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From Doug Cutting <>
Subject Re: potential indexing perormance improvement for compound index - cut IO - have more files though
Date Sat, 16 Dec 2006 18:21:09 GMT
Marvin Humphrey wrote:
> Out of curiosity, does the non-compound format yield any search-time 
> benefits?

Yes.  On 32-bit systems with indexes larger than 1GB or so, memory 
mapping is impractical, so synchronization is required around shared 
file handles (using Java's classic i/o APIs, w/o pread).  The 
non-compound format, with more files, has fewer synchronization 
bottlenecks.  One could of course achieve the same improvements in other 
ways, e.g., by pooling multiple IndexReaders per index, but in straight 
A-to-B comparisons, folks see better throughput with non-compound 
indexes for multi-threaded applications.


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