[SPARK-29688][SQL] Support average for interval type values

sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/aggregate/Average.scala

@@ -31,6 +31,8 @@ import org.apache.spark.sql.types._
        2.0
       > SELECT _FUNC_(col) FROM VALUES (1), (2), (NULL) AS tab(col);
        1.5
+      > SELECT _FUNC_(cast(v as interval)) FROM VALUES ('-1 weeks'), ('2 seconds'), (null) t(v);
+       -3 days -11 hours -59 minutes -59 seconds
   """,
   since = "1.0.0")
 case class Average(child: Expression) extends DeclarativeAggregate with ImplicitCastInputTypes {
@@ -39,10 +41,7 @@ case class Average(child: Expression) extends DeclarativeAggregate with Implicit
 
   override def children: Seq[Expression] = child :: Nil
 
-  override def inputTypes: Seq[AbstractDataType] = Seq(NumericType)
-
-  override def checkInputDataTypes(): TypeCheckResult =
-    TypeUtils.checkForNumericExpr(child.dataType, "function average")
+  override def inputTypes: Seq[AbstractDataType] = Seq(TypeCollection.NumericAndInterval)
 
   override def nullable: Boolean = true
 
@@ -52,11 +51,13 @@ case class Average(child: Expression) extends DeclarativeAggregate with Implicit
   private lazy val resultType = child.dataType match {
     case DecimalType.Fixed(p, s) =>
       DecimalType.bounded(p + 4, s + 4)
+    case interval: CalendarIntervalType => interval
     case _ => DoubleType
   }
 
   private lazy val sumDataType = child.dataType match {
     case _ @ DecimalType.Fixed(p, s) => DecimalType.bounded(p + 10, s)
+    case interval: CalendarIntervalType => interval
     case _ => DoubleType
   }
 
@@ -66,7 +67,7 @@ case class Average(child: Expression) extends DeclarativeAggregate with Implicit
   override lazy val aggBufferAttributes = sum :: count :: Nil
 
   override lazy val initialValues = Seq(
-    /* sum = */ Literal(0).cast(sumDataType),
+    /* sum = */ Literal.default(sumDataType),
     /* count = */ Literal(0L)
   )
 
@@ -79,6 +80,8 @@ case class Average(child: Expression) extends DeclarativeAggregate with Implicit
   override lazy val evaluateExpression = child.dataType match {
     case _: DecimalType =>
       DecimalPrecision.decimalAndDecimal(sum / count.cast(DecimalType.LongDecimal)).cast(resultType)
+    case CalendarIntervalType =>
+      DivideInterval(sum.cast(resultType), count.cast(DoubleType))
     case _ =>
       sum.cast(resultType) / count.cast(resultType)
   }
@@ -87,7 +90,7 @@ case class Average(child: Expression) extends DeclarativeAggregate with Implicit
     /* sum = */
     Add(
       sum,
-      coalesce(child.cast(sumDataType), Literal(0).cast(sumDataType))),
+      coalesce(child.cast(sumDataType), Literal.default(sumDataType))),
     /* count = */ If(child.isNull, count, count + 1L)
   )
 }

sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/analysis/ExpressionTypeCheckingSuite.scala

@@ -150,7 +150,7 @@ class ExpressionTypeCheckingSuite extends SparkFunSuite {
     assertError(Min('mapField), "min does not support ordering on type")
     assertError(Max('mapField), "max does not support ordering on type")
     assertError(Sum('booleanField), "requires (numeric or interval) type")
-    assertError(Average('booleanField), "function average requires numeric type")
+    assertError(Average('booleanField), "requires (numeric or interval) type")
   }
 
