rewritehandler.c

PostgreSQL 8.1.4的源码 适用于Linux下的开源数据库系统

	}

	if (expr == NULL)
	{
		/*
		 * No per-column default, so look for a default for the type itself.
		 */
		expr = get_typdefault(atttype);
	}

	if (expr == NULL)
		return NULL;			/* No default anywhere */

	/*
	 * Make sure the value is coerced to the target column type; this will
	 * generally be true already, but there seem to be some corner cases
	 * involving domain defaults where it might not be true. This should match
	 * the parser's processing of non-defaulted expressions --- see
	 * updateTargetListEntry().
	 */
	exprtype = exprType(expr);

	expr = coerce_to_target_type(NULL,	/* no UNKNOWN params here */
								 expr, exprtype,
								 atttype, atttypmod,
								 COERCION_ASSIGNMENT,
								 COERCE_IMPLICIT_CAST);
	if (expr == NULL)
		ereport(ERROR,
				(errcode(ERRCODE_DATATYPE_MISMATCH),
				 errmsg("column \"%s\" is of type %s"
						" but default expression is of type %s",
						NameStr(att_tup->attname),
						format_type_be(atttype),
						format_type_be(exprtype)),
			   errhint("You will need to rewrite or cast the expression.")));

	return expr;
}


/*
 * matchLocks -
 *	  match the list of locks and returns the matching rules
 */
static List *
matchLocks(CmdType event,
		   RuleLock *rulelocks,
		   int varno,
		   Query *parsetree)
{
	List	   *matching_locks = NIL;
	int			nlocks;
	int			i;

	if (rulelocks == NULL)
		return NIL;

	if (parsetree->commandType != CMD_SELECT)
	{
		if (parsetree->resultRelation != varno)
			return NIL;
	}

	nlocks = rulelocks->numLocks;

	for (i = 0; i < nlocks; i++)
	{
		RewriteRule *oneLock = rulelocks->rules[i];

		if (oneLock->event == event)
		{
			if (parsetree->commandType != CMD_SELECT ||
				(oneLock->attrno == -1 ?
				 rangeTableEntry_used((Node *) parsetree, varno, 0) :
				 attribute_used((Node *) parsetree,
								varno, oneLock->attrno, 0)))
				matching_locks = lappend(matching_locks, oneLock);
		}
	}

	return matching_locks;
}


/*
 * ApplyRetrieveRule - expand an ON SELECT rule
 */
static Query *
ApplyRetrieveRule(Query *parsetree,
				  RewriteRule *rule,
				  int rt_index,
				  bool relation_level,
				  Relation relation,
				  List *activeRIRs)
{
	Query	   *rule_action;
	RangeTblEntry *rte,
			   *subrte;

	if (list_length(rule->actions) != 1)
		elog(ERROR, "expected just one rule action");
	if (rule->qual != NULL)
		elog(ERROR, "cannot handle qualified ON SELECT rule");
	if (!relation_level)
		elog(ERROR, "cannot handle per-attribute ON SELECT rule");

	/*
	 * Make a modifiable copy of the view query, and acquire needed locks on
	 * the relations it mentions.
	 */
	rule_action = copyObject(linitial(rule->actions));

	AcquireRewriteLocks(rule_action);

	/*
	 * Recursively expand any view references inside the view.
	 */
	rule_action = fireRIRrules(rule_action, activeRIRs);

	/*
	 * VIEWs are really easy --- just plug the view query in as a subselect,
	 * replacing the relation's original RTE.
	 */
	rte = rt_fetch(rt_index, parsetree->rtable);

	rte->rtekind = RTE_SUBQUERY;
	rte->relid = InvalidOid;
	rte->subquery = rule_action;
	rte->inh = false;			/* must not be set for a subquery */

	/*
	 * We move the view's permission check data down to its rangetable. The
	 * checks will actually be done against the *OLD* entry therein.
	 */
	subrte = rt_fetch(PRS2_OLD_VARNO, rule_action->rtable);
	Assert(subrte->relid == relation->rd_id);
	subrte->requiredPerms = rte->requiredPerms;
	subrte->checkAsUser = rte->checkAsUser;

	rte->requiredPerms = 0;		/* no permission check on subquery itself */
	rte->checkAsUser = InvalidOid;

