Support timestamp binaryArithmetic string

Author: wangyum

sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/analysis/TypeCoercion.scala

@@ -412,12 +412,17 @@ object TypeCoercion {
       case e if !e.childrenResolved => e
 
       case a @ BinaryArithmetic(left @ StringType(), right)
-        if right.dataType != CalendarIntervalType =>
+        if right.dataType != CalendarIntervalType && right.dataType != TimestampType =>
         a.makeCopy(Array(Cast(left, DoubleType), right))
       case a @ BinaryArithmetic(left, right @ StringType())
-        if left.dataType != CalendarIntervalType =>
+        if left.dataType != CalendarIntervalType && left.dataType != TimestampType =>
         a.makeCopy(Array(left, Cast(right, DoubleType)))
 
+      case a @ BinaryArithmetic(left @ TimestampType(), right @ StringType()) =>
+        a.makeCopy(Array(left, Cast(right, CalendarIntervalType)))
+      case a @ BinaryArithmetic(left @ StringType(), right @ TimestampType()) =>
+        a.makeCopy(Array(Cast(left, CalendarIntervalType), right))
+
       // For equality between string and timestamp we cast the string to a timestamp
       // so that things like rounding of subsecond precision does not affect the comparison.
       case p @ Equality(left @ StringType(), right @ TimestampType()) =>

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

@@ -1576,6 +1576,21 @@ class TypeCoercionSuite extends AnalysisTest {
         SpecifiedWindowFrame(RangeFrame, CurrentRow, UnboundedFollowing))
     )
   }
+
+  test("binary arithmetic with string promotion") {
+    val rule = TypeCoercion.PromoteStrings(conf)
+    val timestamp = Literal(new Timestamp(0L))
+    val intervalStr = Literal("interval 3 month 7 hours")
+    ruleTest(rule,
+      Add(timestamp, intervalStr),
+      Add(timestamp, Cast(intervalStr, CalendarIntervalType)))
+    ruleTest(rule,
+      Add(intervalStr, timestamp),
+      Add(Cast(intervalStr, CalendarIntervalType), timestamp))
+    ruleTest(rule,
+      Subtract(timestamp, intervalStr),
+      Subtract(timestamp, Cast(intervalStr, CalendarIntervalType)))
+  }
 }