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https://issues.apache.org/jira/browse/LUCENE-6697?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14648942#comment-14648942
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Michael McCandless commented on LUCENE-6697:
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bq. I also changed search-time to an iterative impl (vs recursive before)
Actually once nice benefit of this is it's easy to estimate up front how many
hits we'll have, so I can call {{grow}} up front. I'll add that and commit
soon...
> Use 1D KD tree for alternative to postings based numeric range filters
> ----------------------------------------------------------------------
>
> Key: LUCENE-6697
> URL: https://issues.apache.org/jira/browse/LUCENE-6697
> Project: Lucene - Core
> Issue Type: New Feature
> Reporter: Michael McCandless
> Assignee: Michael McCandless
> Attachments: LUCENE-6697.patch, LUCENE-6697.patch, LUCENE-6697.patch
>
>
> Today Lucene uses postings to index a numeric value at multiple
> precision levels for fast range searching. It's somewhat costly: each
> numeric value is indexed with multiple terms (4 terms by default)
> ... I think a dedicated 1D BKD tree should be more compact and perform
> better.
> It should also easily generalize beyond 64 bits to arbitrary byte[],
> e.g. for LUCENE-5596, but I haven't explored that here.
> A 1D BKD tree just sorts all values, and then indexes adjacent leaf
> blocks of size 512-1024 (by default) values per block, and their
> docIDs, into a fully balanced binary tree. Building the range filter
> is then just a recursive walk through this tree.
> It's the same structure we use for 2D lat/lon BKD tree, just with 1D
> instead. I implemented it as a DocValuesFormat that also writes the
> numeric tree on the side.
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