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Re: A performance tip

From: <mbk_at_boredom.org>
Date: 2003-01-23 20:39:58 CET

On Thu, Jan 23, 2003 at 10:49:07AM -0800, Bill Tutt wrote:
 The smaller our BDB transactions are the better off our datastore will
 be for scalability. As far as I know, BDB doesn't let us get away with
 doing dirty reads (no read lock was acquired) on known non-changeable
 data. BDB also doesn't do lock escalation. I don't recall whether or not
 BDB supports row locks or not. It might only support page locks. If
 that's the case the smaller our BDB transactions the less time we hold
 read locks open that prevent writing threads from getting about their
 business of creating new Subversion transactions (or whatever).

IANA BDB person, but db_open supports:

   DB_DIRTY_READ Support dirty reads; that is, transactions, cursors and read operations in the database may request the return of modified but not yet committed data.

and db_get has:

   DB_DIRTY_READ Read modified but not yet committed data. Silently ignored if the DB_DIRTY_READ flag was not specified when the underlying database was opened.


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Received on Sat Oct 14 02:09:51 2006

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