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From "Paul Joseph Davis (JIRA)" <j...@apache.org>
Subject [jira] Commented: (COUCHDB-568) When delayed_commits = true, keep updated btree nodes in memory until the commit
Date Wed, 11 Nov 2009 19:40:39 GMT

    [ https://issues.apache.org/jira/browse/COUCHDB-568?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12776603#action_12776603
] 

Paul Joseph Davis commented on COUCHDB-568:
-------------------------------------------

Oh, good point. I might have to focus on trying to write that code for the b~tree updater.
It definitely sounds fun.

> When delayed_commits = true, keep updated btree nodes in memory until the commit
> --------------------------------------------------------------------------------
>
>                 Key: COUCHDB-568
>                 URL: https://issues.apache.org/jira/browse/COUCHDB-568
>             Project: CouchDB
>          Issue Type: Improvement
>    Affects Versions: 0.10
>            Reporter: Adam Kocoloski
>
> rnewson reported on IRC that the new batch=ok implementation results in significantly
larger overhead in the .couch files.  This makes sense; the old batch mode waited 1 second
before saving, but the new implementation just updates the doc asynchronously.  With fast
hardware and moderate write rates it's likely that each document is being written separately.
> The overhead presumably arises from frequently updated btree inner nodes being written
to disk many times over.  I'm interested in exploring a modification of the delayed_commits
mode whereby the updated btree nodes are not actually written to disk immediately, but are
instead held in memory until the commit.  I'd like to think that this will result in more
compact files without any decrease in durability.  New read requests would still be able to
access these in-memory nodes.
> I realize the notion that updates go directly to disk is baked pretty deeply into couch_btree,
but I still thought this was worth bringing up to a wider audience.

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