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Don't propagate a null subtransaction snapshot up to parent transaction.

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This oversight could cause logical decoding to fail to decode an outer
transaction containing changes, if a subtransaction had an XID but no
actual changes.  Per bug #14279 from Marko Tiikkaja.  Patch by Marko
based on analysis by Andrew Gierth.

Discussion: <20160804191757.1430.39011@wrigleys.postgresql.org>
This commit is contained in:
Tom Lane 2016-08-07 13:15:55 -04:00
parent 3676631c68
commit bcbecbce2f
3 changed files with 40 additions and 6 deletions
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24
contrib/test_decoding/expected/xact.out
View File

@ -6,9 +6,9 @@ SELECT 'init' FROM pg_create_logical_replication_slot('regression_slot', 'test_d
init
(1 row)
-- bug #13844, xids in non-decoded records need to be inspected
CREATE TABLE xact_test(data text);
INSERT INTO xact_test VALUES ('before-test');
-- bug #13844, xids in non-decoded records need to be inspected
BEGIN;
-- perform operation in xact that creates and logs xid, but isn't decoded
SELECT * FROM xact_test FOR UPDATE;
@ -33,6 +33,28 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'inc
COMMIT
(6 rows)
-- bug #14279, do not propagate null snapshot from subtransaction
BEGIN;
-- first insert
INSERT INTO xact_test VALUES ('main-txn');
SAVEPOINT foo;
-- now perform operation in subxact that creates and logs xid, but isn't decoded
SELECT 1 FROM xact_test FOR UPDATE LIMIT 1;
?column?
----------
1
(1 row)
COMMIT;
-- and now show those changes
SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
data
-------------------------------------------------------
BEGIN
table public.xact_test: INSERT: data[text]:'main-txn'
COMMIT
(3 rows)
DROP TABLE xact_test;
SELECT pg_drop_replication_slot('regression_slot');
pg_drop_replication_slot

13
contrib/test_decoding/sql/xact.sql
View File

@ -3,10 +3,10 @@ SET synchronous_commit = on;
SELECT 'init' FROM pg_create_logical_replication_slot('regression_slot', 'test_decoding');
-- bug #13844, xids in non-decoded records need to be inspected
CREATE TABLE xact_test(data text);
INSERT INTO xact_test VALUES ('before-test');
-- bug #13844, xids in non-decoded records need to be inspected
BEGIN;
-- perform operation in xact that creates and logs xid, but isn't decoded
SELECT * FROM xact_test FOR UPDATE;
@ -17,6 +17,17 @@ COMMIT;
-- and now show those changes
SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
-- bug #14279, do not propagate null snapshot from subtransaction
BEGIN;
-- first insert
INSERT INTO xact_test VALUES ('main-txn');
SAVEPOINT foo;
-- now perform operation in subxact that creates and logs xid, but isn't decoded
SELECT 1 FROM xact_test FOR UPDATE LIMIT 1;
COMMIT;
-- and now show those changes
SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
DROP TABLE xact_test;
SELECT pg_drop_replication_slot('regression_slot');

9
src/backend/replication/logical/reorderbuffer.c
View File

@ -807,13 +807,14 @@ ReorderBufferCommitChild(ReorderBuffer *rb, TransactionId xid,
elog(ERROR, "subxact logged without previous toplevel record");
/*
* Pass the our base snapshot to the parent transaction if it doesn't have
* Pass our base snapshot to the parent transaction if it doesn't have
* one, or ours is older. That can happen if there are no changes in the
* toplevel transaction but in one of the child transactions. This allows
* the parent to simply use it's base snapshot initially.
* the parent to simply use its base snapshot initially.
*/
if (txn->base_snapshot == NULL ||
txn->base_snapshot_lsn > subtxn->base_snapshot_lsn)
if (subtxn->base_snapshot != NULL &&
(txn->base_snapshot == NULL ||
txn->base_snapshot_lsn > subtxn->base_snapshot_lsn))
{
txn->base_snapshot = subtxn->base_snapshot;
txn->base_snapshot_lsn = subtxn->base_snapshot_lsn;