typcache.c

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/*-------------------------------------------------------------------------
 *
 * typcache.c
 *    POSTGRES type cache code
 *
 * The type cache exists to speed lookup of certain information about data
 * types that is not directly available from a type's pg_type row.  For
 * example, we use a type's default btree opclass, or the default hash
 * opclass if no btree opclass exists, to determine which operators should
 * be used for grouping and sorting the type (GROUP BY, ORDER BY ASC/DESC).
 *
 * Several seemingly-odd choices have been made to support use of the type
 * cache by generic array and record handling routines, such as array_eq(),
 * record_cmp(), and hash_array().  Because those routines are used as index
 * support operations, they cannot leak memory.  To allow them to execute
 * efficiently, all information that they would like to re-use across calls
 * is kept in the type cache.
 *
 * Once created, a type cache entry lives as long as the backend does, so
 * there is no need for a call to release a cache entry.  (For present uses,
 * it would be okay to flush type cache entries at the ends of transactions,
 * if we needed to reclaim space.)
 *
 * There is presently no provision for clearing out a cache entry if the
 * stored data becomes obsolete.  (The code will work if a type acquires
 * opclasses it didn't have before while a backend runs --- but not if the
 * definition of an existing opclass is altered.)  However, the relcache
 * doesn't cope with opclasses changing under it, either, so this seems
 * a low-priority problem.
 *
 * We do support clearing the tuple descriptor and operator/function parts
 * of a rowtype's cache entry, since those may need to change as a consequence
 * of ALTER TABLE.
 *
 *
 * Portions Copyright (c) 1996-2013, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 * IDENTIFICATION
 *    src/backend/utils/cache/typcache.c
 *
 *-------------------------------------------------------------------------
 */
#include "postgres.h"

#include <limits.h>

#include "access/hash.h"
#include "access/heapam.h"
#include "access/htup_details.h"
#include "access/nbtree.h"
#include "catalog/indexing.h"
#include "catalog/pg_enum.h"
#include "catalog/pg_operator.h"
#include "catalog/pg_range.h"
#include "catalog/pg_type.h"
#include "commands/defrem.h"
#include "utils/builtins.h"
#include "utils/catcache.h"
#include "utils/fmgroids.h"
#include "utils/inval.h"
#include "utils/lsyscache.h"
#include "utils/rel.h"
#include "utils/snapmgr.h"
#include "utils/syscache.h"
#include "utils/typcache.h"


/* The main type cache hashtable searched by lookup_type_cache */
static HTAB *TypeCacheHash = NULL;

/* Private flag bits in the TypeCacheEntry.flags field */
#define TCFLAGS_CHECKED_ELEM_PROPERTIES     0x0001
#define TCFLAGS_HAVE_ELEM_EQUALITY          0x0002
#define TCFLAGS_HAVE_ELEM_COMPARE           0x0004
#define TCFLAGS_HAVE_ELEM_HASHING           0x0008
#define TCFLAGS_CHECKED_FIELD_PROPERTIES    0x0010
#define TCFLAGS_HAVE_FIELD_EQUALITY         0x0020
#define TCFLAGS_HAVE_FIELD_COMPARE          0x0040

/* Private information to support comparisons of enum values */
typedef struct
{
    Oid         enum_oid;       /* OID of one enum value */
    float4      sort_order;     /* its sort position */
} EnumItem;

typedef struct TypeCacheEnumData
{
    Oid         bitmap_base;    /* OID corresponding to bit 0 of bitmapset */
    Bitmapset  *sorted_values;  /* Set of OIDs known to be in order */
    int         num_values;     /* total number of values in enum */
    EnumItem    enum_values[1]; /* VARIABLE LENGTH ARRAY */
} TypeCacheEnumData;

/*
 * We use a separate table for storing the definitions of non-anonymous
 * record types.  Once defined, a record type will be remembered for the
 * life of the backend.  Subsequent uses of the "same" record type (where
 * sameness means equalTupleDescs) will refer to the existing table entry.
 *
 * Stored record types are remembered in a linear array of TupleDescs,
 * which can be indexed quickly with the assigned typmod.  There is also
 * a hash table to speed searches for matching TupleDescs.  The hash key
 * uses just the first N columns' type OIDs, and so we may have multiple
 * entries with the same hash key.
 */
#define REC_HASH_KEYS   16      /* use this many columns in hash key */

typedef struct RecordCacheEntry
{
    /* the hash lookup key MUST BE FIRST */
    Oid         hashkey[REC_HASH_KEYS]; /* column type IDs, zero-filled */

    /* list of TupleDescs for record types with this hashkey */
    List       *tupdescs;
} RecordCacheEntry;

static HTAB *RecordCacheHash = NULL;

static TupleDesc *RecordCacheArray = NULL;
static int32 RecordCacheArrayLen = 0;   /* allocated length of array */
static int32 NextRecordTypmod = 0;      /* number of entries used */

static void load_typcache_tupdesc(TypeCacheEntry *typentry);
static void load_rangetype_info(TypeCacheEntry *typentry);
static bool array_element_has_equality(TypeCacheEntry *typentry);
static bool array_element_has_compare(TypeCacheEntry *typentry);
static bool array_element_has_hashing(TypeCacheEntry *typentry);
static void cache_array_element_properties(TypeCacheEntry *typentry);
static bool record_fields_have_equality(TypeCacheEntry *typentry);
static bool record_fields_have_compare(TypeCacheEntry *typentry);
static void cache_record_field_properties(TypeCacheEntry *typentry);
static void TypeCacheRelCallback(Datum arg, Oid relid);
static void load_enum_cache_data(TypeCacheEntry *tcache);
static EnumItem *find_enumitem(TypeCacheEnumData *enumdata, Oid arg);
static int  enum_oid_cmp(const void *left, const void *right);


