[SPARK-8944][SQL] Support casting between IntervalType and StringType

Author: Wenchen Fan <cloud0fan@outlook.com>

Closes #7355 from cloud-fan/fromString and squashes the following commits:

3bbb9d6 [Wenchen Fan] fix code gen
7dab957 [Wenchen Fan] naming fix
0fbbe19 [Wenchen Fan] address comments
ac1f3d1 [Wenchen Fan] Support casting between IntervalType and StringType

2 files changed, 26 insertions, 1 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
index 7f2383dedc..ab02addfb4 100644
--- 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
@@ -26,7 +26,7 @@ import org.apache.spark.sql.catalyst.analysis.TypeCheckResult
 import org.apache.spark.sql.catalyst.expressions.codegen.{CodeGenContext, GeneratedExpressionCode}
 import org.apache.spark.sql.catalyst.util.DateTimeUtils
 import org.apache.spark.sql.types._
-import org.apache.spark.unsafe.types.UTF8String
+import org.apache.spark.unsafe.types.{Interval, UTF8String}
 
 
 object Cast {
@@ -55,6 +55,9 @@ object Cast {
 
     case (_, DateType) => true
 
+    case (StringType, IntervalType) => true
+    case (IntervalType, StringType) => true
+
     case (StringType, _: NumericType) => true
     case (BooleanType, _: NumericType) => true
     case (DateType, _: NumericType) => true
@@ -232,6 +235,13 @@ case class Cast(child: Expression, dataType: DataType) extends UnaryExpression w
     case _ => _ => null
   }
 
+  // IntervalConverter
+  private[this] def castToInterval(from: DataType): Any => Any = from match {
+    case StringType =>
+      buildCast[UTF8String](_, s => Interval.fromString(s.toString))
+    case _ => _ => null
+  }
+
   // LongConverter
   private[this] def castToLong(from: DataType): Any => Any = from match {
     case StringType =>
@@ -405,6 +415,7 @@ case class Cast(child: Expression, dataType: DataType) extends UnaryExpression w
     case DateType => castToDate(from)
     case decimal: DecimalType => castToDecimal(from, decimal)
     case TimestampType => castToTimestamp(from)
+    case IntervalType => castToInterval(from)
     case BooleanType => castToBoolean(from)
     case ByteType => castToByte(from)
     case ShortType => castToShort(from)
@@ -442,6 +453,10 @@ case class Cast(child: Expression, dataType: DataType) extends UnaryExpression w
       case (_, StringType) =>
         defineCodeGen(ctx, ev, c => s"${ctx.stringType}.fromString(String.valueOf($c))")
 
+      case (StringType, IntervalType) =>
+        defineCodeGen(ctx, ev, c =>
+          s"org.apache.spark.unsafe.types.Interval.fromString($c.toString())")
+
       // fallback for DecimalType, this must be before other numeric types
       case (_, dt: DecimalType) =>
         super.genCode(ctx, ev)
diff --git a/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/expressions/CastSuite.scala b/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/expressions/CastSuite.scala
index 919fdd470b..1de161c367 100644
--- a/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/expressions/CastSuite.scala
+++ b/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/expressions/CastSuite.scala
@@ -563,4 +563,14 @@ class CastSuite extends SparkFunSuite with ExpressionEvalHelper {
       InternalRow(0L)))
   }
 
+  test("case between string and interval") {
+    import org.apache.spark.unsafe.types.Interval
+
+    checkEvaluation(Cast(Literal("interval -3 month 7 hours"), IntervalType),
+      new Interval(-3, 7 * Interval.MICROS_PER_HOUR))
+    checkEvaluation(Cast(Literal.create(
+      new Interval(15, -3 * Interval.MICROS_PER_DAY), IntervalType), StringType),
+      "interval 1 years 3 months -3 days")
+  }
+
 }