Re: query output in psql PROMPT

On Fri, Jan 14, 2005 at 12:06:32PM -0500, Tom Lane wrote:
> strk <strk@keybit.net> writes:
> > A simple patch allow query output in psql PROMPT strings:
>
> Why is this a good idea?  Having a query implicitly executed during
> every prompt will have a ton of bad side effects, for instance
> prematurely freezing the query snapshot in SERIALIZABLE transactions.

The only purpose for having made the patch is having current_schema()
printed on the prompt (for the first question).

I know the code is very dirty, is there a chance to current_schema()
as a variable if that won't change transaction status ?

--strk;

>
> The syntax you propose is downright bizarre --- what if I needed a dot
> in the query text?
>
> > +                        cmdend = strcspn(cmd, ".");
> > +                        cmd[cmdend] = '\0';
> > +                        if (cmd)
> > +                        {
> > +                            res = PSQLexec(cmd, false);
> > +                        }
>
> What's the if for?  cmd can't be NULL (you already dumped core if it
> is).
>
> > +                        if (res && PQntuples(res) )
> > +                        {
> > +                            memcpy(buf, PQgetvalue(res, 0, 0), MAX_PROMPT_SIZE-1);
> > +                            PQclear(res);
> > +                        }
>
> Leaks memory on query failure.
>
> > +                        if (strlen(buf) > 0 && buf[strlen(buf) - 1] == '\n')
> > +                            buf[strlen(buf) - 1] = '\0';
>
> Uses undefined contents of buf on query failure.
>
> > +                        p += cmdend + 1;
>
> Falls off the end of the prompt if there was no terminating dot, causing
> subsequent iterations of the loop to continue reading undefined memory.
>
>             regards, tom lane

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