Dandandan commented on a change in pull request #11: URL: https://github.com/apache/arrow-datafusion/pull/11#discussion_r616938595
########## File path: datafusion/src/physical_plan/cross_join.rs ########## @@ -0,0 +1,315 @@ +// 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 join plan for executing partitions in parallel and then joining the results +//! into a set of partitions. + +use futures::{lock::Mutex, StreamExt}; +use std::{any::Any, sync::Arc, task::Poll}; + +use crate::physical_plan::memory::MemoryStream; +use arrow::datatypes::{Schema, SchemaRef}; +use arrow::error::Result as ArrowResult; +use arrow::record_batch::RecordBatch; + +use futures::{Stream, TryStreamExt}; + +use super::{hash_utils::check_join_is_valid, merge::MergeExec}; +use crate::{ + error::{DataFusionError, Result}, + scalar::ScalarValue, +}; +use async_trait::async_trait; +use std::time::Instant; + +use super::{ExecutionPlan, Partitioning, RecordBatchStream, SendableRecordBatchStream}; +use crate::physical_plan::coalesce_batches::concat_batches; +use log::debug; + +/// Data of the left side +type JoinLeftData = RecordBatch; + +/// executes partitions in parallel and combines them into a set of +/// partitions by combining all values from the left with all values on the right +#[derive(Debug)] +pub struct CrossJoinExec { + /// left (build) side which gets loaded in memory + left: Arc<dyn ExecutionPlan>, + /// right (probe) side which are combined with left side + right: Arc<dyn ExecutionPlan>, + /// The schema once the join is applied + schema: SchemaRef, + /// Build-side data + build_side: Arc<Mutex<Option<JoinLeftData>>>, +} + +impl CrossJoinExec { + /// Tries to create a new [CrossJoinExec]. + /// # Error + /// This function errors when it is not possible to join the left and right sides on keys `on`. + pub fn try_new( + left: Arc<dyn ExecutionPlan>, + right: Arc<dyn ExecutionPlan>, + ) -> Result<Self> { + let left_schema = left.schema(); + let right_schema = right.schema(); + check_join_is_valid(&left_schema, &right_schema, &[])?; + + let left_schema = left.schema(); + let left_fields = left_schema.fields().iter(); + let right_schema = right.schema(); + + let right_fields = right_schema.fields().iter(); + + // left then right + let all_columns = left_fields.chain(right_fields).cloned().collect(); + + let schema = Arc::new(Schema::new(all_columns)); + + Ok(CrossJoinExec { + left, + right, + schema, + build_side: Arc::new(Mutex::new(None)), + }) + } + + /// left (build) side which gets loaded in memory + pub fn left(&self) -> &Arc<dyn ExecutionPlan> { + &self.left + } + + /// right side which gets combined with left side + pub fn right(&self) -> &Arc<dyn ExecutionPlan> { + &self.right + } +} + +#[async_trait] +impl ExecutionPlan for CrossJoinExec { + fn as_any(&self) -> &dyn Any { + self + } + + fn schema(&self) -> SchemaRef { + self.schema.clone() + } + + fn children(&self) -> Vec<Arc<dyn ExecutionPlan>> { + vec![self.left.clone(), self.right.clone()] + } + + fn with_new_children( + &self, + children: Vec<Arc<dyn ExecutionPlan>>, + ) -> Result<Arc<dyn ExecutionPlan>> { + match children.len() { + 2 => Ok(Arc::new(CrossJoinExec::try_new( + children[0].clone(), + children[1].clone(), + )?)), + _ => Err(DataFusionError::Internal( + "CrossJoinExec wrong number of children".to_string(), + )), + } + } + + fn output_partitioning(&self) -> Partitioning { + self.right.output_partitioning() + } + + async fn execute(&self, partition: usize) -> Result<SendableRecordBatchStream> { + // we only want to compute the build side once + let left_data = { + let mut build_side = self.build_side.lock().await; + + match build_side.as_ref() { + Some(stream) => stream.clone(), + None => { + let start = Instant::now(); + + // merge all left parts into a single stream + let merge = MergeExec::new(self.left.clone()); + let stream = merge.execute(0).await?; + + // Load all batches and count the rows + let (batches, num_rows) = stream + .try_fold((Vec::new(), 0usize), |mut acc, batch| async { + acc.1 += batch.num_rows(); + acc.0.push(batch); + Ok(acc) + }) + .await?; + let merged_batch = + concat_batches(&self.left.schema(), &batches, num_rows)?; + *build_side = Some(merged_batch.clone()); + + debug!( + "Built build-side of cross join containing {} rows in {} ms", + num_rows, + start.elapsed().as_millis() + ); + + merged_batch + } + } + }; + + let stream = self.right.execute(partition).await?; + + if left_data.num_rows() == 0 { + return Ok(Box::pin(MemoryStream::try_new( + vec![], + self.schema.clone(), + None, + )?)); + } + + Ok(Box::pin(CrossJoinStream { + schema: self.schema.clone(), + left_data, + right: stream, + right_batch: Arc::new(std::sync::Mutex::new(None)), + left_index: 0, + num_input_batches: 0, + num_input_rows: 0, + num_output_batches: 0, + num_output_rows: 0, + join_time: 0, + })) + } +} + +/// A stream that issues [RecordBatch]es as they arrive from the right of the join. +struct CrossJoinStream { + /// Input schema + schema: Arc<Schema>, + /// data from the left side + left_data: JoinLeftData, + /// right + right: SendableRecordBatchStream, + /// Current value on the left + left_index: usize, + /// Current batch being processed from the right side + right_batch: Arc<std::sync::Mutex<Option<RecordBatch>>>, Review comment: Also some more context here https://users.rust-lang.org/t/std-mutex-vs-futures-mutex-vs-futures-lock-mutex-for-async/41710/4 -- This is an automated message from the Apache Git Service. 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