jorgecarleitao commented on a change in pull request #8032:
URL: https://github.com/apache/arrow/pull/8032#discussion_r477045153
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File path: rust/datafusion/src/logicalplan.rs
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@@ -1042,6 +998,35 @@ pub fn can_coerce_from(type_into: &DataType, type_from:
&DataType) -> bool {
}
}
+/// A registry of functions used to plan queries programmatically
Review comment:
That is an excellent idea. I am trying to implement it, but I am facing
a challenge; could you help me here?
I've implemented the trait and moved the implementation for the
`ExecutionContextState`, which is where the scalar is and what the DataFrame
has access to:
```
impl UDFFactory for ExecutionContextState {
fn udf(&self, name: &str, args: Vec<Expr>) -> Result<Expr> {
...
}
```
On the dataframe, we will need to do something like
```
fn registry(&self) -> &dyn UDFFactory {
self.ctx_state ...
}
```
but `self.ctx_state` is under a mutex: `Arc<Mutex<ExecutionContextState>>`.
This seems fair (safety wise): another thread could be trying to register a
new UDF while we are trying to use one, in which case one of them should wait.
However, I am struggling to write the interface to handle this.
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