[SPARK-9830][SQL] Remove AggregateExpression1 and Aggregate Operator used to evaluate AggregateExpression1s

https://issues.apache.org/jira/browse/SPARK-9830

This PR contains the following main changes.
* Removing `AggregateExpression1`.
* Removing `Aggregate` operator, which is used to evaluate `AggregateExpression1`.
* Removing planner rule used to plan `Aggregate`.
* Linking `MultipleDistinctRewriter` to analyzer.
* Renaming `AggregateExpression2` to `AggregateExpression` and `AggregateFunction2` to `AggregateFunction`.
* Updating places where we create aggregate expression. The way to create aggregate expressions is `AggregateExpression(aggregateFunction, mode, isDistinct)`.
* Changing `val`s in `DeclarativeAggregate`s that touch children of this function to `lazy val`s (when we create aggregate expression in DataFrame API, children of an aggregate function can be unresolved).

Author: Yin Huai <yhuai@databricks.com>

Closes #9556 from yhuai/removeAgg1.

1 files changed, 1 insertions, 1 deletions

diff --git a/python/pyspark/sql/dataframe.py b/python/pyspark/sql/dataframe.py
index b97c94dad8..0dd75ba7ca 100644
--- a/python/pyspark/sql/dataframe.py
+++ b/python/pyspark/sql/dataframe.py
@@ -866,7 +866,7 @@ class DataFrame(object):
         This is a variant of :func:`select` that accepts SQL expressions.
 
         >>> df.selectExpr("age * 2", "abs(age)").collect()
-        [Row((age * 2)=4, 'abs(age)=2), Row((age * 2)=10, 'abs(age)=5)]
+        [Row((age * 2)=4, abs(age)=2), Row((age * 2)=10, abs(age)=5)]
         """
         if len(expr) == 1 and isinstance(expr[0], list):
             expr = expr[0]