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https://issues.apache.org/jira/browse/LUCENE-6668?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Adrien Grand updated LUCENE-6668:
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Attachment: LUCENE-6668.patch
Here is a patch: it uses table encoding for SortedSet/SortedNumeric if the sum
of the sizes of all unique sets is 256 or less. If my math is correct, this
means it will always be used if there are 6 unique values or less (given that
the sum of the sizes of all possible subsets would be 192), and might be used
if the number of unique values is between 7 and 256.
> Optimize SortedSet/SortedNumeric storage for the few unique sets use-case
> -------------------------------------------------------------------------
>
> Key: LUCENE-6668
> URL: https://issues.apache.org/jira/browse/LUCENE-6668
> Project: Lucene - Core
> Issue Type: Improvement
> Reporter: Adrien Grand
> Assignee: Adrien Grand
> Priority: Minor
> Attachments: LUCENE-6668.patch
>
>
> Robert suggested this idea: if there are few unique sets of values, we could
> build a lookup table and then map each doc to an ord in this table, just like
> we already do for table compression for numerics.
> I think this is especially compelling given that SortedSet/SortedNumeric are
> our two only doc values types that use O(maxDoc) memory because of the
> offsets map. When this new strategy is used, memory usage could be bounded to
> a constant.
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