Xuanwo commented on code in PR #5208:
URL: https://github.com/apache/opendal/pull/5208#discussion_r1810519200
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core/src/raw/adapters/kv/api.rs:
##########
@@ -25,10 +26,69 @@ use crate::Capability;
use crate::Scheme;
use crate::*;
+/// ScanIter is the async iterator returned by `Adapter::scan`.
+pub trait Scan: Send + Sync + Unpin {
+ /// Fetch the next key in the current key prefix
+ ///
+ /// `None` means no further key will be returned
+ fn next(&mut self) -> impl Future<Output = Option<Result<String>>> +
MaybeSend;
Review Comment:
Let's return `Result<Option<String>>` instead to make it easier to handling
errors.
##########
core/src/raw/adapters/kv/api.rs:
##########
@@ -25,10 +26,69 @@ use crate::Capability;
use crate::Scheme;
use crate::*;
+/// ScanIter is the async iterator returned by `Adapter::scan`.
Review Comment:
Please also update the comment.
##########
core/src/raw/adapters/kv/api.rs:
##########
@@ -25,10 +26,69 @@ use crate::Capability;
use crate::Scheme;
use crate::*;
+/// ScanIter is the async iterator returned by `Adapter::scan`.
+pub trait Scan: Send + Sync + Unpin {
+ /// Fetch the next key in the current key prefix
+ ///
+ /// `None` means no further key will be returned
+ fn next(&mut self) -> impl Future<Output = Option<Result<String>>> +
MaybeSend;
+}
+
+/// A noop implementation of Scan
+impl Scan for () {
+ async fn next(&mut self) -> Option<Result<String>> {
+ None
+ }
+}
+
+/// A ScanIterator implementation for all trivial non-async iterators
Review Comment:
I feel that this is unnecessary. The service should provide their own
scanner when needed. Ideally, service should perform real IO inside scanner
instead of in the `scan` call.
For example, mysql service should build connection / sending query inside
the first `next` call in scanner.
##########
core/src/raw/adapters/kv/mod.rs:
##########
@@ -22,6 +22,9 @@
mod api;
pub use api::Adapter;
pub use api::Metadata;
+pub use api::Scan;
+pub use api::ScanStdIter;
Review Comment:
I wish we won't expose this.
##########
core/src/services/sqlite/backend.rs:
##########
@@ -188,7 +195,35 @@ impl Adapter {
}
}
+#[self_referencing]
+pub struct SqlStream {
Review Comment:
How about following the same name pattern like `SqliteScanner`
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