relcache.c

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/*-------------------------------------------------------------------------
 *
 * relcache.c
 *    POSTGRES relation descriptor cache code
 *
 * Portions Copyright (c) 1996-2013, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *    src/backend/utils/cache/relcache.c
 *
 *-------------------------------------------------------------------------
 */
/*
 * INTERFACE ROUTINES
 *      RelationCacheInitialize         - initialize relcache (to empty)
 *      RelationCacheInitializePhase2   - initialize shared-catalog entries
 *      RelationCacheInitializePhase3   - finish initializing relcache
 *      RelationIdGetRelation           - get a reldesc by relation id
 *      RelationClose                   - close an open relation
 *
 * NOTES
 *      The following code contains many undocumented hacks.  Please be
 *      careful....
 */
#include "postgres.h"

#include <sys/file.h>
#include <fcntl.h>
#include <unistd.h>

#include "access/htup_details.h"
#include "access/multixact.h"
#include "access/reloptions.h"
#include "access/sysattr.h"
#include "access/transam.h"
#include "access/xact.h"
#include "catalog/catalog.h"
#include "catalog/heap.h"
#include "catalog/index.h"
#include "catalog/indexing.h"
#include "catalog/namespace.h"
#include "catalog/pg_amproc.h"
#include "catalog/pg_attrdef.h"
#include "catalog/pg_authid.h"
#include "catalog/pg_auth_members.h"
#include "catalog/pg_constraint.h"
#include "catalog/pg_database.h"
#include "catalog/pg_namespace.h"
#include "catalog/pg_opclass.h"
#include "catalog/pg_proc.h"
#include "catalog/pg_rewrite.h"
#include "catalog/pg_tablespace.h"
#include "catalog/pg_trigger.h"
#include "catalog/pg_type.h"
#include "catalog/schemapg.h"
#include "catalog/storage.h"
#include "commands/trigger.h"
#include "common/relpath.h"
#include "miscadmin.h"
#include "optimizer/clauses.h"
#include "optimizer/planmain.h"
#include "optimizer/prep.h"
#include "optimizer/var.h"
#include "rewrite/rewriteDefine.h"
#include "storage/lmgr.h"
#include "storage/smgr.h"
#include "utils/array.h"
#include "utils/builtins.h"
#include "utils/fmgroids.h"
#include "utils/inval.h"
#include "utils/lsyscache.h"
#include "utils/memutils.h"
#include "utils/relmapper.h"
#include "utils/resowner_private.h"
#include "utils/syscache.h"
#include "utils/tqual.h"


/*
 *      name of relcache init file(s), used to speed up backend startup
 */
#define RELCACHE_INIT_FILENAME  "pg_internal.init"

#define RELCACHE_INIT_FILEMAGIC     0x573266    /* version ID value */

/*
 *      hardcoded tuple descriptors, contents generated by genbki.pl
 */
static const FormData_pg_attribute Desc_pg_class[Natts_pg_class] = {Schema_pg_class};
static const FormData_pg_attribute Desc_pg_attribute[Natts_pg_attribute] = {Schema_pg_attribute};
static const FormData_pg_attribute Desc_pg_proc[Natts_pg_proc] = {Schema_pg_proc};
static const FormData_pg_attribute Desc_pg_type[Natts_pg_type] = {Schema_pg_type};
static const FormData_pg_attribute Desc_pg_database[Natts_pg_database] = {Schema_pg_database};
static const FormData_pg_attribute Desc_pg_authid[Natts_pg_authid] = {Schema_pg_authid};
static const FormData_pg_attribute Desc_pg_auth_members[Natts_pg_auth_members] = {Schema_pg_auth_members};
static const FormData_pg_attribute Desc_pg_index[Natts_pg_index] = {Schema_pg_index};

/*
 *      Hash tables that index the relation cache
 *
 *      We used to index the cache by both name and OID, but now there
 *      is only an index by OID.
 */
typedef struct relidcacheent
{
    Oid         reloid;
    Relation    reldesc;
} RelIdCacheEnt;

static HTAB *RelationIdCache;

/*
 * This flag is false until we have prepared the critical relcache entries
 * that are needed to do indexscans on the tables read by relcache building.
 */
bool        criticalRelcachesBuilt = false;

/*
 * This flag is false until we have prepared the critical relcache entries
 * for shared catalogs (which are the tables needed for login).
 */
bool        criticalSharedRelcachesBuilt = false;

/*
 * This counter counts relcache inval events received since backend startup
 * (but only for rels that are actually in cache).  Presently, we use it only
 * to detect whether data about to be written by write_relcache_init_file()
 * might already be obsolete.
 */
static long relcacheInvalsReceived = 0L;

/*
 * This list remembers the OIDs of the non-shared relations cached in the
 * database's local relcache init file.  Note that there is no corresponding
 * list for the shared relcache init file, for reasons explained in the
 * comments for RelationCacheInitFileRemove.
 */
static List *initFileRelationIds = NIL;

/*
 * eoxact_list[] stores the OIDs of relations that (might) need AtEOXact
 * cleanup work.  This list intentionally has limited size; if it overflows,
 * we fall back to scanning the whole hashtable.  There is no value in a very
 * large list because (1) at some point, a hash_seq_search scan is faster than
 * retail lookups, and (2) the value of this is to reduce EOXact work for
 * short transactions, which can't have dirtied all that many tables anyway.
 * EOXactListAdd() does not bother to prevent duplicate list entries, so the
 * cleanup processing must be idempotent.
 */
#define MAX_EOXACT_LIST 32
static Oid  eoxact_list[MAX_EOXACT_LIST];
static int  eoxact_list_len = 0;
static bool eoxact_list_overflowed = false;

#define EOXactListAdd(rel) \
    do { \
        if (eoxact_list_len < MAX_EOXACT_LIST) \
            eoxact_list[eoxact_list_len++] = (rel)->rd_id; \
        else \
            eoxact_list_overflowed = true; \
    } while (0)


/*
 *      macros to manipulate the lookup hashtables
 */
#define RelationCacheInsert(RELATION)   \
do { \
    RelIdCacheEnt *idhentry; bool found; \
    idhentry = (RelIdCacheEnt*)hash_search(RelationIdCache, \
                                           (void *) &(RELATION->rd_id), \
                                           HASH_ENTER, &found); \
    /* used to give notice if found -- now just keep quiet */ \
    idhentry->reldesc = RELATION; \
} while(0)

#define RelationIdCacheLookup(ID, RELATION) \
do { \
    RelIdCacheEnt *hentry; \
    hentry = (RelIdCacheEnt*)hash_search(RelationIdCache, \
                                         (void *) &(ID), \
                                         HASH_FIND, NULL); \
    if (hentry) \
        RELATION = hentry->reldesc; \
    else \
        RELATION = NULL; \
} while(0)

#define RelationCacheDelete(RELATION) \
do { \
    RelIdCacheEnt *idhentry; \
    idhentry = (RelIdCacheEnt*)hash_search(RelationIdCache, \
                                           (void *) &(RELATION->rd_id), \
                                           HASH_REMOVE, NULL); \
    if (idhentry == NULL) \
        elog(WARNING, "trying to delete a rd_id reldesc that does not exist"); \
} while(0)


/*
 * Special cache for opclass-related information
 *
 * Note: only default support procs get cached, ie, those with
 * lefttype = righttype = opcintype.
 */
typedef struct opclasscacheent
{
    Oid         opclassoid;     /* lookup key: OID of opclass */
    bool        valid;          /* set TRUE after successful fill-in */
    StrategyNumber numSupport;  /* max # of support procs (from pg_am) */
    Oid         opcfamily;      /* OID of opclass's family */
    Oid         opcintype;      /* OID of opclass's declared input type */
    RegProcedure *supportProcs; /* OIDs of support procedures */
} OpClassCacheEnt;

static HTAB *OpClassCache = NULL;


/* non-export function prototypes */

static void RelationDestroyRelation(Relation relation);
static void RelationClearRelation(Relation relation, bool rebuild);

static void RelationReloadIndexInfo(Relation relation);
static void RelationFlushRelation(Relation relation);
static void AtEOXact_cleanup(Relation relation, bool isCommit);
static void AtEOSubXact_cleanup(Relation relation, bool isCommit,
                    SubTransactionId mySubid, SubTransactionId parentSubid);
static bool load_relcache_init_file(bool shared);
static void write_relcache_init_file(bool shared);
static void write_item(const void *data, Size len, FILE *fp);

static void formrdesc(const char *relationName, Oid relationReltype,
          bool isshared, bool hasoids,
          int natts, const FormData_pg_attribute *attrs);

static HeapTuple ScanPgRelation(Oid targetRelId, bool indexOK);
static Relation AllocateRelationDesc(Form_pg_class relp);
static void RelationParseRelOptions(Relation relation, HeapTuple tuple);
static void RelationBuildTupleDesc(Relation relation);
static Relation RelationBuildDesc(Oid targetRelId, bool insertIt);
static void RelationInitPhysicalAddr(Relation relation);
static void load_critical_index(Oid indexoid, Oid heapoid);
static TupleDesc GetPgClassDescriptor(void);
static TupleDesc GetPgIndexDescriptor(void);
static void AttrDefaultFetch(Relation relation);
static void CheckConstraintFetch(Relation relation);
static List *insert_ordered_oid(List *list, Oid datum);
static void IndexSupportInitialize(oidvector *indclass,
                       RegProcedure *indexSupport,
                       Oid *opFamily,
                       Oid *opcInType,
                       StrategyNumber maxSupportNumber,
                       AttrNumber maxAttributeNumber);
static OpClassCacheEnt *LookupOpclassInfo(Oid operatorClassOid,
                  StrategyNumber numSupport);
static void RelationCacheInitFileRemoveInDir(const char *tblspcpath);
static void unlink_initfile(const char *initfilename);


/*
 *      ScanPgRelation
 *
 *      This is used by RelationBuildDesc to find a pg_class
 *      tuple matching targetRelId.  The caller must hold at least
 *      AccessShareLock on the target relid to prevent concurrent-update
 *      scenarios --- else our SnapshotNow scan might fail to find any
 *      version that it thinks is live.
 *
 *      NB: the returned tuple has been copied into palloc'd storage
 *      and must eventually be freed with heap_freetuple.
 */
static HeapTuple
ScanPgRelation(Oid targetRelId, bool indexOK)
{
    HeapTuple   pg_class_tuple;
    Relation    pg_class_desc;
    SysScanDesc pg_class_scan;
    ScanKeyData key[1];

    /*
     * If something goes wrong during backend startup, we might find ourselves
     * trying to read pg_class before we've selected a database.  That ain't
     * gonna work, so bail out with a useful error message.  If this happens,
     * it probably means a relcache entry that needs to be nailed isn't.
     */
    if (!OidIsValid(MyDatabaseId))
        elog(FATAL, "cannot read pg_class without having selected a database");

    /*
     * form a scan key
     */
    ScanKeyInit(&key[0],
                ObjectIdAttributeNumber,
                BTEqualStrategyNumber, F_OIDEQ,
                ObjectIdGetDatum(targetRelId));

    /*
     * Open pg_class and fetch a tuple.  Force heap scan if we haven't yet
     * built the critical relcache entries (this includes initdb and startup
     * without a pg_internal.init file).  The caller can also force a heap
     * scan by setting indexOK == false.
     */
    pg_class_desc = heap_open(RelationRelationId, AccessShareLock);
    pg_class_scan = systable_beginscan(pg_class_desc, ClassOidIndexId,
                                       indexOK && criticalRelcachesBuilt,
                                       SnapshotNow,
                                       1, key);

    pg_class_tuple = systable_getnext(pg_class_scan);

    /*
     * Must copy tuple before releasing buffer.
     */
    if (HeapTupleIsValid(pg_class_tuple))
        pg_class_tuple = heap_copytuple(pg_class_tuple);

    /* all done */
    systable_endscan(pg_class_scan);
    heap_close(pg_class_desc, AccessShareLock);

    return pg_class_tuple;
}

/*
 *      AllocateRelationDesc
 *
 *      This is used to allocate memory for a new relation descriptor
 *      and initialize the rd_rel field from the given pg_class tuple.
 */
static Relation
AllocateRelationDesc(Form_pg_class relp)
{
    Relation    relation;
    MemoryContext oldcxt;
    Form_pg_class relationForm;

    /* Relcache entries must live in CacheMemoryContext */
    oldcxt = MemoryContextSwitchTo(CacheMemoryContext);

    /*
     * allocate and zero space for new relation descriptor
     */
    relation = (Relation) palloc0(sizeof(RelationData));

    /* make sure relation is marked as having no open file yet */
    relation->rd_smgr = NULL;

    /*
     * Copy the relation tuple form
     *
     * We only allocate space for the fixed fields, ie, CLASS_TUPLE_SIZE. The
     * variable-length fields (relacl, reloptions) are NOT stored in the
     * relcache --- there'd be little point in it, since we don't copy the
     * tuple's nulls bitmap and hence wouldn't know if the values are valid.
     * Bottom line is that relacl *cannot* be retrieved from the relcache. Get
     * it from the syscache if you need it.  The same goes for the original
     * form of reloptions (however, we do store the parsed form of reloptions
     * in rd_options).
     */
    relationForm = (Form_pg_class) palloc(CLASS_TUPLE_SIZE);

    memcpy(relationForm, relp, CLASS_TUPLE_SIZE);

    /* initialize relation tuple form */
    relation->rd_rel = relationForm;

    /* and allocate attribute tuple form storage */
    relation->rd_att = CreateTemplateTupleDesc(relationForm->relnatts,
                                               relationForm->relhasoids);
    /* which we mark as a reference-counted tupdesc */
    relation->rd_att->tdrefcount = 1;

    MemoryContextSwitchTo(oldcxt);

    return relation;
}

/*
 * RelationParseRelOptions
 *      Convert pg_class.reloptions into pre-parsed rd_options
 *
 * tuple is the real pg_class tuple (not rd_rel!) for relation
 *
 * Note: rd_rel and (if an index) rd_am must be valid already
 */
static void
RelationParseRelOptions(Relation relation, HeapTuple tuple)
{
    bytea      *options;

    relation->rd_options = NULL;

    /* Fall out if relkind should not have options */
    switch (relation->rd_rel->relkind)
    {
        case RELKIND_RELATION:
        case RELKIND_TOASTVALUE:
        case RELKIND_INDEX:
        case RELKIND_VIEW:
        case RELKIND_MATVIEW:
            break;
        default:
            return;
    }

    /*
     * Fetch reloptions from tuple; have to use a hardwired descriptor because
     * we might not have any other for pg_class yet (consider executing this
     * code for pg_class itself)
     */
    options = extractRelOptions(tuple,
                                GetPgClassDescriptor(),
                                relation->rd_rel->relkind == RELKIND_INDEX ?
                                relation->rd_am->amoptions : InvalidOid);

    /*
     * Copy parsed data into CacheMemoryContext.  To guard against the
     * possibility of leaks in the reloptions code, we want to do the actual
     * parsing in the caller's memory context and copy the results into
     * CacheMemoryContext after the fact.
     */
    if (options)
    {
        relation->rd_options = MemoryContextAlloc(CacheMemoryContext,
                                                  VARSIZE(options));
        memcpy(relation->rd_options, options, VARSIZE(options));
        pfree(options);
    }
}

/*
 *      RelationBuildTupleDesc
 *
 *      Form the relation's tuple descriptor from information in
 *      the pg_attribute, pg_attrdef & pg_constraint system catalogs.
 */
static void
RelationBuildTupleDesc(Relation relation)
{
    HeapTuple   pg_attribute_tuple;
    Relation    pg_attribute_desc;
    SysScanDesc pg_attribute_scan;
    ScanKeyData skey[2];
    int         need;
    TupleConstr *constr;
    AttrDefault *attrdef = NULL;
    int         ndef = 0;

    /* copy some fields from pg_class row to rd_att */
    relation->rd_att->tdtypeid = relation->rd_rel->reltype;
    relation->rd_att->tdtypmod = -1;    /* unnecessary, but... */
    relation->rd_att->tdhasoid = relation->rd_rel->relhasoids;

    constr = (TupleConstr *) MemoryContextAlloc(CacheMemoryContext,
                                                sizeof(TupleConstr));
    constr->has_not_null = false;

    /*
     * Form a scan key that selects only user attributes (attnum > 0).
     * (Eliminating system attribute rows at the index level is lots faster
     * than fetching them.)
     */
    ScanKeyInit(&skey[0],
                Anum_pg_attribute_attrelid,
                BTEqualStrategyNumber, F_OIDEQ,
                ObjectIdGetDatum(RelationGetRelid(relation)));
    ScanKeyInit(&skey[1],
                Anum_pg_attribute_attnum,
                BTGreaterStrategyNumber, F_INT2GT,
                Int16GetDatum(0));

    /*
     * Open pg_attribute and begin a scan.  Force heap scan if we haven't yet
     * built the critical relcache entries (this includes initdb and startup
     * without a pg_internal.init file).
     */
    pg_attribute_desc = heap_open(AttributeRelationId, AccessShareLock);
    pg_attribute_scan = systable_beginscan(pg_attribute_desc,
                                           AttributeRelidNumIndexId,
                                           criticalRelcachesBuilt,
                                           SnapshotNow,
                                           2, skey);

    /*
     * add attribute data to relation->rd_att
     */
    need = relation->rd_rel->relnatts;

    while (HeapTupleIsValid(pg_attribute_tuple = systable_getnext(pg_attribute_scan)))
    {
        Form_pg_attribute attp;

        attp = (Form_pg_attribute) GETSTRUCT(pg_attribute_tuple);

        if (attp->attnum <= 0 ||
            attp->attnum > relation->rd_rel->relnatts)
            elog(ERROR, "invalid attribute number %d for %s",
                 attp->attnum, RelationGetRelationName(relation));

        memcpy(relation->rd_att->attrs[attp->attnum - 1],
               attp,
               ATTRIBUTE_FIXED_PART_SIZE);

        /* Update constraint/default info */
        if (attp->attnotnull)
            constr->has_not_null = true;

        if (attp->atthasdef)
        {
            if (attrdef == NULL)
                attrdef = (AttrDefault *)
                    MemoryContextAllocZero(CacheMemoryContext,
                                           relation->rd_rel->relnatts *
                                           sizeof(AttrDefault));
            attrdef[ndef].adnum = attp->attnum;
            attrdef[ndef].adbin = NULL;
            ndef++;
        }
        need--;
        if (need == 0)
            break;
    }

    /*
     * end the scan and close the attribute relation
     */
    systable_endscan(pg_attribute_scan);
    heap_close(pg_attribute_desc, AccessShareLock);

    if (need != 0)
        elog(ERROR, "catalog is missing %d attribute(s) for relid %u",
             need, RelationGetRelid(relation));

    /*
     * The attcacheoff values we read from pg_attribute should all be -1
     * ("unknown").  Verify this if assert checking is on.  They will be
     * computed when and if needed during tuple access.
     */
#ifdef USE_ASSERT_CHECKING
    {
        int         i;

        for (i = 0; i < relation->rd_rel->relnatts; i++)
            Assert(relation->rd_att->attrs[i]->attcacheoff == -1);
    }
#endif

    /*
     * However, we can easily set the attcacheoff value for the first
     * attribute: it must be zero.  This eliminates the need for special cases
     * for attnum=1 that used to exist in fastgetattr() and index_getattr().
     */
    if (relation->rd_rel->relnatts > 0)
        relation->rd_att->attrs[0]->attcacheoff = 0;

    /*
     * Set up constraint/default info
     */
    if (constr->has_not_null || ndef > 0 || relation->rd_rel->relchecks)
    {
        relation->rd_att->constr = constr;

        if (ndef > 0)           /* DEFAULTs */
        {
            if (ndef < relation->rd_rel->relnatts)
                constr->defval = (AttrDefault *)
                    repalloc(attrdef, ndef * sizeof(AttrDefault));
            else
                constr->defval = attrdef;
            constr->num_defval = ndef;
            AttrDefaultFetch(relation);
        }
        else
            constr->num_defval = 0;

        if (relation->rd_rel->relchecks > 0)    /* CHECKs */
        {
            constr->num_check = relation->rd_rel->relchecks;
            constr->check = (ConstrCheck *)
                MemoryContextAllocZero(CacheMemoryContext,
                                    constr->num_check * sizeof(ConstrCheck));
            CheckConstraintFetch(relation);
        }
        else
            constr->num_check = 0;
    }
    else
    {
        pfree(constr);
        relation->rd_att->constr = NULL;
    }
}

