[jira] [Commented] (HIVE-19387) Truncate table for Acid tables conflicts with ResultSet cache

["Eugene Koifman (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HIVE-19387?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16539306#comment-16539306 ] 

Eugene Koifman commented on HIVE-19387:
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truncate table/partition is handled by {{HiveMetaStore.truncate_table(String,String,List)}}
It works by deleting all files under an X lock.
Since it's not writing anything it doesn't create a writeId and so RS Cache invalidation doesn't know about this since it relies on ValidWriteIdList.
I suspect Incremental MV maintenance would have the same issue.

> Truncate table for Acid tables conflicts with ResultSet cache
> -------------------------------------------------------------
>
>                 Key: HIVE-19387
>                 URL: https://issues.apache.org/jira/browse/HIVE-19387
>             Project: Hive
>          Issue Type: New Feature
>          Components: Transactions
>            Reporter: Eugene Koifman
>            Assignee: Eugene Koifman
>            Priority: Major
>
> How should this work?  Should it work like Insert Overwrite T select * from T where 1=2?
> This should create a new empty base_x/ and thus operate w/o violating Snapshot Isolation semantics.
> This makes sense for specific partition or unpartitioned table.  What about "Truncate T" where T is partitioned?  Is the expectation to wipe out all partition info or to make each partition empty?



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