Fei Wang created SPARK-7289:
-------------------------------
Summary: push down sort when it's child is Limit
Key: SPARK-7289
URL: https://issues.apache.org/jira/browse/SPARK-7289
Project: Spark
Issue Type: Improvement
Components: SQL
Affects Versions: 1.3.1
Reporter: Fei Wang
Optimize following sql
`select key from (select * from testData limit 5) t order by key limit 5`
optimize it from
```
== Parsed Logical Plan ==
'Limit 5
'Sort ['key ASC], true
'Project ['key]
'Subquery t
'Limit 5
'Project [*]
'UnresolvedRelation [testData], None
== Analyzed Logical Plan ==
Limit 5
Sort [key#0 ASC], true
Project [key#0]
Subquery t
Limit 5
Project [key#0,value#1]
Subquery testData
LogicalRDD [key#0,value#1], MapPartitionsRDD[1]
== Optimized Logical Plan ==
Limit 5
Sort [key#0 ASC], true
Project [key#0]
Limit 5
LogicalRDD [key#0,value#1], MapPartitionsRDD[1]
== Physical Plan ==
TakeOrdered 5, [key#0 ASC]
Project [key#0]
Limit 5
PhysicalRDD [key#0,value#1], MapPartitionsRDD[1]
```
to
```
== Parsed Logical Plan ==
'Limit 5
'Sort ['key ASC], true
'Project ['key]
'Subquery t
'Limit 5
'Project [*]
'UnresolvedRelation [testData], None
== Analyzed Logical Plan ==
Limit 5
Sort [key#0 ASC], true
Project [key#0]
Subquery t
Limit 5
Project [key#0,value#1]
Subquery testData
LogicalRDD [key#0,value#1], MapPartitionsRDD[1]
== Optimized Logical Plan ==
Limit 5
Sort [key#0 ASC], true
Project [key#0]
LogicalRDD [key#0,value#1], MapPartitionsRDD[1]
== Physical Plan ==
TakeOrdered 5, [key#0 ASC]
Project [key#0]
PhysicalRDD [key#0,value#1], MapPartitionsRDD[1]
```
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