Re: Table locks

> Bruce Momjian <pgman@candle.pha.pa.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.

That was the idea.

> 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.

Good point.  I certainly did not want to muck up the backend with an API
just so I could grab information for a monitoring utility.

>
> 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.

No spinlock.  I was going to just grab a snapshot as it existed.  If it
changes while I am grabbing it, I just try again.

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

Not sure.

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