Re: plpgsql.consistent_into - Mailing list pgsql-hackers
| From | Pavel Stehule |
|---|---|
| Subject | Re: plpgsql.consistent_into |
| Date | |
| Msg-id | CAFj8pRAmhU-3Ffh4qS0Xou59V4a5xsojNejt+baASHS7eF3+Pg@mail.gmail.com Whole thread Raw |
| In response to | Re: plpgsql.consistent_into (Florian Pflug <fgp@phlo.org>) |
| Responses |
Re: plpgsql.consistent_into
|
| List | pgsql-hackers |
2014/1/12 Florian Pflug <fgp@phlo.org>
On Jan12, 2014, at 22:37 , Pavel Stehule <pavel.stehule@gmail.com> wrote:I must say I hate behaviour-changing GUCs with quite some passion. IMHO
> There is GUC for variable_conflict already too. In this case I would to
> enable this functionality everywhere (it is tool how to simply eliminate
> some kind of strange bugs) so it needs a GUC.
>
> We have GUC for plpgsql.variable_conflict three years and I don't know
> about any problem.
they tend to cause bugs, not avoid them, in the long run. The pattern
usually is
1) Code gets written, depends on some particular set of settings
to work correctly
2) Code gets reused, with little further testing since it's supposed
to be battle-proven anyway. Settings get dropped.
3) Code blows up for those corner-cases where the setting actually
matter. Debugging is hell, because you effectively have to go
over the code line-by-line and check if it might be affected by
some GUC or another.
Only a few days ago I spent more than an hour tracking down a bug
which, as it turned out, was caused by a regex which subtly changed its
meaning depending on whether standard_conforming_strings is on or off.
Some GUCs are unavoidable - standard_conforming_strings, for example
probably still was a good idea, since the alternative would have been
to stick with the historical, non-standard behaviour forever.
But in this case, my feeling is that the trouble such a GUC may cause
out-weights the potential benefits. I'm all for having a directive like
#consistent_into (though I feel that the name could convey the
meaning better). If we *really* think that this ought to be the default
from 9.4 onward, then we should
*) Change it to always complain, except if the function explictly
specifies "#consistent_into on" or whatever.
*) Have pg_dump add that to all plpgsql functions if the server
version is < 9.4 or whatever major release this ends up in
That's all just my opinion of course.
I am thinking so GUC and plpgsql option can live together. If you like to accent a some behave, then you can use a plpgsql option. On second hand, I would to use a some functionality, that is safe, but I don't would to dirty source code by using repeated options. But I have to check (and calculate with risk) a GUC settings.
One idea: required GUC? Can be nice a possibility to ensure some GUC setting, and restore ensure these values or raises warning.
Back to main topic. Required and described feature doesn't change a behave of INTO clause. I can enable or disable this functionality and well written code should to work without change (and problems). When check is disabled, then execution is just less safe. So in this case, a impact of GUC is significantly less than by you described issues. Does know anybody a use case where this check should be disabled?
Probably we have a different experience about GUC. I had a problem with standard_conforming_strings and bytea format some years ago. Now I prepare document about required setting. But I can see (from my experience from Czech area) more often problems related to effective_cache_size or from_collapse_limit and similar GUC. These parameters are behind knowledge (and visibility) typical user.
Best regards
Pavel
best regards,
Florian Pflug
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