alamb commented on code in PR #7695: URL: https://github.com/apache/arrow-datafusion/pull/7695#discussion_r1341659929
########## 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: What is the reason for running with `EliminateFilter` and `PropagateEmptyRelation` as well here? ########## datafusion/optimizer/src/eliminate_nested_union.rs: ########## @@ -0,0 +1,146 @@ +// 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 replace nested unions to single union. +use crate::{OptimizerConfig, OptimizerRule}; +use datafusion_common::Result; +use datafusion_expr::{ + builder::project_with_column_index, + expr_rewriter::coerce_plan_expr_for_schema, + logical_plan::{LogicalPlan, Projection, Union}, +}; + +use crate::optimizer::ApplyOrder; +use std::sync::Arc; + +#[derive(Default)] +/// An optimization rule that replaces nested unions with a single union. +pub struct EliminateNestedUnion; + +impl EliminateNestedUnion { + #[allow(missing_docs)] + pub fn new() -> Self { + Self {} + } +} + +impl OptimizerRule for EliminateNestedUnion { + fn try_optimize( + &self, + plan: &LogicalPlan, + _config: &dyn OptimizerConfig, + ) -> Result<Option<LogicalPlan>> { + match plan { + LogicalPlan::Union(union) => { + let Union { inputs, schema } = union; + + let union_schema = schema.clone(); + + let inputs = inputs + .into_iter() + .flat_map(|plan| match Arc::as_ref(plan) { + LogicalPlan::Union(Union { inputs, .. }) => inputs.clone(), + _ => vec![Arc::clone(plan)], + }) + .map(|plan| { + let plan = coerce_plan_expr_for_schema(&plan, &union_schema)?; Review Comment: Calling the coercion logic looks right, but I didn't see any tests for this. -- This is an automated message from the Apache Git Service. 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