Github user wuchong commented on a diff in the pull request:
https://github.com/apache/flink/pull/4274#discussion_r126870614
--- Diff:
flink-libraries/flink-table/src/main/scala/org/apache/flink/table/api/scala/expressionDsl.scala
---
@@ -982,4 +982,27 @@ object randInteger {
}
}
+/**
+ * Returns the string that results from concatenating the arguments.
+ * Returns NULL if any argument is NULL.
+ */
+object concat {
+ def apply(strings: Expression*): Expression = {
+ new Concat(strings)
+ }
+}
+
+/**
+ * Returns the string that results from concatenating the arguments and
separator.
+ * Returns NULL If the separator is NULL.
+ *
+ * Note: this user-defined function does not skip empty strings. However,
it does skip any NULL
+ * values after the separator argument.
+ **/
+object concat_ws {
+ def apply(separator: Expression, strings: Expression*): Expression = {
--- End diff --
I would suggest to change this signature to `apply(separator: Expression,
first: Expression, second: Expression, rest: Expression*)` to avoid misusage
such as `concat_ws(",")`.
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