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https://issues.apache.org/jira/browse/LUCENE-7462?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Adrien Grand updated LUCENE-7462:
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Attachment: LUCENE-7462-advanceExact.patch
I have been playing with the idea of having an advanceExact method (which I
guess is the alternative to adding a 2nd search API for doc values). It removes
stress on consumers since this method can be called blindly since it does not
advance beyond the target document. It also removes some stress on the codec
since it doesn't have to find the next document that has a value anymore.
I ran the wikimedium10m benchmark, to which I added the sorting tasks from the
nigthly benchmark to check the impact. There seems to be a consistent speedup
for queries for which norms is the bottleneck (term queries and simple
conjunctions/disjunctions) and sorted queries (TermTitleSort and TermDTSort).
{noformat}
TaskQPS baseline StdDev QPS patch StdDev
Pct diff
Fuzzy2 55.31 (20.1%) 54.45 (18.5%)
-1.6% ( -33% - 46%)
OrNotHighLow 875.16 (3.3%) 870.60 (2.9%)
-0.5% ( -6% - 5%)
MedSloppyPhrase 210.38 (3.9%) 209.40 (3.8%)
-0.5% ( -7% - 7%)
LowSloppyPhrase 126.86 (2.5%) 126.74 (2.1%)
-0.1% ( -4% - 4%)
AndHighMed 151.22 (1.7%) 151.30 (2.3%)
0.0% ( -3% - 4%)
LowSpanNear 20.08 (2.6%) 20.10 (2.9%)
0.1% ( -5% - 5%)
Respell 77.27 (3.8%) 77.36 (3.5%)
0.1% ( -6% - 7%)
LowPhrase 42.32 (2.1%) 42.40 (1.9%)
0.2% ( -3% - 4%)
HighPhrase 20.01 (4.1%) 20.06 (3.7%)
0.3% ( -7% - 8%)
Wildcard 46.20 (3.5%) 46.32 (3.9%)
0.3% ( -6% - 7%)
HighSloppyPhrase 15.99 (5.1%) 16.04 (4.9%)
0.3% ( -9% - 10%)
Prefix3 43.21 (2.9%) 43.39 (3.1%)
0.4% ( -5% - 6%)
MedPhrase 151.07 (3.4%) 151.69 (3.7%)
0.4% ( -6% - 7%)
OrNotHighMed 151.21 (2.3%) 151.98 (2.6%)
0.5% ( -4% - 5%)
AndHighHigh 58.73 (1.4%) 59.05 (1.4%)
0.5% ( -2% - 3%)
MedSpanNear 22.36 (1.6%) 22.48 (1.6%)
0.6% ( -2% - 3%)
IntNRQ 13.75 (12.5%) 13.83 (13.1%)
0.6% ( -22% - 29%)
OrHighNotMed 62.26 (2.7%) 62.70 (3.2%)
0.7% ( -5% - 6%)
OrNotHighHigh 58.38 (2.6%) 58.82 (2.4%)
0.7% ( -4% - 5%)
HighSpanNear 39.78 (2.2%) 40.09 (3.0%)
0.8% ( -4% - 6%)
OrHighNotHigh 44.88 (2.8%) 45.29 (2.7%)
0.9% ( -4% - 6%)
AndHighLow 694.25 (4.8%) 703.66 (3.8%)
1.4% ( -6% - 10%)
OrHighLow 91.20 (3.4%) 92.54 (3.7%)
1.5% ( -5% - 8%)
OrHighNotLow 105.90 (3.0%) 107.79 (4.4%)
1.8% ( -5% - 9%)
Fuzzy1 79.92 (12.3%) 81.61 (12.1%)
2.1% ( -19% - 30%)
OrHighHigh 29.18 (7.2%) 29.83 (7.3%)
2.2% ( -11% - 18%)
OrHighMed 19.44 (7.2%) 19.89 (7.3%)
2.3% ( -11% - 18%)
TermTitleSort 81.70 (5.6%) 83.67 (5.8%)
2.4% ( -8% - 14%)
LowTerm 682.24 (4.5%) 704.58 (4.1%)
3.3% ( -5% - 12%)
TermDTSort 103.25 (5.7%) 106.77 (4.0%)
3.4% ( -5% - 13%)
MedTerm 249.00 (2.5%) 260.56 (3.2%)
4.6% ( -1% - 10%)
HighTerm 103.70 (3.2%) 109.27 (3.6%)
5.4% ( -1% - 12%)
{noformat}
Note that the patch has barely any tests, so it's really just for playing. :)
We'd also still need to define the semantics of this method.
> Faster search APIs for doc values
> ---------------------------------
>
> Key: LUCENE-7462
> URL: https://issues.apache.org/jira/browse/LUCENE-7462
> Project: Lucene - Core
> Issue Type: Improvement
> Affects Versions: master (7.0)
> Reporter: Adrien Grand
> Priority: Minor
> Attachments: LUCENE-7462-advanceExact.patch
>
>
> While the iterator API helps deal with sparse doc values more efficiently, it
> also makes search-time operations more costly. For instance, the old
> random-access API allowed to compute facets on a given segment without any
> conditionals, by just incrementing the counter at index {{ordinal+1}} while
> the new API requires to advance the iterator if necessary and then check
> whether it is exactly on the right document or not.
> Since it is very common for fields to exist across most documents, I suspect
> codecs will keep an internal structure that is similar to the current codec
> in the dense case, by having a dense representation of the data and just
> making the iterator skip over the minority of documents that do not have a
> value.
> I suggest that we add APIs that make things cheaper at search time. For
> instance in the case of SORTED doc values, it could look like
> {{LegacySortedDocValues}} with the additional restriction that documents can
> only be consumed in order. Codecs that can implement this API efficiently
> would hide it behind a {{SortedDocValues}} adapter, and then at search time
> facets and comparators (which liked the {{LegacySortedDocValues}} API better)
> would either unwrap or hide the SortedDocValues they got behind a more
> random-access API (which would only happen in the truly sparse case if the
> codec optimizes the dense case).
> One challenge is that we already use the same idea for hiding single-valued
> impls behind multi-valued impls, so we would need to enforce the order in
> which the wrapping needs to happen. At first sight, it seems that it would be
> best to do the single-value-behind-multi-value-API wrapping above the
> random-access-behind-iterator-API wrapping. The complexity of
> wrapping/unwrapping in the right order could be contained in the
> {{DocValues}} helper class.
> I think this change would also simplify search-time consumption of doc
> values, which currently needs to spend several lines of code positioning the
> iterator everytime it needs to do something interesting with doc values.
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