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https://issues.apache.org/jira/browse/HIVE-6980?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13986240#comment-13986240
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Sergey Shelukhin commented on HIVE-6980:
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Hmm... I don't think deleting via cascade will be much faster, DN will probably
issue separate queries just like for selects. Batch delete could be done w/join
or subquery, that is what I had in mind in original jira
> Drop table by using direct sql
> ------------------------------
>
> Key: HIVE-6980
> URL: https://issues.apache.org/jira/browse/HIVE-6980
> Project: Hive
> Issue Type: Improvement
> Components: Metastore
> Affects Versions: 0.12.0
> Reporter: Selina Zhang
> Assignee: Selina Zhang
>
> Dropping table which has lots of partitions is slow. Even after applying the
> patch of HIVE-6265, the drop table still takes hours (100K+ partitions).
> The fixes come with two parts:
> 1. use directSQL to query the partitions protect mode;
> the current implementation needs to transfer the Partition object to client
> and check the protect mode for each partition. I'd like to move this part of
> logic to metastore. The check will be done by direct sql (if direct sql is
> disabled, execute the same logic in the ObjectStore);
> 2. use directSQL to drop partitions for table;
> there maybe two solutions here:
> 1. add "DELETE CASCADE" in the schema. In this way we only need to delete
> entries from partitions table use direct sql. May need to change
> datanucleus.deletionPolicy = DataNucleus.
> 2. clean up the dependent tables by issue DELETE statement. This also needs
> to turn on datanucleus.query.sql.allowAll
> Both of above solutions should be able to fix the problem. The DELETE CASCADE
> has to change schemas and prepare upgrade scripts. The second solutions added
> maintenance cost if new tables added in the future releases.
> Please advice.
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