/*
 *      RelationBuildRuleLock
 *
 *      Form the relation's rewrite rules from information in
 *      the pg_rewrite system catalog.
 *
 * Note: The rule parsetrees are potentially very complex node structures.
 * To allow these trees to be freed when the relcache entry is flushed,
 * we make a private memory context to hold the RuleLock information for
 * each relcache entry that has associated rules.  The context is used
 * just for rule info, not for any other subsidiary data of the relcache
 * entry, because that keeps the update logic in RelationClearRelation()
 * manageable.  The other subsidiary data structures are simple enough
 * to be easy to free explicitly, anyway.
 */
static void
RelationBuildRuleLock(Relation relation)
{
    MemoryContext rulescxt;
    MemoryContext oldcxt;
    HeapTuple   rewrite_tuple;
    Relation    rewrite_desc;
    TupleDesc   rewrite_tupdesc;
    SysScanDesc rewrite_scan;
    ScanKeyData key;
    RuleLock   *rulelock;
    int         numlocks;
    RewriteRule **rules;
    int         maxlocks;

    /*
     * Make the private context.  Parameters are set on the assumption that
     * it'll probably not contain much data.
     */
    rulescxt = AllocSetContextCreate(CacheMemoryContext,
                                     RelationGetRelationName(relation),
                                     ALLOCSET_SMALL_MINSIZE,
                                     ALLOCSET_SMALL_INITSIZE,
                                     ALLOCSET_SMALL_MAXSIZE);
    relation->rd_rulescxt = rulescxt;

    /*
     * allocate an array to hold the rewrite rules (the array is extended if
     * necessary)
     */
    maxlocks = 4;
    rules = (RewriteRule **)
        MemoryContextAlloc(rulescxt, sizeof(RewriteRule *) * maxlocks);
    numlocks = 0;

    /*
     * form a scan key
     */
    ScanKeyInit(&key,
                Anum_pg_rewrite_ev_class,
                BTEqualStrategyNumber, F_OIDEQ,
                ObjectIdGetDatum(RelationGetRelid(relation)));

    /*
     * open pg_rewrite and begin a scan
     *
     * Note: since we scan the rules using RewriteRelRulenameIndexId, we will
     * be reading the rules in name order, except possibly during
     * emergency-recovery operations (ie, IgnoreSystemIndexes). This in turn
     * ensures that rules will be fired in name order.
     */
    rewrite_desc = heap_open(RewriteRelationId, AccessShareLock);
    rewrite_tupdesc = RelationGetDescr(rewrite_desc);
    rewrite_scan = systable_beginscan(rewrite_desc,
                                      RewriteRelRulenameIndexId,
                                      true, SnapshotNow,
                                      1, &key);

    while (HeapTupleIsValid(rewrite_tuple = systable_getnext(rewrite_scan)))
    {
        Form_pg_rewrite rewrite_form = (Form_pg_rewrite) GETSTRUCT(rewrite_tuple);
        bool        isnull;
        Datum       rule_datum;
        char       *rule_str;
        RewriteRule *rule;

        rule = (RewriteRule *) MemoryContextAlloc(rulescxt,
                                                  sizeof(RewriteRule));

        rule->ruleId = HeapTupleGetOid(rewrite_tuple);

        rule->event = rewrite_form->ev_type - '0';
        rule->attrno = rewrite_form->ev_attr;
        rule->enabled = rewrite_form->ev_enabled;
        rule->isInstead = rewrite_form->is_instead;

        /*
         * Must use heap_getattr to fetch ev_action and ev_qual.  Also, the
         * rule strings are often large enough to be toasted.  To avoid
         * leaking memory in the caller's context, do the detoasting here so
         * we can free the detoasted version.
         */
        rule_datum = heap_getattr(rewrite_tuple,
                                  Anum_pg_rewrite_ev_action,
                                  rewrite_tupdesc,
                                  &isnull);
        Assert(!isnull);
        rule_str = TextDatumGetCString(rule_datum);
        oldcxt = MemoryContextSwitchTo(rulescxt);
        rule->actions = (List *) stringToNode(rule_str);
        MemoryContextSwitchTo(oldcxt);
        pfree(rule_str);

        rule_datum = heap_getattr(rewrite_tuple,
                                  Anum_pg_rewrite_ev_qual,
                                  rewrite_tupdesc,
                                  &isnull);
        Assert(!isnull);
        rule_str = TextDatumGetCString(rule_datum);
        oldcxt = MemoryContextSwitchTo(rulescxt);
        rule->qual = (Node *) stringToNode(rule_str);
        MemoryContextSwitchTo(oldcxt);
        pfree(rule_str);

        /*
         * We want the rule's table references to be checked as though by the
         * table owner, not the user referencing the rule.  Therefore, scan
         * through the rule's actions and set the checkAsUser field on all
         * rtable entries.  We have to look at the qual as well, in case it
         * contains sublinks.
         *
         * The reason for doing this when the rule is loaded, rather than when
         * it is stored, is that otherwise ALTER TABLE OWNER would have to
         * grovel through stored rules to update checkAsUser fields. Scanning
         * the rule tree during load is relatively cheap (compared to
         * constructing it in the first place), so we do it here.
         */
        setRuleCheckAsUser((Node *) rule->actions, relation->rd_rel->relowner);
        setRuleCheckAsUser(rule->qual, relation->rd_rel->relowner);

        if (numlocks >= maxlocks)
        {
            maxlocks *= 2;
            rules = (RewriteRule **)
                repalloc(rules, sizeof(RewriteRule *) * maxlocks);
        }
        rules[numlocks++] = rule;
    }

    /*
     * end the scan and close the attribute relation
     */
    systable_endscan(rewrite_scan);
    heap_close(rewrite_desc, AccessShareLock);

    /*
     * there might not be any rules (if relhasrules is out-of-date)
     */
    if (numlocks == 0)
    {
        relation->rd_rules = NULL;
        relation->rd_rulescxt = NULL;
        MemoryContextDelete(rulescxt);
        return;
    }

    /*
     * form a RuleLock and insert into relation
     */
    rulelock = (RuleLock *) MemoryContextAlloc(rulescxt, sizeof(RuleLock));
    rulelock->numLocks = numlocks;
    rulelock->rules = rules;

    relation->rd_rules = rulelock;
}

/*
 *      equalRuleLocks
 *
 *      Determine whether two RuleLocks are equivalent
 *
 *      Probably this should be in the rules code someplace...
 */
static bool
equalRuleLocks(RuleLock *rlock1, RuleLock *rlock2)
{
    int         i;

    /*
     * As of 7.3 we assume the rule ordering is repeatable, because
     * RelationBuildRuleLock should read 'em in a consistent order.  So just
     * compare corresponding slots.
     */
    if (rlock1 != NULL)
    {
        if (rlock2 == NULL)
            return false;
        if (rlock1->numLocks != rlock2->numLocks)
            return false;
        for (i = 0; i < rlock1->numLocks; i++)
        {
            RewriteRule *rule1 = rlock1->rules[i];
            RewriteRule *rule2 = rlock2->rules[i];

            if (rule1->ruleId != rule2->ruleId)
                return false;
            if (rule1->event != rule2->event)
                return false;
            if (rule1->attrno != rule2->attrno)
                return false;
            if (rule1->enabled != rule2->enabled)
                return false;
            if (rule1->isInstead != rule2->isInstead)
                return false;
            if (!equal(rule1->qual, rule2->qual))
                return false;
            if (!equal(rule1->actions, rule2->actions))
                return false;
        }
    }
    else if (rlock2 != NULL)
        return false;
    return true;
}


/*
 *      RelationBuildDesc
 *
 *      Build a relation descriptor.  The caller must hold at least
 *      AccessShareLock on the target relid.
 *
 *      The new descriptor is inserted into the hash table if insertIt is true.
 *
 *      Returns NULL if no pg_class row could be found for the given relid
 *      (suggesting we are trying to access a just-deleted relation).
 *      Any other error is reported via elog.
 */
static Relation
RelationBuildDesc(Oid targetRelId, bool insertIt)
{
    Relation    relation;
    Oid         relid;
    HeapTuple   pg_class_tuple;
    Form_pg_class relp;

    /*
     * find the tuple in pg_class corresponding to the given relation id
     */
    pg_class_tuple = ScanPgRelation(targetRelId, true);

    /*
     * if no such tuple exists, return NULL
     */
    if (!HeapTupleIsValid(pg_class_tuple))
        return NULL;

    /*
     * get information from the pg_class_tuple
     */
    relid = HeapTupleGetOid(pg_class_tuple);
    relp = (Form_pg_class) GETSTRUCT(pg_class_tuple);
    Assert(relid == targetRelId);

    /*
     * allocate storage for the relation descriptor, and copy pg_class_tuple
     * to relation->rd_rel.
     */
    relation = AllocateRelationDesc(relp);

    /*
     * initialize the relation's relation id (relation->rd_id)
     */
    RelationGetRelid(relation) = relid;

    /*
     * normal relations are not nailed into the cache; nor can a pre-existing
     * relation be new.  It could be temp though.  (Actually, it could be new
     * too, but it's okay to forget that fact if forced to flush the entry.)
     */
    relation->rd_refcnt = 0;
    relation->rd_isnailed = false;
    relation->rd_createSubid = InvalidSubTransactionId;
    relation->rd_newRelfilenodeSubid = InvalidSubTransactionId;
    switch (relation->rd_rel->relpersistence)
    {
        case RELPERSISTENCE_UNLOGGED:
        case RELPERSISTENCE_PERMANENT:
            relation->rd_backend = InvalidBackendId;
            relation->rd_islocaltemp = false;
            break;
        case RELPERSISTENCE_TEMP:
            if (isTempOrToastNamespace(relation->rd_rel->relnamespace))
            {
                relation->rd_backend = MyBackendId;
                relation->rd_islocaltemp = true;
            }
            else
            {
                /*
                 * If it's a temp table, but not one of ours, we have to use
                 * the slow, grotty method to figure out the owning backend.
                 *
                 * Note: it's possible that rd_backend gets set to MyBackendId
                 * here, in case we are looking at a pg_class entry left over
                 * from a crashed backend that coincidentally had the same
                 * BackendId we're using.  We should *not* consider such a
                 * table to be "ours"; this is why we need the separate
                 * rd_islocaltemp flag.  The pg_class entry will get flushed
                 * if/when we clean out the corresponding temp table namespace
                 * in preparation for using it.
                 */
                relation->rd_backend =
                    GetTempNamespaceBackendId(relation->rd_rel->relnamespace);
                Assert(relation->rd_backend != InvalidBackendId);
                relation->rd_islocaltemp = false;
            }
            break;
        default:
            elog(ERROR, "invalid relpersistence: %c",
                 relation->rd_rel->relpersistence);
            break;
    }

    /*
     * initialize the tuple descriptor (relation->rd_att).
     */
    RelationBuildTupleDesc(relation);

    /*
     * Fetch rules and triggers that affect this relation
     */
    if (relation->rd_rel->relhasrules)
        RelationBuildRuleLock(relation);
    else
    {
        relation->rd_rules = NULL;
        relation->rd_rulescxt = NULL;
    }

    if (relation->rd_rel->relhastriggers)
        RelationBuildTriggers(relation);
    else
        relation->trigdesc = NULL;

    /*
     * if it's an index, initialize index-related information
     */
    if (OidIsValid(relation->rd_rel->relam))
        RelationInitIndexAccessInfo(relation);

    /* extract reloptions if any */
    RelationParseRelOptions(relation, pg_class_tuple);

    /*
     * initialize the relation lock manager information
     */
    RelationInitLockInfo(relation);     /* see lmgr.c */

    /*
     * initialize physical addressing information for the relation
     */
    RelationInitPhysicalAddr(relation);

    /* make sure relation is marked as having no open file yet */
    relation->rd_smgr = NULL;

    if (relation->rd_rel->relkind == RELKIND_MATVIEW &&
        heap_is_matview_init_state(relation))
        relation->rd_ispopulated = false;
    else
        relation->rd_ispopulated = true;

    /*
     * now we can free the memory allocated for pg_class_tuple
     */
    heap_freetuple(pg_class_tuple);

    /*
     * Insert newly created relation into relcache hash table, if requested.
     */
    if (insertIt)
        RelationCacheInsert(relation);

    /* It's fully valid */
    relation->rd_isvalid = true;

    return relation;
}

/*
 * Initialize the physical addressing info (RelFileNode) for a relcache entry
 *
 * Note: at the physical level, relations in the pg_global tablespace must
 * be treated as shared, even if relisshared isn't set.  Hence we do not
 * look at relisshared here.
 */
static void
RelationInitPhysicalAddr(Relation relation)
{
    if (relation->rd_rel->reltablespace)
        relation->rd_node.spcNode = relation->rd_rel->reltablespace;
    else
        relation->rd_node.spcNode = MyDatabaseTableSpace;
    if (relation->rd_node.spcNode == GLOBALTABLESPACE_OID)
        relation->rd_node.dbNode = InvalidOid;
    else
        relation->rd_node.dbNode = MyDatabaseId;
    if (relation->rd_rel->relfilenode)
        relation->rd_node.relNode = relation->rd_rel->relfilenode;
    else
    {
        /* Consult the relation mapper */
        relation->rd_node.relNode =
            RelationMapOidToFilenode(relation->rd_id,
                                     relation->rd_rel->relisshared);
        if (!OidIsValid(relation->rd_node.relNode))
            elog(ERROR, "could not find relation mapping for relation \"%s\", OID %u",
                 RelationGetRelationName(relation), relation->rd_id);
    }
}

/*
 * Initialize index-access-method support data for an index relation
 */
void
RelationInitIndexAccessInfo(Relation relation)
{
    HeapTuple   tuple;
    Form_pg_am  aform;
    Datum       indcollDatum;
    Datum       indclassDatum;
    Datum       indoptionDatum;
    bool        isnull;
    oidvector  *indcoll;
    oidvector  *indclass;
    int2vector *indoption;
    MemoryContext indexcxt;
    MemoryContext oldcontext;
    int         natts;
    uint16      amsupport;

    /*
     * Make a copy of the pg_index entry for the index.  Since pg_index
     * contains variable-length and possibly-null fields, we have to do this
     * honestly rather than just treating it as a Form_pg_index struct.
     */
    tuple = SearchSysCache1(INDEXRELID,
                            ObjectIdGetDatum(RelationGetRelid(relation)));
    if (!HeapTupleIsValid(tuple))
        elog(ERROR, "cache lookup failed for index %u",
             RelationGetRelid(relation));
    oldcontext = MemoryContextSwitchTo(CacheMemoryContext);
    relation->rd_indextuple = heap_copytuple(tuple);
    relation->rd_index = (Form_pg_index) GETSTRUCT(relation->rd_indextuple);
    MemoryContextSwitchTo(oldcontext);
    ReleaseSysCache(tuple);

    /*
     * Make a copy of the pg_am entry for the index's access method
     */
    tuple = SearchSysCache1(AMOID, ObjectIdGetDatum(relation->rd_rel->relam));
    if (!HeapTupleIsValid(tuple))
        elog(ERROR, "cache lookup failed for access method %u",
             relation->rd_rel->relam);
    aform = (Form_pg_am) MemoryContextAlloc(CacheMemoryContext, sizeof *aform);
    memcpy(aform, GETSTRUCT(tuple), sizeof *aform);
    ReleaseSysCache(tuple);
    relation->rd_am = aform;

    natts = relation->rd_rel->relnatts;
    if (natts != relation->rd_index->indnatts)
        elog(ERROR, "relnatts disagrees with indnatts for index %u",
             RelationGetRelid(relation));
    amsupport = aform->amsupport;

    /*
     * Make the private context to hold index access info.  The reason we need
     * a context, and not just a couple of pallocs, is so that we won't leak
     * any subsidiary info attached to fmgr lookup records.
     *
     * Context parameters are set on the assumption that it'll probably not
     * contain much data.
     */
    indexcxt = AllocSetContextCreate(CacheMemoryContext,
                                     RelationGetRelationName(relation),
                                     ALLOCSET_SMALL_MINSIZE,
                                     ALLOCSET_SMALL_INITSIZE,
                                     ALLOCSET_SMALL_MAXSIZE);
    relation->rd_indexcxt = indexcxt;

    /*
     * Allocate arrays to hold data
     */
    relation->rd_aminfo = (RelationAmInfo *)
        MemoryContextAllocZero(indexcxt, sizeof(RelationAmInfo));

    relation->rd_opfamily = (Oid *)
        MemoryContextAllocZero(indexcxt, natts * sizeof(Oid));
    relation->rd_opcintype = (Oid *)
        MemoryContextAllocZero(indexcxt, natts * sizeof(Oid));

    if (amsupport > 0)
    {
        int         nsupport = natts * amsupport;

        relation->rd_support = (RegProcedure *)
            MemoryContextAllocZero(indexcxt, nsupport * sizeof(RegProcedure));
        relation->rd_supportinfo = (FmgrInfo *)
            MemoryContextAllocZero(indexcxt, nsupport * sizeof(FmgrInfo));
    }
    else
    {
        relation->rd_support = NULL;
        relation->rd_supportinfo = NULL;
    }

    relation->rd_indcollation = (Oid *)
        MemoryContextAllocZero(indexcxt, natts * sizeof(Oid));

    relation->rd_indoption = (int16 *)
        MemoryContextAllocZero(indexcxt, natts * sizeof(int16));

    /*
     * indcollation cannot be referenced directly through the C struct,
     * because it comes after the variable-width indkey field.  Must extract
     * the datum the hard way...
     */
    indcollDatum = fastgetattr(relation->rd_indextuple,
                               Anum_pg_index_indcollation,
                               GetPgIndexDescriptor(),
                               &isnull);
    Assert(!isnull);
    indcoll = (oidvector *) DatumGetPointer(indcollDatum);
    memcpy(relation->rd_indcollation, indcoll->values, natts * sizeof(Oid));

    /*
     * indclass cannot be referenced directly through the C struct, because it
     * comes after the variable-width indkey field.  Must extract the datum
     * the hard way...
     */
    indclassDatum = fastgetattr(relation->rd_indextuple,
                                Anum_pg_index_indclass,
                                GetPgIndexDescriptor(),
                                &isnull);
    Assert(!isnull);
    indclass = (oidvector *) DatumGetPointer(indclassDatum);

    /*
     * Fill the support procedure OID array, as well as the info about
     * opfamilies and opclass input types.  (aminfo and supportinfo are left
     * as zeroes, and are filled on-the-fly when used)
     */
    IndexSupportInitialize(indclass, relation->rd_support,
                           relation->rd_opfamily, relation->rd_opcintype,
                           amsupport, natts);

    /*
     * Similarly extract indoption and copy it to the cache entry
     */
    indoptionDatum = fastgetattr(relation->rd_indextuple,
                                 Anum_pg_index_indoption,
                                 GetPgIndexDescriptor(),
                                 &isnull);
    Assert(!isnull);
    indoption = (int2vector *) DatumGetPointer(indoptionDatum);
    memcpy(relation->rd_indoption, indoption->values, natts * sizeof(int16));

    /*
     * expressions, predicate, exclusion caches will be filled later
     */
    relation->rd_indexprs = NIL;
    relation->rd_indpred = NIL;
    relation->rd_exclops = NULL;
    relation->rd_exclprocs = NULL;
    relation->rd_exclstrats = NULL;
    relation->rd_amcache = NULL;
}

/*
 * IndexSupportInitialize
 *      Initializes an index's cached opclass information,
 *      given the index's pg_index.indclass entry.
 *
 * Data is returned into *indexSupport, *opFamily, and *opcInType,
 * which are arrays allocated by the caller.
 *
 * The caller also passes maxSupportNumber and maxAttributeNumber, since these
 * indicate the size of the arrays it has allocated --- but in practice these
 * numbers must always match those obtainable from the system catalog entries
 * for the index and access method.
 */
static void
IndexSupportInitialize(oidvector *indclass,
                       RegProcedure *indexSupport,
                       Oid *opFamily,
                       Oid *opcInType,
                       StrategyNumber maxSupportNumber,
                       AttrNumber maxAttributeNumber)
{
    int         attIndex;

    for (attIndex = 0; attIndex < maxAttributeNumber; attIndex++)
    {
        OpClassCacheEnt *opcentry;

        if (!OidIsValid(indclass->values[attIndex]))
            elog(ERROR, "bogus pg_index tuple");

        /* look up the info for this opclass, using a cache */
        opcentry = LookupOpclassInfo(indclass->values[attIndex],
                                     maxSupportNumber);

        /* copy cached data into relcache entry */
        opFamily[attIndex] = opcentry->opcfamily;
        opcInType[attIndex] = opcentry->opcintype;
        if (maxSupportNumber > 0)
            memcpy(&indexSupport[attIndex * maxSupportNumber],
                   opcentry->supportProcs,
                   maxSupportNumber * sizeof(RegProcedure));
    }
}

