Trait datafusion::logical_expr::WindowUDFImpl
source · pub trait WindowUDFImpl: Debug + Send + Sync {
// Required methods
fn as_any(&self) -> &(dyn Any + 'static);
fn name(&self) -> &str;
fn signature(&self) -> &Signature;
fn return_type(
&self,
arg_types: &[DataType]
) -> Result<DataType, DataFusionError>;
fn partition_evaluator(
&self
) -> Result<Box<dyn PartitionEvaluator>, DataFusionError>;
// Provided method
fn aliases(&self) -> &[String] { ... }
}
Expand description
Trait for implementing WindowUDF
.
This trait exposes the full API for implementing user defined window functions and can be used to implement any function.
See advanced_udwf.rs
for a full example with complete implementation and
WindowUDF
for other available options.
§Basic Example
#[derive(Debug, Clone)]
struct SmoothIt {
signature: Signature
};
impl SmoothIt {
fn new() -> Self {
Self {
signature: Signature::uniform(1, vec![DataType::Int32], Volatility::Immutable)
}
}
}
/// Implement the WindowUDFImpl trait for AddOne
impl WindowUDFImpl for SmoothIt {
fn as_any(&self) -> &dyn Any { self }
fn name(&self) -> &str { "smooth_it" }
fn signature(&self) -> &Signature { &self.signature }
fn return_type(&self, args: &[DataType]) -> Result<DataType> {
if !matches!(args.get(0), Some(&DataType::Int32)) {
return plan_err!("smooth_it only accepts Int32 arguments");
}
Ok(DataType::Int32)
}
// The actual implementation would add one to the argument
fn partition_evaluator(&self) -> Result<Box<dyn PartitionEvaluator>> { unimplemented!() }
}
// Create a new WindowUDF from the implementation
let smooth_it = WindowUDF::from(SmoothIt::new());
// Call the function `add_one(col)`
let expr = smooth_it.call(
vec![col("speed")], // smooth_it(speed)
vec![col("car")], // PARTITION BY car
vec![col("time").sort(true, true)], // ORDER BY time ASC
WindowFrame::new(None),
);
Required Methods§
sourcefn signature(&self) -> &Signature
fn signature(&self) -> &Signature
Returns the function’s Signature
for information about what input
types are accepted and the function’s Volatility.
sourcefn return_type(
&self,
arg_types: &[DataType]
) -> Result<DataType, DataFusionError>
fn return_type( &self, arg_types: &[DataType] ) -> Result<DataType, DataFusionError>
What DataType
will be returned by this function, given the types of
the arguments
sourcefn partition_evaluator(
&self
) -> Result<Box<dyn PartitionEvaluator>, DataFusionError>
fn partition_evaluator( &self ) -> Result<Box<dyn PartitionEvaluator>, DataFusionError>
Invoke the function, returning the PartitionEvaluator
instance
Provided Methods§
sourcefn aliases(&self) -> &[String]
fn aliases(&self) -> &[String]
Returns any aliases (alternate names) for this function.
Note: aliases
should only include names other than Self::name
.
Defaults to []
(no aliases)