| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com> |
| Cc: | Greg Stark <gsstark(at)mit(dot)edu>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>, Robert Haas <robertmhaas(at)gmail(dot)com>, Bruce Momjian <bruce(at)momjian(dot)us>, Teodor Sigaev <teodor(at)sigaev(dot)ru>, Oleg Bartunov <oleg(at)sai(dot)msu(dot)su> |
| Subject: | Re: GiST insert algorithm rewrite |
| Date: | 2010-12-13 18:30:55 |
| Message-ID: | 3001.1292265055@sss.pgh.pa.us |
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Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com> writes:
> On 13.12.2010 19:48, Tom Lane wrote:
>> Yeah. Wouldn't the original page-split record have been carrying full
>> page images already?
> Yes.
> BTW, the original split record doesn't run into the limit because it
> doesn't use the backup-block mechanism, it contains all the tuples for
> all the pages in the main payload.
I see.
>> (And if so, why didn't we have this problem in the
>> previous implementation?)
> In the previous implementation, the NSN was updated immediately in the
> page split record, and there was no follow-right flag to clear. So the
> child pages didn't need to be updated when the downlinks are inserted.
Can we fix it so that each child page is updated, and its downlink
inserted, as a separate atomic action? That'd require each intermediate
state to be consistent and crash-safe, but I think you really need the
intermediate states to be consistent anyway because of concurrent scans.
regards, tom lane
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