Re: mcvstats serialization code is still shy of a load

On Sun, Jun 30, 2019 at 08:30:33PM -0400, Tom Lane wrote:
>Tomas Vondra <tomas.vondra@2ndquadrant.com> writes:
>> Attached is a slightly improved version of the serialization patch.
>
>I reviewed this patch, and tested it on hppa and ppc.  I found one
>serious bug: in the deserialization varlena case, you need
>
>-					dataptr += MAXALIGN(len);
>+					dataptr += MAXALIGN(len + VARHDRSZ);
>
>(approx. line 1100 in mcv.c).  Without this, the output data is corrupt,
>plus the Assert a few lines further down about dataptr having been
>advanced by the correct amount fires.  (On one machine I tested on,
>that happened during the core regression tests.  The other machine
>got through regression, but trying to do "select * from pg_stats_ext;"
>afterwards exhibited the crash.  I didn't investigate closely, but
>I suspect the difference has to do with different MAXALIGN values,
>4 and 8 respectively.)
>
>The attached patch (a delta atop your v2) corrects that plus some
>cosmetic issues.
>

Thanks.

>If we're going to push this, it would be considerably less complicated
>to do so before v12 gets branched --- not long after that, there will be
>catversion differences to cope with.  I'm planning to make the branch
>tomorrow (Monday), probably ~1500 UTC.  Just sayin'.
>

Unfortunately, I was travelling on Sunday and was quite busy on Monday, so
I've been unable to push this before the branching :-(

I'll push by the end of this week, once I get home.


regards

-- 
Tomas Vondra                  http://www.2ndQuadrant.com
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