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Date: Wed, 9 Mar 2011 18:33:07 +0000 (UTC)
From: "Randall Leeds (JIRA)" <jira@apache.org>
To: dev@couchdb.apache.org
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Subject: [jira] Commented: (COUCHDB-1084) Remove unnecessary btree lookup
 inside couch_db_updater
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    [ https://issues.apache.org/jira/browse/COUCHDB-1084?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13004709#comment-13004709 ] 

Randall Leeds commented on COUCHDB-1084:
----------------------------------------

Relaximation uses a fixed number of writers and readers and fires off a new request whenever one finishes.
That means that a decrease in write latency means more writes overall and if any resource was saturated before it likely means a commensurate impact elsewhere, since there's no free lunch.

Jan, if you can find the time I think running the writes only test would be interesting. I would expect pure gains in all areas.
>From a code perspective we already know for sure we haven't made reads worse in general.

> Remove unnecessary btree lookup inside couch_db_updater
> -------------------------------------------------------
>
>                 Key: COUCHDB-1084
>                 URL: https://issues.apache.org/jira/browse/COUCHDB-1084
>             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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