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https://issues.apache.org/jira/browse/LUCENE-3892?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13413709#comment-13413709
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Han Jiang commented on LUCENE-3892:
-----------------------------------
bq. We could in theory subtract 1 from all these deltas (except the first one!
so maybe we add one to the docID to begin with...) so that these turn into all
0s blocks, but then at decode time we'd have to add 1 back and I'm not sure
that'd net/net be a win.
Hmm , so current strategy is: 1.for docIDs, store v[i+1]-v[i]-1; 2. for freq
and positions, store v[i] directly? Yes there are blocks with all 0s, although
very rare to see.
> Add a useful intblock postings format (eg, FOR, PFOR, PFORDelta,
> Simple9/16/64, etc.)
> -------------------------------------------------------------------------------------
>
> Key: LUCENE-3892
> URL: https://issues.apache.org/jira/browse/LUCENE-3892
> Project: Lucene - Java
> Issue Type: Improvement
> Reporter: Michael McCandless
> Labels: gsoc2012, lucene-gsoc-12
> Fix For: 4.1
>
> Attachments: LUCENE-3892-BlockTermScorer.patch,
> LUCENE-3892-direct-IntBuffer.patch, LUCENE-3892-for&pfor-with-javadoc.patch,
> LUCENE-3892-for&pfor-with-javadoc.patch, LUCENE-3892-for&pfor.patch,
> LUCENE-3892-handle_open_files.patch, LUCENE-3892_for.patch,
> LUCENE-3892_for_byte[].patch, LUCENE-3892_for_int[].patch,
> LUCENE-3892_for_unfold_method.patch, LUCENE-3892_pfor.patch,
> LUCENE-3892_pfor.patch, LUCENE-3892_pfor.patch,
> LUCENE-3892_pfor_unfold_method.patch, LUCENE-3892_pulsing_support.patch,
> LUCENE-3892_settings.patch, LUCENE-3892_settings.patch
>
>
> On the flex branch we explored a number of possible intblock
> encodings, but for whatever reason never brought them to completion.
> There are still a number of issues opened with patches in different
> states.
> Initial results (based on prototype) were excellent (see
> http://blog.mikemccandless.com/2010/08/lucene-performance-with-pfordelta-codec.html
> ).
> I think this would make a good GSoC project.
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