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https://issues.apache.org/jira/browse/LUCENE-6919?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15048947#comment-15048947
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Adrien Grand commented on LUCENE-6919:
--------------------------------------
Woops, here is the actual patch I wanted to upload.
> Change the Scorer API to expose an iterator instead of extending
> DocIdSetIterator
> ---------------------------------------------------------------------------------
>
> Key: LUCENE-6919
> URL: https://issues.apache.org/jira/browse/LUCENE-6919
> Project: Lucene - Core
> Issue Type: Improvement
> Reporter: Adrien Grand
> Assignee: Adrien Grand
> Priority: Minor
> Attachments: LUCENE-6919.patch, LUCENE-6919.patch, LUCENE-6919.patch
>
>
> I was working on trying to address the performance regression on LUCENE-6815
> but this is hard to do without introducing specialization of
> DisjunctionScorer which I'd like to avoid at all costs.
> I think the performance regression would be easy to address without
> specialization if Scorers were changed to return an iterator instead of
> extending DocIdSetIterator. So conceptually the API would move from
> {code}
> class Scorer extends DocIdSetIterator {
> }
> {code}
> to
> {code}
> class Scorer {
> DocIdSetIterator iterator();
> }
> {code}
> This would help me because then if none of the sub clauses support two-phase
> iteration, DisjunctionScorer could directly return the approximation as an
> iterator instead of having to check if twoPhase == null at every iteration.
> Such an approach could also help remove some method calls. For instance
> TermScorer.nextDoc calls PostingsEnum.nextDoc but with this change
> TermScorer.iterator() could return the PostingsEnum and TermScorer would not
> even appear in stack traces when scoring. I hacked a patch to see how much
> that would help and luceneutil seems to like the change:
> {noformat}
> TaskQPS baseline StdDev QPS patch StdDev
> Pct diff
> Fuzzy1 88.54 (15.7%) 86.73 (16.6%)
> -2.0% ( -29% - 35%)
> AndHighLow 698.98 (4.1%) 691.11 (5.1%)
> -1.1% ( -9% - 8%)
> Fuzzy2 26.47 (11.2%) 26.28 (10.3%)
> -0.7% ( -19% - 23%)
> MedSpanNear 141.03 (3.3%) 140.51 (3.2%)
> -0.4% ( -6% - 6%)
> HighPhrase 60.66 (2.6%) 60.48 (3.3%)
> -0.3% ( -5% - 5%)
> LowSpanNear 29.25 (2.4%) 29.21 (2.1%)
> -0.1% ( -4% - 4%)
> MedPhrase 28.32 (1.9%) 28.28 (2.0%)
> -0.1% ( -3% - 3%)
> LowPhrase 17.31 (2.1%) 17.29 (2.6%)
> -0.1% ( -4% - 4%)
> HighSloppyPhrase 10.93 (6.0%) 10.92 (6.0%)
> -0.1% ( -11% - 12%)
> MedSloppyPhrase 72.21 (2.2%) 72.27 (1.8%)
> 0.1% ( -3% - 4%)
> Respell 57.35 (3.2%) 57.41 (3.4%)
> 0.1% ( -6% - 6%)
> HighSpanNear 26.71 (3.0%) 26.75 (2.5%)
> 0.1% ( -5% - 5%)
> OrNotHighLow 803.46 (3.4%) 807.03 (4.2%)
> 0.4% ( -6% - 8%)
> LowSloppyPhrase 88.02 (3.4%) 88.77 (2.5%)
> 0.8% ( -4% - 7%)
> OrNotHighMed 200.45 (2.7%) 203.83 (2.5%)
> 1.7% ( -3% - 7%)
> OrHighHigh 38.98 (7.9%) 40.30 (6.6%)
> 3.4% ( -10% - 19%)
> HighTerm 92.53 (5.3%) 95.94 (5.8%)
> 3.7% ( -7% - 15%)
> OrHighMed 53.80 (7.7%) 55.79 (6.6%)
> 3.7% ( -9% - 19%)
> AndHighMed 266.69 (1.7%) 277.15 (2.5%)
> 3.9% ( 0% - 8%)
> Prefix3 44.68 (5.4%) 46.60 (7.0%)
> 4.3% ( -7% - 17%)
> MedTerm 261.52 (4.9%) 273.52 (5.4%)
> 4.6% ( -5% - 15%)
> Wildcard 42.39 (6.1%) 44.35 (7.8%)
> 4.6% ( -8% - 19%)
> IntNRQ 10.46 (7.0%) 10.99 (9.5%)
> 5.0% ( -10% - 23%)
> OrNotHighHigh 67.15 (4.6%) 70.65 (4.5%)
> 5.2% ( -3% - 15%)
> OrHighNotHigh 43.07 (5.1%) 45.36 (5.4%)
> 5.3% ( -4% - 16%)
> OrHighLow 64.19 (6.4%) 67.72 (5.5%)
> 5.5% ( -6% - 18%)
> AndHighHigh 64.17 (2.3%) 67.87 (2.1%)
> 5.8% ( 1% - 10%)
> LowTerm 642.94 (10.9%) 681.48 (8.5%)
> 6.0% ( -12% - 28%)
> OrHighNotMed 12.68 (6.9%) 13.51 (6.6%)
> 6.5% ( -6% - 21%)
> OrHighNotLow 54.69 (6.8%) 58.25 (7.0%)
> 6.5% ( -6% - 21%)
> {noformat}
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