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fix: detect non-recursive CTEs in the recursive
WITH clause (#9836)
* move cte related logic to its own mod * fix check cte self reference * add tests * fix test * move test to slt
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| // 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 std::sync::Arc; | ||
|
|
||
| use crate::planner::{ContextProvider, PlannerContext, SqlToRel}; | ||
|
|
||
| use arrow::datatypes::Schema; | ||
| use datafusion_common::{ | ||
| not_impl_err, plan_err, | ||
| tree_node::{TreeNode, TreeNodeRecursion}, | ||
| Result, | ||
| }; | ||
| use datafusion_expr::{LogicalPlan, LogicalPlanBuilder, TableSource}; | ||
| use sqlparser::ast::{Query, SetExpr, SetOperator, With}; | ||
|
|
||
| impl<'a, S: ContextProvider> SqlToRel<'a, S> { | ||
| pub(super) fn plan_with_clause( | ||
| &self, | ||
| with: With, | ||
| planner_context: &mut PlannerContext, | ||
| ) -> Result<()> { | ||
| let is_recursive = with.recursive; | ||
| // Process CTEs from top to bottom | ||
| for cte in with.cte_tables { | ||
| // A `WITH` block can't use the same name more than once | ||
| let cte_name = self.normalizer.normalize(cte.alias.name.clone()); | ||
| if planner_context.contains_cte(&cte_name) { | ||
| return plan_err!( | ||
| "WITH query name {cte_name:?} specified more than once" | ||
| ); | ||
| } | ||
|
|
||
| // Create a logical plan for the CTE | ||
| let cte_plan = if is_recursive { | ||
| self.recursive_cte(cte_name.clone(), *cte.query, planner_context)? | ||
| } else { | ||
| self.non_recursive_cte(*cte.query, planner_context)? | ||
| }; | ||
|
|
||
| // Each `WITH` block can change the column names in the last | ||
| // projection (e.g. "WITH table(t1, t2) AS SELECT 1, 2"). | ||
| let final_plan = self.apply_table_alias(cte_plan, cte.alias)?; | ||
| // Export the CTE to the outer query | ||
| planner_context.insert_cte(cte_name, final_plan); | ||
| } | ||
| Ok(()) | ||
| } | ||
|
|
||
| fn non_recursive_cte( | ||
| &self, | ||
| cte_query: Query, | ||
| planner_context: &mut PlannerContext, | ||
| ) -> Result<LogicalPlan> { | ||
| // CTE expr don't need extend outer_query_schema, | ||
| // so we clone a new planner_context here. | ||
| let mut cte_planner_context = planner_context.clone(); | ||
| self.query_to_plan(cte_query, &mut cte_planner_context) | ||
| } | ||
|
|
||
| fn recursive_cte( | ||
| &self, | ||
| cte_name: String, | ||
| mut cte_query: Query, | ||
| planner_context: &mut PlannerContext, | ||
| ) -> Result<LogicalPlan> { | ||
| if !self | ||
| .context_provider | ||
| .options() | ||
| .execution | ||
| .enable_recursive_ctes | ||
| { | ||
| return not_impl_err!("Recursive CTEs are not enabled"); | ||
| } | ||
|
|
||
| let (left_expr, right_expr, set_quantifier) = match *cte_query.body { | ||
| SetExpr::SetOperation { | ||
| op: SetOperator::Union, | ||
| left, | ||
| right, | ||
| set_quantifier, | ||
| } => (left, right, set_quantifier), | ||
| other => { | ||
| // If the query is not a UNION, then it is not a recursive CTE | ||
| cte_query.body = Box::new(other); | ||
| return self.non_recursive_cte(cte_query, planner_context); | ||
| } | ||
| }; | ||
|
|
||
| // Each recursive CTE consists from two parts in the logical plan: | ||
| // 1. A static term (the left hand side on the SQL, where the | ||
| // referencing to the same CTE is not allowed) | ||
| // | ||
| // 2. A recursive term (the right hand side, and the recursive | ||
| // part) | ||
|
|
||
| // Since static term does not have any specific properties, it can | ||
| // be compiled as if it was a regular expression. This will | ||
| // allow us to infer the schema to be used in the recursive term. | ||
|
|
||
| // ---------- Step 1: Compile the static term ------------------ | ||
| let static_plan = | ||
| self.set_expr_to_plan(*left_expr, &mut planner_context.clone())?; | ||
