Sean Zhong created SPARK-17289:
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Summary: Sort based partial aggregation breaks due to SPARK-12978
Key: SPARK-17289
URL: https://issues.apache.org/jira/browse/SPARK-17289
Project: Spark
Issue Type: Bug
Reporter: Sean Zhong
For the following query:
{code}
val df2 = (0 to 1000).map(x => (x % 2, x.toString)).toDF("a",
"b").createOrReplaceTempView("t2")
spark.sql("select max(b) from t2 group by a").explain(true)
{code}
Now, the SortAggregator won't insert Sort operator before partial aggregation,
this will break sort-based partial aggregation.
{code}
== Physical Plan ==
SortAggregate(key=[a#5], functions=[max(b#6)], output=[max(b)#17])
+- *Sort [a#5 ASC], false, 0
+- Exchange hashpartitioning(a#5, 200)
+- SortAggregate(key=[a#5], functions=[partial_max(b#6)], output=[a#5,
max#19])
+- LocalTableScan [a#5, b#6]
{code}
In Spark 2.0 branch, the plan is:
{code}
== Physical Plan ==
SortAggregate(key=[a#5], functions=[max(b#6)], output=[max(b)#17])
+- *Sort [a#5 ASC], false, 0
+- Exchange hashpartitioning(a#5, 200)
+- SortAggregate(key=[a#5], functions=[partial_max(b#6)], output=[a#5,
max#19])
+- *Sort [a#5 ASC], false, 0
+- LocalTableScan [a#5, b#6]
{code}
This is related with SPARK-12978
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