Re: not(t_xmax = 0)

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
>
>
>