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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