Re: [HACKERS] merging some features from plpgsql2 project

On Tue, Jan 3, 2017 at 9:58 AM, Pavel Stehule <pavel.stehule@gmail.com> wrote:
> 2017-01-03 16:23 GMT+01:00 Merlin Moncure <mmoncure@gmail.com>:
>> So -1 to strict mode, unless we can make a case why this can't be done
>> as part of checking/validation.
>
> Can be plpgsq.extra_errors and plpgsql.extra_warnings solution?
>
> I am thinking so there is a space for improvement (in extra_* usage)

extra_warnings seems ok at the GUC level.  However it's bad to have a
body of code fail to compile based on GUC.  check_function_bodies for
example is a complete hack and should be avoided if at all possible
IMO.  There is very good informal rule that GUC should not impact
behavior (minus some special cases like timeouts).   Good examples of
failure to follow this rule are mysql and php.

Maybe settings at level of extension could be ok, but I'm skeptical.
Good languages are clear without needing extra context.

> Do you know plpgsql_check https://github.com/okbob/plpgsql_check ?

Yes.  This is good design and should be model for core-work (if any).
 In my ideal world, this could would be part of pgxn and to have pgxn
client be installed in core.   For plpgsql to enter modern era we need
standardized packaging and deployment like cran, npm, etc.

>> Other random points:
>> *) Another major pain point is swapping in the input variables for
>> debugging purposes.  Something that emits a script based on a set of
>> arguments would be wonderful.
>
> ???

Often for debugging of complicated cases I'm starting from errors in
database log with function name and argument values.  Sometimes I find
myself pasting pl/pgsql function into text editor and replacing input
variables with known values.

>>
>> *) Would also like to have a FINALLY block
>
> What you can do there?

This is syntax sugar so you don't need second begin/end/exception
block or duplicated code.  It separates error handling from cleanup.

BEGIN
  PERFORM dblink_connect(...
  <risky_stuff>
EXCEPTION WHEN OTHERS THEN
  <log/handle error>
FINALLY
  PERFORM dblink_disconnect(...
END;

>> *) Some user visible mechanic other than forcing SQL through EXECUTE
>> to be able to control plan caching would be useful.
>
> fully agree.
>
> Have you some ideas?
>
> What about plpgsql option (function scope) -- WITHOUT-PLAN-CACHE - any non
> trivial plans will not be cached - and evaluated as parametrized query only.

I have slight preference for syntax marker for each query, similar to
INTO.  Maybe 'UNCACHED'?

On Tue, Jan 3, 2017 at 10:57 AM, Jim Nasby <Jim.Nasby@bluetreble.com> wrote:
> Or just fix the issue, provide the backwards compatability GUCs and move on.

I really don't think this will fly.  I'm not buying your argument (at
all) that compatibility breaks have have been cleanly done in the
past, at least not in the modern era.  In any event, marginal language
improvements are not a good justification to do it.   And yes, the
continual monkey around with column names in pg_stat_activity are a
major hassle.  For heaven's sake, can we just add new columns and/or
create a new view?

merlin