datafusion-expr 10.0.0

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// distributed with this work for additional information
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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
//
// Unless required by applicable law or agreed to in writing,
// software distributed under the License is distributed on an
// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
// KIND, either express or implied.  See the License for the
// specific language governing permissions and limitations
// under the License.

//! Aggregate function module contains all built-in aggregate functions definitions

use crate::{Signature, TypeSignature, Volatility};
use arrow::datatypes::{
    DataType, Field, TimeUnit, DECIMAL_MAX_PRECISION, DECIMAL_MAX_SCALE,
};
use datafusion_common::{DataFusionError, Result};
use std::ops::Deref;
use std::{fmt, str::FromStr};

pub static STRINGS: &[DataType] = &[DataType::Utf8, DataType::LargeUtf8];

pub static NUMERICS: &[DataType] = &[
    DataType::Int8,
    DataType::Int16,
    DataType::Int32,
    DataType::Int64,
    DataType::UInt8,
    DataType::UInt16,
    DataType::UInt32,
    DataType::UInt64,
    DataType::Float32,
    DataType::Float64,
];

pub static TIMESTAMPS: &[DataType] = &[
    DataType::Timestamp(TimeUnit::Second, None),
    DataType::Timestamp(TimeUnit::Millisecond, None),
    DataType::Timestamp(TimeUnit::Microsecond, None),
    DataType::Timestamp(TimeUnit::Nanosecond, None),
];

pub static DATES: &[DataType] = &[DataType::Date32, DataType::Date64];

/// Enum of all built-in aggregate functions
#[derive(Debug, Clone, PartialEq, Eq, PartialOrd, Hash)]
pub enum AggregateFunction {
    /// count
    Count,
    /// sum
    Sum,
    /// min
    Min,
    /// max
    Max,
    /// avg
    Avg,
    /// Approximate aggregate function
    ApproxDistinct,
    /// array_agg
    ArrayAgg,
    /// Variance (Sample)
    Variance,
    /// Variance (Population)
    VariancePop,
    /// Standard Deviation (Sample)
    Stddev,
    /// Standard Deviation (Population)
    StddevPop,
    /// Covariance (Sample)
    Covariance,
    /// Covariance (Population)
    CovariancePop,
    /// Correlation
    Correlation,
    /// Approximate continuous percentile function
    ApproxPercentileCont,
    /// Approximate continuous percentile function with weight
    ApproxPercentileContWithWeight,
    /// ApproxMedian
    ApproxMedian,
    /// Grouping
    Grouping,
}

impl fmt::Display for AggregateFunction {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        // uppercase of the debug.
        write!(f, "{}", format!("{:?}", self).to_uppercase())
    }
}

impl FromStr for AggregateFunction {
    type Err = DataFusionError;
    fn from_str(name: &str) -> Result<AggregateFunction> {
        Ok(match name {
            "min" => AggregateFunction::Min,
            "max" => AggregateFunction::Max,
            "count" => AggregateFunction::Count,
            "avg" => AggregateFunction::Avg,
            "sum" => AggregateFunction::Sum,
            "approx_distinct" => AggregateFunction::ApproxDistinct,
            "array_agg" => AggregateFunction::ArrayAgg,
            "var" => AggregateFunction::Variance,
            "var_samp" => AggregateFunction::Variance,
            "var_pop" => AggregateFunction::VariancePop,
            "stddev" => AggregateFunction::Stddev,
            "stddev_samp" => AggregateFunction::Stddev,
            "stddev_pop" => AggregateFunction::StddevPop,
            "covar" => AggregateFunction::Covariance,
            "covar_samp" => AggregateFunction::Covariance,
            "covar_pop" => AggregateFunction::CovariancePop,
            "corr" => AggregateFunction::Correlation,
            "approx_percentile_cont" => AggregateFunction::ApproxPercentileCont,
            "approx_percentile_cont_with_weight" => {
                AggregateFunction::ApproxPercentileContWithWeight
            }
            "approx_median" => AggregateFunction::ApproxMedian,
            "grouping" => AggregateFunction::Grouping,
            _ => {
                return Err(DataFusionError::Plan(format!(
                    "There is no built-in function named {}",
                    name
                )));
            }
        })
    }
}