/*
 * lookup_type_cache
 *
 * Fetch the type cache entry for the specified datatype, and make sure that
 * all the fields requested by bits in 'flags' are valid.
 *
 * The result is never NULL --- we will elog() if the passed type OID is
 * invalid.  Note however that we may fail to find one or more of the
 * requested opclass-dependent fields; the caller needs to check whether
 * the fields are InvalidOid or not.
 */
TypeCacheEntry *
lookup_type_cache(Oid type_id, int flags)
{
    TypeCacheEntry *typentry;
    bool        found;

    if (TypeCacheHash == NULL)
    {
        /* First time through: initialize the hash table */
        HASHCTL     ctl;

        MemSet(&ctl, 0, sizeof(ctl));
        ctl.keysize = sizeof(Oid);
        ctl.entrysize = sizeof(TypeCacheEntry);
        ctl.hash = oid_hash;
        TypeCacheHash = hash_create("Type information cache", 64,
                                    &ctl, HASH_ELEM | HASH_FUNCTION);

        /* Also set up a callback for relcache SI invalidations */
        CacheRegisterRelcacheCallback(TypeCacheRelCallback, (Datum) 0);

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

    /* Try to look up an existing entry */
    typentry = (TypeCacheEntry *) hash_search(TypeCacheHash,
                                              (void *) &type_id,
                                              HASH_FIND, NULL);
    if (typentry == NULL)
    {
        /*
         * If we didn't find one, we want to make one.  But first look up the
         * pg_type row, just to make sure we don't make a cache entry for an
         * invalid type OID.
         */
        HeapTuple   tp;
        Form_pg_type typtup;

        tp = SearchSysCache1(TYPEOID, ObjectIdGetDatum(type_id));
        if (!HeapTupleIsValid(tp))
            elog(ERROR, "cache lookup failed for type %u", type_id);
        typtup = (Form_pg_type) GETSTRUCT(tp);
        if (!typtup->typisdefined)
            ereport(ERROR,
                    (errcode(ERRCODE_UNDEFINED_OBJECT),
                     errmsg("type \"%s\" is only a shell",
                            NameStr(typtup->typname))));

        /* Now make the typcache entry */
        typentry = (TypeCacheEntry *) hash_search(TypeCacheHash,
                                                  (void *) &type_id,
                                                  HASH_ENTER, &found);
        Assert(!found);         /* it wasn't there a moment ago */

        MemSet(typentry, 0, sizeof(TypeCacheEntry));
        typentry->type_id = type_id;
        typentry->typlen = typtup->typlen;
        typentry->typbyval = typtup->typbyval;
        typentry->typalign = typtup->typalign;
        typentry->typstorage = typtup->typstorage;
        typentry->typtype = typtup->typtype;
        typentry->typrelid = typtup->typrelid;

        ReleaseSysCache(tp);
    }

    /*
     * If we haven't already found the opclasses, try to do so
     */
    if ((flags & (TYPECACHE_EQ_OPR | TYPECACHE_LT_OPR | TYPECACHE_GT_OPR |
                  TYPECACHE_CMP_PROC |
                  TYPECACHE_EQ_OPR_FINFO | TYPECACHE_CMP_PROC_FINFO |
                  TYPECACHE_BTREE_OPFAMILY)) &&
        typentry->btree_opf == InvalidOid)
    {
        Oid         opclass;

        opclass = GetDefaultOpClass(type_id, BTREE_AM_OID);
        if (OidIsValid(opclass))
        {
            typentry->btree_opf = get_opclass_family(opclass);
            typentry->btree_opintype = get_opclass_input_type(opclass);
        }
        /* If no btree opclass, we force lookup of the hash opclass */
        if (typentry->btree_opf == InvalidOid)
        {
            if (typentry->hash_opf == InvalidOid)
            {
                opclass = GetDefaultOpClass(type_id, HASH_AM_OID);
                if (OidIsValid(opclass))
                {
                    typentry->hash_opf = get_opclass_family(opclass);
                    typentry->hash_opintype = get_opclass_input_type(opclass);
                }
            }
        }
        else
        {
            /*
             * In case we find a btree opclass where previously we only found
             * a hash opclass, reset eq_opr and derived information so that we
             * can fetch the btree equality operator instead of the hash
             * equality operator.  (They're probably the same operator, but we
             * don't assume that here.)
             */
            typentry->eq_opr = InvalidOid;
            typentry->eq_opr_finfo.fn_oid = InvalidOid;
            typentry->hash_proc = InvalidOid;
            typentry->hash_proc_finfo.fn_oid = InvalidOid;
        }
    }

    if ((flags & (TYPECACHE_HASH_PROC | TYPECACHE_HASH_PROC_FINFO |
                  TYPECACHE_HASH_OPFAMILY)) &&
        typentry->hash_opf == InvalidOid)
    {
        Oid         opclass;

        opclass = GetDefaultOpClass(type_id, HASH_AM_OID);
        if (OidIsValid(opclass))
        {
            typentry->hash_opf = get_opclass_family(opclass);
            typentry->hash_opintype = get_opclass_input_type(opclass);
        }
    }

