| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | "Heikki Linnakangas" <heikki(at)enterprisedb(dot)com> |
| Cc: | "Craig Ringer" <craig(at)postnewspapers(dot)com(dot)au>, pgsql-performance(at)postgresql(dot)org |
| Subject: | Re: Very slow (2 tuples/second) sequential scan after bulk insert; speed returns to ~500 tuples/second after commit |
| Date: | 2008-03-10 15:20:40 |
| Message-ID: | 24304.1205162440@sss.pgh.pa.us |
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| Lists: | pgsql-patches pgsql-performance |
"Heikki Linnakangas" <heikki(at)enterprisedb(dot)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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