alamb commented on code in PR #17560: URL: https://github.com/apache/datafusion/pull/17560#discussion_r2353293646
########## datafusion/functions-aggregate-common/src/aggregate/avg_distinct/decimal.rs: ########## @@ -0,0 +1,192 @@ +// Licensed to the Apache Software Foundation (ASF) under one +// or more contributor license agreements. See the NOTICE file +// distributed with this work for additional information +// regarding copyright ownership. The ASF licenses this file +// 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. + +use arrow::{ + array::{ArrayRef, ArrowNumericType}, + datatypes::{i256, Decimal128Type, Decimal256Type, DecimalType}, +}; +use datafusion_common::{Result, ScalarValue}; +use datafusion_expr_common::accumulator::Accumulator; +use std::fmt::Debug; +use std::mem::size_of_val; + +use crate::aggregate::sum_distinct::DistinctSumAccumulator; +use crate::utils::DecimalAverager; + +/// Generic implementation of `AVG DISTINCT` for Decimal types. +/// Handles both Decimal128Type and Decimal256Type. +#[derive(Debug)] +pub struct DecimalDistinctAvgAccumulator<T: DecimalType + Debug> { + sum_accumulator: DistinctSumAccumulator<T>, + sum_scale: i8, + target_precision: u8, + target_scale: i8, +} + +impl<T: DecimalType + Debug> DecimalDistinctAvgAccumulator<T> { + pub fn with_decimal_params( + sum_scale: i8, + target_precision: u8, + target_scale: i8, + ) -> Self { + let data_type = T::TYPE_CONSTRUCTOR(T::MAX_PRECISION, sum_scale); + + Self { + sum_accumulator: DistinctSumAccumulator::new(&data_type), + sum_scale, + target_precision, + target_scale, + } + } +} + +impl<T: DecimalType + ArrowNumericType + Debug> Accumulator + for DecimalDistinctAvgAccumulator<T> +{ + fn state(&mut self) -> Result<Vec<ScalarValue>> { + self.sum_accumulator.state() + } + + fn update_batch(&mut self, values: &[ArrayRef]) -> Result<()> { + self.sum_accumulator.update_batch(values) + } + + fn merge_batch(&mut self, states: &[ArrayRef]) -> Result<()> { + self.sum_accumulator.merge_batch(states) + } + + fn evaluate(&mut self) -> Result<ScalarValue> { + if self.sum_accumulator.distinct_count() == 0 { + return ScalarValue::new_primitive::<T>( + None, + &T::TYPE_CONSTRUCTOR(self.target_precision, self.target_scale), + ); + } + + let sum_scalar = self.sum_accumulator.evaluate()?; + + match sum_scalar { + ScalarValue::Decimal128(Some(sum), _, _) => { + let decimal_averager = DecimalAverager::<Decimal128Type>::try_new( + self.sum_scale, + self.target_precision, + self.target_scale, + )?; + let avg = decimal_averager + .avg(sum, self.sum_accumulator.distinct_count() as i128)?; + Ok(ScalarValue::Decimal128( + Some(avg), + self.target_precision, + self.target_scale, + )) + } + ScalarValue::Decimal256(Some(sum), _, _) => { + let decimal_averager = DecimalAverager::<Decimal256Type>::try_new( + self.sum_scale, + self.target_precision, + self.target_scale, + )?; + // `distinct_count` returns `u64`, but `avg` expects `i256` Review Comment: I found this strange but after poking around I see there isn't a direct conversion from u64 --> i256: ```rust let count: i256 = self.sum_accumulator.distinct_count().into(); ``` ``` error[E0277]: the trait bound `arrow::datatypes::i256: std::convert::From<usize>` is not satisfied --> datafusion/functions-aggregate-common/src/aggregate/avg_distinct/decimal.rs:105:73 | 105 | let count: i256 = self.sum_accumulator.distinct_count().into(); | ^^^^ the trait `std::convert::From<usize>` is not implemented for `arrow::datatypes::i256` | ``` ########## datafusion/functions-aggregate/src/average.rs: ########## @@ -161,22 +187,31 @@ impl AggregateUDFImpl for Avg { })) } - _ => exec_err!( - "AvgAccumulator for ({} --> {})", - &data_type, - acc_args.return_field.data_type() - ), + (dt, return_type) => { + exec_err!("AvgAccumulator for ({} --> {})", dt, return_type) + } } } } fn state_fields(&self, args: StateFieldsArgs) -> Result<Vec<FieldRef>> { if args.is_distinct { - // Copied from datafusion_functions_aggregate::sum::Sum::state_fields + // Decimal accumulator actually uses a different precision during accumulation, Review Comment: 👍 -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected] --------------------------------------------------------------------- To unsubscribe, e-mail: [email protected] For additional commands, e-mail: [email protected]