    /* Look for requested operators and functions */
    if ((flags & (TYPECACHE_EQ_OPR | TYPECACHE_EQ_OPR_FINFO)) &&
        typentry->eq_opr == InvalidOid)
    {
        Oid         eq_opr = InvalidOid;

        if (typentry->btree_opf != InvalidOid)
            eq_opr = get_opfamily_member(typentry->btree_opf,
                                         typentry->btree_opintype,
                                         typentry->btree_opintype,
                                         BTEqualStrategyNumber);
        if (eq_opr == InvalidOid &&
            typentry->hash_opf != InvalidOid)
            eq_opr = get_opfamily_member(typentry->hash_opf,
                                         typentry->hash_opintype,
                                         typentry->hash_opintype,
                                         HTEqualStrategyNumber);

        /*
         * If the proposed equality operator is array_eq or record_eq, check
         * to see if the element type or column types support equality. If
         * not, array_eq or record_eq would fail at runtime, so we don't want
         * to report that the type has equality.
         */
        if (eq_opr == ARRAY_EQ_OP &&
            !array_element_has_equality(typentry))
            eq_opr = InvalidOid;
        else if (eq_opr == RECORD_EQ_OP &&
                 !record_fields_have_equality(typentry))
            eq_opr = InvalidOid;

        typentry->eq_opr = eq_opr;

        /*
         * Reset info about hash function whenever we pick up new info about
         * equality operator.  This is so we can ensure that the hash function
         * matches the operator.
         */
        typentry->hash_proc = InvalidOid;
        typentry->hash_proc_finfo.fn_oid = InvalidOid;
    }
    if ((flags & TYPECACHE_LT_OPR) && typentry->lt_opr == InvalidOid)
    {
        Oid         lt_opr = InvalidOid;

        if (typentry->btree_opf != InvalidOid)
            lt_opr = get_opfamily_member(typentry->btree_opf,
                                         typentry->btree_opintype,
                                         typentry->btree_opintype,
                                         BTLessStrategyNumber);

        /* As above, make sure array_cmp or record_cmp will succeed */
        if (lt_opr == ARRAY_LT_OP &&
            !array_element_has_compare(typentry))
            lt_opr = InvalidOid;
        else if (lt_opr == RECORD_LT_OP &&
                 !record_fields_have_compare(typentry))
            lt_opr = InvalidOid;

        typentry->lt_opr = lt_opr;
    }
    if ((flags & TYPECACHE_GT_OPR) && typentry->gt_opr == InvalidOid)
    {
        Oid         gt_opr = InvalidOid;

        if (typentry->btree_opf != InvalidOid)
            gt_opr = get_opfamily_member(typentry->btree_opf,
                                         typentry->btree_opintype,
                                         typentry->btree_opintype,
                                         BTGreaterStrategyNumber);

        /* As above, make sure array_cmp or record_cmp will succeed */
        if (gt_opr == ARRAY_GT_OP &&
            !array_element_has_compare(typentry))
            gt_opr = InvalidOid;
        else if (gt_opr == RECORD_GT_OP &&
                 !record_fields_have_compare(typentry))
            gt_opr = InvalidOid;

        typentry->gt_opr = gt_opr;
    }
    if ((flags & (TYPECACHE_CMP_PROC | TYPECACHE_CMP_PROC_FINFO)) &&
        typentry->cmp_proc == InvalidOid)
    {
        Oid         cmp_proc = InvalidOid;

        if (typentry->btree_opf != InvalidOid)
            cmp_proc = get_opfamily_proc(typentry->btree_opf,
                                         typentry->btree_opintype,
                                         typentry->btree_opintype,
                                         BTORDER_PROC);

        /* As above, make sure array_cmp or record_cmp will succeed */
        if (cmp_proc == F_BTARRAYCMP &&
            !array_element_has_compare(typentry))
            cmp_proc = InvalidOid;
        else if (cmp_proc == F_BTRECORDCMP &&
                 !record_fields_have_compare(typentry))
            cmp_proc = InvalidOid;

        typentry->cmp_proc = cmp_proc;
    }
    if ((flags & (TYPECACHE_HASH_PROC | TYPECACHE_HASH_PROC_FINFO)) &&
        typentry->hash_proc == InvalidOid)
    {
        Oid         hash_proc = InvalidOid;

        /*
         * We insist that the eq_opr, if one has been determined, match the
         * hash opclass; else report there is no hash function.
         */
        if (typentry->hash_opf != InvalidOid &&
            (!OidIsValid(typentry->eq_opr) ||
             typentry->eq_opr == get_opfamily_member(typentry->hash_opf,
                                                     typentry->hash_opintype,
                                                     typentry->hash_opintype,
                                                     HTEqualStrategyNumber)))
            hash_proc = get_opfamily_proc(typentry->hash_opf,
                                          typentry->hash_opintype,
                                          typentry->hash_opintype,
                                          HASHPROC);

        /*
         * As above, make sure hash_array will succeed.  We don't currently
         * support hashing for composite types, but when we do, we'll need
         * more logic here to check that case too.
         */
        if (hash_proc == F_HASH_ARRAY &&
            !array_element_has_hashing(typentry))
            hash_proc = InvalidOid;

        typentry->hash_proc = hash_proc;
    }

    /*
     * Set up fmgr lookup info as requested
     *
     * Note: we tell fmgr the finfo structures live in CacheMemoryContext,
     * which is not quite right (they're really in the hash table's private
     * memory context) but this will do for our purposes.
     */
    if ((flags & TYPECACHE_EQ_OPR_FINFO) &&
        typentry->eq_opr_finfo.fn_oid == InvalidOid &&
        typentry->eq_opr != InvalidOid)
    {
        Oid         eq_opr_func;

        eq_opr_func = get_opcode(typentry->eq_opr);
        if (eq_opr_func != InvalidOid)
            fmgr_info_cxt(eq_opr_func, &typentry->eq_opr_finfo,
                          CacheMemoryContext);
    }
    if ((flags & TYPECACHE_CMP_PROC_FINFO) &&
        typentry->cmp_proc_finfo.fn_oid == InvalidOid &&
        typentry->cmp_proc != InvalidOid)
    {
        fmgr_info_cxt(typentry->cmp_proc, &typentry->cmp_proc_finfo,
                      CacheMemoryContext);
    }
    if ((flags & TYPECACHE_HASH_PROC_FINFO) &&
        typentry->hash_proc_finfo.fn_oid == InvalidOid &&
        typentry->hash_proc != InvalidOid)
    {
        fmgr_info_cxt(typentry->hash_proc, &typentry->hash_proc_finfo,
                      CacheMemoryContext);
    }

