From: | Alejandro Carrillo <fasterzip(at)yahoo(dot)es> |
---|---|
To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Kevin Grittner <kgrittn(at)mail(dot)com> |
Cc: | "pgsql-general(at)postgresql(dot)org" <pgsql-general(at)postgresql(dot)org> |
Subject: | Re: not(t_xmax = 0) |
Date: | 2013-01-21 01:36:16 |
Message-ID: | 1358732176.67313.YahooMailNeo@web172206.mail.ir2.yahoo.com |
Views: | Raw Message | Whole Thread | Download mbox | Resend email |
Thread: | |
Lists: | pgsql-general |
this function didn't work to know if a row can surely dead?
http://doxygen.postgresql.org/tqual_8c_source.html#l01236
>________________________________
> De: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
>Para: Kevin Grittner <kgrittn(at)mail(dot)com>
>CC: Alejandro Carrillo <fasterzip(at)yahoo(dot)es>; pgsql-general(at)postgresql(dot)org
>Enviado: Domingo 20 de enero de 2013 15:30
>Asunto: Re: [GENERAL] not(t_xmax = 0)
>
>"Kevin Grittner" <kgrittn(at)mail(dot)com> writes:
>> Alejandro Carrillo wrote:
>>> I try to do a function that let know which rows are deleted in a
>>> table using the xmax !=0
>
>> That's not something you're going to have much luck with by using
>> plpgsql to try to parse heap pages.
>
>No, because xmax being nonzero doesn't prove much: the row might be
>updated/deleted, or it might only have been locked by SELECT FOR UPDATE,
>or it might be perfectly fine because the updating transaction rolled
>back. You could get a limited amount of information by checking the
>hint bits in t_infomask, but if the hint bits aren't set you won't know
>what the row's state is.
>
>You'd really need to do this in C using the tqual.c functions for the
>results to be trustworthy.
>
>I'm a bit surprised that contrib/pageinspect doesn't have a mechanism
>for pulling out only committed-good heap tuples...
>
> regards, tom lane
>
>
>
From | Date | Subject | |
---|---|---|---|
Next Message | Tom Lane | 2013-01-21 03:01:44 | Re: proposal: fix corner use case of variadic fuctions usage |
Previous Message | Adrian Klaver | 2013-01-21 01:04:10 | Re: Understanding TIMESTAMP WITH TIME ZONE |