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. 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