    /*
     * If it's a composite type (row type), get tupdesc if requested
     */
    if ((flags & TYPECACHE_TUPDESC) &&
        typentry->tupDesc == NULL &&
        typentry->typtype == TYPTYPE_COMPOSITE)
    {
        load_typcache_tupdesc(typentry);
    }

    /*
     * If requested, get information about a range type
     */
    if ((flags & TYPECACHE_RANGE_INFO) &&
        typentry->rngelemtype == NULL &&
        typentry->typtype == TYPTYPE_RANGE)
    {
        load_rangetype_info(typentry);
    }

    return typentry;
}

/*
 * load_typcache_tupdesc --- helper routine to set up composite type's tupDesc
 */
static void
load_typcache_tupdesc(TypeCacheEntry *typentry)
{
    Relation    rel;

    if (!OidIsValid(typentry->typrelid))        /* should not happen */
        elog(ERROR, "invalid typrelid for composite type %u",
             typentry->type_id);
    rel = relation_open(typentry->typrelid, AccessShareLock);
    Assert(rel->rd_rel->reltype == typentry->type_id);

    /*
     * Link to the tupdesc and increment its refcount (we assert it's a
     * refcounted descriptor).  We don't use IncrTupleDescRefCount() for this,
     * because the reference mustn't be entered in the current resource owner;
     * it can outlive the current query.
     */
    typentry->tupDesc = RelationGetDescr(rel);

    Assert(typentry->tupDesc->tdrefcount > 0);
    typentry->tupDesc->tdrefcount++;

    relation_close(rel, AccessShareLock);
}

/*
 * load_rangetype_info --- helper routine to set up range type information
 */
static void
load_rangetype_info(TypeCacheEntry *typentry)
{
    Form_pg_range pg_range;
    HeapTuple   tup;
    Oid         subtypeOid;
    Oid         opclassOid;
    Oid         canonicalOid;
    Oid         subdiffOid;
    Oid         opfamilyOid;
    Oid         opcintype;
    Oid         cmpFnOid;

    /* get information from pg_range */
    tup = SearchSysCache1(RANGETYPE, ObjectIdGetDatum(typentry->type_id));
    /* should not fail, since we already checked typtype ... */
    if (!HeapTupleIsValid(tup))
        elog(ERROR, "cache lookup failed for range type %u",
             typentry->type_id);
    pg_range = (Form_pg_range) GETSTRUCT(tup);

    subtypeOid = pg_range->rngsubtype;
    typentry->rng_collation = pg_range->rngcollation;
    opclassOid = pg_range->rngsubopc;
    canonicalOid = pg_range->rngcanonical;
    subdiffOid = pg_range->rngsubdiff;

    ReleaseSysCache(tup);

    /* get opclass properties and look up the comparison function */
    opfamilyOid = get_opclass_family(opclassOid);
    opcintype = get_opclass_input_type(opclassOid);

    cmpFnOid = get_opfamily_proc(opfamilyOid, opcintype, opcintype,
                                 BTORDER_PROC);
    if (!RegProcedureIsValid(cmpFnOid))
        elog(ERROR, "missing support function %d(%u,%u) in opfamily %u",
             BTORDER_PROC, opcintype, opcintype, opfamilyOid);

    /* set up cached fmgrinfo structs */
    fmgr_info_cxt(cmpFnOid, &typentry->rng_cmp_proc_finfo,
                  CacheMemoryContext);
    if (OidIsValid(canonicalOid))
        fmgr_info_cxt(canonicalOid, &typentry->rng_canonical_finfo,
                      CacheMemoryContext);
    if (OidIsValid(subdiffOid))
        fmgr_info_cxt(subdiffOid, &typentry->rng_subdiff_finfo,
                      CacheMemoryContext);

    /* Lastly, set up link to the element type --- this marks data valid */
    typentry->rngelemtype = lookup_type_cache(subtypeOid, 0);
}


/*
 * array_element_has_equality and friends are helper routines to check
 * whether we should believe that array_eq and related functions will work
 * on the given array type or composite type.
 *
 * The logic above may call these repeatedly on the same type entry, so we
 * make use of the typentry->flags field to cache the results once known.
 * Also, we assume that we'll probably want all these facts about the type
 * if we want any, so we cache them all using only one lookup of the
 * component datatype(s).
 */

static bool
array_element_has_equality(TypeCacheEntry *typentry)
{
    if (!(typentry->flags & TCFLAGS_CHECKED_ELEM_PROPERTIES))
        cache_array_element_properties(typentry);
    return (typentry->flags & TCFLAGS_HAVE_ELEM_EQUALITY) != 0;
}

static bool
array_element_has_compare(TypeCacheEntry *typentry)
{
    if (!(typentry->flags & TCFLAGS_CHECKED_ELEM_PROPERTIES))
        cache_array_element_properties(typentry);
    return (typentry->flags & TCFLAGS_HAVE_ELEM_COMPARE) != 0;
}

