Function transformFromClause

src/backend/parser/parse_clause.c:133–173

* transformFromClause - * Process the FROM clause and add items to the query's range table, * joinlist, and namespace. * * Note: we assume that the pstate's p_rtable, p_joinlist, and p_namespace * lists were initialized to NIL when the pstate was created. * We will add onto any entries already present --- this is needed for rule * processing, as well as for UPDATE and DELETE. */

 * processing, as well as for UPDATE and DELETE.
 */
void
transformFromClause(ParseState *pstate, List *frmList)
{
	ListCell   *fl;

	/*
	 * The grammar will have produced a list of RangeVars, RangeSubselects,
	 * RangeFunctions, and/or JoinExprs. Transform each one (possibly adding
	 * entries to the rtable), check for duplicate refnames, and then add it
	 * to the joinlist and namespace.
	 *
	 * Note we must process the items left-to-right for proper handling of
	 * LATERAL references.
	 */
	foreach(fl, frmList)
	{
		Node	   *n = lfirst(fl);
		ParseNamespaceItem *nsitem;
		List	   *namespace;

		n = transformFromClauseItem(pstate, n,
									&nsitem,
									&namespace);

		checkNameSpaceConflicts(pstate, pstate->p_namespace, namespace);

		/* Mark the new namespace items as visible only to LATERAL */
		setNamespaceLateralState(namespace, true, true);

		pstate->p_joinlist = lappend(pstate->p_joinlist, n);
		pstate->p_namespace = list_concat(pstate->p_namespace, namespace);
	}

	/*
	 * We're done parsing the FROM list, so make all namespace items
	 * unconditionally visible.  Note that this will also reset lateral_only
	 * for any namespace items that were already present when we were called;
	 * but those should have been that way already.
	 */
	setNamespaceLateralState(pstate->p_namespace, false, true);
}

/*
 * winref_checkspec_walker