/// Returns the datatype of the aggregate function.
/// This is used to get the returned data type for aggregate expr.
pub fn return_type(
    fun: &AggregateFunction,
    input_expr_types: &[DataType],
) -> Result<DataType> {
    // Note that this function *must* return the same type that the respective physical expression returns
    // or the execution panics.

    let coerced_data_types = coerce_types(fun, input_expr_types, &signature(fun))?;

    match fun {
        AggregateFunction::Count | AggregateFunction::ApproxDistinct => {
            Ok(DataType::Int64)
        }
        AggregateFunction::Max | AggregateFunction::Min => {
            // For min and max agg function, the returned type is same as input type.
            // The coerced_data_types is same with input_types.
            Ok(coerced_data_types[0].clone())
        }
        AggregateFunction::Sum => sum_return_type(&coerced_data_types[0]),
        AggregateFunction::Variance => variance_return_type(&coerced_data_types[0]),
        AggregateFunction::VariancePop => variance_return_type(&coerced_data_types[0]),
        AggregateFunction::Covariance => covariance_return_type(&coerced_data_types[0]),
        AggregateFunction::CovariancePop => {
            covariance_return_type(&coerced_data_types[0])
        }
        AggregateFunction::Correlation => correlation_return_type(&coerced_data_types[0]),
        AggregateFunction::Stddev => stddev_return_type(&coerced_data_types[0]),
        AggregateFunction::StddevPop => stddev_return_type(&coerced_data_types[0]),
        AggregateFunction::Avg => avg_return_type(&coerced_data_types[0]),
        AggregateFunction::ArrayAgg => Ok(DataType::List(Box::new(Field::new(
            "item",
            coerced_data_types[0].clone(),
            true,
        )))),
        AggregateFunction::ApproxPercentileCont => Ok(coerced_data_types[0].clone()),
        AggregateFunction::ApproxPercentileContWithWeight => {
            Ok(coerced_data_types[0].clone())
        }
        AggregateFunction::ApproxMedian => Ok(coerced_data_types[0].clone()),
        AggregateFunction::Grouping => Ok(DataType::Int32),
    }
}

/// Returns the coerced data type for each `input_types`.
/// Different aggregate function with different input data type will get corresponding coerced data type.
pub fn coerce_types(
    agg_fun: &AggregateFunction,
    input_types: &[DataType],
    signature: &Signature,
) -> Result<Vec<DataType>> {
    // Validate input_types matches (at least one of) the func signature.
    check_arg_count(agg_fun, input_types, &signature.type_signature)?;

