Github user davies commented on a diff in the pull request:
https://github.com/apache/spark/pull/4332#discussion_r23991126
--- Diff: sql/core/src/main/scala/org/apache/spark/sql/Dsl.scala ---
@@ -100,27 +91,82 @@ object Dsl {
Column(literalExpr)
}
+
//////////////////////////////////////////////////////////////////////////////////////////////
+
//////////////////////////////////////////////////////////////////////////////////////////////
+
+ /** Aggregate function: returns the sum of all values in the expression.
*/
def sum(e: Column): Column = Sum(e.expr)
+
+ /** Aggregate function: returns the sum of distinct values in the
expression. */
def sumDistinct(e: Column): Column = SumDistinct(e.expr)
+
+ /** Aggregate function: returns the number of items in a group. */
def count(e: Column): Column = Count(e.expr)
+ /** Aggregate function: returns the number of distinct items in a group.
*/
@scala.annotation.varargs
def countDistinct(expr: Column, exprs: Column*): Column =
CountDistinct((expr +: exprs).map(_.expr))
+ /** Aggregate function: returns the approximate number of distinct items
in a group. */
def approxCountDistinct(e: Column): Column = ApproxCountDistinct(e.expr)
- def approxCountDistinct(e: Column, rsd: Double): Column =
- ApproxCountDistinct(e.expr, rsd)
+ /** Aggregate function: returns the approximate number of distinct items
in a group. */
+ def approxCountDistinct(e: Column, rsd: Double): Column =
ApproxCountDistinct(e.expr, rsd)
+
+ /** Aggregate function: returns the average of the values in a group. */
def avg(e: Column): Column = Average(e.expr)
+
+ /** Aggregate function: returns the first value in a group. */
def first(e: Column): Column = First(e.expr)
+
+ /** Aggregate function: returns the last value in a group. */
def last(e: Column): Column = Last(e.expr)
+
+ /** Aggregate function: returns the minimum value of the expression in a
group. */
def min(e: Column): Column = Min(e.expr)
+
+ /** Aggregate function: returns the maximum value of the expression in a
group. */
def max(e: Column): Column = Max(e.expr)
+
//////////////////////////////////////////////////////////////////////////////////////////////
+
//////////////////////////////////////////////////////////////////////////////////////////////
+
+ /**
+ * Unary minus, i.e. negate the expression.
+ * {{{
+ * // Select the amount column and negates all values.
+ * // Scala:
+ * df.select( -df("amount") )
+ *
+ * // Java:
+ * df.select( negate(df.col("amount")) );
+ * }}}
+ */
+ def negate(e: Column): Column = -e
--- End diff --
negative or neg?
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