--
-- SELECT_DISTINCT_ON
--
SELECT DISTINCT ON (string4) string4, two, ten
   FROM onek
   ORDER BY string4 using <, two using >, ten using <;
 string4 | two | ten 
---------+-----+-----
 AAAAxx  |   1 |   1
 HHHHxx  |   1 |   1
 OOOOxx  |   1 |   1
 VVVVxx  |   1 |   1
(4 rows)

-- 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 <;
ERROR:  SELECT DISTINCT ON expressions must match initial ORDER BY expressions
LINE 1: SELECT DISTINCT ON (string4, ten) string4, two, ten
                                     ^
SELECT DISTINCT ON (string4, ten) string4, ten, two
   FROM onek
   ORDER BY string4 using <, ten using >, two using <;
 string4 | ten | two 
---------+-----+-----
 AAAAxx  |   9 |   1
 AAAAxx  |   8 |   0
 AAAAxx  |   7 |   1
 AAAAxx  |   6 |   0
 AAAAxx  |   5 |   1
 AAAAxx  |   4 |   0
 AAAAxx  |   3 |   1
 AAAAxx  |   2 |   0
 AAAAxx  |   1 |   1
 AAAAxx  |   0 |   0
 HHHHxx  |   9 |   1
 HHHHxx  |   8 |   0
 HHHHxx  |   7 |   1
 HHHHxx  |   6 |   0
 HHHHxx  |   5 |   1
 HHHHxx  |   4 |   0
 HHHHxx  |   3 |   1
 HHHHxx  |   2 |   0
 HHHHxx  |   1 |   1
 HHHHxx  |   0 |   0
 OOOOxx  |   9 |   1
 OOOOxx  |   8 |   0
 OOOOxx  |   7 |   1
 OOOOxx  |   6 |   0
 OOOOxx  |   5 |   1
 OOOOxx  |   4 |   0
 OOOOxx  |   3 |   1
 OOOOxx  |   2 |   0
 OOOOxx  |   1 |   1
 OOOOxx  |   0 |   0
 VVVVxx  |   9 |   1
 VVVVxx  |   8 |   0
 VVVVxx  |   7 |   1
 VVVVxx  |   6 |   0
 VVVVxx  |   5 |   1
 VVVVxx  |   4 |   0
 VVVVxx  |   3 |   1
 VVVVxx  |   2 |   0
 VVVVxx  |   1 |   1
 VVVVxx  |   0 |   0
(40 rows)

-- 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;
 r |     f1      
---+-------------
 0 | -2147483647
(1 row)

--
-- 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;
            QUERY PLAN            
----------------------------------
 Result
   ->  Limit
         ->  Seq Scan on tenk1
               Filter: (four = 0)
(4 rows)

-- and check the result of the above query is correct
SELECT DISTINCT ON (four) four,two
   FROM tenk1 WHERE four = 0 ORDER BY 1;
 four | two 
------+-----
    0 |   0
(1 row)

-- 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;
            QUERY PLAN            
----------------------------------
 Limit
   ->  Sort
         Sort Key: two
         ->  Seq Scan on tenk1
               Filter: (four = 0)
(5 rows)

-- 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;
                     QUERY PLAN                      
-----------------------------------------------------
 Result
   ->  Limit
         ->  Index Scan using tenk1_hundred on tenk1
               Filter: (four = 0)
(4 rows)