/*-------------------------------------------------------------------------
 *
 * 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);
}