From: Alexander Korotkov <akorotkov@postgresql.org>
To: pgsql-committers@lists.postgresql.org
Subject: pgsql: Implement ALTER TABLE ... MERGE PARTITIONS ... command
Date: Sun, 14 Dec 2025 11:30:02 +0000
Message-ID: <E1vUkIb-000hmq-0B@gemulon.postgresql.org> (raw)
Implement ALTER TABLE ... MERGE PARTITIONS ... command
This new DDL command merges several partitions into a single partition of the
target table. The target partition is created using the new
createPartitionTable() function with the parent partition as the template.
This commit comprises a quite naive implementation which works in a single
process and holds the ACCESS EXCLUSIVE LOCK on the parent table during all
the operations, including the tuple routing. This is why this new DDL
command can't be recommended for large partitioned tables under a high load.
However, this implementation comes in handy in certain cases, even as it is.
Also, it could serve as a foundation for future implementations with less
locking and possibly parallelism.
Discussion: https://postgr.es/m/c73a1746-0cd0-6bdd-6b23-3ae0b7c0c582%40postgrespro.ru
Author: Dmitry Koval <d.koval@postgrespro.ru>
Co-authored-by: Alexander Korotkov <aekorotkov@gmail.com>
Co-authored-by: Tender Wang <tndrwang@gmail.com>
Co-authored-by: Richard Guo <guofenglinux@gmail.com>
Co-authored-by: Dagfinn Ilmari Mannsaker <ilmari@ilmari.org>
Co-authored-by: Fujii Masao <masao.fujii@gmail.com>
Co-authored-by: Jian He <jian.universality@gmail.com>
Reviewed-by: Matthias van de Meent <boekewurm+postgres@gmail.com>
Reviewed-by: Laurenz Albe <laurenz.albe@cybertec.at>
Reviewed-by: Zhihong Yu <zyu@yugabyte.com>
Reviewed-by: Justin Pryzby <pryzby@telsasoft.com>
Reviewed-by: Alvaro Herrera <alvherre@alvh.no-ip.org>
Reviewed-by: Robert Haas <rhaas@postgresql.org>
Reviewed-by: Stephane Tachoires <stephane.tachoires@gmail.com>
Reviewed-by: Jian He <jian.universality@gmail.com>
Reviewed-by: Alexander Korotkov <aekorotkov@gmail.com>
Reviewed-by: Pavel Borisov <pashkin.elfe@gmail.com>
Reviewed-by: Masahiko Sawada <sawada.mshk@gmail.com>
Reviewed-by: Alexander Lakhin <exclusion@gmail.com>
Reviewed-by: Kyotaro Horiguchi <horikyota.ntt@gmail.com>
Reviewed-by: Daniel Gustafsson <dgustafsson@postgresql.org>
Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us>
Reviewed-by: Noah Misch <noah@leadboat.com>
Branch
------
master
Details
-------
https://git.postgresql.org/pg/commitdiff/f2e4cc427951b7c46629fb7625a22f7898586f3a
Modified Files
--------------
doc/src/sgml/ddl.sgml | 19 +
doc/src/sgml/ref/alter_table.sgml | 127 ++-
src/backend/catalog/dependency.c | 54 +-
src/backend/catalog/pg_constraint.c | 2 +-
src/backend/commands/tablecmds.c | 894 +++++++++++++++-
src/backend/parser/gram.y | 22 +-
src/backend/parser/parse_utilcmd.c | 152 ++-
src/backend/partitioning/partbounds.c | 196 ++++
src/bin/psql/tab-complete.in.c | 10 +
src/include/catalog/dependency.h | 2 +
src/include/nodes/parsenodes.h | 8 +-
src/include/parser/kwlist.h | 1 +
src/include/partitioning/partbounds.h | 6 +
src/test/isolation/expected/partition-merge.out | 243 +++++
src/test/isolation/isolation_schedule | 1 +
src/test/isolation/specs/partition-merge.spec | 62 ++
.../test_ddl_deparse/expected/alter_table.out | 5 +
.../modules/test_ddl_deparse/sql/alter_table.sql | 3 +
.../modules/test_ddl_deparse/test_ddl_deparse.c | 3 +
src/test/regress/expected/partition_merge.out | 1097 ++++++++++++++++++++
src/test/regress/parallel_schedule | 2 +-
src/test/regress/sql/partition_merge.sql | 791 ++++++++++++++
22 files changed, 3668 insertions(+), 32 deletions(-)
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To: pgsql-committers@postgresql.org
Cc: akorotkov@postgresql.org, pgsql-committers@lists.postgresql.org
Subject: Re: pgsql: Implement ALTER TABLE ... MERGE PARTITIONS ... command
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