From: Tom Lane <tgl@sss.pgh.pa.us>
To: Heikki Linnakangas <heikki@enterprisedb.com>
Cc: Craig Ringer <craig@postnewspapers.com.au>
Cc: pgsql-performance@postgresql.org
Subject: Re: Very slow (2 tuples/second) sequential scan after bulk insert; speed returns to ~500 tuples/second after commit
Date: Mon, 10 Mar 2008 11:20:40 -0400
Message-ID: <24304.1205162440@sss.pgh.pa.us> (raw)
In-Reply-To: <47D54DB2.4020405@enterprisedb.com>
References: <47D505AF.4040101@postnewspapers.com.au>
<47D5150C.8090802@enterprisedb.com>
<23588.1205159638@sss.pgh.pa.us>
<47D54A47.3030608@postnewspapers.com.au>
<47D54DB2.4020405@enterprisedb.com>
"Heikki Linnakangas" <heikki@enterprisedb.com> writes:
> The oprofile output is pretty damning:
> samples % symbol name
> 42148 99.7468 TransactionIdIsCurrentTransactionId
Oh, I have no doubt that that could eat a lot of cycles inside the
originating transaction ;-). I just misread Craig's complaint as
being about the cost of the first table scan *after* that transaction.
Getting rid of the linked-list representation would be a win in a couple
of ways --- we'd not need the bogus "list of XIDs" support in pg_list.h,
and xactGetCommittedChildren would go away. OTOH AtSubCommit_childXids
would get more expensive.
regards, tom lane
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To: pgsql-performance@postgresql.org
Cc: tgl@sss.pgh.pa.us, heikki@enterprisedb.com, craig@postnewspapers.com.au
Subject: Re: Very slow (2 tuples/second) sequential scan after bulk insert; speed returns to ~500 tuples/second after commit
In-Reply-To: <24304.1205162440@sss.pgh.pa.us>
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