Re: Support for CALL statement in ecpg

Hi,

Thanks for the review. Please find my comments in-line.

On Fri, Jul 19, 2019 at 8:33 AM Kyotaro Horiguchi
<horikyota(dot)ntt(at)gmail(dot)com> wrote:
>
> Hello.
>
>
> +ECPG: CallStmtCALLfunc_application
>
> Even though it is the default behavior, but as a written rule
> this needs the postfix "block".
>

Done.

> + $$ = cat_str(2,mm_strdup("call"),$2);
>
> Let's have proper spacing.
>
> + * Copy input arguments to the result arguments list so that all the
> + * host variables gets treated as INOUT params.
>

I've removed above comments so this is no more valid.

> This fails for the following usage:
>
> -- define procedure
> create procedure ptest2 (in x int, inout y int) language plpgsql as $$
> begin
> y := y + x;
> end;
> $$;
>
> -- in .pgc
> 14: a = 3;
> 15: r = 5;
> 16: EXEC SQL call ptest2(:a, :r);
> 21: printf("ret = %d, %d\n", a, r);
>
>
> This complains like this:
>
> > SQL error: too many arguments on line 16
> > ret = 8, 5;
>
> The result should be "3, 8". This is because the patch requests
> two return but actually retruned just one.
>
> I'm not sure how to know that previously on ecpg. Might need to
> let users append INTO <vars> clause explicitly.
>

As the ecpg connector is not aware of the param types of the procedure
that it is calling, it becomes the responsibility of end users to
ensure that only those many out variables gets created by ecpg as the
number of fields in the tuple returned by the server and for that, as
you rightly said they must use the INTO clause with CALL statement in
ecpg. Considering this approach, now with the attached v2 patch, the
CALL statement in ecpg application would be like this:

EXEC SQL CALL(:hv1, :hv2) INTO :ret1, ret2;

EXEC SQL CALL(:hv1, :hv2) INTO :ret1 :ind1, :ret2, :ind2;

In case if INTO clause is not used with the CALL statement then the
ecpg compiler would fail with a parse error: "INTO clause is required
with CALL statement"

--
With Regards,
Ashutosh Sharma
EnterpriseDB:http://www.enterprisedb.com