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https://issues.apache.org/jira/browse/HIVE-21376?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16787245#comment-16787245
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Ashutosh Chauhan commented on HIVE-21376:
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+1
> Incompatible change in Hive bucket computation
> ----------------------------------------------
>
> Key: HIVE-21376
> URL: https://issues.apache.org/jira/browse/HIVE-21376
> Project: Hive
> Issue Type: Bug
> Affects Versions: 3.1.0
> Reporter: David Phillips
> Assignee: Jesus Camacho Rodriguez
> Priority: Major
> Attachments: HIVE-21376.01.patch, HIVE-21376.patch
>
>
> HIVE-20007 seems to have inadvertently changed the bucket hash code
> computation via {{ObjectInspectorUtils.getBucketHashCodeOld()}} for the
> {{DATE}} and {{TIMESTAMP}} data type2.
> {{DATE}} was previously computed using {{DateWritable}}, which uses
> {{daysSinceEpoch}} as the hash code. It is now computed using
> {{DateWritableV2}}, which uses the hash code of {{java.time.LocalDate}}
> (which is not days since epoch).
> {{TIMESTAMP}} was previous computed using {{TimestampWritable}} and now uses
> {{TimestampWritableV2}}. They ostensibly use the same hash code computation,
> but there are two important differences:
> # {{TimestampWritable}} rounds the number of milliseconds into the seconds
> portion of the computation, but {{TimestampWritableV2}} does not.
> # {{TimestampWritable}} gets the epoch time from {{java.sql.Timestamp}},
> which returns it relative to the JVM time zone, not UTC.
> {{TimestampWritableV2}} uses a {{LocalDateTime}} relative to UTC.
> I was unable to get Hive 3.1 running in order to verify if this actually
> causes data to be read or written incorrectly (there may be code above this
> library method which makes things work correctly). However, if my
> understanding is correct, this means Hive 3.1 is both forwards and backwards
> incompatible with bucketed tables using either of these data types. It also
> indicates that Hive needs tests to verify that the hash code does not change
> between releases.
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