Function transformFromClauseItem

src/backend/parser/parse_clause.c:1268–1762

* transformFromClauseItem - * Transform a FROM-clause item, adding any required entries to the * range table list being built in the ParseState, and return the * transformed item ready to include in the joinlist. Also build a * ParseNamespaceItem list describing the names exposed by this item. * This routine can recurse to handle SQL92 JOIN expressions. * * The function return va

 * are indeterminate and should be explicitly set by the caller before use.)
 */
static Node *
transformFromClauseItem(ParseState *pstate, Node *n,
						ParseNamespaceItem **top_nsitem,
						List **namespace)
{
	if (IsA(n, RangeVar))
	{
		/* Plain relation reference, or perhaps a CTE reference */
		RangeVar   *rv = (RangeVar *) n;
		RangeTblRef *rtr;
		ParseNamespaceItem *nsitem;

		/* Check if it's a CTE or tuplestore reference */
		nsitem = getNSItemForSpecialRelationTypes(pstate, rv);

		/* if not found above, must be a table reference */
		if (!nsitem)
			nsitem = transformTableEntry(pstate, rv);

		*top_nsitem = nsitem;
		*namespace = list_make1(nsitem);
		rtr = makeNode(RangeTblRef);
		rtr->rtindex = nsitem->p_rtindex;
		return (Node *) rtr;
	}
	else if (IsA(n, RangeSubselect))
	{
		/* sub-SELECT is like a plain relation */
		RangeTblRef *rtr;
		ParseNamespaceItem *nsitem;

		nsitem = transformRangeSubselect(pstate, (RangeSubselect *) n);
		*top_nsitem = nsitem;
		*namespace = list_make1(nsitem);
		rtr = makeNode(RangeTblRef);
		rtr->rtindex = nsitem->p_rtindex;
		return (Node *) rtr;
	}
	else if (IsA(n, RangeFunction))
	{
		/* function is like a plain relation */
		RangeTblRef *rtr;
		ParseNamespaceItem *nsitem;

		nsitem = transformRangeFunction(pstate, (RangeFunction *) n);
		*top_nsitem = nsitem;
		*namespace = list_make1(nsitem);
		rtr = makeNode(RangeTblRef);
		rtr->rtindex = nsitem->p_rtindex;
		return (Node *) rtr;
	}
	else if (IsA(n, RangeTableFunc))
	{
		/* table function is like a plain relation */
		RangeTblRef *rtr;
		ParseNamespaceItem *nsitem;

		nsitem = transformRangeTableFunc(pstate, (RangeTableFunc *) n);