CurtHagenlocher commented on code in PR #4917:
URL: https://github.com/apache/arrow-adbc/pull/4917#discussion_r4307630723
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csharp/src/Apache.Arrow.Adbc/C/CAdbcDriverExporter.cs:
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@@ -424,6 +477,7 @@ private unsafe static AdbcStatusCode
ReleaseDriver(CAdbcDriver* nativeDriver, CA
stub.Dispose();
gch.Free();
nativeDriver->private_data = null;
+ s_idleCollector.DriverReleased();
Review Comment:
The premise is right, but this only affects hosts that already do something
unsupported, so I've documented it rather than changed the behavior (55ff58d9a).
- Unloading is opt-in: `canUnload` defaults to `false`. The C/C++ driver
manager never unloads drivers; `ManagedLibrary::Release()` is intentionally
empty (#204), and the Go driver manager shares that code.
- A NativeAOT library can't be safely unloaded regardless; Microsoft's
documentation says unloading isn't supported. Its runtime's finalizer thread
starts with the library and parks inside it, so a host that unloads an AOT
driver is already relying on that thread never waking.
- Cancelling the timer when the driver is released wouldn't make unloading
safe, because the runtime's timer thread can still wake at its previous due
time.
`IdleCollectionDelay`'s remarks now say that a pending collection runs after
release returns, and that a driver which expects to be unloaded should set the
delay to `null`. The importer's `canUnload` parameter now notes that NativeAOT
drivers can't be safely unloaded.
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