From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
---|---|
To: | Josh Berkus <josh(at)agliodbs(dot)com> |
Cc: | marcin mank <marcin(dot)mank(at)gmail(dot)com>, Greg Smith <greg(at)2ndquadrant(dot)com>, Joachim Wieland <joe(at)mcknight(dot)de>, Andrew Dunstan <andrew(at)dunslane(dot)net>, Robert Haas <robertmhaas(at)gmail(dot)com>, Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com>, pgsql-hackers(at)postgresql(dot)org |
Subject: | Re: WIP patch for parallel pg_dump |
Date: | 2010-12-07 00:22:09 |
Message-ID: | 4881.1291681329@sss.pgh.pa.us |
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Josh Berkus <josh(at)agliodbs(dot)com> writes:
>> However, if you were doing something like parallel pg_dump you could
>> just run the parent and child instances all against the slave, so the
>> pg_dump scenario doesn't seem to offer much of a supporting use-case for
>> worrying about this. When would you really need to be able to do it?
> If you had several standbys, you could distribute the work of the
> pg_dump among them. This would be a huge speedup for a large database,
> potentially, thanks to parallelization of I/O and network. Imagine
> doing a pg_dump of a 300GB database in 10min.
That does sound kind of attractive. But to do that I think we'd have to
go with the pass-the-snapshot-through-the-client approach. Shipping
internal snapshot files through the WAL stream doesn't seem attractive
to me.
While I see Robert's point about preferring not to expose the snapshot
contents to clients, I don't think it outweighs all other considerations
here; and every other one is pointing to doing it the other way.
regards, tom lane
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