/*
 * LookupOpclassInfo
 *
 * This routine maintains a per-opclass cache of the information needed
 * by IndexSupportInitialize().  This is more efficient than relying on
 * the catalog cache, because we can load all the info about a particular
 * opclass in a single indexscan of pg_amproc.
 *
 * The information from pg_am about expected range of support function
 * numbers is passed in, rather than being looked up, mainly because the
 * caller will have it already.
 *
 * Note there is no provision for flushing the cache.  This is OK at the
 * moment because there is no way to ALTER any interesting properties of an
 * existing opclass --- all you can do is drop it, which will result in
 * a useless but harmless dead entry in the cache.  To support altering
 * opclass membership (not the same as opfamily membership!), we'd need to
 * be able to flush this cache as well as the contents of relcache entries
 * for indexes.
 */
static OpClassCacheEnt *
LookupOpclassInfo(Oid operatorClassOid,
                  StrategyNumber numSupport)
{
    OpClassCacheEnt *opcentry;
    bool        found;
    Relation    rel;
    SysScanDesc scan;
    ScanKeyData skey[3];
    HeapTuple   htup;
    bool        indexOK;

    if (OpClassCache == NULL)
    {
        /* First time through: initialize the opclass cache */
        HASHCTL     ctl;

        MemSet(&ctl, 0, sizeof(ctl));
        ctl.keysize = sizeof(Oid);
        ctl.entrysize = sizeof(OpClassCacheEnt);
        ctl.hash = oid_hash;
        OpClassCache = hash_create("Operator class cache", 64,
                                   &ctl, HASH_ELEM | HASH_FUNCTION);

        /* Also make sure CacheMemoryContext exists */
        if (!CacheMemoryContext)
            CreateCacheMemoryContext();
    }

    opcentry = (OpClassCacheEnt *) hash_search(OpClassCache,
                                               (void *) &operatorClassOid,
                                               HASH_ENTER, &found);

    if (!found)
    {
        /* Need to allocate memory for new entry */
        opcentry->valid = false;    /* until known OK */
        opcentry->numSupport = numSupport;

        if (numSupport > 0)
            opcentry->supportProcs = (RegProcedure *)
                MemoryContextAllocZero(CacheMemoryContext,
                                       numSupport * sizeof(RegProcedure));
        else
            opcentry->supportProcs = NULL;
    }
    else
    {
        Assert(numSupport == opcentry->numSupport);
    }

    /*
     * When testing for cache-flush hazards, we intentionally disable the
     * operator class cache and force reloading of the info on each call. This
     * is helpful because we want to test the case where a cache flush occurs
     * while we are loading the info, and it's very hard to provoke that if
     * this happens only once per opclass per backend.
     */
#if defined(CLOBBER_CACHE_ALWAYS)
    opcentry->valid = false;
#endif

    if (opcentry->valid)
        return opcentry;

    /*
     * Need to fill in new entry.
     *
     * To avoid infinite recursion during startup, force heap scans if we're
     * looking up info for the opclasses used by the indexes we would like to
     * reference here.
     */
    indexOK = criticalRelcachesBuilt ||
        (operatorClassOid != OID_BTREE_OPS_OID &&
         operatorClassOid != INT2_BTREE_OPS_OID);

    /*
     * We have to fetch the pg_opclass row to determine its opfamily and
     * opcintype, which are needed to look up related operators and functions.
     * It'd be convenient to use the syscache here, but that probably doesn't
     * work while bootstrapping.
     */
    ScanKeyInit(&skey[0],
                ObjectIdAttributeNumber,
                BTEqualStrategyNumber, F_OIDEQ,
                ObjectIdGetDatum(operatorClassOid));
    rel = heap_open(OperatorClassRelationId, AccessShareLock);
    scan = systable_beginscan(rel, OpclassOidIndexId, indexOK,
                              SnapshotNow, 1, skey);

    if (HeapTupleIsValid(htup = systable_getnext(scan)))
    {
        Form_pg_opclass opclassform = (Form_pg_opclass) GETSTRUCT(htup);

        opcentry->opcfamily = opclassform->opcfamily;
        opcentry->opcintype = opclassform->opcintype;
    }
    else
        elog(ERROR, "could not find tuple for opclass %u", operatorClassOid);

    systable_endscan(scan);
    heap_close(rel, AccessShareLock);

    /*
     * Scan pg_amproc to obtain support procs for the opclass.  We only fetch
     * the default ones (those with lefttype = righttype = opcintype).
     */
    if (numSupport > 0)
    {
        ScanKeyInit(&skey[0],
                    Anum_pg_amproc_amprocfamily,
                    BTEqualStrategyNumber, F_OIDEQ,
                    ObjectIdGetDatum(opcentry->opcfamily));
        ScanKeyInit(&skey[1],
                    Anum_pg_amproc_amproclefttype,
                    BTEqualStrategyNumber, F_OIDEQ,
                    ObjectIdGetDatum(opcentry->opcintype));
        ScanKeyInit(&skey[2],
                    Anum_pg_amproc_amprocrighttype,
                    BTEqualStrategyNumber, F_OIDEQ,
                    ObjectIdGetDatum(opcentry->opcintype));
        rel = heap_open(AccessMethodProcedureRelationId, AccessShareLock);
        scan = systable_beginscan(rel, AccessMethodProcedureIndexId, indexOK,
                                  SnapshotNow, 3, skey);

        while (HeapTupleIsValid(htup = systable_getnext(scan)))
        {
            Form_pg_amproc amprocform = (Form_pg_amproc) GETSTRUCT(htup);

            if (amprocform->amprocnum <= 0 ||
                (StrategyNumber) amprocform->amprocnum > numSupport)
                elog(ERROR, "invalid amproc number %d for opclass %u",
                     amprocform->amprocnum, operatorClassOid);

            opcentry->supportProcs[amprocform->amprocnum - 1] =
                amprocform->amproc;
        }

        systable_endscan(scan);
        heap_close(rel, AccessShareLock);
    }

    opcentry->valid = true;
    return opcentry;
}


/*
 *      formrdesc
 *
 *      This is a special cut-down version of RelationBuildDesc(),
 *      used while initializing the relcache.
 *      The relation descriptor is built just from the supplied parameters,
 *      without actually looking at any system table entries.  We cheat
 *      quite a lot since we only need to work for a few basic system
 *      catalogs.
 *
 * formrdesc is currently used for: pg_database, pg_authid, pg_auth_members,
 * pg_class, pg_attribute, pg_proc, and pg_type
 * (see RelationCacheInitializePhase2/3).
 *
 * Note that these catalogs can't have constraints (except attnotnull),
 * default values, rules, or triggers, since we don't cope with any of that.
 * (Well, actually, this only matters for properties that need to be valid
 * during bootstrap or before RelationCacheInitializePhase3 runs, and none of
 * these properties matter then...)
 *
 * NOTE: we assume we are already switched into CacheMemoryContext.
 */
static void
formrdesc(const char *relationName, Oid relationReltype,
          bool isshared, bool hasoids,
          int natts, const FormData_pg_attribute *attrs)
{
    Relation    relation;
    int         i;
    bool        has_not_null;

    /*
     * allocate new relation desc, clear all fields of reldesc
     */
    relation = (Relation) palloc0(sizeof(RelationData));

    /* make sure relation is marked as having no open file yet */
    relation->rd_smgr = NULL;

    /*
     * initialize reference count: 1 because it is nailed in cache
     */
    relation->rd_refcnt = 1;

    /*
     * all entries built with this routine are nailed-in-cache; none are for
     * new or temp relations.
     */
    relation->rd_isnailed = true;
    relation->rd_createSubid = InvalidSubTransactionId;
    relation->rd_newRelfilenodeSubid = InvalidSubTransactionId;
    relation->rd_backend = InvalidBackendId;
    relation->rd_islocaltemp = false;

    /*
     * initialize relation tuple form
     *
     * The data we insert here is pretty incomplete/bogus, but it'll serve to
     * get us launched.  RelationCacheInitializePhase3() will read the real
     * data from pg_class and replace what we've done here.  Note in
     * particular that relowner is left as zero; this cues
     * RelationCacheInitializePhase3 that the real data isn't there yet.
     */
    relation->rd_rel = (Form_pg_class) palloc0(CLASS_TUPLE_SIZE);

    namestrcpy(&relation->rd_rel->relname, relationName);
    relation->rd_rel->relnamespace = PG_CATALOG_NAMESPACE;
    relation->rd_rel->reltype = relationReltype;

    /*
     * It's important to distinguish between shared and non-shared relations,
     * even at bootstrap time, to make sure we know where they are stored.
     */
    relation->rd_rel->relisshared = isshared;
    if (isshared)
        relation->rd_rel->reltablespace = GLOBALTABLESPACE_OID;

    /* formrdesc is used only for permanent relations */
    relation->rd_rel->relpersistence = RELPERSISTENCE_PERMANENT;

    relation->rd_rel->relpages = 0;
    relation->rd_rel->reltuples = 0;
    relation->rd_rel->relallvisible = 0;
    relation->rd_rel->relkind = RELKIND_RELATION;
    relation->rd_rel->relhasoids = hasoids;
    relation->rd_rel->relnatts = (int16) natts;

    /*
     * initialize attribute tuple form
     *
     * Unlike the case with the relation tuple, this data had better be right
     * because it will never be replaced.  The data comes from
     * src/include/catalog/ headers via genbki.pl.
     */
    relation->rd_att = CreateTemplateTupleDesc(natts, hasoids);
    relation->rd_att->tdrefcount = 1;   /* mark as refcounted */

    relation->rd_att->tdtypeid = relationReltype;
    relation->rd_att->tdtypmod = -1;    /* unnecessary, but... */

    /*
     * initialize tuple desc info
     */
    has_not_null = false;
    for (i = 0; i < natts; i++)
    {
        memcpy(relation->rd_att->attrs[i],
               &attrs[i],
               ATTRIBUTE_FIXED_PART_SIZE);
        has_not_null |= attrs[i].attnotnull;
        /* make sure attcacheoff is valid */
        relation->rd_att->attrs[i]->attcacheoff = -1;
    }

    /* initialize first attribute's attcacheoff, cf RelationBuildTupleDesc */
    relation->rd_att->attrs[0]->attcacheoff = 0;

    /* mark not-null status */
    if (has_not_null)
    {
        TupleConstr *constr = (TupleConstr *) palloc0(sizeof(TupleConstr));

        constr->has_not_null = true;
        relation->rd_att->constr = constr;
    }

    /*
     * initialize relation id from info in att array (my, this is ugly)
     */
    RelationGetRelid(relation) = relation->rd_att->attrs[0]->attrelid;

    /*
     * All relations made with formrdesc are mapped.  This is necessarily so
     * because there is no other way to know what filenode they currently
     * have.  In bootstrap mode, add them to the initial relation mapper data,
     * specifying that the initial filenode is the same as the OID.
     */
    relation->rd_rel->relfilenode = InvalidOid;
    if (IsBootstrapProcessingMode())
        RelationMapUpdateMap(RelationGetRelid(relation),
                             RelationGetRelid(relation),
                             isshared, true);

    /*
     * initialize the relation lock manager information
     */
    RelationInitLockInfo(relation);     /* see lmgr.c */

    /*
     * initialize physical addressing information for the relation
     */
    RelationInitPhysicalAddr(relation);
    relation->rd_ispopulated = true;

    /*
     * initialize the rel-has-index flag, using hardwired knowledge
     */
    if (IsBootstrapProcessingMode())
    {
        /* In bootstrap mode, we have no indexes */
        relation->rd_rel->relhasindex = false;
    }
    else
    {
        /* Otherwise, all the rels formrdesc is used for have indexes */
        relation->rd_rel->relhasindex = true;
    }

    /*
     * add new reldesc to relcache
     */
    RelationCacheInsert(relation);

    /* It's fully valid */
    relation->rd_isvalid = true;
}


/* ----------------------------------------------------------------
 *               Relation Descriptor Lookup Interface
 * ----------------------------------------------------------------
 */

/*
 *      RelationIdGetRelation
 *
 *      Lookup a reldesc by OID; make one if not already in cache.
 *
 *      Returns NULL if no pg_class row could be found for the given relid
 *      (suggesting we are trying to access a just-deleted relation).
 *      Any other error is reported via elog.
 *
 *      NB: caller should already have at least AccessShareLock on the
 *      relation ID, else there are nasty race conditions.
 *
 *      NB: relation ref count is incremented, or set to 1 if new entry.
 *      Caller should eventually decrement count.  (Usually,
 *      that happens by calling RelationClose().)
 */
Relation
RelationIdGetRelation(Oid relationId)
{
    Relation    rd;

    /*
     * first try to find reldesc in the cache
     */
    RelationIdCacheLookup(relationId, rd);

    if (RelationIsValid(rd))
    {
        RelationIncrementReferenceCount(rd);
        /* revalidate cache entry if necessary */
        if (!rd->rd_isvalid)
        {
            /*
             * Indexes only have a limited number of possible schema changes,
             * and we don't want to use the full-blown procedure because it's
             * a headache for indexes that reload itself depends on.
             */
            if (rd->rd_rel->relkind == RELKIND_INDEX)
                RelationReloadIndexInfo(rd);
            else
                RelationClearRelation(rd, true);
        }
        return rd;
    }

    /*
     * no reldesc in the cache, so have RelationBuildDesc() build one and add
     * it.
     */
    rd = RelationBuildDesc(relationId, true);
    if (RelationIsValid(rd))
        RelationIncrementReferenceCount(rd);
    return rd;
}

/* ----------------------------------------------------------------
 *              cache invalidation support routines
 * ----------------------------------------------------------------
 */

/*
 * RelationIncrementReferenceCount
 *      Increments relation reference count.
 *
 * Note: bootstrap mode has its own weird ideas about relation refcount
 * behavior; we ought to fix it someday, but for now, just disable
 * reference count ownership tracking in bootstrap mode.
 */
void
RelationIncrementReferenceCount(Relation rel)
{
    ResourceOwnerEnlargeRelationRefs(CurrentResourceOwner);
    rel->rd_refcnt += 1;
    if (!IsBootstrapProcessingMode())
        ResourceOwnerRememberRelationRef(CurrentResourceOwner, rel);
}

/*
 * RelationDecrementReferenceCount
 *      Decrements relation reference count.
 */
void
RelationDecrementReferenceCount(Relation rel)
{
    Assert(rel->rd_refcnt > 0);
    rel->rd_refcnt -= 1;
    if (!IsBootstrapProcessingMode())
        ResourceOwnerForgetRelationRef(CurrentResourceOwner, rel);
}

/*
 * RelationClose - close an open relation
 *
 *  Actually, we just decrement the refcount.
 *
 *  NOTE: if compiled with -DRELCACHE_FORCE_RELEASE then relcache entries
 *  will be freed as soon as their refcount goes to zero.  In combination
 *  with aset.c's CLOBBER_FREED_MEMORY option, this provides a good test
 *  to catch references to already-released relcache entries.  It slows
 *  things down quite a bit, however.
 */
void
RelationClose(Relation relation)
{
    /* Note: no locking manipulations needed */
    RelationDecrementReferenceCount(relation);

#ifdef RELCACHE_FORCE_RELEASE
    if (RelationHasReferenceCountZero(relation) &&
        relation->rd_createSubid == InvalidSubTransactionId &&
        relation->rd_newRelfilenodeSubid == InvalidSubTransactionId)
        RelationClearRelation(relation, false);
#endif
}

/*
 * RelationReloadIndexInfo - reload minimal information for an open index
 *
 *  This function is used only for indexes.  A relcache inval on an index
 *  can mean that its pg_class or pg_index row changed.  There are only
 *  very limited changes that are allowed to an existing index's schema,
 *  so we can update the relcache entry without a complete rebuild; which
 *  is fortunate because we can't rebuild an index entry that is "nailed"
 *  and/or in active use.  We support full replacement of the pg_class row,
 *  as well as updates of a few simple fields of the pg_index row.
 *
 *  We can't necessarily reread the catalog rows right away; we might be
 *  in a failed transaction when we receive the SI notification.  If so,
 *  RelationClearRelation just marks the entry as invalid by setting
 *  rd_isvalid to false.  This routine is called to fix the entry when it
 *  is next needed.
 *
 *  We assume that at the time we are called, we have at least AccessShareLock
 *  on the target index.  (Note: in the calls from RelationClearRelation,
 *  this is legitimate because we know the rel has positive refcount.)
 *
 *  If the target index is an index on pg_class or pg_index, we'd better have
 *  previously gotten at least AccessShareLock on its underlying catalog,
 *  else we are at risk of deadlock against someone trying to exclusive-lock
 *  the heap and index in that order.  This is ensured in current usage by
 *  only applying this to indexes being opened or having positive refcount.
 */
static void
RelationReloadIndexInfo(Relation relation)
{
    bool        indexOK;
    HeapTuple   pg_class_tuple;
    Form_pg_class relp;

    /* Should be called only for invalidated indexes */
    Assert(relation->rd_rel->relkind == RELKIND_INDEX &&
           !relation->rd_isvalid);
    /* Should be closed at smgr level */
    Assert(relation->rd_smgr == NULL);

    /* Must free any AM cached data upon relcache flush */
    if (relation->rd_amcache)
        pfree(relation->rd_amcache);
    relation->rd_amcache = NULL;

    /*
     * If it's a shared index, we might be called before backend startup has
     * finished selecting a database, in which case we have no way to read
     * pg_class yet.  However, a shared index can never have any significant
     * schema updates, so it's okay to ignore the invalidation signal.  Just
     * mark it valid and return without doing anything more.
     */
    if (relation->rd_rel->relisshared && !criticalRelcachesBuilt)
    {
        relation->rd_isvalid = true;
        return;
    }

    /*
     * Read the pg_class row
     *
     * Don't try to use an indexscan of pg_class_oid_index to reload the info
     * for pg_class_oid_index ...
     */
    indexOK = (RelationGetRelid(relation) != ClassOidIndexId);
    pg_class_tuple = ScanPgRelation(RelationGetRelid(relation), indexOK);
    if (!HeapTupleIsValid(pg_class_tuple))
        elog(ERROR, "could not find pg_class tuple for index %u",
             RelationGetRelid(relation));
    relp = (Form_pg_class) GETSTRUCT(pg_class_tuple);
    memcpy(relation->rd_rel, relp, CLASS_TUPLE_SIZE);
    /* Reload reloptions in case they changed */
    if (relation->rd_options)
        pfree(relation->rd_options);
    RelationParseRelOptions(relation, pg_class_tuple);
    /* done with pg_class tuple */
    heap_freetuple(pg_class_tuple);
    /* We must recalculate physical address in case it changed */
    RelationInitPhysicalAddr(relation);
    relation->rd_ispopulated = true;

    /*
     * For a non-system index, there are fields of the pg_index row that are
     * allowed to change, so re-read that row and update the relcache entry.
     * Most of the info derived from pg_index (such as support function lookup
     * info) cannot change, and indeed the whole point of this routine is to
     * update the relcache entry without clobbering that data; so wholesale
     * replacement is not appropriate.
     */
    if (!IsSystemRelation(relation))
    {
        HeapTuple   tuple;
        Form_pg_index index;

        tuple = SearchSysCache1(INDEXRELID,
                                ObjectIdGetDatum(RelationGetRelid(relation)));
        if (!HeapTupleIsValid(tuple))
            elog(ERROR, "cache lookup failed for index %u",
                 RelationGetRelid(relation));
        index = (Form_pg_index) GETSTRUCT(tuple);

        /*
         * Basically, let's just copy all the bool fields.  There are one or
         * two of these that can't actually change in the current code, but
         * it's not worth it to track exactly which ones they are.  None of
         * the array fields are allowed to change, though.
         */
        relation->rd_index->indisunique = index->indisunique;
        relation->rd_index->indisprimary = index->indisprimary;
        relation->rd_index->indisexclusion = index->indisexclusion;
        relation->rd_index->indimmediate = index->indimmediate;
        relation->rd_index->indisclustered = index->indisclustered;
        relation->rd_index->indisvalid = index->indisvalid;
        relation->rd_index->indcheckxmin = index->indcheckxmin;
        relation->rd_index->indisready = index->indisready;
        relation->rd_index->indislive = index->indislive;

        /* Copy xmin too, as that is needed to make sense of indcheckxmin */
        HeapTupleHeaderSetXmin(relation->rd_indextuple->t_data,
                               HeapTupleHeaderGetXmin(tuple->t_data));

        ReleaseSysCache(tuple);
    }

    /* Okay, now it's valid again */
    relation->rd_isvalid = true;
}

/*
 * RelationDestroyRelation
 *
 *  Physically delete a relation cache entry and all subsidiary data.
 *  Caller must already have unhooked the entry from the hash table.
 */
static void
RelationDestroyRelation(Relation relation)
{
    Assert(RelationHasReferenceCountZero(relation));

