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https://issues.apache.org/jira/browse/COUCHDB-568?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12776597#action_12776597
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Adam Kocoloski commented on COUCHDB-568:
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Yes, an error could make the state go backwords, just like killing couch before
the fsync.
> 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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