    match agg_fun {
        AggregateFunction::Count | AggregateFunction::ApproxDistinct => {
            Ok(input_types.to_vec())
        }
        AggregateFunction::ArrayAgg => Ok(input_types.to_vec()),
        AggregateFunction::Min | AggregateFunction::Max => {
            // min and max support the dictionary data type
            // unpack the dictionary to get the value
            get_min_max_result_type(input_types)
        }
        AggregateFunction::Sum => {
            // Refer to https://www.postgresql.org/docs/8.2/functions-aggregate.html doc
            // smallint, int, bigint, real, double precision, decimal, or interval.
            if !is_sum_support_arg_type(&input_types[0]) {
                return Err(DataFusionError::Plan(format!(
                    "The function {:?} does not support inputs of type {:?}.",
                    agg_fun, input_types[0]
                )));
            }
            Ok(input_types.to_vec())
        }
        AggregateFunction::Avg => {
            // Refer to https://www.postgresql.org/docs/8.2/functions-aggregate.html doc
            // smallint, int, bigint, real, double precision, decimal, or interval
            if !is_avg_support_arg_type(&input_types[0]) {
                return Err(DataFusionError::Plan(format!(
                    "The function {:?} does not support inputs of type {:?}.",
                    agg_fun, input_types[0]
                )));
            }
            Ok(input_types.to_vec())
        }
        AggregateFunction::Variance => {
            if !is_variance_support_arg_type(&input_types[0]) {
                return Err(DataFusionError::Plan(format!(
                    "The function {:?} does not support inputs of type {:?}.",
                    agg_fun, input_types[0]
                )));
            }
            Ok(input_types.to_vec())
        }
        AggregateFunction::VariancePop => {
            if !is_variance_support_arg_type(&input_types[0]) {
                return Err(DataFusionError::Plan(format!(
                    "The function {:?} does not support inputs of type {:?}.",
                    agg_fun, input_types[0]
                )));
            }
            Ok(input_types.to_vec())
        }
        AggregateFunction::Covariance => {
            if !is_covariance_support_arg_type(&input_types[0]) {
                return Err(DataFusionError::Plan(format!(
                    "The function {:?} does not support inputs of type {:?}.",
                    agg_fun, input_types[0]
                )));
            }
            Ok(input_types.to_vec())
        }
        AggregateFunction::CovariancePop => {
            if !is_covariance_support_arg_type(&input_types[0]) {
                return Err(DataFusionError::Plan(format!(
                    "The function {:?} does not support inputs of type {:?}.",
                    agg_fun, input_types[0]
                )));
            }
            Ok(input_types.to_vec())
        }
        AggregateFunction::Stddev => {
            if !is_stddev_support_arg_type(&input_types[0]) {
                return Err(DataFusionError::Plan(format!(
                    "The function {:?} does not support inputs of type {:?}.",
                    agg_fun, input_types[0]
                )));
            }
            Ok(input_types.to_vec())
        }
        AggregateFunction::StddevPop => {
            if !is_stddev_support_arg_type(&input_types[0]) {
                return Err(DataFusionError::Plan(format!(
                    "The function {:?} does not support inputs of type {:?}.",
                    agg_fun, input_types[0]
                )));
            }
            Ok(input_types.to_vec())
        }
        AggregateFunction::Correlation => {
            if !is_correlation_support_arg_type(&input_types[0]) {
                return Err(DataFusionError::Plan(format!(
                    "The function {:?} does not support inputs of type {:?}.",
                    agg_fun, input_types[0]
                )));
            }
            Ok(input_types.to_vec())
        }
        AggregateFunction::ApproxPercentileCont => {
            if !is_approx_percentile_cont_supported_arg_type(&input_types[0]) {
                return Err(DataFusionError::Plan(format!(
                    "The function {:?} does not support inputs of type {:?}.",
                    agg_fun, input_types[0]
                )));
            }
            if !matches!(input_types[1], DataType::Float64) {
                return Err(DataFusionError::Plan(format!(
                    "The percentile argument for {:?} must be Float64, not {:?}.",
                    agg_fun, input_types[1]
                )));
            }
            Ok(input_types.to_vec())
        }
        AggregateFunction::ApproxPercentileContWithWeight => {
            if !is_approx_percentile_cont_supported_arg_type(&input_types[0]) {
                return Err(DataFusionError::Plan(format!(
                    "The function {:?} does not support inputs of type {:?}.",
                    agg_fun, input_types[0]
                )));
            }
            if !is_approx_percentile_cont_supported_arg_type(&input_types[1]) {
                return Err(DataFusionError::Plan(format!(
                    "The weight argument for {:?} does not support inputs of type {:?}.",
                    agg_fun, input_types[1]
                )));
            }
            if !matches!(input_types[2], DataType::Float64) {
                return Err(DataFusionError::Plan(format!(
                    "The percentile argument for {:?} must be Float64, not {:?}.",
                    agg_fun, input_types[2]
                )));
            }
            Ok(input_types.to_vec())
        }
        AggregateFunction::ApproxMedian => {
            if !is_approx_percentile_cont_supported_arg_type(&input_types[0]) {
                return Err(DataFusionError::Plan(format!(
                    "The function {:?} does not support inputs of type {:?}.",
                    agg_fun, input_types[0]
                )));
            }
            Ok(input_types.to_vec())
        }
        AggregateFunction::Grouping => Ok(vec![input_types[0].clone()]),
    }
}

