matthewgapp commented on code in PR #8840: URL: https://github.com/apache/arrow-datafusion/pull/8840#discussion_r1468204446
########## datafusion/physical-plan/src/recursive_query.rs: ########## @@ -0,0 +1,373 @@ +// 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. + +//! Defines the recursive query plan + +use std::any::Any; +use std::sync::Arc; +use std::task::{Context, Poll}; + +use super::expressions::PhysicalSortExpr; +use super::metrics::BaselineMetrics; +use super::RecordBatchStream; +use super::{ + metrics::{ExecutionPlanMetricsSet, MetricsSet}, + work_table::{WorkTable, WorkTableExec}, + SendableRecordBatchStream, Statistics, +}; + +use arrow::datatypes::SchemaRef; +use arrow::record_batch::RecordBatch; +use datafusion_common::tree_node::{Transformed, TreeNode}; +use datafusion_common::{not_impl_err, DataFusionError, Result}; +use datafusion_execution::TaskContext; +use datafusion_physical_expr::Partitioning; +use futures::{ready, Stream, StreamExt}; + +use crate::{DisplayAs, DisplayFormatType, ExecutionPlan}; + +/// Recursive query execution plan. +/// +/// This plan has two components: a base part (the static term) and +/// a dynamic part (the recursive term). The execution will start from +/// the base, and as long as the previous iteration produced at least +/// a single new row (taking care of the distinction) the recursive +/// part will be continuously executed. +/// +/// Before each execution of the dynamic part, the rows from the previous +/// iteration will be available in a "working table" (not a real table, +/// can be only accessed using a continuance operation). +/// +/// Note that there won't be any limit or checks applied to detect +/// an infinite recursion, so it is up to the planner to ensure that +/// it won't happen. +#[derive(Debug)] +pub struct RecursiveQueryExec { + /// Name of the query handler + name: String, + /// The working table of cte + work_table: Arc<WorkTable>, + /// The base part (static term) + static_term: Arc<dyn ExecutionPlan>, + /// The dynamic part (recursive term) + recursive_term: Arc<dyn ExecutionPlan>, + /// Distinction + is_distinct: bool, + /// Execution metrics + metrics: ExecutionPlanMetricsSet, +} + +impl RecursiveQueryExec { + /// Create a new RecursiveQueryExec + pub fn try_new( + name: String, + static_term: Arc<dyn ExecutionPlan>, + recursive_term: Arc<dyn ExecutionPlan>, + is_distinct: bool, + ) -> Result<Self> { + // Each recursive query needs its own work table + let work_table = Arc::new(WorkTable::new()); + // Use the same work table for both the WorkTableExec and the recursive term + let recursive_term = assign_work_table(recursive_term, work_table.clone())?; + Ok(RecursiveQueryExec { + name, + static_term, + recursive_term, + is_distinct, + work_table, + metrics: ExecutionPlanMetricsSet::new(), + }) + } +} + +impl ExecutionPlan for RecursiveQueryExec { + fn as_any(&self) -> &dyn Any { + self + } + + fn schema(&self) -> SchemaRef { + self.static_term.schema() + } + + fn children(&self) -> Vec<Arc<dyn ExecutionPlan>> { + vec![self.static_term.clone(), self.recursive_term.clone()] + } + + // Distribution on a recursive query is really tricky to handle. + // For now, we are going to use a single partition but in the + // future we might find a better way to handle this. + fn output_partitioning(&self) -> Partitioning { + Partitioning::UnknownPartitioning(1) + } + + // TODO: control these hints and see whether we can + // infer some from the child plans (static/recurisve terms). + fn maintains_input_order(&self) -> Vec<bool> { + vec![false, false] + } + + fn benefits_from_input_partitioning(&self) -> Vec<bool> { + vec![false, false] + } + + fn required_input_distribution(&self) -> Vec<datafusion_physical_expr::Distribution> { + vec![ + datafusion_physical_expr::Distribution::SinglePartition, + datafusion_physical_expr::Distribution::SinglePartition, + ] + } + + fn output_ordering(&self) -> Option<&[PhysicalSortExpr]> { + None + } + + fn with_new_children( + self: Arc<Self>, + children: Vec<Arc<dyn ExecutionPlan>>, + ) -> Result<Arc<dyn ExecutionPlan>> { + Ok(Arc::new(RecursiveQueryExec { + name: self.name.clone(), + static_term: children[0].clone(), + recursive_term: children[1].clone(), + is_distinct: self.is_distinct, + work_table: self.work_table.clone(), + metrics: self.metrics.clone(), + })) + } + + fn execute( + &self, + partition: usize, + context: Arc<TaskContext>, + ) -> Result<SendableRecordBatchStream> { + // TODO: we might be able to handle multiple partitions in the future. + if partition != 0 { + return Err(DataFusionError::Internal(format!( + "RecursiveQueryExec got an invalid partition {} (expected 0)", + partition + ))); + } + + let static_stream = self.static_term.execute(partition, context.clone())?; + let baseline_metrics = BaselineMetrics::new(&self.metrics, partition); + Ok(Box::pin(RecursiveQueryStream::new( + context, + self.work_table.clone(), + self.recursive_term.clone(), + static_stream, + baseline_metrics, + ))) + } + + fn metrics(&self) -> Option<MetricsSet> { + Some(self.metrics.clone_inner()) + } + + fn statistics(&self) -> Result<Statistics> { + Ok(Statistics::new_unknown(&self.schema())) + } +} + +impl DisplayAs for RecursiveQueryExec { + fn fmt_as( + &self, + t: DisplayFormatType, + f: &mut std::fmt::Formatter, + ) -> std::fmt::Result { + match t { + DisplayFormatType::Default | DisplayFormatType::Verbose => { + write!(f, "RecursiveQueryExec: is_distinct={}", self.is_distinct) Review Comment: done -- This is an automated message from the Apache Git Service. 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