Github user rxin commented on a diff in the pull request:
https://github.com/apache/spark/pull/7151#discussion_r33702376
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/Expression.scala
---
@@ -266,16 +266,37 @@ abstract class UnaryExpression extends Expression
with trees.UnaryNode[Expressio
}
/**
+ * An trait that gets mixin to define the expected input types of an
expression.
+ */
+trait ExpectsInputTypes { self: Expression =>
+
+ /**
+ * Expected input types from child expressions. The i-th position in the
returned seq indicates
+ * the type requirement for the i-th child.
+ *
+ * The possible values at each position are:
+ * 1. a specific data type, e.g. LongType, StringType.
+ * 2. a non-leaf data type, e.g. NumericType, IntegralType,
FractionalType.
+ * 3. a list of specific data types, e.g. Seq(StringType, BinaryType).
+ */
+ def inputTypes: Seq[Any]
+
+ override def checkInputDataTypes(): TypeCheckResult = {
+ // We will do the type checking in `HiveTypeCoercion`, so always
returning success here.
+ TypeCheckResult.TypeCheckSuccess
+ }
+}
+
+/**
* Expressions that require a specific `DataType` as input should
implement this trait
* so that the proper type conversions can be performed in the analyzer.
*/
-trait AutoCastInputTypes {
- self: Expression =>
+trait AutoCastInputTypes { self: Expression =>
- def expectedChildTypes: Seq[DataType]
+ def inputTypes: Seq[DataType]
override def checkInputDataTypes(): TypeCheckResult = {
--- End diff --
that doesn't make sense here until we implement all expressions
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