Function transformRuleStmt

src/backend/parser/parse_utilcmd.c:4114–4409

* transformRuleStmt - * transform a CREATE RULE Statement. The action is a list of parse * trees which is transformed into a list of query trees, and we also * transform the WHERE clause if any. * * actions and whereClause are output parameters that receive the * transformed results. */

 * transformed results.
 */
void
transformRuleStmt(RuleStmt *stmt, const char *queryString,
				  List **actions, Node **whereClause)
{
	Relation	rel;
	ParseState *pstate;
	ParseNamespaceItem *oldnsitem;
	ParseNamespaceItem *newnsitem;

	/*
	 * To avoid deadlock, make sure the first thing we do is grab
	 * AccessExclusiveLock on the target relation.  This will be needed by
	 * DefineQueryRewrite(), and we don't want to grab a lesser lock
	 * beforehand.
	 */
	rel = table_openrv(stmt->relation, AccessExclusiveLock);

	if (rel->rd_rel->relkind == RELKIND_MATVIEW)
		ereport(ERROR,
				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
				 errmsg("rules on materialized views are not supported")));

	/* Set up pstate */
	pstate = make_parsestate(NULL);
	pstate->p_sourcetext = queryString;

	/*
	 * NOTE: 'OLD' must always have a varno equal to 1 and 'NEW' equal to 2.
	 * Set up their ParseNamespaceItems in the main pstate for use in parsing
	 * the rule qualification.
	 */
	oldnsitem = addRangeTableEntryForRelation(pstate, rel,
											  AccessShareLock,
											  makeAlias("old", NIL),
											  false, false);
	newnsitem = addRangeTableEntryForRelation(pstate, rel,
											  AccessShareLock,
											  makeAlias("new", NIL),
											  false, false);
	/* Must override addRangeTableEntry's default access-check flags */
	oldnsitem->p_rte->requiredPerms = 0;
	newnsitem->p_rte->requiredPerms = 0;

	/*
	 * They must be in the namespace too for lookup purposes, but only add the
	 * one(s) that are relevant for the current kind of rule.  In an UPDATE
	 * rule, quals must refer to OLD.field or NEW.field to be unambiguous, but
	 * there's no need to be so picky for INSERT & DELETE.  We do not add them
	 * to the joinlist.
	 */
	switch (stmt->event)
	{
		case CMD_SELECT:
			addNSItemToQuery(pstate, oldnsitem, false, true, true);
			break;
		case CMD_UPDATE:
			addNSItemToQuery(pstate, oldnsitem, false, true, true);
			addNSItemToQuery(pstate, newnsitem, false, true, true);