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From "Robert Muir (JIRA)" <>
Subject [jira] [Commented] (LUCENE-4225) New FixedPostingsFormat for less overhead than SepPostingsFormat
Date Tue, 17 Jul 2012 09:58:34 GMT


Robert Muir commented on LUCENE-4225:

Looks like some small gain over BulkVInt but not much...

Well, thats good enough to see which one is faster. Now lets nuke the abstraction and just
make this FORPostingsFormat that uses PackedInts?

I think its finally clear that its the abstractions here in the codec, not in the search API,
are slowing down bulk decompression :)

> New FixedPostingsFormat for less overhead than SepPostingsFormat
> ----------------------------------------------------------------
>                 Key: LUCENE-4225
>                 URL:
>             Project: Lucene - Java
>          Issue Type: Bug
>            Reporter: Michael McCandless
>            Assignee: Michael McCandless
>         Attachments: 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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