catalog.c

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/*-------------------------------------------------------------------------
 *
 * catalog.c
 *      routines concerned with catalog naming conventions and other
 *      bits of hard-wired knowledge
 *
 *
 * Portions Copyright (c) 1996-2013, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *    src/backend/catalog/catalog.c
 *
 *-------------------------------------------------------------------------
 */

#include "postgres.h"

#include <fcntl.h>
#include <unistd.h>

#include "access/genam.h"
#include "access/sysattr.h"
#include "access/transam.h"
#include "catalog/catalog.h"
#include "catalog/indexing.h"
#include "catalog/namespace.h"
#include "catalog/pg_auth_members.h"
#include "catalog/pg_authid.h"
#include "catalog/pg_database.h"
#include "catalog/pg_namespace.h"
#include "catalog/pg_pltemplate.h"
#include "catalog/pg_db_role_setting.h"
#include "catalog/pg_shdepend.h"
#include "catalog/pg_shdescription.h"
#include "catalog/pg_shseclabel.h"
#include "catalog/pg_tablespace.h"
#include "catalog/toasting.h"
#include "common/relpath.h"
#include "miscadmin.h"
#include "storage/fd.h"
#include "utils/fmgroids.h"
#include "utils/rel.h"
#include "utils/tqual.h"



/*
 * forkname_to_number - look up fork number by name
 */
ForkNumber
forkname_to_number(char *forkName)
{
    ForkNumber  forkNum;

    for (forkNum = 0; forkNum <= MAX_FORKNUM; forkNum++)
        if (strcmp(forkNames[forkNum], forkName) == 0)
            return forkNum;

    ereport(ERROR,
            (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
             errmsg("invalid fork name"),
             errhint("Valid fork names are \"main\", \"fsm\", and \"vm\".")));
    return InvalidForkNumber;   /* keep compiler quiet */
}

/*
 * GetDatabasePath          - construct path to a database dir
 *
 * Result is a palloc'd string.
 *
 * XXX this must agree with relpath()!
 */
char *
GetDatabasePath(Oid dbNode, Oid spcNode)
{
    int         pathlen;
    char       *path;

    if (spcNode == GLOBALTABLESPACE_OID)
    {
        /* Shared system relations live in {datadir}/global */
        Assert(dbNode == 0);
        pathlen = 6 + 1;
        path = (char *) palloc(pathlen);
        snprintf(path, pathlen, "global");
    }
    else if (spcNode == DEFAULTTABLESPACE_OID)
    {
        /* The default tablespace is {datadir}/base */
        pathlen = 5 + OIDCHARS + 1;
        path = (char *) palloc(pathlen);
        snprintf(path, pathlen, "base/%u",
                 dbNode);
    }
    else
    {
        /* All other tablespaces are accessed via symlinks */
        pathlen = 9 + 1 + OIDCHARS + 1 + strlen(TABLESPACE_VERSION_DIRECTORY) +
            1 + OIDCHARS + 1;
        path = (char *) palloc(pathlen);
        snprintf(path, pathlen, "pg_tblspc/%u/%s/%u",
                 spcNode, TABLESPACE_VERSION_DIRECTORY, dbNode);
    }
    return path;
}


/*
 * IsSystemRelation
 *      True iff the relation is a system catalog relation.
 *
 *      NB: TOAST relations are considered system relations by this test
 *      for compatibility with the old IsSystemRelationName function.
 *      This is appropriate in many places but not all.  Where it's not,
 *      also check IsToastRelation.
 *
 *      We now just test if the relation is in the system catalog namespace;
 *      so it's no longer necessary to forbid user relations from having
 *      names starting with pg_.
 */
bool
IsSystemRelation(Relation relation)
{
    return IsSystemNamespace(RelationGetNamespace(relation)) ||
        IsToastNamespace(RelationGetNamespace(relation));
}

/*
 * IsSystemClass
 *      Like the above, but takes a Form_pg_class as argument.
 *      Used when we do not want to open the relation and have to
 *      search pg_class directly.
 */
bool
IsSystemClass(Form_pg_class reltuple)
{
    Oid         relnamespace = reltuple->relnamespace;

    return IsSystemNamespace(relnamespace) ||
        IsToastNamespace(relnamespace);
}

/*
 * IsToastRelation
 *      True iff relation is a TOAST support relation (or index).
 */
bool
IsToastRelation(Relation relation)
{
    return IsToastNamespace(RelationGetNamespace(relation));
}

/*
 * IsToastClass
 *      Like the above, but takes a Form_pg_class as argument.
 *      Used when we do not want to open the relation and have to
 *      search pg_class directly.
 */
bool
IsToastClass(Form_pg_class reltuple)
{
    Oid         relnamespace = reltuple->relnamespace;

    return IsToastNamespace(relnamespace);
}

/*
 * IsSystemNamespace
 *      True iff namespace is pg_catalog.
 *
 * NOTE: the reason this isn't a macro is to avoid having to include
 * catalog/pg_namespace.h in a lot of places.
 */
bool
IsSystemNamespace(Oid namespaceId)
{
    return namespaceId == PG_CATALOG_NAMESPACE;
}

