cloud-fan commented on a change in pull request #28420:
URL: https://github.com/apache/spark/pull/28420#discussion_r420659008
##########
File path:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/Expression.scala
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@@ -323,6 +324,18 @@ trait RuntimeReplaceable extends UnaryExpression with
Unevaluable {
// two `RuntimeReplaceable` are considered to be semantically equal if their
"child" expressions
// are semantically equal.
override lazy val canonicalized: Expression = child.canonicalized
+
+ /**
+ * Only used to generate SQL representation of this expression.
+ *
+ * Implementations should override this with original parameters
+ */
+ protected def exprsReplaced: Seq[Expression]
+
+ override def sql: String = prettyName +
exprsReplaced.map(_.sql).mkString("(", ", ", ")")
Review comment:
another idea: maybe we can define a `mkString` method?
```
def exprsReplaced: Seq[Expression]
def mkString(childrenString: Seq[String]): String =
childrenString.mkString("(", ", ", ")")
override def sql: String = prettyName + mkString(exprsReplaced.map(_.sql))
```
then in `util`
```
case r: RuntimeReplaceable =>
PrettyAttribute(r.mkString(r.exprsReplaced.map(toPrettySQL)), r.dataType)
```
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