postgrespro.git / summary / log / commit / refs
commit 171e0418b03dc103d5d9bdc0bfaadbb193dd7fd6
Author: Andres Freund <andres@anarazel.de>
Date: Wed Feb 06 09:09:32 2019 +0000
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 | 4 +---
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(+), 11 deletions(-)
diff --git a/src/backend/access/common/heaptuple.c b/src/backend/access/common/heaptuple.c
index ed4549ca57..783b04a3cb 100644
--- a/src/backend/access/common/heaptuple.c
+++ b/src/backend/access/common/heaptuple.c
@@ -71,8 +71,6 @@
#define VARLENA_ATT_IS_PACKABLE(att) \
((att)->attstorage != 'p')
-static Datum getmissingattr(TupleDesc tupleDesc, int attnum, bool *isnull);
-
/* ----------------------------------------------------------------
* misc support routines
@@ -82,7 +80,7 @@ static Datum getmissingattr(TupleDesc tupleDesc, int attnum, bool *isnull);
/*
* 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 7b5896b98f..0b245a613e 100644
--- a/src/backend/commands/trigger.c
+++ b/src/backend/commands/trigger.c
@@ -3412,10 +3412,7 @@ 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 873a3015fc..6d51f9062b 100644
--- a/src/include/access/htup_details.h
+++ b/src/include/access/htup_details.h
@@ -764,10 +764,7 @@ 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)) \
) \
@@ -788,6 +785,8 @@ 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;
[parent: d07fb6810e51]