Waiting for PostgreSQL 19 – Sequence synchronization in logical replication.

First, on 9th of October 2025, Amit Kapila committed patch:

Add "ALL SEQUENCES" support to publications.
 
This patch adds support for the ALL SEQUENCES clause in publications,
enabling synchronization/replication of all sequences that is useful for
upgrades.
 
Publications can now include all sequences via FOR ALL SEQUENCES.
psql enhancements:
\d shows publications for a given sequence.
\dRp indicates if a publication includes all sequences.
 
ALL SEQUENCES can be combined with ALL TABLES, but not with other options
like TABLE or TABLES IN SCHEMA. We can extend support for more granular
clauses in future.
 
The view pg_publication_sequences provides information about the mapping
between publications and sequences.
 
This patch enables publishing of sequences; subscriber-side support will
be added in upcoming patches.
 
Author: vignesh C <vignesh21@gmail.com>
Author: Tomas Vondra <tomas@vondra.me>
Reviewed-by: shveta malik <shveta.malik@gmail.com>
Reviewed-by: Dilip Kumar <dilipbalaut@gmail.com>
Reviewed-by: Peter Smith <smithpb2250@gmail.com>
Reviewed-by: Hayato Kuroda <kuroda.hayato@fujitsu.com>
Reviewed-by: Masahiko Sawada <sawada.mshk@gmail.com>
Reviewed-by: Nisha Moond <nisha.moond412@gmail.com>
Reviewed-by: Shlok Kyal <shlok.kyal.oss@gmail.com>
Reviewed-by: Amit Kapila <amit.kapila16@gmail.com>
Discussion: https://postgr.es/m/CAA4eK1LC+KJiAkSrpE_NwvNdidw9F2os7GERUeSxSKv71gXysQ@mail.gmail.com

And then, on 5th of November 2025, he also committed patch:

Add sequence synchronization for logical replication.
 
This patch introduces sequence synchronization. Sequences that are synced
will have 2 states:
   - INIT (needs [re]synchronizing)
   - READY (is already synchronized)
 
A new sequencesync worker is launched as needed to synchronize sequences.
A single sequencesync worker is responsible for synchronizing all
sequences. It begins by retrieving the list of sequences that are flagged
for synchronization, i.e., those in the INIT state. These sequences are
then processed in batches, allowing multiple entries to be synchronized
within a single transaction. The worker fetches the current sequence
values and page LSNs from the remote publisher, updates the corresponding
sequences on the local subscriber, and finally marks each sequence as
READY upon successful synchronization.
 
Sequence synchronization occurs in 3 places:
1) CREATE SUBSCRIPTION
    - The command syntax remains unchanged.
    - The subscriber retrieves sequences associated with publications.
    - Published sequences are added to pg_subscription_rel with INIT
      state.
    - Initiate the sequencesync worker to synchronize all sequences.
 
2) ALTER SUBSCRIPTION ... REFRESH PUBLICATION
    - The command syntax remains unchanged.
    - Dropped published sequences are removed from pg_subscription_rel.
    - Newly published sequences are added to pg_subscription_rel with INIT
      state.
    - Initiate the sequencesync worker to synchronize only newly added
      sequences.
 
3) ALTER SUBSCRIPTION ... REFRESH SEQUENCES
    - A new command introduced for PG19 by f0b3573c3a.
    - All sequences in pg_subscription_rel are reset to INIT state.
    - Initiate the sequencesync worker to synchronize all sequences.
    - Unlike "ALTER SUBSCRIPTION ... REFRESH PUBLICATION" command,
      addition and removal of missing sequences will not be done in this
      case.
 
