It's been pointed multiple times that a difference between Tantivy and Lucene
is the fact that Tantivy uses windows of 4,096 docs when Lucene has a 2x
smaller window size of 2,048 docs and that this might explain part of the
performance difference. luceneutil suggests that bumping the window size to
4,096 does indeed improve performance for counting queries, but not for top-k
queries. I'm still suggesting to bump the window size across the board to keep
our disjunction scorer consistent.
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