martin-g commented on code in PR #18970: URL: https://github.com/apache/datafusion/pull/18970#discussion_r2569954357
########## datafusion/physical-expr/src/simplifier/not.rs: ########## @@ -0,0 +1,379 @@ +// 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. + +//! Simplify NOT expressions in physical expressions +//! +//! This module provides optimizations for NOT expressions such as: +//! - Double negation elimination: NOT(NOT(expr)) -> expr +//! - NOT with binary comparisons: NOT(a = b) -> a != b +//! - NOT with IN expressions: NOT(a IN (list)) -> a NOT IN (list) Review Comment: Is this really supported ? I don't see neither implementation nor tests for IN ########## datafusion/physical-expr/src/simplifier/mod.rs: ########## @@ -56,6 +57,11 @@ impl<'a> TreeNodeRewriter for PhysicalExprSimplifier<'a> { type Node = Arc<dyn PhysicalExpr>; fn f_up(&mut self, node: Self::Node) -> Result<Transformed<Self::Node>> { + // Apply NOT expression simplification first + let not_simplified = simplify_not_expr_recursive(&node, self.schema)?; Review Comment: The name of the variable is a bit confusing - `not_simplified`. It sounds like it is _not_ simplified. Maybe rename it to `not_expr_simplified` ?! ########## datafusion/physical-expr/src/simplifier/not.rs: ########## @@ -0,0 +1,379 @@ +// 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. + +//! Simplify NOT expressions in physical expressions +//! +//! This module provides optimizations for NOT expressions such as: +//! - Double negation elimination: NOT(NOT(expr)) -> expr +//! - NOT with binary comparisons: NOT(a = b) -> a != b +//! - NOT with IN expressions: NOT(a IN (list)) -> a NOT IN (list) +//! - De Morgan's laws: NOT(A AND B) -> NOT A OR NOT B +//! - Constant folding: NOT(TRUE) -> FALSE, NOT(FALSE) -> TRUE + +use std::sync::Arc; + +use arrow::datatypes::Schema; +use datafusion_common::{tree_node::Transformed, Result, ScalarValue}; +use datafusion_expr::Operator; + +use crate::expressions::{lit, BinaryExpr, Literal, NotExpr}; +use crate::PhysicalExpr; + +/// Attempts to simplify NOT expressions +pub(crate) fn simplify_not_expr( + expr: Arc<dyn PhysicalExpr>, + schema: &Schema, +) -> Result<Transformed<Arc<dyn PhysicalExpr>>> { + // Check if this is a NOT expression + let not_expr = match expr.as_any().downcast_ref::<NotExpr>() { + Some(not_expr) => not_expr, + None => return Ok(Transformed::no(expr)), + }; + + let inner_expr = not_expr.arg(); + + // Handle NOT(NOT(expr)) -> expr (double negation elimination) + if let Some(inner_not) = inner_expr.as_any().downcast_ref::<NotExpr>() { + // Recursively simplify the inner expression + let simplified = simplify_not_expr_recursive(inner_not.arg(), schema)?; + // We eliminated double negation, so always return transformed=true + return Ok(Transformed::yes(simplified.data)); + } + + // Handle NOT(literal) -> !literal + if let Some(literal) = inner_expr.as_any().downcast_ref::<Literal>() { + if let ScalarValue::Boolean(Some(val)) = literal.value() { + return Ok(Transformed::yes(lit(ScalarValue::Boolean(Some(!val))))); + } + if let ScalarValue::Boolean(None) = literal.value() { + return Ok(Transformed::yes(lit(ScalarValue::Boolean(None)))); + } + } + + // Handle NOT(binary_expr) where we can flip the operator + if let Some(binary_expr) = inner_expr.as_any().downcast_ref::<BinaryExpr>() { + if let Some(negated_op) = negate_operator(binary_expr.op()) { + // Recursively simplify the left and right expressions first + let left_simplified = + simplify_not_expr_recursive(binary_expr.left(), schema)?; + let right_simplified = + simplify_not_expr_recursive(binary_expr.right(), schema)?; + + let new_binary = Arc::new(BinaryExpr::new( + left_simplified.data, + negated_op, + right_simplified.data, + )); + // We flipped the operator, so always return transformed=true + return