Github user willb commented on a diff in the pull request:
https://github.com/apache/spark/pull/1359#discussion_r14783468
--- 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
+ }
+
+ def references = children.flatMap(_.references).toSet
+
+ override def children = str :: pos :: len :: Nil
+
+ def slice[T, C <% IndexedSeqOptimized[T,_]](str: C, startPos: Int,
sliceLen: Int): Any = {
+ val len = str.length
+ // Hive and SQL use one-based indexing for SUBSTR arguments but also
accept zero and
--- End diff --
Hive supports 0-based indexing in the same way as this patch. I agree that
supporting both in this way is ugly (both from an interface and from an
implementation perspective), but it seems likely that people are depending on
this behavior in the wild, doesn't it?
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