    /*
     * Make sure smgr and lower levels close the relation's files, if they
     * weren't closed already.  (This was probably done by caller, but let's
     * just be real sure.)
     */
    RelationCloseSmgr(relation);

    /*
     * Free all the subsidiary data structures of the relcache entry, then the
     * entry itself.
     */
    if (relation->rd_rel)
        pfree(relation->rd_rel);
    /* can't use DecrTupleDescRefCount here */
    Assert(relation->rd_att->tdrefcount > 0);
    if (--relation->rd_att->tdrefcount == 0)
        FreeTupleDesc(relation->rd_att);
    list_free(relation->rd_indexlist);
    bms_free(relation->rd_indexattr);
    FreeTriggerDesc(relation->trigdesc);
    if (relation->rd_options)
        pfree(relation->rd_options);
    if (relation->rd_indextuple)
        pfree(relation->rd_indextuple);
    if (relation->rd_am)
        pfree(relation->rd_am);
    if (relation->rd_indexcxt)
        MemoryContextDelete(relation->rd_indexcxt);
    if (relation->rd_rulescxt)
        MemoryContextDelete(relation->rd_rulescxt);
    if (relation->rd_fdwroutine)
        pfree(relation->rd_fdwroutine);
    pfree(relation);
}

/*
 * RelationClearRelation
 *
 *   Physically blow away a relation cache entry, or reset it and rebuild
 *   it from scratch (that is, from catalog entries).  The latter path is
 *   used when we are notified of a change to an open relation (one with
 *   refcount > 0).
 *
 *   NB: when rebuilding, we'd better hold some lock on the relation,
 *   else the catalog data we need to read could be changing under us.
 *   Also, a rel to be rebuilt had better have refcnt > 0.  This is because
 *   an sinval reset could happen while we're accessing the catalogs, and
 *   the rel would get blown away underneath us by RelationCacheInvalidate
 *   if it has zero refcnt.
 *
 *   The "rebuild" parameter is redundant in current usage because it has
 *   to match the relation's refcnt status, but we keep it as a crosscheck
 *   that we're doing what the caller expects.
 */
static void
RelationClearRelation(Relation relation, bool rebuild)
{
    /*
     * As per notes above, a rel to be rebuilt MUST have refcnt > 0; while of
     * course it would be a bad idea to blow away one with nonzero refcnt.
     */
    Assert(rebuild ?
           !RelationHasReferenceCountZero(relation) :
           RelationHasReferenceCountZero(relation));

    /*
     * Make sure smgr and lower levels close the relation's files, if they
     * weren't closed already.  If the relation is not getting deleted, the
     * next smgr access should reopen the files automatically.  This ensures
     * that the low-level file access state is updated after, say, a vacuum
     * truncation.
     */
    RelationCloseSmgr(relation);

    /*
     * Never, never ever blow away a nailed-in system relation, because we'd
     * be unable to recover.  However, we must redo RelationInitPhysicalAddr
     * in case it is a mapped relation whose mapping changed.
     *
     * If it's a nailed index, then we need to re-read the pg_class row to see
     * if its relfilenode changed.  We can't necessarily do that here, because
     * we might be in a failed transaction.  We assume it's okay to do it if
     * there are open references to the relcache entry (cf notes for
     * AtEOXact_RelationCache).  Otherwise just mark the entry as possibly
     * invalid, and it'll be fixed when next opened.
     */
    if (relation->rd_isnailed)
    {
        RelationInitPhysicalAddr(relation);
        if (relation->rd_rel->relkind == RELKIND_MATVIEW &&
            heap_is_matview_init_state(relation))
            relation->rd_ispopulated = false;
        else
            relation->rd_ispopulated = true;

        if (relation->rd_rel->relkind == RELKIND_INDEX)
        {
            relation->rd_isvalid = false;       /* needs to be revalidated */
            if (relation->rd_refcnt > 1)
                RelationReloadIndexInfo(relation);
        }
        return;
    }

    /*
     * Even non-system indexes should not be blown away if they are open and
     * have valid index support information.  This avoids problems with active
     * use of the index support information.  As with nailed indexes, we
     * re-read the pg_class row to handle possible physical relocation of the
     * index, and we check for pg_index updates too.
     */
    if (relation->rd_rel->relkind == RELKIND_INDEX &&
        relation->rd_refcnt > 0 &&
        relation->rd_indexcxt != NULL)
    {
        relation->rd_isvalid = false;   /* needs to be revalidated */
        RelationReloadIndexInfo(relation);
        return;
    }

    /* Mark it invalid until we've finished rebuild */
    relation->rd_isvalid = false;

    /*
     * If we're really done with the relcache entry, blow it away. But if
     * someone is still using it, reconstruct the whole deal without moving
     * the physical RelationData record (so that the someone's pointer is
     * still valid).
     */
    if (!rebuild)
    {
        /* Remove it from the hash table */
        RelationCacheDelete(relation);

        /* And release storage */
        RelationDestroyRelation(relation);
    }
    else
    {
        /*
         * Our strategy for rebuilding an open relcache entry is to build a
         * new entry from scratch, swap its contents with the old entry, and
         * finally delete the new entry (along with any infrastructure swapped
         * over from the old entry).  This is to avoid trouble in case an
         * error causes us to lose control partway through.  The old entry
         * will still be marked !rd_isvalid, so we'll try to rebuild it again
         * on next access.  Meanwhile it's not any less valid than it was
         * before, so any code that might expect to continue accessing it
         * isn't hurt by the rebuild failure.  (Consider for example a
         * subtransaction that ALTERs a table and then gets canceled partway
         * through the cache entry rebuild.  The outer transaction should
         * still see the not-modified cache entry as valid.)  The worst
         * consequence of an error is leaking the necessarily-unreferenced new
         * entry, and this shouldn't happen often enough for that to be a big
         * problem.
         *
         * When rebuilding an open relcache entry, we must preserve ref count,
         * rd_createSubid/rd_newRelfilenodeSubid, and rd_toastoid state.  Also
         * attempt to preserve the pg_class entry (rd_rel), tupledesc, and
         * rewrite-rule substructures in place, because various places assume
         * that these structures won't move while they are working with an
         * open relcache entry.  (Note: the refcount mechanism for tupledescs
         * might someday allow us to remove this hack for the tupledesc.)
         *
         * Note that this process does not touch CurrentResourceOwner; which
         * is good because whatever ref counts the entry may have do not
         * necessarily belong to that resource owner.
         */
        Relation    newrel;
        Oid         save_relid = RelationGetRelid(relation);
        bool        keep_tupdesc;
        bool        keep_rules;

        /* Build temporary entry, but don't link it into hashtable */
        newrel = RelationBuildDesc(save_relid, false);
        if (newrel == NULL)
        {
            /* Should only get here if relation was deleted */
            RelationCacheDelete(relation);
            RelationDestroyRelation(relation);
            elog(ERROR, "relation %u deleted while still in use", save_relid);
        }

        keep_tupdesc = equalTupleDescs(relation->rd_att, newrel->rd_att);
        keep_rules = equalRuleLocks(relation->rd_rules, newrel->rd_rules);

        /*
         * Perform swapping of the relcache entry contents.  Within this
         * process the old entry is momentarily invalid, so there *must* be no
         * possibility of CHECK_FOR_INTERRUPTS within this sequence. Do it in
         * all-in-line code for safety.
         *
         * Since the vast majority of fields should be swapped, our method is
         * to swap the whole structures and then re-swap those few fields we
         * didn't want swapped.
         */
#define SWAPFIELD(fldtype, fldname) \
        do { \
            fldtype _tmp = newrel->fldname; \
            newrel->fldname = relation->fldname; \
            relation->fldname = _tmp; \
        } while (0)

        /* swap all Relation struct fields */
        {
            RelationData tmpstruct;

            memcpy(&tmpstruct, newrel, sizeof(RelationData));
            memcpy(newrel, relation, sizeof(RelationData));
            memcpy(relation, &tmpstruct, sizeof(RelationData));
        }

        /* rd_smgr must not be swapped, due to back-links from smgr level */
        SWAPFIELD(SMgrRelation, rd_smgr);
        /* rd_refcnt must be preserved */
        SWAPFIELD(int, rd_refcnt);
        /* isnailed shouldn't change */
        Assert(newrel->rd_isnailed == relation->rd_isnailed);
        /* creation sub-XIDs must be preserved */
        SWAPFIELD(SubTransactionId, rd_createSubid);
        SWAPFIELD(SubTransactionId, rd_newRelfilenodeSubid);
        /* un-swap rd_rel pointers, swap contents instead */
        SWAPFIELD(Form_pg_class, rd_rel);
        /* ... but actually, we don't have to update newrel->rd_rel */
        memcpy(relation->rd_rel, newrel->rd_rel, CLASS_TUPLE_SIZE);
        /* preserve old tupledesc and rules if no logical change */
        if (keep_tupdesc)
            SWAPFIELD(TupleDesc, rd_att);
        if (keep_rules)
        {
            SWAPFIELD(RuleLock *, rd_rules);
            SWAPFIELD(MemoryContext, rd_rulescxt);
        }
        /* toast OID override must be preserved */
        SWAPFIELD(Oid, rd_toastoid);
        /* pgstat_info must be preserved */
        SWAPFIELD(struct PgStat_TableStatus *, pgstat_info);

#undef SWAPFIELD

        /* And now we can throw away the temporary entry */
        RelationDestroyRelation(newrel);
    }
}

/*
 * RelationFlushRelation
 *
 *   Rebuild the relation if it is open (refcount > 0), else blow it away.
 */
static void
RelationFlushRelation(Relation relation)
{
    if (relation->rd_createSubid != InvalidSubTransactionId ||
        relation->rd_newRelfilenodeSubid != InvalidSubTransactionId)
    {
        /*
         * New relcache entries are always rebuilt, not flushed; else we'd
         * forget the "new" status of the relation, which is a useful
         * optimization to have.  Ditto for the new-relfilenode status.
         *
         * The rel could have zero refcnt here, so temporarily increment the
         * refcnt to ensure it's safe to rebuild it.  We can assume that the
         * current transaction has some lock on the rel already.
         */
        RelationIncrementReferenceCount(relation);
        RelationClearRelation(relation, true);
        RelationDecrementReferenceCount(relation);
    }
    else
    {
        /*
         * Pre-existing rels can be dropped from the relcache if not open.
         */
        bool        rebuild = !RelationHasReferenceCountZero(relation);

        RelationClearRelation(relation, rebuild);
    }
}

/*
 * RelationForgetRelation - unconditionally remove a relcache entry
 *
 *         External interface for destroying a relcache entry when we
 *         drop the relation.
 */
void
RelationForgetRelation(Oid rid)
{
    Relation    relation;

    RelationIdCacheLookup(rid, relation);

    if (!PointerIsValid(relation))
        return;                 /* not in cache, nothing to do */

    if (!RelationHasReferenceCountZero(relation))
        elog(ERROR, "relation %u is still open", rid);

    /* Unconditionally destroy the relcache entry */
    RelationClearRelation(relation, false);
}

/*
 *      RelationCacheInvalidateEntry
 *
 *      This routine is invoked for SI cache flush messages.
 *
 * Any relcache entry matching the relid must be flushed.  (Note: caller has
 * already determined that the relid belongs to our database or is a shared
 * relation.)
 *
 * We used to skip local relations, on the grounds that they could
 * not be targets of cross-backend SI update messages; but it seems
 * safer to process them, so that our *own* SI update messages will
 * have the same effects during CommandCounterIncrement for both
 * local and nonlocal relations.
 */
void
RelationCacheInvalidateEntry(Oid relationId)
{
    Relation    relation;

    RelationIdCacheLookup(relationId, relation);

    if (PointerIsValid(relation))
    {
        relcacheInvalsReceived++;
        RelationFlushRelation(relation);
    }
}

/*
 * RelationCacheInvalidate
 *   Blow away cached relation descriptors that have zero reference counts,
 *   and rebuild those with positive reference counts.  Also reset the smgr
 *   relation cache and re-read relation mapping data.
 *
 *   This is currently used only to recover from SI message buffer overflow,
 *   so we do not touch new-in-transaction relations; they cannot be targets
 *   of cross-backend SI updates (and our own updates now go through a
 *   separate linked list that isn't limited by the SI message buffer size).
 *   Likewise, we need not discard new-relfilenode-in-transaction hints,
 *   since any invalidation of those would be a local event.
 *
 *   We do this in two phases: the first pass deletes deletable items, and
 *   the second one rebuilds the rebuildable items.  This is essential for
 *   safety, because hash_seq_search only copes with concurrent deletion of
 *   the element it is currently visiting.  If a second SI overflow were to
 *   occur while we are walking the table, resulting in recursive entry to
 *   this routine, we could crash because the inner invocation blows away
 *   the entry next to be visited by the outer scan.  But this way is OK,
 *   because (a) during the first pass we won't process any more SI messages,
 *   so hash_seq_search will complete safely; (b) during the second pass we
 *   only hold onto pointers to nondeletable entries.
 *
 *   The two-phase approach also makes it easy to update relfilenodes for
 *   mapped relations before we do anything else, and to ensure that the
 *   second pass processes nailed-in-cache items before other nondeletable
 *   items.  This should ensure that system catalogs are up to date before
 *   we attempt to use them to reload information about other open relations.
 */
void
RelationCacheInvalidate(void)
{
    HASH_SEQ_STATUS status;
    RelIdCacheEnt *idhentry;
    Relation    relation;
    List       *rebuildFirstList = NIL;
    List       *rebuildList = NIL;
    ListCell   *l;

    /*
     * Reload relation mapping data before starting to reconstruct cache.
     */
    RelationMapInvalidateAll();

    /* Phase 1 */
    hash_seq_init(&status, RelationIdCache);

    while ((idhentry = (RelIdCacheEnt *) hash_seq_search(&status)) != NULL)
    {
        relation = idhentry->reldesc;

        /* Must close all smgr references to avoid leaving dangling ptrs */
        RelationCloseSmgr(relation);

        /*
         * Ignore new relations; no other backend will manipulate them before
         * we commit.  Likewise, before replacing a relation's relfilenode, we
         * shall have acquired AccessExclusiveLock and drained any applicable
         * pending invalidations.
         */
        if (relation->rd_createSubid != InvalidSubTransactionId ||
            relation->rd_newRelfilenodeSubid != InvalidSubTransactionId)
            continue;

        relcacheInvalsReceived++;

        if (RelationHasReferenceCountZero(relation))
        {
            /* Delete this entry immediately */
            Assert(!relation->rd_isnailed);
            RelationClearRelation(relation, false);
        }
        else
        {
            /*
             * If it's a mapped relation, immediately update its rd_node in
             * case its relfilenode changed.  We must do this during phase 1
             * in case the relation is consulted during rebuild of other
             * relcache entries in phase 2.  It's safe since consulting the
             * map doesn't involve any access to relcache entries.
             */
            if (RelationIsMapped(relation))
                RelationInitPhysicalAddr(relation);

            /*
             * Add this entry to list of stuff to rebuild in second pass.
             * pg_class goes to the front of rebuildFirstList while
             * pg_class_oid_index goes to the back of rebuildFirstList, so
             * they are done first and second respectively.  Other nailed
             * relations go to the front of rebuildList, so they'll be done
             * next in no particular order; and everything else goes to the
             * back of rebuildList.
             */
            if (RelationGetRelid(relation) == RelationRelationId)
                rebuildFirstList = lcons(relation, rebuildFirstList);
            else if (RelationGetRelid(relation) == ClassOidIndexId)
                rebuildFirstList = lappend(rebuildFirstList, relation);
            else if (relation->rd_isnailed)
                rebuildList = lcons(relation, rebuildList);
            else
                rebuildList = lappend(rebuildList, relation);
        }
    }

    /*
     * Now zap any remaining smgr cache entries.  This must happen before we
     * start to rebuild entries, since that may involve catalog fetches which
     * will re-open catalog files.
     */
    smgrcloseall();

    /* Phase 2: rebuild the items found to need rebuild in phase 1 */
    foreach(l, rebuildFirstList)
    {
        relation = (Relation) lfirst(l);
        RelationClearRelation(relation, true);
    }
    list_free(rebuildFirstList);
    foreach(l, rebuildList)
    {
        relation = (Relation) lfirst(l);
        RelationClearRelation(relation, true);
    }
    list_free(rebuildList);
}

/*
 * RelationCloseSmgrByOid - close a relcache entry's smgr link
 *
 * Needed in some cases where we are changing a relation's physical mapping.
 * The link will be automatically reopened on next use.
 */
void
RelationCloseSmgrByOid(Oid relationId)
{
    Relation    relation;

    RelationIdCacheLookup(relationId, relation);

    if (!PointerIsValid(relation))
        return;                 /* not in cache, nothing to do */

    RelationCloseSmgr(relation);
}

/*
 * AtEOXact_RelationCache
 *
 *  Clean up the relcache at main-transaction commit or abort.
 *
 * Note: this must be called *before* processing invalidation messages.
 * In the case of abort, we don't want to try to rebuild any invalidated
 * cache entries (since we can't safely do database accesses).  Therefore
 * we must reset refcnts before handling pending invalidations.
 *
 * As of PostgreSQL 8.1, relcache refcnts should get released by the
 * ResourceOwner mechanism.  This routine just does a debugging
 * cross-check that no pins remain.  However, we also need to do special
 * cleanup when the current transaction created any relations or made use
 * of forced index lists.
 */
void
AtEOXact_RelationCache(bool isCommit)
{
    HASH_SEQ_STATUS status;
    RelIdCacheEnt *idhentry;
    int         i;

    /*
     * Unless the eoxact_list[] overflowed, we only need to examine the rels
     * listed in it.  Otherwise fall back on a hash_seq_search scan.
     *
     * For simplicity, eoxact_list[] entries are not deleted till end of
     * top-level transaction, even though we could remove them at
     * subtransaction end in some cases, or remove relations from the list if
     * they are cleared for other reasons.  Therefore we should expect the
     * case that list entries are not found in the hashtable; if not, there's
     * nothing to do for them.
     */
    if (eoxact_list_overflowed)
    {
        hash_seq_init(&status, RelationIdCache);
        while ((idhentry = (RelIdCacheEnt *) hash_seq_search(&status)) != NULL)
        {
            AtEOXact_cleanup(idhentry->reldesc, isCommit);
        }
    }
    else
    {
        for (i = 0; i < eoxact_list_len; i++)
        {
            idhentry = (RelIdCacheEnt *) hash_search(RelationIdCache,
                                                     (void *) &eoxact_list[i],
                                                     HASH_FIND,
                                                     NULL);
            if (idhentry != NULL)
                AtEOXact_cleanup(idhentry->reldesc, isCommit);
        }
    }

    /* Now we're out of the transaction and can clear the list */
    eoxact_list_len = 0;
    eoxact_list_overflowed = false;
}

/*
 * AtEOXact_cleanup
 *
 *  Clean up a single rel at main-transaction commit or abort
 *
 * NB: this processing must be idempotent, because EOXactListAdd() doesn't
 * bother to prevent duplicate entries in eoxact_list[].
 */
static void
AtEOXact_cleanup(Relation relation, bool isCommit)
{
        /*
         * The relcache entry's ref count should be back to its normal
         * not-in-a-transaction state: 0 unless it's nailed in cache.
         *
         * In bootstrap mode, this is NOT true, so don't check it --- the
         * bootstrap code expects relations to stay open across start/commit
         * transaction calls.  (That seems bogus, but it's not worth fixing.)
         *
         * Note: ideally this check would be applied to every relcache entry,
         * not just those that have eoxact work to do.  But it's not worth
         * forcing a scan of the whole relcache just for this.  (Moreover,
         * doing so would mean that assert-enabled testing never tests the
         * hash_search code path above, which seems a bad idea.)
         */
#ifdef USE_ASSERT_CHECKING
        if (!IsBootstrapProcessingMode())
        {
            int         expected_refcnt;

            expected_refcnt = relation->rd_isnailed ? 1 : 0;
            Assert(relation->rd_refcnt == expected_refcnt);
        }
#endif

        /*
         * Is it a relation created in the current transaction?
         *
         * During commit, reset the flag to zero, since we are now out of the
         * creating transaction.  During abort, simply delete the relcache
         * entry --- it isn't interesting any longer.  (NOTE: if we have
         * forgotten the new-ness of a new relation due to a forced cache
         * flush, the entry will get deleted anyway by shared-cache-inval
         * processing of the aborted pg_class insertion.)
         */
        if (relation->rd_createSubid != InvalidSubTransactionId)
        {
            if (isCommit)
                relation->rd_createSubid = InvalidSubTransactionId;
            else
            {
                RelationClearRelation(relation, false);
                return;
            }
        }