Author: Vignesh C <vignesh21@gmail.com>
Reviewed-by: shveta malik <shveta.malik@gmail.com>
Reviewed-by: Hou Zhijie <houzj.fnst@fujitsu.com>
Reviewed-by: Masahiko Sawada <sawada.mshk@gmail.com>
Reviewed-by: Hayato Kuroda <kuroda.hayato@fujitsu.com>
Reviewed-by: Dilip Kumar <dilipbalaut@gmail.com>
Reviewed-by: Peter Smith <smithpb2250@gmail.com>
Reviewed-by: Nisha Moond <nisha.moond412@gmail.com>
Reviewed-by: Shlok Kyal <shlok.kyal.oss@gmail.com>
Reviewed-by: Amit Kapila <amit.kapila16@gmail.com>
Reviewed-by: Chao Li <li.evan.chao@gmail.com>
Discussion: https://postgr.es/m/CAA4eK1LC+KJiAkSrpE_NwvNdidw9F2os7GERUeSxSKv71gXysQ@mail.gmail.com

Continue reading Waiting for PostgreSQL 19 – Sequence synchronization in logical replication.

A tale about (incomplete) upgrade from PostgreSQL 12 to 14

This might not interest many of you, but I recently heard about at least two people that stumbled upon the problems I did, so I figured I can write about problems we discovered, and how we solved them (or not).

When we began our journey, the latest Pg was 14.x, that's why we're upgrading to 14, not 15. But I suspect upgrading to 15 wouldn't change much …

Continue reading A tale about (incomplete) upgrade from PostgreSQL 12 to 14

Waiting for PostgreSQL 15 – Allow publishing the tables of schema.

On 27th of October 2021, Amit Kapila committed patch:

Allow publishing the tables of schema.
 
A new option "FOR ALL TABLES IN SCHEMA" in Create/Alter Publication allows
one or more schemas to be specified, whose tables are selected by the
publisher for sending the data to the subscriber.
 
The new syntax allows specifying both the tables and schemas. For example:
CREATE PUBLICATION pub1 FOR TABLE t1,t2,t3, ALL TABLES IN SCHEMA s1,s2;
OR
ALTER PUBLICATION pub1 ADD TABLE t1,t2,t3, ALL TABLES IN SCHEMA s1,s2;
 
A new system table "pg_publication_namespace" has been added, to maintain
the schemas that the user wants to publish through the publication.
Modified the output plugin (pgoutput) to publish the changes if the
relation is part of schema publication.
 
Updates pg_dump to identify and dump schema publications. Updates the \d
family of commands to display schema publications and \dRp+ variant will
now display associated schemas if any.
 
Author: Vignesh C, Hou Zhijie, Amit Kapila
Syntax-Suggested-by: Tom Lane, Alvaro Herrera
Reviewed-by: Greg Nancarrow, Masahiko Sawada, Hou Zhijie, Amit Kapila, Haiying Tang, Ajin Cherian, Rahila Syed, Bharath Rupireddy, Mark Dilger
Tested-by: Haiying Tang
Discussion: https://www.postgresql.org/message-id/CALDaNm0OANxuJ6RXqwZsM1MSY4s19nuH3734j4a72etDwvBETQ@mail.gmail.com

Continue reading Waiting for PostgreSQL 15 – Allow publishing the tables of schema.

Waiting for PostgreSQL 13 – Add logical replication support to replicate into partitioned tables

On 6th of April 2020, Peter Eisentraut committed patch:

Add logical replication support to replicate into partitioned tables 
 
Mainly, this adds support code in logical/worker.c for applying
replicated operations whose target is a partitioned table to its
relevant partitions.
 
Author: Amit Langote <amitlangote09@gmail.com>
Reviewed-by: Rafia Sabih <rafia.pghackers@gmail.com>
Reviewed-by: Peter Eisentraut <peter.eisentraut@2ndquadrant.com>
Reviewed-by: Petr Jelinek <petr@2ndquadrant.com>
Discussion: https://www.postgresql.org/message-id/flat/CA+HiwqH=Y85vRK3mOdjEkqFK+E=ST=eQiHdpj43L=_eJMOOznQ@mail.gmail.com

Continue reading Waiting for PostgreSQL 13 – Add logical replication support to replicate into partitioned tables

Waiting for PostgreSQL 12 – Add pg_promote function

On 25th of October 2018, Michael Paquier committed patch:

Add pg_promote function
 
 
This function is able to promote a standby with this new SQL-callable
function.  Execution access can be granted to non-superusers so that
failover tools can observe the principle of least privilege.
 
