alamb commented on code in PR #3482: URL: https://github.com/apache/arrow-datafusion/pull/3482#discussion_r973572268
########## datafusion/optimizer/src/reduce_cross_join.rs: ########## @@ -0,0 +1,452 @@ +// 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 reduce cross join to inner join if join predicates are available in filters. +use crate::{OptimizerConfig, OptimizerRule}; +use datafusion_common::{Column, Result}; +use datafusion_expr::{ + logical_plan::{Filter, Join, CrossJoin, JoinType, LogicalPlan}, + utils::from_plan, and, or, utils::can_hash +}; +use datafusion_expr::{Expr, Operator}; + +use std::collections::HashSet; + +//use std::collections::HashMap; +use std::sync::Arc; +use datafusion_expr::logical_plan::JoinConstraint; + +#[derive(Default)] +pub struct ReduceCrossJoin; + +impl ReduceCrossJoin { + #[allow(missing_docs)] + pub fn new() -> Self { + Self {} + } +} + +impl OptimizerRule for ReduceCrossJoin { + fn optimize( + &self, + plan: &LogicalPlan, + _optimizer_config: &mut OptimizerConfig, + ) -> Result<LogicalPlan> { + let mut possible_join_keys : Vec<(Column, Column)> = vec![]; + let mut all_join_keys = HashSet::new(); + + reduce_cross_join(self, plan, &mut possible_join_keys, &mut all_join_keys,) + } + + fn name(&self) -> &str { + "reduce_cross_join" + } +} + +/// Attempt to reduce cross joins to inner joins. +/// for queries: +/// 'select ... from a, b where a.x = b.y and b.xx = 100;' +/// 'select ... from a, b where (a.x = b.y and b.xx = 100) or (a.x = b.y and b.xx = 200);' +/// 'select ... from a, b, c where (a.x = b.y and b.xx = 100 and a.z = c.z) +/// or (a.x = b.y and b.xx = 200 and a.z=c.z);' +/// For above queries, the join predicate is available in filters and they are moved to +/// join nodes appropriately +/// This fix helps to improve the performance of TPCH Q19. issue#78 +/// +fn reduce_cross_join( + _optimizer: &ReduceCrossJoin, + plan: &LogicalPlan, + possible_join_keys: &mut Vec<(Column, Column)>, + all_join_keys: &mut HashSet<(Column, Column)>, +) -> Result<LogicalPlan> { + match plan { + LogicalPlan::Filter(Filter { input, predicate }) => { + extract_possible_join_keys(predicate, possible_join_keys); + let new_plan = reduce_cross_join(_optimizer, input, possible_join_keys, all_join_keys)?; + + // if there are no join keys then do nothing. + if all_join_keys.is_empty() { + Ok(plan.clone()) + } + else { + // remove join expressions from filter + match remove_join_expressions(predicate, all_join_keys)? { + Some(filter_expr) => { + Ok(LogicalPlan::Filter(Filter { + predicate: filter_expr, + input: Arc::new(new_plan), + })) + } + _ => Ok(new_plan) + } + } + } + LogicalPlan::CrossJoin(cross_join) => { + let left_plan = reduce_cross_join( + _optimizer, + &cross_join.left, + possible_join_keys, + all_join_keys, + )?; + let right_plan = reduce_cross_join( + _optimizer, + &cross_join.right, + possible_join_keys, + all_join_keys, + )?; + // can we find a match? + let left_schema = left_plan.schema(); + let right_schema = right_plan.schema(); + let mut join_keys = vec![]; + + for (l, r) in possible_join_keys { + if left_schema.field_from_column(l).is_ok() + && right_schema.field_from_column(r).is_ok() + && can_hash( + left_schema + .field_from_column(l) + .unwrap() + .data_type(), + ) + { + join_keys.push((l.clone(), r.clone())); + } else if left_schema.field_from_column(r).is_ok() + && right_schema.field_from_column(l).is_ok() + && can_hash( + left_schema + .field_from_column(r) + .unwrap() + .data_type(), + ) + { + join_keys.push((r.clone(), l.clone())); + } + } + + // if there are no join keys then do nothing. + if join_keys.is_empty() { + Ok(LogicalPlan::CrossJoin(CrossJoin { + left: Arc::new(left_plan), + right: Arc::new(right_plan), + schema: cross_join.schema.clone(), + })) + } + else { + // Keep track of join keys being pushed to Join nodes + all_join_keys.extend(join_keys.clone()); + + Ok(LogicalPlan::Join(Join { + left: Arc::new(left_plan), + right: Arc::new(right_plan), + join_type: JoinType::Inner, + join_constraint: JoinConstraint::On, + on: join_keys, + filter: None, + schema: cross_join.schema.clone(), + null_equals_null: false, + })) + } + } + _ => { + let expr = plan.expressions(); + + // apply the optimization to all inputs of the plan + let inputs = plan.inputs(); + let new_inputs = inputs + .iter() + .map(|plan| { + reduce_cross_join( + _optimizer, + plan, + possible_join_keys, + all_join_keys, + ) + }) + .collect::<Result<Vec<_>>>()?; + + from_plan(plan, &expr, &new_inputs) + } + } +} + +fn intersect( + accum: &mut Vec<(Column, Column)>, + vec1: &[(Column, Column)], + vec2: &[(Column, Column)], +) -> () { + + for x1 in vec1.iter() { + for x2 in vec2.iter() { + if x1.0 == x2.0 && x1.1 == x2.1 + || x1.1 == x2.0 && x1.0 == x2.1 + { + accum.push((x1.0.clone(), x1.1.clone())); + } + } + } + + () +} + +/// Extract join keys from a WHERE clause +fn extract_possible_join_keys( + expr: &Expr, + accum: &mut Vec<(Column, Column)>, +) -> () { + match expr { + Expr::BinaryExpr { left, op, right } => match op { + Operator::Eq => match (left.as_ref(), right.as_ref()) { + (Expr::Column(l), Expr::Column(r)) => { + // Ensure that we don't add the same Join keys multiple times + if !(accum.contains(&(l.clone(), r.clone())) || + accum.contains(&(r.clone(), l.clone()))) { + accum.push((l.clone(), r.clone())); + } + () + } + _ => (), + }, + Operator::And => { + extract_possible_join_keys(left, accum); + extract_possible_join_keys(right, accum) + }, + // Fix for issue#78 join predicates from inside of OR expr also pulled up properly. + Operator::Or => { Review Comment: Yes, I agree with @avantgardnerio -- I am fairly sure you are correct, but I would like to see a test that both removes any doubt as well as serves as protection against regression when / if this code is refactored in the future -- This is an automated message from the Apache Git Service. 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