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Posted to dev@lucene.apache.org by Grant Ingersoll <gs...@apache.org> on 2009/09/22 15:12:48 UTC
Re: How to leverage the LogMergePolicy "calibrateSizeByDeletes" patch in Solr ?
On Sep 21, 2009, at 9:35 PM, John Wang wrote:
> Jason:
>
> You are missing the point.
>
> The idea is to avoid merging of large segments. The point of
> this MergePolicy is to balance segment merges across the index. The
> aim is not to have 1 large segment, it is to have n segments with
> balanced sizes.
>
> When the large segment is out of the IO cache, replacing it is
> very costly. What we have done is to split the cost over time by
> having more frequent but faster merges.
>
Yeah, I have seen this in action several times as well. See also some
discussion at: http://www.lucidimagination.com/search/document/bd53b0431f7eada5/concurrentmergescheduler_and_mergepolicy_question
.