Re: Weird effects using BLOBs from libpq

Joerg Hessdoerfer <Joerg(dot)Hessdoerfer(at)sea-gmbh(dot)com> writes:
> I'm experiencing somewhat confusing results using lo_creat(), lo_open(),
> lo_write()...

> First effect I have noticed is that when I write more than a certain
> amount of data at once using lo_write(), my application hangs
> indefinitely (10K work perfect, 100K not). Is there a well-known
> limit? On what does it depend? Or is it an unexpected feature ;-)

> Next off, now that everything runs fine, it does so only when using a
> local database - when connecting over the network to our test server,
> i need to put in usleeps of minimum 30ms in between consecutive writes
> to the same BLOB - else writing fails and i have to close the DB
> connection to do anything useful with the DB again!

Ugh. FWIW, no one else has reported anything like that, as far as I
can remember.

> I'm afraid i can't give you source code right now, 'cause i'm using LabVIEW
> (a graphical programming language).

> Oh, yes, the local DB is postgreSQL 7.0.2 on cygwin 1.1.4, cygipc 1.0.7.

Maybe it's just my natural dislike for anything Microsoft, but I'm
suspicious that you are looking at bugs in the Windows TCP/IP stack.
Or possibly a cygipc bug. The timing dependency would more or less
have to be a TCP-level bug, seems like (unless you are trying to use
the "non blocking output" feature of libpq? That's known not to be
too reliable, and I don't recommend using it...)

regards, tom lane