Re: remove ATTRIBUTE_FIXED_PART_SIZE

From: Peter Eisentraut <peter(dot)eisentraut(at)2ndquadrant(dot)com>
To: Andres Freund <andres(at)anarazel(dot)de>
Cc: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, pgsql-hackers(at)lists(dot)postgresql(dot)org, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: remove ATTRIBUTE_FIXED_PART_SIZE
Date: 2018-08-21 15:15:53
Message-ID: ec636b39-d401-937f-12c7-6fbdd888a44e@2ndquadrant.com
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On 20/08/2018 12:46, Andres Freund wrote:
> static VacAttrStats *
> examine_attribute(Relation onerel, int attnum, Node *index_expr)
> {
> ...
> /*
> * Create the VacAttrStats struct. Note that we only have a copy of the
> * fixed fields of the pg_attribute tuple.
> */
> stats = (VacAttrStats *) palloc0(sizeof(VacAttrStats));
> stats->attr = (Form_pg_attribute) palloc(ATTRIBUTE_FIXED_PART_SIZE);
> memcpy(stats->attr, attr, ATTRIBUTE_FIXED_PART_SIZE);
>
> Accesses to stats->attr can legitimately assume that the padding at the
> tail end of attr is present (i.e. widening a load / store).

Yeah, that's probably just broken.

--
Peter Eisentraut http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services

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