maruschin commented on code in PR #7695: URL: https://github.com/apache/arrow-datafusion/pull/7695#discussion_r1343273130
########## datafusion/optimizer/src/eliminate_one_union.rs: ########## @@ -0,0 +1,125 @@ +// 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. + +//! Optimizer rule to eliminate one union. +use crate::{OptimizerConfig, OptimizerRule}; +use datafusion_common::Result; +use datafusion_expr::logical_plan::{LogicalPlan, Union}; + +use crate::optimizer::ApplyOrder; + +#[derive(Default)] +/// An optimization rule that eliminates union with one element. +pub struct EliminateOneUnion; + +impl EliminateOneUnion { + #[allow(missing_docs)] + pub fn new() -> Self { + Self {} + } +} + +impl OptimizerRule for EliminateOneUnion { + fn try_optimize( + &self, + plan: &LogicalPlan, + _config: &dyn OptimizerConfig, + ) -> Result<Option<LogicalPlan>> { + match plan { + LogicalPlan::Union(union) if union.inputs.len() == 1 => { + let Union { inputs, schema: _ } = union; + + Ok(inputs.first().map(|input| input.as_ref().clone())) + } + _ => Ok(None), + } + } + + fn name(&self) -> &str { + "eliminate_one_union" + } + + fn apply_order(&self) -> Option<ApplyOrder> { + Some(ApplyOrder::TopDown) + } +} + +#[cfg(test)] +mod tests { + use super::*; + use crate::eliminate_filter::EliminateFilter; + use crate::propagate_empty_relation::PropagateEmptyRelation; + use crate::test::*; + use arrow::datatypes::{DataType, Field, Schema}; + use datafusion_common::ScalarValue; + use datafusion_expr::{logical_plan::table_scan, Expr}; + use std::sync::Arc; + + fn schema() -> Schema { + Schema::new(vec![ + Field::new("id", DataType::Int32, false), + Field::new("key", DataType::Utf8, false), + Field::new("value", DataType::Int32, false), + ]) + } + + fn assert_optimized_plan_equal(plan: &LogicalPlan, expected: &str) -> Result<()> { + assert_optimized_plan_eq_with_rules( + vec![ + Arc::new(EliminateFilter::new()), Review Comment: `EliminateFilter` to create EmpthyRelation, `PropogateEmpthyRelation` to remove it and get union with one element. Little overcomplicated. Rewrote test, just logical plan with single element. -- 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]
