Github user wuchong commented on a diff in the pull request:
https://github.com/apache/flink/pull/4274#discussion_r126881444
--- Diff:
flink-libraries/flink-table/src/main/scala/org/apache/flink/table/expressions/stringExpressions.scala
---
@@ -277,3 +278,47 @@ case class Overlay(
position.toRexNode)
}
}
+
+/**
+ * Returns the string that results from concatenating the arguments.
+ * Returns NULL if any argument is NULL.
+ */
+case class Concat(strings: Seq[Expression]) extends Expression with
InputTypeSpec {
+
+ override private[flink] def children: Seq[Expression] = strings
+
+ override private[flink] def resultType: TypeInformation[_] =
BasicTypeInfo.STRING_TYPE_INFO
+
+ override private[flink] def expectedTypes: Seq[TypeInformation[_]] =
STRING_TYPE_INFO :: Nil
--- End diff --
The `expectedTypes` should be the same size as children with
`STRING_TYPE_INFO`.
All the tests passed, because there is a bug in
`InputTypeSpec#validateInput` which do not check the size of `expectedTypes`
and `children`. It would be great if we can fix it in this PR.
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