catalog.c

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/*-------------------------------------------------------------------------
 *
 * catalog.c
 *      routines concerned with catalog naming conventions and other
 *      bits of hard-wired knowledge
 *
 *
 * Portions Copyright (c) 1996-2023, 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/htup_details.h"
#include "access/sysattr.h"
#include "access/table.h"
#include "access/transam.h"
#include "catalog/catalog.h"
#include "catalog/namespace.h"
#include "catalog/pg_auth_members.h"
#include "catalog/pg_authid.h"
#include "catalog/pg_database.h"
#include "catalog/pg_db_role_setting.h"
#include "catalog/pg_largeobject.h"
#include "catalog/pg_namespace.h"
#include "catalog/pg_parameter_acl.h"
#include "catalog/pg_replication_origin.h"
#include "catalog/pg_shdepend.h"
#include "catalog/pg_shdescription.h"
#include "catalog/pg_shseclabel.h"
#include "catalog/pg_subscription.h"
#include "catalog/pg_tablespace.h"
#include "catalog/pg_type.h"
#include "miscadmin.h"
#include "storage/fd.h"
#include "utils/fmgroids.h"
#include "utils/fmgrprotos.h"
#include "utils/rel.h"
#include "utils/snapmgr.h"
#include "utils/syscache.h"
 
/*
 * Parameters to determine when to emit a log message in
 * GetNewOidWithIndex()
 */
#define GETNEWOID_LOG_THRESHOLD 1000000
#define GETNEWOID_LOG_MAX_INTERVAL 128000000
 
/*
 * IsSystemRelation
 *      True iff the relation is either a system catalog or a toast table.
 *      See IsCatalogRelation for the exact definition of a system catalog.
 *
 *      We treat toast tables of user relations as "system relations" for
 *      protection purposes, e.g. you can't change their schemas without
 *      special permissions.  Therefore, most uses of this function are
 *      checking whether allow_system_table_mods restrictions apply.
 *      For other purposes, consider whether you shouldn't be using
 *      IsCatalogRelation instead.
 *
 *      This function does not perform any catalog accesses.
 *      Some callers rely on that!
 */
bool
IsSystemRelation(Relation relation)
{
    return IsSystemClass(RelationGetRelid(relation), relation->rd_rel);
}
 
/*
 * 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(Oid relid, Form_pg_class reltuple)
{
    /* IsCatalogRelationOid is a bit faster, so test that first */
    return (IsCatalogRelationOid(relid) || IsToastClass(reltuple));
}
 
/*
 * IsCatalogRelation
 *      True iff the relation is a system catalog.
 *
 *      By a system catalog, we mean one that is created during the bootstrap
 *      phase of initdb.  That includes not just the catalogs per se, but
 *      also their indexes, and TOAST tables and indexes if any.
 *
 *      This function does not perform any catalog accesses.
 *      Some callers rely on that!
 */
bool
IsCatalogRelation(Relation relation)
{
    return IsCatalogRelationOid(RelationGetRelid(relation));
}
 
/*
 * IsCatalogRelationOid
 *      True iff the relation identified by this OID is a system catalog.
 *
 *      By a system catalog, we mean one that is created during the bootstrap
 *      phase of initdb.  That includes not just the catalogs per se, but
 *      also their indexes, and TOAST tables and indexes if any.
 *
 *      This function does not perform any catalog accesses.
 *      Some callers rely on that!
 */
bool
IsCatalogRelationOid(Oid relid)
{
    /*
     * We consider a relation to be a system catalog if it has a pinned OID.
     * This includes all the defined catalogs, their indexes, and their TOAST
     * tables and indexes.
     *
     * This rule excludes the relations in information_schema, which are not
     * integral to the system and can be treated the same as user relations.
     * (Since it's valid to drop and recreate information_schema, any rule
     * that did not act this way would be wrong.)
     *
     * This test is reliable since an OID wraparound will skip this range of
     * OIDs; see GetNewObjectId().
     */
    return (relid < (Oid) FirstUnpinnedObjectId);
}
 