static bool
array_element_has_hashing(TypeCacheEntry *typentry)
{
    if (!(typentry->flags & TCFLAGS_CHECKED_ELEM_PROPERTIES))
        cache_array_element_properties(typentry);
    return (typentry->flags & TCFLAGS_HAVE_ELEM_HASHING) != 0;
}

static void
cache_array_element_properties(TypeCacheEntry *typentry)
{
    Oid         elem_type = get_base_element_type(typentry->type_id);

    if (OidIsValid(elem_type))
    {
        TypeCacheEntry *elementry;

        elementry = lookup_type_cache(elem_type,
                                      TYPECACHE_EQ_OPR |
                                      TYPECACHE_CMP_PROC |
                                      TYPECACHE_HASH_PROC);
        if (OidIsValid(elementry->eq_opr))
            typentry->flags |= TCFLAGS_HAVE_ELEM_EQUALITY;
        if (OidIsValid(elementry->cmp_proc))
            typentry->flags |= TCFLAGS_HAVE_ELEM_COMPARE;
        if (OidIsValid(elementry->hash_proc))
            typentry->flags |= TCFLAGS_HAVE_ELEM_HASHING;
    }
    typentry->flags |= TCFLAGS_CHECKED_ELEM_PROPERTIES;
}

static bool
record_fields_have_equality(TypeCacheEntry *typentry)
{
    if (!(typentry->flags & TCFLAGS_CHECKED_FIELD_PROPERTIES))
        cache_record_field_properties(typentry);
    return (typentry->flags & TCFLAGS_HAVE_FIELD_EQUALITY) != 0;
}

static bool
record_fields_have_compare(TypeCacheEntry *typentry)
{
    if (!(typentry->flags & TCFLAGS_CHECKED_FIELD_PROPERTIES))
        cache_record_field_properties(typentry);
    return (typentry->flags & TCFLAGS_HAVE_FIELD_COMPARE) != 0;
}

static void
cache_record_field_properties(TypeCacheEntry *typentry)
{
    /*
     * For type RECORD, we can't really tell what will work, since we don't
     * have access here to the specific anonymous type.  Just assume that
     * everything will (we may get a failure at runtime ...)
     */
    if (typentry->type_id == RECORDOID)
        typentry->flags |= (TCFLAGS_HAVE_FIELD_EQUALITY |
                            TCFLAGS_HAVE_FIELD_COMPARE);
    else if (typentry->typtype == TYPTYPE_COMPOSITE)
    {
        TupleDesc   tupdesc;
        int         newflags;
        int         i;

        /* Fetch composite type's tupdesc if we don't have it already */
        if (typentry->tupDesc == NULL)
            load_typcache_tupdesc(typentry);
        tupdesc = typentry->tupDesc;

        /* Have each property if all non-dropped fields have the property */
        newflags = (TCFLAGS_HAVE_FIELD_EQUALITY |
                    TCFLAGS_HAVE_FIELD_COMPARE);
        for (i = 0; i < tupdesc->natts; i++)
        {
            TypeCacheEntry *fieldentry;

            if (tupdesc->attrs[i]->attisdropped)
                continue;

            fieldentry = lookup_type_cache(tupdesc->attrs[i]->atttypid,
                                           TYPECACHE_EQ_OPR |
                                           TYPECACHE_CMP_PROC);
            if (!OidIsValid(fieldentry->eq_opr))
                newflags &= ~TCFLAGS_HAVE_FIELD_EQUALITY;
            if (!OidIsValid(fieldentry->cmp_proc))
                newflags &= ~TCFLAGS_HAVE_FIELD_COMPARE;

            /* We can drop out of the loop once we disprove all bits */
            if (newflags == 0)
                break;
        }
        typentry->flags |= newflags;
    }
    typentry->flags |= TCFLAGS_CHECKED_FIELD_PROPERTIES;
}


/*
 * lookup_rowtype_tupdesc_internal --- internal routine to lookup a rowtype
 *
 * Same API as lookup_rowtype_tupdesc_noerror, but the returned tupdesc
 * hasn't had its refcount bumped.
 */
static TupleDesc
lookup_rowtype_tupdesc_internal(Oid type_id, int32 typmod, bool noError)
{
    if (type_id != RECORDOID)
    {
        /*
         * It's a named composite type, so use the regular typcache.
         */
        TypeCacheEntry *typentry;

        typentry = lookup_type_cache(type_id, TYPECACHE_TUPDESC);
        if (typentry->tupDesc == NULL && !noError)
            ereport(ERROR,
                    (errcode(ERRCODE_WRONG_OBJECT_TYPE),
                     errmsg("type %s is not composite",
                            format_type_be(type_id))));
        return typentry->tupDesc;
    }
    else
    {
        /*
         * It's a transient record type, so look in our record-type table.
         */
        if (typmod < 0 || typmod >= NextRecordTypmod)
        {
            if (!noError)
                ereport(ERROR,
                        (errcode(ERRCODE_WRONG_OBJECT_TYPE),
                         errmsg("record type has not been registered")));
            return NULL;
        }
        return RecordCacheArray[typmod];
    }
}

/*
 * lookup_rowtype_tupdesc
 *
 * Given a typeid/typmod that should describe a known composite type,
 * return the tuple descriptor for the type.  Will ereport on failure.
 *
 * Note: on success, we increment the refcount of the returned TupleDesc,
 * and log the reference in CurrentResourceOwner.  Caller should call
 * ReleaseTupleDesc or DecrTupleDescRefCount when done using the tupdesc.
 */
TupleDesc
lookup_rowtype_tupdesc(Oid type_id, int32 typmod)
{
    TupleDesc   tupDesc;

    tupDesc = lookup_rowtype_tupdesc_internal(type_id, typmod, false);
    IncrTupleDescRefCount(tupDesc);
    return tupDesc;
}

