| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Simon Riggs <simon(at)2ndQuadrant(dot)com> |
| Cc: | Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Re: [COMMITTERS] pgsql: Introduce WAL records to log reuse of btree pages, allowing |
| Date: | 2010-02-18 19:17:11 |
| Message-ID: | 9803.1266520631@sss.pgh.pa.us |
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Simon Riggs <simon(at)2ndQuadrant(dot)com> writes:
> On Thu, 2010-02-18 at 14:23 +0200, Heikki Linnakangas wrote:
>> A straightforward way to fix that is to WAL-log the real xid in the
>> XLOG_BTREE_DELETE_PAGE records, instead of resetting it to
>> FrozenTransactionId.
> An even simpler way would be to reset the value to latestCompletedXid
> during btree_xlog_delete_page(). That touches less code. I doubt it will
> make much difference to conflict recovery, since if pages are being
> deleted then btree delete records are likely to be frequent and will
> have already killed long running queries.
I'm a bit concerned about XID wraparound if the value doesn't get reset
to FrozenTransactionId. There's no guarantee the page will get reused
promptly ...
regards, tom lane
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