Add a test

Author: rxin

sql/core/src/test/scala/org/apache/spark/sql/ConfigBehaviorSuite.scala

@@ -0,0 +1,64 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.spark.sql
+
+import org.apache.commons.math3.stat.inference.ChiSquareTest
+
+import org.apache.spark.sql.internal.SQLConf
+import org.apache.spark.sql.test.SharedSQLContext
+
+
+class ConfigBehaviorSuite extends QueryTest with SharedSQLContext {
+
+  import testImplicits._
+
+  test("SPARK-22160 spark.sql.execution.rangeExchange.sampleSizePerPartition") {
+    // In this test, we run a sort and compute the histogram for partition size post shuffle.
+    // With a high sample count, the partition size should be more evenly distributed, and has a
+    // low chi-sq test value.
+
+    val numPartitions = 4
+
+    def computeChiSquareTest(): Double = {
+      val n = 10000
+      // Trigger a sort
+      val data = spark.range(0, n, 1, 1).sort('id)
+        .selectExpr("SPARK_PARTITION_ID() pid", "id").as[(Int, Long)].collect()
+
+      // Compute histogram for the number of records per partition post sort
+      val dist = data.groupBy(_._1).map(_._2.length.toLong).toArray
+      assert(dist.length == 4)
+
+      new ChiSquareTest().chiSquare(
+        Array.fill(numPartitions) { n.toDouble / numPartitions },
+        dist)
+    }
+
+    withSQLConf(SQLConf.SHUFFLE_PARTITIONS.key -> numPartitions.toString) {
+      // The default chi-sq value should be low
+      assert(computeChiSquareTest() < 100)
+
+      withSQLConf(SQLConf.RANGE_EXCHANGE_SAMPLE_SIZE_PER_PARTITION.key -> "1") {
+        // If we only sample one point, the range boundaries will be pretty bad and the
+        // chi-sq value would be very high.
+        assert(computeChiSquareTest() > 1000)
+      }
+    }
+  }
+
+}