Fix NullPointerException on null partition insert

Closes NVIDIA#1735

Signed-off-by: Gera Shegalov <gera@apache.org>

sql-plugin/src/main/scala/org/apache/spark/sql/rapids/GpuInsertIntoHadoopFsRelationCommand.scala

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2019, NVIDIA CORPORATION.
+ * Copyright (c) 2019-2021, NVIDIA CORPORATION.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -25,7 +25,7 @@ import org.apache.spark.internal.io.FileCommitProtocol
 import org.apache.spark.sql.{AnalysisException, SaveMode, SparkSession}
 import org.apache.spark.sql.catalyst.catalog.{BucketSpec, CatalogTable, CatalogTablePartition}
 import org.apache.spark.sql.catalyst.catalog.CatalogTypes.TablePartitionSpec
-import org.apache.spark.sql.catalyst.catalog.ExternalCatalogUtils.escapePathName
+import org.apache.spark.sql.catalyst.catalog.ExternalCatalogUtils.getPartitionPathString
 import org.apache.spark.sql.catalyst.expressions.Attribute
 import org.apache.spark.sql.catalyst.plans.logical.LogicalPlan
 import org.apache.spark.sql.catalyst.util.CaseInsensitiveMap
@@ -204,12 +204,7 @@ case class GpuInsertIntoHadoopFsRelationCommand(
       committer: FileCommitProtocol): Unit = {
     val staticPartitionPrefix = if (staticPartitions.nonEmpty) {
       "/" + partitionColumns.flatMap { p =>
-        staticPartitions.get(p.name) match {
-          case Some(value) =>
-            Some(escapePathName(p.name) + "=" + escapePathName(value))
-          case None =>
-            None
-        }
+        staticPartitions.get(p.name).map(getPartitionPathString(p.name, _))
       }.mkString("/")
     } else {
       ""

tests/src/test/scala/com/nvidia/spark/rapids/InsertPartitionSuite.scala

@@ -0,0 +1,39 @@
+/*
+ * Copyright (c) 2021, NVIDIA CORPORATION.
+ *
+ * Licensed 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 com.nvidia.spark.rapids
+
+import org.scalatest.BeforeAndAfterEach
+
+class InsertPartitionSuite extends SparkQueryCompareTestSuite with BeforeAndAfterEach {
+  var tableNr = 0
+
+  override def afterEach(): Unit = {
+    List(1, 2).foreach { tnr =>
+      SparkSessionHolder.sparkSession.sql(s"DROP TABLE t$tnr")
+    }
+  }
+
+  testSparkResultsAreEqual(
+    testName ="Insert null-value partition ",
+    spark => {
+      tableNr += 1
+      spark.sql(s"""CREATE TABLE t${tableNr}(i STRING, c STRING)
+                   |USING PARQUET PARTITIONED BY (c)""".stripMargin)
+      spark.sql(s"""INSERT OVERWRITE t${tableNr} PARTITION (c=null)
+                   |VALUES ('1')""".stripMargin)})(
+    _.sparkSession.sql(s"SELECT * FROM t$tableNr"))
+}