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Generic Messages for Logical Decoding

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API and mechanism to allow generic messages to be inserted into WAL that are
intended to be read by logical decoding plugins. This commit adds an optional
new callback to the logical decoding API.

Messages are either text or bytea. Messages can be transactional, or not, and
are identified by a prefix to allow multiple concurrent decoding plugins.

(Not to be confused with Generic WAL records, which are intended to allow crash
recovery of extensible objects.)

Author: Petr Jelinek and Andres Freund
Reviewers: Artur Zakirov, Tomas Vondra, Simon Riggs
Discussion: 5685F999.6010202@2ndquadrant.com
This commit is contained in:
Simon Riggs
2016-04-06 10:05:41 +01:00
parent 989be0810d
commit 3fe3511d05
27 changed files with 693 additions and 33 deletions
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21
contrib/test_decoding/expected/ddl.out
View File

@ -220,11 +220,17 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'inc
(7 rows)
/*
* check that disk spooling works
* check that disk spooling works (also for logical messages)
*/
BEGIN;
CREATE TABLE tr_etoomuch (id serial primary key, data int);
INSERT INTO tr_etoomuch(data) SELECT g.i FROM generate_series(1, 10234) g(i);
SELECT 'tx logical msg' FROM pg_logical_emit_message(true, 'test', 'tx logical msg');
?column?
----------------
tx logical msg
(1 row)
DELETE FROM tr_etoomuch WHERE id < 5000;
UPDATE tr_etoomuch SET data = - data WHERE id > 5000;
COMMIT;
@ -233,12 +239,13 @@ SELECT count(*), min(data), max(data)
FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1')
GROUP BY substring(data, 1, 24)
ORDER BY 1,2;
count | min | max
-------+-------------------------------------------------+------------------------------------------------------------------------
1 | BEGIN | BEGIN
1 | COMMIT | COMMIT
20467 | table public.tr_etoomuch: DELETE: id[integer]:1 | table public.tr_etoomuch: UPDATE: id[integer]:9999 data[integer]:-9999
(3 rows)
count | min | max
-------+-----------------------------------------------------------------------+------------------------------------------------------------------------
1 | BEGIN | BEGIN
1 | COMMIT | COMMIT
1 | message: transactional: 1 prefix: test, sz: 14 content:tx logical msg | message: transactional: 1 prefix: test, sz: 14 content:tx logical msg
20467 | table public.tr_etoomuch: DELETE: id[integer]:1 | table public.tr_etoomuch: UPDATE: id[integer]:9999 data[integer]:-9999
(4 rows)
-- check updates of primary keys work correctly
BEGIN;

79
contrib/test_decoding/expected/messages.out Normal file
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@ -0,0 +1,79 @@
-- predictability
SET synchronous_commit = on;
SET client_encoding = 'utf8';
SELECT 'init' FROM pg_create_logical_replication_slot('regression_slot', 'test_decoding');
?column?
----------
init
(1 row)
SELECT 'msg1' FROM pg_logical_emit_message(true, 'test', 'msg1');
?column?
----------
msg1
(1 row)
SELECT 'msg2' FROM pg_logical_emit_message(false, 'test', 'msg2');
?column?
----------
msg2
(1 row)
BEGIN;
SELECT 'msg3' FROM pg_logical_emit_message(true, 'test', 'msg3');
?column?
----------
msg3
(1 row)
SELECT 'msg4' FROM pg_logical_emit_message(false, 'test', 'msg4');
?column?
----------
msg4
(1 row)
ROLLBACK;
BEGIN;
SELECT 'msg5' FROM pg_logical_emit_message(true, 'test', 'msg5');
?column?
----------
msg5
(1 row)
SELECT 'msg6' FROM pg_logical_emit_message(false, 'test', 'msg6');
?column?
----------
msg6
(1 row)
SELECT 'msg7' FROM pg_logical_emit_message(true, 'test', 'msg7');
?column?
----------
msg7
(1 row)
COMMIT;
SELECT 'žluťoučký kůň' FROM pg_logical_emit_message(true, 'test', 'žluťoučký kůň');
?column?
---------------
žluťoučký kůň
(1 row)
SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'force-binary', '0', 'skip-empty-xacts', '1');
data
----------------------------------------------------------------------
message: transactional: 1 prefix: test, sz: 4 content:msg1
message: transactional: 0 prefix: test, sz: 4 content:msg2
message: transactional: 0 prefix: test, sz: 4 content:msg4
message: transactional: 0 prefix: test, sz: 4 content:msg6
message: transactional: 1 prefix: test, sz: 4 content:msg5
message: transactional: 1 prefix: test, sz: 4 content:msg7
message: transactional: 1 prefix: test, sz: 19 content:žluťoučký kůň
(7 rows)
SELECT 'init' FROM pg_drop_replication_slot('regression_slot');
?column?
----------
init
(1 row)