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use crate::error::Result;
use datafusion_expr::{AggregateUDF, ScalarUDF};
use std::{collections::HashSet, sync::Arc};

/// A registry knows how to build logical expressions out of user-defined function' names
pub trait FunctionRegistry {
    /// Set of all available udfs.
    fn udfs(&self) -> HashSet<String>;

    /// Returns a reference to the udf named `name`.
    fn udf(&self, name: &str) -> Result<Arc<ScalarUDF>>;

    /// Returns a reference to the udaf named `name`.
    fn udaf(&self, name: &str) -> Result<Arc<AggregateUDF>>;
}
