[SPARK-16318][SQL] Implement all remaining xpath functions

## What changes were proposed in this pull request?
This patch implements all remaining xpath functions that Hive supports and not natively supported in Spark: xpath_int, xpath_short, xpath_long, xpath_float, xpath_double, xpath_string, and xpath.

## How was this patch tested?
Added unit tests and end-to-end tests.

Author: petermaxlee <petermaxlee@gmail.com>

Closes #13991 from petermaxlee/SPARK-16318.

2 files changed, 62 insertions, 32 deletions

diff --git a/sql/core/src/test/scala/org/apache/spark/sql/XPathFunctionsSuite.scala b/sql/core/src/test/scala/org/apache/spark/sql/XPathFunctionsSuite.scala
new file mode 100644
index 0000000000..1d33e7970b
--- /dev/null
+++ b/sql/core/src/test/scala/org/apache/spark/sql/XPathFunctionsSuite.scala
@@ -0,0 +1,62 @@
+/*
+ * 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.spark.sql.test.SharedSQLContext
+
+/**
+ * End-to-end tests for xpath expressions.
+ */
+class XPathFunctionsSuite extends QueryTest with SharedSQLContext {
+  import testImplicits._
+
+  test("xpath_boolean") {
+    val df = Seq("<a><b>b</b></a>").toDF("xml")
+    checkAnswer(df.selectExpr("xpath_boolean(xml, 'a/b')"), Row(true))
+  }
+
+  test("xpath_short, xpath_int, xpath_long") {
+    val df = Seq("<a><b>1</b><b>2</b></a>").toDF("xml")
+    checkAnswer(
+      df.selectExpr(
+        "xpath_short(xml, 'sum(a/b)')",
+        "xpath_int(xml, 'sum(a/b)')",
+        "xpath_long(xml, 'sum(a/b)')"),
+      Row(3.toShort, 3, 3L))
+  }
+
+  test("xpath_float, xpath_double, xpath_number") {
+    val df = Seq("<a><b>1.0</b><b>2.1</b></a>").toDF("xml")
+    checkAnswer(
+      df.selectExpr(
+        "xpath_float(xml, 'sum(a/b)')",
+        "xpath_double(xml, 'sum(a/b)')",
+        "xpath_number(xml, 'sum(a/b)')"),
+      Row(3.1.toFloat, 3.1, 3.1))
+  }
+
+  test("xpath_string") {
+    val df = Seq("<a><b>b</b><c>cc</c></a>").toDF("xml")
+    checkAnswer(df.selectExpr("xpath_string(xml, 'a/c')"), Row("cc"))
+  }
+
+  test("xpath") {
+    val df = Seq("<a><b>b1</b><b>b2</b><b>b3</b><c>c1</c><c>c2</c></a>").toDF("xml")
+    checkAnswer(df.selectExpr("xpath(xml, 'a/*/text()')"), Row(Seq("b1", "b2", "b3", "c1", "c2")))
+  }
+}
diff --git a/sql/core/src/test/scala/org/apache/spark/sql/XmlFunctionsSuite.scala b/sql/core/src/test/scala/org/apache/spark/sql/XmlFunctionsSuite.scala
deleted file mode 100644
index 532d48cc26..0000000000
--- a/sql/core/src/test/scala/org/apache/spark/sql/XmlFunctionsSuite.scala
+++ /dev/null
@@ -1,32 +0,0 @@
-/*
- * 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.spark.sql.test.SharedSQLContext
-
-/**
- * End-to-end tests for XML expressions.
- */
-class XmlFunctionsSuite extends QueryTest with SharedSQLContext {
-  import testImplicits._
-
-  test("xpath_boolean") {
-    val df = Seq("<a><b>b</b></a>" -> "a/b").toDF("xml", "path")
-    checkAnswer(df.selectExpr("xpath_boolean(xml, path)"), Row(true))
-  }
-}