Function cdbpullup_findEclassInTargetList

src/backend/cdb/cdbpullup.c:242–335

* cdbpullup_findEclassInTargetList * * Searches the given equivalence class for a member that uses no rels * outside the 'relids' set, and either is a member of 'targetlist', or * uses no Vars that are not in 'targetlist'. Furthermore, if * 'hashOpFamily' is valid, the member must be hashable using that hash * operator family. * * If found, returns the chosen member's expression, otherwise

 * targetlist expr.)
 */
Expr *
cdbpullup_findEclassInTargetList(EquivalenceClass *eclass, List *targetlist,
								 Oid hashOpFamily, bool *relabel_stripped)
{
	ListCell   *lc;

	foreach(lc, eclass->ec_members)
	{
		EquivalenceMember *em = (EquivalenceMember *) lfirst(lc);
		Expr	   *key = (Expr *) em->em_expr;
		ListCell *lc_tle;

		if (OidIsValid(hashOpFamily) &&
			!get_opfamily_member(hashOpFamily, em->em_datatype, em->em_datatype,
								 HTEqualStrategyNumber))
			continue;

		/* A constant is OK regardless of the target list */
		if (em->em_is_const)
			return key;

		/*-------
		 * Try to find this EC member in the target list.
		 *
		 * We do the search in a very lenient way:
		 *
		 * 1. Ignore RelabelType nodes on top of both sides, like
		 *    tlist_member_ignore_relabel() does.
		 * 2. Ignore varnoold/varoattno fields in Var nodes, like
		 *    tlist_member_match_var() does.
		 * 3. Also Accept "naked" targetlists, without TargetEntry nodes
		 *
		 * Unfortunately, neither tlist_member_ignore_relabel() nor
		 * tlist_member_match_var() does exactly what we need.
		 *-------
		 */
		while (IsA(key, RelabelType))
		{
			key = (Expr *) ((RelabelType *) key)->arg;
			if(relabel_stripped && (!*relabel_stripped))
				*relabel_stripped = true;
		}

		foreach(lc_tle, targetlist)
		{
			Node	   *tlexpr = lfirst(lc_tle);
			Node	   *naked_tlexpr;

			/*
			 * Check if targetlist is a List of TargetEntry. (Planner's
			 * RelOptInfo targetlists don't have TargetEntry nodes.)
			 */
			if (IsA(tlexpr, TargetEntry))
				tlexpr = (Node *) ((TargetEntry *) tlexpr)->expr;

			/* ignore RelabelType nodes on both sides */
			naked_tlexpr = tlexpr;
			while (naked_tlexpr && IsA(naked_tlexpr, RelabelType))