alamb commented on code in PR #3669:
URL: https://github.com/apache/arrow-datafusion/pull/3669#discussion_r985226627
##########
datafusion/optimizer/src/simplify_expressions.rs:
##########
@@ -790,6 +791,37 @@ impl<'a, S: SimplifyInfo> ExprRewriter for Simplifier<'a,
S> {
right,
} if !info.nullable(&left)? && left == right => lit(1),
+ //
+ // Rules for Modulo
+ //
+
+ // A % null --> null
+ BinaryExpr {
+ left: _,
+ op: Modulo,
+ right,
+ } if is_null(&right) => *right,
+ // null % A --> null
+ BinaryExpr {
+ left,
+ op: Modulo,
+ right: _,
+ } if is_null(&left) => *left,
+ // A % 1 --> 0
+ BinaryExpr {
+ left,
+ op: Modulo,
+ right,
+ } if !info.nullable(&left)? && is_one(&right) => lit(0),
+ // A % 0 --> DivideByZero Error
+ BinaryExpr {
+ left,
+ op: Modulo,
+ right,
+ } if !info.nullable(&left)? && is_zero(&right) => {
+ return
Err(DataFusionError::ArrowError(ArrowError::DivideByZero))
Review Comment:
I suggest not erroring in this case. It might end up causing a an expression
like
```sql
select
CASE
WHEN 0 = 0 THEN 5
WHEN 0 != 0 THEN 5 % 0
END
...
```
In other words, it could generate an error that would not ever actually be
evaluated at runtime
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