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Re: truncate partitioned table locking

From: "Benjamin Krajmalnik" <kraj(at)illumen(dot)com>
To: "Tom Lane" <tgl(at)sss(dot)pgh(dot)pa(dot)us>,"Sriram Dandapani" <sdandapani(at)counterpane(dot)com>
Cc: <pgsql-admin(at)postgresql(dot)org>
Subject: Re: truncate partitioned table locking
Date: 2006-06-20 15:20:22
Message-ID: BF337097BDD9D849A2F4B818DDB27987029371@stash.stackdump.local (view raw or flat)
Thread:
Lists: pgsql-admin
Siriam,

As I mentioned to you yesterday, I have a partitioned table which gets
over a million inserts per day (routed to the correct partition via
triggers).  Each partition holds one month' worth of data, so
approximately 30 million rows.  Last time I truncated the oldest
partition took 2 ms.


-----Original Message-----
From: pgsql-admin-owner(at)postgresql(dot)org
[mailto:pgsql-admin-owner(at)postgresql(dot)org] On Behalf Of Tom Lane
Sent: Monday, June 19, 2006 7:24 PM
To: Sriram Dandapani
Cc: pgsql-admin(at)postgresql(dot)org
Subject: Re: [ADMIN] truncate partitioned table locking 

"Sriram Dandapani" <sdandapani(at)counterpane(dot)com> writes:
> How can I issue a truncate /drop table on the child without running
into
> locking issues. Doesn't constraint exclusion prevent access of a child
> table based on the check constraint criteria

No, because the planner has to access the child table in order to
examine its constraints.  (Since TRUNCATE is a metadata update, the
fact that the constraints are metadata not content doesn't help.)

TRUNCATE in itself is fast enough that you shouldn't really have any
problems here.  If you are having locking issues then I suspect you need
to look for transactions that are sitting on ordinary reader or writer
locks of the table, instead of doing their jobs and committing.

			regards, tom lane

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Subject: Re: truncate partitioned table locking
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