[jira] [Created] (HIVE-24237) Multi level/dimensional bucketing in Hive

["Pushpender Garg (Jira)" <ji...@apache.org>]

Pushpender Garg created HIVE-24237:
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             Summary: Multi level/dimensional bucketing in Hive
                 Key: HIVE-24237
                 URL: https://issues.apache.org/jira/browse/HIVE-24237
             Project: Hive
          Issue Type: New Feature
          Components: Database/Schema
    Affects Versions: 3.1.2, 3.1.1
            Reporter: Pushpender Garg


Hive can considerably optimize the execution of certain queries like filter, aggregations, joins, if bucketed columns are used in query for these operations. Buckets can be created on multiple columns as well where hash function is computed after merging all bucket columns. 

The problem is that if buckets are created on multiple columns but query is on subset of those columns then hive doesn't optimize that query. Unless all bucket columns are used as predicate, bucketing will not be utilized. Solution proposed in this document is to solve this problem such that even if subset of bucket columns are used still hive will be able to optimize that query.

Instead of storing data in single dimensional buckets it can be stored in multi-dimensional buckets when multiple columns are given. If subset of bucketed columns is used as predicates in query then based on hash value of individual columns, appropriate buckets can be identified and only those buckets will be scanned. This will enable optimizations even when single column or few columns are used in querying  



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