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https://issues.apache.org/jira/browse/LUCENE-6863?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14979524#comment-14979524
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Robert Muir commented on LUCENE-6863:
-------------------------------------
{quote}
Here is a patch. It detects sparsity by checking if less than 10% documents
have a value.
{quote}
Please, put a minimum count like 1024 where this starts to make sense, so types
arent flipping back and forth during ordinary NRT search. And where did 10%
come from? It seems far too aggressive. In previous work we determined much
lower thresholds to work better (e.g. 3%).
> Store sparse doc values more efficiently
> ----------------------------------------
>
> Key: LUCENE-6863
> URL: https://issues.apache.org/jira/browse/LUCENE-6863
> Project: Lucene - Core
> Issue Type: Improvement
> Reporter: Adrien Grand
> Assignee: Adrien Grand
> Attachments: LUCENE-6863.patch
>
>
> For both NUMERIC fields and ordinals of SORTED fields, we store data in a
> dense way. As a consequence, if you have only 1000 documents out of 1B that
> have a value, and 8 bits are required to store those 1000 numbers, we will
> not require 1KB of storage, but 1GB.
> I suspect this mostly happens in abuse cases, but still it's a pity that we
> explode storage requirements. We could try to detect sparsity and compress
> accordingly.
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