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Posted to dev@lucene.apache.org by "Adrien Grand (JIRA)" <ji...@apache.org> on 2016/07/06 13:22:10 UTC
[jira] [Updated] (LUCENE-7371) BKDReader could compress values
better
[ https://issues.apache.org/jira/browse/LUCENE-7371?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Adrien Grand updated LUCENE-7371:
---------------------------------
Attachment: LUCENE-7371.patch
Here is a patch. On the IndexAndSearchOpenStreetMaps benchmark, it saves 9.7% storage (577MB -> 521B). The "distance" and "poly 5" benchmarks report the same response times but the "box" benchmark is about 4% slower.
> BKDReader could compress values better
> --------------------------------------
>
> Key: LUCENE-7371
> URL: https://issues.apache.org/jira/browse/LUCENE-7371
> Project: Lucene - Core
> Issue Type: Bug
> Reporter: Adrien Grand
> Assignee: Adrien Grand
> Priority: Minor
> Attachments: LUCENE-7371.patch
>
>
> For compressing values, BKDReader only relies on shared prefixes in a block. We could probably easily do better. For instance there are only 256 possible values for the first byte of the dimension that the values are sorted by, yet we use a block size of 1024. So by using something simple like run-length compression we could save 6 bits per value on average.
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