/*
 * IsToastRelation
 *      True iff relation is a TOAST support relation (or index).
 *
 *      Does not perform any catalog accesses.
 */
bool
IsToastRelation(Relation relation)
{
    /*
     * What we actually check is whether the relation belongs to a pg_toast
     * namespace.  This should be equivalent because of restrictions that are
     * enforced elsewhere against creating user relations in, or moving
     * relations into/out of, a pg_toast namespace.  Notice also that this
     * will not say "true" for toast tables belonging to other sessions' temp
     * tables; we expect that other mechanisms will prevent access to those.
     */
    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);
}
 
/*
 * IsCatalogNamespace
 *      True iff namespace is pg_catalog.
 *
 *      Does not perform any catalog accesses.
 *
 * NOTE: the reason this isn't a macro is to avoid having to include
 * catalog/pg_namespace.h in a lot of places.
 */
bool
IsCatalogNamespace(Oid namespaceId)
{
    return namespaceId == PG_CATALOG_NAMESPACE;
}
 
/*
 * IsToastNamespace
 *      True iff namespace is pg_toast or my temporary-toast-table namespace.
 *
 *      Does not perform any catalog accesses.
 *
 * 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.
 * If you need to check for those, you may be able to use isAnyTempNamespace,
 * but beware that that does involve a catalog access.
 */
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 was only true for
 *      schema and tablespace names.  With 9.6, this is also true
 *      for roles.
 */
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.
 *
 * In older releases, this had to be hard-wired so that we could compute the
 * locktag for a relation and lock it before examining its catalog entry.
 * Since we now have MVCC catalog access, the race conditions that made that
 * a hard requirement are gone, so we could look at relaxing this restriction.
 * However, if we scanned the pg_class entry to find relisshared, and only
 * then locked the relation, pg_class could get updated in the meantime,
 * forcing us to scan the relation again, which would definitely be complex
 * and might have undesirable performance consequences.  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 == DbRoleSettingRelationId ||
        relationId == ParameterAclRelationId ||
        relationId == ReplicationOriginRelationId ||
        relationId == SharedDependRelationId ||
        relationId == SharedDescriptionRelationId ||
        relationId == SharedSecLabelRelationId ||
        relationId == SubscriptionRelationId ||
        relationId == TableSpaceRelationId)
        return true;
    /* These are their indexes */
    if (relationId == AuthIdOidIndexId ||
        relationId == AuthIdRolnameIndexId ||
        relationId == AuthMemMemRoleIndexId ||
        relationId == AuthMemRoleMemIndexId ||
        relationId == AuthMemOidIndexId ||
        relationId == AuthMemGrantorIndexId ||
        relationId == DatabaseNameIndexId ||
        relationId == DatabaseOidIndexId ||
        relationId == DbRoleSettingDatidRolidIndexId ||
        relationId == ParameterAclOidIndexId ||
        relationId == ParameterAclParnameIndexId ||
        relationId == ReplicationOriginIdentIndex ||
        relationId == ReplicationOriginNameIndex ||
        relationId == SharedDependDependerIndexId ||
        relationId == SharedDependReferenceIndexId ||
        relationId == SharedDescriptionObjIndexId ||
        relationId == SharedSecLabelObjectIndexId ||
        relationId == SubscriptionNameIndexId ||
        relationId == SubscriptionObjectIndexId ||
        relationId == TablespaceNameIndexId ||
        relationId == TablespaceOidIndexId)
        return true;
    /* These are their toast tables and toast indexes */
    if (relationId == PgAuthidToastTable ||
        relationId == PgAuthidToastIndex ||
        relationId == PgDatabaseToastTable ||
        relationId == PgDatabaseToastIndex ||
        relationId == PgDbRoleSettingToastTable ||
        relationId == PgDbRoleSettingToastIndex ||
        relationId == PgParameterAclToastTable ||
        relationId == PgParameterAclToastIndex ||
        relationId == PgReplicationOriginToastTable ||
        relationId == PgReplicationOriginToastIndex ||
        relationId == PgShdescriptionToastTable ||
        relationId == PgShdescriptionToastIndex ||
        relationId == PgShseclabelToastTable ||
        relationId == PgShseclabelToastIndex ||
        relationId == PgSubscriptionToastTable ||
        relationId == PgSubscriptionToastIndex ||
        relationId == PgTablespaceToastTable ||
        relationId == PgTablespaceToastIndex)
        return true;
    return false;
}
 
