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From "Simon Willnauer (JIRA)" <j...@apache.org>
Subject [jira] Commented: (LUCENE-2723) Speed up Lucene's low level bulk postings read API
Date Thu, 09 Dec 2010 19:30:01 GMT

    [ https://issues.apache.org/jira/browse/LUCENE-2723?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12969885#action_12969885
] 

Simon Willnauer commented on LUCENE-2723:
-----------------------------------------

Mike, this patch is so impressive that I didn't even make it to the bottom. I think that is
bigger than the docValues branch changes, so here is my take on it.... I think this is extremely
valuable but we really should try to split that up into multiple patches. The easiest take
on it would be moving PFoR and FoR out of it to make it at least reviewable.
I would volunteer to do so if we agree on it. I am actually close to proposing a branch for
that since its truely huge and it would be easier to keep up with trunk really.  Either way,
let me know and I get it started....

simon

> Speed up Lucene's low level bulk postings read API
> --------------------------------------------------
>
>                 Key: LUCENE-2723
>                 URL: https://issues.apache.org/jira/browse/LUCENE-2723
>             Project: Lucene - Java
>          Issue Type: Improvement
>          Components: Index
>            Reporter: Michael McCandless
>            Assignee: Michael McCandless
>             Fix For: 4.0
>
>         Attachments: LUCENE-2723.patch, LUCENE-2723.patch
>
>
> Spinoff from LUCENE-1410.
> The flex DocsEnum has a simple bulk-read API that reads the next chunk
> of docs/freqs.  But it's a poor fit for intblock codecs like FOR/PFOR
> (from LUCENE-1410).  This is not unlike sucking coffee through those
> tiny plastic coffee stirrers they hand out airplanes that,
> surprisingly, also happen to function as a straw.
> As a result we see no perf gain from using FOR/PFOR.
> I had hacked up a fix for this, described at in my blog post at
> http://chbits.blogspot.com/2010/08/lucene-performance-with-pfordelta-codec.html
> I'm opening this issue to get that work to a committable point.
> So... I've worked out a new bulk-read API to address performance
> bottleneck.  It has some big changes over the current bulk-read API:
>   * You can now also bulk-read positions (but not payloads), but, I
>      have yet to cutover positional queries.
>   * The buffer contains doc deltas, not absolute values, for docIDs
>     and positions (freqs are absolute).
>   * Deleted docs are not filtered out.
>   * The doc & freq buffers need not be "aligned".  For fixed intblock
>     codecs (FOR/PFOR) they will be, but for varint codecs (Simple9/16,
>     Group varint, etc.) they won't be.
> It's still a work in progress...

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