Message-ID: <49C9F49B.8020003@oss.ntt.co.jp>
Date: Wed, 25 Mar 2009 18:08:43 +0900
From: Tatsuhito Kasahara <kasahara.tatsuhito@oss.ntt.co.jp>
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To: pgsql-hackers@postgresql.org
Subject: display previous query string of idle-in-transaction
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Hi.

Now, we can check the running query string by pg_stat_activity.current_query.
If we can also check previous query_string of idle-in-transaction,
it is useful for analysis of long transaction problem.

Long-transaction is a trouble, because it prevents defragmentation of HOT and VACUUM.
And long-transaction tends to be it in a state of "idle in transaction".
(BEGIN -> SOME SQL -> .... (long-transactin) ....)

So, I sometimes want to know what query (main cause) was done before
transaction which have been practiced for a long time.

I think that we are glad when we can confirm it in the following form.
# We will be able to use debug_query_string in postgres.c for this purpose.

=================================================================
=# SELECT current_query FROM pg_stat_activity
   WHERE procpid <> pg_backend_pid();

                         current_query
---------------------------------------------------------------
 <IDLE> in transaction [prev]: SELECT * FROM pg_class limit 1;

=================================================================

Thoughts?

Best regards.

-- 
Tatsuhito Kasahara
kasahara.tatsuhito@oss.ntt.co.jp