Remove duplicate find_em_expr_for_rel function

The functions find_em_expr_for_rel and ts_find_em_expr_for_rel are
identical. This patch removes find_em_expr_for_rel and changes all
call-sites to use ts_find_em_expr_for_rel.

src/utils.c

@@ -700,6 +700,13 @@ ts_get_appendrelinfo(PlannerInfo *root, Index rti, bool missing_ok)
 	return NULL;
 }
 
+/*
+ * Find an equivalence class member expression, all of whose Vars, come from
+ * the indicated relation.
+ *
+ * This function has been copied from find_em_expr_for_rel in
+ * contrib/postgres_fdw/postgres_fdw.c in postgres source.
+ */
 Expr *
 ts_find_em_expr_for_rel(EquivalenceClass *ec, RelOptInfo *rel)
 {

tsl/src/fdw/deparse.c

@@ -212,34 +212,6 @@ static bool is_subquery_var(Var *node, RelOptInfo *foreignrel, int *relno, int *
 static void get_relation_column_alias_ids(Var *node, RelOptInfo *foreignrel, int *relno,
 										  int *colno);
 
-/*
- * Find an equivalence class member expression, all of whose Vars, come from
- * the indicated relation.
- */
-extern Expr *
-find_em_expr_for_rel(EquivalenceClass *ec, RelOptInfo *rel)
-{
-	ListCell *lc_em;
-
-	foreach (lc_em, ec->ec_members)
-	{
-		EquivalenceMember *em = lfirst(lc_em);
-
-		if (bms_is_subset(em->em_relids, rel->relids))
-		{
-			/*
-			 * If there is more than one equivalence member whose Vars are
-			 * taken entirely from this relation, we'll be content to choose
-			 * any one of those.
-			 */
-			return em->em_expr;
-		}
-	}
-
-	/* We didn't find any suitable equivalence class expression */
-	return NULL;
-}
-
 /*
  * Examine each qual clause in input_conds, and classify them into two groups,
  * which are returned as two lists:
@@ -2799,7 +2771,7 @@ appendOrderByClause(List *pathkeys, deparse_expr_cxt *context)
 		PathKey *pathkey = lfirst(lcell);
 		Expr *em_expr;
 
-		em_expr = find_em_expr_for_rel(pathkey->pk_eclass, baserel);
+		em_expr = ts_find_em_expr_for_rel(pathkey->pk_eclass, baserel);
 		Assert(em_expr != NULL);
 
 		appendStringInfoString(buf, delim);

tsl/src/fdw/deparse.h

@@ -19,7 +19,6 @@ typedef struct DeparsedInsertStmt
 	List *retrieved_attrs;
 } DeparsedInsertStmt;
 
-extern Expr *find_em_expr_for_rel(EquivalenceClass *ec, RelOptInfo *rel);
 extern void deparse_insert_stmt(DeparsedInsertStmt *stmt, RangeTblEntry *rte, Index rtindex,
 								Relation rel, List *target_attrs, bool do_nothing,
 								List *returning_list);

tsl/src/fdw/scan_plan.c

@@ -70,7 +70,7 @@ get_useful_pathkeys_for_relation(PlannerInfo *root, RelOptInfo *rel)
 			 * is_foreign_expr would detect volatile expressions as well, but
 			 * checking ec_has_volatile here saves some cycles.
 			 */
-			if (pathkey_ec->ec_has_volatile || !(em_expr = find_em_expr_for_rel(pathkey_ec, rel)) ||
+			if (pathkey_ec->ec_has_volatile || !(em_expr = ts_find_em_expr_for_rel(pathkey_ec, rel)) ||
 				!is_foreign_expr(root, rel, em_expr))
 			{
 				query_pathkeys_ok = false;