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From "Filipe Manana (JIRA)" <>
Subject [jira] [Commented] (COUCHDB-1270) Rewrite the view engine
Date Mon, 05 Sep 2011 01:02:09 GMT


Filipe Manana commented on COUCHDB-1270:

Great work here Paul, it's really nice.

I haven't done a very detailed analysis, but so far, 2 minor details:

1) In couch_index_compactor (patch 2), the pid in state is assigned the default value of 'nil',
but everywhere else in the module, you match against/use 'undefined'. It would be better to
use the same everywhere, or an is_pid(Pid) call;

2) When a view compaction is canceled, the partially compacted file is not deleted (unlike
trunk's current behaviour). Since we don't support resuming of view compaction, it's useless
to leave it there and be deleted only on the next compaction request. Plus, leaving it there,
it can prevent other compactions from succeeding due to not enough free disk space

> Rewrite the view engine
> -----------------------
>                 Key: COUCHDB-1270
>                 URL:
>             Project: CouchDB
>          Issue Type: Improvement
>          Components: JavaScript View Server
>            Reporter: Paul Joseph Davis
>         Attachments: 0001-Minor-changes-for-new-indexing-engine.patch, 0002-Create-the-couch_index-application.patch,
0003-Create-the-couch_mrview-application.patch, 0004-Remove-the-old-view-engine.patch
> The view engine has been creaky and cluttered. As shown by GeoCouch, adding new indexers
basically involves copying the entire view engine and hacking the parts that are different.
In short, the opposite of good engineering.
> Over the last couple weeks I've refactored the view engine and reimplemented the map/reduce
view engine. These changes are 100% internal and no external behavior has changed. Performance
is just a tiny bit better than trunk. I did do some playing trying to improve view update
times and there are some dances we could do, but for the time being I wanted to keep the same
general architecture for updates so that the changes are minimal.

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