Github user shebiki commented on the pull request:
https://github.com/apache/lucene-solr/pull/40#issuecomment-38165595
Mikhail,
I have a similar use case and opted for creating the `BooleanScorer2`
directly instead of trying to associate each child `Scorer` with the drilldown
id. I chose not to use the
[QueryWrapper](https://github.com/apache/lucene-solr/blob/lucene_solr_4_6/lucene/facet/src/java/org/apache/lucene/facet/search/DrillSideways.java#L352)
pattern from `DrillSideways` in 4.6.0 because I felt it would prevent future
optimizations and it was no longer in use in 4.7. I didn't consider the idea of
just comparing `scorer.getWeight().getQuery()` but it's essentially the same
work flow.
The reason that I felt that prevented further optimization is that it
prevents a `Weight` instance from returning an already created child `Scorer`.
For example:
* A `BooleanQuery` consisting of just `SHOULD` clauses with `disableCoord`
set to `true`. If a segment only has one non-null scorer then
`BooleanWeight.scorer()` should be able to return just that child scorer
instead of having to wrap it with another.
* Introduction of a extra scoring metadata (imagine decorating each score
with an additional `boolean`). In this case a composing query (variant of
`BooleanQuery`, ``DisjunctionMaxQuery`, etc) would want to aggregated this
extra metadata at scoring time. If the metadata has a decent default value then
only some of the child `Scorer`s will be able to provide it. If non of the
child `Scorer`s provide this metadata then it's calculation can probably be
short circuited and it can just return a `BooleanScorer`, `ConjunctionScorer`,
or `DisjunctionScorer` as needed. This would be more efficient than making it
wrap unconditionally.
Quick question about your particular drillsideways query. Do you call
`score()`, `freq()`, or something else to ensure the `SHOULD` `Scorer`s are
correctly positioned? Do you optimize for when `BooleanQuery` returns a
`DisjunctionScorer` and the child `Scorer`s are already positioned?
--Terry
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