Magnus Hagander wrote: > It won't work unless you make it a copy, I think. Because you'd have to > lock the entire structure whenever you called PQexec() (since you don't > know when PQexec does things), and that's just the time when you'd need > to use it from the other thread... > > As for making a copy, yes, that's the other optino I had, but completely > had lost when I wrote that mail. However, it cannot be done in just > pqsl, because psql doesn't see the contents of PGconn. We'd need at > least one new libpq function to create a duplicate PGconn. In order to > be safe, this should probably be a for-cancel-only-copy, so we shouldn't > copy the whole PGconn. But we could copy whatever fields are required to > cancel the query, which in turn would require a new cancelilng function > that accepted this limited structure. > > Probably doable, but it requires API additions, I think.
I thought about this. There are a lot of pointers in PGconn, and most we don't use so I don't like the idea of adding a new API to copy the complex PGconn structure just for Win32 psql cancel. Looking at the PQrequestCancel() code, it only writes to errorMessage and reads from everything else, and I don't see any of those changing (except errorMessage) once the connection is established, so we could do a non-deep copy of the structure and reuse all the existing structure pointers. We would just need to create a new errorMessage structure because PQrequestCancel() wants to write to that. We do need to use locking while we create/destroy this structure. > > I can't think of how to simulate the longjump() currently > > used when cancelConn is NULL though. > > Um. No need for that on win32, I think. When cancelConn is NULL (I am > now assuming we have solved the fact that cancelConn has to be a copy), > we can just do a "return" from the signal handler. The therad will then > happily end, and we're all fine. Or is it supposed to do something other > than just ignoring the cancel request if cancelconn is NULL? Agreed, we can just ignore it. -- Bruce Momjian | http://candle.pha.pa.us [EMAIL PROTECTED] | (610) 359-1001 + If your life is a hard drive, | 13 Roberts Road + Christ can be your backup. | Newtown Square, Pennsylvania 19073 ---------------------------(end of broadcast)--------------------------- TIP 1: subscribe and unsubscribe commands go to [EMAIL PROTECTED]
