Acfboy opened a new pull request, #20545:
URL: https://github.com/apache/datafusion/pull/20545
## Which issue does this PR close?
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- Closes #18816 .
## Rationale for this change
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In `UserDefinedLogicalNodeCore`, the default implementation of
`necessary_children_exprs ` returns `None`, which signals to the optimizer that
it cannot determine which columns are required from the child.
The optimizer takes a conservative approach and skips projection pruning for
that node, leading to complex and redundant plans in the subtree. However, it
would make more sense to assume all columns are required and let the optimizer
proceed, rather than giving up on the entire subtree entirely.
## What changes are included in this PR?
```rust
LogicalPlan::Extension(extension) => {
if let Some(necessary_children_indices) =
extension.node.necessary_children_exprs(indices.indices())
{
...
} else {
// Requirements from parent cannot be routed down to user defined
logical plan safely
// Assume it requires all input exprs here
plan.inputs()
.into_iter()
.map(RequiredIndices::new_for_all_exprs)
.collect()
}
}
```
instead of
https://github.com/apache/datafusion/blob/b6d46a63824f003117297848d8d83b659ac2e759/datafusion/optimizer/src/optimize_projections/mod.rs#L331-L337
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## Are these changes tested?
Yes.
In addition to unit tests, I've also added a complete end-to-end integration
test that reproduces the full scenario in the issue. This might seem redundant,
bloated, or even unnecessary. Please let me know if I should remove these tests.
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## Are there any user-facing changes?
Yes. But I think the new implementation is the expected behavior.
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