	/*
	 * FOR UPDATE/SHARE of view?
	 */
	if (list_member_int(parsetree->rowMarks, rt_index))
	{
		/*
		 * Remove the view from the list of rels that will actually be marked
		 * FOR UPDATE/SHARE by the executor.  It will still be access- checked
		 * for write access, though.
		 */
		parsetree->rowMarks = list_delete_int(parsetree->rowMarks, rt_index);

		/*
		 * Set up the view's referenced tables as if FOR UPDATE/SHARE.
		 */
		markQueryForLocking(rule_action, parsetree->forUpdate,
							parsetree->rowNoWait, true);
	}

	return parsetree;
}

/*
 * Recursively mark all relations used by a view as FOR UPDATE/SHARE.
 *
 * This may generate an invalid query, eg if some sub-query uses an
 * aggregate.  We leave it to the planner to detect that.
 *
 * NB: this must agree with the parser's transformLocking() routine.
 */
static void
markQueryForLocking(Query *qry, bool forUpdate, bool noWait, bool skipOldNew)
{
	Index		rti = 0;
	ListCell   *l;

	if (qry->rowMarks)
	{
		if (forUpdate != qry->forUpdate)
			ereport(ERROR,
					(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
			errmsg("cannot use both FOR UPDATE and FOR SHARE in one query")));
		if (noWait != qry->rowNoWait)
			ereport(ERROR,
					(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
					 errmsg("cannot use both wait and NOWAIT in one query")));
	}
	qry->forUpdate = forUpdate;
	qry->rowNoWait = noWait;

	foreach(l, qry->rtable)
	{
		RangeTblEntry *rte = (RangeTblEntry *) lfirst(l);

		rti++;

		/* Ignore OLD and NEW entries if we are at top level of view */
		if (skipOldNew &&
			(rti == PRS2_OLD_VARNO || rti == PRS2_NEW_VARNO))
			continue;

		if (rte->rtekind == RTE_RELATION)
		{
			qry->rowMarks = list_append_unique_int(qry->rowMarks, rti);
			rte->requiredPerms |= ACL_SELECT_FOR_UPDATE;
		}
		else if (rte->rtekind == RTE_SUBQUERY)
		{
			/* FOR UPDATE/SHARE of subquery is propagated to subquery's rels */
			markQueryForLocking(rte->subquery, forUpdate, noWait, false);
		}
	}
}


/*
 * fireRIRonSubLink -
 *	Apply fireRIRrules() to each SubLink (subselect in expression) found
 *	in the given tree.
 *
 * NOTE: although this has the form of a walker, we cheat and modify the
 * SubLink nodes in-place.	It is caller's responsibility to ensure that
 * no unwanted side-effects occur!
 *
 * This is unlike most of the other routines that recurse into subselects,
 * because we must take control at the SubLink node in order to replace
 * the SubLink's subselect link with the possibly-rewritten subquery.
 */
static bool
fireRIRonSubLink(Node *node, List *activeRIRs)
{
	if (node == NULL)
		return false;
	if (IsA(node, SubLink))
	{
		SubLink    *sub = (SubLink *) node;

		/* Do what we came for */
		sub->subselect = (Node *) fireRIRrules((Query *) sub->subselect,
											   activeRIRs);
		/* Fall through to process lefthand args of SubLink */
	}

	/*
	 * Do NOT recurse into Query nodes, because fireRIRrules already processed
	 * subselects of subselects for us.
	 */
	return expression_tree_walker(node, fireRIRonSubLink,
								  (void *) activeRIRs);
}


/*
 * fireRIRrules -
 *	Apply all RIR rules on each rangetable entry in a query
 */
static Query *
fireRIRrules(Query *parsetree, List *activeRIRs)
{
	int			rt_index;

