[SPARK-8230][SQL] Add array/map size method

Pull Request for: https://issues.apache.org/jira/browse/SPARK-8230

Primary issue resolved is to implement array/map size for Spark SQL. Code is ready for review by a committer. Chen Hao is on the JIRA ticket, but I don't know his username on github, rxin is also on JIRA ticket.

Things to review:
1. Where to put added functions namespace wise, they seem to be part of a few operations on collections which includes `sort_array` and `array_contains`. Hence the name given `collectionOperations.scala` and `_collection_functions` in python.
2. In Python code, should it be in a `1.5.0` function array or in a collections array?
3. Are there any missing methods on the `Size` case class? Looks like many of these functions have generated Java code, is that also needed in this case?
4. Something else?

Author: Pedro Rodriguez <ski.rodriguez@gmail.com>
Author: Pedro Rodriguez <prodriguez@trulia.com>

Closes #7462 from EntilZha/SPARK-8230 and squashes the following commits:

9a442ae [Pedro Rodriguez] fixed functions and sorted __all__
9aea3bb [Pedro Rodriguez] removed imports from python docs
15d4bf1 [Pedro Rodriguez] Added null test case and changed to nullSafeCodeGen
d88247c [Pedro Rodriguez] removed python code
bd5f0e4 [Pedro Rodriguez] removed duplicate function from rebase/merge
59931b4 [Pedro Rodriguez] fixed compile bug instroduced when merging
c187175 [Pedro Rodriguez] updated code to add size to __all__ directly and removed redundent pretty print
130839f [Pedro Rodriguez] fixed failing test
aa9bade [Pedro Rodriguez] fix style
e093473 [Pedro Rodriguez] updated python code with docs, switched classes/traits implemented, added (failing) expression tests
0449377 [Pedro Rodriguez] refactored code to use better abstract classes/traits and implementations
9a1a2ff [Pedro Rodriguez] added unit tests for map size
2bfbcb6 [Pedro Rodriguez] added unit test for size
20df2b4 [Pedro Rodriguez] Finished working version of size function and added it to python
b503e75 [Pedro Rodriguez] First attempt at implementing size for maps and arrays
99a6a5c [Pedro Rodriguez] fixed failing test
cac75ac [Pedro Rodriguez] fix style
933d843 [Pedro Rodriguez] updated python code with docs, switched classes/traits implemented, added (failing) expression tests
42bb7d4 [Pedro Rodriguez] refactored code to use better abstract classes/traits and implementations
f9c3b8a [Pedro Rodriguez] added unit tests for map size
2515d9f [Pedro Rodriguez] added documentation
0e60541 [Pedro Rodriguez] added unit test for size
acf9853 [Pedro Rodriguez] Finished working version of size function and added it to python
84a5d38 [Pedro Rodriguez] First attempt at implementing size for maps and arrays

6 files changed, 152 insertions, 1 deletions

diff --git a/python/pyspark/sql/functions.py b/python/pyspark/sql/functions.py
index 3c134faa0a..719e623a1a 100644
--- a/python/pyspark/sql/functions.py
+++ b/python/pyspark/sql/functions.py
@@ -50,6 +50,7 @@ __all__ = [
     'regexp_replace',
     'sha1',
     'sha2',
+    'size',
     'sparkPartitionId',
     'struct',
     'udf',
@@ -825,6 +826,20 @@ def weekofyear(col):
     return Column(sc._jvm.functions.weekofyear(col))
 
 
+@since(1.5)
+def size(col):
+    """
+    Collection function: returns the length of the array or map stored in the column.
+    :param col: name of column or expression
+
+    >>> df = sqlContext.createDataFrame([([1, 2, 3],),([1],),([],)], ['data'])
+    >>> df.select(size(df.data)).collect()
+    [Row(size(data)=3), Row(size(data)=1), Row(size(data)=0)]
+    """
+    sc = SparkContext._active_spark_context
+    return Column(sc._jvm.functions.size(_to_java_column(col)))
+
+
 class UserDefinedFunction(object):
     """
     User defined function in Python
diff --git a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/analysis/FunctionRegistry.scala b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/analysis/FunctionRegistry.scala
index aec392379c..13523720da 100644
--- a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/analysis/FunctionRegistry.scala
+++ b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/analysis/FunctionRegistry.scala
@@ -195,8 +195,10 @@ object FunctionRegistry {
     expression[Quarter]("quarter"),
     expression[Second]("second"),
     expression[WeekOfYear]("weekofyear"),
-    expression[Year]("year")
+    expression[Year]("year"),
 
+    // collection functions
+    expression[Size]("size")
   )
 
