2 files changed, 18 insertions, 3 deletions
diff --git a/src/test/regress/sql/collate.icu.utf8.sql b/src/test/regress/sql/collate.icu.utf8.sql
index 03837de846b..80f28a97d78 100644
--- a/src/test/regress/sql/collate.icu.utf8.sql
+++ b/src/test/regress/sql/collate.icu.utf8.sql
@@ -555,6 +555,7 @@ SELECT x FROM test3cs WHERE x LIKE 'a%';
 SELECT x FROM test3cs WHERE x ILIKE 'a%';
 SELECT x FROM test3cs WHERE x SIMILAR TO 'a%';
 SELECT x FROM test3cs WHERE x ~ 'a';
+SET enable_hashagg TO off;
 SELECT x FROM test1cs UNION SELECT x FROM test2cs ORDER BY x;
 SELECT x FROM test2cs UNION SELECT x FROM test1cs ORDER BY x;
 SELECT x FROM test1cs INTERSECT SELECT x FROM test2cs;
@@ -562,6 +563,7 @@ SELECT x FROM test2cs INTERSECT SELECT x FROM test1cs;
 SELECT x FROM test1cs EXCEPT SELECT x FROM test2cs;
 SELECT x FROM test2cs EXCEPT SELECT x FROM test1cs;
 SELECT DISTINCT x FROM test3cs ORDER BY x;
+RESET enable_hashagg;
 SELECT count(DISTINCT x) FROM test3cs;
 SELECT x, count(*) FROM test3cs GROUP BY x ORDER BY x;
 SELECT x, row_number() OVER (ORDER BY x), rank() OVER (ORDER BY x) FROM test3cs ORDER BY x;
diff --git a/src/test/regress/sql/union.sql b/src/test/regress/sql/union.sql
index d160db54588..8afc580c632 100644
--- a/src/test/regress/sql/union.sql
+++ b/src/test/regress/sql/union.sql
@@ -302,12 +302,12 @@ select except select;
 set enable_hashagg = true;
 set enable_sort = false;
 
-explain (costs off)
-select from generate_series(1,5) union select from generate_series(1,3);
+-- We've no way to check hashed UNION as the empty pathkeys in the Append are
+-- fine to make use of Unique, which is cheaper than HashAggregate and we've
+-- no means to disable Unique.
 explain (costs off)
 select from generate_series(1,5) intersect select from generate_series(1,3);
 
-select from generate_series(1,5) union select from generate_series(1,3);
 select from generate_series(1,5) union all select from generate_series(1,3);
 select from generate_series(1,5) intersect select from generate_series(1,3);
 select from generate_series(1,5) intersect all select from generate_series(1,3);
@@ -330,6 +330,17 @@ select from generate_series(1,5) intersect all select from generate_series(1,3);
 select from generate_series(1,5) except select from generate_series(1,3);
 select from generate_series(1,5) except all select from generate_series(1,3);
 
+-- Try a variation of the above but with a CTE which contains a column, again
+-- with an empty final select list.
+
+-- Ensure we get the expected 1 row with 0 columns
+with cte as materialized (select s from generate_series(1,5) s)
+select from cte union select from cte;
+
+-- Ensure we get the same result as the above.
+with cte as not materialized (select s from generate_series(1,5) s)
+select from cte union select from cte;
+
 reset enable_hashagg;
 reset enable_sort;
 
@@ -361,6 +372,7 @@ INSERT INTO t2 VALUES ('ab'), ('xy');
 set enable_seqscan = off;
 set enable_indexscan = on;
 set enable_bitmapscan = off;
+set enable_sort = off;
 
 explain (costs off)
  SELECT * FROM
@@ -407,6 +419,7 @@ explain (costs off)
 reset enable_seqscan;
 reset enable_indexscan;
 reset enable_bitmapscan;
+reset enable_sort;
 
 -- This simpler variant of the above test has been observed to fail differently