mingmwang commented on PR #5111:
URL:
https://github.com/apache/arrow-datafusion/pull/5111#issuecomment-1407947251
Should move the calculation logic to the `UnionExec`'s constructor ? Since
`maintains_input_order()` will be invoked multiple times during the
optimization process.
```rust
fn maintains_input_order(&self) -> Vec<bool> {
// If the Union has an output ordering, it maintains at least one
// child's ordering (i.e. the meet).
// For instance, assume that the first child is
SortExpr('a','b','c'),
// the second child is SortExpr('a','b') and the third child is
// SortExpr('a','b'). The output ordering would be SortExpr('a','b'),
// which is the "meet" of all input orderings. In this example, this
// function will return vec![false, true, true], indicating that we
// preserve the orderings for the 2nd and the 3rd children.
self.inputs()
.iter()
.map(|child| {
ordering_satisfy(self.output_ordering(),
child.output_ordering(), || {
child.equivalence_properties()
})
})
.collect()
}
```
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