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From "Eks Dev (JIRA)" <>
Subject [jira] Commented: (LUCENE-1594) Use source code specialization to maximize search performance
Date Thu, 07 May 2009 21:14:45 GMT


Eks Dev commented on LUCENE-1594:

huh, it reduces hardware costs 2-3 times for larger setup! great

> Use source code specialization to maximize search performance
> -------------------------------------------------------------
>                 Key: LUCENE-1594
>                 URL:
>             Project: Lucene - Java
>          Issue Type: New Feature
>          Components: Search
>            Reporter: Michael McCandless
>            Assignee: Michael McCandless
>            Priority: Minor
>         Attachments:, LUCENE-1594.patch, LUCENE-1594.patch, LUCENE-1594.patch
> Towards eeking absolute best search performance, and after seeing the
> Java ghosts in LUCENE-1575, I decided to build a simple prototype
> source code specializer for Lucene's searches.
> The idea is to write dynamic Java code, specialized to run a very
> specific query context (eg TermQuery, collecting top N by field, no
> filter, no deletions), compile that Java code, and run it.
> Here're the performance gains when compared to trunk:
> ||Query||Sort||Filt|Deletes||Scoring||Hits||QPS (base)||QPS (new)||%||
> |1|Date (long)|no|no|Track,Max|2561886|6.8|10.6|{color:green}55.9%{color}|
> |1|Date (long)|no|5%|Track,Max|2433472|6.3|10.5|{color:green}66.7%{color}|
> |1|Date (long)|25%|no|Track,Max|640022|5.2|9.9|{color:green}90.4%{color}|
> |1|Date (long)|25%|5%|Track,Max|607949|5.3|10.3|{color:green}94.3%{color}|
> |1|Date (long)|10%|no|Track,Max|256300|6.7|12.3|{color:green}83.6%{color}|
> |1|Date (long)|10%|5%|Track,Max|243317|6.6|12.6|{color:green}90.9%{color}|
> |1|Relevance|no|no|Track,Max|2561886|11.2|17.3|{color:green}54.5%{color}|
> |1|Relevance|no|5%|Track,Max|2433472|10.1|15.7|{color:green}55.4%{color}|
> |1|Relevance|25%|no|Track,Max|640022|6.1|14.1|{color:green}131.1%{color}|
> |1|Relevance|25%|5%|Track,Max|607949|6.2|14.4|{color:green}132.3%{color}|
> |1|Relevance|10%|no|Track,Max|256300|7.7|15.6|{color:green}102.6%{color}|
> |1|Relevance|10%|5%|Track,Max|243317|7.6|15.9|{color:green}109.2%{color}|
> |1|Title (string)|no|no|Track,Max|2561886|7.8|12.5|{color:green}60.3%{color}|
> |1|Title (string)|no|5%|Track,Max|2433472|7.5|11.1|{color:green}48.0%{color}|
> |1|Title (string)|25%|no|Track,Max|640022|5.7|11.2|{color:green}96.5%{color}|
> |1|Title (string)|25%|5%|Track,Max|607949|5.5|11.3|{color:green}105.5%{color}|
> |1|Title (string)|10%|no|Track,Max|256300|7.0|12.7|{color:green}81.4%{color}|
> |1|Title (string)|10%|5%|Track,Max|243317|6.7|13.2|{color:green}97.0%{color}|
> Those tests were run on a 19M doc wikipedia index (splitting each
> Wikipedia doc @ ~1024 chars), on Linux, Java 1.6.0_10
> But: it only works with TermQuery for now; it's just a start.
> It should be easy for others to run this test:
>   * apply patch
>   * cd contrib/benchmark
>   * run python -u -delindex </path/to/index/with/deletes>
>     -nodelindex </path/to/index/without/deletes>
> (You can leave off one of -delindex or -nodelindex and it'll skip
> those tests).
> For each test, generates a single Java source file that runs
> that one query; you can open
> contrib/benchmark/src/java/org/apache/lucene/benchmark/byTask/tasks/
> to see it.  I'll attach an example.  It writes "results.txt", in Jira
> table format, which you should be able to copy/paste back here.
> The specializer uses pretty much every search speedup I can think of
> -- the ones from LUCENE-1575 (to score or not, to maxScore or not),
> the ones suggested in the spinoff LUCENE-1593 (pre-fill w/ sentinels,
> don't use docID for tie breaking), LUCENE-1536 (random access
> filters).  It bypasses TermDocs and interacts directly with the
> IndexInput, and with BitVector for deletions.  It directly folds in
> the collector, if possible.  A filter if used must be random access,
> and is assumed to pre-multiply-in the deleted docs.
> Current status:
>   * I only handle TermQuery.  I'd like to add others over time...
>   * It can collect by score, or single field (with the 3 scoring
>     options in LUCENE-1575).  It can't do reverse field sort nor
>     multi-field sort now.
>   * The auto-gen code ( is rather hideous.  It could use some
>     serious refactoring, etc.; I think we could get it to the point
>     where each Query can gen its own specialized code, maybe.  It also
>     needs to be eventually ported to Java.
>   * The script runs old, then new, then checks that the topN results
>     are identical, and aborts if not.  So I'm pretty sure the
>     specialized code is working correctly, for the cases I'm testing.
>   * The patch includes a few small changes to core, mostly to open up
>     package protected APIs so I can access stuff
> I think this is an interesting effort for several reasons:
>   * It gives us a best-case upper bound performance we can expect from
>     Lucene's normal search classes (minus algorithmic improvements eg
>     PFOR) because it makes life as easy as possible on the
>     compiler/JRE to convert to assembly.
>   * We can spin out optimization ideas from this back into the core
>     (eg LUCENE-1593 already has one example), and prioritize.  EG I
>     think given these results, optimizing for filters that support
>     random-access API is important.  As we fold speedups back into
>     core, the gains from specialization will naturally decrease.
>   * Eventually (maybe, eg as a future "experimental" module) this can
>     be used in production as a simple "search wrapper".  Ie, for a
>     given query, the specializer is checked.  If the query "matches"
>     what the specializer can handle, then the specialized code is run;
>     else we fallback to Lucene core.  Likely one would pre-compile the
>     space of all specializations, or we could compile java-on-the-fly
>     (eg what a JSP source does when it's changed) but I'm not sure how
>     costly/portable that is.

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