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From "Aviran" <>
Subject Lucene Search has poor cpu utilization on a 4-CPU machine
Date Mon, 12 Jul 2004 14:27:04 GMT
Hi all,
First let me explain what I found out. I'm running Lucene on a 4 CPU server.
While doing some stress tests I've noticed (by doing full thread dump) that
searching threads are blocked on the method: public FieldInfo fieldInfo(int
fieldNumber) This causes for a significant cpu idle time. 
I noticed that the class org.apache.lucene.index.FieldInfos uses private
class members Vector byNumber and Hashtable byName, both of which are
synchronized objects. By changing the Vector byNumber to ArrayList byNumber
I was able to get 110% improvement in performance (number of searches per
My question is: do the fields byNumber and byName have to be synchronized
and what can happen if I'll change them to be ArrayList and HashMap which
are not synchronized ? Can this corrupt the index or the integrity of the


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