Adding callback support.
Hi ppl,
I'm currently building some stored procedures in C that uses some internal
hash tables - It could be really nice to be able to deallocate those
correctly when e.g. a memctx is destroyed. Would it be possible to add this
as a postgresql feature and how should it be done.
I also have some other tasks where I would like to do specific actions when a
transaction completes or aborts. This could be used for maintaining a
pgmemcache correctly and many other cases. Could this be combined with the
above feature so a generic callback framework was added ?
I was thinking something like :
register_callback(my_func, (void*) myprivatedata,
CB_ON_TRNSACT_OK|CB_ON_TRNSACT_ABORT );
Other flags could be on CB_ON_QUERY_DONE/ABORTED, CB_ON_CONNETION_CLOSED
I wouldn't mind trying to do patches if they would be accepted for 8.1 or 8.2
but I would if we could settle for an API before I start coding anything.
---
Nicolai Petri
On Tue, May 10, 2005 at 09:36:59AM +0200, Nicolai Petri wrote:
I'm currently building some stored procedures in C that uses some internal
hash tables - It could be really nice to be able to deallocate those
correctly when e.g. a memctx is destroyed. Would it be possible to add this
as a postgresql feature and how should it be done.
Why don't you just create the hash table inside a context that has the
right longevity? For example, TopTransactionContext. So at transaction
end the hash table is automatically freed.
I also have some other tasks where I would like to do specific actions when a
transaction completes or aborts. This could be used for maintaining a
pgmemcache correctly and many other cases. Could this be combined with the
above feature so a generic callback framework was added ?
Hmm, is there anything the following functions don't do for you:
extern void RegisterXactCallback(XactCallback callback, void *arg);
extern void UnregisterXactCallback(XactCallback callback, void *arg);
extern void RegisterSubXactCallback(SubXactCallback callback, void *arg);
extern void UnregisterSubXactCallback(SubXactCallback callback, void *arg);
See src/backend/access/transam/xact.c
--
Alvaro Herrera (<alvherre[@]dcc.uchile.cl>)
"Ni aun el genio muy grande llegar�a muy lejos
si tuviera que sacarlo todo de su propio interior" (Goethe)