Handles EXPLAIN output diffs in PG15: extra arrows&result lines

To handle extra "->" arrows resulting from extra Result lines
in explain outputs, we add the following explain method to
multi_test_helpers.sql file

- plan_without_arrows() is added for cases where we want the
whole explain output without arrows and without Result lines

src/test/regress/expected/columnar_chunk_filtering.out

@@ -264,17 +264,21 @@ EXPLAIN (analyze on, costs off, timing off, summary off)
          Columnar Projected Columns: a
 (9 rows)
 
+SELECT plan_without_arrows($Q$
 EXPLAIN (costs off, timing off, summary off)
   SELECT y, * FROM another_columnar_table;
-                      QUERY PLAN
+$Q$);
+                      plan_without_arrows
 ---------------------------------------------------------------------
  Custom Scan (ColumnarScan) on another_columnar_table
    Columnar Projected Columns: x, y
 (2 rows)
 
+SELECT plan_without_arrows($Q$
 EXPLAIN (costs off, timing off, summary off)
   SELECT *, x FROM another_columnar_table;
-                      QUERY PLAN
+$Q$);
+                      plan_without_arrows
 ---------------------------------------------------------------------
  Custom Scan (ColumnarScan) on another_columnar_table
    Columnar Projected Columns: x, y

src/test/regress/expected/multi_test_helpers.out

@@ -81,6 +81,18 @@ BEGIN
     RETURN NEXT;
   END LOOP;
 END; $$ language plpgsql;
+-- Create a function to remove arrows from the explain plan
+CREATE OR REPLACE FUNCTION plan_without_arrows(explain_command text, out query_plan text)
+RETURNS SETOF TEXT AS $$
+BEGIN
+  FOR query_plan IN execute explain_command LOOP
+    IF (query_plan LIKE '%->  Result%' OR query_plan = 'Result') THEN
+        CONTINUE;
+    END IF;
+    query_plan := regexp_replace(query_plan, '( )*->  (.*)',  '\2', 'g');
+    RETURN NEXT;
+  END LOOP;
+END; $$ language plpgsql;
 -- helper function that returns true if output of given explain has "is not null" (case in-sensitive)
 CREATE OR REPLACE FUNCTION explain_has_is_not_null(explain_command text)
 RETURNS BOOLEAN AS $$

src/test/regress/sql/columnar_chunk_filtering.sql

@@ -130,11 +130,15 @@ INSERT INTO another_columnar_table SELECT generate_series(0,5);
 EXPLAIN (analyze on, costs off, timing off, summary off)
   SELECT a, y FROM multi_column_chunk_filtering, another_columnar_table WHERE x > 1;
 
+SELECT plan_without_arrows($Q$
 EXPLAIN (costs off, timing off, summary off)
   SELECT y, * FROM another_columnar_table;
+$Q$);
 
+SELECT plan_without_arrows($Q$
 EXPLAIN (costs off, timing off, summary off)
   SELECT *, x FROM another_columnar_table;
+$Q$);
 
 EXPLAIN (costs off, timing off, summary off)
   SELECT y, another_columnar_table FROM another_columnar_table;

src/test/regress/sql/multi_test_helpers.sql

@@ -88,6 +88,19 @@ BEGIN
   END LOOP;
 END; $$ language plpgsql;
 
+-- Create a function to remove arrows from the explain plan
+CREATE OR REPLACE FUNCTION plan_without_arrows(explain_command text, out query_plan text)
+RETURNS SETOF TEXT AS $$
+BEGIN
+  FOR query_plan IN execute explain_command LOOP
+    IF (query_plan LIKE '%->  Result%' OR query_plan = 'Result') THEN
+        CONTINUE;
+    END IF;
+    query_plan := regexp_replace(query_plan, '( )*->  (.*)',  '\2', 'g');
+    RETURN NEXT;
+  END LOOP;
+END; $$ language plpgsql;
+
 -- helper function that returns true if output of given explain has "is not null" (case in-sensitive)
 CREATE OR REPLACE FUNCTION explain_has_is_not_null(explain_command text)
 RETURNS BOOLEAN AS $$