Github user ueshin commented on a diff in the pull request:
https://github.com/apache/spark/pull/1359#discussion_r14915562
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/stringOperations.scala
---
@@ -205,3 +207,72 @@ case class EndsWith(left: Expression, right:
Expression)
extends BinaryExpression with 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
--- End diff --
`nullable` could be `str.nullable || pos.nullable || len.nullable` ?
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