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From Chitra R <chithu.r...@gmail.com>
Subject Re: Searcher Performance
Date Fri, 17 Feb 2017 14:13:03 GMT
Hey, thank you so much. I got it.

I have

   - 10 lakh docs, 30 fields in my index
   - opening new searcher at initial search and
   - there will be no filesystem cache for my current index

At initial search, I search across only one field out of 30 fields in my
index.

My question is,

*At initial search, Whether the required page (os pages of Lucene index
files) for that field (a single field) will be loaded to filesystem cache
or all the fields info will be loaded to filesystem cache from disk?*


Regards,
Chitra

On Fri, Feb 17, 2017 at 7:05 PM, Adrien Grand <jpountz@gmail.com> wrote:

> Regarding whether the filesystem cache helps, you could look at whether
> there is some disk activity while your queries are running.
>
> When everything is in the filesystem cache, the latency of search requests
> for simple queries (term queries and combinations through boolean queries)
> usually mostly depends on the total number of matches since Lucene needs to
> call the collector on every match.
>
> Le ven. 17 févr. 2017 à 10:09, Chitra R <chithu.r111@gmail.com> a écrit :
>
> > Hi,
> >      While working with Searcher.Search, I have noticed a difference in
> > their performance. I have 10 lakh documents and 30 fields in my index. I
> > have performed three searches using different queries in a sequential
> > manner. At search time, I used MMapDirectory and index is opened.
> >
> > *case1: *
> >
> >    - During the first search, I ran the Query Say (new TermQuery(new
> >    Term("name","Chitra"))) and which yields 1 lakh documents as result.
> > Time
> >    taken for first search = 50 - 60 ms nearly.
> >    - And for the second search, I ran the Query Say (new TermQuery(new
> >    Term("animal","lion"))) which also yields 1 lakh documents as result.
> > Time
> >    taken for Second search = 50 - 60 ms nearly.
> >    - And for the third search,  I ran the Query Say (new TermQuery(new
> >    Term("bird","peacock"))) which also yields 1 lakh documents as result.
> >    Time taken for Third search = 50 - 60 ms nearly.
> >
> > In this case, why does searcher.search take the same search time for
> > different queries?
> >
> > *case2:*
> >
> > Suppose if I ran the same query twice, Searcher.search took less time
> than
> > the previous search because of os cache.
> >
> > *Based on above observation, *
> >
> > During initial search, only the required portion of index files will be
> > loaded to i/o cache. And for the next search, if the required portion is
> > not present in os cache,
> >
> > Will it take time to read that files from disk? If so, this is the reason
> > behind searcher.search is taking the nearly same search time for
> different
> > queries.
> >
> >
> > Regards,
> > Chitra
> >
>

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