Davies Liu 0f72e4f04b [SPARK-16958] [SQL] Reuse subqueries within the same query ... ## What changes were proposed in this pull request? There could be multiple subqueries that generate same results, we could re-use the result instead of running it multiple times. This PR also cleanup up how we run subqueries. For SQL query ```sql select id,(select avg(id) from t) from t where id > (select avg(id) from t) ``` The explain is ``` == Physical Plan == *Project [id#15L, Subquery subquery29 AS scalarsubquery()#35] : +- Subquery subquery29 : +- *HashAggregate(keys=[], functions=[avg(id#15L)]) : +- Exchange SinglePartition : +- *HashAggregate(keys=[], functions=[partial_avg(id#15L)]) : +- *Range (0, 1000, splits=4) +- *Filter (cast(id#15L as double) > Subquery subquery29) : +- Subquery subquery29 : +- *HashAggregate(keys=[], functions=[avg(id#15L)]) : +- Exchange SinglePartition : +- *HashAggregate(keys=[], functions=[partial_avg(id#15L)]) : +- *Range (0, 1000, splits=4) +- *Range (0, 1000, splits=4) ``` The visualized plan:  ## How was this patch tested? Existing tests. Author: Davies Liu <davies@databricks.com> Closes #14548 from davies/subq.		2016-08-11 09:47:19 -07:00
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src	[SPARK-16958] [SQL] Reuse subqueries within the same query	2016-08-11 09:47:19 -07:00
pom.xml	[SPARK-16535][BUILD] In pom.xml, remove groupId which is redundant definition and inherited from the parent	2016-07-19 11:59:46 +01:00