When was my database started ?

In the database world, it’s fair to ask question to database that when have you started? In Oracle world, it can be easily find out by querying system level view V$INSTANCE. In PostgreSQL world, until today, I wasn’t able to answer that question without checking database log files. Today, I asked this question to OmniTi’s database operations irc channel and got answer in 20 minutes. I regret that I should have asked it earlier but anyways, now I know that in PostgreSQL it’s possible using this query.

omniti=# SELECT (pg_stat_file( 'postmaster.pid')).modification;
2010-08-13 15:37:14-04

If someone complains that database was restarted , it would be easy as DBA to query and verify it. I hope this query will be helpful to you during day-to-day operations!