[HIVE-6980] Drop table by using direct sql

• Type: Improvement
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 0.12.0
• Fix Version/s: 4.0.0-alpha-1
• Component/s: Metastore
• Assignee: Peter Vary
• Reporter: Selina Zhang
• Created: 28/Apr/14 00:10
• Updated: 17/Nov/22 08:54
• Resolved: 25/May/18 08:17

Description

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.

Issue Links

• Dependent: HIVE-19503 Create a test that checks for dropPartitions with directSql
• duplicates: HIVE-22702 ALTER TABLE REMOVE PARTITION is inefficient
• Is contained by: HIVE-7195 Improve Metastore performance
• is related to: HIVE-20554 Unable to drop an external table after renaming it.
• links to: Review board link