From 297d627e074ad4aa2a9936b029a4b9231f9a150e Mon Sep 17 00:00:00 2001 From: Andres Freund Date: Wed, 6 Feb 2019 01:09:32 -0800 Subject: [PATCH] Fix heap_getattr() handling of fast defaults. Previously heap_getattr() returned NULL for attributes with a fast default value (c.f. 16828d5c0273), as it had no handling whatsoever for that case. A previous fix, 7636e5c60f, attempted to fix issues caused by this oversight, but just expanding OLD tuples for triggers doesn't actually solve the underlying issue. One known consequence of this bug is that the check for HOT updates can return the wrong result, when a previously fast-default'ed column is set to NULL. Which in turn means that an index over a column with fast default'ed columns might be corrupt if the underlying column(s) allow NULLs. Fix by handling fast default columns in heap_getattr(), remove now superfluous expansion in GetTupleForTrigger(). Author: Andres Freund Discussion: https://postgr.es/m/20190201162404.onngi77f26baem4g@alap3.anarazel.de Backpatch: 11, where fast defaults were introduced --- src/backend/access/common/heaptuple.c | 2 +- src/backend/commands/trigger.c | 5 +--- src/include/access/htup_details.h | 7 +++--- src/test/regress/expected/fast_default.out | 27 ++++++++++++++++++++++ src/test/regress/sql/fast_default.sql | 20 ++++++++++++++++ 5 files changed, 52 insertions(+), 9 deletions(-) diff --git a/src/backend/access/common/heaptuple.c b/src/backend/access/common/heaptuple.c index 5f34b26a2c..1d03b7dd13 100644 --- a/src/backend/access/common/heaptuple.c +++ b/src/backend/access/common/heaptuple.c @@ -80,7 +80,7 @@ /* * Return the missing value of an attribute, or NULL if there isn't one. */ -static Datum +Datum getmissingattr(TupleDesc tupleDesc, int attnum, bool *isnull) { diff --git a/src/backend/commands/trigger.c b/src/backend/commands/trigger.c index a0cc82c2a3..d7ffc9c3e2 100644 --- a/src/backend/commands/trigger.c +++ b/src/backend/commands/trigger.c @@ -3396,10 +3396,7 @@ ltrmark:; LockBuffer(buffer, BUFFER_LOCK_UNLOCK); } - if (HeapTupleHeaderGetNatts(tuple.t_data) < relation->rd_att->natts) - result = heap_expand_tuple(&tuple, relation->rd_att); - else - result = heap_copytuple(&tuple); + result = heap_copytuple(&tuple); ReleaseBuffer(buffer); return result; diff --git a/src/include/access/htup_details.h b/src/include/access/htup_details.h index 1867a70f6f..bc61bc8a8e 100644 --- a/src/include/access/htup_details.h +++ b/src/include/access/htup_details.h @@ -783,10 +783,7 @@ extern Datum fastgetattr(HeapTuple tup, int attnum, TupleDesc tupleDesc, ((attnum) > 0) ? \ ( \ ((attnum) > (int) HeapTupleHeaderGetNatts((tup)->t_data)) ? \ - ( \ - (*(isnull) = true), \ - (Datum)NULL \ - ) \ + getmissingattr((tupleDesc), (attnum), (isnull)) \ : \ fastgetattr((tup), (attnum), (tupleDesc), (isnull)) \ ) \ @@ -807,6 +804,8 @@ extern Datum nocachegetattr(HeapTuple tup, int attnum, TupleDesc att); extern Datum heap_getsysattr(HeapTuple tup, int attnum, TupleDesc tupleDesc, bool *isnull); +extern Datum getmissingattr(TupleDesc tupleDesc, + int attnum, bool *isnull); extern HeapTuple heap_copytuple(HeapTuple tuple); extern void heap_copytuple_with_tuple(HeapTuple src, HeapTuple dest); extern Datum heap_copy_tuple_as_datum(HeapTuple tuple, TupleDesc tupleDesc); diff --git a/src/test/regress/expected/fast_default.out b/src/test/regress/expected/fast_default.out index 40a15bd2d6..10bc5ff757 100644 --- a/src/test/regress/expected/fast_default.out +++ b/src/test/regress/expected/fast_default.out @@ -770,6 +770,33 @@ SELECT * FROM vtype2; 2 | yyy (2 rows) +-- Ensure that defaults are checked when evaluating whether HOT update +-- is possible, this was broken for a while: +-- https://postgr.es/m/20190202133521.ylauh3ckqa7colzj%40alap3.anarazel.de +BEGIN; +CREATE TABLE t(); +INSERT INTO t DEFAULT VALUES; +ALTER TABLE t ADD COLUMN a int DEFAULT 1; +CREATE INDEX ON t(a); +-- set column with a default 1 to NULL, due to a bug that wasn't +-- noticed has heap_getattr buggily returned NULL for default columns +UPDATE t SET a = NULL; +-- verify that index and non-index scans show the same result +SET LOCAL enable_seqscan = true; +SELECT * FROM t WHERE a IS NULL; + a +--- + +(1 row) + +SET LOCAL enable_seqscan = false; +SELECT * FROM t WHERE a IS NULL; + a +--- + +(1 row) + +ROLLBACK; -- cleanup DROP TABLE vtype; DROP TABLE vtype2; diff --git a/src/test/regress/sql/fast_default.sql b/src/test/regress/sql/fast_default.sql index 0f65a79c7f..4589b9e58d 100644 --- a/src/test/regress/sql/fast_default.sql +++ b/src/test/regress/sql/fast_default.sql @@ -505,6 +505,26 @@ ALTER TABLE vtype2 ALTER COLUMN b TYPE varchar(20) USING b::varchar(20); SELECT * FROM vtype2; +-- Ensure that defaults are checked when evaluating whether HOT update +-- is possible, this was broken for a while: +-- https://postgr.es/m/20190202133521.ylauh3ckqa7colzj%40alap3.anarazel.de +BEGIN; +CREATE TABLE t(); +INSERT INTO t DEFAULT VALUES; +ALTER TABLE t ADD COLUMN a int DEFAULT 1; +CREATE INDEX ON t(a); +-- set column with a default 1 to NULL, due to a bug that wasn't +-- noticed has heap_getattr buggily returned NULL for default columns +UPDATE t SET a = NULL; + +-- verify that index and non-index scans show the same result +SET LOCAL enable_seqscan = true; +SELECT * FROM t WHERE a IS NULL; +SET LOCAL enable_seqscan = false; +SELECT * FROM t WHERE a IS NULL; +ROLLBACK; + + -- cleanup DROP TABLE vtype; DROP TABLE vtype2;