1 files changed, 44 insertions, 0 deletions
diff --git a/src/test/regress/sql/select_distinct_on.sql b/src/test/regress/sql/select_distinct_on.sql
new file mode 100644
index 0000000..261e614
--- /dev/null
+++ b/src/test/regress/sql/select_distinct_on.sql
@@ -0,0 +1,44 @@
+--
+-- SELECT_DISTINCT_ON
+--
+
+SELECT DISTINCT ON (string4) string4, two, ten
+   FROM onek
+   ORDER BY string4 using <, two using >, ten using <;
+
+-- this will fail due to conflict of ordering requirements
+SELECT DISTINCT ON (string4, ten) string4, two, ten
+   FROM onek
+   ORDER BY string4 using <, two using <, ten using <;
+
+SELECT DISTINCT ON (string4, ten) string4, ten, two
+   FROM onek
+   ORDER BY string4 using <, ten using >, two using <;
+
+-- bug #5049: early 8.4.x chokes on volatile DISTINCT ON clauses
+select distinct on (1) floor(random()) as r, f1 from int4_tbl order by 1,2;
+
+--
+-- Test the planner's ability to use a LIMIT 1 instead of a Unique node when
+-- all of the distinct_pathkeys have been marked as redundant
+--
+
+-- Ensure we also get a LIMIT plan with DISTINCT ON
+EXPLAIN (COSTS OFF)
+SELECT DISTINCT ON (four) four,two
+   FROM tenk1 WHERE four = 0 ORDER BY 1;
+
+-- and check the result of the above query is correct
+SELECT DISTINCT ON (four) four,two
+   FROM tenk1 WHERE four = 0 ORDER BY 1;
+
+-- Ensure a Sort -> Limit is used when the ORDER BY contains additional cols
+EXPLAIN (COSTS OFF)
+SELECT DISTINCT ON (four) four,two
+   FROM tenk1 WHERE four = 0 ORDER BY 1,2;
+
+-- Same again but use a column that is indexed so that we get an index scan
+-- then a limit
+EXPLAIN (COSTS OFF)
+SELECT DISTINCT ON (four) four,hundred
+   FROM tenk1 WHERE four = 0 ORDER BY 1,2;