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Date: Thu, 22 Apr 2010 07:11:55 -0400
Message-ID: <k2o9ac0c6aa1004220411z4ae12992nf78d2943d4ec7fea@mail.gmail.com>
Subject: Re: Reopening a Searcher for each request
From: Michael McCandless <lucene@mikemccandless.com>
To: java-user@lucene.apache.org
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It's the IndexReader that's costly to open/warm, so ideally it should
be opened once and shared.

The Searchers do very little on construction so re-creating per query
should be OK.

Mike

On Thu, Apr 22, 2010 at 6:38 AM, Samarendra Pratap <samarzone@gmail.com> wr=
ote:
> Greetings to all.
> =A0I have read at so many places that we should not open a Searcher for e=
ach
> request for the sake of performance, but I have always been wondering
> whether it is actually Searcher or Reader?
>
> =A0I have a group of index amounting to 23G which actually contains of
> different index directories. The structure is something like following
>
> Main directory
> |
> |_________ country1
> | =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 |___ country1-time1 (actual ind=
ex)
> | =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 |___ country1-time2 (actual ind=
ex)
> | =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 |___ country1-time3 (actual ind=
ex)
> |
> |_________ country2
> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 |___ country2-time1 (actual index=
)
> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 |___ country2-time2 (actual index=
)
> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 |___ country2-time3 (actual index=
)
>
> =A0When application starts I open IndexReaders on all of actual index
> directories (country1-time1, country1-tim2, .... country2-time3) and keep
> them in a pool.
>
> =A0At the time of search, IndexSearchers are created by selecting the
> appropriate IndexReaders from the pool. These IndexSearchers in turn are
> used to create a ParallelMultiSearcher. Constructors of IndexSearcher and
> ParallelMultiSearcher are run for every request.
>
> =A0Now I believe that creating a pool of ParallelMultiSearcher itself is =
a
> good idea but* I wanted to know if reopening **IndexSearchers** will real=
ly
> degrade performance irrespective of **IndexReaders** being opened once*.
>
> In my performance tests (which may not be very comprehensive) I didn't fi=
nd
> any noticeable difference.
>
> Please throw some light.
>
>
> --
> Regards,
> Samar
>

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