/// the signatures supported by the function `fun`.
pub fn signature(fun: &AggregateFunction) -> Signature {
    // note: the physical expression must accept the type returned by this function or the execution panics.
    match fun {
        AggregateFunction::Count
        | AggregateFunction::ApproxDistinct
        | AggregateFunction::Grouping
        | AggregateFunction::ArrayAgg => Signature::any(1, Volatility::Immutable),
        AggregateFunction::Min | AggregateFunction::Max => {
            let valid = STRINGS
                .iter()
                .chain(NUMERICS.iter())
                .chain(TIMESTAMPS.iter())
                .chain(DATES.iter())
                .cloned()
                .collect::<Vec<_>>();
            Signature::uniform(1, valid, Volatility::Immutable)
        }
        AggregateFunction::Avg
        | AggregateFunction::Sum
        | AggregateFunction::Variance
        | AggregateFunction::VariancePop
        | AggregateFunction::Stddev
        | AggregateFunction::StddevPop
        | AggregateFunction::ApproxMedian => {
            Signature::uniform(1, NUMERICS.to_vec(), Volatility::Immutable)
        }
        AggregateFunction::Covariance | AggregateFunction::CovariancePop => {
            Signature::uniform(2, NUMERICS.to_vec(), Volatility::Immutable)
        }
        AggregateFunction::Correlation => {
            Signature::uniform(2, NUMERICS.to_vec(), Volatility::Immutable)
        }
        AggregateFunction::ApproxPercentileCont => Signature::one_of(
            // Accept any numeric value paired with a float64 percentile
            NUMERICS
                .iter()
                .map(|t| TypeSignature::Exact(vec![t.clone(), DataType::Float64]))
                .collect(),
            Volatility::Immutable,
        ),
        AggregateFunction::ApproxPercentileContWithWeight => Signature::one_of(
            // Accept any numeric value paired with a float64 percentile
            NUMERICS
                .iter()
                .map(|t| {
                    TypeSignature::Exact(vec![t.clone(), t.clone(), DataType::Float64])
                })
                .collect(),
            Volatility::Immutable,
        ),
    }
}

/// function return type of a sum
pub fn sum_return_type(arg_type: &DataType) -> Result<DataType> {
    match arg_type {
        DataType::Int8 | DataType::Int16 | DataType::Int32 | DataType::Int64 => {
            Ok(DataType::Int64)
        }
        DataType::UInt8 | DataType::UInt16 | DataType::UInt32 | DataType::UInt64 => {
            Ok(DataType::UInt64)
        }
        // In the https://www.postgresql.org/docs/current/functions-aggregate.html doc,
        // the result type of floating-point is FLOAT64 with the double precision.
        DataType::Float64 | DataType::Float32 => Ok(DataType::Float64),
        DataType::Decimal(precision, scale) => {
            // in the spark, the result type is DECIMAL(min(38,precision+10), s)
            // ref: https://github.com/apache/spark/blob/fcf636d9eb8d645c24be3db2d599aba2d7e2955a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/aggregate/Sum.scala#L66
            let new_precision = DECIMAL_MAX_PRECISION.min(*precision + 10);
            Ok(DataType::Decimal(new_precision, *scale))
        }
        other => Err(DataFusionError::Plan(format!(
            "SUM does not support type \"{:?}\"",
            other
        ))),
    }
}

/// function return type of variance
pub fn variance_return_type(arg_type: &DataType) -> Result<DataType> {
    match arg_type {
        DataType::Int8
        | DataType::Int16
        | DataType::Int32
        | DataType::Int64
        | DataType::UInt8
        | DataType::UInt16
        | DataType::UInt32
        | DataType::UInt64
        | DataType::Float32
        | DataType::Float64 => Ok(DataType::Float64),
        other => Err(DataFusionError::Plan(format!(
            "VAR does not support {:?}",
            other
        ))),
    }
}

/// function return type of covariance
pub fn covariance_return_type(arg_type: &DataType) -> Result<DataType> {
    match arg_type {
        DataType::Int8
        | DataType::Int16
        | DataType::Int32
        | DataType::Int64
        | DataType::UInt8
        | DataType::UInt16
        | DataType::UInt32
        | DataType::UInt64
        | DataType::Float32
        | DataType::Float64 => Ok(DataType::Float64),
        other => Err(DataFusionError::Plan(format!(
            "COVAR does not support {:?}",
            other
        ))),
    }
}

/// function return type of correlation
pub fn correlation_return_type(arg_type: &DataType) -> Result<DataType> {
    match arg_type {
        DataType::Int8
        | DataType::Int16
        | DataType::Int32
        | DataType::Int64
        | DataType::UInt8
        | DataType::UInt16
        | DataType::UInt32
        | DataType::UInt64
        | DataType::Float32
        | DataType::Float64 => Ok(DataType::Float64),
        other => Err(DataFusionError::Plan(format!(
            "CORR does not support {:?}",
            other
        ))),
    }
}

