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From "Michael McCandless (JIRA)" <>
Subject [jira] Commented: (LUCENE-2773) Don't create compound file for large segments by default
Date Wed, 24 Nov 2010 19:03:13 GMT


Michael McCandless commented on LUCENE-2773:

OK i think for 2.9/3.0, I will only backport the "don't make a CFS if the merged segment is
large" change; that change will reduce temp disk space required.

I think the change to maxMergeMB / take deletions into account is too big for 2.9/3.0.

So for 3.x/trunk (which already take deletions into account by default), I'll switch maxMergeMB
default to 2 GB.  I think this is an OK default given that it means your biggest segments
will range from 2GB - 20GB.

> Don't create compound file for large segments by default
> --------------------------------------------------------
>                 Key: LUCENE-2773
>                 URL:
>             Project: Lucene - Java
>          Issue Type: Improvement
>          Components: Index
>            Reporter: Michael McCandless
>            Assignee: Michael McCandless
>             Fix For: 2.9.4, 3.0.3, 3.1, 4.0
>         Attachments: LUCENE-2773.patch
> Spinoff from LUCENE-2762.
> CFS is useful for keeping the open file count down.  But, it costs
> some added time during indexing to build, and also ties up temporary
> disk space, causing eg a large spike on the final merge of an
> optimize.
> Since MergePolicy dictates which segments should be CFS, we can
> change it to only build CFS for "smallish" merges.
> I think we should also set a maxMergeMB by default so that very large
> merges aren't done.

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