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base repository: postgresql-cfbot/postgresql
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  • 5 commits
  • 11 files changed
  • 2 contributors

Commits on Dec 26, 2025

  1. Extend xlogwait infrastructure with write and flush wait types 

    Add support for waiting on WAL write and flush LSNs in addition to the
existing replay LSN wait type. This provides the foundation for
extending the WAIT FOR command with MODE option.

Key changes:
- Add WAIT_LSN_TYPE_STANDBY_WRITE and WAIT_LSN_TYPE_STANDBY_FLUSH to WaitLSNType
- Add GetCurrentLSNForWaitType() to retrieve current LSN for each wait type
- Add new wait events WAIT_EVENT_WAIT_FOR_WAL_WRITE and
  WAIT_EVENT_WAIT_FOR_WAL_FLUSH for pg_stat_activity visibility
- Update WaitForLSN() to use GetCurrentLSNForWaitType() internally
    @alterego655
    alterego655 authored and Commitfest Bot committed Dec 26, 2025
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  2. Add MODE option to WAIT FOR LSN command 

    Extend 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.

Also 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
    @alterego655
    alterego655 authored and Commitfest Bot committed Dec 26, 2025
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  3. Add tab completion for WAIT FOR LSN MODE option 

    Update psql tab completion to support the optional MODE option in
WAIT FOR LSN command. After specifying an LSN value, completion now
offers both MODE and WITH keywords. The MODE option controls whether
the wait is evaluated from the standby or primary perspective.

When MODE is specified, completion suggests the valid mode values:
standby_replay, standby_write, standby_flush, and primary_flush.
    @alterego655
    alterego655 authored and Commitfest Bot committed Dec 26, 2025
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  4. Use WAIT FOR LSN in PostgreSQL::Test::Cluster::wait_for_catchup() 

    When the standby is passed as a PostgreSQL::Test::Cluster instance,
use the WAIT FOR LSN command on the standby server to implement
wait_for_catchup() for replay, write, and flush modes.  This is more
efficient than polling pg_stat_replication on the upstream, as the
WAIT FOR LSN command uses a latch-based wakeup mechanism.

The optimization applies when:
- The standby is passed as a Cluster object (not just a name string)
- The mode is 'replay', 'write', or 'flush' (not 'sent')
- The standby is in recovery

For 'sent' mode, when the standby is passed as a string (e.g., a
subscription name for logical replication), or when the standby has
been promoted, the function falls back to the original polling-based
approach using pg_stat_replication on the upstream.
    @alterego655
    alterego655 authored and Commitfest Bot committed Dec 26, 2025
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  5. [CF 6265] v8 - Add MODE parameter to WAIT FOR LSN command 

    This branch was automatically generated by a robot using patches from an
email thread registered at:

https://commitfest.postgresql.org/patch/6265

The branch will be overwritten each time a new patch version is posted to
the thread, and also periodically to check for bitrot caused by changes
on the master branch.

Patch(es): https://www.postgresql.org/message-id/CABPTF7WDzTs2EEB6c5QmsV-svF4rKSTLOS1pWM+7ydUN6tnFOQ@mail.gmail.com
Author(s): Xuneng Zhou
    Commitfest Bot committed Dec 26, 2025
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