Parameter · Reporting and Logging / What to Log

log_statement

Sets the type of statements logged.

Default: none
Type: enum
Values: none · ddl · mod · all
Applies: Session (superuser)

In plain words

Logs the text of SQL statements as they start, filtered by kind: ddl logs schema changes, mod also logs data changes (INSERT, UPDATE, DELETE …), all logs everything including SELECTs. ddl is a popular, low-volume audit trail.

For DBAs and operators

Classes: ddl = CREATE, ALTER, DROP (and similar schema commands); mod = ddl plus INSERT, UPDATE, DELETE, MERGE, TRUNCATE, COPY FROM, and PREPARE/EXECUTE/EXPLAIN ANALYZE of those; all = every statement. Verified on 18.6: with mod, EXPLAIN ANALYZE INSERT and TRUNCATE were logged, COPY … TO was not.

LOG: statement: update t set v=v where id=1; LOG: statement: execute p(1, 'abcdefghijklmnopqrstuvwxyz'); DETAIL: prepare: prepare p(int,text) as select $1, $2; LOG: execute <unnamed>: SELECT * FROM orders WHERE id = $1 DETAIL: Parameters: $1 = '42'

Logging happens before execution (after parsing), so failed statements are logged too, while statements with syntax errors are not. Statements inside functions (PL/pgSQL) are not logged, only the outer call: for full auditing use the pgaudit extension.

With mod or all the log contains data values, including passwords in CREATE/ALTER ROLE … PASSWORD (also with ddl!). all on a busy system generates huge volume and adds latency; prefer sampling or log_min_duration_statement.

How to change it

A superuser (or a role granted SET) can change it per session with SET.

See it in context

Life of a query Logger (logging collector)

Related parameters

log_min_duration_statement log_duration log_parameter_max_length log_min_error_statement

All Reporting and Logging parameters