From db6e1aeb952e9aed26ba2a56b4145293c72b8068 Mon Sep 17 00:00:00 2001 From: Alvaro Herrera Date: Thu, 6 May 2021 16:42:30 -0400 Subject: [PATCH] Improve documentation on DETACH PARTITION lock levels This was forgotten in 71f4c8c6f74b. Reported-by: Pavel Luzanov Author: Amit Langote Discussion: https://postgr.es/m/0688e7c3-8bc8-a3e4-9d8e-3bcbbf3e1f4d@postgrespro.ru --- doc/src/sgml/ddl.sgml | 24 ++++++++++-------------- doc/src/sgml/ref/alter_table.sgml | 2 +- 2 files changed, 11 insertions(+), 15 deletions(-) diff --git a/doc/src/sgml/ddl.sgml b/doc/src/sgml/ddl.sgml index b4648321dc4..63bc946c3b6 100644 --- a/doc/src/sgml/ddl.sgml +++ b/doc/src/sgml/ddl.sgml @@ -3915,18 +3915,25 @@ DROP TABLE measurement_y2006m02; Another option that is often preferable is to remove the partition from the partitioned table but retain access to it as a table in its own - right: + right. This has two forms: ALTER TABLE measurement DETACH PARTITION measurement_y2006m02; +ALTER TABLE measurement DETACH PARTITION measurement_y2006m02 CONCURRENTLY; - This allows further operations to be performed on the data before + These allow further operations to be performed on the data before it is dropped. For example, this is often a useful time to back up the data using COPY, pg_dump, or similar tools. It might also be a useful time to aggregate data into smaller formats, perform other data manipulations, or run - reports. + reports. The first form of the command requires an + ACCESS EXCLUSIVE lock on the parent table. + Adding the CONCURRENTLY qualifier as in the second + form allows the detach operation to require only + SHARE UPDATE EXCLUSIVE lock on the parent table, but see + ALTER TABLE ... DETACH PARTITION + for details on the restrictions. @@ -4163,17 +4170,6 @@ ALTER INDEX measurement_city_id_logdate_key might be poor.) - - - - Some operations require a stronger lock when using declarative - partitioning than when using table inheritance. For example, - removing a partition from a partitioned table requires taking - an ACCESS EXCLUSIVE lock on the parent table, - whereas a SHARE UPDATE EXCLUSIVE lock is enough - in the case of regular inheritance. - - diff --git a/doc/src/sgml/ref/alter_table.sgml b/doc/src/sgml/ref/alter_table.sgml index 9cef1f101eb..087f640dc07 100644 --- a/doc/src/sgml/ref/alter_table.sgml +++ b/doc/src/sgml/ref/alter_table.sgml @@ -967,7 +967,7 @@ WITH ( MODULUS numeric_literal, REM - + DETACH PARTITION partition_name [ CONCURRENTLY | FINALIZE ]