|
|
||
| // Since the recursive CTEs include a component that references a | ||
| // table with its name, like the example below: | ||
| // | ||
| // WITH RECURSIVE values(n) AS ( | ||
| // SELECT 1 as n -- static term | ||
| // UNION ALL | ||
| // SELECT n + 1 | ||
| // FROM values -- self reference | ||
| // WHERE n < 100 | ||
| // ) | ||
| // | ||
| // We need a temporary 'relation' to be referenced and used. PostgreSQL | ||
| // calls this a 'working table', but it is entirely an implementation | ||
| // detail and a 'real' table with that name might not even exist (as | ||
| // in the case of DataFusion). | ||
| // | ||
| // Since we can't simply register a table during planning stage (it is | ||
| // an execution problem), we'll use a relation object that preserves the | ||
| // schema of the input perfectly and also knows which recursive CTE it is | ||
| // bound to. | ||
|
|
||
| // ---------- Step 2: Create a temporary relation ------------------ | ||
| // Step 2.1: Create a table source for the temporary relation | ||
| let work_table_source = self.context_provider.create_cte_work_table( | ||
| &cte_name, | ||
| Arc::new(Schema::from(static_plan.schema().as_ref())), | ||
| )?; | ||
|
|
||
| // Step 2.2: Create a temporary relation logical plan that will be used | ||
| // as the input to the recursive term | ||
| let work_table_plan = LogicalPlanBuilder::scan( | ||
| cte_name.to_string(), | ||
| work_table_source.clone(), | ||
| None, | ||
| )? | ||
| .build()?; | ||
|
|
||
| let name = cte_name.clone(); | ||
|
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||
| // Step 2.3: Register the temporary relation in the planning context | ||
| // For all the self references in the variadic term, we'll replace it | ||
| // with the temporary relation we created above by temporarily registering | ||
| // it as a CTE. This temporary relation in the planning context will be | ||
| // replaced by the actual CTE plan once we're done with the planning. | ||
| planner_context.insert_cte(cte_name.clone(), work_table_plan); | ||
|
|
||
| // ---------- Step 3: Compile the recursive term ------------------ | ||
| // this uses the named_relation we inserted above to resolve the | ||
| // relation. This ensures that the recursive term uses the named relation logical plan | ||
| // and thus the 'continuance' physical plan as its input and source | ||
| let recursive_plan = | ||
| self.set_expr_to_plan(*right_expr, &mut planner_context.clone())?; | ||
|
|
||
| // Check if the recursive term references the CTE itself, | ||
| // if not, it is a non-recursive CTE | ||
| if !has_work_table_reference(&recursive_plan, &work_table_source) { | ||
| // Remove the work table plan from the context | ||
| planner_context.remove_cte(&cte_name); | ||
| // Compile it as a non-recursive CTE | ||
| return self.set_operation_to_plan( | ||
| SetOperator::Union, | ||
| static_plan, | ||
| recursive_plan, | ||
| set_quantifier, | ||
| ); | ||
| } | ||
|
|
||
| // ---------- Step 4: Create the final plan ------------------ | ||
| // Step 4.1: Compile the final plan | ||
| let distinct = !Self::is_union_all(set_quantifier)?; | ||
| LogicalPlanBuilder::from(static_plan) | ||
| .to_recursive_query(name, recursive_plan, distinct)? | ||
| .build() | ||
| } | ||
| } | ||
|
|
||
| fn has_work_table_reference( | ||
| plan: &LogicalPlan, | ||
| work_table_source: &Arc<dyn TableSource>, | ||
| ) -> bool { | ||
| let mut has_reference = false; | ||
| plan.apply(&mut |node| { | ||
| if let LogicalPlan::TableScan(scan) = node { | ||
| if Arc::ptr_eq(&scan.source, work_table_source) { | ||
| has_reference = true; | ||
| return Ok(TreeNodeRecursion::Stop); | ||
| } | ||
| } | ||
| Ok(TreeNodeRecursion::Continue) | ||
| }) | ||
| // Closure always return Ok | ||
| .unwrap(); | ||
| has_reference | ||
| } |
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