Can I log query execution time in PostgreSQL 8.4?

Question

I want to log each query execution time which is run in a day.

For example like this,

2012-10-01 13:23:38 STATEMENT: SELECT * FROM pg_stat_database  runtime:265 ms.

Please give me some guideline.

Answer 1

If you set

log_min_duration_statement = 0
log_statement = all 

in your postgresql.conf, then you will see all statements being logged into the Postgres logfile.

If you enable

log_duration

that will also print the time taken for each statement. This is off by default.

Using the log_statement parameter you can control which type of statement you want to log (DDL, DML, ...)

This will produce an output like this in the logfile:

2012-10-01 13:00:43 CEST postgres LOG:  statement: select count(*) from pg_class;
2012-10-01 13:00:43 CEST postgres LOG:  duration: 47.000 ms

More details in the manual:

• http://www.postgresql.org/docs/8.4/static/runtime-config-logging.html#RUNTIME-CONFIG-LOGGING-WHEN
• http://www.postgresql.org/docs/8.4/static/runtime-config-logging.html#RUNTIME-CONFIG-LOGGING-WHAT

If you want a daily list, you probably want to configure the logfile to rotate on a daily basis. Again this is described in the manual.

Answer 2

I believe OP was actually asking for execution duration, not the timestamp.

To include the duration in the log output, open pgsql/<version>/data/postgresql.conf, find the line that reads

#log_duration = off

and change it to

log_duration = on

If you can't find the given parameter, just add it in a new line in the file.

After saving the changes, restart the postgresql service, or just invoke

pg_ctl reload -D <path to the directory of postgresql.conf>

e.g.

pg_ctl reload -D /var/lib/pgsql/9.2/data/

to reload the configuration.