Horton

Re: WIP patch for parallel pg_dump

Tom Lane <tgl@sss.pgh.pa.us>

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From: Tom Lane <tgl@sss.pgh.pa.us>
To: "Kevin Grittner" <Kevin.Grittner@wicourts.gov>
Cc: "Andrew Dunstan" <andrew@dunslane.net>, "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: 2010-12-06T18:24:27Z
Lists: pgsql-hackers 
"Kevin Grittner" <Kevin.Grittner@wicourts.gov> writes:
> 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?

No.  See subtransactions.

			regards, tom lane