docs : Change notes for IntegralDivide (#2054)

Author: coderfender

docs/source/user-guide/expressions.md

@@ -35,14 +35,14 @@ The following Spark expressions are currently available. Any known compatibility
 
 ## Binary Arithmetic
 
-| Expression             | Notes |
-|------------------------| ----- |
-| Add (`+`)              |       |
-| Subtract (`-`)         |       |
-| Multiply (`*`)         |       |
-| Divide (`/`)           |       |
-| IntegralDivide (`div`) |       |
-| Remainder (`%`)        |       |
+| Expression             | Notes                                                                                                                                                                                                                                         |
+|------------------------|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
+| Add (`+`)              |                                                                                                                                                                                                                                               |
+| Subtract (`-`)         |                                                                                                                                                                                                                                               |
+| Multiply (`*`)         |                                                                                                                                                                                                                                               |
+| Divide (`/`)           |                                                                                                                                                                                                                                               |
+| IntegralDivide (`div`) | All operands are cast to DecimalType (in case the input type is not already decima type) with precision 19 and scale 0. Please set `spark.comet.cast.allowIncompatible` to `true` to enable DataFusion’s cast operation for LongType inputs. |
+| Remainder (`%`)        |                                                                                                                                                                                                                                               |
 
 ## Conditional Expressions