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Date: Tue, 21 Jun 2011 12:28:24 -0400
Message-ID: <BANLkTimxoDvM62Q5nT1P5YmdVzGxJWYAvQ@mail.gmail.com>
Subject: Re: About IndexReader.reopen with very similar indexes
From: Michael McCandless <lucene@mikemccandless.com>
To: java-user@lucene.apache.org
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Reopening is based entirely on the latest segments_N file present in the in=
dex.

Lucene loads that file and checks if it refers to any new segments not
already open and if so opens those new ones.  And segments in common
with what the reader already has open (ie same segment name) are
simply reused.

Lucene doesn't look at file modification times, etc.

Mike McCandless

http://blog.mikemccandless.com

On Mon, Jun 20, 2011 at 5:13 AM, Marc Sturlese <marc.sturlese@gmail.com> wr=
ote:
> Hey there,
> I have a doubt about the behaviour of IndexReader.reopen.
> I have a tomcat server holding a lucene index over an IndexSearcher. If I
> move the index.folder to index.folder.old and another index, let's say
> index.folder.2 to index.folder and then I reopen readers, something weird
> happen if the first index and the second have very similar size and are
> built from scratch. It seems that when I get the new reader and compare w=
ith
> the new one:
>
> =A0IndexReader reader =3D ...
> =A0...
> =A0IndexReader newReader =3D r.reopen();
> =A0if (newReader !=3D reader) {
> =A0... =A0 =A0 // reader was reopened
> =A0 reader.close();
> =A0}
> =A0reader =3D newReader;
> =A0...
>
> Lucene does not detect that are different indexes.
> Here you can see both indexes (have same number of files and names are
> similar, but sizes are a bit different, as contained documents are not
> exactly the same).
> *This does not happen if indexes have much more differents sizes (and so,
> file names will not be equal, ex: _4.fdt, etc)
>
> Index1:
> -rw-r--r-- =A0 1 marc =A0admin =A0269289634 15 Jun 15:52 _3.fdt
> -rw-r--r-- =A0 1 marc =A0admin =A0 =A02066764 15 Jun 15:52 _3.fdx
> -rw-r--r-- =A0 1 marc =A0admin =A0 =A0 =A0 =A0463 15 Jun 15:52 _3.fnm
> -rw-r--r-- =A0 1 marc =A0admin =A0 40358787 15 Jun 15:52 _3.frq
> -rw-r--r-- =A0 1 marc =A0admin =A0 =A01033384 15 Jun 15:52 _3.nrm
> -rw-r--r-- =A0 1 marc =A0admin =A0 27014923 15 Jun 15:52 _3.prx
> -rw-r--r-- =A0 1 marc =A0admin =A0 =A0 234797 15 Jun 15:52 _3.tii
> -rw-r--r-- =A0 1 marc =A0admin =A0 19322234 15 Jun 15:52 _3.tis
> -rw-r--r-- =A0 1 marc =A0admin =A0 =A0 =A0 =A0 20 15 Jun 15:52 segments.g=
en
> -rw-r--r-- =A0 1 marc =A0admin =A0 =A0 =A0 =A0298 15 Jun 15:52 segments_2
>
> Index2:
> -rw-r--r-- =A0 1 marc =A0admin =A0269044254 15 Jun 15:52 _3.fdt
> -rw-r--r-- =A0 1 marc =A0admin =A0 =A02068116 15 Jun 15:52 _3.fdx
> -rw-r--r-- =A0 1 marc =A0admin =A0 =A0 =A0 =A0463 15 Jun 15:52 _3.fnm
> -rw-r--r-- =A0 1 marc =A0admin =A0 40320465 15 Jun 15:52 _3.frq
> -rw-r--r-- =A0 1 marc =A0admin =A0 =A01034060 15 Jun 15:52 _3.nrm
> -rw-r--r-- =A0 1 marc =A0admin =A0 26967519 15 Jun 15:52 _3.prx
> -rw-r--r-- =A0 1 marc =A0admin =A0 =A0 235895 15 Jun 15:52 _3.tii
> -rw-r--r-- =A0 1 marc =A0admin =A0 19372446 15 Jun 15:52 _3.tis
> -rw-r--r-- =A0 1 marc =A0admin =A0 =A0 =A0 =A0 20 15 Jun 15:52 segments.g=
en
> -rw-r--r-- =A0 1 marc =A0admin =A0 =A0 =A0 =A0298 15 Jun 15:52 segments_2
>
> Can someone explain me the lucene criteria to decide if a segment has
> changed or not?
> Thanks in advance.
>
>
> --
> View this message in context: http://lucene.472066.n3.nabble.com/About-In=
dexReader-reopen-with-very-similar-indexes-tp3085456p3085456.html
> Sent from the Lucene - Java Users mailing list archive at Nabble.com.
>
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