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https://issues.apache.org/jira/browse/LUCENE-1593?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Shai Erera updated LUCENE-1593:
-------------------------------
Attachment: PerfTest.java
LUCENE-1593.patch
The patch implements all that has been suggested except:
* pre-populating the queue in TopFieldCollector - as was noted here previously,
this seems to remove the 'if (queueFull)' check but add another 'if' in
FieldComparator (which may be executed several times per collect().
* Move initCountingSumScorer() to BS2's ctor and add(). That's because if more
than one Scorer is added we create a DisjunctionSumScorer, which initializes
its queue by calling next() on the passed-in Scorer. Therefore if we call
initCountingSumScorer for every Scorer added, we advance that Scorer as well as
all the previous ones. I chose to discard that optimization, which only affects
next() and skipTo().
The patch also includes the fix for TestSort in the 2.4 back_compat branch. I
only fixed TestSort, and not MultiSearcher and ParallelMultiSearcher.
All tests pass.
I also ran some performance measurements (all on SRV 2003):
|| JRE || sort || best time (trunk) || best time (patch) || diff (%) ||
| SUN 1.6 | int | 1017.59 | 1015.96 | {color:green}~1%{color} |
| SUN 1.6 | doc | 767.49 | 763.20 | {color:green}~1%{color} |
| IBM 1.5 | int | 1018.77 | 1017.39 | {color:green}~1%{color} |
| IBM 1.5 | doc | 768.10 | 764.14 | {color:green}~1%{color} |
As you can see, there is a slight performance improvement, but nothing too
dramatic.
You are welcome to review the patch as well as run the PerfTest I attached. It
accepts two arguments: <indexDir> and [sort]. 'sort' is optional and if not
defined it sorts by doc. Otherwise, whatever you pass there, it sorts by int.
> Optimizations to TopScoreDocCollector and TopFieldCollector
> -----------------------------------------------------------
>
> Key: LUCENE-1593
> URL: https://issues.apache.org/jira/browse/LUCENE-1593
> Project: Lucene - Java
> Issue Type: Improvement
> Components: Search
> Reporter: Shai Erera
> Fix For: 2.9
>
> Attachments: LUCENE-1593.patch, PerfTest.java
>
>
> This is a spin-off of LUCENE-1575 and proposes to optimize TSDC and TFC code
> to remove unnecessary checks. The plan is:
> # Ensure that IndexSearcher returns segements in increasing doc Id order,
> instead of numDocs().
> # Change TSDC and TFC's code to not use the doc id as a tie breaker. New docs
> will always have larger ids and therefore cannot compete.
> # Pre-populate HitQueue with sentinel values in TSDC (score = Float.NEG_INF)
> and remove the check if reusableSD == null.
> # Also move to use "changing top" and then call adjustTop(), in case we
> update the queue.
> # some methods in Sort explicitly add SortField.FIELD_DOC as a "tie breaker"
> for the last SortField. But, doing so should not be necessary (since we
> already break ties by docID), and is in fact less efficient (once the above
> optimization is in).
> # Investigate PQ - can we deprecate insert() and have only
> insertWithOverflow()? Add a addDummyObjects method which will populate the
> queue without "arranging" it, just store the objects in the array (this can
> be used to pre-populate sentinel values)?
> I will post a patch as well as some perf measurements as soon as I have them.
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