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From sro...@apache.org
Subject spark git commit: [SPARK-18111][SQL] Wrong ApproximatePercentile answer when multiple records have the minimum value
Date Tue, 01 Nov 2016 13:11:29 GMT
Repository: spark
Updated Branches:
  refs/heads/master 623fc7fc6 -> cb80edc26


[SPARK-18111][SQL] Wrong ApproximatePercentile answer when multiple records have the minimum
value

## What changes were proposed in this pull request?

When multiple records have the minimum value, the answer of ApproximatePercentile is wrong.
## How was this patch tested?

add a test case

Author: wangzhenhua <wangzhenhua@huawei.com>

Closes #15641 from wzhfy/percentile.


Project: http://git-wip-us.apache.org/repos/asf/spark/repo
Commit: http://git-wip-us.apache.org/repos/asf/spark/commit/cb80edc2
Tree: http://git-wip-us.apache.org/repos/asf/spark/tree/cb80edc2
Diff: http://git-wip-us.apache.org/repos/asf/spark/diff/cb80edc2

Branch: refs/heads/master
Commit: cb80edc26349e2e358d27fe2ae8e5d6959b77fab
Parents: 623fc7f
Author: wangzhenhua <wangzhenhua@huawei.com>
Authored: Tue Nov 1 13:11:24 2016 +0000
Committer: Sean Owen <sowen@cloudera.com>
Committed: Tue Nov 1 13:11:24 2016 +0000

----------------------------------------------------------------------
 .../spark/sql/catalyst/util/QuantileSummaries.scala      |  4 +++-
 .../spark/sql/ApproximatePercentileQuerySuite.scala      | 11 +++++++++++
 2 files changed, 14 insertions(+), 1 deletion(-)
----------------------------------------------------------------------


http://git-wip-us.apache.org/repos/asf/spark/blob/cb80edc2/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/util/QuantileSummaries.scala
----------------------------------------------------------------------
diff --git a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/util/QuantileSummaries.scala
b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/util/QuantileSummaries.scala
index 27928c4..04f4ff2 100644
--- a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/util/QuantileSummaries.scala
+++ b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/util/QuantileSummaries.scala
@@ -264,7 +264,9 @@ object QuantileSummaries {
     res.prepend(head)
     // If necessary, add the minimum element:
     val currHead = currentSamples.head
-    if (currHead.value < head.value) {
+    // don't add the minimum element if `currentSamples` has only one element (both `currHead`
and
+    // `head` point to the same element)
+    if (currHead.value <= head.value && currentSamples.length > 1) {
       res.prepend(currentSamples.head)
     }
     res.toArray

http://git-wip-us.apache.org/repos/asf/spark/blob/cb80edc2/sql/core/src/test/scala/org/apache/spark/sql/ApproximatePercentileQuerySuite.scala
----------------------------------------------------------------------
diff --git a/sql/core/src/test/scala/org/apache/spark/sql/ApproximatePercentileQuerySuite.scala
b/sql/core/src/test/scala/org/apache/spark/sql/ApproximatePercentileQuerySuite.scala
index 37d7c44..e98092d 100644
--- a/sql/core/src/test/scala/org/apache/spark/sql/ApproximatePercentileQuerySuite.scala
+++ b/sql/core/src/test/scala/org/apache/spark/sql/ApproximatePercentileQuerySuite.scala
@@ -64,6 +64,17 @@ class ApproximatePercentileQuerySuite extends QueryTest with SharedSQLContext
{
     }
   }
 
+  test("percentile_approx, multiple records with the minimum value in a partition") {
+    withTempView(table) {
+      spark.sparkContext.makeRDD(Seq(1, 1, 2, 1, 1, 3, 1, 1, 4, 1, 1, 5), 4).toDF("col")
+        .createOrReplaceTempView(table)
+      checkAnswer(
+        spark.sql(s"SELECT percentile_approx(col, array(0.5)) FROM $table"),
+        Row(Seq(1.0D))
+      )
+    }
+  }
+
   test("percentile_approx, with different accuracies") {
 
     withTempView(table) {


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