transaction_isolation — PostgreSQL configuration parameter

This parameter reflects the current transaction’s isolation level.

At a glance

What it does

This parameter reflects the current transaction’s isolation level. At the beginning of each transaction, it is set to the current value of default_transaction_isolation. Any subsequent attempt to change it is equivalent to a set_transaction command.

(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 transaction_isolation; or SELECT name, setting, unit, context, source FROM pg_settings WHERE name = 'transaction_isolation';.

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 — transaction_isolation.