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https://issues.apache.org/jira/browse/LUCENE-5122?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13713670#comment-13713670
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Adrien Grand commented on LUCENE-5122:
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For SortingMP, we only provide the ability to sort by a NumericDocValues field
out of the box because numbers feel more natural to define a static rank.
Maybe another case where BlockPackedReader could help is if almost all
documents have the same value. In that case BlockPackedReader will be able to
require 0 bits per value for all blocks that contain a single unique value.
But I agree PackedInts would likely better in general and remove one level of
indirection.
> DiskDV probably shouldnt use BlockPackedReader for SortedDV doc-to-ord
> ----------------------------------------------------------------------
>
> Key: LUCENE-5122
> URL: https://issues.apache.org/jira/browse/LUCENE-5122
> Project: Lucene - Core
> Issue Type: Improvement
> Reporter: Robert Muir
>
> I dont think "blocking" provides any benefit here in general. we can assume
> the ordinals are essentially random and since SortedDV is single-valued, its
> probably better to just use the simpler packedints directly?
> I guess the only case where it would help is if you sorted your segments by
> that DV field. But that seems kinda wierd/esoteric to sort your index by a
> deref'ed string value, e.g. I don't think its even supported by SortingMP.
> For the SortedSet "ord stream", this can exceed 2B values so for now I think
> it should stay as blockpackedreader. but it could use a large blocksize...
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