/*-------------------------------------------------------------------------
 *
 * rewriteRemove.c
 *	  routines for removing rewrite rules
 *
 * Portions Copyright (c) 1996-2009, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *	  $PostgreSQL: pgsql/src/backend/rewrite/rewriteRemove.c,v 1.76 2009/01/22 17:27:54 petere Exp $
 *
 *-------------------------------------------------------------------------
 */
#include "postgres.h"

#include "access/genam.h"
#include "access/heapam.h"
#include "access/sysattr.h"
#include "catalog/dependency.h"
#include "catalog/indexing.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"
#include "utils/tqual.h"


/*
 * RemoveRewriteRule
 *
 * Delete a rule given its name.
 */
void
RemoveRewriteRule(Oid owningRel, const char *ruleName, DropBehavior behavior,
				  bool missing_ok)
{
	HeapTuple	tuple;
	Oid			eventRelationOid;
	ObjectAddress object;

	/*
	 * Find the tuple for the target rule.
	 */
	tuple = SearchSysCache(RULERELNAME,
						   ObjectIdGetDatum(owningRel),
						   PointerGetDatum(ruleName),
						   0, 0);

	/*
	 * complain if no rule with such name exists
	 */
	if (!HeapTupleIsValid(tuple))
	{
		if (!missing_ok)
			ereport(ERROR,
					(errcode(ERRCODE_UNDEFINED_OBJECT),
					 errmsg("rule \"%s\" for relation \"%s\" does not exist",
							ruleName, get_rel_name(owningRel))));
		else
			ereport(NOTICE,
					(errmsg("rule \"%s\" for relation \"%s\" does not exist, skipping",
							ruleName, get_rel_name(owningRel))));
		return;
	}

	/*
	 * Verify user has appropriate permissions.
	 */
	eventRelationOid = ((Form_pg_rewrite) GETSTRUCT(tuple))->ev_class;
	Assert(eventRelationOid == owningRel);
	if (!pg_class_ownercheck(eventRelationOid, GetUserId()))
		aclcheck_error(ACLCHECK_NOT_OWNER, ACL_KIND_CLASS,
					   get_rel_name(eventRelationOid));

	/*
	 * Do the deletion
	 */
	object.classId = RewriteRelationId;
	object.objectId = HeapTupleGetOid(tuple);
	object.objectSubId = 0;

	ReleaseSysCache(tuple);

	performDeletion(&object, behavior);
}

/*
 * RemoveAutomaticRulesOnEvent
 *
 * This will delete automatic rules, if any exist, on the event in the
 * relation.
 */
void
RemoveAutomaticRulesOnEvent(Relation rel, CmdType event_type)
{
	RuleLock   *rulelocks = rel->rd_rules;
	int			i;

	/* If there are no rules on the relation, waste no more time. */
	if (rulelocks == NULL)
		return;

	/*
	 * Look at all rules looking for the ones that are on the event
	 * and are automatic.
	 */
	for (i = 0; i < rulelocks->numLocks; i++)
	{
		RewriteRule *oneLock = rulelocks->rules[i];

		if (oneLock->event == event_type && oneLock->is_auto)
		{
			RemoveRewriteRuleById(oneLock->ruleId);
			elog(DEBUG1, "removing automatic rule with OID %u\n",
				 oneLock->ruleId);
			deleteDependencyRecordsFor(RewriteRelationId, oneLock->ruleId);
		}
	}
}

/*
 * 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 = heap_open(RewriteRelationId, RowExclusiveLock);

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

	rcscan = systable_beginscan(RewriteRelation, RewriteOidIndexId, true,
								SnapshotNow, 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 = heap_open(eventRelationOid, AccessExclusiveLock);

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

	systable_endscan(rcscan);

	heap_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... */
	heap_close(event_relation, NoLock);
}
