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From Uwe Schindler <>
Subject Re: How important is single segment optimization to Search time performance?
Date Sun, 18 Aug 2013 19:12:07 GMT

I would suggest to read:

In general, if the index changes often, don't force merges. IndexWriter automatically merges
to a suitable number of segments. 


Gili Nachum <> schrieb:
>Hi there Lucene samurai!
>*I was wondering how important is single segment merging for search
>performance compared to a more modest merging goal like merging down to
>just 4 segment.
>Currently my system merges every evening, it takes ~1-2 hours, and
>invalidates the File-system cache.
>What would happen if I'll reduce the merging target to just 4 segments?
>e.g., When searching a term, does Lucene needs to visit each segment
>seek operation) to access the relevant posting list? If not then what's
>advantage of merging down segments (besides open files limit).
>*Was wondering if anyone has tested # of segments against search time
>I should add I have ~10 indexes, at a total size of 50GB, and I use
>mutli-index searcher to search over them (Lucene 3.0.3 - yeah it's old
>know). The index is updated every 15min.
>Gili Nachum.

Uwe Schindler
H.-H.-Meier-Allee 63, 28213 Bremen
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