temp_tablespaces — PostgreSQL configuration parameter

This variable specifies tablespaces in which to create temporary objects (temp tables and indexes on temp tables) when a CREATE command does not explicitly specify a tablespace.

At a glance

What it does

This variable specifies tablespaces in which to create temporary objects (temp tables and indexes on temp tables) when a CREATE command does not explicitly specify a tablespace. Temporary files for purposes such as sorting large data sets are also created in these tablespaces.

The value is a list of names of tablespaces. When there is more than one name in the list, PostgreSQL chooses a random member of the list each time a temporary object is to be created; except that within a transaction, successively created temporary objects are placed in successive tablespaces from the list. If the selected element of the list is an empty string, PostgreSQL will automatically use the default tablespace of the current database instead.

(Description quoted from the official PostgreSQL documentation.)

How to apply a change

Can be set per session with SET, per role/database with ALTER ROLE/DATABASE ... SET, or globally in postgresql.conf.

Inspect the current value and source with SHOW temp_tablespaces; or SELECT name, setting, unit, context, source FROM pg_settings WHERE name = 'temp_tablespaces';.

Tuning guidance

This sets a session default (locale, formatting, search path or transaction behaviour) rather than a performance knob. Set it per role or database with ALTER ROLE/DATABASE ... SET so the right default follows the right workload, and prefer setting it explicitly in the application for behaviour the query results depend on.

Reference

PostgreSQL documentation — temp_tablespaces.