[jira] [Commented] (HIVE-21376) Incompatible change in Hive bucket computation

["Piotr Findeisen (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HIVE-21376?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16901291#comment-16901291 ] 

Piotr Findeisen commented on HIVE-21376:
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bq. If bucketed data with those types has been written in 3.0 using v2, a user should recreate those bucketed tables using a more recent Hive version.

To me that means Hive 3 should not be deployed on production until this issue is fixed.
It's fixed in 3.1.2, but the latest available from HDP is 3.1.0.

[~jcamachorodriguez] do you have a timeline when 3.1.2 will be available in HDP?


> 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
>             Fix For: 4.0.0, 3.2.0, 3.1.2
>
>         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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