otis_gospodnetic at yahoo
Nov 17, 2009, 11:37 AM
Post #2 of 5
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Re: Why Lucene takes longer time for the first query and less for subsequent ones
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Hello,
Most likely due to the operating system caching the relevant portions of the index after the first set of queries.
Otis
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----- Original Message ----
> From: Dinh <pcdinh [at] gmail>
> To: java-user [at] lucene
> Sent: Tue, November 17, 2009 12:39:14 PM
> Subject: Why Lucene takes longer time for the first query and less for subsequent ones
>
> Hi all,
>
> I made a list of 4 simple, singe term queries and do 4 searches via Lucene
> and find that if the term is used for search in the first time, Lucene takes
> quite a bit time to handle it.
>
> - Query A
> 00:27:28,781 INFO LuceneSearchService:151 - Internal search took
> 328.21463ms
> 00:27:28,781 INFO SearchController:86 - Page rendered in 338.29553ms
>
> - Query B
> 00:27:39,171 INFO LuceneSearchService:151 - Internal search took
> 480.30908ms
> 00:27:39,187 INFO SearchController:86 - Page rendered in 493.07327ms
>
> - Query C
> 00:27:46,765 INFO LuceneSearchService:151 - Internal search took
> 189.33635ms
> 00:27:46,765 INFO SearchController:86 - Page rendered in 195.43823ms
>
> - Query D
> 00:28:00,312 INFO LuceneSearchService:151 - Internal search took 330.3596ms
> 00:28:00,328 INFO SearchController:86 - Page rendered in 347.34747ms
>
>
> It looks no good at the first glance because I have only 500 000 indexed
> documents. However, when I searched them again I found that Lucene run much
> faster.
>
> - Query A
> 00:28:04,046 INFO LuceneSearchService:151 - Internal search took 3.90301ms
> 00:28:04,062 INFO SearchController:86 - Page rendered in 15.694173ms
>
> - Query C
> 00:28:15,390 INFO LuceneSearchService:151 - Internal search took 1.425879ms
> 00:28:15,390 INFO SearchController:86 - Page rendered in 7.946541ms
>
> - Query D
> 00:28:26,031 INFO LuceneSearchService:151 - Internal search took 1.849956ms
> 00:28:26,046 INFO SearchController:86 - Page rendered in 12.023037ms
>
> - Query B
> 00:28:31,609 INFO LuceneSearchService:151 - Internal search took 1.668648ms
> 00:28:31,625 INFO SearchController:86 - Page rendered in 15.57237ms
>
> Why does it happens? Does it mean that Lucene has an internal cache engine,
> just like MySQL query result cache or Oracle query execution plan cache?
>
> Thanks
>
> Dinh
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