/*
 * IsPinnedObject
 *      Given the class + OID identity of a database object, report whether
 *      it is "pinned", that is not droppable because the system requires it.
 *
 * We used to represent this explicitly in pg_depend, but that proved to be
 * an undesirable amount of overhead, so now we rely on an OID range test.
 */
bool
IsPinnedObject(Oid classId, Oid objectId)
{
    /*
     * Objects with OIDs above FirstUnpinnedObjectId are never pinned.  Since
     * the OID generator skips this range when wrapping around, this check
     * guarantees that user-defined objects are never considered pinned.
     */
    if (objectId >= FirstUnpinnedObjectId)
        return false;
 
    /*
     * Large objects are never pinned.  We need this special case because
     * their OIDs can be user-assigned.
     */
    if (classId == LargeObjectRelationId)
        return false;
 
    /*
     * There are a few objects defined in the catalog .dat files that, as a
     * matter of policy, we prefer not to treat as pinned.  We used to handle
     * that by excluding them from pg_depend, but it's just as easy to
     * hard-wire their OIDs here.  (If the user does indeed drop and recreate
     * them, they'll have new but certainly-unpinned OIDs, so no problem.)
     *
     * Checking both classId and objectId is overkill, since OIDs below
     * FirstGenbkiObjectId should be globally unique, but do it anyway for
     * robustness.
     */
 
    /* the public namespace is not pinned */
    if (classId == NamespaceRelationId &&
        objectId == PG_PUBLIC_NAMESPACE)
        return false;
 
    /*
     * Databases are never pinned.  It might seem that it'd be prudent to pin
     * at least template0; but we do this intentionally so that template0 and
     * template1 can be rebuilt from each other, thus letting them serve as
     * mutual backups (as long as you've not modified template1, anyway).
     */
    if (classId == DatabaseRelationId)
        return false;
 
    /*
     * All other initdb-created objects are pinned.  This is overkill (the
     * system doesn't really depend on having every last weird datatype, for
     * instance) but generating only the minimum required set of dependencies
     * seems hard, and enforcing an accurate list would be much more expensive
     * than the simple range test used here.
     */
    return true;
}
 
 
/*
 * GetNewOidWithIndex
 *      Generate a new OID that is unique within the system relation.
 *
 * 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 SnapshotAny in the test, so that
 * we will see uncommitted rows.  (We used to use SnapshotDirty, but that has
 * the disadvantage that it ignores recently-deleted rows, creating a risk
 * of transient conflicts for as long as our own MVCC snapshots think a
 * recently-deleted row is live.  The risk is far higher when selecting TOAST
 * OIDs, because SnapshotToast considers dead rows as active indefinitely.)
 *
 * 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.  This is a mostly reasonable assumption for
 * system catalogs.
 *
 * Caller must have a suitable lock on the relation.
 */
Oid
GetNewOidWithIndex(Relation relation, Oid indexId, AttrNumber oidcolumn)
{
    Oid         newOid;
    SysScanDesc scan;
    ScanKeyData key;
    bool        collides;
    uint64      retries = 0;
    uint64      retries_before_log = GETNEWOID_LOG_THRESHOLD;
 
    /* Only system relations are supported */
    Assert(IsSystemRelation(relation));
 
    /* In bootstrap mode, we don't have any indexes to use */
    if (IsBootstrapProcessingMode())
        return GetNewObjectId();
 
