Thread: PQsetNoticeReceiver issues

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I'm writing a onion-skin thick wrapper around the libpq library in Python.
This is my way of getting back into C and also getting a lot more
familiar with PostgreSQL.

I've run into a conundrum with the PQsetNoticeReceiver function call. How
do you set it back to the original default? How do you call the
appropriate PQnoticeProcessor as well?

I expected to find a function in the library like PQdefaultNoticeReceiver,
but either I'm looking at the wrong file or it doesn't exist. I also
expected to see PQdefaultNoticeProcessor, but nothing turned up. While
the documentation contains a neat implementation of a default
PQnoticeProcessor, it doesn't seem to be defined in the library.

Another issue that I am running into is that while the documentation
claims that PQnoticeReceivers may call PQnoticeProcessors, it doesn't
mention how this is to be done. How do I find out which PQnoticeProcessor
is connected to a PGresult?

I though that I could perhaps access it directly by including libpq-int.h,
but that seems to be missing from 7.4 now. (Should the note about not
using libpq-int.h in the documentation be removed now that it isn't there
anymore?)

- --
Jonathan Gardner
jgardner@jonathangardner.net
Live Free, Use Linux!
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Jonathan Gardner wrote:
> I've run into a conundrum with the PQsetNoticeReceiver function call.
> How do you set it back to the original default? How do you call the
> appropriate PQnoticeProcessor as well?

The documentation says:
Each of these functions returns the previous notice receiver or 
processor function pointer, and sets the new value. If you supply a 
null function pointer, no action is taken, but the current pointer is 
returned.

Peter Eisentraut wrote:
> 
> Jonathan Gardner wrote:
> > I've run into a conundrum with the PQsetNoticeReceiver function call.
> > How do you set it back to the original default? How do you call the
> > appropriate PQnoticeProcessor as well?
> 
> The documentation says:
> 
>  Each of these functions returns the previous notice receiver or 
> processor function pointer, and sets the new value. If you supply a 
> null function pointer, no action is taken, but the current pointer is 
> returned.

Saving and restoring the previous noticeProcessor or noticeReceiver handler
function works, unless they actually made use of the "arg" pass-through
argument.  For example, somewhere you have:    PQsetNoticeProcessor(conn, myNoticeProc, &mydata);

And somewhere else you want to temporarily override the noticeProcessor:    prevNoticeProc = PQsetNoticeProcessor(conn,
newNoticeProc,&newdata);    /* ... Do something which makes a notice ... */
 
    /* Restore previous notice processor */    PQsetNoticeProcessor(conn, prevNoticeProc, ????);    /* Oops, lost the
previous"arg". */
 
Not exactly a huge API hole, but nevertheless...