Catalog version is bumped.
 
Author: Laurenz Albe
 
Discussion: https://postgr.es/m/.camel@cybertec.at

Continue reading Waiting for PostgreSQL 12 – Add pg_promote function

Waiting for PostgreSQL 10 – Logical replication support for initial data copy

On 23rd of March 2017, Peter Eisentraut committed patch:

Logical replication support for initial data copy
 
Add functionality for a new subscription to copy the initial data in the
tables and then sync with the ongoing apply process.
 
For the copying, add a new internal COPY option to have the COPY source
data provided by a callback function.  The initial data copy works on
the subscriber by receiving COPY data from the publisher and then
providing it locally into a COPY that writes to the destination table.
 
A WAL receiver can now execute full SQL commands.  This is used here to
obtain information about tables and publications.
 
Several new options were added to CREATE and ALTER SUBSCRIPTION to
control whether and when initial table syncing happens.
 
Change pg_dump option --no-create-subscription-slots to
--no-subscription-connect and use the new CREATE SUBSCRIPTION
... NOCONNECT option for that.
 
Author: Petr Jelinek

Continue reading Waiting for PostgreSQL 10 – Logical replication support for initial data copy

Waiting for PostgreSQL 10 – hash indexing vs. WAL

For a long time hash indexed were not crash safe, and couldn't be used on replication slave, because they skipped WAL. Now, thanks to these two commits, it has changed:

On 14th of March 2017, Robert Haas committed patch:

hash: Add write-ahead logging support.
 
The warning about hash indexes not being write-ahead logged and their
use being discouraged has been removed.  "snapshot too old" is now
supported for tables with hash indexes.  Most importantly, barring
bugs, hash indexes will now be crash-safe and usable on standbys.
 
This commit doesn't yet add WAL consistency checking for hash
indexes, as we now have for other index types; a separate patch has
been submitted to cure that lack.
 
Amit Kapila, reviewed and slightly modified by me.  The larger patch
series of which this is a part has been reviewed and tested by Álvaro
Herrera, Ashutosh Sharma, Mark Kirkwood, Jeff Janes, and Jesper
Pedersen.
 
Discussion: http://postgr.es/m/CAA4eK1JOBX=YU33631Qh-XivYXtPSALh514+jR8XeD7v+K3r_Q@mail.gmail.com

and then, ~ 13 hours later, Robert committed also:

hash: Support WAL consistency checking.
 
Kuntal Ghosh, reviewed by Amit Kapila and Ashutosh Sharma, with
a few tweaks by me.
 
Discussion: http://postgr.es/m/CAGz5QCJLERUn_zoO0eDv6_Y_d0o4tNTMPeR7ivTLBg4rUrJdwg@mail.gmail.com

Continue reading Waiting for PostgreSQL 10 – hash indexing vs. WAL

Waiting for PostgreSQL 10 – Logical replication

On 20th of January, Peter Eisentraut committed patch:

Logical replication
 
- Add PUBLICATION catalogs and DDL
- Add SUBSCRIPTION catalog and DDL
- Define logical replication protocol and output plugin
- Add logical replication workers
 
From: Petr Jelinek
Reviewed-by: Steve Singer
Reviewed-by: Andres Freund
Reviewed-by: Erik Rijkers
Reviewed-by: Peter Eisentraut

Continue reading Waiting for PostgreSQL 10 – Logical replication

Major-version upgrading with minimal downtime

There is this idea that from 9.5 we will be able to upgrade pg clusters to newer, major, version, without downtime (well, almost), thanks to magic of logical replication.

Sounds very promising, so I figured – I'll test it. To some extent at least.

Continue reading Major-version upgrading with minimal downtime