Re: enhance SPI to support EXECUTE commands

On 2019/9/5 16:31, Pavel Stehule wrote:
>
>
> čt 5. 9. 2019 v 10:25 odesílatel Quan Zongliang
> <zongliang(dot)quan(at)postgresdata(dot)com
> <mailto:zongliang(dot)quan(at)postgresdata(dot)com>> napsal:
>
> On 2019/9/5 15:09, Pavel Stehule wrote:
> >
> >
> > čt 5. 9. 2019 v 8:39 odesílatel Quan Zongliang
> > <zongliang(dot)quan(at)postgresdata(dot)com
> <mailto:zongliang(dot)quan(at)postgresdata(dot)com>
> > <mailto:zongliang(dot)quan(at)postgresdata(dot)com
> <mailto:zongliang(dot)quan(at)postgresdata(dot)com>>> napsal:
> >
> >     Dear hackers,
> >
> >     I found that such a statement would get 0 in PL/pgSQL.
> >
> >     PREPARE smt_del(int) AS DELETE FROM t1;
> >     EXECUTE 'EXECUTE smt_del(100)';
> >     GET DIAGNOSTICS j = ROW_COUNT;
> >
> >     In fact, this is a problem with SPI, it does not support
> getting result
> >     of the EXECUTE command. I made a little enhancement. Support
> for the
> >     number of rows processed when executing INSERT/UPDATE/DELETE
> statements
> >     dynamically.
> >
> >
> > Is there some use case for support this feature?
> >
> A user deletes the data in PL/pgSQL using the above method, hoping
> to do
> more processing according to the number of rows affected, and found
> that
> each time will get 0.
>
> Sample code:
> PREPARE smt_del(int) AS DELETE FROM t1 WHERE c=$1;
> EXECUTE 'EXECUTE smt_del(100)';
> GET DIAGNOSTICS j = ROW_COUNT;
>
>
> This has not sense in plpgsql. Why you use PREPARE statement explicitly?
>
Yes, I told him to do it in other ways, and the problem has been solved.

Under psql, we can get this result

flying=# EXECUTE smt_del(100);
DELETE 1

So I think this may be the negligence of SPI, it should be better to
deal with it.

>
> IF j=1 THEN
>    do something
> ELSIF j=0 THEN
>    do something
>
> Here j is always equal to 0.
>
>
>
> Regards
>
> > Regards
> >
> > Pavel
> >
> >
> >     Regards,
> >     Quan Zongliang
> >
>