[jira] [Commented] (LUCENE-9899) Numeric DV block compression ignores the gcd when computing the number of bits required

["Adrien Grand (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/LUCENE-9899?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17313041#comment-17313041 ] 

Adrien Grand commented on LUCENE-9899:
--------------------------------------

We have a test for GCD compression in {{BaseCompressingDocValuesFormatTestCase#testDateCompression}}, I wonder if we can have a similar test for block+GCD compression. Otherwise +1 to the patch, great catch!

> Numeric DV block compression ignores the gcd when computing the number of bits required
> ---------------------------------------------------------------------------------------
>
>                 Key: LUCENE-9899
>                 URL: https://issues.apache.org/jira/browse/LUCENE-9899
>             Project: Lucene - Core
>          Issue Type: New Feature
>            Reporter: Jim Ferenczi
>            Priority: Major
>         Attachments: LUCENE-9899.patch
>
>
> When numeric doc values are splitted per block we compute the number of bits per value [from the minimum and maximum value present in the block|https://github.com/apache/lucene/blob/d5d6dc079395c47cd6d12dcce3bcfdd2c7d9dc63/lucene/core/src/java/org/apache/lucene/codecs/lucene90/Lucene90DocValuesConsumer.java#L390]. However, the greatest common divisor is not taken into account so the number is overvalued for cases where it is greater than 1.
>  



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