        /*
         * Likewise, reset the hint about the relfilenode being new.
         */
        relation->rd_newRelfilenodeSubid = InvalidSubTransactionId;

        /*
         * Flush any temporary index list.
         */
        if (relation->rd_indexvalid == 2)
        {
            list_free(relation->rd_indexlist);
            relation->rd_indexlist = NIL;
            relation->rd_oidindex = InvalidOid;
            relation->rd_indexvalid = 0;
        }
}

/*
 * AtEOSubXact_RelationCache
 *
 *  Clean up the relcache at sub-transaction commit or abort.
 *
 * Note: this must be called *before* processing invalidation messages.
 */
void
AtEOSubXact_RelationCache(bool isCommit, SubTransactionId mySubid,
                          SubTransactionId parentSubid)
{
    HASH_SEQ_STATUS status;
    RelIdCacheEnt *idhentry;
    int         i;

    /*
     * Unless the eoxact_list[] overflowed, we only need to examine the rels
     * listed in it.  Otherwise fall back on a hash_seq_search scan.  Same
     * logic as in AtEOXact_RelationCache.
     */
    if (eoxact_list_overflowed)
    {
        hash_seq_init(&status, RelationIdCache);
        while ((idhentry = (RelIdCacheEnt *) hash_seq_search(&status)) != NULL)
        {
            AtEOSubXact_cleanup(idhentry->reldesc, isCommit,
                                mySubid, parentSubid);
        }
    }
    else
    {
        for (i = 0; i < eoxact_list_len; i++)
        {
            idhentry = (RelIdCacheEnt *) hash_search(RelationIdCache,
                                                     (void *) &eoxact_list[i],
                                                     HASH_FIND,
                                                     NULL);
            if (idhentry != NULL)
                AtEOSubXact_cleanup(idhentry->reldesc, isCommit,
                                    mySubid, parentSubid);
        }
    }

    /* Don't reset the list; we still need more cleanup later */
}

/*
 * AtEOSubXact_cleanup
 *
 *  Clean up a single rel at subtransaction commit or abort
 *
 * NB: this processing must be idempotent, because EOXactListAdd() doesn't
 * bother to prevent duplicate entries in eoxact_list[].
 */
static void
AtEOSubXact_cleanup(Relation relation, bool isCommit,
                    SubTransactionId mySubid, SubTransactionId parentSubid)
{
        /*
         * Is it a relation created in the current subtransaction?
         *
         * During subcommit, mark it as belonging to the parent, instead.
         * During subabort, simply delete the relcache entry.
         */
        if (relation->rd_createSubid == mySubid)
        {
            if (isCommit)
                relation->rd_createSubid = parentSubid;
            else
            {
                RelationClearRelation(relation, false);
                return;
            }
        }

        /*
         * Likewise, update or drop any new-relfilenode-in-subtransaction
         * hint.
         */
        if (relation->rd_newRelfilenodeSubid == mySubid)
        {
            if (isCommit)
                relation->rd_newRelfilenodeSubid = parentSubid;
            else
                relation->rd_newRelfilenodeSubid = InvalidSubTransactionId;
        }

        /*
         * Flush any temporary index list.
         */
        if (relation->rd_indexvalid == 2)
        {
            list_free(relation->rd_indexlist);
            relation->rd_indexlist = NIL;
            relation->rd_oidindex = InvalidOid;
            relation->rd_indexvalid = 0;
        }
}


/*
 *      RelationBuildLocalRelation
 *          Build a relcache entry for an about-to-be-created relation,
 *          and enter it into the relcache.
 */
Relation
RelationBuildLocalRelation(const char *relname,
                           Oid relnamespace,
                           TupleDesc tupDesc,
                           Oid relid,
                           Oid relfilenode,
                           Oid reltablespace,
                           bool shared_relation,
                           bool mapped_relation,
                           char relpersistence,
                           char relkind)
{
    Relation    rel;
    MemoryContext oldcxt;
    int         natts = tupDesc->natts;
    int         i;
    bool        has_not_null;
    bool        nailit;

    AssertArg(natts >= 0);

    /*
     * check for creation of a rel that must be nailed in cache.
     *
     * XXX this list had better match the relations specially handled in
     * RelationCacheInitializePhase2/3.
     */
    switch (relid)
    {
        case DatabaseRelationId:
        case AuthIdRelationId:
        case AuthMemRelationId:
        case RelationRelationId:
        case AttributeRelationId:
        case ProcedureRelationId:
        case TypeRelationId:
            nailit = true;
            break;
        default:
            nailit = false;
            break;
    }

    /*
     * check that hardwired list of shared rels matches what's in the
     * bootstrap .bki file.  If you get a failure here during initdb, you
     * probably need to fix IsSharedRelation() to match whatever you've done
     * to the set of shared relations.
     */
    if (shared_relation != IsSharedRelation(relid))
        elog(ERROR, "shared_relation flag for \"%s\" does not match IsSharedRelation(%u)",
             relname, relid);

    /* Shared relations had better be mapped, too */
    Assert(mapped_relation || !shared_relation);

    /*
     * switch to the cache context to create the relcache entry.
     */
    if (!CacheMemoryContext)
        CreateCacheMemoryContext();

    oldcxt = MemoryContextSwitchTo(CacheMemoryContext);

    /*
     * allocate a new relation descriptor and fill in basic state fields.
     */
    rel = (Relation) palloc0(sizeof(RelationData));

    /* make sure relation is marked as having no open file yet */
    rel->rd_smgr = NULL;

    /* mark it nailed if appropriate */
    rel->rd_isnailed = nailit;

    rel->rd_refcnt = nailit ? 1 : 0;

    /* it's being created in this transaction */
    rel->rd_createSubid = GetCurrentSubTransactionId();
    rel->rd_newRelfilenodeSubid = InvalidSubTransactionId;

    /*
     * create a new tuple descriptor from the one passed in.  We do this
     * partly to copy it into the cache context, and partly because the new
     * relation can't have any defaults or constraints yet; they have to be
     * added in later steps, because they require additions to multiple system
     * catalogs.  We can copy attnotnull constraints here, however.
     */
    rel->rd_att = CreateTupleDescCopy(tupDesc);
    rel->rd_att->tdrefcount = 1;    /* mark as refcounted */
    has_not_null = false;
    for (i = 0; i < natts; i++)
    {
        rel->rd_att->attrs[i]->attnotnull = tupDesc->attrs[i]->attnotnull;
        has_not_null |= tupDesc->attrs[i]->attnotnull;
    }

    if (has_not_null)
    {
        TupleConstr *constr = (TupleConstr *) palloc0(sizeof(TupleConstr));

        constr->has_not_null = true;
        rel->rd_att->constr = constr;
    }

    /*
     * initialize relation tuple form (caller may add/override data later)
     */
    rel->rd_rel = (Form_pg_class) palloc0(CLASS_TUPLE_SIZE);

    namestrcpy(&rel->rd_rel->relname, relname);
    rel->rd_rel->relnamespace = relnamespace;

    rel->rd_rel->relkind = relkind;
    rel->rd_rel->relhasoids = rel->rd_att->tdhasoid;
    rel->rd_rel->relnatts = natts;
    rel->rd_rel->reltype = InvalidOid;
    /* needed when bootstrapping: */
    rel->rd_rel->relowner = BOOTSTRAP_SUPERUSERID;

    /* set up persistence and relcache fields dependent on it */
    rel->rd_rel->relpersistence = relpersistence;
    switch (relpersistence)
    {
        case RELPERSISTENCE_UNLOGGED:
        case RELPERSISTENCE_PERMANENT:
            rel->rd_backend = InvalidBackendId;
            rel->rd_islocaltemp = false;
            break;
        case RELPERSISTENCE_TEMP:
            Assert(isTempOrToastNamespace(relnamespace));
            rel->rd_backend = MyBackendId;
            rel->rd_islocaltemp = true;
            break;
        default:
            elog(ERROR, "invalid relpersistence: %c", relpersistence);
            break;
    }

    /*
     * Insert relation physical and logical identifiers (OIDs) into the right
     * places.  For a mapped relation, we set relfilenode to zero and rely on
     * RelationInitPhysicalAddr to consult the map.
     */
    rel->rd_rel->relisshared = shared_relation;

    RelationGetRelid(rel) = relid;

    for (i = 0; i < natts; i++)
        rel->rd_att->attrs[i]->attrelid = relid;

    rel->rd_rel->reltablespace = reltablespace;

    if (mapped_relation)
    {
        rel->rd_rel->relfilenode = InvalidOid;
        /* Add it to the active mapping information */
        RelationMapUpdateMap(relid, relfilenode, shared_relation, true);
    }
    else
        rel->rd_rel->relfilenode = relfilenode;

    RelationInitLockInfo(rel);  /* see lmgr.c */

    RelationInitPhysicalAddr(rel);

    /* materialized view not initially scannable */
    if (relkind == RELKIND_MATVIEW)
        rel->rd_ispopulated = false;
    else
        rel->rd_ispopulated = true;

    /*
     * Okay to insert into the relcache hash tables.
     */
    RelationCacheInsert(rel);

    /*
     * Flag relation as needing eoxact cleanup (to clear rd_createSubid).
     * We can't do this before storing relid in it.
     */
    EOXactListAdd(rel);

    /*
     * done building relcache entry.
     */
    MemoryContextSwitchTo(oldcxt);

    /* It's fully valid */
    rel->rd_isvalid = true;

    /*
     * Caller expects us to pin the returned entry.
     */
    RelationIncrementReferenceCount(rel);

    return rel;
}


/*
 * RelationSetNewRelfilenode
 *
 * Assign a new relfilenode (physical file name) to the relation.
 *
 * This allows a full rewrite of the relation to be done with transactional
 * safety (since the filenode assignment can be rolled back).  Note however
 * that there is no simple way to access the relation's old data for the
 * remainder of the current transaction.  This limits the usefulness to cases
 * such as TRUNCATE or rebuilding an index from scratch.
 *
 * Caller must already hold exclusive lock on the relation.
 *
 * The relation is marked with relfrozenxid = freezeXid (InvalidTransactionId
 * must be passed for indexes and sequences).  This should be a lower bound on
 * the XIDs that will be put into the new relation contents.
 */
void
RelationSetNewRelfilenode(Relation relation, TransactionId freezeXid,
                          MultiXactId minmulti)
{
    Oid         newrelfilenode;
    RelFileNodeBackend newrnode;
    Relation    pg_class;
    HeapTuple   tuple;
    Form_pg_class classform;

    /* Indexes, sequences must have Invalid frozenxid; other rels must not */
    Assert((relation->rd_rel->relkind == RELKIND_INDEX ||
            relation->rd_rel->relkind == RELKIND_SEQUENCE) ?
           freezeXid == InvalidTransactionId :
           TransactionIdIsNormal(freezeXid));
    Assert(TransactionIdIsNormal(freezeXid) == MultiXactIdIsValid(minmulti));

    /* Allocate a new relfilenode */
    newrelfilenode = GetNewRelFileNode(relation->rd_rel->reltablespace, NULL,
                                       relation->rd_rel->relpersistence);

    /*
     * Get a writable copy of the pg_class tuple for the given relation.
     */
    pg_class = heap_open(RelationRelationId, RowExclusiveLock);

    tuple = SearchSysCacheCopy1(RELOID,
                                ObjectIdGetDatum(RelationGetRelid(relation)));
    if (!HeapTupleIsValid(tuple))
        elog(ERROR, "could not find tuple for relation %u",
             RelationGetRelid(relation));
    classform = (Form_pg_class) GETSTRUCT(tuple);

    /*
     * Create storage for the main fork of the new relfilenode.
     *
     * NOTE: any conflict in relfilenode value will be caught here, if
     * GetNewRelFileNode messes up for any reason.
     */
    newrnode.node = relation->rd_node;
    newrnode.node.relNode = newrelfilenode;
    newrnode.backend = relation->rd_backend;
    RelationCreateStorage(newrnode.node, relation->rd_rel->relpersistence);
    smgrclosenode(newrnode);

    /*
     * Schedule unlinking of the old storage at transaction commit.
     */
    RelationDropStorage(relation);

    /*
     * Now update the pg_class row.  However, if we're dealing with a mapped
     * index, pg_class.relfilenode doesn't change; instead we have to send the
     * update to the relation mapper.
     */
    if (RelationIsMapped(relation))
        RelationMapUpdateMap(RelationGetRelid(relation),
                             newrelfilenode,
                             relation->rd_rel->relisshared,
                             false);
    else
        classform->relfilenode = newrelfilenode;

    /* These changes are safe even for a mapped relation */
    if (relation->rd_rel->relkind != RELKIND_SEQUENCE)
    {
        classform->relpages = 0;    /* it's empty until further notice */
        classform->reltuples = 0;
        classform->relallvisible = 0;
    }
    classform->relfrozenxid = freezeXid;
    classform->relminmxid = minmulti;

    simple_heap_update(pg_class, &tuple->t_self, tuple);
    CatalogUpdateIndexes(pg_class, tuple);

    heap_freetuple(tuple);

    heap_close(pg_class, RowExclusiveLock);

    /*
     * Make the pg_class row change visible, as well as the relation map
     * change if any.  This will cause the relcache entry to get updated, too.
     */
    CommandCounterIncrement();

    /*
     * Mark the rel as having been given a new relfilenode in the current
     * (sub) transaction.  This is a hint that can be used to optimize later
     * operations on the rel in the same transaction.
     */
    relation->rd_newRelfilenodeSubid = GetCurrentSubTransactionId();

    /* Flag relation as needing eoxact cleanup (to remove the hint) */
    EOXactListAdd(relation);
}


/*
 *      RelationCacheInitialize
 *
 *      This initializes the relation descriptor cache.  At the time
 *      that this is invoked, we can't do database access yet (mainly
 *      because the transaction subsystem is not up); all we are doing
 *      is making an empty cache hashtable.  This must be done before
 *      starting the initialization transaction, because otherwise
 *      AtEOXact_RelationCache would crash if that transaction aborts
 *      before we can get the relcache set up.
 */

#define INITRELCACHESIZE        400

void
RelationCacheInitialize(void)
{
    HASHCTL     ctl;

    /*
     * make sure cache memory context exists
     */
    if (!CacheMemoryContext)
        CreateCacheMemoryContext();

    /*
     * create hashtable that indexes the relcache
     */
    MemSet(&ctl, 0, sizeof(ctl));
    ctl.keysize = sizeof(Oid);
    ctl.entrysize = sizeof(RelIdCacheEnt);
    ctl.hash = oid_hash;
    RelationIdCache = hash_create("Relcache by OID", INITRELCACHESIZE,
                                  &ctl, HASH_ELEM | HASH_FUNCTION);

    /*
     * relation mapper needs to be initialized too
     */
    RelationMapInitialize();
}

/*
 *      RelationCacheInitializePhase2
 *
 *      This is called to prepare for access to shared catalogs during startup.
 *      We must at least set up nailed reldescs for pg_database, pg_authid,
 *      and pg_auth_members.  Ideally we'd like to have reldescs for their
 *      indexes, too.  We attempt to load this information from the shared
 *      relcache init file.  If that's missing or broken, just make phony
 *      entries for the catalogs themselves.  RelationCacheInitializePhase3
 *      will clean up as needed.
 */
void
RelationCacheInitializePhase2(void)
{
    MemoryContext oldcxt;

    /*
     * relation mapper needs initialized too
     */
    RelationMapInitializePhase2();

    /*
     * In bootstrap mode, the shared catalogs aren't there yet anyway, so do
     * nothing.
     */
    if (IsBootstrapProcessingMode())
        return;

    /*
     * switch to cache memory context
     */
    oldcxt = MemoryContextSwitchTo(CacheMemoryContext);

    /*
     * Try to load the shared relcache cache file.  If unsuccessful, bootstrap
     * the cache with pre-made descriptors for the critical shared catalogs.
     */
    if (!load_relcache_init_file(true))
    {
        formrdesc("pg_database", DatabaseRelation_Rowtype_Id, true,
                  true, Natts_pg_database, Desc_pg_database);
        formrdesc("pg_authid", AuthIdRelation_Rowtype_Id, true,
                  true, Natts_pg_authid, Desc_pg_authid);
        formrdesc("pg_auth_members", AuthMemRelation_Rowtype_Id, true,
                  false, Natts_pg_auth_members, Desc_pg_auth_members);

#define NUM_CRITICAL_SHARED_RELS    3   /* fix if you change list above */
    }

    MemoryContextSwitchTo(oldcxt);
}

/*
 *      RelationCacheInitializePhase3
 *
 *      This is called as soon as the catcache and transaction system
 *      are functional and we have determined MyDatabaseId.  At this point
 *      we can actually read data from the database's system catalogs.
 *      We first try to read pre-computed relcache entries from the local
 *      relcache init file.  If that's missing or broken, make phony entries
 *      for the minimum set of nailed-in-cache relations.  Then (unless
 *      bootstrapping) make sure we have entries for the critical system
 *      indexes.  Once we've done all this, we have enough infrastructure to
 *      open any system catalog or use any catcache.  The last step is to
 *      rewrite the cache files if needed.
 */
void
RelationCacheInitializePhase3(void)
{
    HASH_SEQ_STATUS status;
    RelIdCacheEnt *idhentry;
    MemoryContext oldcxt;
    bool        needNewCacheFile = !criticalSharedRelcachesBuilt;

    /*
     * relation mapper needs initialized too
     */
    RelationMapInitializePhase3();

    /*
     * switch to cache memory context
     */
    oldcxt = MemoryContextSwitchTo(CacheMemoryContext);

    /*
     * Try to load the local relcache cache file.  If unsuccessful, bootstrap
     * the cache with pre-made descriptors for the critical "nailed-in" system
     * catalogs.
     */
    if (IsBootstrapProcessingMode() ||
        !load_relcache_init_file(false))
    {
        needNewCacheFile = true;

        formrdesc("pg_class", RelationRelation_Rowtype_Id, false,
                  true, Natts_pg_class, Desc_pg_class);
        formrdesc("pg_attribute", AttributeRelation_Rowtype_Id, false,
                  false, Natts_pg_attribute, Desc_pg_attribute);
        formrdesc("pg_proc", ProcedureRelation_Rowtype_Id, false,
                  true, Natts_pg_proc, Desc_pg_proc);
        formrdesc("pg_type", TypeRelation_Rowtype_Id, false,
                  true, Natts_pg_type, Desc_pg_type);

#define NUM_CRITICAL_LOCAL_RELS 4       /* fix if you change list above */
    }

    MemoryContextSwitchTo(oldcxt);

    /* In bootstrap mode, the faked-up formrdesc info is all we'll have */
    if (IsBootstrapProcessingMode())
        return;

    /*
     * If we didn't get the critical system indexes loaded into relcache, do
     * so now.  These are critical because the catcache and/or opclass cache
     * depend on them for fetches done during relcache load.  Thus, we have an
     * infinite-recursion problem.  We can break the recursion by doing
     * heapscans instead of indexscans at certain key spots. To avoid hobbling
     * performance, we only want to do that until we have the critical indexes
     * loaded into relcache.  Thus, the flag criticalRelcachesBuilt is used to
     * decide whether to do heapscan or indexscan at the key spots, and we set
     * it true after we've loaded the critical indexes.
     *
     * The critical indexes are marked as "nailed in cache", partly to make it
     * easy for load_relcache_init_file to count them, but mainly because we
     * cannot flush and rebuild them once we've set criticalRelcachesBuilt to
     * true.  (NOTE: perhaps it would be possible to reload them by
     * temporarily setting criticalRelcachesBuilt to false again.  For now,
     * though, we just nail 'em in.)
     *
     * RewriteRelRulenameIndexId and TriggerRelidNameIndexId are not critical
     * in the same way as the others, because the critical catalogs don't
     * (currently) have any rules or triggers, and so these indexes can be
     * rebuilt without inducing recursion.  However they are used during
     * relcache load when a rel does have rules or triggers, so we choose to
     * nail them for performance reasons.
     */
    if (!criticalRelcachesBuilt)
    {
        load_critical_index(ClassOidIndexId,
                            RelationRelationId);
        load_critical_index(AttributeRelidNumIndexId,
                            AttributeRelationId);
        load_critical_index(IndexRelidIndexId,
                            IndexRelationId);
        load_critical_index(OpclassOidIndexId,
                            OperatorClassRelationId);
        load_critical_index(AccessMethodProcedureIndexId,
                            AccessMethodProcedureRelationId);
        load_critical_index(RewriteRelRulenameIndexId,
                            RewriteRelationId);
        load_critical_index(TriggerRelidNameIndexId,
                            TriggerRelationId);