/// function return type of standard deviation
pub fn stddev_return_type(arg_type: &DataType) -> Result<DataType> {
    match arg_type {
        DataType::Int8
        | DataType::Int16
        | DataType::Int32
        | DataType::Int64
        | DataType::UInt8
        | DataType::UInt16
        | DataType::UInt32
        | DataType::UInt64
        | DataType::Float32
        | DataType::Float64 => Ok(DataType::Float64),
        other => Err(DataFusionError::Plan(format!(
            "STDDEV does not support {:?}",
            other
        ))),
    }
}

/// function return type of an average
pub fn avg_return_type(arg_type: &DataType) -> Result<DataType> {
    match arg_type {
        DataType::Decimal(precision, scale) => {
            // in the spark, the result type is DECIMAL(min(38,precision+4), min(38,scale+4)).
            // ref: https://github.com/apache/spark/blob/fcf636d9eb8d645c24be3db2d599aba2d7e2955a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/aggregate/Average.scala#L66
            let new_precision = DECIMAL_MAX_PRECISION.min(*precision + 4);
            let new_scale = DECIMAL_MAX_SCALE.min(*scale + 4);
            Ok(DataType::Decimal(new_precision, new_scale))
        }
        DataType::Int8
        | DataType::Int16
        | DataType::Int32
        | DataType::Int64
        | DataType::UInt8
        | DataType::UInt16
        | DataType::UInt32
        | DataType::UInt64
        | DataType::Float32
        | DataType::Float64 => Ok(DataType::Float64),
        other => Err(DataFusionError::Plan(format!(
            "AVG does not support {:?}",
            other
        ))),
    }
}

/// Validate the length of `input_types` matches the `signature` for `agg_fun`.
///
/// This method DOES NOT validate the argument types - only that (at least one,
/// in the case of [`TypeSignature::OneOf`]) signature matches the desired
/// number of input types.
fn check_arg_count(
    agg_fun: &AggregateFunction,
    input_types: &[DataType],
    signature: &TypeSignature,
) -> Result<()> {
    match signature {
        TypeSignature::Uniform(agg_count, _) | TypeSignature::Any(agg_count) => {
            if input_types.len() != *agg_count {
                return Err(DataFusionError::Plan(format!(
                    "The function {:?} expects {:?} arguments, but {:?} were provided",
                    agg_fun,
                    agg_count,
                    input_types.len()
                )));
            }
        }
        TypeSignature::Exact(types) => {
            if types.len() != input_types.len() {
                return Err(DataFusionError::Plan(format!(
                    "The function {:?} expects {:?} arguments, but {:?} were provided",
                    agg_fun,
                    types.len(),
                    input_types.len()
                )));
            }
        }
        TypeSignature::OneOf(variants) => {
            let ok = variants
                .iter()
                .any(|v| check_arg_count(agg_fun, input_types, v).is_ok());
            if !ok {
                return Err(DataFusionError::Plan(format!(
                    "The function {:?} does not accept {:?} function arguments.",
                    agg_fun,
                    input_types.len()
                )));
            }
        }
        _ => {
            return Err(DataFusionError::Internal(format!(
                "Aggregate functions do not support this {:?}",
                signature
            )));
        }
    }
    Ok(())
}

fn get_min_max_result_type(input_types: &[DataType]) -> Result<Vec<DataType>> {
    // make sure that the input types only has one element.
    assert_eq!(input_types.len(), 1);
    // min and max support the dictionary data type
    // unpack the dictionary to get the value
    match &input_types[0] {
        DataType::Dictionary(_, dict_value_type) => {
            // TODO add checker, if the value type is complex data type
            Ok(vec![dict_value_type.deref().clone()])
        }
        // TODO add checker for datatype which min and max supported
        // For example, the `Struct` and `Map` type are not supported in the MIN and MAX function
        _ => Ok(input_types.to_vec()),
    }
}

