[SPARK-8748][SQL] Move castability test out from Cast case class into…

… Cast object. This patch moved resolve function in Cast case class into the companion object, and renamed it canCast. We can then use this in the analyzer without a Cast expr.
maropu · Jul 1, 2015 · 4d2d989 · 4d2d989
1 parent ccdb052
commit 4d2d989
Showing 1 changed file with 68 additions and 63 deletions.
diff --git a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/Cast.scala b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/Cast.scala
@@ -27,23 +27,65 @@ import org.apache.spark.sql.catalyst.util.DateTimeUtils
 import org.apache.spark.sql.types._
 import org.apache.spark.unsafe.types.UTF8String
 
-/** Cast the child expression to the target data type. */
-case class Cast(child: Expression, dataType: DataType) extends UnaryExpression with Logging {
 
-  override def checkInputDataTypes(): TypeCheckResult = {
-    if (resolve(child.dataType, dataType)) {
-      TypeCheckResult.TypeCheckSuccess
-    } else {
-      TypeCheckResult.TypeCheckFailure(
-        s"cannot cast ${child.dataType} to $dataType")
-    }
-  }
+object Cast {
 
-  override def foldable: Boolean = child.foldable
+  /**
+   * Returns true iff we can cast `from` type to `to` type.
+   */
+  def canCast(from: DataType, to: DataType): Boolean = (from, to) match {
+    case (fromType, toType) if fromType == toType => true
+
+    case (NullType, _) => true
 
-  override def nullable: Boolean = forceNullable(child.dataType, dataType) || child.nullable
+    case (_, StringType) => true
+
+    case (StringType, BinaryType) => true
+
+    case (StringType, BooleanType) => true
+    case (DateType, BooleanType) => true
+    case (TimestampType, BooleanType) => true
+    case (_: NumericType, BooleanType) => true
+
+    case (StringType, TimestampType) => true
+    case (BooleanType, TimestampType) => true
+    case (DateType, TimestampType) => true
+    case (_: NumericType, TimestampType) => true
+
+    case (_, DateType) => true
 
-  private[this] def forceNullable(from: DataType, to: DataType) = (from, to) match {
+    case (StringType, _: NumericType) => true
+    case (BooleanType, _: NumericType) => true
+    case (DateType, _: NumericType) => true
+    case (TimestampType, _: NumericType) => true
+    case (_: NumericType, _: NumericType) => true
+
+    case (ArrayType(fromType, fn), ArrayType(toType, tn)) =>
+      canCast(fromType, toType) &&
+        resolvableNullability(fn || forceNullable(fromType, toType), tn)
+
+    case (MapType(fromKey, fromValue, fn), MapType(toKey, toValue, tn)) =>
+      canCast(fromKey, toKey) &&
+        (!forceNullable(fromKey, toKey)) &&
+        canCast(fromValue, toValue) &&
+        resolvableNullability(fn || forceNullable(fromValue, toValue), tn)
+
+    case (StructType(fromFields), StructType(toFields)) =>
+      fromFields.length == toFields.length &&
+        fromFields.zip(toFields).forall {
+          case (fromField, toField) =>
+            canCast(fromField.dataType, toField.dataType) &&
+              resolvableNullability(
+                fromField.nullable || forceNullable(fromField.dataType, toField.dataType),
+                toField.nullable)
+        }
+
+    case _ => false
+  }
+
+  private def resolvableNullability(from: Boolean, to: Boolean) = !from || to
+
+  private def forceNullable(from: DataType, to: DataType) = (from, to) match {
     case (StringType, _: NumericType) => true
     case (StringType, TimestampType) => true
     case (DoubleType, TimestampType) => true
@@ -58,61 +100,24 @@ case class Cast(child: Expression, dataType: DataType) extends UnaryExpression w
     case (_, DecimalType.Fixed(_, _)) => true // TODO: not all upcasts here can really give null
     case _ => false
   }
+}
 
-  private[this] def resolvableNullability(from: Boolean, to: Boolean) = !from || to
-
-  private[this] def resolve(from: DataType, to: DataType): Boolean = {
-    (from, to) match {
-      case (from, to) if from == to => true
-
-      case (NullType, _) => true
-
-      case (_, StringType) => true
-
-      case (StringType, BinaryType) => true
-
-      case (StringType, BooleanType) => true
-      case (DateType, BooleanType) => true
-      case (TimestampType, BooleanType) => true
-      case (_: NumericType, BooleanType) => true
-
-      case (StringType, TimestampType) => true
-      case (BooleanType, TimestampType) => true
-      case (DateType, TimestampType) => true
-      case (_: NumericType, TimestampType) => true
-
-      case (_, DateType) => true
-
-      case (StringType, _: NumericType) => true
-      case (BooleanType, _: NumericType) => true
-      case (DateType, _: NumericType) => true
-      case (TimestampType, _: NumericType) => true
-      case (_: NumericType, _: NumericType) => true
-
-      case (ArrayType(from, fn), ArrayType(to, tn)) =>
-        resolve(from, to) &&
-          resolvableNullability(fn || forceNullable(from, to), tn)
-
-      case (MapType(fromKey, fromValue, fn), MapType(toKey, toValue, tn)) =>
-        resolve(fromKey, toKey) &&
-          (!forceNullable(fromKey, toKey)) &&
-          resolve(fromValue, toValue) &&
-          resolvableNullability(fn || forceNullable(fromValue, toValue), tn)
-
-      case (StructType(fromFields), StructType(toFields)) =>
-        fromFields.size == toFields.size &&
-          fromFields.zip(toFields).forall {
-            case (fromField, toField) =>
-              resolve(fromField.dataType, toField.dataType) &&
-                resolvableNullability(
-                  fromField.nullable || forceNullable(fromField.dataType, toField.dataType),
-                  toField.nullable)
-          }
+/** Cast the child expression to the target data type. */
+case class Cast(child: Expression, dataType: DataType) extends UnaryExpression with Logging {
 
-      case _ => false
+  override def checkInputDataTypes(): TypeCheckResult = {
+    if (Cast.canCast(child.dataType, dataType)) {
+      TypeCheckResult.TypeCheckSuccess
+    } else {
+      TypeCheckResult.TypeCheckFailure(
+        s"cannot cast ${child.dataType} to $dataType")
     }
   }
 
+  override def foldable: Boolean = child.foldable
+
+  override def nullable: Boolean = Cast.forceNullable(child.dataType, dataType) || child.nullable
+
   override def toString: String = s"CAST($child, $dataType)"
 
   // [[func]] assumes the input is no longer null because eval already does the null check.