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https://issues.apache.org/jira/browse/HIVE-20901?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Eugene Koifman reassigned HIVE-20901:
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> running compactor when there is nothing to do produces duplicate data
> ---------------------------------------------------------------------
>
> Key: HIVE-20901
> URL: https://issues.apache.org/jira/browse/HIVE-20901
> Project: Hive
> Issue Type: Bug
> Components: Transactions
> Affects Versions: 4.0.0
> Reporter: Eugene Koifman
> Assignee: Eugene Koifman
> Priority: Major
>
> suppose we run minor compaction 2 times, via alter table
> The 2nd request to compaction should have nothing to do but I don't think
> there is a check for that. It's visible in the context of HIVE-20823, where
> each compactor run produces a delta with new visibility suffix so we end up
> with something like
> {noformat}
> target/tmp/org.apache.hadoop.hive.ql.TestTxnCommands3-1541810844849/warehouse/t/
> ├── delete_delta_0000001_0000002_v0000019
> │ ├── _orc_acid_version
> │ └── bucket_00000
> ├── delete_delta_0000001_0000002_v0000021
> │ ├── _orc_acid_version
> │ └── bucket_00000
> ├── delta_0000001_0000001_0000
> │ ├── _orc_acid_version
> │ └── bucket_00000
> ├── delta_0000001_0000002_v0000019
> │ ├── _orc_acid_version
> │ └── bucket_00000
> ├── delta_0000001_0000002_v0000021
> │ ├── _orc_acid_version
> │ └── bucket_00000
> └── delta_0000002_0000002_0000
> ├── _orc_acid_version
> └── bucket_00000{noformat}
> i.e. 2 deltas with the same write ID range
> this is bad. Probably happens today as well but new run produces a delta
> with the same name and clobbers the previous one, which may interfere with
> writers
>
> need to investigate
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