[jira] [Commented] (HIVE-18410) [Performance][Avro] Reading flat Avro tables is very expensive in Hive

["Ratandeep Ratti (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HIVE-18410?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16317521#comment-16317521 ] 

Ratandeep Ratti commented on HIVE-18410:
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Attached profiling data

> [Performance][Avro] Reading flat Avro tables is very expensive in Hive
> ----------------------------------------------------------------------
>
>                 Key: HIVE-18410
>                 URL: https://issues.apache.org/jira/browse/HIVE-18410
>             Project: Hive
>          Issue Type: Improvement
>    Affects Versions: 2.3.2
>            Reporter: Ratandeep Ratti
>            Assignee: Ratandeep Ratti
>             Fix For: 2.3.2
>
>         Attachments: profiling_with_patch.nps, profiling_with_patch.png, profiling_without_patch.nps, profiling_without_patch.png
>
>
> There's a performance penalty when reading flat [no nested fields] Avro tables. When reading the same flat dataset in Pig, it takes half the time.  On profiling, a lot of time is spent in {{AvroDeserializer.deserializeSingleItemNullableUnion()}}. The bulk of the time is spent in GenericData.get().resolveUnion(), which calls GenericData.getSchemaName(Object datum), which does a lot of instanceof checks.  This could be simplified with performance benefits. A approach is described in this patch which almost halves the runtime.



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