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https://issues.apache.org/jira/browse/LUCENE-4396?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13970091#comment-13970091
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Michael McCandless commented on LUCENE-4396:
--------------------------------------------
This looks great! Tests pass for me.
Changing from static so you can access requiredNrMatchers seems fine;
we could also pass that into the class & save it. Either way ...
The comment for REQUIRED_MASK needs fixing.
Maybe add a comment where we return null if requiredSubScorer is null
explaining why?
Hmm that pre-existing comment "// Check if we can and should return a
BooleanScorer" is wrong ... I'll fix.
Small styling issue: we don't put whitespace after ( and before ),
e.g.:
{noformat}
if ( this.requiredNrMatchers > 0 ) {
{noformat}
should be this instead:
{noformat}
if (this.requiredNrMatchers > 0) {
{noformat}
Maybe change:
{noformat}
if (current.coord >= minNrShouldMatch + requiredNrMatchers) {
{noformat}
to:
{noformat}
if (current.coord - requiredNrMatchers >= minNrShouldMatch) {
{noformat}
And add a comment saying "minNrShouldMatch only applies to SHOULD
clauses", or something? Just to make the math more obvious :)
bq. For consistency, I should probably change the argument from "List<Scorer>
requiredScorers" to "List<BulkScorer> requiredScorers", but, as a result,
getScorer method should be added to BulkScorer.
Hmm in general a BulkScorer need not implement a Scorer under the hood
(DefaultBulkScorer does, because it wraps, but e.g. BooleanScorer
doesn't).
Or alternatively if you pass List<BulkScorer> you could handle all the
conjunctions yourself in BooleanScorer, e.g. make different collectors
for them that add up a "mustClauseCountMatches" counter (instead of
setting the 1 bit mask), and then check if that counts is >=
requiredScorers.size() before counting it as a hit...
> BooleanScorer should sometimes be used for MUST clauses
> -------------------------------------------------------
>
> Key: LUCENE-4396
> URL: https://issues.apache.org/jira/browse/LUCENE-4396
> Project: Lucene - Core
> Issue Type: Improvement
> Reporter: Michael McCandless
> Attachments: LUCENE-4396.patch
>
>
> Today we only use BooleanScorer if the query consists of SHOULD and MUST_NOT.
> If there is one or more MUST clauses we always use BooleanScorer2.
> But I suspect that unless the MUST clauses have very low hit count compared
> to the other clauses, that BooleanScorer would perform better than
> BooleanScorer2. BooleanScorer still has some vestiges from when it used to
> handle MUST so it shouldn't be hard to bring back this capability ... I think
> the challenging part might be the heuristics on when to use which (likely we
> would have to use firstDocID as proxy for total hit count).
> Likely we should also have BooleanScorer sometimes use .advance() on the subs
> in this case, eg if suddenly the MUST clause skips 1000000 docs then you want
> to .advance() all the SHOULD clauses.
> I won't have near term time to work on this so feel free to take it if you
> are inspired!
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