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From "Michael McCandless (JIRA)" <>
Subject [jira] [Commented] (LUCENE-4225) New FixedPostingsFormat for less overhead than SepPostingsFormat
Date Thu, 02 Aug 2012 20:01:02 GMT


Michael McCandless commented on LUCENE-4225:

OK I committed the fix: Block/PackedPF was incorrectly encoding offsets as startOffset - lastEndOffset.
 It must instead be startOffset - lastStartOffset because it is possible (though rare) for
startOffset - lastEndOffset to be negative.

I also separately committed a fix for NPEs that tests were hitting when the index didn't index
payloads nor offsets.  Tests should now pass for BlockPF and BlockPackedPF...
> New FixedPostingsFormat for less overhead than SepPostingsFormat
> ----------------------------------------------------------------
>                 Key: LUCENE-4225
>                 URL:
>             Project: Lucene - Core
>          Issue Type: Bug
>            Reporter: Michael McCandless
>            Assignee: Michael McCandless
>         Attachments: LUCENE-4225-on-rev-1362013.patch, LUCENE-4225.patch, LUCENE-4225.patch,
LUCENE-4225.patch, LUCENE-4225.patch
> I've worked out the start at a new postings format that should have
> less overhead for fixed-int[] encoders (For,PFor)... using ideas from
> the old bulk branch, and new ideas from Robert.
> It's only a start: there's no payloads support yet, and I haven't run
> Lucene's tests with it, except for one new test I added that tries to
> be a thorough PostingsFormat tester (to make it easier to create new
> postings formats).  It does pass luceneutil's performance test, so
> it's at least able to run those queries correctly...
> Like Lucene40, it uses two files (though once we add payloads it may
> be 3).  The .doc file interleaves doc delta and freq blocks, and .pos
> has position delta blocks.  Unlike sep, blocks are NOT shared across
> terms; instead, it uses block encoding if there are enough ints to
> encode, else the same Lucene40 vInt format.  This means low-freq terms
> (< 128 = current default block size) are always vInts, and high-freq
> terms will have some number of blocks, with a vInt final block.
> Skip points are only recorded at block starts.

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