xudong963 commented on code in PR #2858: URL: https://github.com/apache/arrow-datafusion/pull/2858#discussion_r927636440
########## datafusion/optimizer/src/rewrite_disjunctive_predicate.rs: ########## @@ -0,0 +1,429 @@ +// 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 crate::{OptimizerConfig, OptimizerRule}; +use datafusion_common::Result; +use datafusion_expr::logical_plan::Filter; +use datafusion_expr::utils::from_plan; +use datafusion_expr::Expr::BinaryExpr; +use datafusion_expr::{Expr, LogicalPlan, Operator}; +use std::sync::Arc; + +#[derive(Clone, PartialEq, Debug)] +enum Predicate { + And { args: Vec<Predicate> }, + Or { args: Vec<Predicate> }, + Other { expr: Box<Expr> }, +} + +fn predicate(expr: &Expr) -> Result<Predicate> { + match expr { + BinaryExpr { left, op, right } => match op { + Operator::And => { + let args = vec![predicate(left)?, predicate(right)?]; + Ok(Predicate::And { args }) + } + Operator::Or => { + let args = vec![predicate(left)?, predicate(right)?]; + Ok(Predicate::Or { args }) + } + _ => Ok(Predicate::Other { + expr: Box::new(BinaryExpr { + left: left.clone(), + op: *op, + right: right.clone(), + }), + }), + }, + _ => Ok(Predicate::Other { + expr: Box::new(expr.clone()), + }), + } +} + +fn normalize_predicate(predicate: &Predicate) -> Expr { + match predicate { + Predicate::And { args } => { + assert!(args.len() >= 2); + let left = normalize_predicate(&args[0]); + let right = normalize_predicate(&args[1]); + let mut and_expr = BinaryExpr { + left: Box::new(left), + op: Operator::And, + right: Box::new(right), + }; + for arg in args.iter().skip(2) { + and_expr = BinaryExpr { + left: Box::new(and_expr), + op: Operator::And, + right: Box::new(normalize_predicate(arg)), + }; + } + and_expr + } + Predicate::Or { args } => { + assert!(args.len() >= 2); + let left = normalize_predicate(&args[0]); + let right = normalize_predicate(&args[1]); + let mut or_expr = BinaryExpr { + left: Box::new(left), + op: Operator::Or, + right: Box::new(right), + }; + for arg in args.iter().skip(2) { + or_expr = BinaryExpr { + left: Box::new(or_expr), + op: Operator::Or, + right: Box::new(normalize_predicate(arg)), + }; + } + or_expr + } + Predicate::Other { expr } => *expr.clone(), + } +} + +fn rewrite_predicate(predicate: &Predicate) -> Predicate { + match predicate { + Predicate::And { args } => { + let mut rewritten_args = Vec::with_capacity(args.len()); + for arg in args.iter() { + rewritten_args.push(rewrite_predicate(arg)); + } + rewritten_args = flatten_and_predicates(&rewritten_args); + Predicate::And { + args: rewritten_args, + } + } + Predicate::Or { args } => { + let mut rewritten_args = vec![]; + for arg in args.iter() { + rewritten_args.push(rewrite_predicate(arg)); + } + rewritten_args = flatten_or_predicates(&rewritten_args); + delete_duplicate_predicates(&rewritten_args) + } + Predicate::Other { expr } => Predicate::Other { + expr: Box::new(*expr.clone()), + }, + } +} + +fn flatten_and_predicates(and_predicates: &[Predicate]) -> Vec<Predicate> { + let mut flattened_predicates = vec![]; + for predicate in and_predicates { + match predicate { + Predicate::And { args } => { + flattened_predicates + .extend_from_slice(flatten_and_predicates(args).as_slice()); + } + _ => { + flattened_predicates.push(predicate.clone()); + } + } + } + flattened_predicates +} + +fn flatten_or_predicates(or_predicates: &[Predicate]) -> Vec<Predicate> { + let mut flattened_predicates = vec![]; + for predicate in or_predicates { + match predicate { + Predicate::Or { args } => { + flattened_predicates + .extend_from_slice(flatten_or_predicates(args).as_slice()); + } + _ => { + flattened_predicates.push(predicate.clone()); + } + } + } + flattened_predicates +} + +fn delete_duplicate_predicates(or_predicates: &[Predicate]) -> Predicate { + let mut shortest_exprs: Vec<Predicate> = vec![]; + let mut shortest_exprs_len = 0; + // choose the shortest AND predicate Review Comment: > I don't understand the need for checking the shortest AND predicate The shortest AND predicate could be the common expression to be extracted if each of its elements appears in all OR predicates. > why not check all elements We don't need to check all elements, only the shortest could be the common expression. > keeping a set of expressions Yes, `shortest_exprs` should be a `HashSet`, but to avoid implementing `Eq` and `Hash`(it'll be spread deeply), I use `Vec` instead. -- 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]
