CurtHagenlocher commented on issue #811:
URL: https://github.com/apache/arrow-adbc/issues/811#issuecomment-2087736516
I've been starting to play around with this, and the management of the data
structures is a bit annoying. It also isn't very consistent with other parts of
the Arrow C API where the receiver of a call is free to move structures around
in memory as long as it preserves the bits. Here's an alternative whose memory
management is more like the synchronous API:
`struct ArrowAsyncInfo {
void* caller_data;
void* private_data;
void (*release)(struct ArrowAsyncInfo*);
};
AdbcStatusCode AdbcConnectionGetTableSchemaAsync(
struct AdbcConnection* connection,
const char* catalog,
const char* db_schema,
const char* table_name,
struct ArrowAsyncInfo* asyncInfo,
void (*complete)(struct ArrowAsyncInfo*, AdbcStatus, struct AdbcSchema*,
struct AdbcError*);
};`
In this variation, the caller allocates (and is free to move)
`ArrowAsyncInfo` and populates `caller_data`. The receiver fills the
`private_data` and `release` fields and makes a copy for itself. On completion,
the receiver calls the `complete` callback with its copy of `ArrowAsyncInfo`
and its own buffers for the result (which can be `nullptr` on error) and the
result status. It's the original caller's responsibility to clean these up at
an appropriate time by invoking the corresponding `release`. The original
caller then signals that it will no longer call AdbcCancel by calling `release`
on `ArrowAsyncInfo`.
The primary drawback of this variation is that it doesn't cleanly support
synchronous completion of the call. On the other hand, there was nothing in the
initial sketch which would have prevented the completion callback from
happening before the original async call returned, and that fact is a bit more
obvious with this approach.
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