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