SPARK-2813: [SQL] Implement SQRT() directly in Spark SQL

This PR adds a native implementation for SQL SQRT() and thus avoids delegating this function to Hive.

Author: William Benton <willb@redhat.com>

Closes #1750 from willb/spark-2813 and squashes the following commits:

22c8a79 [William Benton] Fixed missed newline from rebase
d673861 [William Benton] Added string coercions for SQRT and associated test case
e125df4 [William Benton] Added ExpressionEvaluationSuite test cases for SQRT
7b84bcd [William Benton] SQL SQRT now properly returns NULL for NULL inputs
8256971 [William Benton] added SQRT test to SqlQuerySuite
504d2e5 [William Benton] Added native SQRT implementation

1 files changed, 14 insertions, 0 deletions

diff --git a/sql/core/src/test/scala/org/apache/spark/sql/SQLQuerySuite.scala b/sql/core/src/test/scala/org/apache/spark/sql/SQLQuerySuite.scala
index 9b2a36d33f..4047bc0672 100644
--- a/sql/core/src/test/scala/org/apache/spark/sql/SQLQuerySuite.scala
+++ b/sql/core/src/test/scala/org/apache/spark/sql/SQLQuerySuite.scala
@@ -34,6 +34,20 @@ class SQLQuerySuite extends QueryTest {
       "test")
   }
 
+  test("SQRT") {
+    checkAnswer(
+      sql("SELECT SQRT(key) FROM testData"),
+      (1 to 100).map(x => Row(math.sqrt(x.toDouble))).toSeq
+    )
+  }
+  
+  test("SQRT with automatic string casts") {
+    checkAnswer(
+      sql("SELECT SQRT(CAST(key AS STRING)) FROM testData"),
+      (1 to 100).map(x => Row(math.sqrt(x.toDouble))).toSeq
+    )
+  }
+  
   test("SPARK-2407 Added Parser of SQL SUBSTR()") {
     checkAnswer(
       sql("SELECT substr(tableName, 1, 2) FROM tableName"),