houqp commented on a change in pull request #9309: URL: https://github.com/apache/arrow/pull/9309#discussion_r576445235
########## File path: rust/datafusion/src/optimizer/constant_folding.rs ########## @@ -0,0 +1,834 @@ +// 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. + +//! Boolean comparision rule rewrites redudant comparison expression involing boolean literal into +//! unary expression. + +use std::sync::Arc; + +use arrow::datatypes::DataType; + +use crate::error::Result; +use crate::logical_plan::{DFSchemaRef, Expr, LogicalPlan, Operator}; +use crate::optimizer::optimizer::OptimizerRule; +use crate::optimizer::utils; +use crate::scalar::ScalarValue; + +/// Optimizer that simplifies comparison expressions involving boolean literals. +/// +/// Recursively go through all expressionss and simplify the following cases: +/// * `expr = true` and `expr != false` to `expr` when `expr` is of boolean type +/// * `expr = false` and `expr != true` to `!expr` when `expr` is of boolean type +/// * `true = true` and `false = false` to `true` +/// * `false = true` and `true = false` to `false` +/// * `!!expr` to `expr` +/// * `expr = null` and `expr != null` to `null` +pub struct ConstantFolding {} + +impl ConstantFolding { + #[allow(missing_docs)] + pub fn new() -> Self { + Self {} + } +} + +impl OptimizerRule for ConstantFolding { + fn optimize(&self, plan: &LogicalPlan) -> Result<LogicalPlan> { + match plan { + LogicalPlan::Filter { predicate, input } => Ok(LogicalPlan::Filter { + predicate: optimize_expr(predicate, &plan.all_schemas())?, + input: Arc::new(self.optimize(input)?), + }), + // Rest: recurse into plan, apply optimization where possible + LogicalPlan::Projection { .. } + | LogicalPlan::Aggregate { .. } + | LogicalPlan::Repartition { .. } + | LogicalPlan::CreateExternalTable { .. } + | LogicalPlan::Extension { .. } + | LogicalPlan::Sort { .. } + | LogicalPlan::Explain { .. } + | LogicalPlan::Limit { .. } + | LogicalPlan::Join { .. } => { + // apply the optimization to all inputs of the plan + let inputs = utils::inputs(plan); + let new_inputs = inputs + .iter() + .map(|plan| self.optimize(plan)) + .collect::<Result<Vec<_>>>()?; + + let schemas = plan.all_schemas(); + let expr = utils::expressions(plan) + .iter() + .map(|e| optimize_expr(e, &schemas)) + .collect::<Result<Vec<_>>>()?; + + utils::from_plan(plan, &expr, &new_inputs) + } + LogicalPlan::TableScan { .. } | LogicalPlan::EmptyRelation { .. } => { + Ok(plan.clone()) + } + } + } + + fn name(&self) -> &str { + "constant_folding" + } +} + +fn is_boolean_type(expr: &Expr, schemas: &[&DFSchemaRef]) -> bool { + for schema in schemas { + match expr.get_type(schema) { + Ok(dt) if dt == DataType::Boolean => { + return true; + } + _ => { + continue; + } + } + } + + false +} + +/// Recursively transverses the logical plan. +fn optimize_expr(e: &Expr, schemas: &[&DFSchemaRef]) -> Result<Expr> { + Ok(match e { + Expr::BinaryExpr { left, op, right } => { + let left = optimize_expr(left, schemas)?; + let right = optimize_expr(right, schemas)?; + match op { + Operator::Eq => match (&left, &right) { + ( + Expr::Literal(ScalarValue::Boolean(l)), + Expr::Literal(ScalarValue::Boolean(r)), + ) => match (l, r) { + (Some(l), Some(r)) => { + Expr::Literal(ScalarValue::Boolean(Some(l == r))) + } + _ => Expr::Literal(ScalarValue::Boolean(None)), + }, + (Expr::Literal(ScalarValue::Boolean(b)), _) + if is_boolean_type(&right, schemas) => + { + match b { + Some(true) => right, + Some(false) => Expr::Not(Box::new(right)), + None => Expr::Literal(ScalarValue::Boolean(None)), + } + } + (_, Expr::Literal(ScalarValue::Boolean(b))) + if is_boolean_type(&left, schemas) => + { + match b { + Some(true) => left, + Some(false) => Expr::Not(Box::new(left)), + None => Expr::Literal(ScalarValue::Boolean(None)), + } + } + _ => Expr::BinaryExpr { + left: Box::new(left), + op: Operator::Eq, + right: Box::new(right), + }, + }, + Operator::NotEq => match (&left, &right) { + ( + Expr::Literal(ScalarValue::Boolean(l)), + Expr::Literal(ScalarValue::Boolean(r)), + ) => match (l, r) { + (Some(l), Some(r)) => { + Expr::Literal(ScalarValue::Boolean(Some(l != r))) + } + _ => Expr::Literal(ScalarValue::Boolean(None)), + }, + (Expr::Literal(ScalarValue::Boolean(b)), _) + if is_boolean_type(&right, schemas) => + { + match b { + Some(true) => Expr::Not(Box::new(right)), + Some(false) => right, + None => Expr::Literal(ScalarValue::Boolean(None)), + } + } + (_, Expr::Literal(ScalarValue::Boolean(b))) + if is_boolean_type(&left, schemas) => + { + match b { + Some(true) => Expr::Not(Box::new(left)), + Some(false) => left, + None => Expr::Literal(ScalarValue::Boolean(None)), + } + } + _ => Expr::BinaryExpr { + left: Box::new(left), + op: Operator::NotEq, + right: Box::new(right), + }, + }, + _ => Expr::BinaryExpr { + left: Box::new(left), + op: *op, + right: Box::new(right), + }, + } + } + Expr::Not(expr) => match &**expr { + Expr::Not(inner) => optimize_expr(&inner, schemas)?, + _ => Expr::Not(Box::new(optimize_expr(&expr, schemas)?)), + }, + Expr::Case { + expr, + when_then_expr, + else_expr, + } => { + if expr.is_none() { + // recurse into CASE WHEN condition expressions + Expr::Case { + expr: None, + when_then_expr: when_then_expr + .iter() + .map(|(when, then)| { + Ok(( + Box::new(optimize_expr(when, schemas)?), + Box::new(optimize_expr(then, schemas)?), + )) + }) + .collect::<Result<_>>()?, + else_expr: match else_expr { + Some(e) => Some(Box::new(optimize_expr(e, schemas)?)), + None => None, + }, + } + } else { + // when base expression is specified, when_then_expr conditions are literal values + // so we can just skip this case + e.clone() Review comment: This is based on the doc string we have in `logical_plan/expr.rs`: ``` The second form uses a base expression and then a series of "when" clauses that match on a literal value. `` However, general SQL and spark SQL does support arbitrary expressions in when conditions, so I think it's best for us to match that behavior. ---------------------------------------------------------------- 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. For queries about this service, please contact Infrastructure at: us...@infra.apache.org
