[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, 47 insertions, 0 deletions

diff --git a/unsafe/src/main/java/org/apache/spark/unsafe/types/Interval.java b/unsafe/src/main/java/org/apache/spark/unsafe/types/Interval.java
new file mode 100644
index 0000000000..3eb67ede06
--- /dev/null
+++ b/unsafe/src/main/java/org/apache/spark/unsafe/types/Interval.java
@@ -0,0 +1,47 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.spark.unsafe.types;
+
+import java.io.Serializable;
+
+/**
+ * The internal representation of interval type.
+ */
+public final class Interval implements Serializable {
+  public final int months;
+  public final long microseconds;
+
+  public Interval(int months, long microseconds) {
+    this.months = months;
+    this.microseconds = microseconds;
+  }
+
+  @Override
+  public boolean equals(Object other) {
+    if (this == other) return true;
+    if (other == null || !(other instanceof Interval)) return false;
+
+    Interval o = (Interval) other;
+    return this.months == o.months && this.microseconds == o.microseconds;
+  }
+
+  @Override
+  public int hashCode() {
+    return 31 * months + (int) microseconds;
+  }
+}