0002-Teach-ATExecAttachPartition-to-skip-validation-in-mo.patch

From a7d0d781bd9e3730f90d902d0e09abf79962f872 Mon Sep 17 00:00:00 2001
From: amit <amitlangote09@gmail.com>
Date: Mon, 7 Aug 2017 10:51:47 +0900
Subject: [PATCH 2/2] Teach ATExecAttachPartition to skip validation in more
 cases

In cases where the table being attached is a partitioned table and
the table itself does not have constraints that would allow validation
on the whole table to be skipped, we can still skip the validations
of individual partitions if they each happen to have the requisite
constraints.

Per an idea of Robert Haas', with code refactoring suggestions from
Ashutosh Bapat.
---
 src/backend/commands/tablecmds.c          | 10 ++++++++++
 src/test/regress/expected/alter_table.out | 13 +++++++++++++
 src/test/regress/sql/alter_table.sql      | 10 ++++++++++
 3 files changed, 33 insertions(+)

diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c
index 563bcda30c..901eea7fe2 100644
--- a/src/backend/commands/tablecmds.c
+++ b/src/backend/commands/tablecmds.c
@@ -13678,6 +13678,16 @@ ValidatePartitionConstraints(List **wqueue, Relation scanrel,
 			/* There can never be a whole-row reference here */
 			if (found_whole_row)
 				elog(ERROR, "unexpected whole-row reference found in partition key");
+
+			/* Check if we can we skip scanning this part_rel. */
+			if (PartConstraintImpliedByRelConstraint(part_rel, my_partconstr))
+			{
+				ereport(INFO,
+						(errmsg("partition constraint for table \"%s\" is implied by existing constraints",
+								RelationGetRelationName(part_rel))));
+				heap_close(part_rel, NoLock);
+				continue;
+			}
 		}
 
 		/* Grab a work queue entry. */
diff --git a/src/test/regress/expected/alter_table.out b/src/test/regress/expected/alter_table.out
index 0478a8ac60..e3415837b6 100644
--- a/src/test/regress/expected/alter_table.out
+++ b/src/test/regress/expected/alter_table.out
@@ -3464,6 +3464,19 @@ ERROR:  updated partition constraint for default partition would be violated by
 -- should be ok after deleting the bad row
 DELETE FROM part5_def_p1 WHERE b = 'y';
 ALTER TABLE part_5 ATTACH PARTITION part5_p1 FOR VALUES IN ('y');
+-- If the partitioned table being attached does not have a constraint that
+-- would allow validation scan to be skipped, but an individual partition
+-- does, then the partition's validation scan is skipped.  Note that the
+-- following leaf partition only allows rows that have a = 7 (and b = 'b' but
+-- that's irrelevant).
+CREATE TABLE part_7_b PARTITION OF part_7 (
+	CONSTRAINT check_a CHECK (a IS NOT NULL AND a = 7)
+) FOR VALUES IN ('b');
+-- The faulting row in part_7_a_null will still cause the command to fail
+ALTER TABLE list_parted2 ATTACH PARTITION part_7 FOR VALUES IN (7);
+INFO:  partition constraint for table "part_7_b" is implied by existing constraints
+INFO:  partition constraint for table "list_parted2_def" is implied by existing constraints
+ERROR:  partition constraint is violated by some row
 -- check that the table being attached is not already a partition
 ALTER TABLE list_parted2 ATTACH PARTITION part_2 FOR VALUES IN (2);
 ERROR:  "part_2" is already a partition
diff --git a/src/test/regress/sql/alter_table.sql b/src/test/regress/sql/alter_table.sql
index 37cca72620..d296314ca9 100644
--- a/src/test/regress/sql/alter_table.sql
+++ b/src/test/regress/sql/alter_table.sql
@@ -2277,6 +2277,16 @@ ALTER TABLE part_5 ATTACH PARTITION part5_p1 FOR VALUES IN ('y');
 -- should be ok after deleting the bad row
 DELETE FROM part5_def_p1 WHERE b = 'y';
 ALTER TABLE part_5 ATTACH PARTITION part5_p1 FOR VALUES IN ('y');
+-- If the partitioned table being attached does not have a constraint that
+-- would allow validation scan to be skipped, but an individual partition
+-- does, then the partition's validation scan is skipped.  Note that the
+-- following leaf partition only allows rows that have a = 7 (and b = 'b' but
+-- that's irrelevant).
+CREATE TABLE part_7_b PARTITION OF part_7 (
+	CONSTRAINT check_a CHECK (a IS NOT NULL AND a = 7)
+) FOR VALUES IN ('b');
+-- The faulting row in part_7_a_null will still cause the command to fail
+ALTER TABLE list_parted2 ATTACH PARTITION part_7 FOR VALUES IN (7);
 
 -- check that the table being attached is not already a partition
 ALTER TABLE list_parted2 ATTACH PARTITION part_2 FOR VALUES IN (2);
-- 
2.11.0