houqp commented on a change in pull request #1556:
URL: https://github.com/apache/arrow-datafusion/pull/1556#discussion_r785403949
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File path: datafusion/src/datasource/object_store/mod.rs
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@@ -33,6 +33,12 @@ use local::LocalFileSystem;
use crate::error::{DataFusionError, Result};
+/// Both Read and Seek
+pub trait ReadSeek: Read + Seek {}
+
+impl<R: Read + Seek> ReadSeek for std::io::BufReader<R> {}
+impl<R: AsRef<[u8]>> ReadSeek for std::io::Cursor<R> {}
Review comment:
Nice tip on the generic approach. @Igosuki is right that this is not
needed for BufRead and Cursor, It's only needed for `std::fs::File`, so I will
keep the generic form. Here is the build error I got without it:
```
error[E0277]: the trait bound `std::fs::File:
datasource::object_store::ReadSeek` is not satisfied
--> datafusion/src/datasource/object_store/local.rs:82:12
|
82 | Ok(Box::new(File::open(&self.file.path)?))
| -- ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait
`datasource::object_store::ReadSeek` is not implemented for `std::fs::File`
| |
| required by a bound introduced by this call
|
= note: required for the cast to the object type `dyn
datasource::object_store::ReadSeek + std::marker::Send + std::marker::Sync`
```
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