   val builtin: FunctionRegistry = {
diff --git a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/collectionOperations.scala b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/collectionOperations.scala
new file mode 100644
index 0000000000..2d92dcf23a
--- /dev/null
+++ b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/collectionOperations.scala
@@ -0,0 +1,37 @@
+/*
+ * 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.catalyst.expressions
+
+import org.apache.spark.sql.catalyst.expressions.codegen.{CodeGenContext, GeneratedExpressionCode}
+import org.apache.spark.sql.types._
+
+/**
+ * Given an array or map, returns its size.
+ */
+case class Size(child: Expression) extends UnaryExpression with ExpectsInputTypes {
+  override def dataType: DataType = IntegerType
+  override def inputTypes: Seq[AbstractDataType] = Seq(TypeCollection(ArrayType, MapType))
+
+  override def nullSafeEval(value: Any): Int = child.dataType match {
+    case ArrayType(_, _) => value.asInstanceOf[Seq[Any]].size
+    case MapType(_, _, _) => value.asInstanceOf[Map[Any, Any]].size
+  }
+
+  override def genCode(ctx: CodeGenContext, ev: GeneratedExpressionCode): String = {
+    nullSafeCodeGen(ctx, ev, c => s"${ev.primitive} = ($c).size();")
+  }
+}
diff --git a/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/expressions/CollectionFunctionsSuite.scala b/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/expressions/CollectionFunctionsSuite.scala
new file mode 100644
index 0000000000..28c41b5716
--- /dev/null
+++ b/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/expressions/CollectionFunctionsSuite.scala
@@ -0,0 +1,46 @@
+/*
+ * 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.catalyst.expressions
+
+import org.apache.spark.SparkFunSuite
+import org.apache.spark.sql.types._
+
+
+class CollectionFunctionsSuite extends SparkFunSuite with ExpressionEvalHelper {
+
+  test("Array and Map Size") {
+    val a0 = Literal.create(Seq(1, 2, 3), ArrayType(IntegerType))
+    val a1 = Literal.create(Seq[Integer](), ArrayType(IntegerType))
+    val a2 = Literal.create(Seq(1, 2), ArrayType(IntegerType))
+
+    checkEvaluation(Size(a0), 3)
+    checkEvaluation(Size(a1), 0)
+    checkEvaluation(Size(a2), 2)
+
+    val m0 = Literal.create(Map("a" -> "a", "b" -> "b"), MapType(StringType, StringType))
+    val m1 = Literal.create(Map[String, String](), MapType(StringType, StringType))
+    val m2 = Literal.create(Map("a" -> "a"), MapType(StringType, StringType))
+
+    checkEvaluation(Size(m0), 2)
+    checkEvaluation(Size(m1), 0)
+    checkEvaluation(Size(m2), 1)
+
+    checkEvaluation(Literal.create(null, MapType(StringType, StringType)), null)
+    checkEvaluation(Literal.create(null, ArrayType(StringType)), null)
+  }
+}
diff --git a/sql/core/src/main/scala/org/apache/spark/sql/functions.scala b/sql/core/src/main/scala/org/apache/spark/sql/functions.scala
index 6d60dae624..60b089180c 100644
--- a/sql/core/src/main/scala/org/apache/spark/sql/functions.scala
+++ b/sql/core/src/main/scala/org/apache/spark/sql/functions.scala
@@ -42,6 +42,7 @@ import org.apache.spark.util.Utils
  * @groupname misc_funcs Misc functions
  * @groupname window_funcs Window functions
  * @groupname string_funcs String functions
+ * @groupname collection_funcs Collection functions
  * @groupname Ungrouped Support functions for DataFrames.
  * @since 1.3.0
  */
@@ -2054,6 +2055,25 @@ object functions {
   def weekofyear(columnName: String): Column = weekofyear(Column(columnName))
 
   //////////////////////////////////////////////////////////////////////////////////////////////
+  // Collection functions
+  //////////////////////////////////////////////////////////////////////////////////////////////
+
+  /**
+   * Returns length of array or map
+   * @group collection_funcs
+   * @since 1.5.0
+   */
+  def size(columnName: String): Column = size(Column(columnName))
+
+  /**
+   * Returns length of array or map
+   * @group collection_funcs
+   * @since 1.5.0
+   */
+  def size(column: Column): Column = Size(column.expr)
+
+
+  //////////////////////////////////////////////////////////////////////////////////////////////
   //////////////////////////////////////////////////////////////////////////////////////////////
 
   // scalastyle:off
diff --git a/sql/core/src/test/scala/org/apache/spark/sql/DataFrameFunctionsSuite.scala b/sql/core/src/test/scala/org/apache/spark/sql/DataFrameFunctionsSuite.scala
index 8d2ff2f969..1baec5d376 100644
--- a/sql/core/src/test/scala/org/apache/spark/sql/DataFrameFunctionsSuite.scala
+++ b/sql/core/src/test/scala/org/apache/spark/sql/DataFrameFunctionsSuite.scala
@@ -267,4 +267,35 @@ class DataFrameFunctionsSuite extends QueryTest {
     )
   }
 
+  test("array size function") {
+    val df = Seq(
+      (Array[Int](1, 2), "x"),
+      (Array[Int](), "y"),
+      (Array[Int](1, 2, 3), "z")
+    ).toDF("a", "b")
+    checkAnswer(
+      df.select(size("a")),
+      Seq(Row(2), Row(0), Row(3))
+    )
+    checkAnswer(
+      df.selectExpr("size(a)"),
+      Seq(Row(2), Row(0), Row(3))
+    )
+  }
+
+  test("map size function") {
+    val df = Seq(
+      (Map[Int, Int](1 -> 1, 2 -> 2), "x"),
+      (Map[Int, Int](), "y"),
+      (Map[Int, Int](1 -> 1, 2 -> 2, 3 -> 3), "z")
+    ).toDF("a", "b")
+    checkAnswer(
+      df.select(size("a")),
+      Seq(Row(2), Row(0), Row(3))
+    )
+    checkAnswer(
+      df.selectExpr("size(a)"),
+      Seq(Row(2), Row(0), Row(3))
+    )
+  }
 }