From 9617c2d982ed799580957a1467d47f42e8124636 Mon Sep 17 00:00:00 2001
From: Zhenhua Wang <wangzhenhua@huawei.com>
Date: Thu, 28 Dec 2017 16:36:23 +0800
Subject: [PATCH] fix

---
 .../command/AnalyzeColumnCommand.scala        |  7 ++++++-
 .../spark/sql/StatisticsCollectionSuite.scala | 21 +++++++++++++++++--
 2 files changed, 25 insertions(+), 3 deletions(-)

diff --git a/sql/core/src/main/scala/org/apache/spark/sql/execution/command/AnalyzeColumnCommand.scala b/sql/core/src/main/scala/org/apache/spark/sql/execution/command/AnalyzeColumnCommand.scala
index e3bb4d357b39..1122522ccb4c 100644
--- a/sql/core/src/main/scala/org/apache/spark/sql/execution/command/AnalyzeColumnCommand.scala
+++ b/sql/core/src/main/scala/org/apache/spark/sql/execution/command/AnalyzeColumnCommand.scala
@@ -143,7 +143,12 @@ case class AnalyzeColumnCommand(
       val percentilesRow = new QueryExecution(sparkSession, Aggregate(Nil, namedExprs, relation))
         .executedPlan.executeTake(1).head
       attrsToGenHistogram.zipWithIndex.foreach { case (attr, i) =>
-        attributePercentiles += attr -> percentilesRow.getArray(i)
+        val percentiles = percentilesRow.getArray(i)
+        // When there is no non-null value, `percentiles` is null. In such case, there is no
+        // need to generate histogram.
+        if (percentiles != null) {
+          attributePercentiles += attr -> percentiles
+        }
       }
     }
     AttributeMap(attributePercentiles.toSeq)
diff --git a/sql/core/src/test/scala/org/apache/spark/sql/StatisticsCollectionSuite.scala b/sql/core/src/test/scala/org/apache/spark/sql/StatisticsCollectionSuite.scala
index fba5d2652d3f..b11e79853205 100644
--- a/sql/core/src/test/scala/org/apache/spark/sql/StatisticsCollectionSuite.scala
+++ b/sql/core/src/test/scala/org/apache/spark/sql/StatisticsCollectionSuite.scala
@@ -85,13 +85,24 @@ class StatisticsCollectionSuite extends StatisticsCollectionTestBase with Shared
   test("analyze empty table") {
     val table = "emptyTable"
     withTable(table) {
-      sql(s"CREATE TABLE $table (key STRING, value STRING) USING PARQUET")
+      val df = Seq.empty[Int].toDF("key")
+      df.write.format("json").saveAsTable(table)
       sql(s"ANALYZE TABLE $table COMPUTE STATISTICS noscan")
       val fetchedStats1 = checkTableStats(table, hasSizeInBytes = true, expectedRowCounts = None)
       assert(fetchedStats1.get.sizeInBytes == 0)
       sql(s"ANALYZE TABLE $table COMPUTE STATISTICS")
       val fetchedStats2 = checkTableStats(table, hasSizeInBytes = true, expectedRowCounts = Some(0))
       assert(fetchedStats2.get.sizeInBytes == 0)
+
+      val expectedColStat =
+        "key" -> ColumnStat(0, None, None, 0, IntegerType.defaultSize, IntegerType.defaultSize)
+
+      // There won't be histogram for empty column.
+      Seq("true", "false").foreach { histogramEnabled =>
+        withSQLConf(SQLConf.HISTOGRAM_ENABLED.key -> histogramEnabled) {
+          checkColStats(df, mutable.LinkedHashMap(expectedColStat))
+        }
+      }
     }
   }
 
@@ -178,7 +189,13 @@ class StatisticsCollectionSuite extends StatisticsCollectionTestBase with Shared
     val expectedColStats = dataTypes.map { case (tpe, idx) =>
       (s"col$idx", ColumnStat(0, None, None, 1, tpe.defaultSize.toLong, tpe.defaultSize.toLong))
     }
-    checkColStats(df, mutable.LinkedHashMap(expectedColStats: _*))
+
+    // There won't be histograms for null columns.
+    Seq("true", "false").foreach { histogramEnabled =>
+      withSQLConf(SQLConf.HISTOGRAM_ENABLED.key -> histogramEnabled) {
+        checkColStats(df, mutable.LinkedHashMap(expectedColStats: _*))
+      }
+    }
   }
 
   test("number format in statistics") {