From d2340f8e1c342354e1a67d468b35e86e3496ccf9 Mon Sep 17 00:00:00 2001
From: Max Gekk <max.gekk@gmail.com>
Date: Tue, 21 Sep 2021 10:20:16 +0300
Subject: [PATCH] [SPARK-36807][SQL] Merge ANSI interval types to a tightest
 common type

### What changes were proposed in this pull request?
In the PR, I propose to modify `StructType` to support merging of ANSI interval types with different fields.

### Why are the changes needed?
This will allow merging of schemas from different datasource files.

### Does this PR introduce _any_ user-facing change?
No, the ANSI interval types haven't released yet.

### How was this patch tested?
Added new test to `StructTypeSuite`.

Closes #34049 from MaxGekk/merge-ansi-interval-types.

Authored-by: Max Gekk <max.gekk@gmail.com>
Signed-off-by: Max Gekk <max.gekk@gmail.com>
---
 .../apache/spark/sql/types/StructType.scala   |  6 +++++
 .../spark/sql/types/StructTypeSuite.scala     | 23 +++++++++++++++++++
 2 files changed, 29 insertions(+)

diff --git a/sql/catalyst/src/main/scala/org/apache/spark/sql/types/StructType.scala b/sql/catalyst/src/main/scala/org/apache/spark/sql/types/StructType.scala
index 83ee1913da..c9862cb629 100644
--- a/sql/catalyst/src/main/scala/org/apache/spark/sql/types/StructType.scala
+++ b/sql/catalyst/src/main/scala/org/apache/spark/sql/types/StructType.scala
@@ -653,6 +653,12 @@ object StructType extends AbstractDataType {
       case (leftUdt: UserDefinedType[_], rightUdt: UserDefinedType[_])
         if leftUdt.userClass == rightUdt.userClass => leftUdt
 
+      case (YearMonthIntervalType(lstart, lend), YearMonthIntervalType(rstart, rend)) =>
+        YearMonthIntervalType(Math.min(lstart, rstart).toByte, Math.max(lend, rend).toByte)
+
+      case (DayTimeIntervalType(lstart, lend), DayTimeIntervalType(rstart, rend)) =>
+        DayTimeIntervalType(Math.min(lstart, rstart).toByte, Math.max(lend, rend).toByte)
+
       case (leftType, rightType) if leftType == rightType =>
         leftType
 
diff --git a/sql/catalyst/src/test/scala/org/apache/spark/sql/types/StructTypeSuite.scala b/sql/catalyst/src/test/scala/org/apache/spark/sql/types/StructTypeSuite.scala
index 8db3831392..8cc04c78d8 100644
--- a/sql/catalyst/src/test/scala/org/apache/spark/sql/types/StructTypeSuite.scala
+++ b/sql/catalyst/src/test/scala/org/apache/spark/sql/types/StructTypeSuite.scala
@@ -25,7 +25,9 @@ import org.apache.spark.sql.catalyst.plans.SQLHelper
 import org.apache.spark.sql.internal.SQLConf
 import org.apache.spark.sql.types.{DayTimeIntervalType => DT}
 import org.apache.spark.sql.types.{YearMonthIntervalType => YM}
+import org.apache.spark.sql.types.DayTimeIntervalType._
 import org.apache.spark.sql.types.StructType.fromDDL
+import org.apache.spark.sql.types.YearMonthIntervalType._
 
 class StructTypeSuite extends SparkFunSuite with SQLHelper {
 
@@ -382,4 +384,25 @@ class StructTypeSuite extends SparkFunSuite with SQLHelper {
     assert(e.getMessage.contains(
       "Field name a2.element.C.name is invalid: a2.element.c is not a struct"))
   }
+
+  test("SPARK-36807: Merge ANSI interval types to a tightest common type") {
+    Seq(
+      (YM(YEAR), YM(YEAR)) -> YM(YEAR),
+      (YM(YEAR), YM(MONTH)) -> YM(YEAR, MONTH),
+      (YM(MONTH), YM(MONTH)) -> YM(MONTH),
+      (YM(YEAR, MONTH), YM(YEAR)) -> YM(YEAR, MONTH),
+      (YM(YEAR, MONTH), YM(YEAR, MONTH)) -> YM(YEAR, MONTH),
+      (DT(DAY), DT(DAY)) -> DT(DAY),
+      (DT(SECOND), DT(SECOND)) -> DT(SECOND),
+      (DT(DAY), DT(SECOND)) -> DT(DAY, SECOND),
+      (DT(HOUR, SECOND), DT(DAY, MINUTE)) -> DT(DAY, SECOND),
+      (DT(HOUR, MINUTE), DT(DAY, SECOND)) -> DT(DAY, SECOND)
+    ).foreach { case ((i1, i2), expected) =>
+      val st1 = new StructType().add("interval", i1)
+      val st2 = new StructType().add("interval", i2)
+      val expectedStruct = new StructType().add("interval", expected)
+      assert(st1.merge(st2) === expectedStruct)
+      assert(st2.merge(st1) === expectedStruct)
+    }
+  }
 }