Re: [PATCH] 2PC state files on shared memory

From: Michael Paquier <michael(dot)paquier(at)gmail(dot)com>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: [PATCH] 2PC state files on shared memory
Date: 2009-08-10 02:36:45
Message-ID: c64c5f8b0908091936n78b8d0ch9bfa029e0c9a15af@mail.gmail.com
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After making a lot of tests, state file size is not more than 600B.
In some cases, it reached a maximum of size of 712B and I used such
transactions in my tests.

> I think setting the size parameter for this would be a frightfully
> difficult problem; the fact that average installations wouldn't use it
> doesn't make that any better for those who would. After our bad
> experiences with fixed-size FSM, I'm pretty wary of introducing new
> fixed-size structures that the user is expected to figure out how to
> size.
The patch has been designed such as if a state file has a size higher than
what has been decided by the user,
it will be written to disk instead of shared memory. So it will not
represent a danger for teh stability of the system.
The case of too many prepared transactions is also covered thanks to
max_prepared_transactions.

Regards,

--
Michael Paquier

NTT OSSC

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