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Re: Updatable cursors - applications?

From: Dave Page <dpage(at)postgresql(dot)org>
To: Hiroshi Inoue <inoue(at)tpf(dot)co(dot)jp>
Cc: pgsql-odbc(at)postgresql(dot)org
Subject: Re: Updatable cursors - applications?
Date: 2007-01-31 08:37:15
Message-ID: 45C0553B.3000403@postgresql.org (view raw or flat)
Thread:
Lists: pgsql-odbc
Hiroshi Inoue wrote:
> Dave Page wrote:
>> Does anyone know if there are any apps in existence that can be used as
>> a good test of the updatable cursor functionality in the driver?
>>
>> Hiroshi; do you have a test app for this purpose?
>>
>> In case anyone is wondering about my recent obsession with updatable
>> cursors, there is a patch from EnterpriseDB for PostgreSQL which offers
>> some quite significant performance benefits, but it does change the way
>> CTIDs work which the UC feature relies on.
> 
> The driver relies on the following.
> 1. TID scans i.e  SELECT/UPDATE/DELETE ... where CTID = ...
>    are available.
> 2. The fucntions currtid(2) returns the latest tid  of the given tid.
> 
> Does the patch change the above behavior ?

When I wrote originally, the version of the patch the guys were testing
added a couple of extra fields to the ctid (xmin and xmax iirc) which
shouldn't affect the driver (assuming there's no hard-coded memory
allocations for ctid). Simon did say yesterday that he'd figured out a
way to avoid changing ctid at all - I don't know yet how that's working out.

The bottom line is that we have no intention of suggesting dropping any
functionality - we just want to make sure everything will continue to
work as it should if the patch to the server is accepted.

Regards, Dave.

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