#define NUM_CRITICAL_LOCAL_INDEXES  7   /* fix if you change list above */

        criticalRelcachesBuilt = true;
    }

    /*
     * Process critical shared indexes too.
     *
     * DatabaseNameIndexId isn't critical for relcache loading, but rather for
     * initial lookup of MyDatabaseId, without which we'll never find any
     * non-shared catalogs at all.  Autovacuum calls InitPostgres with a
     * database OID, so it instead depends on DatabaseOidIndexId.  We also
     * need to nail up some indexes on pg_authid and pg_auth_members for use
     * during client authentication.
     */
    if (!criticalSharedRelcachesBuilt)
    {
        load_critical_index(DatabaseNameIndexId,
                            DatabaseRelationId);
        load_critical_index(DatabaseOidIndexId,
                            DatabaseRelationId);
        load_critical_index(AuthIdRolnameIndexId,
                            AuthIdRelationId);
        load_critical_index(AuthIdOidIndexId,
                            AuthIdRelationId);
        load_critical_index(AuthMemMemRoleIndexId,
                            AuthMemRelationId);

#define NUM_CRITICAL_SHARED_INDEXES 5   /* fix if you change list above */

        criticalSharedRelcachesBuilt = true;
    }

    /*
     * Now, scan all the relcache entries and update anything that might be
     * wrong in the results from formrdesc or the relcache cache file. If we
     * faked up relcache entries using formrdesc, then read the real pg_class
     * rows and replace the fake entries with them. Also, if any of the
     * relcache entries have rules or triggers, load that info the hard way
     * since it isn't recorded in the cache file.
     *
     * Whenever we access the catalogs to read data, there is a possibility of
     * a shared-inval cache flush causing relcache entries to be removed.
     * Since hash_seq_search only guarantees to still work after the *current*
     * entry is removed, it's unsafe to continue the hashtable scan afterward.
     * We handle this by restarting the scan from scratch after each access.
     * This is theoretically O(N^2), but the number of entries that actually
     * need to be fixed is small enough that it doesn't matter.
     */
    hash_seq_init(&status, RelationIdCache);

    while ((idhentry = (RelIdCacheEnt *) hash_seq_search(&status)) != NULL)
    {
        Relation    relation = idhentry->reldesc;
        bool        restart = false;

        /*
         * Make sure *this* entry doesn't get flushed while we work with it.
         */
        RelationIncrementReferenceCount(relation);

        /*
         * If it's a faked-up entry, read the real pg_class tuple.
         */
        if (relation->rd_rel->relowner == InvalidOid)
        {
            HeapTuple   htup;
            Form_pg_class relp;

            htup = SearchSysCache1(RELOID,
                               ObjectIdGetDatum(RelationGetRelid(relation)));
            if (!HeapTupleIsValid(htup))
                elog(FATAL, "cache lookup failed for relation %u",
                     RelationGetRelid(relation));
            relp = (Form_pg_class) GETSTRUCT(htup);

            /*
             * Copy tuple to relation->rd_rel. (See notes in
             * AllocateRelationDesc())
             */
            memcpy((char *) relation->rd_rel, (char *) relp, CLASS_TUPLE_SIZE);

            /* Update rd_options while we have the tuple */
            if (relation->rd_options)
                pfree(relation->rd_options);
            RelationParseRelOptions(relation, htup);

            /*
             * Check the values in rd_att were set up correctly.  (We cannot
             * just copy them over now: formrdesc must have set up the rd_att
             * data correctly to start with, because it may already have been
             * copied into one or more catcache entries.)
             */
            Assert(relation->rd_att->tdtypeid == relp->reltype);
            Assert(relation->rd_att->tdtypmod == -1);
            Assert(relation->rd_att->tdhasoid == relp->relhasoids);

            ReleaseSysCache(htup);

            /* relowner had better be OK now, else we'll loop forever */
            if (relation->rd_rel->relowner == InvalidOid)
                elog(ERROR, "invalid relowner in pg_class entry for \"%s\"",
                     RelationGetRelationName(relation));

            restart = true;
        }

        /*
         * Fix data that isn't saved in relcache cache file.
         *
         * relhasrules or relhastriggers could possibly be wrong or out of
         * date.  If we don't actually find any rules or triggers, clear the
         * local copy of the flag so that we don't get into an infinite loop
         * here.  We don't make any attempt to fix the pg_class entry, though.
         */
        if (relation->rd_rel->relhasrules && relation->rd_rules == NULL)
        {
            RelationBuildRuleLock(relation);
            if (relation->rd_rules == NULL)
                relation->rd_rel->relhasrules = false;
            restart = true;
        }
        if (relation->rd_rel->relhastriggers && relation->trigdesc == NULL)
        {
            RelationBuildTriggers(relation);
            if (relation->trigdesc == NULL)
                relation->rd_rel->relhastriggers = false;
            restart = true;
        }

        /* Release hold on the relation */
        RelationDecrementReferenceCount(relation);

        /* Now, restart the hashtable scan if needed */
        if (restart)
        {
            hash_seq_term(&status);
            hash_seq_init(&status, RelationIdCache);
        }
    }

    /*
     * Lastly, write out new relcache cache files if needed.  We don't bother
     * to distinguish cases where only one of the two needs an update.
     */
    if (needNewCacheFile)
    {
        /*
         * Force all the catcaches to finish initializing and thereby open the
         * catalogs and indexes they use.  This will preload the relcache with
         * entries for all the most important system catalogs and indexes, so
         * that the init files will be most useful for future backends.
         */
        InitCatalogCachePhase2();

        /* reset initFileRelationIds list; we'll fill it during write */
        initFileRelationIds = NIL;

        /* now write the files */
        write_relcache_init_file(true);
        write_relcache_init_file(false);
    }
}

/*
 * Load one critical system index into the relcache
 *
 * indexoid is the OID of the target index, heapoid is the OID of the catalog
 * it belongs to.
 */
static void
load_critical_index(Oid indexoid, Oid heapoid)
{
    Relation    ird;

    /*
     * We must lock the underlying catalog before locking the index to avoid
     * deadlock, since RelationBuildDesc might well need to read the catalog,
     * and if anyone else is exclusive-locking this catalog and index they'll
     * be doing it in that order.
     */
    LockRelationOid(heapoid, AccessShareLock);
    LockRelationOid(indexoid, AccessShareLock);
    ird = RelationBuildDesc(indexoid, true);
    if (ird == NULL)
        elog(PANIC, "could not open critical system index %u", indexoid);
    ird->rd_isnailed = true;
    ird->rd_refcnt = 1;
    UnlockRelationOid(indexoid, AccessShareLock);
    UnlockRelationOid(heapoid, AccessShareLock);
}

/*
 * GetPgClassDescriptor -- get a predefined tuple descriptor for pg_class
 * GetPgIndexDescriptor -- get a predefined tuple descriptor for pg_index
 *
 * We need this kluge because we have to be able to access non-fixed-width
 * fields of pg_class and pg_index before we have the standard catalog caches
 * available.  We use predefined data that's set up in just the same way as
 * the bootstrapped reldescs used by formrdesc().  The resulting tupdesc is
 * not 100% kosher: it does not have the correct rowtype OID in tdtypeid, nor
 * does it have a TupleConstr field.  But it's good enough for the purpose of
 * extracting fields.
 */
static TupleDesc
BuildHardcodedDescriptor(int natts, const FormData_pg_attribute *attrs,
                         bool hasoids)
{
    TupleDesc   result;
    MemoryContext oldcxt;
    int         i;

    oldcxt = MemoryContextSwitchTo(CacheMemoryContext);

    result = CreateTemplateTupleDesc(natts, hasoids);
    result->tdtypeid = RECORDOID;       /* not right, but we don't care */
    result->tdtypmod = -1;

    for (i = 0; i < natts; i++)
    {
        memcpy(result->attrs[i], &attrs[i], ATTRIBUTE_FIXED_PART_SIZE);
        /* make sure attcacheoff is valid */
        result->attrs[i]->attcacheoff = -1;
    }

    /* initialize first attribute's attcacheoff, cf RelationBuildTupleDesc */
    result->attrs[0]->attcacheoff = 0;

    /* Note: we don't bother to set up a TupleConstr entry */

    MemoryContextSwitchTo(oldcxt);

    return result;
}

static TupleDesc
GetPgClassDescriptor(void)
{
    static TupleDesc pgclassdesc = NULL;

    /* Already done? */
    if (pgclassdesc == NULL)
        pgclassdesc = BuildHardcodedDescriptor(Natts_pg_class,
                                               Desc_pg_class,
                                               true);

    return pgclassdesc;
}

static TupleDesc
GetPgIndexDescriptor(void)
{
    static TupleDesc pgindexdesc = NULL;

    /* Already done? */
    if (pgindexdesc == NULL)
        pgindexdesc = BuildHardcodedDescriptor(Natts_pg_index,
                                               Desc_pg_index,
                                               false);

    return pgindexdesc;
}

/*
 * Load any default attribute value definitions for the relation.
 */
static void
AttrDefaultFetch(Relation relation)
{
    AttrDefault *attrdef = relation->rd_att->constr->defval;
    int         ndef = relation->rd_att->constr->num_defval;
    Relation    adrel;
    SysScanDesc adscan;
    ScanKeyData skey;
    HeapTuple   htup;
    Datum       val;
    bool        isnull;
    int         found;
    int         i;

    ScanKeyInit(&skey,
                Anum_pg_attrdef_adrelid,
                BTEqualStrategyNumber, F_OIDEQ,
                ObjectIdGetDatum(RelationGetRelid(relation)));

    adrel = heap_open(AttrDefaultRelationId, AccessShareLock);
    adscan = systable_beginscan(adrel, AttrDefaultIndexId, true,
                                SnapshotNow, 1, &skey);
    found = 0;

    while (HeapTupleIsValid(htup = systable_getnext(adscan)))
    {
        Form_pg_attrdef adform = (Form_pg_attrdef) GETSTRUCT(htup);

        for (i = 0; i < ndef; i++)
        {
            if (adform->adnum != attrdef[i].adnum)
                continue;
            if (attrdef[i].adbin != NULL)
                elog(WARNING, "multiple attrdef records found for attr %s of rel %s",
                NameStr(relation->rd_att->attrs[adform->adnum - 1]->attname),
                     RelationGetRelationName(relation));
            else
                found++;

            val = fastgetattr(htup,
                              Anum_pg_attrdef_adbin,
                              adrel->rd_att, &isnull);
            if (isnull)
                elog(WARNING, "null adbin for attr %s of rel %s",
                NameStr(relation->rd_att->attrs[adform->adnum - 1]->attname),
                     RelationGetRelationName(relation));
            else
                attrdef[i].adbin = MemoryContextStrdup(CacheMemoryContext,
                                                   TextDatumGetCString(val));
            break;
        }

        if (i >= ndef)
            elog(WARNING, "unexpected attrdef record found for attr %d of rel %s",
                 adform->adnum, RelationGetRelationName(relation));
    }

    systable_endscan(adscan);
    heap_close(adrel, AccessShareLock);

    if (found != ndef)
        elog(WARNING, "%d attrdef record(s) missing for rel %s",
             ndef - found, RelationGetRelationName(relation));
}

/*
 * Load any check constraints for the relation.
 */
static void
CheckConstraintFetch(Relation relation)
{
    ConstrCheck *check = relation->rd_att->constr->check;
    int         ncheck = relation->rd_att->constr->num_check;
    Relation    conrel;
    SysScanDesc conscan;
    ScanKeyData skey[1];
    HeapTuple   htup;
    Datum       val;
    bool        isnull;
    int         found = 0;

    ScanKeyInit(&skey[0],
                Anum_pg_constraint_conrelid,
                BTEqualStrategyNumber, F_OIDEQ,
                ObjectIdGetDatum(RelationGetRelid(relation)));

    conrel = heap_open(ConstraintRelationId, AccessShareLock);
    conscan = systable_beginscan(conrel, ConstraintRelidIndexId, true,
                                 SnapshotNow, 1, skey);

    while (HeapTupleIsValid(htup = systable_getnext(conscan)))
    {
        Form_pg_constraint conform = (Form_pg_constraint) GETSTRUCT(htup);

        /* We want check constraints only */
        if (conform->contype != CONSTRAINT_CHECK)
            continue;

        if (found >= ncheck)
            elog(ERROR, "unexpected constraint record found for rel %s",
                 RelationGetRelationName(relation));

        check[found].ccvalid = conform->convalidated;
        check[found].ccnoinherit = conform->connoinherit;
        check[found].ccname = MemoryContextStrdup(CacheMemoryContext,
                                                  NameStr(conform->conname));

        /* Grab and test conbin is actually set */
        val = fastgetattr(htup,
                          Anum_pg_constraint_conbin,
                          conrel->rd_att, &isnull);
        if (isnull)
            elog(ERROR, "null conbin for rel %s",
                 RelationGetRelationName(relation));

        check[found].ccbin = MemoryContextStrdup(CacheMemoryContext,
                                                 TextDatumGetCString(val));
        found++;
    }

    systable_endscan(conscan);
    heap_close(conrel, AccessShareLock);

    if (found != ncheck)
        elog(ERROR, "%d constraint record(s) missing for rel %s",
             ncheck - found, RelationGetRelationName(relation));
}

/*
 * RelationGetIndexList -- get a list of OIDs of indexes on this relation
 *
 * The index list is created only if someone requests it.  We scan pg_index
 * to find relevant indexes, and add the list to the relcache entry so that
 * we won't have to compute it again.  Note that shared cache inval of a
 * relcache entry will delete the old list and set rd_indexvalid to 0,
 * so that we must recompute the index list on next request.  This handles
 * creation or deletion of an index.
 *
 * Indexes that are marked not IndexIsLive are omitted from the returned list.
 * Such indexes are expected to be dropped momentarily, and should not be
 * touched at all by any caller of this function.
 *
 * The returned list is guaranteed to be sorted in order by OID.  This is
 * needed by the executor, since for index types that we obtain exclusive
 * locks on when updating the index, all backends must lock the indexes in
 * the same order or we will get deadlocks (see ExecOpenIndices()).  Any
 * consistent ordering would do, but ordering by OID is easy.
 *
 * Since shared cache inval causes the relcache's copy of the list to go away,
 * we return a copy of the list palloc'd in the caller's context.  The caller
 * may list_free() the returned list after scanning it. This is necessary
 * since the caller will typically be doing syscache lookups on the relevant
 * indexes, and syscache lookup could cause SI messages to be processed!
 *
 * We also update rd_oidindex, which this module treats as effectively part
 * of the index list.  rd_oidindex is valid when rd_indexvalid isn't zero;
 * it is the pg_class OID of a unique index on OID when the relation has one,
 * and InvalidOid if there is no such index.
 */
List *
RelationGetIndexList(Relation relation)
{
    Relation    indrel;
    SysScanDesc indscan;
    ScanKeyData skey;
    HeapTuple   htup;
    List       *result;
    Oid         oidIndex;
    MemoryContext oldcxt;

    /* Quick exit if we already computed the list. */
    if (relation->rd_indexvalid != 0)
        return list_copy(relation->rd_indexlist);

    /*
     * We build the list we intend to return (in the caller's context) while
     * doing the scan.  After successfully completing the scan, we copy that
     * list into the relcache entry.  This avoids cache-context memory leakage
     * if we get some sort of error partway through.
     */
    result = NIL;
    oidIndex = InvalidOid;

    /* Prepare to scan pg_index for entries having indrelid = this rel. */
    ScanKeyInit(&skey,
                Anum_pg_index_indrelid,
                BTEqualStrategyNumber, F_OIDEQ,
                ObjectIdGetDatum(RelationGetRelid(relation)));

    indrel = heap_open(IndexRelationId, AccessShareLock);
    indscan = systable_beginscan(indrel, IndexIndrelidIndexId, true,
                                 SnapshotNow, 1, &skey);

    while (HeapTupleIsValid(htup = systable_getnext(indscan)))
    {
        Form_pg_index index = (Form_pg_index) GETSTRUCT(htup);
        Datum       indclassDatum;
        oidvector  *indclass;
        bool        isnull;

        /*
         * Ignore any indexes that are currently being dropped.  This will
         * prevent them from being searched, inserted into, or considered in
         * HOT-safety decisions.  It's unsafe to touch such an index at all
         * since its catalog entries could disappear at any instant.
         */
        if (!IndexIsLive(index))
            continue;

        /* Add index's OID to result list in the proper order */
        result = insert_ordered_oid(result, index->indexrelid);

        /*
         * indclass cannot be referenced directly through the C struct,
         * because it comes after the variable-width indkey field.  Must
         * extract the datum the hard way...
         */
        indclassDatum = heap_getattr(htup,
                                     Anum_pg_index_indclass,
                                     GetPgIndexDescriptor(),
                                     &isnull);
        Assert(!isnull);
        indclass = (oidvector *) DatumGetPointer(indclassDatum);

        /* Check to see if it is a unique, non-partial btree index on OID */
        if (IndexIsValid(index) &&
            index->indnatts == 1 &&
            index->indisunique && index->indimmediate &&
            index->indkey.values[0] == ObjectIdAttributeNumber &&
            indclass->values[0] == OID_BTREE_OPS_OID &&
            heap_attisnull(htup, Anum_pg_index_indpred))
            oidIndex = index->indexrelid;
    }

    systable_endscan(indscan);
    heap_close(indrel, AccessShareLock);

    /* Now save a copy of the completed list in the relcache entry. */
    oldcxt = MemoryContextSwitchTo(CacheMemoryContext);
    relation->rd_indexlist = list_copy(result);
    relation->rd_oidindex = oidIndex;
    relation->rd_indexvalid = 1;
    MemoryContextSwitchTo(oldcxt);

    return result;
}

/*
 * insert_ordered_oid
 *      Insert a new Oid into a sorted list of Oids, preserving ordering
 *
 * Building the ordered list this way is O(N^2), but with a pretty small
 * constant, so for the number of entries we expect it will probably be
 * faster than trying to apply qsort().  Most tables don't have very many
 * indexes...
 */
static List *
insert_ordered_oid(List *list, Oid datum)
{
    ListCell   *prev;

    /* Does the datum belong at the front? */
    if (list == NIL || datum < linitial_oid(list))
        return lcons_oid(datum, list);
    /* No, so find the entry it belongs after */
    prev = list_head(list);
    for (;;)
    {
        ListCell   *curr = lnext(prev);

        if (curr == NULL || datum < lfirst_oid(curr))
            break;              /* it belongs after 'prev', before 'curr' */

        prev = curr;
    }
    /* Insert datum into list after 'prev' */
    lappend_cell_oid(list, prev, datum);
    return list;
}

/*
 * RelationSetIndexList -- externally force the index list contents
 *
 * This is used to temporarily override what we think the set of valid
 * indexes is (including the presence or absence of an OID index).
 * The forcing will be valid only until transaction commit or abort.
 *
 * This should only be applied to nailed relations, because in a non-nailed
 * relation the hacked index list could be lost at any time due to SI
 * messages.  In practice it is only used on pg_class (see REINDEX).
 *
 * It is up to the caller to make sure the given list is correctly ordered.
 *
 * We deliberately do not change rd_indexattr here: even when operating
 * with a temporary partial index list, HOT-update decisions must be made
 * correctly with respect to the full index set.  It is up to the caller
 * to ensure that a correct rd_indexattr set has been cached before first
 * calling RelationSetIndexList; else a subsequent inquiry might cause a
 * wrong rd_indexattr set to get computed and cached.
 */
void
RelationSetIndexList(Relation relation, List *indexIds, Oid oidIndex)
{
    MemoryContext oldcxt;

    Assert(relation->rd_isnailed);
    /* Copy the list into the cache context (could fail for lack of mem) */
    oldcxt = MemoryContextSwitchTo(CacheMemoryContext);
    indexIds = list_copy(indexIds);
    MemoryContextSwitchTo(oldcxt);
    /* Okay to replace old list */
    list_free(relation->rd_indexlist);
    relation->rd_indexlist = indexIds;
    relation->rd_oidindex = oidIndex;
    relation->rd_indexvalid = 2;    /* mark list as forced */
    /* Flag relation as needing eoxact cleanup (to reset the list) */
    EOXactListAdd(relation);
}

/*
 * RelationGetOidIndex -- get the pg_class OID of the relation's OID index
 *
 * Returns InvalidOid if there is no such index.
 */
Oid
RelationGetOidIndex(Relation relation)
{
    List       *ilist;