/*
 * IsToastNamespace
 *      True iff namespace is pg_toast or my temporary-toast-table namespace.
 *
 * Note: this will return false for temporary-toast-table namespaces belonging
 * to other backends.  Those are treated the same as other backends' regular
 * temp table namespaces, and access is prevented where appropriate.
 */
bool
IsToastNamespace(Oid namespaceId)
{
    return (namespaceId == PG_TOAST_NAMESPACE) ||
        isTempToastNamespace(namespaceId);
}


/*
 * IsReservedName
 *      True iff name starts with the pg_ prefix.
 *
 *      For some classes of objects, the prefix pg_ is reserved for
 *      system objects only.  As of 8.0, this is only true for
 *      schema and tablespace names.
 */
bool
IsReservedName(const char *name)
{
    /* ugly coding for speed */
    return (name[0] == 'p' &&
            name[1] == 'g' &&
            name[2] == '_');
}


/*
 * IsSharedRelation
 *      Given the OID of a relation, determine whether it's supposed to be
 *      shared across an entire database cluster.
 *
 * Hard-wiring this list is pretty grotty, but we really need it so that
 * we can compute the locktag for a relation (and then lock it) without
 * having already read its pg_class entry.  If we try to retrieve relisshared
 * from pg_class with no pre-existing lock, there is a race condition against
 * anyone who is concurrently committing a change to the pg_class entry:
 * since we read system catalog entries under SnapshotNow, it's possible
 * that both the old and new versions of the row are invalid at the instants
 * we scan them.  We fix this by insisting that updaters of a pg_class
 * row must hold exclusive lock on the corresponding rel, and that users
 * of a relation must hold at least AccessShareLock on the rel *before*
 * trying to open its relcache entry.  But to lock a rel, you have to
 * know if it's shared.  Fortunately, the set of shared relations is
 * fairly static, so a hand-maintained list of their OIDs isn't completely
 * impractical.
 */
bool
IsSharedRelation(Oid relationId)
{
    /* These are the shared catalogs (look for BKI_SHARED_RELATION) */
    if (relationId == AuthIdRelationId ||
        relationId == AuthMemRelationId ||
        relationId == DatabaseRelationId ||
        relationId == PLTemplateRelationId ||
        relationId == SharedDescriptionRelationId ||
        relationId == SharedDependRelationId ||
        relationId == SharedSecLabelRelationId ||
        relationId == TableSpaceRelationId ||
        relationId == DbRoleSettingRelationId)
        return true;
    /* These are their indexes (see indexing.h) */
    if (relationId == AuthIdRolnameIndexId ||
        relationId == AuthIdOidIndexId ||
        relationId == AuthMemRoleMemIndexId ||
        relationId == AuthMemMemRoleIndexId ||
        relationId == DatabaseNameIndexId ||
        relationId == DatabaseOidIndexId ||
        relationId == PLTemplateNameIndexId ||
        relationId == SharedDescriptionObjIndexId ||
        relationId == SharedDependDependerIndexId ||
        relationId == SharedDependReferenceIndexId ||
        relationId == SharedSecLabelObjectIndexId ||
        relationId == TablespaceOidIndexId ||
        relationId == TablespaceNameIndexId ||
        relationId == DbRoleSettingDatidRolidIndexId)
        return true;
    /* These are their toast tables and toast indexes (see toasting.h) */
    if (relationId == PgShdescriptionToastTable ||
        relationId == PgShdescriptionToastIndex ||
        relationId == PgDbRoleSettingToastTable ||
        relationId == PgDbRoleSettingToastIndex)
        return true;
    return false;
}


/*
 * GetNewOid
 *      Generate a new OID that is unique within the given relation.
 *
 * Caller must have a suitable lock on the relation.
 *
 * Uniqueness is promised only if the relation has a unique index on OID.
 * This is true for all system catalogs that have OIDs, but might not be
 * true for user tables.  Note that we are effectively assuming that the
 * table has a relatively small number of entries (much less than 2^32)
 * and there aren't very long runs of consecutive existing OIDs.  Again,
 * this is reasonable for system catalogs but less so for user tables.
 *
 * Since the OID is not immediately inserted into the table, there is a
 * race condition here; but a problem could occur only if someone else
 * managed to cycle through 2^32 OIDs and generate the same OID before we
 * finish inserting our row.  This seems unlikely to be a problem.  Note
 * that if we had to *commit* the row to end the race condition, the risk
 * would be rather higher; therefore we use SnapshotDirty in the test,
 * so that we will see uncommitted rows.
 */
Oid
GetNewOid(Relation relation)
{
    Oid         oidIndex;

    /* If relation doesn't have OIDs at all, caller is confused */
    Assert(relation->rd_rel->relhasoids);

    /* In bootstrap mode, we don't have any indexes to use */
    if (IsBootstrapProcessingMode())
        return GetNewObjectId();

    /* The relcache will cache the identity of the OID index for us */
    oidIndex = RelationGetOidIndex(relation);

