Omega359 commented on code in PR #19460:
URL: https://github.com/apache/datafusion/pull/19460#discussion_r2645974786


##########
datafusion/optimizer/src/analyzer/type_coercion.rs:
##########
@@ -290,17 +291,214 @@ impl<'a> TypeCoercionRewriter<'a> {
         right: Expr,
         right_schema: &DFSchema,
     ) -> Result<(Expr, Expr)> {
-        let (left_type, right_type) = BinaryTypeCoercer::new(
-            &left.get_type(left_schema)?,
+        let left_data_type = left.get_type(left_schema)?;
+        let right_data_type = right.get_type(right_schema)?;
+        let (left_type, right_type) =
+            BinaryTypeCoercer::new(&left_data_type, &op, &right_data_type)
+                .get_input_types()?;
+        let left_cast_ok = can_cast_types(&left_data_type, &left_type);
+        let right_cast_ok = can_cast_types(&right_data_type, &right_type);
+
+        // handle special cases for
+        // * Date +/- int => Date
+        // * Date + time => Timestamp
+        let left_expr = if !left_cast_ok {
+            Self::coerce_date_time_math_op(
+                left,
+                &op,
+                &left_data_type,
+                &left_type,
+                &right_type,
+            )?
+        } else {
+            left.cast_to(&left_type, left_schema)?
+        };
+
+        let right_expr = if !right_cast_ok {
+            Self::coerce_date_time_math_op(
+                right,
+                &op,
+                &right_data_type,
+                &right_type,
+                &left_type,
+            )?
+        } else {
+            right.cast_to(&right_type, right_schema)?
+        };
+
+        Ok((left_expr, right_expr))
+    }
+
+    fn coerce_date_time_math_op(
+        expr: Expr,
+        op: &Operator,
+        left_current_type: &DataType,
+        left_target_type: &DataType,
+        right_target_type: &DataType,
+    ) -> Result<Expr, DataFusionError> {
+        use DataType::*;
+
+        let e = match (
             &op,
-            &right.get_type(right_schema)?,
-        )
-        .get_input_types()?;
+            &left_current_type,
+            &left_target_type,
+            &right_target_type,
+        ) {
+            // int +/- date => date
+            (
+                Operator::Plus | Operator::Minus,
+                Int8 | Int16 | Int32 | Int64 | UInt8 | UInt16 | UInt32 | 
UInt64,
+                Interval(IntervalUnit::MonthDayNano),
+                Date32 | Date64,
+            ) => {
+                // cast to i64 first
+                let expr = if *left_current_type == Int64 {
+                    expr
+                } else {
+                    Expr::Cast(Cast::new(Box::new(expr), Int64))
+                };
+                // next, multiply by 86400 to get seconds
+                let expr = Expr::BinaryExpr(BinaryExpr::new(
+                    Box::new(expr),
+                    Operator::Multiply,
+                    Box::new(Expr::Literal(
+                        ScalarValue::Int64(Some(SECONDS_IN_DAY)),
+                        None,
+                    )),
+                ));
+                // cast to duration
+                let expr =
+                    Expr::Cast(Cast::new(Box::new(expr), 
Duration(TimeUnit::Second)));
+
+                // finally cast to interval
+                Expr::Cast(Cast::new(
+                    Box::new(expr),
+                    Interval(IntervalUnit::MonthDayNano),
+                ))
+            }
+            // These might seem to be a bit convoluted, however for arrow to 
do date + time arithmetic

Review Comment:
   date + time -> timestamp 
   time +/- time -> time
   
   Those are the two that make sense to me to push down into arrow



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