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Simplify null division. #3625

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Merged
alamb merged 2 commits into from
Sep 30, 2022
Merged

Simplify null division. #3625

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d39703e
fix
HaoYang670 Sep 27, 2022
f53f114
fix comment
HaoYang670 Sep 29, 2022
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25 changes: 23 additions & 2 deletions datafusion/optimizer/src/simplify_expressions.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -749,12 +749,18 @@ impl<'a, S: SimplifyInfo> ExprRewriter for Simplifier<'a, S> {
op: Divide,
right,
} if is_one(&right) => *left,
// A / null --> null
// null / A --> null
BinaryExpr {
left,
op: Divide,
right: _,
} if is_null(&left) => *left,
// A / null --> null
BinaryExpr {
left: _,
op: Divide,
right,
} if left == right && is_null(&left) => *left,
} if is_null(&right) => *right,
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@alamb alamb Sep 28, 2022

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Isn't this checking for A / null (not null / A as the comments suggest)?
(as in I think the comments are backwards)

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@HaoYang670 HaoYang670 Sep 28, 2022

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Thank you for catching this, I will update.

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@HaoYang670 HaoYang670 Sep 29, 2022

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Done.

// A / A --> 1 (if a is not nullable)
BinaryExpr {
left,
Expand Down Expand Up @@ -979,6 +985,21 @@ mod tests {
assert_eq!(simplify(expr), expected);
}

#[test]
fn test_simplify_divide_null() {
// A / null --> null
let null = Expr::Literal(ScalarValue::Null);
{
let expr = binary_expr(col("c"), Operator::Divide, null.clone());
assert_eq!(simplify(expr), null);
}
// null / A --> null
{
let expr = binary_expr(null.clone(), Operator::Divide, col("c"));
assert_eq!(simplify(expr), null);
}
}

#[test]
fn test_simplify_divide_by_same() {
let expr = binary_expr(col("c2"), Operator::Divide, col("c2"));
Expand Down