From: | Robert Haas <robertmhaas(at)gmail(dot)com> |
---|---|
To: | Kevin Grittner <Kevin(dot)Grittner(at)wicourts(dot)gov> |
Cc: | drkp(at)csail(dot)mit(dot)edu, heikki(dot)linnakangas(at)enterprisedb(dot)com, pgsql-hackers(at)postgresql(dot)org |
Subject: | Re: Small SSI issues |
Date: | 2011-07-05 15:07:53 |
Message-ID: | CA+TgmobERS2i0Vf-JnSa1tGjgRyqErCbmahGCNUYejJQqKJqMQ@mail.gmail.com |
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On Tue, Jul 5, 2011 at 10:51 AM, Kevin Grittner
<Kevin(dot)Grittner(at)wicourts(dot)gov> wrote:
>> Is this still an open item?
>
> Yes, although I'm not clear on whether people feel it is one which
> needs to be fixed for 9.1 or left for 9.2.
>
> On a build with a BLCKSZ less than 8KB we would not get a warning
> before problems occurred, and we would have more serious problem
> involving potentially incorrect behavior. Tom questioned whether
> anyone actually builds with BLCKSZ less than 8KB, and I'm not
> altogether sure that SLRUs dealing with transaction IDs would behave
> correctly either.
>
> On block sizes larger than 8KB it will the warning if you burn
> through one billion transactions while holding one serializable read
> write transaction open, even though there won't be a problem. With
> the larger BLCKSZ values it may also generate log level messages
> about SLRU wraparound when that's not really a problem.
Well, as long as we can verify that OLDSERXID_MAX_PAGE has the same
value for BLCKSZ=8K before and after this patch, I don't see any real
downside to applying it. If, hypothetically, it's buggy, it's only
going to break things for non-default block sizes which are, by your
description, not correct right now anyway.
--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company
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