On 6/4/07, Tom Lane <[EMAIL PROTECTED]> 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.
"Programming today is a race between software engineers striving to
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So far, the universe is winning."
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TIP 9: In versions below 8.0, the planner will ignore your desire to
choose an index scan if your joining column's datatypes do not