Ok(Transformed::yes(new_binary)); + } + + // Handle De Morgan's laws for AND/OR + match binary_expr.op() { + Operator::And => { + // NOT(A AND B) -> NOT A OR NOT B + let not_left: Arc<dyn PhysicalExpr> = + Arc::new(NotExpr::new(Arc::clone(binary_expr.left()))); + let not_right: Arc<dyn PhysicalExpr> = + Arc::new(NotExpr::new(Arc::clone(binary_expr.right()))); + + // Recursively simplify the NOT expressions + let simplified_left = simplify_not_expr_recursive(¬_left, schema)?; + let simplified_right = simplify_not_expr_recursive(¬_right, schema)?; + + let new_binary = Arc::new(BinaryExpr::new( + simplified_left.data, + Operator::Or, + simplified_right.data, + )); + return Ok(Transformed::yes(new_binary)); + } + Operator::Or => { + // NOT(A OR B) -> NOT A AND NOT B + let not_left: Arc<dyn PhysicalExpr> = + Arc::new(NotExpr::new(Arc::clone(binary_expr.left()))); + let not_right: Arc<dyn PhysicalExpr> = + Arc::new(NotExpr::new(Arc::clone(binary_expr.right()))); + + // Recursively simplify the NOT expressions + let simplified_left = simplify_not_expr_recursive(¬_left, schema)?; + let simplified_right = simplify_not_expr_recursive(¬_right, schema)?; + + let new_binary = Arc::new(BinaryExpr::new( + simplified_left.data, + Operator::And, + simplified_right.data, + )); + return Ok(Transformed::yes(new_binary)); + } + _ => {} + } + } + + // If no simplification possible, return the original expression + Ok(Transformed::no(expr)) +} + +/// Helper function that recursively simplifies expressions, including NOT expressions +pub fn simplify_not_expr_recursive( + expr: &Arc<dyn PhysicalExpr>, + schema: &Schema, +) -> Result<Transformed<Arc<dyn PhysicalExpr>>> { + // First, try to simplify any NOT expressions in this expression + let not_simplified = simplify_not_expr(Arc::clone(expr), schema)?; + + // If the expression was transformed, we might have created new opportunities for simplification + if not_simplified.transformed { + // Recursively simplify the result + let further_simplified = + simplify_not_expr_recursive(¬_simplified.data, schema)?; + if further_simplified.transformed { + return Ok(Transformed::yes(further_simplified.data)); + } else { + return Ok(not_simplified); + } + } + + // If this expression wasn't a NOT expression, try to simplify its children + // This handles cases where NOT expressions might be nested deeper in the tree + if let Some(binary_expr) = expr.as_any().downcast_ref::<BinaryExpr>() { + let left_simplified = simplify_not_expr_recursive(binary_expr.left(), schema)?; + let right_simplified = simplify_not_expr_recursive(binary_expr.right(), schema)?; + + if left_simplified.transformed || right_simplified.transformed { + let new_binary = Arc::new(BinaryExpr::new( + left_simplified.data, + *binary_expr.op(), + right_simplified.data, + )); + return Ok(Transformed::yes(new_binary)); + } + } + + Ok(not_simplified) +} + +/// Returns the negated version of a comparison operator, if possible +fn negate_operator(op: &Operator) -> Option<Operator> { + match op { + Operator::Eq => Some(Operator::NotEq), + Operator::NotEq => Some(Operator::Eq), + Operator::Lt => Some(Operator::GtEq), + Operator::LtEq => Some(Operator::Gt), + Operator::Gt => Some(Operator::LtEq), + Operator::GtEq => Some(Operator::Lt), + Operator::IsDistinctFrom => Some(Operator::IsNotDistinctFrom), + Operator::IsNotDistinctFrom => Some(Operator::IsDistinctFrom), + // For other operators, we can't directly negate them + _ => None, + } +} + +#[cfg(test)] +mod tests { + use super::*; + use crate::expressions::{col, lit, BinaryExpr, NotExpr}; + use arrow::datatypes::{DataType, Field, Schema}; + use datafusion_common::ScalarValue; + use datafusion_expr::Operator; + + fn test_schema() -> Schema { + Schema::new(vec![ + Field::new("a", DataType::Boolean, false), + Field::new("b", DataType::Int32, false), + ]) + } + + #[test] + fn test_double_negation_elimination() -> Result<()> { + let schema = test_schema(); + + // Create NOT(NOT(b > 5)) + let inner_expr: Arc<dyn PhysicalExpr> = Arc::new(BinaryExpr::new( + col("b", &schema)?, + Operator::Gt, + lit(ScalarValue::Int32(Some(5))), + )); + let inner_not = Arc::new(NotExpr::new(Arc::clone(&inner_expr))); + let double_not: Arc<dyn PhysicalExpr> = Arc::new(NotExpr::new(inner_not)); + + let result = simplify_not_expr_recursive(&double_not, &schema)?; + + assert!