Ignacio Vera created LUCENE-8673:
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Summary: Use radix sorting when merging dimensional points
Key: LUCENE-8673
URL: https://issues.apache.org/jira/browse/LUCENE-8673
Project: Lucene - Core
Issue Type: Improvement
Reporter: Ignacio Vera
Attachments: Geo3D.png, LatLonPoint.png, LatLonShape.png
Following the advise of [~jpountz] in LUCENE-8623I have investigated using
radix selection when merging segments instead of sorting the data at the
beginning. The results are pretty promising when running Lucene geo benchmarks:
{code:java}
||Approach||Index time (sec)||Force merge time (sec)||Index size (GB)||Reader
heap (MB)||
||Dev||Base||Diff ||Dev ||Base ||diff
||Dev||Base||Diff||Dev||Base||Diff ||
|points|241.5s|235.0s| 3%|157.2s|157.9s|-0%|0.55|0.55| 0%|1.57|1.57| 0%|
|shapes|416.1s|650.1s|-36%|306.1s|603.2s|-49%|1.29|1.29| 0%|1.61|1.61| 0%|
|geo3d|261.0s|360.1s|-28%|170.2s|279.9s|-39%|0.75|0.75| 0%|1.58|1.58| 0%|{code}
In 2D the index throughput is more or less equal but for higher dimensions the
impact is quite big. In all cases the merging process requires much less disk
space, I am attaching plots showing the different behaviour and I am opening a
pull request.
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