    /* If no OID index, just hand back the next OID counter value */
    if (!OidIsValid(oidIndex))
    {
        /*
         * System catalogs that have OIDs should *always* have a unique OID
         * index; we should only take this path for user tables. Give a
         * warning if it looks like somebody forgot an index.
         */
        if (IsSystemRelation(relation))
            elog(WARNING, "generating possibly-non-unique OID for \"%s\"",
                 RelationGetRelationName(relation));

        return GetNewObjectId();
    }

    /* Otherwise, use the index to find a nonconflicting OID */
    return GetNewOidWithIndex(relation, oidIndex, ObjectIdAttributeNumber);
}

/*
 * GetNewOidWithIndex
 *      Guts of GetNewOid: use the supplied index
 *
 * This is exported separately because there are cases where we want to use
 * an index that will not be recognized by RelationGetOidIndex: TOAST tables
 * have indexes that are usable, but have multiple columns and are on
 * ordinary columns rather than a true OID column.  This code will work
 * anyway, so long as the OID is the index's first column.  The caller must
 * pass in the actual heap attnum of the OID column, however.
 *
 * Caller must have a suitable lock on the relation.
 */
Oid
GetNewOidWithIndex(Relation relation, Oid indexId, AttrNumber oidcolumn)
{
    Oid         newOid;
    SnapshotData SnapshotDirty;
    SysScanDesc scan;
    ScanKeyData key;
    bool        collides;

    InitDirtySnapshot(SnapshotDirty);

    /* Generate new OIDs until we find one not in the table */
    do
    {
        CHECK_FOR_INTERRUPTS();

        newOid = GetNewObjectId();

        ScanKeyInit(&key,
                    oidcolumn,
                    BTEqualStrategyNumber, F_OIDEQ,
                    ObjectIdGetDatum(newOid));

        /* see notes above about using SnapshotDirty */
        scan = systable_beginscan(relation, indexId, true,
                                  &SnapshotDirty, 1, &key);

        collides = HeapTupleIsValid(systable_getnext(scan));

        systable_endscan(scan);
    } while (collides);

    return newOid;
}

/*
 * GetNewRelFileNode
 *      Generate a new relfilenode number that is unique within the given
 *      tablespace.
 *
 * If the relfilenode will also be used as the relation's OID, pass the
 * opened pg_class catalog, and this routine will guarantee that the result
 * is also an unused OID within pg_class.  If the result is to be used only
 * as a relfilenode for an existing relation, pass NULL for pg_class.
 *
 * As with GetNewOid, there is some theoretical risk of a race condition,
 * but it doesn't seem worth worrying about.
 *
 * Note: we don't support using this in bootstrap mode.  All relations
 * created by bootstrap have preassigned OIDs, so there's no need.
 */
Oid
GetNewRelFileNode(Oid reltablespace, Relation pg_class, char relpersistence)
{
    RelFileNodeBackend rnode;
    char       *rpath;
    int         fd;
    bool        collides;
    BackendId   backend;

    switch (relpersistence)
    {
        case RELPERSISTENCE_TEMP:
            backend = MyBackendId;
            break;
        case RELPERSISTENCE_UNLOGGED:
        case RELPERSISTENCE_PERMANENT:
            backend = InvalidBackendId;
            break;
        default:
            elog(ERROR, "invalid relpersistence: %c", relpersistence);
            return InvalidOid;  /* placate compiler */
    }

    /* This logic should match RelationInitPhysicalAddr */
    rnode.node.spcNode = reltablespace ? reltablespace : MyDatabaseTableSpace;
    rnode.node.dbNode = (rnode.node.spcNode == GLOBALTABLESPACE_OID) ? InvalidOid : MyDatabaseId;

    /*
     * The relpath will vary based on the backend ID, so we must initialize
     * that properly here to make sure that any collisions based on filename
     * are properly detected.
     */
    rnode.backend = backend;

    do
    {
        CHECK_FOR_INTERRUPTS();

        /* Generate the OID */
        if (pg_class)
            rnode.node.relNode = GetNewOid(pg_class);
        else
            rnode.node.relNode = GetNewObjectId();

        /* Check for existing file of same name */
        rpath = relpath(rnode, MAIN_FORKNUM);
        fd = BasicOpenFile(rpath, O_RDONLY | PG_BINARY, 0);

        if (fd >= 0)
        {
            /* definite collision */
            close(fd);
            collides = true;
        }
        else
        {
            /*
             * Here we have a little bit of a dilemma: if errno is something
             * other than ENOENT, should we declare a collision and loop? In
             * particular one might think this advisable for, say, EPERM.
             * However there really shouldn't be any unreadable files in a
             * tablespace directory, and if the EPERM is actually complaining
             * that we can't read the directory itself, we'd be in an infinite
             * loop.  In practice it seems best to go ahead regardless of the
             * errno.  If there is a colliding file we will get an smgr
             * failure when we attempt to create the new relation file.
             */
            collides = false;
        }

        pfree(rpath);
    } while (collides);

    return rnode.node.relNode;
}