(result.transformed); + // Should be simplified back to the original b > 5 + assert_eq!(result.data.to_string(), inner_expr.to_string()); + Ok(()) + } + + #[test] + fn test_not_literal() -> Result<()> { + let schema = test_schema(); + + // NOT(TRUE) -> FALSE + let not_true = Arc::new(NotExpr::new(lit(ScalarValue::Boolean(Some(true))))); + let result = simplify_not_expr(not_true, &schema)?; + assert!(result.transformed); + + if let Some(literal) = result.data.as_any().downcast_ref::<Literal>() { + assert_eq!(literal.value(), &ScalarValue::Boolean(Some(false))); + } else { + panic!("Expected literal result"); + } + + // NOT(FALSE) -> TRUE + let not_false: Arc<dyn PhysicalExpr> = + Arc::new(NotExpr::new(lit(ScalarValue::Boolean(Some(false))))); + let result = simplify_not_expr_recursive(¬_false, &schema)?; + assert!(result.transformed); + + if let Some(literal) = result.data.as_any().downcast_ref::<Literal>() { + assert_eq!(literal.value(), &ScalarValue::Boolean(Some(true))); + } else { + panic!("Expected literal result"); + } + + Ok(()) + } + + #[test] + fn test_negate_comparison() -> Result<()> { + let schema = test_schema(); + + // NOT(b = 5) -> b != 5 + let eq_expr = Arc::new(BinaryExpr::new( + col("b", &schema)?, + Operator::Eq, + lit(ScalarValue::Int32(Some(5))), + )); + let not_eq: Arc<dyn PhysicalExpr> = Arc::new(NotExpr::new(eq_expr)); + + let result = simplify_not_expr_recursive(¬_eq, &schema)?; + assert!(result.transformed); + + if let Some(binary) = result.data.as_any().downcast_ref::<BinaryExpr>() { + assert_eq!(binary.op(), &Operator::NotEq); + } else { + panic!("Expected binary expression result"); + } + + Ok(()) + } + + #[test] + fn test_demorgans_law_and() -> Result<()> { + let schema = test_schema(); + + // NOT(a AND b) -> NOT a OR NOT b + let and_expr = Arc::new(BinaryExpr::new( + col("a", &schema)?, + Operator::And, + col("b", &schema)?, + )); + let not_and: Arc<dyn PhysicalExpr> = Arc::new(NotExpr::new(and_expr)); + + let result = simplify_not_expr_recursive(¬_and, &schema)?; + assert!(result.transformed); + + if let Some(binary) = result.data.as_any().downcast_ref::<BinaryExpr>() { + assert_eq!(binary.op(), &Operator::Or); + // Left and right should both be NOT expressions + assert!(binary.left().as_any().downcast_ref::<NotExpr>().is_some()); + assert!(binary.right().as_any().downcast_ref::<NotExpr>().is_some()); + } else { + panic!("Expected binary expression result"); + } + + Ok(()) + } + + #[test] + fn test_demorgans_law_or() -> Result<()> { + let schema = test_schema(); + + // NOT(a OR b) -> NOT a AND NOT b + let or_expr = Arc::new(BinaryExpr::new( + col("a", &schema)?, + Operator::Or, + col("b", &schema)?, + )); + let not_or: Arc<dyn PhysicalExpr> = Arc::new(NotExpr::new(or_expr)); + + let result = simplify_not_expr_recursive(¬_or, &schema)?; + assert!(result.transformed); + + if let Some(binary) = result.data.as_any().downcast_ref::<BinaryExpr>() { + assert_eq!(binary.op(), &Operator::And); + // Left and right should both be NOT expressions + assert!(binary.left().as_any().downcast_ref::<NotExpr>().is_some()); + assert!(binary.right().as_any().downcast_ref::<NotExpr>().is_some()); + } else { + panic!