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postgres_fdw: When sending ORDER BY, always include NULLS FIRST/LAST.

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Previously, we included NULLS FIRST when appropriate but relied on the
default behavior to be NULLS LAST.  This is, however, not true for a
sort in descending order and seems like a fragile assumption anyway.

Report by Rajkumar Raghuwanshi.  Patch by Ashutosh Bapat.  Review
comments from Michael Paquier and Tom Lane.
This commit is contained in:
Robert Haas
2016-03-04 11:35:46 -05:00
parent 52fe6f4e02
commit 3bea3f88d5
3 changed files with 125 additions and 31 deletions
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12
contrib/postgres_fdw/sql/postgres_fdw.sql
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@ -677,6 +677,18 @@ commit;
select c2, count(*) from ft2 where c2 < 500 group by 1 order by 1;
select c2, count(*) from "S 1"."T 1" where c2 < 500 group by 1 order by 1;
-- Above DMLs add data with c6 as NULL in ft1, so test ORDER BY NULLS LAST and NULLs
-- FIRST behavior here.
-- ORDER BY DESC NULLS LAST options
EXPLAIN (VERBOSE, COSTS false) SELECT * FROM ft1 ORDER BY c6 DESC NULLS LAST, c1 OFFSET 795 LIMIT 10;
SELECT * FROM ft1 ORDER BY c6 DESC NULLS LAST, c1 OFFSET 795 LIMIT 10;
-- ORDER BY DESC NULLS FIRST options
EXPLAIN (VERBOSE, COSTS false) SELECT * FROM ft1 ORDER BY c6 DESC NULLS FIRST, c1 OFFSET 15 LIMIT 10;
SELECT * FROM ft1 ORDER BY c6 DESC NULLS FIRST, c1 OFFSET 15 LIMIT 10;
-- ORDER BY ASC NULLS FIRST options
EXPLAIN (VERBOSE, COSTS false) SELECT * FROM ft1 ORDER BY c6 ASC NULLS FIRST, c1 OFFSET 15 LIMIT 10;
SELECT * FROM ft1 ORDER BY c6 ASC NULLS FIRST, c1 OFFSET 15 LIMIT 10;
-- ===================================================================
-- test check constraints
-- ===================================================================