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Posted to issues@lucene.apache.org by "ASF subversion and git services (Jira)" <ji...@apache.org> on 2020/11/02 15:41:00 UTC
[jira] [Commented] (LUCENE-9536) Optimize OrdinalMap when one
segment contains all distinct values?
[ https://issues.apache.org/jira/browse/LUCENE-9536?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17224744#comment-17224744 ]
ASF subversion and git services commented on LUCENE-9536:
---------------------------------------------------------
Commit 8f004f7a38947176eecf9056087311f39d7504d6 in lucene-solr's branch refs/heads/master from Julie Tibshirani
[ https://gitbox.apache.org/repos/asf?p=lucene-solr.git;h=8f004f7 ]
LUCENE-9536: Optimize OrdinalMap when one segment contains all distinct values. (#1948)
LUCENE-9536: Optimize OrdinalMap when one segment contains all distinct values.
For doc values that are not too high cardinality, it is common for some large
segments to contain all distinct values. In this case, we can check if the first
segment ords map perfectly to global ords, and if so store the global ord deltas
and first segment indices as `LongValues.ZEROES`
to save some space.
> Optimize OrdinalMap when one segment contains all distinct values?
> ------------------------------------------------------------------
>
> Key: LUCENE-9536
> URL: https://issues.apache.org/jira/browse/LUCENE-9536
> Project: Lucene - Core
> Issue Type: Improvement
> Reporter: Julie Tibshirani
> Priority: Minor
> Time Spent: 3h
> Remaining Estimate: 0h
>
> For doc values that are not too high cardinality, it seems common to have some large segments that contain all distinct values (plus many small segments who are missing some values). In this case, we could check if the first segment ords map perfectly to global ords and if so store `globalOrdDeltas` and `firstSegments` as `LongValues.ZEROES`. This could save a small amount of space.
> I don’t think it would help a huge amount, especially since the optimization might only kick in with small/ medium cardinalities, which don’t create huge `OrdinalMap` instances anyways? But it is simple and seemed worth mentioning.
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