From: | "Jaime Casanova" <systemguards(at)gmail(dot)com> |
---|---|
To: | "Tom Lane" <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
Cc: | "Simon Riggs" <simon(at)2ndquadrant(dot)com>, pgsql-hackers(at)postgresql(dot)org |
Subject: | Re: [COMMITTERS] pgsql: Create a GUC parametertemp_tablespacesthat allows selection of |
Date: | 2007-06-07 04:08:00 |
Message-ID: | c2d9e70e0706062108w30b766f7q3d5b6d978af33967@mail.gmail.com |
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On 6/4/07, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> Perhaps a reasonable compromise could work like this: at the first point
> in a transaction where a temp file is created, choose a random list
> element, and thereafter advance cyclically for the duration of that
> transaction. This ensures within-transaction spread-out while still
> having some randomness across backends.
>
> The reason I'm thinking per-transaction is that we could tie this to
> setting up a cached list of tablespace OIDs, which would avoid the
> overhead of repeat parsing and tablespace validity checking. We had
> rejected using a long-lived cache because of the problem of tablespaces
> getting dropped, but I think one that lasts only across a transaction
> would be OK.
>
> And the reason I'm thinking a cache is important is that if you really
> want to get any win from this idea, you need to spread the temp files
> across tablespaces *per file*, which is not the way it works now.
ok. are you doing this? or can i prepare a patch that implements this?
i guess we can allocate the memory for the list in TopTransactionContext.
--
regards,
Jaime Casanova
"Programming today is a race between software engineers striving to
build bigger and better idiot-proof programs and the universe trying
to produce bigger and better idiots.
So far, the universe is winning."
Richard Cook
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