From 5a3533e779d8e43ce0980203dfd3cbe343cc7d0a Mon Sep 17 00:00:00 2001
From: Dongjoon Hyun <dongjoon@apache.org>
Date: Thu, 9 Jun 2016 22:46:51 -0700
Subject: [PATCH] [SPARK-15696][SQL] Improve `crosstab` to have a consistent
column order
## What changes were proposed in this pull request?
Currently, `crosstab` returns a Dataframe having **random-order** columns obtained by just `distinct`. Also, the documentation of `crosstab` shows the result in a sorted order which is different from the current implementation. This PR explicitly constructs the columns in a sorted order in order to improve user experience. Also, this implementation gives the same result with the documentation.
**Before**
```scala
scala> spark.createDataFrame(Seq((1, 1), (1, 2), (2, 1), (2, 1), (2, 3), (3, 2), (3, 3))).toDF("key", "value").stat.crosstab("key", "value").show()
+---------+---+---+---+
|key_value| 3| 2| 1|
+---------+---+---+---+
| 2| 1| 0| 2|
| 1| 0| 1| 1|
| 3| 1| 1| 0|
+---------+---+---+---+
scala> spark.createDataFrame(Seq((1, "a"), (1, "b"), (2, "a"), (2, "a"), (2, "c"), (3, "b"), (3, "c"))).toDF("key", "value").stat.crosstab("key", "value").show()
+---------+---+---+---+
|key_value| c| a| b|
+---------+---+---+---+
| 2| 1| 2| 0|
| 1| 0| 1| 1|
| 3| 1| 0| 1|
+---------+---+---+---+
```
**After**
```scala
scala> spark.createDataFrame(Seq((1, 1), (1, 2), (2, 1), (2, 1), (2, 3), (3, 2), (3, 3))).toDF("key", "value").stat.crosstab("key", "value").show()
+---------+---+---+---+
|key_value| 1| 2| 3|
+---------+---+---+---+
| 2| 2| 0| 1|
| 1| 1| 1| 0|
| 3| 0| 1| 1|
+---------+---+---+---+
scala> spark.createDataFrame(Seq((1, "a"), (1, "b"), (2, "a"), (2, "a"), (2, "c"), (3, "b"), (3, "c"))).toDF("key", "value").stat.crosstab("key", "value").show()
+---------+---+---+---+
|key_value| a| b| c|
+---------+---+---+---+
| 2| 2| 0| 1|
| 1| 1| 1| 0|
| 3| 0| 1| 1|
+---------+---+---+---+
```
## How was this patch tested?
Pass the Jenkins tests with updated testcases.
Author: Dongjoon Hyun <dongjoon@apache.org>
Closes #13436 from dongjoon-hyun/SPARK-15696.
---
.../org/apache/spark/sql/execution/stat/StatFunctions.scala | 4 ++--
.../java/test/org/apache/spark/sql/JavaDataFrameSuite.java | 4 ++--
2 files changed, 4 insertions(+), 4 deletions(-)
diff --git a/sql/core/src/main/scala/org/apache/spark/sql/execution/stat/StatFunctions.scala b/sql/core/src/main/scala/org/apache/spark/sql/execution/stat/StatFunctions.scala
index 9c0406168e..ea58df70b3 100644
--- a/sql/core/src/main/scala/org/apache/spark/sql/execution/stat/StatFunctions.scala
+++ b/sql/core/src/main/scala/org/apache/spark/sql/execution/stat/StatFunctions.scala
@@ -423,9 +423,9 @@ private[sql] object StatFunctions extends Logging {
def cleanElement(element: Any): String = {
if (element == null) "null" else element.toString
}
- // get the distinct values of column 2, so that we can make them the column names
+ // get the distinct sorted values of column 2, so that we can make them the column names
val distinctCol2: Map[Any, Int] =
- counts.map(e => cleanElement(e.get(1))).distinct.zipWithIndex.toMap
+ counts.map(e => cleanElement(e.get(1))).distinct.sorted.zipWithIndex.toMap
val columnSize = distinctCol2.size
require(columnSize < 1e4, s"The number of distinct values for $col2, can't " +
s"exceed 1e4. Currently $columnSize")
diff --git a/sql/core/src/test/java/test/org/apache/spark/sql/JavaDataFrameSuite.java b/sql/core/src/test/java/test/org/apache/spark/sql/JavaDataFrameSuite.java
index 1e8f1062c5..0152f3f85a 100644
--- a/sql/core/src/test/java/test/org/apache/spark/sql/JavaDataFrameSuite.java
+++ b/sql/core/src/test/java/test/org/apache/spark/sql/JavaDataFrameSuite.java
@@ -246,8 +246,8 @@ public class JavaDataFrameSuite {
Dataset<Row> crosstab = df.stat().crosstab("a", "b");
String[] columnNames = crosstab.schema().fieldNames();
Assert.assertEquals("a_b", columnNames[0]);
- Assert.assertEquals("2", columnNames[1]);
- Assert.assertEquals("1", columnNames[2]);
+ Assert.assertEquals("1", columnNames[1]);
+ Assert.assertEquals("2", columnNames[2]);
List<Row> rows = crosstab.collectAsList();
Collections.sort(rows, crosstabRowComparator);
Integer count = 1;
--
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