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Re: testing HS/SR - 1 vs 2 performance

From: Simon Riggs <simon(at)2ndQuadrant(dot)com>
To: marcin mank <marcin(dot)mank(at)gmail(dot)com>
Cc: pgsql-hackers(at)postgresql(dot)org
Subject: Re: testing HS/SR - 1 vs 2 performance
Date: 2010-04-21 14:49:06
Message-ID: 1271861346.8305.28130.camel@ebony (view raw, whole thread or download thread mbox)
Lists: pgsql-hackers
On Wed, 2010-04-21 at 16:22 +0200, marcin mank wrote:

> Is that not a good idea that (at least for dev-builds, like with
> enable-cassert) the xid counter start at like 2^31 - 1000 ? It could
> help catch some bugs.

It is a good idea, I'm sure that would help catch bugs.

It wouldn't help here because the case in doubt is whether it's possible
to have an xid still showing in memory arrays from the last time the
cycle wrapped. It isn't. These things aren't random. These numbers are
extracted directly from activity that was occurring on the primary and
regularly checked and cleaned as the standby runs.

So you'll need to do 2^31 transactions to prove this isn't true, which
isn't ever going to happen in testing with an assert build and nobody
with that many transactions would run an assert build anyway.

 Simon Riggs 

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