rewriteRemove.c

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/*-------------------------------------------------------------------------
 *
 * rewriteRemove.c
 *    routines for removing rewrite rules
 *
 * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *    src/backend/rewrite/rewriteRemove.c
 *
 *-------------------------------------------------------------------------
 */
#include "postgres.h"

#include "access/genam.h"
#include "access/htup_details.h"
#include "access/sysattr.h"
#include "access/table.h"
#include "catalog/catalog.h"
#include "catalog/dependency.h"
#include "catalog/indexing.h"
#include "catalog/namespace.h"
#include "catalog/pg_rewrite.h"
#include "miscadmin.h"
#include "rewrite/rewriteRemove.h"
#include "utils/acl.h"
#include "utils/fmgroids.h"
#include "utils/inval.h"
#include "utils/lsyscache.h"
#include "utils/rel.h"
#include "utils/syscache.h"

/*
 * Guts of rule deletion.
 */
void
RemoveRewriteRuleById(Oid ruleOid)
{
    Relation    RewriteRelation;
    ScanKeyData skey[1];
    SysScanDesc rcscan;
    Relation    event_relation;
    HeapTuple   tuple;
    Oid         eventRelationOid;

    /*
     * Open the pg_rewrite relation.
     */
    RewriteRelation = table_open(RewriteRelationId, RowExclusiveLock);

    /*
     * Find the tuple for the target rule.
     */
    ScanKeyInit(&skey[0],
                Anum_pg_rewrite_oid,
                BTEqualStrategyNumber, F_OIDEQ,
                ObjectIdGetDatum(ruleOid));

    rcscan = systable_beginscan(RewriteRelation, RewriteOidIndexId, true,
                                NULL, 1, skey);

    tuple = systable_getnext(rcscan);

    if (!HeapTupleIsValid(tuple))
        elog(ERROR, "could not find tuple for rule %u", ruleOid);

    /*
     * We had better grab AccessExclusiveLock to ensure that no queries are
     * going on that might depend on this rule.  (Note: a weaker lock would
     * suffice if it's not an ON SELECT rule.)
     */
    eventRelationOid = ((Form_pg_rewrite) GETSTRUCT(tuple))->ev_class;
    event_relation = table_open(eventRelationOid, AccessExclusiveLock);

    if (!allowSystemTableMods && IsSystemRelation(event_relation))
        ereport(ERROR,
                (errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
                 errmsg("permission denied: \"%s\" is a system catalog",
                        RelationGetRelationName(event_relation))));

    /*
     * Now delete the pg_rewrite tuple for the rule
     */
    CatalogTupleDelete(RewriteRelation, &tuple->t_self);

    systable_endscan(rcscan);

    table_close(RewriteRelation, RowExclusiveLock);

    /*
     * Issue shared-inval notice to force all backends (including me!) to
     * update relcache entries with the new rule set.
     */
    CacheInvalidateRelcache(event_relation);

    /* Close rel, but keep lock till commit... */
    table_close(event_relation, NoLock);
}