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From Doug Cutting <>
Subject Re: release & migration plan
Date Mon, 12 Jul 2004 17:34:03 GMT
fp235-5 wrote:
> I'd like to be able to modify the indexInterval (tii file) from the IndexWriter.   
> I tried it recently and it proved to increase performances, especially for large
> queries. Do you think there would be a reason not to give access to that parameter?

I agree.  We should add this, but with caution.  I haven't added this in 
the past because I feared that, like mergeFactor, it is rife for abuse, 
that folks will set it to very large or small values and then loudly 
proclaim that Lucene is broken.

If we make it easily changeable then we should clearly document (a) that 
one should change it with caution; (b) what reasonable values are; and 
(c) what the effects are of setting it high (low memory use, somewhat 
slower search, faster IndexReader creation) and low (high memory use, 
somewhat faster search, slower IndexReader creation).  A formula for 
memory use and IndexReader creation speed should be included 
(proportional to total number of terms) and a description of impact on 
search performance (constant factor per query term, regardless of index 
size: greater impact for small indexes, less for large indexes).

In particular, we want to discourage folks with very large indexes or 
who re-open indexes frequently from setting this to small values.

Would you like to draft the javadoc and make a patch file for this 
change?  This would not be an incompatible change and could be done at 
any time.


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