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From "Michael McCandless (JIRA)" <>
Subject [jira] Commented: (LUCENE-2655) Get deletes working in the realtime branch
Date Fri, 01 Oct 2010 22:03:34 GMT


Michael McCandless commented on LUCENE-2655:

bq. We've implied an additional change to the way deletes are flushed in that today, they're
flushed in applyDeletes when segments are merged, however with flush-DWPT we're applying deletes
after flushing the DWPT segment.

Why is that change needed again?  Deferring until merge kickoff is a win, eg for a non N/R/T
(heh) app, it means 1/10th the reader open cost (w/ default mergeFactor=10)?  Opening/closing
readers can be costly for a large index.

Really, some day, we ought to only apply deletes to those segments about to be merged (and
keep the buffer for the rest of the segments). Eg most merges are small... yet we'll pay huge
cost opening that massive grandaddy segment every time these small merges kick off.  But that's
another issue...

Why can't we just do what we do today?  Ie push the DWPT buffered deletes into the flushed

> Get deletes working in the realtime branch
> ------------------------------------------
>                 Key: LUCENE-2655
>                 URL:
>             Project: Lucene - Java
>          Issue Type: Improvement
>          Components: Index
>    Affects Versions: Realtime Branch
>            Reporter: Jason Rutherglen
>             Fix For: Realtime Branch
>         Attachments: LUCENE-2655.patch
> Deletes don't work anymore, a patch here will fix this.

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