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https://issues.apache.org/jira/browse/LUCENE-3490?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13139662#comment-13139662
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Uwe Schindler edited comment on LUCENE-3490 at 10/30/11 4:46 PM:
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A good example how this could work is Unicode Policeman's
java.nio.charset.Charset and java.nio.charset.spi.CharsetProvider. We can copy
lots of stuff from there. The lookup of a codec by string-name is exactly like
looking up a charset by name. Also for Luke we can provide the iterator of all
codecs available, that appends all registered SPIs codecs. And so on.
Once Robert have cleaned up the branch I will happily help here. The code is
already in my head, I just need a working base to implement it.
NOTE: As we are on Java 1.6 for trunk, we can use the now public
java.util.ServiceLoader discovery and don't need to use sun.misc or
java.awt.image.spi classes.
was (Author: thetaphi):
A good example how this could work is Unicode Policeman's
java.nio.charset.Charset and java.nio.charset.spi.CharsetProvider. We can copy
lots of stuff from there. The lookup of a codec by string-name is exactly like
looking up a charset by name. Also for Luke we can provide the iterator of all
codecs available, that appends all registered SPIs codecs. And so on.
Once Robert have cleaned up the branch I will happily help here. The code is
already in my head, I just need a working base to implement it.
> Restructure codec hierarchy
> ---------------------------
>
> Key: LUCENE-3490
> URL: https://issues.apache.org/jira/browse/LUCENE-3490
> Project: Lucene - Java
> Issue Type: Improvement
> Reporter: Robert Muir
> Fix For: 4.0
>
>
> Spinoff of LUCENE-2621. (Hoping we can do some of the renaming etc here in a
> rote way to make progress).
> Currently Codec.java only represents a portion of the index, but there are
> other parts of the index
> (stored fields, term vectors, fieldinfos, ...) that we want under codec
> control. There is also some
> inconsistency about what a Codec is currently, for example Memory and Pulsing
> are really just
> PostingsFormats, you might just apply them to a specific field. On the other
> hand, PreFlex actually
> is a Codec: it represents the Lucene 3.x index format (just not all parts
> yet). I imagine we would
> like SimpleText to be the same way.
> So, I propose restructuring the classes so that we have something like:
> * CodecProvider <-- codec name to Class resolution only
> * Codec <-- represents the index format (PostingsFormat + FieldsFormat + ...)
> * PostingsFormat: this is what Codec controls today, and Codec will return
> one of these for a field.
> * FieldsFormat: Stored Fields + Term Vectors + FieldInfos?
> I think for PreFlex, it doesnt make sense to expose its PostingsFormat as a
> 'public' class, because preflex
> can never be per-field so there is no use in allowing you to configure
> PreFlex for a specific field.
> Similarly, I think we should do the same thing for SimpleText. Nobody needs
> SimpleText for production, it should
> just be a Codec where we try to make as much of the index as plain text and
> simple as possible for debugging/learning/etc.
> So we don't need to expose its PostingsFormat. On the other hand, I don't
> think we need Pulsing or Memory codecs,
> because its pretty silly to make your entire index use one of their
> PostingsFormats. To parallel with analysis:
> PostingsFormat is like Tokenizer and Codec is like Analyzer, and we don't
> need Analyzers to "show off" every Tokenizer.
> Later, once we abstract FieldInfos reading/writing out of o.a.l.index into
> codec control, we can also then
> move the baked in PerFieldCodecWrapper out (it would basically be
> PerFieldPostingsFormat). Privately it would
> write the ids to the file like it does today. all 3.x hairy backwards code
> would move to PreflexCodec. SimpleTextCodec
> would get a plain text fieldinfos impl, etc.
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