    /*
     * We should never be asked to generate a new pg_type OID during
     * pg_upgrade; doing so would risk collisions with the OIDs it wants to
     * assign.  Hitting this assert means there's some path where we failed to
     * ensure that a type OID is determined by commands in the dump script.
     */
    Assert(!IsBinaryUpgrade || RelationGetRelid(relation) != TypeRelationId);
 
    /* 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 SnapshotAny */
        scan = systable_beginscan(relation, indexId, true,
                                  SnapshotAny, 1, &key);
 
        collides = HeapTupleIsValid(systable_getnext(scan));
 
        systable_endscan(scan);
 
        /*
         * Log that we iterate more than GETNEWOID_LOG_THRESHOLD but have not
         * yet found OID unused in the relation. Then repeat logging with
         * exponentially increasing intervals until we iterate more than
         * GETNEWOID_LOG_MAX_INTERVAL. Finally repeat logging every
         * GETNEWOID_LOG_MAX_INTERVAL unless an unused OID is found. This
         * logic is necessary not to fill up the server log with the similar
         * messages.
         */
        if (retries >= retries_before_log)
        {
            ereport(LOG,
                    (errmsg("still searching for an unused OID in relation \"%s\"",
                            RelationGetRelationName(relation)),
                     errdetail_plural("OID candidates have been checked %llu time, but no unused OID has been found yet.",
                                      "OID candidates have been checked %llu times, but no unused OID has been found yet.",
                                      retries,
                                      (unsigned long long) retries)));
 
            /*
             * Double the number of retries to do before logging next until it
             * reaches GETNEWOID_LOG_MAX_INTERVAL.
             */
            if (retries_before_log * 2 <= GETNEWOID_LOG_MAX_INTERVAL)
                retries_before_log *= 2;
            else
                retries_before_log += GETNEWOID_LOG_MAX_INTERVAL;
        }
 
        retries++;
    } while (collides);
 
    /*
     * If at least one log message is emitted, also log the completion of OID
     * assignment.
     */
    if (retries > GETNEWOID_LOG_THRESHOLD)
    {
        ereport(LOG,
                (errmsg_plural("new OID has been assigned in relation \"%s\" after %llu retry",
                               "new OID has been assigned in relation \"%s\" after %llu retries",
                               retries,
                               RelationGetRelationName(relation), (unsigned long long) retries)));
    }
 
    return newOid;
}
 
/*
 * GetNewRelFileNumber
 *      Generate a new relfilenumber that is unique within the
 *      database of the given tablespace.
 *
 * If the relfilenumber 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 relfilenumber for an existing relation, pass NULL for pg_class.
 *
 * As with GetNewOidWithIndex(), 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.
 */
RelFileNumber
GetNewRelFileNumber(Oid reltablespace, Relation pg_class, char relpersistence)
{
    RelFileLocatorBackend rlocator;
    char       *rpath;
    bool        collides;
    BackendId   backend;
 
    /*
     * If we ever get here during pg_upgrade, there's something wrong; all
     * relfilenumber assignments during a binary-upgrade run should be
     * determined by commands in the dump script.
     */
    Assert(!IsBinaryUpgrade);
 
    switch (relpersistence)
    {
        case RELPERSISTENCE_TEMP:
            backend = BackendIdForTempRelations();
            break;
        case RELPERSISTENCE_UNLOGGED:
        case RELPERSISTENCE_PERMANENT:
            backend = InvalidBackendId;
            break;
        default:
            elog(ERROR, "invalid relpersistence: %c", relpersistence);
            return InvalidRelFileNumber;    /* placate compiler */
    }
 
    /* This logic should match RelationInitPhysicalAddr */
    rlocator.locator.spcOid = reltablespace ? reltablespace : MyDatabaseTableSpace;
    rlocator.locator.dbOid =
        (rlocator.locator.spcOid == 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.
     */
    rlocator.backend = backend;
 
    do
    {
        CHECK_FOR_INTERRUPTS();
 