    /*
     * If relation doesn't have OIDs at all, caller is probably confused. (We
     * could just silently return InvalidOid, but it seems better to throw an
     * assertion.)
     */
    Assert(relation->rd_rel->relhasoids);

    if (relation->rd_indexvalid == 0)
    {
        /* RelationGetIndexList does the heavy lifting. */
        ilist = RelationGetIndexList(relation);
        list_free(ilist);
        Assert(relation->rd_indexvalid != 0);
    }

    return relation->rd_oidindex;
}

/*
 * RelationGetIndexExpressions -- get the index expressions for an index
 *
 * We cache the result of transforming pg_index.indexprs into a node tree.
 * If the rel is not an index or has no expressional columns, we return NIL.
 * Otherwise, the returned tree is copied into the caller's memory context.
 * (We don't want to return a pointer to the relcache copy, since it could
 * disappear due to relcache invalidation.)
 */
List *
RelationGetIndexExpressions(Relation relation)
{
    List       *result;
    Datum       exprsDatum;
    bool        isnull;
    char       *exprsString;
    MemoryContext oldcxt;

    /* Quick exit if we already computed the result. */
    if (relation->rd_indexprs)
        return (List *) copyObject(relation->rd_indexprs);

    /* Quick exit if there is nothing to do. */
    if (relation->rd_indextuple == NULL ||
        heap_attisnull(relation->rd_indextuple, Anum_pg_index_indexprs))
        return NIL;

    /*
     * We build the tree we intend to return in the caller's context. After
     * successfully completing the work, we copy it into the relcache entry.
     * This avoids problems if we get some sort of error partway through.
     */
    exprsDatum = heap_getattr(relation->rd_indextuple,
                              Anum_pg_index_indexprs,
                              GetPgIndexDescriptor(),
                              &isnull);
    Assert(!isnull);
    exprsString = TextDatumGetCString(exprsDatum);
    result = (List *) stringToNode(exprsString);
    pfree(exprsString);

    /*
     * Run the expressions through eval_const_expressions. This is not just an
     * optimization, but is necessary, because the planner will be comparing
     * them to similarly-processed qual clauses, and may fail to detect valid
     * matches without this.  We don't bother with canonicalize_qual, however.
     */
    result = (List *) eval_const_expressions(NULL, (Node *) result);

    /* May as well fix opfuncids too */
    fix_opfuncids((Node *) result);

    /* Now save a copy of the completed tree in the relcache entry. */
    oldcxt = MemoryContextSwitchTo(relation->rd_indexcxt);
    relation->rd_indexprs = (List *) copyObject(result);
    MemoryContextSwitchTo(oldcxt);

    return result;
}

/*
 * RelationGetIndexPredicate -- get the index predicate for an index
 *
 * We cache the result of transforming pg_index.indpred into an implicit-AND
 * node tree (suitable for ExecQual).
 * If the rel is not an index or has no predicate, we return NIL.
 * Otherwise, the returned tree is copied into the caller's memory context.
 * (We don't want to return a pointer to the relcache copy, since it could
 * disappear due to relcache invalidation.)
 */
List *
RelationGetIndexPredicate(Relation relation)
{
    List       *result;
    Datum       predDatum;
    bool        isnull;
    char       *predString;
    MemoryContext oldcxt;

    /* Quick exit if we already computed the result. */
    if (relation->rd_indpred)
        return (List *) copyObject(relation->rd_indpred);

    /* Quick exit if there is nothing to do. */
    if (relation->rd_indextuple == NULL ||
        heap_attisnull(relation->rd_indextuple, Anum_pg_index_indpred))
        return NIL;

    /*
     * We build the tree we intend to return in the caller's context. After
     * successfully completing the work, we copy it into the relcache entry.
     * This avoids problems if we get some sort of error partway through.
     */
    predDatum = heap_getattr(relation->rd_indextuple,
                             Anum_pg_index_indpred,
                             GetPgIndexDescriptor(),
                             &isnull);
    Assert(!isnull);
    predString = TextDatumGetCString(predDatum);
    result = (List *) stringToNode(predString);
    pfree(predString);

    /*
     * Run the expression through const-simplification and canonicalization.
     * This is not just an optimization, but is necessary, because the planner
     * will be comparing it to similarly-processed qual clauses, and may fail
     * to detect valid matches without this.  This must match the processing
     * done to qual clauses in preprocess_expression()!  (We can skip the
     * stuff involving subqueries, however, since we don't allow any in index
     * predicates.)
     */
    result = (List *) eval_const_expressions(NULL, (Node *) result);

    result = (List *) canonicalize_qual((Expr *) result);

    /* Also convert to implicit-AND format */
    result = make_ands_implicit((Expr *) result);

    /* May as well fix opfuncids too */
    fix_opfuncids((Node *) result);

    /* Now save a copy of the completed tree in the relcache entry. */
    oldcxt = MemoryContextSwitchTo(relation->rd_indexcxt);
    relation->rd_indpred = (List *) copyObject(result);
    MemoryContextSwitchTo(oldcxt);

    return result;
}

/*
 * RelationGetIndexAttrBitmap -- get a bitmap of index attribute numbers
 *
 * The result has a bit set for each attribute used anywhere in the index
 * definitions of all the indexes on this relation.  (This includes not only
 * simple index keys, but attributes used in expressions and partial-index
 * predicates.)
 *
 * If "keyAttrs" is true, only attributes that can be referenced by foreign
 * keys are considered.
 *
 * Attribute numbers are offset by FirstLowInvalidHeapAttributeNumber so that
 * we can include system attributes (e.g., OID) in the bitmap representation.
 *
 * Caller had better hold at least RowExclusiveLock on the target relation
 * to ensure that it has a stable set of indexes.  This also makes it safe
 * (deadlock-free) for us to take locks on the relation's indexes.
 *
 * The returned result is palloc'd in the caller's memory context and should
 * be bms_free'd when not needed anymore.
 */
Bitmapset *
RelationGetIndexAttrBitmap(Relation relation, bool keyAttrs)
{
    Bitmapset  *indexattrs;
    Bitmapset  *uindexattrs;
    List       *indexoidlist;
    ListCell   *l;
    MemoryContext oldcxt;

    /* Quick exit if we already computed the result. */
    if (relation->rd_indexattr != NULL)
        return bms_copy(keyAttrs ? relation->rd_keyattr : relation->rd_indexattr);

    /* Fast path if definitely no indexes */
    if (!RelationGetForm(relation)->relhasindex)
        return NULL;

    /*
     * Get cached list of index OIDs
     */
    indexoidlist = RelationGetIndexList(relation);

    /* Fall out if no indexes (but relhasindex was set) */
    if (indexoidlist == NIL)
        return NULL;

    /*
     * For each index, add referenced attributes to indexattrs.
     *
     * Note: we consider all indexes returned by RelationGetIndexList, even if
     * they are not indisready or indisvalid.  This is important because an
     * index for which CREATE INDEX CONCURRENTLY has just started must be
     * included in HOT-safety decisions (see README.HOT).  If a DROP INDEX
     * CONCURRENTLY is far enough along that we should ignore the index, it
     * won't be returned at all by RelationGetIndexList.
     */
    indexattrs = NULL;
    uindexattrs = NULL;
    foreach(l, indexoidlist)
    {
        Oid         indexOid = lfirst_oid(l);
        Relation    indexDesc;
        IndexInfo  *indexInfo;
        int         i;
        bool        isKey;

        indexDesc = index_open(indexOid, AccessShareLock);

        /* Extract index key information from the index's pg_index row */
        indexInfo = BuildIndexInfo(indexDesc);

        /* Can this index be referenced by a foreign key? */
        isKey = indexInfo->ii_Unique &&
                indexInfo->ii_Expressions == NIL &&
                indexInfo->ii_Predicate == NIL;

        /* Collect simple attribute references */
        for (i = 0; i < indexInfo->ii_NumIndexAttrs; i++)
        {
            int         attrnum = indexInfo->ii_KeyAttrNumbers[i];

            if (attrnum != 0)
            {
                indexattrs = bms_add_member(indexattrs,
                               attrnum - FirstLowInvalidHeapAttributeNumber);
                if (isKey)
                    uindexattrs = bms_add_member(uindexattrs,
                                                 attrnum - FirstLowInvalidHeapAttributeNumber);
            }
        }

        /* Collect all attributes used in expressions, too */
        pull_varattnos((Node *) indexInfo->ii_Expressions, 1, &indexattrs);

        /* Collect all attributes in the index predicate, too */
        pull_varattnos((Node *) indexInfo->ii_Predicate, 1, &indexattrs);

        index_close(indexDesc, AccessShareLock);
    }

    list_free(indexoidlist);

    /* Now save a copy of the bitmap in the relcache entry. */
    oldcxt = MemoryContextSwitchTo(CacheMemoryContext);
    relation->rd_indexattr = bms_copy(indexattrs);
    relation->rd_keyattr = bms_copy(uindexattrs);
    MemoryContextSwitchTo(oldcxt);

    /* We return our original working copy for caller to play with */
    return keyAttrs ? uindexattrs : indexattrs;
}

/*
 * RelationGetExclusionInfo -- get info about index's exclusion constraint
 *
 * This should be called only for an index that is known to have an
 * associated exclusion constraint.  It returns arrays (palloc'd in caller's
 * context) of the exclusion operator OIDs, their underlying functions'
 * OIDs, and their strategy numbers in the index's opclasses.  We cache
 * all this information since it requires a fair amount of work to get.
 */
void
RelationGetExclusionInfo(Relation indexRelation,
                         Oid **operators,
                         Oid **procs,
                         uint16 **strategies)
{
    int         ncols = indexRelation->rd_rel->relnatts;
    Oid        *ops;
    Oid        *funcs;
    uint16     *strats;
    Relation    conrel;
    SysScanDesc conscan;
    ScanKeyData skey[1];
    HeapTuple   htup;
    bool        found;
    MemoryContext oldcxt;
    int         i;

    /* Allocate result space in caller context */
    *operators = ops = (Oid *) palloc(sizeof(Oid) * ncols);
    *procs = funcs = (Oid *) palloc(sizeof(Oid) * ncols);
    *strategies = strats = (uint16 *) palloc(sizeof(uint16) * ncols);

    /* Quick exit if we have the data cached already */
    if (indexRelation->rd_exclstrats != NULL)
    {
        memcpy(ops, indexRelation->rd_exclops, sizeof(Oid) * ncols);
        memcpy(funcs, indexRelation->rd_exclprocs, sizeof(Oid) * ncols);
        memcpy(strats, indexRelation->rd_exclstrats, sizeof(uint16) * ncols);
        return;
    }

    /*
     * Search pg_constraint for the constraint associated with the index. To
     * make this not too painfully slow, we use the index on conrelid; that
     * will hold the parent relation's OID not the index's own OID.
     */
    ScanKeyInit(&skey[0],
                Anum_pg_constraint_conrelid,
                BTEqualStrategyNumber, F_OIDEQ,
                ObjectIdGetDatum(indexRelation->rd_index->indrelid));

    conrel = heap_open(ConstraintRelationId, AccessShareLock);
    conscan = systable_beginscan(conrel, ConstraintRelidIndexId, true,
                                 SnapshotNow, 1, skey);
    found = false;

    while (HeapTupleIsValid(htup = systable_getnext(conscan)))
    {
        Form_pg_constraint conform = (Form_pg_constraint) GETSTRUCT(htup);
        Datum       val;
        bool        isnull;
        ArrayType  *arr;
        int         nelem;

        /* We want the exclusion constraint owning the index */
        if (conform->contype != CONSTRAINT_EXCLUSION ||
            conform->conindid != RelationGetRelid(indexRelation))
            continue;

        /* There should be only one */
        if (found)
            elog(ERROR, "unexpected exclusion constraint record found for rel %s",
                 RelationGetRelationName(indexRelation));
        found = true;

        /* Extract the operator OIDS from conexclop */
        val = fastgetattr(htup,
                          Anum_pg_constraint_conexclop,
                          conrel->rd_att, &isnull);
        if (isnull)
            elog(ERROR, "null conexclop for rel %s",
                 RelationGetRelationName(indexRelation));

        arr = DatumGetArrayTypeP(val);  /* ensure not toasted */
        nelem = ARR_DIMS(arr)[0];
        if (ARR_NDIM(arr) != 1 ||
            nelem != ncols ||
            ARR_HASNULL(arr) ||
            ARR_ELEMTYPE(arr) != OIDOID)
            elog(ERROR, "conexclop is not a 1-D Oid array");

        memcpy(ops, ARR_DATA_PTR(arr), sizeof(Oid) * ncols);
    }

    systable_endscan(conscan);
    heap_close(conrel, AccessShareLock);

    if (!found)
        elog(ERROR, "exclusion constraint record missing for rel %s",
             RelationGetRelationName(indexRelation));

    /* We need the func OIDs and strategy numbers too */
    for (i = 0; i < ncols; i++)
    {
        funcs[i] = get_opcode(ops[i]);
        strats[i] = get_op_opfamily_strategy(ops[i],
                                             indexRelation->rd_opfamily[i]);
        /* shouldn't fail, since it was checked at index creation */
        if (strats[i] == InvalidStrategy)
            elog(ERROR, "could not find strategy for operator %u in family %u",
                 ops[i], indexRelation->rd_opfamily[i]);
    }

    /* Save a copy of the results in the relcache entry. */
    oldcxt = MemoryContextSwitchTo(indexRelation->rd_indexcxt);
    indexRelation->rd_exclops = (Oid *) palloc(sizeof(Oid) * ncols);
    indexRelation->rd_exclprocs = (Oid *) palloc(sizeof(Oid) * ncols);
    indexRelation->rd_exclstrats = (uint16 *) palloc(sizeof(uint16) * ncols);
    memcpy(indexRelation->rd_exclops, ops, sizeof(Oid) * ncols);
    memcpy(indexRelation->rd_exclprocs, funcs, sizeof(Oid) * ncols);
    memcpy(indexRelation->rd_exclstrats, strats, sizeof(uint16) * ncols);
    MemoryContextSwitchTo(oldcxt);
}


/*
 * Routines to support ereport() reports of relation-related errors
 *
 * These could have been put into elog.c, but it seems like a module layering
 * violation to have elog.c calling relcache or syscache stuff --- and we
 * definitely don't want elog.h including rel.h.  So we put them here.
 */

/*
 * errtable --- stores schema_name and table_name of a table
 * within the current errordata.
 */
int
errtable(Relation rel)
{
    err_generic_string(PG_DIAG_SCHEMA_NAME,
                       get_namespace_name(RelationGetNamespace(rel)));
    err_generic_string(PG_DIAG_TABLE_NAME, RelationGetRelationName(rel));

    return 0;           /* return value does not matter */
}

/*
 * errtablecol --- stores schema_name, table_name and column_name
 * of a table column within the current errordata.
 *
 * The column is specified by attribute number --- for most callers, this is
 * easier and less error-prone than getting the column name for themselves.
 */
int
errtablecol(Relation rel, int attnum)
{
    TupleDesc   reldesc = RelationGetDescr(rel);
    const char *colname;

    /* Use reldesc if it's a user attribute, else consult the catalogs */
    if (attnum > 0 && attnum <= reldesc->natts)
        colname = NameStr(reldesc->attrs[attnum - 1]->attname);
    else
        colname = get_relid_attribute_name(RelationGetRelid(rel), attnum);

    return errtablecolname(rel, colname);
}

/*
 * errtablecolname --- stores schema_name, table_name and column_name
 * of a table column within the current errordata, where the column name is
 * given directly rather than extracted from the relation's catalog data.
 *
 * Don't use this directly unless errtablecol() is inconvenient for some
 * reason.  This might possibly be needed during intermediate states in ALTER
 * TABLE, for instance.
 */
int
errtablecolname(Relation rel, const char *colname)
{
    errtable(rel);
    err_generic_string(PG_DIAG_COLUMN_NAME, colname);

    return 0;           /* return value does not matter */
}

/*
 * errtableconstraint --- stores schema_name, table_name and constraint_name
 * of a table-related constraint within the current errordata.
 */
int
errtableconstraint(Relation rel, const char *conname)
{
    errtable(rel);
    err_generic_string(PG_DIAG_CONSTRAINT_NAME, conname);

    return 0;           /* return value does not matter */
}


/*
 *  load_relcache_init_file, write_relcache_init_file
 *
 *      In late 1992, we started regularly having databases with more than
 *      a thousand classes in them.  With this number of classes, it became
 *      critical to do indexed lookups on the system catalogs.
 *
 *      Bootstrapping these lookups is very hard.  We want to be able to
 *      use an index on pg_attribute, for example, but in order to do so,
 *      we must have read pg_attribute for the attributes in the index,
 *      which implies that we need to use the index.
 *
 *      In order to get around the problem, we do the following:
 *
 *         +  When the database system is initialized (at initdb time), we
 *            don't use indexes.  We do sequential scans.
 *
 *         +  When the backend is started up in normal mode, we load an image
 *            of the appropriate relation descriptors, in internal format,
 *            from an initialization file in the data/base/... directory.
 *
 *         +  If the initialization file isn't there, then we create the
 *            relation descriptors using sequential scans and write 'em to
 *            the initialization file for use by subsequent backends.
 *
 *      As of Postgres 9.0, there is one local initialization file in each
 *      database, plus one shared initialization file for shared catalogs.
 *
 *      We could dispense with the initialization files and just build the
 *      critical reldescs the hard way on every backend startup, but that
 *      slows down backend startup noticeably.
 *
 *      We can in fact go further, and save more relcache entries than
 *      just the ones that are absolutely critical; this allows us to speed
 *      up backend startup by not having to build such entries the hard way.
 *      Presently, all the catalog and index entries that are referred to
 *      by catcaches are stored in the initialization files.
 *
 *      The same mechanism that detects when catcache and relcache entries
 *      need to be invalidated (due to catalog updates) also arranges to
 *      unlink the initialization files when the contents may be out of date.
 *      The files will then be rebuilt during the next backend startup.
 */

/*
 * load_relcache_init_file -- attempt to load cache from the shared
 * or local cache init file
 *
 * If successful, return TRUE and set criticalRelcachesBuilt or
 * criticalSharedRelcachesBuilt to true.
 * If not successful, return FALSE.
 *
 * NOTE: we assume we are already switched into CacheMemoryContext.
 */
static bool
load_relcache_init_file(bool shared)
{
    FILE       *fp;
    char        initfilename[MAXPGPATH];
    Relation   *rels;
    int         relno,
                num_rels,
                max_rels,
                nailed_rels,
                nailed_indexes,
                magic;
    int         i;

    if (shared)
        snprintf(initfilename, sizeof(initfilename), "global/%s",
                 RELCACHE_INIT_FILENAME);
    else
        snprintf(initfilename, sizeof(initfilename), "%s/%s",
                 DatabasePath, RELCACHE_INIT_FILENAME);

    fp = AllocateFile(initfilename, PG_BINARY_R);
    if (fp == NULL)
        return false;

    /*
     * Read the index relcache entries from the file.  Note we will not enter
     * any of them into the cache if the read fails partway through; this
     * helps to guard against broken init files.
     */
    max_rels = 100;
    rels = (Relation *) palloc(max_rels * sizeof(Relation));
    num_rels = 0;
    nailed_rels = nailed_indexes = 0;

    /* check for correct magic number (compatible version) */
    if (fread(&magic, 1, sizeof(magic), fp) != sizeof(magic))
        goto read_failed;
    if (magic != RELCACHE_INIT_FILEMAGIC)
        goto read_failed;

    for (relno = 0;; relno++)
    {
        Size        len;
        size_t      nread;
        Relation    rel;
        Form_pg_class relform;
        bool        has_not_null;

        /* first read the relation descriptor length */
        nread = fread(&len, 1, sizeof(len), fp);
        if (nread != sizeof(len))
        {
            if (nread == 0)
                break;          /* end of file */
            goto read_failed;
        }

        /* safety check for incompatible relcache layout */
        if (len != sizeof(RelationData))
            goto read_failed;

        /* allocate another relcache header */
        if (num_rels >= max_rels)
        {
            max_rels *= 2;
            rels = (Relation *) repalloc(rels, max_rels * sizeof(Relation));
        }

        rel = rels[num_rels++] = (Relation) palloc(len);

        /* then, read the Relation structure */
        if (fread(rel, 1, len, fp) != len)
            goto read_failed;

        /* next read the relation tuple form */
        if (fread(&len, 1, sizeof(len), fp) != sizeof(len))
            goto read_failed;

        relform = (Form_pg_class) palloc(len);
        if (fread(relform, 1, len, fp) != len)
            goto read_failed;

        rel->rd_rel = relform;

        /* initialize attribute tuple forms */
        rel->rd_att = CreateTemplateTupleDesc(relform->relnatts,
                                              relform->relhasoids);
        rel->rd_att->tdrefcount = 1;    /* mark as refcounted */

        rel->rd_att->tdtypeid = relform->reltype;
        rel->rd_att->tdtypmod = -1;     /* unnecessary, but... */

