/*-------------------------------------------------------------------------

 *

 * rewriteRemove.c

 *    routines for removing rewrite rules

 *

 * Portions Copyright (c) 1996-2025, 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/table.h"

#include "catalog/catalog.h"

#include "catalog/indexing.h"

#include "catalog/pg_rewrite.h"

#include "miscadmin.h"

#include "rewrite/rewriteRemove.h"

#include "utils/fmgroids.h"

#include "utils/inval.h"

#include "utils/rel.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);

}