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From Simon Willnauer <simon.willna...@googlemail.com>
Subject Re: index files naming
Date Mon, 03 Jan 2011 12:51:40 GMT
Hey Bernd,

On Mon, Jan 3, 2011 at 1:35 PM, Bernd Fehling
<bernd.fehling@uni-bielefeld.de> wrote:
> Dear list,
>
> some questions about the names of the index files.
> With an older Lucene/Solr 4.x version from trunk my index looks like:
> _2t1.fdt
> _2t1.fdx
> _2t1.fnm
> _2t1.frq
> _2t1.nrm
> _2t1.prx
> _2t1.tii
> _2t1.tis
> segments_2
> segments.gen
>
> With a most recent version from trunk it looks like:
> _3a9.fdt
> _3a9.fdx
> _3a9.fnm
> _3a9_0.frq
> _3a9.nrm
> _3a9_0.prx
> _3a9_0.tii
> _3a9_0.tis
> segments_4
> segments.gen
>
> Why is there an "_0" at some files?
> Is it from Lucene or from Solr or a fault in my system?

lucene 4.0 as you might know has the ability to plug in a Codec which
has full control over how postings are stored, which format is used
and what files are written. Each Field within a segment can have its
own codec ie. field "foo" can have "Standard" and Field "bar" uses
"Pulsing" for instance. In such a case, since Pulsing is just a
wrapper around Standard - Codec, both codecs try to write the same set
of files per segment. For that reason we introduced a codec ID valid
per segment. Its is really an ordinal build from the set of codecs
used per segment. this ordinal is used to build the filenames, in your
case you only have one codec (I suppose its Standard - Codec) with the
ord "0". This ordinal is used for all files that codec writes. The
files without that ordinal (nrm, fdt, fdx and fnrm) are written by the
IndexWriter directly but the functionality behind it might be exposed
via codec sooner or later.

So, afterall this is a lucene functionality and your system is just
fine doing the right thing!
>
> I also didn't find any information at
> http://lucene.apache.org/java/3_0_3/fileformats.html

Its not a 3.3 feature - codecs are introduced in 4.0 aka. trunk.

simon
>
> Both indexes are optimized, any idea?
>
> Regards, Bernd
>
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