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https://issues.apache.org/jira/browse/HIVE-22941?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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László Bodor reassigned HIVE-22941:
-----------------------------------
Assignee: László Bodor
> Empty files are inserted into external tables after HIVE-21714
> --------------------------------------------------------------
>
> Key: HIVE-22941
> URL: https://issues.apache.org/jira/browse/HIVE-22941
> Project: Hive
> Issue Type: Improvement
> Reporter: László Bodor
> Assignee: László Bodor
> Priority: Major
> Attachments: HIVE-22941.01.patch
>
>
> There were multiple patches targeting an issue when INSERT OVERWRITE was
> ineffective if the input is empty:
> HIVE-18702: INSERT OVERWRITE TABLE doesn't clean the table directory before
> overwriting
> HIVE-21714: Insert overwrite on an acid/mm table is ineffective if the input
> is empty
> HIVE-21784: Insert overwrite on an acid (not mm) table is ineffective if the
> input is empty
> From these patches, HIVE-21714 seems to have a bad effect on external tables,
> because of this part:
> https://github.com/apache/hive/commit/9a10bc28bee5250c0f667c94a295706a44ed4d7e#diff-9bea2581a1fba611f2c10904857b8823R1268
> The original issue before HIVE-21714 was that the original files in the table
> survived an insert overwrite, and select(*)>0 was after that. HIVE-21714
> seems to enable writing empty files regardless of execution engine / table
> type, which is not the proper way, as the proper solution would be to
> completely avoid writing empty files for Tez (this is what HIVE-14014 was
> about). I found that changing condition to...
> {code}
> if (!isTez && (isStreaming || this.isInsertOverwrite))
> {code}
> (which could be an easy solution for external tables) breaks some test cases
> (both full ACID and MM) in insert_overwrite.q, which could mean they rely
> somehow on the empty generated file. We need to find a proper solution which
> is applicable for all table types without polluting external tables.
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