Github user concretevitamin commented on a diff in the pull request:
https://github.com/apache/spark/pull/1359#discussion_r14781542
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/stringOperations.scala
---
@@ -207,3 +210,64 @@ case class StartsWith(left: Expression, right:
Expression) extends StringCompari
case class EndsWith(left: Expression, right: Expression) extends
StringComparison {
def compare(l: String, r: String) = l.endsWith(r)
}
+
+/**
+ * A function that takes a substring of its first argument starting at a
given position.
+ * Defined for String and Binary types.
+ */
+case class Substring(str: Expression, pos: Expression, len: Expression)
extends Expression {
+
+ type EvaluatedType = Any
+
+ def nullable: Boolean = true
+ def dataType: DataType = {
+ if (str.dataType == BinaryType) str.dataType else StringType
--- End diff --
Hey Will -- I think we need to check if `resolved` is true here to not
break Catalyst's contract. Similar to
[here](https://github.com/apache/spark/blob/master/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/predicates.scala#L183).
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