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https://issues.apache.org/jira/browse/LUCENE-6901?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Michael McCandless resolved LUCENE-6901.
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Resolution: Fixed
> Optimize 1D dimensional value indexing
> --------------------------------------
>
> Key: LUCENE-6901
> URL: https://issues.apache.org/jira/browse/LUCENE-6901
> Project: Lucene - Core
> Issue Type: Improvement
> Reporter: Michael McCandless
> Assignee: Michael McCandless
> Fix For: Trunk
>
> Attachments: LUCENE-6901-timsort.patch, LUCENE-6901.patch,
> LUCENE-6901.patch
>
>
> Dimensional values give a smaller index, and faster search times, for
> indexing ordered byte[] values across one or more dimensions, vs our existing
> approaches, but the indexing time is substantially slower.
> Since the 1D case is so important/common (numeric fields, range query) I
> think it's worth optimizing its indexing time. It should also be possible to
> optimize the N > 1 dimensions case too, but it's more complex ... we can
> postpone that.
> So for the 1D case, I changed the merge method to do a merge sort (like
> postings) of the already sorted segments dimensional values, instead of
> simply re-indexing all values from the incoming segments, and this was a big
> speedup.
> I also changed from {{InPlaceMergeSorter}} to {{IntroSorter}} (this is what
> postings use, and it's faster but still safe) and this was another good
> speedup, which should also help the > 1D cases.
> Finally, I added a {{BKDReader.verify}} method (currently it's dark: NOT
> called) that walks the index and then check that every value in each leaf
> block does in fact fall within what the index expected/claimed. This is
> useful for finding bugs! Maybe we can cleanly fold it into {{CheckIndex}}
> somehow later.
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