houqp commented on a change in pull request #950: URL: https://github.com/apache/arrow-datafusion/pull/950#discussion_r697552520
########## File path: datafusion/src/datasource/object_store/local.rs ########## @@ -0,0 +1,127 @@ +// 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. + +//! Object store that represents the Local File System. + +use std::fs::Metadata; +use std::sync::Arc; + +use async_trait::async_trait; +use futures::{stream, AsyncRead, StreamExt}; + +use crate::datasource::object_store::{ + FileMeta, FileMetaStream, ObjectReader, ObjectStore, +}; +use crate::error::DataFusionError; +use crate::error::Result; +use crate::logical_plan::Expr; + +#[derive(Debug)] +/// Local File System as Object Store. +pub struct LocalFileSystem; + +#[async_trait] +impl ObjectStore for LocalFileSystem { + async fn list(&self, prefix: &str, _filters: &[Expr]) -> Result<FileMetaStream> { + list_all(prefix.to_owned()).await + } + + fn get_reader(&self, file: FileMeta) -> Result<Arc<dyn ObjectReader>> { + Ok(Arc::new(LocalFileReader::new(file)?)) + } +} + +struct LocalFileReader { + file: FileMeta, +} + +impl LocalFileReader { + fn new(file: FileMeta) -> Result<Self> { + Ok(Self { file }) + } +} + +#[async_trait] +impl ObjectReader for LocalFileReader { + async fn get_reader( Review comment: Maybe we should keep `ObjectStore::get_reader` as async? Otherwise, it looks like every call to `ObjectReader::get_reader` would need to open a new file descriptor. We may want to change `ObjectReader::get_reader` to take `self` as `&mut` so an object reader can implement caching and look ahead read behind the scene. ########## File path: datafusion/src/datasource/object_store/mod.rs ########## @@ -0,0 +1,130 @@ +// 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. + +//! Object Store abstracts access to an underlying file/object storage. + +pub mod local; + +use std::collections::HashMap; +use std::fmt::Debug; +use std::pin::Pin; +use std::sync::{Arc, RwLock}; + +use async_trait::async_trait; +use futures::{AsyncRead, Stream}; + +use local::LocalFileSystem; + +use crate::error::{DataFusionError, Result}; +use crate::logical_plan::Expr; +use chrono::Utc; + +/// Object Reader for one file in a object store +#[async_trait] +pub trait ObjectReader { + /// Get reader for a part [start, start + length] in the file asynchronously + async fn get_reader(&self, start: u64, length: usize) -> Result<Arc<dyn AsyncRead>>; Review comment: Mostly a nitpick, for the naming, it might make the code more readable if we use a name that's different from the `get_reader` method we have in `ObjectStore` here. For example, something along the lines of `get_read`, `get_chunk`, `chunk`: ```rust store.get_reader().get_read().read() ``` -- 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]
