[jira] [Commented] (HIVE-6980) Drop table by using direct sql

["Sergey Shelukhin (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HIVE-6980?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13986240#comment-13986240 ] 

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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