Function add_expr_subquery_rte

src/backend/cdb/cdbsubselect.c:839–881

* Pulls up the expr sublink subquery into the top-level range table. */

 * Pulls up the expr sublink subquery into the top-level range table.
 */
static int
add_expr_subquery_rte(Query *parse, Query *subselect)
{
	int					subq_indx;
	ParseNamespaceItem	*pni;
	ParseState			*pstate;

	/**
	 * Generate column names.
	 * TODO: improve this to keep old names around
	 */
	ListCell   *lc = NULL;
	int			teNum = 0;

	foreach(lc, subselect->targetList)
	{
		TargetEntry *te = (TargetEntry *) lfirst(lc);

		te->resname = psprintf("csq_c%d", teNum);
		teNum++;
	}

	/* Create a dummy ParseState for addRangeTableEntryForSubquery */
	pstate = make_parsestate(NULL);

	/*
	 * Create a RTE entry in the parent query for the subquery.
	 * It is marked as lateral, because any correlation quals will
	 * refer to other RTEs in the parent query.
	 */
	pni = addRangeTableEntryForSubquery(pstate,
										subselect,
										makeAlias("Expr_SUBQUERY", NIL),
										true, /* lateral */
										false /* inFromClause */ );
	parse->rtable = lappend(parse->rtable, pni->p_rte);

	/* assume new rte is at end */
	subq_indx = list_length(parse->rtable);
	Assert(pni->p_rte == rt_fetch(subq_indx, parse->rtable));

	return subq_indx;
}


/* Create a join expression linking the supplied larg node