        /* Generate the OID */
        if (pg_class)
            rlocator.locator.relNumber = GetNewOidWithIndex(pg_class, ClassOidIndexId,
                                                            Anum_pg_class_oid);
        else
            rlocator.locator.relNumber = GetNewObjectId();
 
        /* Check for existing file of same name */
        rpath = relpath(rlocator, MAIN_FORKNUM);
 
        if (access(rpath, F_OK) == 0)
        {
            /* definite collision */
            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
             * 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 rlocator.locator.relNumber;
}
 
/*
 * SQL callable interface for GetNewOidWithIndex().  Outside of initdb's
 * direct insertions into catalog tables, and recovering from corruption, this
 * should rarely be needed.
 *
 * Function is intentionally not documented in the user facing docs.
 */
Datum
pg_nextoid(PG_FUNCTION_ARGS)
{
    Oid         reloid = PG_GETARG_OID(0);
    Name        attname = PG_GETARG_NAME(1);
    Oid         idxoid = PG_GETARG_OID(2);
    Relation    rel;
    Relation    idx;
    HeapTuple   atttuple;
    Form_pg_attribute attform;
    AttrNumber  attno;
    Oid         newoid;
 
    /*
     * As this function is not intended to be used during normal running, and
     * only supports system catalogs (which require superuser permissions to
     * modify), just checking for superuser ought to not obstruct valid
     * usecases.
     */
    if (!superuser())
        ereport(ERROR,
                (errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
                 errmsg("must be superuser to call %s()",
                        "pg_nextoid")));
 
    rel = table_open(reloid, RowExclusiveLock);
    idx = index_open(idxoid, RowExclusiveLock);
 
    if (!IsSystemRelation(rel))
        ereport(ERROR,
                (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                 errmsg("pg_nextoid() can only be used on system catalogs")));
 
    if (idx->rd_index->indrelid != RelationGetRelid(rel))
        ereport(ERROR,
                (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                 errmsg("index \"%s\" does not belong to table \"%s\"",
                        RelationGetRelationName(idx),
                        RelationGetRelationName(rel))));
 
    atttuple = SearchSysCacheAttName(reloid, NameStr(*attname));
    if (!HeapTupleIsValid(atttuple))
        ereport(ERROR,
                (errcode(ERRCODE_UNDEFINED_COLUMN),
                 errmsg("column \"%s\" of relation \"%s\" does not exist",
                        NameStr(*attname), RelationGetRelationName(rel))));
 
    attform = ((Form_pg_attribute) GETSTRUCT(atttuple));
    attno = attform->attnum;
 
    if (attform->atttypid != OIDOID)
        ereport(ERROR,
                (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                 errmsg("column \"%s\" is not of type oid",
                        NameStr(*attname))));
 
    if (IndexRelationGetNumberOfKeyAttributes(idx) != 1 ||
        idx->rd_index->indkey.values[0] != attno)
        ereport(ERROR,
                (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                 errmsg("index \"%s\" is not the index for column \"%s\"",
                        RelationGetRelationName(idx),
                        NameStr(*attname))));
 
    newoid = GetNewOidWithIndex(rel, idxoid, attno);
 
    ReleaseSysCache(atttuple);
    table_close(rel, RowExclusiveLock);
    index_close(idx, RowExclusiveLock);
 
    PG_RETURN_OID(newoid);
}
 
/*
 * SQL callable interface for StopGeneratingPinnedObjectIds().
 *
 * This is only to be used by initdb, so it's intentionally not documented in
 * the user facing docs.
 */
Datum
pg_stop_making_pinned_objects(PG_FUNCTION_ARGS)
{
    /*
     * Belt-and-suspenders check, since StopGeneratingPinnedObjectIds will
     * fail anyway in non-single-user mode.
     */
    if (!superuser())
        ereport(ERROR,
                (errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
                 errmsg("must be superuser to call %s()",
                        "pg_stop_making_pinned_objects")));
 
    StopGeneratingPinnedObjectIds();
 
    PG_RETURN_VOID();
}