Re: [HACKERS] logical decoding of two-phase transactions

Did some further tests on the problem I saw and I see that it does not
have anything to do with this patch. I picked code from top of head.
If I have enough changes in a transaction to initiate streaming, then
it will also stream the same changes after a commit.

BEGIN;
INSERT INTO stream_test SELECT repeat('a', 10) || g.i FROM
generate_series(1,800) g(i);
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');
** see streamed output here **
END;
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');
** see the same streamed output here **

I think this is because since the transaction has not been committed,
SnapBuildCommitTxn is not called which is what moves the
"builder->start_decoding_at", and as a result
later calls to pg_logical_slot_get_changes will start from the
previous lsn. I did do a quick test in pgoutput using pub/sub and I
dont see duplication of data there but I haven't
verified exactly what happens.

regards,
Ajin Cherian
Fujitsu Australia