[PR] feat(rust): Let immutable drivers create connections [arrow-adbc]

["felipecrv (via GitHub)" <gi...@apache.org>]

felipecrv opened a new pull request, #2788:
URL: https://github.com/apache/arrow-adbc/pull/2788

   Since the removal of the global driver lock, there is no risk of deadlocks between the locks on the driver and on the database objects.
   
   IIUC, this was why member functions on the database struct took a mutable `self` parameter:
   
   ```rust
       /// Initialize the given database using the loaded driver.
       ///
       /// This uses `&mut self` to prevent a deadlock.
       fn database_init(
           &mut self,
           mut database: ffi::FFI_AdbcDatabase,
       ) -> Result<ffi::FFI_AdbcDatabase> {
   ```
   
   Requiring `&mut self` is overkill and requires another layer of locking at the application side if multiple threads share a database instance (as they should for connection pooling).
   
   This doesn't mean we are passing a forged mutable pointer to the driver via the FFI, the locking on the inner database ensures exclusive access to the `FFI_AdbcDatabase`.
   
   ```rust
       /// Initialize the given connection using the loaded driver.
       fn connection_init(
           &self,
           mut connection: ffi::FFI_AdbcConnection,
       ) -> Result<ffi::FFI_AdbcConnection> {
           let driver = self.ffi_driver();
           let mut database = self.inner.database.lock().unwrap();
   
           // ConnectionInit
           let mut error = ffi::FFI_AdbcError::with_driver(driver);
           let method = driver_method!(driver, ConnectionInit);
           let status = unsafe { method(&mut connection, &mut *database, &mut error) };
           check_status(status, error)?;
   
           Ok(connection)
       }
   ```


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Re: [PR] fix(rust)!: Let immutable drivers create connections [arrow-adbc]

["felipecrv (via GitHub)" <gi...@apache.org>]

felipecrv merged PR #2788:
URL: https://github.com/apache/arrow-adbc/pull/2788


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