Re: duplicate postings

John R Pierce <pierce(at)hogranch(dot)com> writes:
> today has been like deja vu, I'm seeing all kinda postings from
> yesterday regurgitated.

> is this just me? or did the server hiccup and send a lot of stuff twice?

It appears that one alexis(dot)michon(at)ibcp(dot)fr at athena.ibcp.fr regurgitated
a lot of postings. To judge by what I got this morning (one example
below), the PG servers did reject a lot of them as duplicate, with the
bounce messages going to the original posters, since the regurgitated
messages were complete with forged envelope From :-(. But some of them
apparently got modified enough to escape the duplicate-checksum test,
and then they got posted, since they looked like real messages from
subscribed people.

This happens every so often. It seems to usually be the fault of broken
Microsloth mail software. This particular case doesn't bear enough
traces to be sure about what caused it though.

regards, tom lane

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Your message to the pgsql-performance list has been denied
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Duplicate Message-ID - <9435(dot)1307636402(at)sss(dot)pgh(dot)pa(dot)us> (Thu Jun 9 13:20:16 2011)
Duplicate Partial Message Checksum (Thu Jun 9 13:20:16 2011)

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To: Jochen Erwied <jochen(at)erwied(dot)eu>
cc: Marti Raudsepp <marti(at)juffo(dot)org>,
muthu krishnan <muthu(dot)krishnan(dot)linux(at)gmail(dot)com>,
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Comments: In-reply-to Jochen Erwied <jochen(at)erwied(dot)eu>
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Date: Thu, 09 Jun 2011 12:20:02 -0400
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From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
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Jochen Erwied <jochen(at)erwied(dot)eu> writes:
> Thursday, June 9, 2011, 12:45:06 PM you wrote:
>> As the URL mentions, you can build with CFLAGS=-ffast-math, that
>> should work for PostgreSQL too.

> I just tried this with the source for 9.0.4, at least with this version the
> build will not complete since there is a check in
> src/backend/utils/adt/date.c throwing an error if FAST_MATH is active.

Yeah. See
http://archives.postgresql.org/pgsql-bugs/2002-09/msg00169.php
and following discussions, which eventually led to adding the #error.

Now this was all done in regards to PG's original floating-point
timestamp implementation. It's possible that in an integer-datetimes
build (which is now the default) we don't need to forbid -ffast-math to
prevent strange datetime results. But nobody's done the work to prove
that, because there isn't any particularly good reason to enable
-ffast-math in a database in the first place. (Other than coping with
brain-dead platforms, I guess.)

However ... I'm not sure I believe that this is related to the OP's
problem anyway. Postgres doesn't normally work with any denormalized
numbers, so the messages he's seeing probably stem from some other sort
of shortcoming in the hardware FP support. It would be interesting to
see specific examples of SQL operations that trigger the kernel message.

regards, tom lane

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