	/*
	 * don't try to convert this into a foreach loop, because rtable list can
	 * get changed each time through...
	 */
	rt_index = 0;
	while (rt_index < list_length(parsetree->rtable))
	{
		RangeTblEntry *rte;
		Relation	rel;
		List	   *locks;
		RuleLock   *rules;
		RewriteRule *rule;
		int			i;

		++rt_index;

		rte = rt_fetch(rt_index, parsetree->rtable);

		/*
		 * A subquery RTE can't have associated rules, so there's nothing to
		 * do to this level of the query, but we must recurse into the
		 * subquery to expand any rule references in it.
		 */
		if (rte->rtekind == RTE_SUBQUERY)
		{
			rte->subquery = fireRIRrules(rte->subquery, activeRIRs);
			continue;
		}

		/*
		 * Joins and other non-relation RTEs can be ignored completely.
		 */
		if (rte->rtekind != RTE_RELATION)
			continue;

		/*
		 * If the table is not referenced in the query, then we ignore it.
		 * This prevents infinite expansion loop due to new rtable entries
		 * inserted by expansion of a rule. A table is referenced if it is
		 * part of the join set (a source table), or is referenced by any Var
		 * nodes, or is the result table.
		 */
		if (rt_index != parsetree->resultRelation &&
			!rangeTableEntry_used((Node *) parsetree, rt_index, 0))
			continue;

		/*
		 * We can use NoLock here since either the parser or
		 * AcquireRewriteLocks should have locked the rel already.
		 */
		rel = heap_open(rte->relid, NoLock);

		/*
		 * Collect the RIR rules that we must apply
		 */
		rules = rel->rd_rules;
		if (rules == NULL)
		{
			heap_close(rel, NoLock);
			continue;
		}
		locks = NIL;
		for (i = 0; i < rules->numLocks; i++)
		{
			rule = rules->rules[i];
			if (rule->event != CMD_SELECT)
				continue;

			if (rule->attrno > 0)
			{
				/* per-attr rule; do we need it? */
				if (!attribute_used((Node *) parsetree, rt_index,
									rule->attrno, 0))
					continue;
			}

			locks = lappend(locks, rule);
		}

		/*
		 * If we found any, apply them --- but first check for recursion!
		 */
		if (locks != NIL)
		{
			ListCell   *l;

			if (list_member_oid(activeRIRs, RelationGetRelid(rel)))
				ereport(ERROR,
						(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
						 errmsg("infinite recursion detected in rules for relation \"%s\"",
								RelationGetRelationName(rel))));
			activeRIRs = lcons_oid(RelationGetRelid(rel), activeRIRs);

			foreach(l, locks)
			{
				rule = lfirst(l);

				parsetree = ApplyRetrieveRule(parsetree,
											  rule,
											  rt_index,
											  rule->attrno == -1,
											  rel,
											  activeRIRs);
			}

			activeRIRs = list_delete_first(activeRIRs);
		}

		heap_close(rel, NoLock);
	}

	/*
	 * Recurse into sublink subqueries, too.  But we already did the ones in
	 * the rtable.
	 */
	if (parsetree->hasSubLinks)
		query_tree_walker(parsetree, fireRIRonSubLink, (void *) activeRIRs,
						  QTW_IGNORE_RT_SUBQUERIES);

	return parsetree;
}


/*
 * Modify the given query by adding 'AND rule_qual IS NOT TRUE' to its
 * qualification.  This is used to generate suitable "else clauses" for
 * conditional INSTEAD rules.  (Unfortunately we must use "x IS NOT TRUE",
 * not just "NOT x" which the planner is much smarter about, else we will
 * do the wrong thing when the qual evaluates to NULL.)
 *
 * The rule_qual may contain references to OLD or NEW.	OLD references are
 * replaced by references to the specified rt_index (the relation that the
 * rule applies to).  NEW references are only possible for INSERT and UPDATE
 * queries on the relation itself, and so they should be replaced by copies
 * of the related entries in the query's own targetlist.
 */
static Query *
CopyAndAddInvertedQual(Query *parsetree,
					   Node *rule_qual,
					   int rt_index,
					   CmdType event)