[SPARK-8753][SQL] Create an IntervalType data type

We need a new data type to represent time intervals. Because we can't determine how many days in a month, so we need 2 values for interval: a int `months`, a long `microseconds`.

The interval literal syntax looks like:
`interval 3 years -4 month 4 weeks 3 second`

Because we use number of 100ns as value of `TimestampType`, so it may not makes sense to support nano second unit.

Author: Wenchen Fan <cloud0fan@outlook.com>

Closes #7226 from cloud-fan/interval and squashes the following commits:

632062d [Wenchen Fan] address comments
ac348c3 [Wenchen Fan] use case class
0342d2e [Wenchen Fan] use array byte
df9256c [Wenchen Fan] fix style
fd6f18a [Wenchen Fan] address comments
1856af3 [Wenchen Fan] support interval type

1 files changed, 5 insertions, 0 deletions

diff --git a/sql/catalyst/src/main/java/org/apache/spark/sql/types/DataTypes.java b/sql/catalyst/src/main/java/org/apache/spark/sql/types/DataTypes.java
index e457542c64..d22ad6794d 100644
--- a/sql/catalyst/src/main/java/org/apache/spark/sql/types/DataTypes.java
+++ b/sql/catalyst/src/main/java/org/apache/spark/sql/types/DataTypes.java
@@ -50,6 +50,11 @@ public class DataTypes {
   public static final DataType TimestampType = TimestampType$.MODULE$;
 
   /**
+   * Gets the IntervalType object.
+   */
+  public static final DataType IntervalType = IntervalType$.MODULE$;
+
+  /**
    * Gets the DoubleType object.
    */
   public static final DataType DoubleType = DoubleType$.MODULE$;