pantShrey commented on code in PR #21882: URL: https://github.com/apache/datafusion/pull/21882#discussion_r3214836201
########## datafusion/execution/src/spill_file.rs: ########## @@ -0,0 +1,71 @@ +// 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 bytes::Bytes; +use datafusion_common::Result; +use futures::Stream; +use std::path::Path; +use std::pin::Pin; +use std::sync::Arc; + +/// Abstraction over a spill file backend. +/// Implementations handle their own quota enforcement and blocking concerns. +pub trait SpillFile: Send + Sync { + /// Returns the OS path if this is a local file, None otherwise. + fn path(&self) -> Option<&Path> { + None + } + + /// Returns current size in bytes if cheaply available. + fn size(&self) -> Option<u64>; + + /// Returns file contents as an async stream of byte chunks. + fn read_stream(&self) -> Result<Pin<Box<dyn Stream<Item = Result<Bytes>> + Send>>>; + + /// Opens a writer for appending data to this file. + fn open_writer(&self) -> Result<Box<dyn SpillWriter>>; + + /// Opens a synchronous reader for this file. + /// Used by legacy operators (like SortMergeJoin) that haven't been fully migrated to async. + /// + /// Backends that only support async reads should leave this default implementation, + /// which will safely return a NotImplemented error if used in synchronous contexts. + fn open_sync_reader(&self) -> Result<Box<dyn std::io::Read + Send>> { + datafusion_common::exec_err!( + "Synchronous reads are not supported by this spill backend. \ + This backend cannot be used with synchronous operators like SortMergeJoin \ + until they are refactored to be fully asynchronous." + ) + } +} + +/// Writer for spill file backends. +/// Receives zero-copy `Bytes` payloads from the IPCStreamWriter adapter. +pub trait SpillWriter: Send { + fn write(&mut self, data: Bytes) -> Result<()>; Review Comment: Yes, you are right. The reason I didn't use Write trait which uses &[u8] was for ownership reasons. Some backends might queue chunks to a background task (e.g., S3 multipart via a channel) and need to hold the data past the write() call's return. &[u8] can't express that, and it would force a second copy between the SpillWriteAdapter and the SpillWriter. Also, the custom SpillWriter trait contains finish(), which maps perfectly to complete_multipart_upload for S3 and resource owner cleanup for Postgres. -- 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]
