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Commits from this thread:
2026-01-20 30776ca468 Remove redundant pg_unreachable() after elog(ERROR) from ExecWaitStmt()
* pgsql: Add the MODE option to the WAIT FOR LSN command
@ 2026-01-05 17:56 Alexander Korotkov <akorotkov@postgresql.org>
2026-01-19 16:26 ` Re: pgsql: Add the MODE option to the WAIT FOR LSN command Peter Eisentraut <peter@eisentraut.org>
0 siblings, 1 reply; 2+ messages in thread
From: Alexander Korotkov @ 2026-01-05 17:56 UTC (permalink / raw)
To: pgsql-committers@lists.postgresql.org
Add the MODE option to the WAIT FOR LSN command
This commit extends the WAIT FOR LSN command with an optional MODE option in
the WITH clause that specifies which LSN type to wait for:
WAIT FOR LSN '<lsn>' [WITH (MODE '<mode>', ...)]
where mode can be:
- 'standby_replay' (default): Wait for WAL to be replayed to the specified
LSN,
- 'standby_write': Wait for WAL to be written (received) to the specified
LSN,
- 'standby_flush': Wait for WAL to be flushed to disk at the specified LSN,
- 'primary_flush': Wait for WAL to be flushed to disk on the primary server.
The default mode is 'standby_replay', matching the original behavior when MODE
is not specified. This follows the pattern used by COPY and EXPLAIN
commands, where options are specified as string values in the WITH clause.
Modes are explicitly named to distinguish between primary and standby
operations:
- Standby modes ('standby_replay', 'standby_write', 'standby_flush') can only
be used during recovery (on a standby server),
- Primary mode ('primary_flush') can only be used on a primary server.
The 'standby_write' and 'standby_flush' modes are useful for scenarios where
applications need to ensure WAL has been received or persisted on the standby
without necessarily waiting for replay to complete. The 'primary_flush' mode
allows waiting for WAL to be flushed on the primary server.
This commit also includes includes:
- Documentation updates for the new syntax and mode descriptions,
- Test coverage for all four modes, including error cases and concurrent
waiters,
- Wakeup logic in walreceiver for standby write/flush waiters,
- Wakeup logic in WAL writer for primary flush waiters.
Discussion: https://postgr.es/m/CABPTF7UiArgW-sXj9CNwRzUhYOQrevLzkYcgBydmX5oDes1sjg%40mail.gmail.com
Author: Xuneng Zhou <xunengzhou@gmail.com>
Reviewed-by: Alexander Korotkov <aekorotkov@gmail.com>
Reviewed-by: Chao Li <li.evan.chao@gmail.com>
Reviewed-by: Alvaro Herrera <alvherre@kurilemu.de>
Branch
------
master
Details
-------
https://git.postgresql.org/pg/commitdiff/49a181b5d634340fcfb7c762c387c03f6405367e
Modified Files
--------------
doc/src/sgml/ref/wait_for.sgml | 213 +++++++++++++----
src/backend/access/transam/xlog.c | 22 +-
src/backend/commands/wait.c | 174 ++++++++++++--
src/backend/replication/walreceiver.c | 18 ++
src/test/recovery/t/049_wait_for_lsn.pl | 411 +++++++++++++++++++++++++++++---
5 files changed, 741 insertions(+), 97 deletions(-)
^ permalink raw reply [nested|flat] 2+ messages in thread
* Re: pgsql: Add the MODE option to the WAIT FOR LSN command
2026-01-05 17:56 pgsql: Add the MODE option to the WAIT FOR LSN command Alexander Korotkov <akorotkov@postgresql.org>
@ 2026-01-19 16:26 ` Peter Eisentraut <peter@eisentraut.org>
0 siblings, 0 replies; 2+ messages in thread
From: Peter Eisentraut @ 2026-01-19 16:26 UTC (permalink / raw)
To: Alexander Korotkov <akorotkov@postgresql.org>; pgsql-committers@lists.postgresql.org
On 05.01.26 18:56, Alexander Korotkov wrote:
> Add the MODE option to the WAIT FOR LSN command
> Details
> -------
> https://git.postgresql.org/pg/commitdiff/49a181b5d634340fcfb7c762c387c03f6405367e
>
> Modified Files
> --------------
> doc/src/sgml/ref/wait_for.sgml | 213 +++++++++++++----
> src/backend/access/transam/xlog.c | 22 +-
> src/backend/commands/wait.c | 174 ++++++++++++--
> src/backend/replication/walreceiver.c | 18 ++
> src/test/recovery/t/049_wait_for_lsn.pl | 411 +++++++++++++++++++++++++++++---
> 5 files changed, 741 insertions(+), 97 deletions(-)
This patch adds several instances in src/backend/commands/wait.c where
an elog(ERROR) is followed immediately by pg_unreachable(). I think
this is redundant. I think this pattern has been used historically in
functions that return non-void where the elog(ERROR) is the last call,
to avoid warnings about a missing return. But in this case, the
function returns void. Check please if this is really necessary or just
copy-and-pasted.
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2026-01-05 17:56 pgsql: Add the MODE option to the WAIT FOR LSN command Alexander Korotkov <akorotkov@postgresql.org>
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