EnricoMi commented on code in PR #36150:
URL: https://github.com/apache/spark/pull/36150#discussion_r921053543
##########
sql/core/src/main/scala/org/apache/spark/sql/Dataset.scala:
##########
@@ -2012,7 +2012,97 @@ class Dataset[T] private[sql](
@scala.annotation.varargs
def agg(expr: Column, exprs: Column*): DataFrame = groupBy().agg(expr, exprs
: _*)
- /**
+ /**
+ * Unpivot a DataFrame from wide format to long format, optionally
+ * leaving identifier columns set.
+ *
+ * This function is useful to massage a DataFrame into a format where some
+ * columns are identifier columns ("ids"), while all other columns ("values")
+ * are "unpivoted" to the rows, leaving just two non-id columns, named as
given
+ * by `variableColumnName` and `valueColumnName`.
+ *
+ * {{{
+ * val df = Seq((1, 11, 12L), (2, 21, 22L)).toDF("id", "int", "long")
+ * df.show()
+ * // output:
+ * // +---+---+----+
+ * // | id|int|long|
+ * // +---+---+----+
+ * // | 1| 11| 12|
+ * // | 2| 21| 22|
+ * // +---+---+----+
+ *
+ * df.melt(Array($"id"), Array($"int", $"long"), "variable",
"value").show()
+ * // output:
+ * // +---+--------+-----+
+ * // | id|variable|value|
+ * // +---+--------+-----+
+ * // | 1| int| 11|
+ * // | 1| long| 12|
+ * // | 2| int| 21|
+ * // | 2| long| 22|
+ * // +---+--------+-----+
+ * // schema:
+ * //root
+ * // |-- id: integer (nullable = false)
+ * // |-- variable: string (nullable = false)
+ * // |-- value: long (nullable = true)
+ * }}}
+ *
+ * When no "id" columns are given, the unpivoted DataFrame consists of only
the
+ * "variable" and "value" columns.
+ *
+ * All "value" columns must be of compatible data type. If they are not the
same data type,
+ * all "value" columns are cast to the nearest common data type. For
instance,
+ * types `IntegerType` and `LongType` are compatible and cast to `LongType`,
+ * while `IntegerType` and `StringType` are not compatible and `melt` fails.
+ *
+ * @param ids Id columns
+ * @param values Value columns to melt
+ * @param variableColumnName Name of the variable column
+ * @param valueColumnName Name of the value column
+ *
+ * @group untypedrel
+ * @since 3.4.0
+ */
+ def melt(
Review Comment:
answered in https://github.com/apache/spark/pull/36150/files#r919685963 with
yes
--
This is an automated message from the Apache Git Service.
To respond to the message, please log on to GitHub and use the
URL above to go to the specific comment.
To unsubscribe, e-mail: [email protected]
For queries about this service, please contact Infrastructure at:
[email protected]
---------------------------------------------------------------------
To unsubscribe, e-mail: [email protected]
For additional commands, e-mail: [email protected]
