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Re: Multiple entires for the same key in the strings table

From: C. Michael Pilato <cmpilato_at_collab.net>
Date: Sun, 01 Jun 2008 22:34:41 -0400

Vyacheslav V. Zholudev wrote:
> Hey all!
> Could somebody explain me please, why we can have multiple entries for
> the same key in the 'strings' table in case of BDB? I mean what are the
> reasons behind it?

We get data piecemeal, in chunks, though the interfaces that write file
contents to the 'strings' table. We used to simply append this data to the
one "row" for that string ID, but then we noticed that Berkeley DB's
write-ahead logging subsystem wanted to replicate the whole string-so-far
value over and over again in the log.* files (so the transaction could be
replayed if necessary). This caused obnoxious bloat of the disk. We solved
this issue (and possibly some performance related performance pains, though
I don't recall for sure) by simply splitting each of these incoming chunks
into its own "row", but with the same key (the collection of which we
traverse with the magic of cursors).

C. Michael Pilato <cmpilato_at_collab.net>
CollabNet   <>   www.collab.net   <>   Distributed Development On Demand

Received on 2008-06-02 04:35:03 CEST

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