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Posted to dev@hive.apache.org by "Sahil Takiar (JIRA)" <ji...@apache.org> on 2017/06/30 01:05:00 UTC
[jira] [Created] (HIVE-16998) Add config to enable HoS DPP only for
map-joins
Sahil Takiar created HIVE-16998:
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Summary: Add config to enable HoS DPP only for map-joins
Key: HIVE-16998
URL: https://issues.apache.org/jira/browse/HIVE-16998
Project: Hive
Issue Type: Sub-task
Components: Logical Optimizer, Spark
Reporter: Sahil Takiar
Assignee: Sahil Takiar
HoS DPP will split a given operator tree in two under the following conditions: it has detected that the query can benefit from DPP, and the filter is not a map-join (see SplitOpTreeForDPP).
This can hurt performance if the the non-partitioned side of the join involves a complex operator tree - e.g. the query {{select count(*) from srcpart where srcpart.ds in (select max(srcpart.ds) from srcpart union all select min(srcpart.ds) from srcpart)}} will require running the subquery twice, once in each Spark job.
Queries with map-joins don't get split into two operator trees and thus don't suffer from this drawback. Thus, it would be nice to have a config key that just enables DPP on HoS for map-joins.
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