mingmwang commented on code in PR #6084: URL: https://github.com/apache/arrow-datafusion/pull/6084#discussion_r1177422260
########## datafusion/optimizer/src/analyzer/subquery.rs: ########## @@ -0,0 +1,340 @@ +// 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::analyzer::check_plan; +use crate::utils::{collect_subquery_cols, split_conjunction}; +use datafusion_common::tree_node::{TreeNode, VisitRecursion}; +use datafusion_common::{DataFusionError, Result}; +use datafusion_expr::expr_rewriter::strip_outer_reference; +use datafusion_expr::{ + Aggregate, BinaryExpr, Cast, Expr, Filter, Join, JoinType, LogicalPlan, Operator, + Window, +}; +use std::ops::Deref; + +/// Do necessary check on subquery expressions and fail the invalid plan +/// 1) Check whether the outer plan is in the allowed outer plans list to use subquery expressions, +/// the allowed while list: [Projection, Filter, Window, Aggregate, Join]. +/// 2) Check whether the inner plan is in the allowed inner plans list to use correlated(outer) expressions. +/// 3) Check and validate unsupported cases to use the correlated(outer) expressions inside the subquery(inner) plans/inner expressions. +/// For example, we do not want to support to use correlated expressions as the Join conditions in the subquery plan when the Join +/// is a Full Out Join +pub fn check_subquery_expr( + outer_plan: &LogicalPlan, + inner_plan: &LogicalPlan, + expr: &Expr, +) -> Result<()> { + check_plan(inner_plan)?; + if let Expr::ScalarSubquery(subquery) = expr { + // Scalar subquery should only return one column + if subquery.subquery.schema().fields().len() > 1 { + return Err(datafusion_common::DataFusionError::Plan( + "Scalar subquery should only return one column".to_string(), + )); + } + // Correlated scalar subquery must be aggregated to return at most one row + if !subquery.outer_ref_columns.is_empty() { + match strip_inner_query(inner_plan) { + LogicalPlan::Aggregate(agg) => { + check_aggregation_in_scalar_subquery(inner_plan, agg) + } + LogicalPlan::Filter(Filter { input, .. }) + if matches!(input.as_ref(), LogicalPlan::Aggregate(_)) => + { + if let LogicalPlan::Aggregate(agg) = input.as_ref() { + check_aggregation_in_scalar_subquery(inner_plan, agg) + } else { + Ok(()) + } + } + _ => { + if inner_plan + .max_rows() + .filter(|max_row| *max_row <= 1) + .is_some() + { + Ok(()) + } else { + Err(DataFusionError::Plan( + "Correlated scalar subquery must be aggregated to return at most one row" + .to_string(), + )) + } + } + }?; + match outer_plan { + LogicalPlan::Projection(_) + | LogicalPlan::Filter(_) => Ok(()), + LogicalPlan::Aggregate(Aggregate {group_expr, aggr_expr,..}) => { + if group_expr.contains(expr) && !aggr_expr.contains(expr) { + // TODO revisit this validation logic + Err(DataFusionError::Plan( + "Correlated scalar subquery in the GROUP BY clause must also be in the aggregate expressions" + .to_string(), + )) + } else { + Ok(()) + } + }, + _ => Err(DataFusionError::Plan( + "Correlated scalar subquery can only be used in Projection, Filter, Aggregate plan nodes" + .to_string(), + )) + }?; + } + check_correlations_in_subquery(inner_plan, true) + } else { + match outer_plan { + LogicalPlan::Projection(_) + | LogicalPlan::Filter(_) + | LogicalPlan::Window(_) + | LogicalPlan::Aggregate(_) + | LogicalPlan::Join(_) => Ok(()), + _ => Err(DataFusionError::Plan( + "In/Exist subquery can only be used in \ + Projection, Filter, Window functions, Aggregate and Join plan nodes" + .to_string(), + )), + }?; + check_correlations_in_subquery(inner_plan, false) + } +} + +// Recursively check the unsupported outer references