add test in ExplainSuite

Author: huaxingao

sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/trees/TreeNode.scala

@@ -545,8 +545,8 @@ abstract class TreeNode[BaseType <: TreeNode[BaseType]] extends Product {
     case None => Nil
     case Some(null) => Nil
     case Some(any) => any :: Nil
-    case map: CaseInsensitiveStringMap =>
-      truncatedString(map.entrySet().toArray(), "[", ", ", "]", maxFields) :: Nil
+    case map: CaseInsensitiveStringMap => truncatedString(
+        map.asCaseSensitiveMap().entrySet().toArray(), "[", ", ", "]", maxFields):: Nil
     case table: CatalogTable =>
       table.storage.serde match {
         case Some(serde) => table.identifier :: serde :: Nil

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

@@ -408,6 +408,21 @@ class ExplainSuite extends ExplainSuiteHelper with DisableAdaptiveExecutionSuite
       }
     }
   }
+
+  test("Explain UnresolvedRelation with CaseInsensitiveStringMap options") {
+    val tableName = "test"
+    withTable(tableName) {
+      val df1 = Seq((1L, "a"), (2L, "b"), (3L, "c")).toDF("id", "data")
+      df1.write.saveAsTable(tableName)
+      val df2 = spark.read
+        .option("key1", "value1")
+        .option("KEY2", "VALUE2")
+        .table(tableName)
+      // == Parsed Logical Plan ==
+      // 'UnresolvedRelation [test], [key1=value1, KEY2=VALUE2]
+      checkKeywordsExistsInExplain(df2, keywords = "[key1=value1, KEY2=VALUE2]")
+    }
+  }
 }
 
 class ExplainSuiteAE extends ExplainSuiteHelper with EnableAdaptiveExecutionSuite {