Dandandan commented on code in PR #3884:
URL: https://github.com/apache/arrow-datafusion/pull/3884#discussion_r1004002507
##########
datafusion/expr/src/expr.rs:
##########
@@ -265,6 +265,58 @@ impl BinaryExpr {
pub fn new(left: Box<Expr>, op: Operator, right: Box<Expr>) -> Self {
Self { left, op, right }
}
+
+ /// Get the operator precedence
+ /// use https://www.postgresql.org/docs/7.0/operators.htm#AEN2026 as a
reference
+ pub fn precedence(&self) -> u8 {
+ match self.op {
+ Operator::Or => 5,
+ Operator::And => 10,
+ Operator::Like | Operator::NotLike => 19,
+ Operator::NotEq
+ | Operator::Eq
+ | Operator::Lt
+ | Operator::LtEq
+ | Operator::Gt
+ | Operator::GtEq => 20,
+ Operator::Plus | Operator::Minus => 30,
+ Operator::Multiply | Operator::Divide | Operator::Modulo => 40,
+ _ => 0,
+ }
+ }
+}
+
+impl Display for BinaryExpr {
+ fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
+ // Put parentheses around child binary expressions so that we can see
the difference
+ // between `(a OR b) AND c` and `a OR (b AND c)`. We only insert
parentheses when needed,
+ // based on operator precedence. For example, `(a AND b) OR c` and `a
AND b OR c` are
+ // equivalent and the parentheses are not necessary.
+
+ fn write_child(
+ f: &mut Formatter<'_>,
+ expr: &Expr,
+ precedence: u8,
+ ) -> fmt::Result {
+ match expr {
+ Expr::BinaryExpr(child) => {
+ let p = child.precedence();
+ if p == 0 || p < precedence {
Review Comment:
```suggestion
if p <= precedence {
```
Is the same?
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