in the sub query plan. +fn check_correlations_in_subquery( + inner_plan: &LogicalPlan, + is_scalar: bool, +) -> Result<()> { + check_inner_plan(inner_plan, is_scalar, false, true) +} + +// Recursively check the unsupported outer references in the sub query plan. +fn check_inner_plan( + inner_plan: &LogicalPlan, + is_scalar: bool, + is_aggregate: bool, + can_contain_outer_ref: bool, +) -> Result<()> { + if !can_contain_outer_ref && contains_outer_reference(inner_plan) { + return Err(DataFusionError::Plan( + "Accessing outer reference columns is not allowed in the plan".to_string(), + )); + } + // We want to support as many operators as possible inside the correlated subquery + match inner_plan { + LogicalPlan::Aggregate(_) => { + inner_plan.apply_children(&mut |plan| { + check_inner_plan(plan, is_scalar, true, can_contain_outer_ref)?; + Ok(VisitRecursion::Continue) + })?; + Ok(()) + } + LogicalPlan::Filter(Filter { + predicate, input, .. + }) => { + let (correlated, _): (Vec<_>, Vec<_>) = split_conjunction(predicate) + .into_iter() + .partition(|e| e.contains_outer()); + let maybe_unsupport = correlated + .into_iter() + .filter(|expr| !can_pullup_over_aggregation(expr)) + .collect::<Vec<_>>(); + if is_aggregate && is_scalar && !maybe_unsupport.is_empty() { + return Err(DataFusionError::Plan(format!( + "Correlated column is not allowed in predicate: {:?}", + predicate + ))); + } + check_inner_plan(input, is_scalar, is_aggregate, can_contain_outer_ref) + } + LogicalPlan::Window(window) => { + check_mixed_out_refer_in_window(window)?; + inner_plan.apply_children(&mut |plan| { + check_inner_plan(plan, is_scalar, is_aggregate, can_contain_outer_ref)?; + Ok(VisitRecursion::Continue) + })?; + Ok(()) + } + LogicalPlan::Projection(_) + | LogicalPlan::Distinct(_) + | LogicalPlan::Sort(_) + | LogicalPlan::CrossJoin(_) + | LogicalPlan::Union(_) + | LogicalPlan::TableScan(_) + | LogicalPlan::EmptyRelation(_) + | LogicalPlan::Limit(_) + | LogicalPlan::Values(_) + | LogicalPlan::Subquery(_) + | LogicalPlan::SubqueryAlias(_) => { + inner_plan.apply_children(&mut |plan| { + check_inner_plan(plan, is_scalar, is_aggregate, can_contain_outer_ref)?; + Ok(VisitRecursion::Continue) + })?; + Ok(()) + } + LogicalPlan::Join(Join { + left, + right, + join_type, + .. + }) => match join_type { + JoinType::Inner => { + inner_plan.apply_children(&mut |plan| { + check_inner_plan( + plan, + is_scalar, + is_aggregate, + can_contain_outer_ref, + )?; + Ok(VisitRecursion::Continue) + })?; + Ok(()) + } + JoinType::Left | JoinType::LeftSemi | JoinType::LeftAnti => { + check_inner_plan(left, is_scalar, is_aggregate, can_contain_outer_ref)?; + check_inner_plan(right, is_scalar, is_aggregate, false) + } + JoinType::Right | JoinType::RightSemi | JoinType::RightAnti => { + check_inner_plan(left, is_scalar, is_aggregate, false)?; + check_inner_plan(right, is_scalar, is_aggregate, can_contain_outer_ref) + } + JoinType::Full => { + inner_plan.apply_children(&mut |plan| { + check_inner_plan(plan, is_scalar, is_aggregate, false)?; + Ok(VisitRecursion::Continue) + })?; + Ok(()) + } + }, + _ => Err(DataFusionError::Plan( + "Unsupported operator in the subquery plan.".to_string(), + )), + } +} + +fn contains_outer_reference(inner_plan: &LogicalPlan) -> bool { + inner_plan + .expressions() + .iter() + .any(|expr| expr.contains_outer()) +} + +fn check_aggregation_in_scalar_subquery( + inner_plan: &LogicalPlan, + agg: &Aggregate, +) -> Result<()> { + if agg.aggr_expr.is_empty() { Review Comment: Yes. -- This is an automated message from the Apache Git Service. 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