Teach predtest.c about CHECK clauses to fix partitioning bugs.

In a CHECK clause, a null result means true, whereas in a WHERE clause
it means false.  predtest.c provided different functions depending on
which set of semantics applied to the predicate being proved, but had
no option to control what a null meant in the clauses provided as
axioms.  Add one.

Use that in the partitioning code when figuring out whether the
validation scan on a new partition can be skipped.  Rip out the
old logic that attempted (not very successfully) to compensate
for the absence of the necessary support in predtest.c.

Ashutosh Bapat and Robert Haas, reviewed by Amit Langote and
incorporating feedback from Tom Lane.

Discussion: http://postgr.es/m/CAFjFpReT_kq_uwU_B8aWDxR7jNGE=P0iELycdq5oupi=xSQTOw@mail.gmail.com

2 files changed, 12 insertions, 1 deletions

diff --git a/src/test/regress/expected/alter_table.out b/src/test/regress/expected/alter_table.out
index d4dbe650a32..13d6a4b7478 100644
--- a/src/test/regress/expected/alter_table.out
+++ b/src/test/regress/expected/alter_table.out
@@ -3338,6 +3338,12 @@ ALTER TABLE list_parted2 ATTACH PARTITION part_5 FOR VALUES IN (5);
 ERROR:  partition constraint is violated by some row
 -- delete the faulting row and also add a constraint to skip the scan
 DELETE FROM part_5_a WHERE a NOT IN (3);
+ALTER TABLE part_5 ADD CONSTRAINT check_a CHECK (a IS NOT NULL AND a = 5);
+ALTER TABLE list_parted2 ATTACH PARTITION part_5 FOR VALUES IN (5);
+INFO:  partition constraint for table "part_5" is implied by existing constraints
+ALTER TABLE list_parted2 DETACH PARTITION part_5;
+ALTER TABLE part_5 DROP CONSTRAINT check_a;
+-- scan should again be skipped, even though NOT NULL is now a column property
 ALTER TABLE part_5 ADD CONSTRAINT check_a CHECK (a IN (5)), ALTER a SET NOT NULL;
 ALTER TABLE list_parted2 ATTACH PARTITION part_5 FOR VALUES IN (5);
 INFO:  partition constraint for table "part_5" is implied by existing constraints
diff --git a/src/test/regress/sql/alter_table.sql b/src/test/regress/sql/alter_table.sql
index 001717d91ce..5dd1402ea6f 100644
--- a/src/test/regress/sql/alter_table.sql
+++ b/src/test/regress/sql/alter_table.sql
@@ -2169,9 +2169,14 @@ ALTER TABLE list_parted2 ATTACH PARTITION part_5 FOR VALUES IN (5);
 
 -- delete the faulting row and also add a constraint to skip the scan
 DELETE FROM part_5_a WHERE a NOT IN (3);
-ALTER TABLE part_5 ADD CONSTRAINT check_a CHECK (a IN (5)), ALTER a SET NOT NULL;
+ALTER TABLE part_5 ADD CONSTRAINT check_a CHECK (a IS NOT NULL AND a = 5);
 ALTER TABLE list_parted2 ATTACH PARTITION part_5 FOR VALUES IN (5);
+ALTER TABLE list_parted2 DETACH PARTITION part_5;
+ALTER TABLE part_5 DROP CONSTRAINT check_a;
 
+-- scan should again be skipped, even though NOT NULL is now a column property
+ALTER TABLE part_5 ADD CONSTRAINT check_a CHECK (a IN (5)), ALTER a SET NOT NULL;
+ALTER TABLE list_parted2 ATTACH PARTITION part_5 FOR VALUES IN (5);
 
 -- check that the table being attached is not already a partition
 ALTER TABLE list_parted2 ATTACH PARTITION part_2 FOR VALUES IN (2);