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https://issues.apache.org/jira/browse/LUCENE-6890?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Michael McCandless updated LUCENE-6890:
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Attachment: LUCENE-6890.patch
Patch, that adds too much code complexity, is buggy (because the opto isn't
safe for the union-of-disjoint-parts), and too little query performance gains.
> Specialize 1D dimensional values intersection
> ---------------------------------------------
>
> Key: LUCENE-6890
> URL: https://issues.apache.org/jira/browse/LUCENE-6890
> Project: Lucene - Core
> Issue Type: Improvement
> Reporter: Michael McCandless
> Attachments: LUCENE-6890.patch
>
>
> I tried implementing the same specialization we had before LUCENE-6881 for
> the 1D case, but after testing it, I don't think it's worth it.
> I'll upload the patch here for posterity (tests pass), but net/net it adds
> non-trivial code complexity in exchange for minor (5.39 sec -> 5.25 sec for
> 225 queries) query gains. Maybe in the future someone could improve this so
> it's more compelling... but I don't think the tradeoff is worth it today.
> Furthermore, the optimization 1) requires an API change, and 2) is not even
> admissible in the current patch, since the query could be a union of multiple
> disjoint ranges when the optimization assumes it's just a single range.
> The gist of the idea is to locate the start leaf block and end leaf block,
> make an informed estimate of the expected result set size, and then do a
> linear scan of the leaf blocks, vs the recursion and "grow per leaf block" we
> do today. I think the conclusion is that this used to be more sizable win,
> but {{DocIdSetBuilder}} has improved so that it is plenty fast without
> "upfront" growing, which is nice :)
> Or maybe my benchmark is bogus ;)
> I'll commit the minor code comment / TODOs / test improvements from the patch
> ...
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