   test("check types for others") {

sql/core/src/test/resources/sql-tests/inputs/group-by.sql

@@ -192,4 +192,36 @@ having sv is not null;
 SELECT
     i,
     Sum(cast(v as interval)) OVER (ORDER BY i ROWS BETWEEN CURRENT ROW AND UNBOUNDED FOLLOWING)
-FROM VALUES(1,'1 seconds'),(1,'2 seconds'),(2,NULL),(2,NULL) t(i,v);
+FROM VALUES(1,'1 seconds'),(1,'2 seconds'),(2,NULL),(2,NULL) t(i,v);
+
+-- average with interval type
+-- null
+select avg(cast(v as interval)) from VALUES (null) t(v);
+
+-- empty set
+select avg(cast(v as interval)) from VALUES ('1 seconds'), ('2 seconds'), (null) t(v) where 1=0;
+
+-- basic interval avg
+select avg(cast(v as interval)) from VALUES ('1 seconds'), ('2 seconds'), (null) t(v);
+select avg(cast(v as interval)) from VALUES ('-1 seconds'), ('2 seconds'), (null) t(v);
+select avg(cast(v as interval)) from VALUES ('-1 seconds'), ('-2 seconds'), (null) t(v);
+select avg(cast(v as interval)) from VALUES ('-1 weeks'), ('2 seconds'), (null) t(v);
+
+-- group by
+select
+    i,
+    avg(cast(v as interval))
+from VALUES (1, '-1 weeks'), (2, '2 seconds'), (3, null), (1, '5 days') t(i, v)
+group by i;
+
+-- having
+select
+    avg(cast(v as interval)) as sv
+from VALUES (1, '-1 weeks'), (2, '2 seconds'), (3, null), (1, '5 days') t(i, v)
+having sv is not null;
+
+-- window
+SELECT
+    i,
+    avg(cast(v as interval)) OVER (ORDER BY i ROWS BETWEEN CURRENT ROW AND UNBOUNDED FOLLOWING)
+FROM VALUES (1,'1 seconds'), (1,'2 seconds'), (2,NULL), (2,NULL) t(i,v);

sql/core/src/test/resources/sql-tests/results/group-by.sql.out

@@ -1,5 +1,5 @@
 -- Automatically generated by SQLQueryTestSuite
--- Number of queries: 65
+-- Number of queries: 74
 
 
 -- !query 0
@@ -660,3 +660,90 @@ struct<i:int,sum(CAST(v AS INTERVAL)) OVER (ORDER BY i ASC NULLS FIRST ROWS BETW
 1	3 seconds
 2	NULL
 2	NULL
+
+
+-- !query 65
+select avg(cast(v as interval)) from VALUES (null) t(v)
+-- !query 65 schema
+struct<avg(CAST(v AS INTERVAL)):interval>
+-- !query 65 output
+NULL
+
+
+-- !query 66
+select avg(cast(v as interval)) from VALUES ('1 seconds'), ('2 seconds'), (null) t(v) where 1=0
+-- !query 66 schema
+struct<avg(CAST(v AS INTERVAL)):interval>
+-- !query 66 output
+NULL
+
+
+-- !query 67
+select avg(cast(v as interval)) from VALUES ('1 seconds'), ('2 seconds'), (null) t(v)
+-- !query 67 schema
+struct<avg(CAST(v AS INTERVAL)):interval>
+-- !query 67 output
+1.5 seconds
+
+
+-- !query 68
+select avg(cast(v as interval)) from VALUES ('-1 seconds'), ('2 seconds'), (null) t(v)
+-- !query 68 schema
+struct<avg(CAST(v AS INTERVAL)):interval>
+-- !query 68 output
+0.5 seconds
+
+
+-- !query 69
+select avg(cast(v as interval)) from VALUES ('-1 seconds'), ('-2 seconds'), (null) t(v)
+-- !query 69 schema
+struct<avg(CAST(v AS INTERVAL)):interval>
+-- !query 69 output
+-1.5 seconds
+
+
+-- !query 70
+select avg(cast(v as interval)) from VALUES ('-1 weeks'), ('2 seconds'), (null) t(v)
+-- !query 70 schema
+struct<avg(CAST(v AS INTERVAL)):interval>
+-- !query 70 output
+-3 days -11 hours -59 minutes -59 seconds
+
+
+-- !query 71
+select
+    i,
+    avg(cast(v as interval))
+from VALUES (1, '-1 weeks'), (2, '2 seconds'), (3, null), (1, '5 days') t(i, v)
+group by i
+-- !query 71 schema
+struct<i:int,avg(CAST(v AS INTERVAL)):interval>
+-- !query 71 output
+1	-1 days
+2	2 seconds
+3	NULL
+
+
+-- !query 72
+select
+    avg(cast(v as interval)) as sv
+from VALUES (1, '-1 weeks'), (2, '2 seconds'), (3, null), (1, '5 days') t(i, v)
+having sv is not null
+-- !query 72 schema
+struct<sv:interval>
+-- !query 72 output
+-15 hours -59 minutes -59.333333 seconds
+
+
+-- !query 73
+SELECT
+    i,
+    avg(cast(v as interval)) OVER (ORDER BY i ROWS BETWEEN CURRENT ROW AND UNBOUNDED FOLLOWING)
+FROM VALUES (1,'1 seconds'), (1,'2 seconds'), (2,NULL), (2,NULL) t(i,v)
+-- !query 73 schema
+struct<i:int,avg(CAST(v AS INTERVAL)) OVER (ORDER BY i ASC NULLS FIRST ROWS BETWEEN CURRENT ROW AND UNBOUNDED FOLLOWING):interval>
+-- !query 73 output
+1	1.5 seconds
+1	2 seconds
+2	NULL
+2	NULL