/*
 * lookup_rowtype_tupdesc_noerror
 *
 * As above, but if the type is not a known composite type and noError
 * is true, returns NULL instead of ereport'ing.  (Note that if a bogus
 * type_id is passed, you'll get an ereport anyway.)
 */
TupleDesc
lookup_rowtype_tupdesc_noerror(Oid type_id, int32 typmod, bool noError)
{
    TupleDesc   tupDesc;

    tupDesc = lookup_rowtype_tupdesc_internal(type_id, typmod, noError);
    if (tupDesc != NULL)
        IncrTupleDescRefCount(tupDesc);
    return tupDesc;
}

/*
 * lookup_rowtype_tupdesc_copy
 *
 * Like lookup_rowtype_tupdesc(), but the returned TupleDesc has been
 * copied into the CurrentMemoryContext and is not reference-counted.
 */
TupleDesc
lookup_rowtype_tupdesc_copy(Oid type_id, int32 typmod)
{
    TupleDesc   tmp;

    tmp = lookup_rowtype_tupdesc_internal(type_id, typmod, false);
    return CreateTupleDescCopyConstr(tmp);
}


/*
 * assign_record_type_typmod
 *
 * Given a tuple descriptor for a RECORD type, find or create a cache entry
 * for the type, and set the tupdesc's tdtypmod field to a value that will
 * identify this cache entry to lookup_rowtype_tupdesc.
 */
void
assign_record_type_typmod(TupleDesc tupDesc)
{
    RecordCacheEntry *recentry;
    TupleDesc   entDesc;
    Oid         hashkey[REC_HASH_KEYS];
    bool        found;
    int         i;
    ListCell   *l;
    int32       newtypmod;
    MemoryContext oldcxt;

    Assert(tupDesc->tdtypeid == RECORDOID);

    if (RecordCacheHash == NULL)
    {
        /* First time through: initialize the hash table */
        HASHCTL     ctl;

        MemSet(&ctl, 0, sizeof(ctl));
        ctl.keysize = REC_HASH_KEYS * sizeof(Oid);
        ctl.entrysize = sizeof(RecordCacheEntry);
        ctl.hash = tag_hash;
        RecordCacheHash = hash_create("Record information cache", 64,
                                      &ctl, HASH_ELEM | HASH_FUNCTION);

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

    /* Find or create a hashtable entry for this hash class */
    MemSet(hashkey, 0, sizeof(hashkey));
    for (i = 0; i < tupDesc->natts; i++)
    {
        if (i >= REC_HASH_KEYS)
            break;
        hashkey[i] = tupDesc->attrs[i]->atttypid;
    }
    recentry = (RecordCacheEntry *) hash_search(RecordCacheHash,
                                                (void *) hashkey,
                                                HASH_ENTER, &found);
    if (!found)
    {
        /* New entry ... hash_search initialized only the hash key */
        recentry->tupdescs = NIL;
    }

    /* Look for existing record cache entry */
    foreach(l, recentry->tupdescs)
    {
        entDesc = (TupleDesc) lfirst(l);
        if (equalTupleDescs(tupDesc, entDesc))
        {
            tupDesc->tdtypmod = entDesc->tdtypmod;
            return;
        }
    }

    /* Not present, so need to manufacture an entry */
    oldcxt = MemoryContextSwitchTo(CacheMemoryContext);

    if (RecordCacheArray == NULL)
    {
        RecordCacheArray = (TupleDesc *) palloc(64 * sizeof(TupleDesc));
        RecordCacheArrayLen = 64;
    }
    else if (NextRecordTypmod >= RecordCacheArrayLen)
    {
        int32       newlen = RecordCacheArrayLen * 2;

        RecordCacheArray = (TupleDesc *) repalloc(RecordCacheArray,
                                                  newlen * sizeof(TupleDesc));
        RecordCacheArrayLen = newlen;
    }

    /* if fail in subrs, no damage except possibly some wasted memory... */
    entDesc = CreateTupleDescCopy(tupDesc);
    recentry->tupdescs = lcons(entDesc, recentry->tupdescs);
    /* mark it as a reference-counted tupdesc */
    entDesc->tdrefcount = 1;
    /* now it's safe to advance NextRecordTypmod */
    newtypmod = NextRecordTypmod++;
    entDesc->tdtypmod = newtypmod;
    RecordCacheArray[newtypmod] = entDesc;

    /* report to caller as well */
    tupDesc->tdtypmod = newtypmod;

    MemoryContextSwitchTo(oldcxt);
}

/*
 * TypeCacheRelCallback
 *      Relcache inval callback function
 *
 * Delete the cached tuple descriptor (if any) for the given rel's composite
 * type, or for all composite types if relid == InvalidOid.  Also reset
 * whatever info we have cached about the composite type's comparability.
 *
 * This is called when a relcache invalidation event occurs for the given
 * relid.  We must scan the whole typcache hash since we don't know the
 * type OID corresponding to the relid.  We could do a direct search if this
 * were a syscache-flush callback on pg_type, but then we would need all
 * ALTER-TABLE-like commands that could modify a rowtype to issue syscache
 * invals against the rel's pg_type OID.  The extra SI signaling could very
 * well cost more than we'd save, since in most usages there are not very
 * many entries in a backend's typcache.  The risk of bugs-of-omission seems
 * high, too.
 *
 * Another possibility, with only localized impact, is to maintain a second
 * hashtable that indexes composite-type typcache entries by their typrelid.
 * But it's still not clear it's worth the trouble.
 */
static void
TypeCacheRelCallback(Datum arg, Oid relid)
{
    HASH_SEQ_STATUS status;
    TypeCacheEntry *typentry;