        /* next read all the attribute tuple form data entries */
        has_not_null = false;
        for (i = 0; i < relform->relnatts; i++)
        {
            if (fread(&len, 1, sizeof(len), fp) != sizeof(len))
                goto read_failed;
            if (len != ATTRIBUTE_FIXED_PART_SIZE)
                goto read_failed;
            if (fread(rel->rd_att->attrs[i], 1, len, fp) != len)
                goto read_failed;

            has_not_null |= rel->rd_att->attrs[i]->attnotnull;
        }

        /* next read the access method specific field */
        if (fread(&len, 1, sizeof(len), fp) != sizeof(len))
            goto read_failed;
        if (len > 0)
        {
            rel->rd_options = palloc(len);
            if (fread(rel->rd_options, 1, len, fp) != len)
                goto read_failed;
            if (len != VARSIZE(rel->rd_options))
                goto read_failed;       /* sanity check */
        }
        else
        {
            rel->rd_options = NULL;
        }

        /* mark not-null status */
        if (has_not_null)
        {
            TupleConstr *constr = (TupleConstr *) palloc0(sizeof(TupleConstr));

            constr->has_not_null = true;
            rel->rd_att->constr = constr;
        }

        /* If it's an index, there's more to do */
        if (rel->rd_rel->relkind == RELKIND_INDEX)
        {
            Form_pg_am  am;
            MemoryContext indexcxt;
            Oid        *opfamily;
            Oid        *opcintype;
            RegProcedure *support;
            int         nsupport;
            int16      *indoption;
            Oid        *indcollation;

            /* Count nailed indexes to ensure we have 'em all */
            if (rel->rd_isnailed)
                nailed_indexes++;

            /* next, read the pg_index tuple */
            if (fread(&len, 1, sizeof(len), fp) != sizeof(len))
                goto read_failed;

            rel->rd_indextuple = (HeapTuple) palloc(len);
            if (fread(rel->rd_indextuple, 1, len, fp) != len)
                goto read_failed;

            /* Fix up internal pointers in the tuple -- see heap_copytuple */
            rel->rd_indextuple->t_data = (HeapTupleHeader) ((char *) rel->rd_indextuple + HEAPTUPLESIZE);
            rel->rd_index = (Form_pg_index) GETSTRUCT(rel->rd_indextuple);

            /* next, read the access method tuple form */
            if (fread(&len, 1, sizeof(len), fp) != sizeof(len))
                goto read_failed;

            am = (Form_pg_am) palloc(len);
            if (fread(am, 1, len, fp) != len)
                goto read_failed;
            rel->rd_am = am;

            /*
             * prepare index info context --- parameters should match
             * RelationInitIndexAccessInfo
             */
            indexcxt = AllocSetContextCreate(CacheMemoryContext,
                                             RelationGetRelationName(rel),
                                             ALLOCSET_SMALL_MINSIZE,
                                             ALLOCSET_SMALL_INITSIZE,
                                             ALLOCSET_SMALL_MAXSIZE);
            rel->rd_indexcxt = indexcxt;

            /* next, read the vector of opfamily OIDs */
            if (fread(&len, 1, sizeof(len), fp) != sizeof(len))
                goto read_failed;

            opfamily = (Oid *) MemoryContextAlloc(indexcxt, len);
            if (fread(opfamily, 1, len, fp) != len)
                goto read_failed;

            rel->rd_opfamily = opfamily;

            /* next, read the vector of opcintype OIDs */
            if (fread(&len, 1, sizeof(len), fp) != sizeof(len))
                goto read_failed;

            opcintype = (Oid *) MemoryContextAlloc(indexcxt, len);
            if (fread(opcintype, 1, len, fp) != len)
                goto read_failed;

            rel->rd_opcintype = opcintype;

            /* next, read the vector of support procedure OIDs */
            if (fread(&len, 1, sizeof(len), fp) != sizeof(len))
                goto read_failed;
            support = (RegProcedure *) MemoryContextAlloc(indexcxt, len);
            if (fread(support, 1, len, fp) != len)
                goto read_failed;

            rel->rd_support = support;

            /* next, read the vector of collation OIDs */
            if (fread(&len, 1, sizeof(len), fp) != sizeof(len))
                goto read_failed;

            indcollation = (Oid *) MemoryContextAlloc(indexcxt, len);
            if (fread(indcollation, 1, len, fp) != len)
                goto read_failed;

            rel->rd_indcollation = indcollation;

            /* finally, read the vector of indoption values */
            if (fread(&len, 1, sizeof(len), fp) != sizeof(len))
                goto read_failed;

            indoption = (int16 *) MemoryContextAlloc(indexcxt, len);
            if (fread(indoption, 1, len, fp) != len)
                goto read_failed;

            rel->rd_indoption = indoption;

            /* set up zeroed fmgr-info vectors */
            rel->rd_aminfo = (RelationAmInfo *)
                MemoryContextAllocZero(indexcxt, sizeof(RelationAmInfo));
            nsupport = relform->relnatts * am->amsupport;
            rel->rd_supportinfo = (FmgrInfo *)
                MemoryContextAllocZero(indexcxt, nsupport * sizeof(FmgrInfo));
        }
        else
        {
            /* Count nailed rels to ensure we have 'em all */
            if (rel->rd_isnailed)
                nailed_rels++;

            Assert(rel->rd_index == NULL);
            Assert(rel->rd_indextuple == NULL);
            Assert(rel->rd_am == NULL);
            Assert(rel->rd_indexcxt == NULL);
            Assert(rel->rd_aminfo == NULL);
            Assert(rel->rd_opfamily == NULL);
            Assert(rel->rd_opcintype == NULL);
            Assert(rel->rd_support == NULL);
            Assert(rel->rd_supportinfo == NULL);
            Assert(rel->rd_indoption == NULL);
            Assert(rel->rd_indcollation == NULL);
        }

        /*
         * Rules and triggers are not saved (mainly because the internal
         * format is complex and subject to change).  They must be rebuilt if
         * needed by RelationCacheInitializePhase3.  This is not expected to
         * be a big performance hit since few system catalogs have such. Ditto
         * for index expressions, predicates, exclusion info, and FDW info.
         */
        rel->rd_rules = NULL;
        rel->rd_rulescxt = NULL;
        rel->trigdesc = NULL;
        rel->rd_indexprs = NIL;
        rel->rd_indpred = NIL;
        rel->rd_exclops = NULL;
        rel->rd_exclprocs = NULL;
        rel->rd_exclstrats = NULL;
        rel->rd_fdwroutine = NULL;

        /*
         * Reset transient-state fields in the relcache entry
         */
        rel->rd_smgr = NULL;
        if (rel->rd_isnailed)
            rel->rd_refcnt = 1;
        else
            rel->rd_refcnt = 0;
        rel->rd_indexvalid = 0;
        rel->rd_indexlist = NIL;
        rel->rd_indexattr = NULL;
        rel->rd_oidindex = InvalidOid;
        rel->rd_createSubid = InvalidSubTransactionId;
        rel->rd_newRelfilenodeSubid = InvalidSubTransactionId;
        rel->rd_amcache = NULL;
        MemSet(&rel->pgstat_info, 0, sizeof(rel->pgstat_info));

        /*
         * Recompute lock and physical addressing info.  This is needed in
         * case the pg_internal.init file was copied from some other database
         * by CREATE DATABASE.
         */
        RelationInitLockInfo(rel);
        RelationInitPhysicalAddr(rel);
        if (rel->rd_rel->relkind == RELKIND_MATVIEW &&
            heap_is_matview_init_state(rel))
            rel->rd_ispopulated = false;
        else
            rel->rd_ispopulated = true;
    }

    /*
     * We reached the end of the init file without apparent problem. Did we
     * get the right number of nailed items?  (This is a useful crosscheck in
     * case the set of critical rels or indexes changes.)
     */
    if (shared)
    {
        if (nailed_rels != NUM_CRITICAL_SHARED_RELS ||
            nailed_indexes != NUM_CRITICAL_SHARED_INDEXES)
            goto read_failed;
    }
    else
    {
        if (nailed_rels != NUM_CRITICAL_LOCAL_RELS ||
            nailed_indexes != NUM_CRITICAL_LOCAL_INDEXES)
            goto read_failed;
    }

    /*
     * OK, all appears well.
     *
     * Now insert all the new relcache entries into the cache.
     */
    for (relno = 0; relno < num_rels; relno++)
    {
        RelationCacheInsert(rels[relno]);
        /* also make a list of their OIDs, for RelationIdIsInInitFile */
        if (!shared)
            initFileRelationIds = lcons_oid(RelationGetRelid(rels[relno]),
                                            initFileRelationIds);
    }

    pfree(rels);
    FreeFile(fp);

    if (shared)
        criticalSharedRelcachesBuilt = true;
    else
        criticalRelcachesBuilt = true;
    return true;

    /*
     * init file is broken, so do it the hard way.  We don't bother trying to
     * free the clutter we just allocated; it's not in the relcache so it
     * won't hurt.
     */
read_failed:
    pfree(rels);
    FreeFile(fp);

    return false;
}

/*
 * Write out a new initialization file with the current contents
 * of the relcache (either shared rels or local rels, as indicated).
 */
static void
write_relcache_init_file(bool shared)
{
    FILE       *fp;
    char        tempfilename[MAXPGPATH];
    char        finalfilename[MAXPGPATH];
    int         magic;
    HASH_SEQ_STATUS status;
    RelIdCacheEnt *idhentry;
    MemoryContext oldcxt;
    int         i;

    /*
     * We must write a temporary file and rename it into place. Otherwise,
     * another backend starting at about the same time might crash trying to
     * read the partially-complete file.
     */
    if (shared)
    {
        snprintf(tempfilename, sizeof(tempfilename), "global/%s.%d",
                 RELCACHE_INIT_FILENAME, MyProcPid);
        snprintf(finalfilename, sizeof(finalfilename), "global/%s",
                 RELCACHE_INIT_FILENAME);
    }
    else
    {
        snprintf(tempfilename, sizeof(tempfilename), "%s/%s.%d",
                 DatabasePath, RELCACHE_INIT_FILENAME, MyProcPid);
        snprintf(finalfilename, sizeof(finalfilename), "%s/%s",
                 DatabasePath, RELCACHE_INIT_FILENAME);
    }

    unlink(tempfilename);       /* in case it exists w/wrong permissions */

    fp = AllocateFile(tempfilename, PG_BINARY_W);
    if (fp == NULL)
    {
        /*
         * We used to consider this a fatal error, but we might as well
         * continue with backend startup ...
         */
        ereport(WARNING,
                (errcode_for_file_access(),
                 errmsg("could not create relation-cache initialization file \"%s\": %m",
                        tempfilename),
              errdetail("Continuing anyway, but there's something wrong.")));
        return;
    }

    /*
     * Write a magic number to serve as a file version identifier.  We can
     * change the magic number whenever the relcache layout changes.
     */
    magic = RELCACHE_INIT_FILEMAGIC;
    if (fwrite(&magic, 1, sizeof(magic), fp) != sizeof(magic))
        elog(FATAL, "could not write init file");

    /*
     * Write all the appropriate reldescs (in no particular order).
     */
    hash_seq_init(&status, RelationIdCache);

    while ((idhentry = (RelIdCacheEnt *) hash_seq_search(&status)) != NULL)
    {
        Relation    rel = idhentry->reldesc;
        Form_pg_class relform = rel->rd_rel;

        /* ignore if not correct group */
        if (relform->relisshared != shared)
            continue;

        /* first write the relcache entry proper */
        write_item(rel, sizeof(RelationData), fp);

        /* next write the relation tuple form */
        write_item(relform, CLASS_TUPLE_SIZE, fp);

        /* next, do all the attribute tuple form data entries */
        for (i = 0; i < relform->relnatts; i++)
        {
            write_item(rel->rd_att->attrs[i], ATTRIBUTE_FIXED_PART_SIZE, fp);
        }

        /* next, do the access method specific field */
        write_item(rel->rd_options,
                   (rel->rd_options ? VARSIZE(rel->rd_options) : 0),
                   fp);

        /* If it's an index, there's more to do */
        if (rel->rd_rel->relkind == RELKIND_INDEX)
        {
            Form_pg_am  am = rel->rd_am;

            /* write the pg_index tuple */
            /* we assume this was created by heap_copytuple! */
            write_item(rel->rd_indextuple,
                       HEAPTUPLESIZE + rel->rd_indextuple->t_len,
                       fp);

            /* next, write the access method tuple form */
            write_item(am, sizeof(FormData_pg_am), fp);

            /* next, write the vector of opfamily OIDs */
            write_item(rel->rd_opfamily,
                       relform->relnatts * sizeof(Oid),
                       fp);

            /* next, write the vector of opcintype OIDs */
            write_item(rel->rd_opcintype,
                       relform->relnatts * sizeof(Oid),
                       fp);

            /* next, write the vector of support procedure OIDs */
            write_item(rel->rd_support,
                  relform->relnatts * (am->amsupport * sizeof(RegProcedure)),
                       fp);

            /* next, write the vector of collation OIDs */
            write_item(rel->rd_indcollation,
                       relform->relnatts * sizeof(Oid),
                       fp);

            /* finally, write the vector of indoption values */
            write_item(rel->rd_indoption,
                       relform->relnatts * sizeof(int16),
                       fp);
        }

        /* also make a list of their OIDs, for RelationIdIsInInitFile */
        if (!shared)
        {
            oldcxt = MemoryContextSwitchTo(CacheMemoryContext);
            initFileRelationIds = lcons_oid(RelationGetRelid(rel),
                                            initFileRelationIds);
            MemoryContextSwitchTo(oldcxt);
        }
    }

    if (FreeFile(fp))
        elog(FATAL, "could not write init file");

    /*
     * Now we have to check whether the data we've so painstakingly
     * accumulated is already obsolete due to someone else's just-committed
     * catalog changes.  If so, we just delete the temp file and leave it to
     * the next backend to try again.  (Our own relcache entries will be
     * updated by SI message processing, but we can't be sure whether what we
     * wrote out was up-to-date.)
     *
     * This mustn't run concurrently with the code that unlinks an init file
     * and sends SI messages, so grab a serialization lock for the duration.
     */
    LWLockAcquire(RelCacheInitLock, LW_EXCLUSIVE);

    /* Make sure we have seen all incoming SI messages */
    AcceptInvalidationMessages();

    /*
     * If we have received any SI relcache invals since backend start, assume
     * we may have written out-of-date data.
     */
    if (relcacheInvalsReceived == 0L)
    {
        /*
         * OK, rename the temp file to its final name, deleting any
         * previously-existing init file.
         *
         * Note: a failure here is possible under Cygwin, if some other
         * backend is holding open an unlinked-but-not-yet-gone init file. So
         * treat this as a noncritical failure; just remove the useless temp
         * file on failure.
         */
        if (rename(tempfilename, finalfilename) < 0)
            unlink(tempfilename);
    }
    else
    {
        /* Delete the already-obsolete temp file */
        unlink(tempfilename);
    }

    LWLockRelease(RelCacheInitLock);
}

/* write a chunk of data preceded by its length */
static void
write_item(const void *data, Size len, FILE *fp)
{
    if (fwrite(&len, 1, sizeof(len), fp) != sizeof(len))
        elog(FATAL, "could not write init file");
    if (fwrite(data, 1, len, fp) != len)
        elog(FATAL, "could not write init file");
}

/*
 * Detect whether a given relation (identified by OID) is one of the ones
 * we store in the local relcache init file.
 *
 * Note that we effectively assume that all backends running in a database
 * would choose to store the same set of relations in the init file;
 * otherwise there are cases where we'd fail to detect the need for an init
 * file invalidation.  This does not seem likely to be a problem in practice.
 */
bool
RelationIdIsInInitFile(Oid relationId)
{
    return list_member_oid(initFileRelationIds, relationId);
}

/*
 * Invalidate (remove) the init file during commit of a transaction that
 * changed one or more of the relation cache entries that are kept in the
 * local init file.
 *
 * To be safe against concurrent inspection or rewriting of the init file,
 * we must take RelCacheInitLock, then remove the old init file, then send
 * the SI messages that include relcache inval for such relations, and then
 * release RelCacheInitLock.  This serializes the whole affair against
 * write_relcache_init_file, so that we can be sure that any other process
 * that's concurrently trying to create a new init file won't move an
 * already-stale version into place after we unlink.  Also, because we unlink
 * before sending the SI messages, a backend that's currently starting cannot
 * read the now-obsolete init file and then miss the SI messages that will
 * force it to update its relcache entries.  (This works because the backend
 * startup sequence gets into the sinval array before trying to load the init
 * file.)
 *
 * We take the lock and do the unlink in RelationCacheInitFilePreInvalidate,
 * then release the lock in RelationCacheInitFilePostInvalidate.  Caller must
 * send any pending SI messages between those calls.
 *
 * Notice this deals only with the local init file, not the shared init file.
 * The reason is that there can never be a "significant" change to the
 * relcache entry of a shared relation; the most that could happen is
 * updates of noncritical fields such as relpages/reltuples.  So, while
 * it's worth updating the shared init file from time to time, it can never
 * be invalid enough to make it necessary to remove it.
 */
void
RelationCacheInitFilePreInvalidate(void)
{
    char        initfilename[MAXPGPATH];

    snprintf(initfilename, sizeof(initfilename), "%s/%s",
             DatabasePath, RELCACHE_INIT_FILENAME);

    LWLockAcquire(RelCacheInitLock, LW_EXCLUSIVE);

    if (unlink(initfilename) < 0)
    {
        /*
         * The file might not be there if no backend has been started since
         * the last removal.  But complain about failures other than ENOENT.
         * Fortunately, it's not too late to abort the transaction if we can't
         * get rid of the would-be-obsolete init file.
         */
        if (errno != ENOENT)
            ereport(ERROR,
                    (errcode_for_file_access(),
                     errmsg("could not remove cache file \"%s\": %m",
                            initfilename)));
    }
}

void
RelationCacheInitFilePostInvalidate(void)
{
    LWLockRelease(RelCacheInitLock);
}

/*
 * Remove the init files during postmaster startup.
 *
 * We used to keep the init files across restarts, but that is unsafe in PITR
 * scenarios, and even in simple crash-recovery cases there are windows for
 * the init files to become out-of-sync with the database.  So now we just
 * remove them during startup and expect the first backend launch to rebuild
 * them.  Of course, this has to happen in each database of the cluster.
 */
void
RelationCacheInitFileRemove(void)
{
    const char *tblspcdir = "pg_tblspc";
    DIR        *dir;
    struct dirent *de;
    char        path[MAXPGPATH];

    /*
     * We zap the shared cache file too.  In theory it can't get out of sync
     * enough to be a problem, but in data-corruption cases, who knows ...
     */
    snprintf(path, sizeof(path), "global/%s",
             RELCACHE_INIT_FILENAME);
    unlink_initfile(path);

    /* Scan everything in the default tablespace */
    RelationCacheInitFileRemoveInDir("base");

    /* Scan the tablespace link directory to find non-default tablespaces */
    dir = AllocateDir(tblspcdir);
    if (dir == NULL)
    {
        elog(LOG, "could not open tablespace link directory \"%s\": %m",
             tblspcdir);
        return;
    }

    while ((de = ReadDir(dir, tblspcdir)) != NULL)
    {
        if (strspn(de->d_name, "0123456789") == strlen(de->d_name))
        {
            /* Scan the tablespace dir for per-database dirs */
            snprintf(path, sizeof(path), "%s/%s/%s",
                     tblspcdir, de->d_name, TABLESPACE_VERSION_DIRECTORY);
            RelationCacheInitFileRemoveInDir(path);
        }
    }

    FreeDir(dir);
}

/* Process one per-tablespace directory for RelationCacheInitFileRemove */
static void
RelationCacheInitFileRemoveInDir(const char *tblspcpath)
{
    DIR        *dir;
    struct dirent *de;
    char        initfilename[MAXPGPATH];

    /* Scan the tablespace directory to find per-database directories */
    dir = AllocateDir(tblspcpath);
    if (dir == NULL)
    {
        elog(LOG, "could not open tablespace directory \"%s\": %m",
             tblspcpath);
        return;
    }

    while ((de = ReadDir(dir, tblspcpath)) != NULL)
    {
        if (strspn(de->d_name, "0123456789") == strlen(de->d_name))
        {
            /* Try to remove the init file in each database */
            snprintf(initfilename, sizeof(initfilename), "%s/%s/%s",
                     tblspcpath, de->d_name, RELCACHE_INIT_FILENAME);
            unlink_initfile(initfilename);
        }
    }

    FreeDir(dir);
}

static void
unlink_initfile(const char *initfilename)
{
    if (unlink(initfilename) < 0)
    {
        /* It might not be there, but log any error other than ENOENT */
        if (errno != ENOENT)
            elog(LOG, "could not remove cache file \"%s\": %m", initfilename);
    }
}