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

From: Vyacheslav V. Zholudev <vyacheslav.zholudev_at_gmail.com>
Date: Sun, 13 Jul 2008 14:41:43 +0200

Michael, you said that you used to write data into one row in BDB. How
did you do that? In particular, how did you accumulate the chunks which
were got from a stream? Am I right that you had to cache everything
somewhere and then when the whole fulltext was comprised, you flushed
the whole fulltext data to BDB?

C. Michael Pilato wrote:
> 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).
>

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Received on 2008-07-15 02:18:30 CEST

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