[SPARK-20751][SQL] Add built-in SQL Function - COT

sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/analysis/FunctionRegistry.scala

@@ -234,6 +234,7 @@ object FunctionRegistry {
     expression[StringToMap]("str_to_map"),
     expression[Sqrt]("sqrt"),
     expression[Tan]("tan"),
+    expression[Cot]("cot"),
     expression[Tanh]("tanh"),
 
     expression[Add]("+"),

sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/mathExpressions.scala

@@ -543,6 +543,24 @@ case class Sqrt(child: Expression) extends UnaryMathExpression(math.sqrt, "SQRT"
   """)
 case class Tan(child: Expression) extends UnaryMathExpression(math.tan, "TAN")
 
+@ExpressionDescription(
+  usage = "_FUNC_(expr) - Returns the cotangent of `expr`.",
+  extended = """
+    Examples:
+      > SELECT _FUNC_(1);
+       0.6420926159343306
+  """)
+case class Cot(child: Expression)
+  extends UnaryMathExpression((x: Double) => 1 / math.tan(x), "COT") {
+  override def doGenCode(ctx: CodegenContext, ev: ExprCode): ExprCode = {
+    defineCodeGen(ctx, ev, c =>
+      s"""
+        ${ev.value} = 1 / java.lang.Math.tan($c);
+      """
+    )
+  }
+}
+
 @ExpressionDescription(
   usage = "_FUNC_(expr) - Returns the hyperbolic tangent of `expr`.",
   extended = """

sql/core/src/main/scala/org/apache/spark/sql/functions.scala

@@ -1990,6 +1990,14 @@ object functions {
    */
   def tan(columnName: String): Column = tan(Column(columnName))
 
+  /**
+   * Computes the cotangent of the given column.
+   *
+   * @group math_funcs
+   * @since 2.3.0
+   */
+  def cot(e: Column): Column = withExpr { Cot(e.expr) }
+
   /**
    * Computes the hyperbolic tangent of the given value.
    *

sql/core/src/test/resources/sql-tests/inputs/operators.sql

@@ -32,6 +32,7 @@ select 1 - 2;
 select 2 * 5;
 select 5 % 3;
 select pmod(-7, 3);
+select cot(1);
 
 -- check operator precedence.
 -- We follow Oracle operator precedence in the table below that lists the levels of precedence

sql/core/src/test/resources/sql-tests/results/operators.sql.out

@@ -1,5 +1,5 @@
 -- Automatically generated by SQLQueryTestSuite
--- Number of queries: 34
+-- Number of queries: 35
 
 
 -- !query 0
@@ -227,60 +227,68 @@ struct<pmod(-7, 3):int>
 
 
 -- !query 28
-explain select 'a' || 1 + 2
+select cot(1)
 -- !query 28 schema
-struct<plan:string>
+struct<COT(CAST(1 AS DOUBLE)):double>
 -- !query 28 output
-== Physical Plan ==
-*Project [null AS (CAST(concat(a, CAST(1 AS STRING)) AS DOUBLE) + CAST(2 AS DOUBLE))#x]
-+- Scan OneRowRelation[]
+0.6420926159343306
 
 
 -- !query 29
-explain select 1 - 2 || 'b'
+explain select 'a' || 1 + 2
 -- !query 29 schema
 struct<plan:string>
 -- !query 29 output
 == Physical Plan ==
-*Project [-1b AS concat(CAST((1 - 2) AS STRING), b)#x]
+*Project [null AS (CAST(concat(a, CAST(1 AS STRING)) AS DOUBLE) + CAST(2 AS DOUBLE))#x]
 +- Scan OneRowRelation[]
 
 
 -- !query 30
-explain select 2 * 4  + 3 || 'b'
+explain select 1 - 2 || 'b'
 -- !query 30 schema
 struct<plan:string>
 -- !query 30 output
 == Physical Plan ==
-*Project [11b AS concat(CAST(((2 * 4) + 3) AS STRING), b)#x]
+*Project [-1b AS concat(CAST((1 - 2) AS STRING), b)#x]
 +- Scan OneRowRelation[]
 
 
 -- !query 31
-explain select 3 + 1 || 'a' || 4 / 2
+explain select 2 * 4  + 3 || 'b'
 -- !query 31 schema
 struct<plan:string>
 -- !query 31 output
 == Physical Plan ==
-*Project [4a2.0 AS concat(concat(CAST((3 + 1) AS STRING), a), CAST((CAST(4 AS DOUBLE) / CAST(2 AS DOUBLE)) AS STRING))#x]
+*Project [11b AS concat(CAST(((2 * 4) + 3) AS STRING), b)#x]
 +- Scan OneRowRelation[]
 
 
 -- !query 32
-explain select 1 == 1 OR 'a' || 'b' ==  'ab'
+explain select 3 + 1 || 'a' || 4 / 2
 -- !query 32 schema
 struct<plan:string>
 -- !query 32 output
 == Physical Plan ==
-*Project [true AS ((1 = 1) OR (concat(a, b) = ab))#x]
+*Project [4a2.0 AS concat(concat(CAST((3 + 1) AS STRING), a), CAST((CAST(4 AS DOUBLE) / CAST(2 AS DOUBLE)) AS STRING))#x]
 +- Scan OneRowRelation[]
 
 
 -- !query 33
-explain select 'a' || 'c' == 'ac' AND 2 == 3
+explain select 1 == 1 OR 'a' || 'b' ==  'ab'
 -- !query 33 schema
 struct<plan:string>
 -- !query 33 output
 == Physical Plan ==
+*Project [true AS ((1 = 1) OR (concat(a, b) = ab))#x]
++- Scan OneRowRelation[]
+
+
+-- !query 34
+explain select 'a' || 'c' == 'ac' AND 2 == 3
+-- !query 34 schema
+struct<plan:string>
+-- !query 34 output
+== Physical Plan ==
 *Project [false AS ((concat(a, c) = ac) AND (2 = 3))#x]
 +- Scan OneRowRelation[]

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

@@ -274,6 +274,13 @@ class MathFunctionsSuite extends QueryTest with SharedSQLContext {
       Row(1, -1))
   }
 
+  test("cot") {
+    testOneToOneMathFunction(cot, (d: Double) => 1 / math.tan(d))
+    checkAnswer(
+      sql(s"SELECT cot(null), cot(0), cot(-1), cot(${Double.MaxValue})"),
+      Row(null, Double.PositiveInfinity, -0.6420926159343306, -201.53099572900314))
+  }
+
   test("pow / power") {
     testTwoToOneMathFunction(pow, pow, math.pow)