Re: Table locks

Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us> writes:
> I am thinking of a tcl/tk app that can go in and grab information from
> backends by querying the actual structure values. Does gdb
> automatically halt the running app?

Yes. I suppose this is no big problem if you start a backend to be
used only as the gdb target, but you'd not want to take over a live
client's backend for the purpose.

A bigger problem is that it's not a portable approach, since gdb may not
be available/installed on a given platform. Furthermore, you won't get
far unless the installed executable was compiled with debug symbols,
which isn't (and IMHO shouldn't be) the default configuration.

Finally (and probably the key point): what are you going to do about
locking? You aren't going to be able to grab a spinlock via gdb, nor
would it be a good idea if you could --- holding down a critical
spinlock while a tcl-to-gdb-to-backend conversation goes on would be a
killer for performance.

I think the information-grabbing routines need to be C code in the
backend.

regards, tom lane