pub fn is_sum_support_arg_type(arg_type: &DataType) -> bool {
    matches!(
        arg_type,
        DataType::UInt8
            | DataType::UInt16
            | DataType::UInt32
            | DataType::UInt64
            | DataType::Int8
            | DataType::Int16
            | DataType::Int32
            | DataType::Int64
            | DataType::Float32
            | DataType::Float64
            | DataType::Decimal(_, _)
    )
}

pub fn is_avg_support_arg_type(arg_type: &DataType) -> bool {
    matches!(
        arg_type,
        DataType::UInt8
            | DataType::UInt16
            | DataType::UInt32
            | DataType::UInt64
            | DataType::Int8
            | DataType::Int16
            | DataType::Int32
            | DataType::Int64
            | DataType::Float32
            | DataType::Float64
            | DataType::Decimal(_, _)
    )
}

pub fn is_variance_support_arg_type(arg_type: &DataType) -> bool {
    matches!(
        arg_type,
        DataType::UInt8
            | DataType::UInt16
            | DataType::UInt32
            | DataType::UInt64
            | DataType::Int8
            | DataType::Int16
            | DataType::Int32
            | DataType::Int64
            | DataType::Float32
            | DataType::Float64
    )
}

pub fn is_covariance_support_arg_type(arg_type: &DataType) -> bool {
    matches!(
        arg_type,
        DataType::UInt8
            | DataType::UInt16
            | DataType::UInt32
            | DataType::UInt64
            | DataType::Int8
            | DataType::Int16
            | DataType::Int32
            | DataType::Int64
            | DataType::Float32
            | DataType::Float64
    )
}

pub fn is_stddev_support_arg_type(arg_type: &DataType) -> bool {
    matches!(
        arg_type,
        DataType::UInt8
            | DataType::UInt16
            | DataType::UInt32
            | DataType::UInt64
            | DataType::Int8
            | DataType::Int16
            | DataType::Int32
            | DataType::Int64
            | DataType::Float32
            | DataType::Float64
    )
}

pub fn is_correlation_support_arg_type(arg_type: &DataType) -> bool {
    matches!(
        arg_type,
        DataType::UInt8
            | DataType::UInt16
            | DataType::UInt32
            | DataType::UInt64
            | DataType::Int8
            | DataType::Int16
            | DataType::Int32
            | DataType::Int64
            | DataType::Float32
            | DataType::Float64
    )
}

/// Return `true` if `arg_type` is of a [`DataType`] that the
/// [`AggregateFunction::ApproxPercentileCont`] aggregation can operate on.
pub fn is_approx_percentile_cont_supported_arg_type(arg_type: &DataType) -> bool {
    matches!(
        arg_type,
        DataType::UInt8
            | DataType::UInt16
            | DataType::UInt32
            | DataType::UInt64
            | DataType::Int8
            | DataType::Int16
            | DataType::Int32
            | DataType::Int64
            | DataType::Float32
            | DataType::Float64
    )
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::aggregate_function;
    use arrow::datatypes::DataType;

    #[test]
    fn test_aggregate_coerce_types() {
        // test input args with error number input types
        let fun = AggregateFunction::Min;
        let input_types = vec![DataType::Int64, DataType::Int32];
        let signature = aggregate_function::signature(&fun);
        let result = coerce_types(&fun, &input_types, &signature);
        assert_eq!("Error during planning: The function Min expects 1 arguments, but 2 were provided", result.unwrap_err().to_string());

        // test input args is invalid data type for sum or avg
        let fun = AggregateFunction::Sum;
        let input_types = vec![DataType::Utf8];
        let signature = aggregate_function::signature(&fun);
        let result = coerce_types(&fun, &input_types, &signature);
        assert_eq!(
            "Error during planning: The function Sum does not support inputs of type Utf8.",
            result.unwrap_err().to_string()
        );
        let fun = AggregateFunction::Avg;
        let signature = aggregate_function::signature(&fun);
        let result = coerce_types(&fun, &input_types, &signature);
        assert_eq!(
            "Error during planning: The function Avg does not support inputs of type Utf8.",
            result.unwrap_err().to_string()
        );

