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

Commits on Nov 6, 2025

  1. Toggle logical decoding dynamically based on logical slot presence. 

    Previously logical decoding required wal_level to be set to 'logical'
at server start. This commit adds functionality to automatically
control logical decoding availability based on logical replication
slot presence.

The newly introduced module logicalctl.c allows logical decoding to be
dynamically activated when needed when wal_level is set to
'replica'. When the first logical replication slot is created, the
system automatically increases the effective WAL level to maintain
logical-level WAL records. Conversely, after the last logical slot is
dropped or invalidated, it decreases back to 'replica' WAL level.

A new read-only GUC parameter effective_wal_level is introduced to
monitor the actual WAL level in effect. This parameter reflects the
current operational WAL level, which may differ from the configured
wal_level setting.

While activation occurs synchronously right after creating the first
logical slot, deactivation happens asynchronously through the
checkpointer process. This design choice exists because deactivation
requires waiting for concurrent attempts to update logical decoding
status, which can be problematic when the process is holding
interrupts. This situation arises when a process cleans up temporary
or ephemeral slots on error or at process exit without releasing
temporary slots explicitly. This lazy approach has a drawback: it may
take longer to change the effective_wal_level and disable logical
decoding, especially when the checkpointer is busy with other
tasks. However, since dropping the last slot should not happen
frequently, we chose this approach in all deactivation cases for
simpler code implementation for simplicity, even though the lazy
approach is required only in error cases or at process exit time in
principle. In the future, we could address this limitation either by
using a dedicated worker instead of the checkpointer, or by
implementing synchronous waiting during slot drops if workloads are
significantly affected by the lazy deactivation of logical decoding.

XXX Bump PG_CONTROL_VERSION as it adds a new field to CheckPoint
struct.

Reviewed-by: Shveta Malik <[email protected]>
Reviewed-by: Shlok Kyal <[email protected]>
Reviewed-by: Bertrand Drouvot <[email protected]>
Reviewed-by: Amit Kapila <[email protected]>
Reviewed-by: Hayato Kuroda <[email protected]>
Reviewed-by: Ashutosh Bapat <[email protected]>
Discussion: https://postgr.es/m/CAD21AoCVLeLYq09pQPaWs+Jwdni5FuJ8v2jgq-u9_uFbcp6UbA@mail.gmail.com
    @MasahikoSawada
    MasahikoSawada authored and Commitfest Bot committed Nov 6, 2025
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  2. [CF 5479] v24 - Enable logical decoding when wal_level = 'replica' wi… 

    …thout a server restart

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

https://commitfest.postgresql.org/patch/5479

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/CAD21AoB+xpZ-+_=Zkj_RRcGk8gexkt3Sx3eLBBeWVpUqOHGvBg@mail.gmail.com
Author(s): Masahiko Sawada
    Commitfest Bot committed Nov 6, 2025
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