gengliangwang commented on a change in pull request #25300: [SPARK-28503][SQL] 
Return null result on cast an out-of-range value to a integral type
URL: https://github.com/apache/spark/pull/25300#discussion_r309043580
 
 

 ##########
 File path: 
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/Cast.scala
 ##########
 @@ -456,9 +474,52 @@ case class Cast(child: Expression, dataType: DataType, 
timeZoneId: Option[String
     case DateType =>
       buildCast[Int](_, d => null)
     case TimestampType =>
-      buildCast[Long](_, t => timestampToLong(t).toInt)
-    case x: NumericType =>
-      b => x.numeric.asInstanceOf[Numeric[Any]].toInt(b)
+      buildCast[Long](_, t => {
+        val longValue = timestampToLong(t)
+        if (longValue == longValue.toInt) {
+          longValue.toInt
+        } else {
+          null
+        }
+      })
+    case ByteType =>
+      b => b.asInstanceOf[Byte].toInt
+    case ShortType =>
+      b => b.asInstanceOf[Short].toInt
+    case LongType =>
+      buildCast[Long](_, l =>
+        if (l == l.toInt) {
+          l.toInt
+        } else {
+          null
+        }
+      )
+    case x: FloatType =>
+      buildCast[Float](_, f =>
+        if (f <= Int.MaxValue && f >= Int.MinValue) {
+          f.toInt
 
 Review comment:
   Actually it is tricty to compare float and int if the float value is around 
Int.MaxValue or Int.MinValue.
   ```
   scala> BigDecimal((Int.MaxValue + 1L).toString).toFloat <= Int.MaxValue
   res1: Boolean = true
   ```
   This is because `float` is also 32 bits long, and it uses 8 bit to represent 
the exponent field. While `int` is 32 bits long. So the comparison won't be 
accurate.

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