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From "Selina Zhang (JIRA)" <>
Subject [jira] [Commented] (HIVE-6980) Drop table by using direct sql
Date Thu, 01 May 2014 18:27:16 GMT


Selina Zhang commented on HIVE-6980:

[~sershe]I have done the test based on 0.12 version. With delete cascade, drop table with
5000 partitions (oracle flavor) only takes less than 4 seconds(all partition data paths are
subdirectories of table path). Will do more test with different alter table/partitions combinations.

> Drop table by using direct sql
> ------------------------------
>                 Key: HIVE-6980
>                 URL:
>             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
> 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
> 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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