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Re: GiST insert algorithm rewrite

From: Robert Haas <robertmhaas(at)gmail(dot)com>
To: Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com>
Cc: Bruce Momjian <bruce(at)momjian(dot)us>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>, Teodor Sigaev <teodor(at)sigaev(dot)ru>, Oleg Bartunov <oleg(at)sai(dot)msu(dot)su>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Subject: Re: GiST insert algorithm rewrite
Date: 2010-12-01 14:27:54
Message-ID: (view raw, whole thread or download thread mbox)
Lists: pgsql-hackers
On Wed, Dec 1, 2010 at 4:00 AM, Heikki Linnakangas
<heikki(dot)linnakangas(at)enterprisedb(dot)com> wrote:
> On 01.12.2010 04:10, Robert Haas wrote:
>> On Tue, Nov 30, 2010 at 10:26 AM, Heikki Linnakangas
>> <heikki(dot)linnakangas(at)enterprisedb(dot)com>  wrote:
>>>> Does the current code cope with the corruption?
>>> It's not corruption, but "intended degradation". Yes, the current code
>>> copes
>>> with it, that's how GiST survives a crash. However, even with the current
>>> code, VACUUM will nag if it finds any invalid tuples with this message:
>>> ereport(NOTICE,
>>>        (errmsg("index \"%s\" needs VACUUM FULL or REINDEX to finish crash
>>> recovery",
>>> That's harmless, in the sense that all scans and inserts work fine, but
>>> scans might need to do more work than if the invalid tuple wasn't there.
>>> I don't think we need to go out of our way to support such degraded
>>> indexes
>>> in 9.1. If you see such notices in your logs, you should REINDEX anyway,
>>> before of after pg_upgrade. Let's just make sure that you get a
>>> reasonable
>>> error message in 9.1 if a scan or insert encounters such a tuple.
>> I just don't want to take a risk of giving people unexpected wrong
>> answers.  It's not clear to me whether that's a risk here or not.
> You'll get an error if a scan encounters an invalid tuple.
> In the patch I posted, I just ripped out everything related to invalid
> tuples altogether. But we should add a check and ereport for that before
> commit.

All right, that seems like a reasonable backstop, if we're fairly sure
this won't be a common scenario.

Robert Haas
The Enterprise PostgreSQL Company

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