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https://issues.apache.org/jira/browse/LUCENE-584?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12487456
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Doron Cohen commented on LUCENE-584:
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...right, your diff-txt had the Match tasks - I missed that - checked it, it is
exactly what I did, so we're ok here.
When you rerun, you may want to use my alg - to compare the two approaches in
one run. You can run this by something like:
ant run-task -Dtask.mem=256M -Dtask.alg=conf\matcher-vs-bitset.alg
Also, to get cleaner results, add the line:
ResetSystemSoft
just in the beginning of the "search round" - this resets the (query) inputs
and also calls GC.
I tried like this twice, and got inconsistent results:
When the bitset searches preceded the match searches:
[java] Operation round runCnt recsPerRun rec/s
elapsedSec avgUsedMem avgTotalMem
[java] SrchBitsSamRdr_5000 - 10 5000 706.4
70.78 7,511,219 16,573,645
[java] SrchMtchSamRdr_5000 - - - - 10 - - - 5000 - - 689.6 - -
72.50 - 8,223,005 - 11,926,323
[java] SrchBitsNewRdr_500 - 10 500 152.5
32.80 14,360,618 16,962,356
[java] SrchMtchNewRdr_500 - - - - - 10 - - - 500 - - 171.3 - -
29.19 - 15,150,797 - 17,395,712
When the match searches preceded the bitset searches:
[java] Operation round runCnt recsPerRun rec/s
elapsedSec avgUsedMem avgTotalMem
[java] SrchMtchSamRdr_5000 - 10 5000 763.5
65.49 9,563,243 17,128,244
[java] SrchBitsSamRdr_5000 - - - - 10 - - - 5000 - - 729.3 - -
68.56 - 10,003,775 - 13,001,114
[java] SrchMtchNewRdr_500 - 10 500 175.7
28.46 12,068,559 17,524,326
[java] SrchBitsNewRdr_500 - - - - - 10 - - - 500 - - 183.7 - -
27.22 - 15,098,480 - 17,974,476
My conclusion from this is that the speed-up, if exists, is minor, at least for
the setup of this test.
There are only 15 unique queries in this test - also printed in the log - are
these the queries you would expect to save in?
I didn't follow this issue very closely so I don't know where the saving is
expected here. Both SearchTask and MatchTask now do nothing in collect, so no
difference at the actual collect() call.
Also, Scorer.score(HitCollector) and Matcher.match(MatchCollector) are very
similar:
public void score(HitCollector hc) throws IOException {
while (next()) {
hc.collect(doc(), score());
}
}
public void match(MatchCollector mc) throws IOException {
while (next()) {
mc.collect(doc());
}
}
Especially for the case that the collect() method is doing nothing, as in this
test.
I think there is a potential gain for large boolean OR queries, because score()
would have to call next() on all TermScorers and collect/sum their scores,
while match() could use skipTo(last+1) because any match encountered is a match
and there is no need to sum the individual scores for the same doc by other
scorers. However as far as I can tell, current match() implementation does not
take advantage of this, but I may be overlooking something?
> Decouple Filter from BitSet
> ---------------------------
>
> Key: LUCENE-584
> URL: https://issues.apache.org/jira/browse/LUCENE-584
> Project: Lucene - Java
> Issue Type: Improvement
> Components: Search
> Affects Versions: 2.0.1
> Reporter: Peter Schäfer
> Priority: Minor
> Attachments: bench-diff.txt, bench-diff.txt, BitsMatcher.java,
> Filter-20060628.patch, HitCollector-20060628.patch,
> IndexSearcher-20060628.patch, MatchCollector.java, Matcher.java,
> Matcher20070226.patch, Scorer-20060628.patch, Searchable-20060628.patch,
> Searcher-20060628.patch, Some Matchers.zip, SortedVIntList.java,
> TestSortedVIntList.java
>
>
> {code}
> package org.apache.lucene.search;
> public abstract class Filter implements java.io.Serializable
> {
> public abstract AbstractBitSet bits(IndexReader reader) throws IOException;
> }
> public interface AbstractBitSet
> {
> public boolean get(int index);
> }
> {code}
> It would be useful if the method =Filter.bits()= returned an abstract
> interface, instead of =java.util.BitSet=.
> Use case: there is a very large index, and, depending on the user's
> privileges, only a small portion of the index is actually visible.
> Sparsely populated =java.util.BitSet=s are not efficient and waste lots of
> memory. It would be desirable to have an alternative BitSet implementation
> with smaller memory footprint.
> Though it _is_ possibly to derive classes from =java.util.BitSet=, it was
> obviously not designed for that purpose.
> That's why I propose to use an interface instead. The default implementation
> could still delegate to =java.util.BitSet=.
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