Thread: libpq PQexecPrepared returns NULL
hello, i've got a very strange problem, PQexecPrepared returns NULL, but if i immadietly rerun the query it will run normally, returning the query result. what can be the problem, and how could I track it down, solve it? any suggestions welcome bye, Gergely Czuczy mailto: phoemix@harmless.hu PGP: http://phoemix.harmless.hu/phoemix.pgp The point is, that geeks are not necessarily the outcasts society often believes they are. The fact is that society isn't cool enough to be included in our activities.
Gergely Czuczy <phoemix@harmless.hu> writes:
> i've got a very strange problem, PQexecPrepared returns NULL, but if i
> immadietly rerun the query it will run normally, returning the query
> result. what can be the problem, and how could I track it down, solve it?
Check PQerrorMessage().
AFAIR the only reasons for a null result (instead of a possibly-error
PGresult) would be out-of-memory or connection failure.
regards, tom lane
hello the strange thing is -- what i've forgot to mention -- is that PQerrorMessage returns an empty string, so from this i don't know the source of the error. how can I check if it is _really_ out of memory? i have 1G RAM in the box, and shm values are set: kernel.shmmax = 536870912 kernel.shmall = 536870912 Bye, Gergely Czuczy mailto: phoemix@harmless.hu PGP: http://phoemix.harmless.hu/phoemix.pgp The point is, that geeks are not necessarily the outcasts society often believes they are. The fact is that society isn't cool enough to be included in our activities. On Thu, 4 Mar 2004, Tom Lane wrote: > Gergely Czuczy <phoemix@harmless.hu> writes: > > i've got a very strange problem, PQexecPrepared returns NULL, but if i > > immadietly rerun the query it will run normally, returning the query > > result. what can be the problem, and how could I track it down, solve it? > > Check PQerrorMessage(). > > AFAIR the only reasons for a null result (instead of a possibly-error > PGresult) would be out-of-memory or connection failure. > > regards, tom lane >
Gergely Czuczy <phoemix@harmless.hu> writes:
> the strange thing is -- what i've forgot to mention -- is that
> PQerrorMessage returns an empty string, so from this i don't know the
> source of the error.
That's messy. I'd recommend getting out a debugger and tracing through
it to see exactly where it's failing. Or put in some printf's. There
aren't that many paths that could return NULL. I guess one of them must
be forgetting to set PQerrorMessage, which seems like a bug to me. Let
us know what you find out.
regards, tom lane