udf.rs

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// to you under the Apache License, Version 2.0 (the
// "License"); you may not use this file except in compliance
// with the License.  You may obtain a copy of the License at
//
//   http://www.apache.org/licenses/LICENSE-2.0
//
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// KIND, either express or implied.  See the License for the
// specific language governing permissions and limitations
// under the License.

//! UDF support

use fmt::{Debug, Formatter};
use std::fmt;

use arrow::datatypes::Schema;

use crate::error::Result;
use crate::{logical_plan::Expr, physical_plan::PhysicalExpr};

use super::{
    functions::{
        ReturnTypeFunction, ScalarFunctionExpr, ScalarFunctionImplementation, Signature,
    },
    type_coercion::coerce,
};
use std::sync::Arc;

/// Logical representation of a UDF.
#[derive(Clone)]
pub struct ScalarUDF {
    /// name
    pub name: String,
    /// signature
    pub signature: Signature,
    /// Return type
    pub return_type: ReturnTypeFunction,
    /// actual implementation
    ///
    /// The fn param is the wrapped function but be aware that the function will
    /// be passed with the slice / vec of columnar values (either scalar or array)
    /// with the exception of zero param function, where a singular element vec
    /// will be passed. In that case the single element is a null array to indicate
    /// the batch's row count (so that the generative zero-argument function can know
    /// the result array size).
    pub fun: ScalarFunctionImplementation,
}

impl Debug for ScalarUDF {
    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
        f.debug_struct("ScalarUDF")
            .field("name", &self.name)
            .field("signature", &self.signature)
            .field("fun", &"<FUNC>")
            .finish()
    }
}

impl PartialEq for ScalarUDF {
    fn eq(&self, other: &Self) -> bool {
        self.name == other.name && self.signature == other.signature
    }
}

impl std::hash::Hash for ScalarUDF {
    fn hash<H: std::hash::Hasher>(&self, state: &mut H) {
        self.name.hash(state);
        self.signature.hash(state);
    }
}

impl ScalarUDF {
    /// Create a new ScalarUDF
    pub fn new(
        name: &str,
        signature: &Signature,
        return_type: &ReturnTypeFunction,
        fun: &ScalarFunctionImplementation,
    ) -> Self {
        Self {
            name: name.to_owned(),
            signature: signature.clone(),
            return_type: return_type.clone(),
            fun: fun.clone(),
        }
    }

    /// creates a logical expression with a call of the UDF
    /// This utility allows using the UDF without requiring access to the registry.
    pub fn call(&self, args: Vec<Expr>) -> Expr {
        Expr::ScalarUDF {
            fun: Arc::new(self.clone()),
            args,
        }
    }
}

/// Create a physical expression of the UDF.
/// This function errors when `args`' can't be coerced to a valid argument type of the UDF.
pub fn create_physical_expr(
    fun: &ScalarUDF,
    input_phy_exprs: &[Arc<dyn PhysicalExpr>],
    input_schema: &Schema,
) -> Result<Arc<dyn PhysicalExpr>> {
    // coerce
    let coerced_phy_exprs = coerce(input_phy_exprs, input_schema, &fun.signature)?;

    let coerced_exprs_types = coerced_phy_exprs
        .iter()
        .map(|e| e.data_type(input_schema))
        .collect::<Result<Vec<_>>>()?;

    Ok(Arc::new(ScalarFunctionExpr::new(
        &fun.name,
        fun.fun.clone(),
        coerced_phy_exprs,
        (fun.return_type)(&coerced_exprs_types)?.as_ref(),
    )))
}