    /* TypeCacheHash must exist, else this callback wouldn't be registered */
    hash_seq_init(&status, TypeCacheHash);
    while ((typentry = (TypeCacheEntry *) hash_seq_search(&status)) != NULL)
    {
        if (typentry->typtype != TYPTYPE_COMPOSITE)
            continue;           /* skip non-composites */

        /* Skip if no match, unless we're zapping all composite types */
        if (relid != typentry->typrelid && relid != InvalidOid)
            continue;

        /* Delete tupdesc if we have it */
        if (typentry->tupDesc != NULL)
        {
            /*
             * Release our refcount, and free the tupdesc if none remain.
             * (Can't use DecrTupleDescRefCount because this reference is not
             * logged in current resource owner.)
             */
            Assert(typentry->tupDesc->tdrefcount > 0);
            if (--typentry->tupDesc->tdrefcount == 0)
                FreeTupleDesc(typentry->tupDesc);
            typentry->tupDesc = NULL;
        }

        /* Reset equality/comparison/hashing information */
        typentry->eq_opr = InvalidOid;
        typentry->lt_opr = InvalidOid;
        typentry->gt_opr = InvalidOid;
        typentry->cmp_proc = InvalidOid;
        typentry->hash_proc = InvalidOid;
        typentry->eq_opr_finfo.fn_oid = InvalidOid;
        typentry->cmp_proc_finfo.fn_oid = InvalidOid;
        typentry->hash_proc_finfo.fn_oid = InvalidOid;
        typentry->flags = 0;
    }
}


/*
 * Check if given OID is part of the subset that's sortable by comparisons
 */
static inline bool
enum_known_sorted(TypeCacheEnumData *enumdata, Oid arg)
{
    Oid         offset;

    if (arg < enumdata->bitmap_base)
        return false;
    offset = arg - enumdata->bitmap_base;
    if (offset > (Oid) INT_MAX)
        return false;
    return bms_is_member((int) offset, enumdata->sorted_values);
}


/*
 * compare_values_of_enum
 *      Compare two members of an enum type.
 *      Return <0, 0, or >0 according as arg1 <, =, or > arg2.
 *
 * Note: currently, the enumData cache is refreshed only if we are asked
 * to compare an enum value that is not already in the cache.  This is okay
 * because there is no support for re-ordering existing values, so comparisons
 * of previously cached values will return the right answer even if other
 * values have been added since we last loaded the cache.
 *
 * Note: the enum logic has a special-case rule about even-numbered versus
 * odd-numbered OIDs, but we take no account of that rule here; this
 * routine shouldn't even get called when that rule applies.
 */
int
compare_values_of_enum(TypeCacheEntry *tcache, Oid arg1, Oid arg2)
{
    TypeCacheEnumData *enumdata;
    EnumItem   *item1;
    EnumItem   *item2;

    /*
     * Equal OIDs are certainly equal --- this case was probably handled by
     * our caller, but we may as well check.
     */
    if (arg1 == arg2)
        return 0;

    /* Load up the cache if first time through */
    if (tcache->enumData == NULL)
        load_enum_cache_data(tcache);
    enumdata = tcache->enumData;

    /*
     * If both OIDs are known-sorted, we can just compare them directly.
     */
    if (enum_known_sorted(enumdata, arg1) &&
        enum_known_sorted(enumdata, arg2))
    {
        if (arg1 < arg2)
            return -1;
        else
            return 1;
    }

    /*
     * Slow path: we have to identify their actual sort-order positions.
     */
    item1 = find_enumitem(enumdata, arg1);
    item2 = find_enumitem(enumdata, arg2);

    if (item1 == NULL || item2 == NULL)
    {
        /*
         * We couldn't find one or both values.  That means the enum has
         * changed under us, so re-initialize the cache and try again. We
         * don't bother retrying the known-sorted case in this path.
         */
        load_enum_cache_data(tcache);
        enumdata = tcache->enumData;

        item1 = find_enumitem(enumdata, arg1);
        item2 = find_enumitem(enumdata, arg2);

        /*
         * If we still can't find the values, complain: we must have corrupt
         * data.
         */
        if (item1 == NULL)
            elog(ERROR, "enum value %u not found in cache for enum %s",
                 arg1, format_type_be(tcache->type_id));
        if (item2 == NULL)
            elog(ERROR, "enum value %u not found in cache for enum %s",
                 arg2, format_type_be(tcache->type_id));
    }

    if (item1->sort_order < item2->sort_order)
        return -1;
    else if (item1->sort_order > item2->sort_order)
        return 1;
    else
        return 0;
}

/*
 * Load (or re-load) the enumData member of the typcache entry.
 */
static void
load_enum_cache_data(TypeCacheEntry *tcache)
{
    TypeCacheEnumData *enumdata;
    Relation    enum_rel;
    SysScanDesc enum_scan;
    HeapTuple   enum_tuple;
    ScanKeyData skey;
    EnumItem   *items;
    int         numitems;
    int         maxitems;
    Oid         bitmap_base;
    Bitmapset  *bitmap;
    MemoryContext oldcxt;
    int         bm_size,
                start_pos;

    /* Check that this is actually an enum */
    if (tcache->typtype != TYPTYPE_ENUM)
        ereport(ERROR,
                (errcode(ERRCODE_WRONG_OBJECT_TYPE),
                 errmsg("%s is not an enum",
                        format_type_be(tcache->type_id))));

