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Re: [HACKERS] Re: possible row locking bug in 7.0.3 & 7.1

From: Hiroshi Inoue <Inoue(at)tpf(dot)co(dot)jp>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: Philip Warner <pjw(at)rhyme(dot)com(dot)au>, pgsql-sql(at)postgresql(dot)org, pgsql-hackers(at)postgresql(dot)org
Subject: Re: [HACKERS] Re: possible row locking bug in 7.0.3 & 7.1
Date: 2001-03-28 06:19:05
Message-ID: 3AC18259.C5A8B0A9@tpf.co.jp (view raw or flat)
Thread:
Lists: pgsql-hackerspgsql-sql
Tom Lane wrote:
> 
> Philip Warner <pjw(at)rhyme(dot)com(dot)au> writes:
> >> The workaround for Forest is to make the final SELECT be a SELECT FOR
> >> UPDATE, so that it's playing by the same rules as the earlier commands.
> 
> > Eek. Does this seem good to you?
> 
> I did call it a workaround ;-)
> 
> I don't think that we dare try to make any basic changes in MVCC for 7.1
> at this late hour, so Forest is going to have to live with that answer
> for awhile.  But I would like to see a cleaner answer in future
> releases.

Is it the MVCC's restriction that each query inside a function
must use the same snapshot ?

> As I've opined before, the whole EvalPlanQual mechanism
> strikes me as essentially bogus in any case...
> 

How would you change it ? UPDATE/SELECT FOR UPDATE have to
SELECT/UPDATE the latest tuples. I don't think of any simple
way for 'SELECT FOR UPDATE' to have the same visibility as
simple SELECT.

regards,
Hiroshi Inoue

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