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From "Jan Lehnardt (JIRA)" <>
Subject [jira] Commented: (COUCHDB-1084) Remove unnecessary btree lookup inside couch_db_updater
Date Wed, 09 Mar 2011 04:45:59 GMT


Jan Lehnardt commented on COUCHDB-1084:

Definitely more testing :)

Randal, if you are comparing numbers from my tests note that the first was 300s the other
200s (IIRC).

I think though your description is apt, Damien says on SSDs fsyncs are faster and cheaper,
so we see the benefits of the patch earlier. On spinning media, the waiting-for-fsync trumps
most of the time so the improvements in the now relatively smaller btree update code path
are not as significant (for the small data set until we actually save seeks in the large data

> Remove unnecessary btree lookup inside couch_db_updater
> -------------------------------------------------------
>                 Key: COUCHDB-1084
>                 URL:
>             Project: CouchDB
>          Issue Type: Improvement
>          Components: Database Core
>    Affects Versions: 1.2
>            Reporter: Damien Katz
>            Assignee: Damien Katz
>         Attachments: remove_btree_lookup.patch
> The CouchDB update process has an unnecessary btree lookup, where it reads the values
in bulks, checks for conflicts, writes the docs to disk, updates the values appropriately
and writes them to the btree out in a second step. It's possible to avoid this second step,
and instead do all the checking, doc writing and value transformation in a single btree lookup,
thereby reducing the number of btree traversals and disk IO.

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