[SPARK-18841][SQL]fix PushProjectionThroughUnion throw exception when there are same column name

[windpiger]

What changes were proposed in this pull request?

a union SQL with the same column name, after apply the rule RemoveAliasOnlyProject&PushProjectionThroughUnion many times, it will throw a exception

The reason is that RemoveAliasOnlyProject rule remove the right project child(alias only project) of Union, and replace the attribute of Union & the left project child of Union, then apply PushProjectionThroughUnion rule ,as the output attributes of a union are always equal to the left child's output, so it will throw a exception that the left child do not contain an attribute of the Union(RemoveAliasOnlyProject has replace it with right column).

for example:

    >spark.sql("DROP TABLE IF EXISTS p1")
    >spark.sql("DROP TABLE IF EXISTS p2")
    >spark.sql("DROP TABLE IF EXISTS p3")
    >spark.sql("CREATE TABLE p1 (col int)" )
    >spark.sql("CREATE TABLE p2 (col int)")
    >spark.sql("CREATE TABLE p3 (col int)")
    >spark.sql("set spark.sql.crossJoin.enabled = true")
    >spark.sql("SELECT 1 as cste,col FROM (SELECT col as col FROM (SELECT p1.col as col FROM p1 LEFT JOIN p2 UNION ALL SELECT col FROM p3 ) T1) T2").show

exception:

key not found: col#16
java.util.NoSuchElementException: key not found: col#16
        at scala.collection.MapLike$class.default(MapLike.scala:228)
        at org.apache.spark.sql.catalyst.expressions.AttributeMap.default(AttributeMap.scala:31)
        at scala.collection.MapLike$class.apply(MapLike.scala:141)
        at org.apache.spark.sql.catalyst.expressions.AttributeMap.apply(AttributeMap.scala:31)
        at org.apache.spark.sql.catalyst.optimizer.PushProjectionThroughUnion$$anonfun$2.applyOrElse(Optimizer.scala:346)
        at org.apache.spark.sql.catalyst.optimizer.PushProjectionThroughUnion$$anonfun$2.applyOrElse(Optimizer.scala:345)
        at org.apache.spark.sql.catalyst.trees.TreeNode$$anonfun$3.apply(TreeNode.scala:292)
        at org.apache.spark.sql.catalyst.trees.TreeNode$$anonfun$3.apply(TreeNode.scala:292)
        at org.apache.spark.sql.catalyst.trees.CurrentOrigin$.withOrigin(TreeNode.scala:74)
        at org.apache.spark.sql.catalyst.trees.TreeNode.transformDown(TreeNode.scala:291)
        at org.apache.spark.sql.catalyst.trees.TreeNode.transform(TreeNode.scala:281)
        at org.apache.spark.sql.catalyst.optimizer.PushProjectionThroughUnion$.org$apache$spark$sql$catalyst$optimizer$PushProjectionThroughUnion$$pushToRight(Optimizer.scala:345)
        at org.apache.spark.sql.catalyst.optimizer.PushProjectionThroughUnion$$anonfun$apply$4$$anonfun$8$$anonfun$apply$31.apply(Optimizer.scala:378)
        at org.apache.spark.sql.catalyst.optimizer.PushProjectionThroughUnion$$anonfun$apply$4$$anonfun$8$$anonfun$apply$31.apply(Optimizer.scala:378)
        at scala.collection.TraversableLike$$anonfun$map$1.apply(TraversableLike.scala:234)
        at scala.collection.TraversableLike$$anonfun$map$1.apply(TraversableLike.scala:234)
        at scala.collection.immutable.List.foreach(List.scala:381)
        at scala.collection.TraversableLike$class.map(TraversableLike.scala:234)
        at scala.collection.immutable.List.map(List.scala:285)
        at org.apache.spark.sql.catalyst.optimizer.PushProjectionThroughUnion$$anonfun$apply$4$$anonfun$8.apply(Optimizer.scala:378)

How was this patch tested?

unit test added

[SparkQA]

Test build #70086 has finished for PR 16267 at commit b7b27af.

• This patch fails MiMa tests.
• This patch merges cleanly.
• This patch adds no public classes.

[SparkQA]

Test build #70087 has finished for PR 16267 at commit ab6d8d4.

• This patch passes all tests.
• This patch merges cleanly.
• This patch adds no public classes.

[windpiger]

cc @hvanhovell @cloud-fan