Jihoon Son created TAJO-1766:
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Summary: Improve the performance of cross join
Key: TAJO-1766
URL: https://issues.apache.org/jira/browse/TAJO-1766
Project: Tajo
Issue Type: Improvement
Components: distributed query plan
Reporter: Jihoon Son
Assignee: Jihoon Son
Fix For: 0.11.0
Cross join is one of the very heavy operations. Furthermore, this operator is
performed by a single worker in the current implementation. (Please see the
implementation of HashPartitioner. If partitionKeyIds is empty, getPartition()
always returns a single value.)
One possible alternative is executing cross join with broadcast join. That is,
outer table (smaller one) is always broadcasted, and join is performed by the
machine who stores a part of inner table.
To do so, a new session variable is required to set the broadcast threshold for
cross join.
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