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Avoid repeated decoding of prepared transactions after a restart.

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In commit a271a1b50e, we allowed decoding at prepare time and the prepare
was decoded again if there is a restart after decoding it. It was done
that way because we can't distinguish between the cases where we have not
decoded the prepare because it was prior to consistent snapshot or we have
decoded it earlier but restarted. To distinguish between these two cases,
we have introduced an initial_consistent_point at the slot level which is
an LSN at which we found a consistent point at the time of slot creation.
This is also the point where we have exported a snapshot for the initial
copy. So, prepare transaction prior to this point are sent along with
commit prepared.

This commit bumps SNAPBUILD_VERSION because of change in SnapBuild. It
will break existing slots which is fine in a major release.

Author: Ajin Cherian, based on idea by Andres Freund
Reviewed-by: Amit Kapila and Vignesh C
Discussion: https://postgr.es/m/d0f60d60-133d-bf8d-bd70-47784d8fabf3@enterprisedb.com
This commit is contained in:
Amit Kapila
2021-03-01 09:11:18 +05:30
parent 6230912f23
commit 8bdb1332eb
10 changed files with 61 additions and 67 deletions
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38
contrib/test_decoding/expected/twophase.out
View File

@ -33,14 +33,10 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two
COMMIT PREPARED 'test_prepared#1';
SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
data
----------------------------------------------------
BEGIN
table public.test_prepared1: INSERT: id[integer]:1
table public.test_prepared1: INSERT: id[integer]:2
PREPARE TRANSACTION 'test_prepared#1'
data
-----------------------------------
COMMIT PREPARED 'test_prepared#1'
(5 rows)
(1 row)
-- Test that rollback of a prepared xact is decoded.
BEGIN;
@ -103,13 +99,10 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two
COMMIT PREPARED 'test_prepared#3';
SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
data
-------------------------------------------------------------------------
BEGIN
table public.test_prepared1: INSERT: id[integer]:4 data[text]:'frakbar'
PREPARE TRANSACTION 'test_prepared#3'
data
-----------------------------------
COMMIT PREPARED 'test_prepared#3'
(4 rows)
(1 row)
-- make sure stuff still works
INSERT INTO test_prepared1 VALUES (6);
@ -158,14 +151,10 @@ RESET statement_timeout;
COMMIT PREPARED 'test_prepared_lock';
-- consume the commit
SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
data
---------------------------------------------------------------------------
BEGIN
table public.test_prepared1: INSERT: id[integer]:8 data[text]:'othercol'
table public.test_prepared1: INSERT: id[integer]:9 data[text]:'othercol2'
PREPARE TRANSACTION 'test_prepared_lock'
data
--------------------------------------
COMMIT PREPARED 'test_prepared_lock'
(5 rows)
(1 row)
-- Test savepoints and sub-xacts. Creating savepoints will create
-- sub-xacts implicitly.
@ -188,13 +177,10 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two
COMMIT PREPARED 'test_prepared_savepoint';
-- consume the commit
SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1');
data
------------------------------------------------------------
BEGIN
table public.test_prepared_savepoint: INSERT: a[integer]:1
PREPARE TRANSACTION 'test_prepared_savepoint'
data
-------------------------------------------
COMMIT PREPARED 'test_prepared_savepoint'
(4 rows)
(1 row)
-- Test that a GID containing "_nodecode" gets decoded at commit prepared time.
BEGIN;

28
contrib/test_decoding/expected/twophase_stream.out
View File

@ -60,32 +60,10 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'two-
COMMIT PREPARED 'test1';
--should show the COMMIT PREPARED and the other changes in the transaction
SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL,NULL, 'two-phase-commit', '1', 'include-xids', '0', 'skip-empty-xacts', '1', 'stream-changes', '1');
data
-------------------------------------------------------------
BEGIN
table public.stream_test: INSERT: data[text]:'aaaaaaaaaa1'
table public.stream_test: INSERT: data[text]:'aaaaaaaaaa2'
table public.stream_test: INSERT: data[text]:'aaaaaaaaaa3'
table public.stream_test: INSERT: data[text]:'aaaaaaaaaa4'
table public.stream_test: INSERT: data[text]:'aaaaaaaaaa5'
table public.stream_test: INSERT: data[text]:'aaaaaaaaaa6'
table public.stream_test: INSERT: data[text]:'aaaaaaaaaa7'
table public.stream_test: INSERT: data[text]:'aaaaaaaaaa8'
table public.stream_test: INSERT: data[text]:'aaaaaaaaaa9'
table public.stream_test: INSERT: data[text]:'aaaaaaaaaa10'
table public.stream_test: INSERT: data[text]:'aaaaaaaaaa11'
table public.stream_test: INSERT: data[text]:'aaaaaaaaaa12'
table public.stream_test: INSERT: data[text]:'aaaaaaaaaa13'
table public.stream_test: INSERT: data[text]:'aaaaaaaaaa14'
table public.stream_test: INSERT: data[text]:'aaaaaaaaaa15'
table public.stream_test: INSERT: data[text]:'aaaaaaaaaa16'
table public.stream_test: INSERT: data[text]:'aaaaaaaaaa17'
table public.stream_test: INSERT: data[text]:'aaaaaaaaaa18'
table public.stream_test: INSERT: data[text]:'aaaaaaaaaa19'
table public.stream_test: INSERT: data[text]:'aaaaaaaaaa20'
PREPARE TRANSACTION 'test1'
data
-------------------------
COMMIT PREPARED 'test1'
(23 rows)
(1 row)
-- streaming test with sub-transaction and PREPARE/COMMIT PREPARED but with
-- filtered gid. gids with '_nodecode' will not be decoded at prepare time.