Using more than one Index will definitely decrease the searching performance. The most Lucene search latency is to load the hits. If there is no hit, the searching takes a short time, dozens milli seconds and it's a const if the document number is less than 1M. search 100 indexes will take 100 times longer.
I think it's not a good way to use many indexes when the document number is small. Also you can try ParallelMultiSearcher which search all indexes in parallel. I suppose you did not take the opening index time in the comparison. -----Original Message----- From: Ard Schrijvers [mailto:[EMAIL PROTECTED] Sent: Thursday, October 25, 2007 6:09 PM To: java-user@lucene.apache.org Subject: Performance searching over multiple indexes Hello, I am experimenting with lucene MultiSearcher and do some simple BooleanQueries in which I combine a couple of TermQueries. I am experiencing, that a single lucene index for just 100.000 docs (~10 k each) is like 100 times faster than when I have about 100 seperate indexes and use MultiSearcher. The difference specifically is visible when the number of hits gets lower (ie, more TermQueries). A single index seems to be way faster. I must admit I did optimize the single index (but I can't imagine this explains the 100X). Is it correct that a single index is much faster when the query consists of many TermQueries where the number of hits is low? Does lucene something like starting with the Term that has the lowest number of hits, and then do the consecutive terms with the lowest hits? Is this more efficient within one index, or is it the combining of the hits that makes it slower? Hopefully somebody can enlight me, thx Regards Ard -- Hippo Oosteinde 11 1017WT Amsterdam The Netherlands Tel +31 (0)20 5224466 ------------------------------------------------------------- [EMAIL PROTECTED] / [EMAIL PROTECTED] / http://www.hippo.nl -------------------------------------------------------------- --------------------------------------------------------------------- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED] --------------------------------------------------------------------- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]