    /*
     * Read all the information for members of the enum type.  We collect the
     * info in working memory in the caller's context, and then transfer it to
     * permanent memory in CacheMemoryContext.  This minimizes the risk of
     * leaking memory from CacheMemoryContext in the event of an error partway
     * through.
     */
    maxitems = 64;
    items = (EnumItem *) palloc(sizeof(EnumItem) * maxitems);
    numitems = 0;

    /*
     * Scan pg_enum for the members of the target enum type.  We use a current
     * MVCC snapshot, *not* SnapshotNow, so that we see a consistent set of
     * rows even if someone commits a renumbering of the enum meanwhile. See
     * comments for RenumberEnumType in catalog/pg_enum.c for more info.
     */
    ScanKeyInit(&skey,
                Anum_pg_enum_enumtypid,
                BTEqualStrategyNumber, F_OIDEQ,
                ObjectIdGetDatum(tcache->type_id));

    enum_rel = heap_open(EnumRelationId, AccessShareLock);
    enum_scan = systable_beginscan(enum_rel,
                                   EnumTypIdLabelIndexId,
                                   true, GetLatestSnapshot(),
                                   1, &skey);

    while (HeapTupleIsValid(enum_tuple = systable_getnext(enum_scan)))
    {
        Form_pg_enum en = (Form_pg_enum) GETSTRUCT(enum_tuple);

        if (numitems >= maxitems)
        {
            maxitems *= 2;
            items = (EnumItem *) repalloc(items, sizeof(EnumItem) * maxitems);
        }
        items[numitems].enum_oid = HeapTupleGetOid(enum_tuple);
        items[numitems].sort_order = en->enumsortorder;
        numitems++;
    }

    systable_endscan(enum_scan);
    heap_close(enum_rel, AccessShareLock);

    /* Sort the items into OID order */
    qsort(items, numitems, sizeof(EnumItem), enum_oid_cmp);

    /*
     * Here, we create a bitmap listing a subset of the enum's OIDs that are
     * known to be in order and can thus be compared with just OID comparison.
     *
     * The point of this is that the enum's initial OIDs were certainly in
     * order, so there is some subset that can be compared via OID comparison;
     * and we'd rather not do binary searches unnecessarily.
     *
     * This is somewhat heuristic, and might identify a subset of OIDs that
     * isn't exactly what the type started with.  That's okay as long as the
     * subset is correctly sorted.
     */
    bitmap_base = InvalidOid;
    bitmap = NULL;
    bm_size = 1;                /* only save sets of at least 2 OIDs */

    for (start_pos = 0; start_pos < numitems - 1; start_pos++)
    {
        /*
         * Identify longest sorted subsequence starting at start_pos
         */
        Bitmapset  *this_bitmap = bms_make_singleton(0);
        int         this_bm_size = 1;
        Oid         start_oid = items[start_pos].enum_oid;
        float4      prev_order = items[start_pos].sort_order;
        int         i;

        for (i = start_pos + 1; i < numitems; i++)
        {
            Oid         offset;

            offset = items[i].enum_oid - start_oid;
            /* quit if bitmap would be too large; cutoff is arbitrary */
            if (offset >= 8192)
                break;
            /* include the item if it's in-order */
            if (items[i].sort_order > prev_order)
            {
                prev_order = items[i].sort_order;
                this_bitmap = bms_add_member(this_bitmap, (int) offset);
                this_bm_size++;
            }
        }

        /* Remember it if larger than previous best */
        if (this_bm_size > bm_size)
        {
            bms_free(bitmap);
            bitmap_base = start_oid;
            bitmap = this_bitmap;
            bm_size = this_bm_size;
        }
        else
            bms_free(this_bitmap);

        /*
         * Done if it's not possible to find a longer sequence in the rest of
         * the list.  In typical cases this will happen on the first
         * iteration, which is why we create the bitmaps on the fly instead of
         * doing a second pass over the list.
         */
        if (bm_size >= (numitems - start_pos - 1))
            break;
    }

    /* OK, copy the data into CacheMemoryContext */
    oldcxt = MemoryContextSwitchTo(CacheMemoryContext);
    enumdata = (TypeCacheEnumData *)
        palloc(offsetof(TypeCacheEnumData, enum_values) +
               numitems * sizeof(EnumItem));
    enumdata->bitmap_base = bitmap_base;
    enumdata->sorted_values = bms_copy(bitmap);
    enumdata->num_values = numitems;
    memcpy(enumdata->enum_values, items, numitems * sizeof(EnumItem));
    MemoryContextSwitchTo(oldcxt);

    pfree(items);
    bms_free(bitmap);

    /* And link the finished cache struct into the typcache */
    if (tcache->enumData != NULL)
        pfree(tcache->enumData);
    tcache->enumData = enumdata;
}

/*
 * Locate the EnumItem with the given OID, if present
 */
static EnumItem *
find_enumitem(TypeCacheEnumData *enumdata, Oid arg)
{
    EnumItem    srch;

    /* On some versions of Solaris, bsearch of zero items dumps core */
    if (enumdata->num_values <= 0)
        return NULL;

    srch.enum_oid = arg;
    return bsearch(&srch, enumdata->enum_values, enumdata->num_values,
                   sizeof(EnumItem), enum_oid_cmp);
}

/*
 * qsort comparison function for OID-ordered EnumItems
 */
static int
enum_oid_cmp(const void *left, const void *right)
{
    const EnumItem *l = (const EnumItem *) left;
    const EnumItem *r = (const EnumItem *) right;

    if (l->enum_oid < r->enum_oid)
        return -1;
    else if (l->enum_oid > r->enum_oid)
        return 1;
    else
        return 0;
}