Horton

Re: WIP patch for parallel pg_dump

Kevin Grittner <kevin.grittner@wicourts.gov>

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From: "Kevin Grittner" <Kevin.Grittner@wicourts.gov>
To: "Andrew Dunstan" <andrew@dunslane.net>, "Tom Lane" <tgl@sss.pgh.pa.us>
Cc: "Greg Smith" <greg@2ndquadrant.com>, "Heikki Linnakangas" <heikki.linnakangas@enterprisedb.com>, "Robert Haas" <robertmhaas@gmail.com>, "Joachim Wieland" <joe@mcknight.de>, "pgsql-hackers" <pgsql-hackers@postgresql.org>
Date: 2010-12-06T18:11:18Z
Lists: pgsql-hackers 
Tom Lane <tgl@sss.pgh.pa.us> wrote:
 
>> I'm still not convinced that using shared memory is a bad way to 
>> pass these around. Surely we're not talking about large numbers
>> of them.  What am I missing here?
> 
> They're not of a very predictable size.
 
Surely you can predict that any snapshot is no larger than a fairly
small fixed portion plus sizeof(TransactionId) * MaxBackends?  So,
for example, if you're configured for 100 connections, you'd be
limited to something under 1kB, maximum?
 
-Kevin