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https://issues.apache.org/jira/browse/LUCENE-8135?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16336062#comment-16336062
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Adrien Grand commented on LUCENE-8135:
--------------------------------------
Here is a patch that applies on top of the one that is posted on LUCENE-4198:
- Scorer gets the same methods as ImpactsEnum: advanceShallow and getMaxScore,
with the same contract
- Disjunctions and conjunctions skip over entire blocks when the sum of max
scores is not competitive.
- Disjunctions now use the block max score instead of the global max score,
which helps skip over more documents.
- This is not documented in the paper, but when a minimum score is set, the
score is computed on the fly in order to move to the next doc faster. I did
this based on the observation that computing a score was often less costly than
advancing another clause. This is especially useful due to the fact that on the
contrary to term queries, the maximum score of a block is often not collected.
- Another difference with the paper is the fact that we have information about
blocks at multiple levels. This is one of the ideas described in a follow-up
paper (see section 4 of http://engineering.nyu.edu/~suel/papers/bmm.pdf) which
is based on the observation that you sometimes want to advance by more than
${block-size}.
Results on wikibigall need to be taken carefully as some tasks are either
faster or slower depending on which query is run. Typically queries whose terms
match lots of documents but the intersection matches few documents are a bit
slower because it takes time to get a good lower bound for the score. Baseline
is master, and patch is the combination of the patch on LUCENE-4198 and this
patch.
{noformat}
TaskQPS baseline StdDev QPS patch StdDev
Pct diff
OrHighLow 439.34 (2.2%) 402.38 (1.8%)
-8.4% ( -12% - -4%)
Fuzzy1 144.25 (4.3%) 137.08 (3.3%)
-5.0% ( -12% - 2%)
MedPhrase 66.49 (1.1%) 63.83 (1.8%)
-4.0% ( -6% - -1%)
Fuzzy2 153.94 (7.0%) 147.95 (7.3%)
-3.9% ( -16% - 11%)
HighTermDayOfYearSort 54.35 (10.5%) 52.97 (12.0%)
-2.5% ( -22% - 22%)
HighTermMonthSort 91.01 (9.0%) 89.31 (9.2%)
-1.9% ( -18% - 17%)
Prefix3 112.97 (7.6%) 111.66 (6.6%)
-1.2% ( -14% - 14%)
MedSpanNear 46.12 (4.1%) 45.82 (4.5%)
-0.6% ( -8% - 8%)
Respell 249.65 (4.4%) 248.13 (4.1%)
-0.6% ( -8% - 8%)
Wildcard 38.32 (6.9%) 38.09 (7.2%)
-0.6% ( -13% - 14%)
IntNRQ 34.26 (4.8%) 34.18 (6.0%)
-0.3% ( -10% - 11%)
LowSpanNear 12.46 (4.8%) 12.44 (4.9%)
-0.2% ( -9% - 10%)
LowPhrase 44.89 (1.4%) 44.85 (2.1%)
-0.1% ( -3% - 3%)
MedSloppyPhrase 13.77 (6.6%) 13.88 (5.8%)
0.8% ( -10% - 14%)
HighSpanNear 3.58 (7.0%) 3.61 (7.2%)
0.9% ( -12% - 16%)
LowSloppyPhrase 4.59 (7.7%) 4.65 (6.8%)
1.4% ( -12% - 17%)
HighSloppyPhrase 8.87 (8.1%) 9.02 (6.9%)
1.7% ( -12% - 18%)
AndHighLow 1380.92 (3.2%) 1418.90 (3.2%)
2.8% ( -3% - 9%)
HighPhrase 17.20 (3.3%) 18.70 (4.7%)
8.8% ( 0% - 17%)
OrHighHigh 21.38 (3.3%) 28.96 (4.6%)
35.5% ( 26% - 44%)
AndHighMed 123.15 (1.5%) 177.55 (5.3%)
44.2% ( 36% - 51%)
OrHighMed 42.31 (2.0%) 68.99 (4.0%)
63.0% ( 55% - 70%)
AndHighHigh 25.65 (1.5%) 44.33 (6.9%)
72.8% ( 63% - 82%)
LowTerm 567.65 (2.2%) 2305.80 (16.4%)
306.2% ( 281% - 332%)
MedTerm 284.07 (2.1%) 1837.41 (26.1%)
546.8% ( 508% - 587%)
AndCommon 56.30 (1.3%) 437.69 (33.5%)
677.5% ( 634% - 721%)
HighTerm 86.50 (2.1%) 709.65 (38.8%)
720.4% ( 665% - 777%)
OrCommon 13.95 (3.3%) 223.83 (66.0%)
1504.7% (1389% - 1627%)
{noformat}
For instance I had other runs that made OrHighMed slower. However the slowdown
is usually contained and remains in the ~10%.
There are two tasks that I added: AndCommon and OrCommon. Current tasks have
been computed rather randomly (I think!) based on the frequencies of terms, but
user queries are a bit more likely to query terms that frequently occur
together, so I wanted to see the impact on such queries:
{noformat}
OrCommon: united states
OrCommon: have been
OrCommon: see also
OrCommon: united kingdom
OrCommon: new york
AndCommon: +united +states
AndCommon: +have +been
AndCommon: +see +also
AndCommon: +united +kingdom
AndCommon: +new +york
{noformat}
On the contrary to some other tasks like OrHighMed, OrHighLow and AndHighLow,
those tasks are consistently MUCH faster with the patch.
> Implement Block-Max WAND
> ------------------------
>
> Key: LUCENE-8135
> URL: https://issues.apache.org/jira/browse/LUCENE-8135
> Project: Lucene - Core
> Issue Type: Improvement
> Reporter: Adrien Grand
> Priority: Minor
>
> This issue is about building on top of LUCENE-4198 in order to leverage block
> maximum scores instead of global maximum scores. This is documented in
> "Faster Top-k Document Retrieval Using Block-Max Indexes"
> ([http://engineering.nyu.edu/~suel/papers/bmw.pdf)|http://engineering.nyu.edu/~suel/papers/bmw.pdf]
> and called BMW (Block-Max WAND).
>
> Using block max scores adds overhead to scorers, but also provides better
> upper bounds of the scores and is expected to remain efficient in presence of
> outliers (LUCENE-8087).
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