milenkovicm commented on code in PR #10354: URL: https://github.com/apache/datafusion/pull/10354#discussion_r1589909868
########## datafusion-examples/examples/simplify_udaf_expression.rs: ########## @@ -0,0 +1,185 @@ +// 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_schema::{Field, Schema}; +use datafusion::{arrow::datatypes::DataType, logical_expr::Volatility}; +use datafusion_expr::simplify::SimplifyInfo; + +use std::{any::Any, sync::Arc}; + +use datafusion::arrow::{array::Float32Array, record_batch::RecordBatch}; +use datafusion::error::Result; +use datafusion::{assert_batches_eq, prelude::*}; +use datafusion_common::cast::as_float64_array; +use datafusion_expr::{ + expr::{AggregateFunction, AggregateFunctionDefinition}, + function::AccumulatorArgs, + simplify::ExprSimplifyResult, + Accumulator, AggregateUDF, AggregateUDFImpl, GroupsAccumulator, Signature, +}; + +/// This example shows how to use the AggregateUDFImpl::simplify API to simplify/replace user +/// defined aggregate function with a different expression which is defined in the `simplify` method. + +#[derive(Debug, Clone)] +struct BetterAvgUdaf { + signature: Signature, +} + +impl BetterAvgUdaf { + /// Create a new instance of the GeoMeanUdaf struct + fn new() -> Self { + Self { + signature: Signature::exact(vec![DataType::Float64], Volatility::Immutable), + } + } +} + +impl AggregateUDFImpl for BetterAvgUdaf { + fn as_any(&self) -> &dyn Any { + self + } + + fn name(&self) -> &str { + "better_avg" + } + + fn signature(&self) -> &Signature { + &self.signature + } + + fn return_type(&self, _arg_types: &[DataType]) -> Result<DataType> { + Ok(DataType::Float64) + } + + fn accumulator(&self, _acc_args: AccumulatorArgs) -> Result<Box<dyn Accumulator>> { + unimplemented!("should not be invoked") + } + + fn state_fields( + &self, + _name: &str, + _value_type: DataType, + _ordering_fields: Vec<arrow_schema::Field>, + ) -> Result<Vec<arrow_schema::Field>> { + unimplemented!("should not be invoked") + } + + fn groups_accumulator_supported(&self) -> bool { + true + } + + fn create_groups_accumulator(&self) -> Result<Box<dyn GroupsAccumulator>> { + unimplemented!("should not get here"); + } + // we override method, to return new expression which would substitute + // user defined function call + fn simplify( + &self, + args: Vec<Expr>, + distinct: &bool, Review Comment: I agree, if we make `ExprSimplifyResult` generic, as I pointed out in the comment. If we change it without change of `ExprSimplifyResult` it would lead to cloning of arguments even if simplify does nothing -- 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: github-unsubscr...@datafusion.apache.org For queries about this service, please contact Infrastructure at: us...@infra.apache.org --------------------------------------------------------------------- To unsubscribe, e-mail: github-unsubscr...@datafusion.apache.org For additional commands, e-mail: github-h...@datafusion.apache.org
