gabotechs commented on code in PR #16031:
URL: https://github.com/apache/datafusion/pull/16031#discussion_r2084556175
##########
datafusion/substrait/src/logical_plan/consumer/expr/scalar_function.rs:
##########
@@ -124,6 +109,31 @@ pub fn name_to_op(name: &str) -> Option<Operator> {
}
}
+/// Build a balanced tree of binary operations from a binary operator and a
list of arguments.
+///
+/// For example, `OR` `(a, b, c, d, e)` will be converted to: `OR(OR(a, OR(b,
c)), OR(d, e))`.
+///
+/// `args` must not be empty.
+fn arg_list_to_binary_op_tree(
+ op: Operator,
+ args: &[Expr],
+) -> Expr {
+ if args.len() == 1 {
+ return args[0].clone();
+ } else if args.len() == 0 {
+ panic!("must not be called with empty args");
+ }
+ // Cut argument list in 2 balanced parts
+ let mid_idx = args.len() / 2;
+ let left = arg_list_to_binary_op_tree(op, &args[0..mid_idx]);
+ let right = arg_list_to_binary_op_tree(op, &args[mid_idx..]);
+ Expr::BinaryExpr(BinaryExpr {
+ left: Box::new(left),
+ op,
+ right: Box::new(right),
+ })
+}
Review Comment:
Nice! do you think we can do it without cloning the expressions? something
like:
```rust
fn arg_list_to_binary_op_tree(op: Operator, mut args: Vec<Expr>) -> Expr {
if args.is_empty() {
panic!("must not be called with empty args");
}
if args.len() == 1 {
return args.into_iter().next().unwrap();
}
// Cut argument list in 2 balanced parts
let mid_idx = args.len() / 2;
let right = arg_list_to_binary_op_tree(op, args.split_off(mid_idx));
let left = arg_list_to_binary_op_tree(op, args);
Expr::BinaryExpr(BinaryExpr {
left: Box::new(left),
op,
right: Box::new(right),
})
}
```
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