        // test count, array_agg, approx_distinct, min, max.
        // the coerced types is same with input types
        let funs = vec![
            AggregateFunction::Count,
            AggregateFunction::ArrayAgg,
            AggregateFunction::ApproxDistinct,
            AggregateFunction::Min,
            AggregateFunction::Max,
        ];
        let input_types = vec![
            vec![DataType::Int32],
            vec![DataType::Decimal(10, 2)],
            vec![DataType::Utf8],
        ];
        for fun in funs {
            for input_type in &input_types {
                let signature = aggregate_function::signature(&fun);
                let result = coerce_types(&fun, input_type, &signature);
                assert_eq!(*input_type, result.unwrap());
            }
        }
        // test sum, avg
        let funs = vec![AggregateFunction::Sum, AggregateFunction::Avg];
        let input_types = vec![
            vec![DataType::Int32],
            vec![DataType::Float32],
            vec![DataType::Decimal(20, 3)],
        ];
        for fun in funs {
            for input_type in &input_types {
                let signature = aggregate_function::signature(&fun);
                let result = coerce_types(&fun, input_type, &signature);
                assert_eq!(*input_type, result.unwrap());
            }
        }

        // ApproxPercentileCont input types
        let input_types = vec![
            vec![DataType::Int8, DataType::Float64],
            vec![DataType::Int16, DataType::Float64],
            vec![DataType::Int32, DataType::Float64],
            vec![DataType::Int64, DataType::Float64],
            vec![DataType::UInt8, DataType::Float64],
            vec![DataType::UInt16, DataType::Float64],
            vec![DataType::UInt32, DataType::Float64],
            vec![DataType::UInt64, DataType::Float64],
            vec![DataType::Float32, DataType::Float64],
            vec![DataType::Float64, DataType::Float64],
        ];
        for input_type in &input_types {
            let signature =
                aggregate_function::signature(&AggregateFunction::ApproxPercentileCont);
            let result = coerce_types(
                &AggregateFunction::ApproxPercentileCont,
                input_type,
                &signature,
            );
            assert_eq!(*input_type, result.unwrap());
        }
    }

    #[test]
    fn test_avg_return_data_type() -> Result<()> {
        let data_type = DataType::Decimal(10, 5);
        let result_type = avg_return_type(&data_type)?;
        assert_eq!(DataType::Decimal(14, 9), result_type);

        let data_type = DataType::Decimal(36, 10);
        let result_type = avg_return_type(&data_type)?;
        assert_eq!(DataType::Decimal(38, 14), result_type);
        Ok(())
    }

    #[test]
    fn test_variance_return_data_type() -> Result<()> {
        let data_type = DataType::Float64;
        let result_type = variance_return_type(&data_type)?;
        assert_eq!(DataType::Float64, result_type);

        let data_type = DataType::Decimal(36, 10);
        assert!(variance_return_type(&data_type).is_err());
        Ok(())
    }

    #[test]
    fn test_sum_return_data_type() -> Result<()> {
        let data_type = DataType::Decimal(10, 5);
        let result_type = sum_return_type(&data_type)?;
        assert_eq!(DataType::Decimal(20, 5), result_type);

        let data_type = DataType::Decimal(36, 10);
        let result_type = sum_return_type(&data_type)?;
        assert_eq!(DataType::Decimal(38, 10), result_type);
        Ok(())
    }

    #[test]
    fn test_stddev_return_data_type() -> Result<()> {
        let data_type = DataType::Float64;
        let result_type = stddev_return_type(&data_type)?;
        assert_eq!(DataType::Float64, result_type);

        let data_type = DataType::Decimal(36, 10);
        assert!(stddev_return_type(&data_type).is_err());
        Ok(())
    }

    #[test]
    fn test_covariance_return_data_type() -> Result<()> {
        let data_type = DataType::Float64;
        let result_type = covariance_return_type(&data_type)?;
        assert_eq!(DataType::Float64, result_type);

        let data_type = DataType::Decimal(36, 10);
        assert!(covariance_return_type(&data_type).is_err());
        Ok(())
    }

    #[test]
    fn test_correlation_return_data_type() -> Result<()> {
        let data_type = DataType::Float64;
        let result_type = correlation_return_type(&data_type)?;
        assert_eq!(DataType::Float64, result_type);

        let data_type = DataType::Decimal(36, 10);
        assert!(correlation_return_type(&data_type).is_err());
        Ok(())
    }
}