Method create_groups_accumulator

datafusion/functions-aggregate/src/average.rs:347–488

(
        &self,
        args: AccumulatorArgs,
    )

    }

    fn create_groups_accumulator(
        &self,
        args: AccumulatorArgs,
    ) -> Result<Box<dyn GroupsAccumulator>> {
        use DataType::*;

        let data_type = args.expr_fields[0].data_type();

        // instantiate specialized accumulator based for the type
        match (data_type, args.return_field.data_type()) {
            (Float64, Float64) => {
                Ok(Box::new(AvgGroupsAccumulator::<Float64Type, _>::new(
                    data_type,
                    args.return_field.data_type(),
                    |sum: f64, count: u64| Ok(sum / count as f64),
                )))
            }
            (
                Decimal32(_sum_precision, sum_scale),
                Decimal32(target_precision, target_scale),
            ) => {
                let decimal_averager = DecimalAverager::<Decimal32Type>::try_new(
                    *sum_scale,
                    *target_precision,
                    *target_scale,
                )?;

                let avg_fn =
                    move |sum: i32, count: u64| decimal_averager.avg(sum, count as i32);

                Ok(Box::new(AvgGroupsAccumulator::<Decimal32Type, _>::new(
                    data_type,
                    args.return_field.data_type(),
                    avg_fn,
                )))
            }
            (
                Decimal64(_sum_precision, sum_scale),
                Decimal64(target_precision, target_scale),
            ) => {
                let decimal_averager = DecimalAverager::<Decimal64Type>::try_new(
                    *sum_scale,
                    *target_precision,
                    *target_scale,
                )?;

                let avg_fn =
                    move |sum: i64, count: u64| decimal_averager.avg(sum, count as i64);

                Ok(Box::new(AvgGroupsAccumulator::<Decimal64Type, _>::new(
                    data_type,
                    args.return_field.data_type(),
                    avg_fn,
                )))
            }
            (
                Decimal128(_sum_precision, sum_scale),
                Decimal128(target_precision, target_scale),