rewritehandler.c

来自「PostgreSQL7.4.6 for Linux」· C语言 代码 · 共 1,349 行 · 第 1/3 页

		((ArrayRef *) prior_tle->expr)->refassgnexpr == NULL ||
		((ArrayRef *) src_tle->expr)->refrestype !=
		((ArrayRef *) prior_tle->expr)->refrestype)
		ereport(ERROR,
				(errcode(ERRCODE_SYNTAX_ERROR),
				 errmsg("multiple assignments to same column \"%s\"",
						attrName)));

	/*
	 * Prior TLE could be a nest of ArrayRefs if we do this more than
	 * once.
	 */
	priorbottom = (Node *) ((ArrayRef *) prior_tle->expr)->refexpr;
	while (priorbottom != NULL && IsA(priorbottom, ArrayRef) &&
		   ((ArrayRef *) priorbottom)->refassgnexpr != NULL)
		priorbottom = (Node *) ((ArrayRef *) priorbottom)->refexpr;
	if (!equal(priorbottom, ((ArrayRef *) src_tle->expr)->refexpr))
		ereport(ERROR,
				(errcode(ERRCODE_SYNTAX_ERROR),
				 errmsg("multiple assignments to same column \"%s\"",
						attrName)));

	/*
	 * Looks OK to nest 'em.
	 */
	newexpr = makeNode(ArrayRef);
	memcpy(newexpr, src_tle->expr, sizeof(ArrayRef));
	newexpr->refexpr = prior_tle->expr;

	return makeTargetEntry(resdom, (Expr *) newexpr);
}


/*
 * Make an expression tree for the default value for a column.
 *
 * If there is no default, return a NULL instead.
 */
Node *
build_column_default(Relation rel, int attrno)
{
	TupleDesc	rd_att = rel->rd_att;
	Form_pg_attribute att_tup = rd_att->attrs[attrno - 1];
	Oid			atttype = att_tup->atttypid;
	int32		atttypmod = att_tup->atttypmod;
	Node	   *expr = NULL;
	Oid			exprtype;

	/*
	 * Scan to see if relation has a default for this column.
	 */
	if (rd_att->constr && rd_att->constr->num_defval > 0)
	{
		AttrDefault *defval = rd_att->constr->defval;
		int			ndef = rd_att->constr->num_defval;

		while (--ndef >= 0)
		{
			if (attrno == defval[ndef].adnum)
			{
				/*
				 * Found it, convert string representation to node tree.
				 */
				expr = stringToNode(defval[ndef].adbin);
				break;
			}
		}
	}

	if (expr == NULL)
	{
		/*
		 * No per-column default, so look for a default for the type
		 * itself.
		 */
		if (att_tup->attisset)
		{
			/*
			 * Set attributes are represented as OIDs no matter what the
			 * set element type is, and the element type's default is
			 * irrelevant too.
			 */
		}
		else
			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;
}


static Query *
ApplyRetrieveRule(Query *parsetree,
				  RewriteRule *rule,
				  int rt_index,
				  bool relation_level,
				  Relation relation,
				  bool relIsUsed,
				  List *activeRIRs)
{
	Query	   *rule_action;
	RangeTblEntry *rte,
			   *subrte;

	if (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 recursively expand
	 * any view references inside it.
	 */
	rule_action = copyObject(lfirst(rule->actions));

	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->checkForRead = rte->checkForRead;
	subrte->checkForWrite = rte->checkForWrite;
	subrte->checkAsUser = rte->checkAsUser;

	rte->checkForRead = false;	/* no permission check on subquery itself */
	rte->checkForWrite = false;
	rte->checkAsUser = InvalidOid;

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

		/*
		 * Set up the view's referenced tables as if FOR UPDATE.
		 */
		markQueryForUpdate(rule_action, true);
	}

	return parsetree;
}

/*
 * Recursively mark all relations used by a view as FOR UPDATE.
 *
 * 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 transformForUpdate() routine.
 */
static void
markQueryForUpdate(Query *qry, bool skipOldNew)
{
	Index		rti = 0;
	List	   *l;

	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)
		{
			if (!intMember(rti, qry->rowMarks))
				qry->rowMarks = lappendi(qry->rowMarks, rti);
			rte->checkForWrite = true;
		}
		else if (rte->rtekind == RTE_SUBQUERY)
		{
			/* FOR UPDATE of subquery is propagated to subquery's rels */
			markQueryForUpdate(rte->subquery, 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 < length(parsetree->rtable))
	{
		RangeTblEntry *rte;
		Relation	rel;
		List	   *locks;
		RuleLock   *rules;
		RewriteRule *rule;
		LOCKMODE	lockmode;
		bool		relIsUsed;
		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.
		 */
		relIsUsed = rangeTableEntry_used((Node *) parsetree, rt_index, 0);

		if (!relIsUsed && rt_index != parsetree->resultRelation)
			continue;

		/*
		 * This may well be the first access to the relation during the
		 * current statement (it will be, if this Query was extracted from
		 * a rule or somehow got here other than via the parser).
		 * Therefore, grab the appropriate lock type for the relation, and
		 * do not release it until end of transaction.	This protects the
		 * rewriter and planner against schema changes mid-query.
		 *
		 * If the relation is the query's result relation, then
		 * RewriteQuery() already got the right lock on it, so we need no
		 * additional lock. Otherwise, check to see if the relation is
		 * accessed FOR UPDATE or not.
		 */
		if (rt_index == parsetree->resultRelation)
			lockmode = NoLock;
		else if (intMember(rt_index, parsetree->rowMarks))
			lockmode = RowShareLock;
		else
			lockmode = AccessShareLock;

		rel = heap_open(rte->relid, lockmode);

		/*
		 * 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)
		{
			List	   *newActiveRIRs;
			List	   *l;

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

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

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

		heap_close(rel, NoLock);