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Re: GiST insert algorithm rewrite

From: Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com>
To: Robert Haas <robertmhaas(at)gmail(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 09:00:43
Message-ID: 4CF60EBB.4090707@enterprisedb.com (view raw or flat)
Thread:
Lists: pgsql-hackers
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.

-- 
   Heikki Linnakangas
   EnterpriseDB   http://www.enterprisedb.com

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Subject: Re: Another proposal for table synonyms
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