("Expected binary expression result"); + } + + Ok(()) + } + + #[test] + fn test_demorgans_with_comparison_simplification() -> Result<()> { + let schema = test_schema(); + + // NOT(b = 1 AND b = 2) -> b != 1 OR b != 2 + // This tests the combination of De Morgan's law and operator negation + let eq1 = Arc::new(BinaryExpr::new( + col("b", &schema)?, + Operator::Eq, + lit(ScalarValue::Int32(Some(1))), + )); + let eq2 = Arc::new(BinaryExpr::new( + col("b", &schema)?, + Operator::Eq, + lit(ScalarValue::Int32(Some(2))), + )); + let and_expr = Arc::new(BinaryExpr::new(eq1, Operator::And, eq2)); + let not_and: Arc<dyn PhysicalExpr> = Arc::new(NotExpr::new(and_expr)); + + let result = simplify_not_expr_recursive(¬_and, &schema)?; + assert!(result.transformed, "Expression should be transformed"); + + // Verify the result is an OR expression + if let Some(or_binary) = result.data.as_any().downcast_ref::<BinaryExpr>() { + assert_eq!(or_binary.op(), &Operator::Or, "Top level should be OR"); + + // Verify left side is b != 1 + if let Some(left_binary) = + or_binary.left().as_any().downcast_ref::<BinaryExpr>() + { + assert_eq!(left_binary.op(), &Operator::NotEq, "Left should be NotEq"); + } else { + panic!("Expected left to be a binary expression with !="); + } + + // Verify right side is b != 2 + if let Some(right_binary) = + or_binary.right().as_any().downcast_ref::<BinaryExpr>() + { + assert_eq!(right_binary.op(), &Operator::NotEq, "Right should be NotEq"); + } else { + panic!("Expected right to be a binary expression with !="); + } + } else { + panic!("Expected binary OR expression result"); + } + + Ok(()) Review Comment: Please add a test for `NOT(NOT(a) AND NOT(b))`. It should be simplified to `a OR b` but let's confirm. ########## datafusion/physical-expr/src/simplifier/not.rs: ########## @@ -0,0 +1,379 @@ +// 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. + +//! Simplify NOT expressions in physical expressions +//! +//! This module provides optimizations for NOT expressions such as: +//! - Double negation elimination: NOT(NOT(expr)) -> expr +//! - NOT with binary comparisons: NOT(a = b) -> a != b +//! - NOT with IN expressions: NOT(a IN (list)) -> a NOT IN (list) +//! - De Morgan's laws: NOT(A AND B) -> NOT A OR NOT B +//! - Constant folding: NOT(TRUE) -> FALSE, NOT(FALSE) -> TRUE + +use std::sync::Arc; + +use arrow::datatypes::Schema; +use datafusion_common::{tree_node::Transformed, Result, ScalarValue}; +use datafusion_expr::Operator; + +use crate::expressions::{lit, BinaryExpr, Literal, NotExpr}; +use crate::PhysicalExpr; + +/// Attempts to simplify NOT expressions +pub(crate) fn simplify_not_expr( + expr: Arc<dyn PhysicalExpr>, + schema: &Schema, +) -> Result<Transformed<Arc<dyn PhysicalExpr>>> { + // Check if this is a NOT expression + let not_expr = match expr.as_any().downcast_ref::<NotExpr>() { + Some(not_expr) => not_expr, + None => return Ok(Transformed::no(expr)), + }; + + let inner_expr = not_expr.arg(); + + // Handle NOT(NOT(expr)) -> expr (double negation elimination) + if let Some(inner_not) = inner_expr.as_any().downcast_ref::<NotExpr>() { + // Recursively simplify the inner expression + let simplified = simplify_not_expr_recursive(inner_not.arg(), schema)?; + // We eliminated double negation, so always return transformed=true + return Ok(Transformed::yes(simplified.data)); + } + + // Handle NOT(literal) -> !literal + if let Some(literal) = inner_expr.as_any().downcast_ref::<Literal>() { + if let ScalarValue::Boolean(Some(val)) = literal.value() { + return Ok(Transformed::yes(lit(ScalarValue::Boolean(Some(!val))))); + } + if let ScalarValue::Boolean(None) = literal.value() { + return Ok(Transformed::yes(lit(ScalarValue::Boolean(None)))); Review Comment: Should this return Transformed::yes ? It returns the same value. -- 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] --------------------------------------------------------------------- To unsubscribe, e-mail: [email protected] For additional commands, e-mail: [email protected]
