Re: 9.3.9 and pg_multixact corruption

Bernd Helmle wrote:
> A customer had a severe issue with a PostgreSQL 9.3.9/sparc64/Solaris 11
> instance.
>

> 2015-09-08 11:40:59 CEST [27047] FATAL: could not access status of
> transaction 1068235595
> 2015-09-08 11:40:59 CEST [27047] DETAIL: Could not seek in file
> "pg_multixact/members/FFFF5FC4" to offset 4294950912: Invalid argument.
> 2015-09-08 11:40:59 CEST [27047] CONTEXT: xlog redo create mxid 1068235595
> offset 2147483648 nmembers 2: 2896635220 (upd) 2896635510 (keysh)

I think the math to compute segment number and byte offset of the member
might be bogus here. The file names in pg_multixact/members is supposed
to go to 14078 (hex) in a 8kB-BLCKSZ build, and of course it goes a bit
higher in builds with smaller page sizes, but nowhere as high as
FFFF5FC4. And the offset is way too close to 2^32 (exactly 16384 less
than 2^32, to be precise.)

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