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From "Kevin A. Burton" <>
Subject Re: Does a RAMDirectory ever need to merge segments... (performanceissue)
Date Wed, 21 Apr 2004 23:27:35 GMT
Gerard Sychay wrote:

>I've always wondered about this too.  To put it another way, how does
>mergeFactor affect an IndexWriter backed by a RAMDirectory?  Can I set
>mergeFactor to the highest possible value (given the machine's RAM) in
>order to avoid merging segments?
Yes... actually I was thinking of increasing these vars on the 
RAMDirectory in the hope to avoid this CPU overhead..

Also I think the var you want is minMergeDocs not mergeFactor.  the only 
problem is that the source to maybeMergeSegments says:

>   private final void maybeMergeSegments() throws IOException {
>     long targetMergeDocs = minMergeDocs;
>     while (targetMergeDocs <= maxMergeDocs) {

So I guess to prevent this we would have to set minMergeDocs to 
maxMergeDocs+1 ... which makes not sense.  Also by default maxMergeDocs 
is Integer.MAX_VALUE so that will have to be changed.

Anyway... I'm still playing with this myself. It might be easier to just 
use an ArrayList of N documents if you know for sure how big your RAM 
dir will grow to.



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