Re: [HACKERS] PoC plpgsql - possibility to force custom or generic plan
| От | Pavel Stehule |
|---|---|
| Тема | Re: [HACKERS] PoC plpgsql - possibility to force custom or generic plan |
| Дата | |
| Msg-id | CAFj8pRAFjMFu4XQbpruWze_c+oMyVoh0=0ays2Yx=dd4Y0RY9w@mail.gmail.com обсуждение исходный текст |
| Ответ на | Re: [HACKERS] PoC plpgsql - possibility to force custom or generic plan (Tom Lane <tgl@sss.pgh.pa.us>) |
| Список | pgsql-hackers |
2017-09-05 19:38 GMT+02:00 Tom Lane <tgl@sss.pgh.pa.us>:
Pavel Stehule <pavel.stehule@gmail.com> writes:
> 2. what syntax we should to use (if we accept this feature)? There was not
> another proposal if I remember well - The PRAGMA syntax is strong because
> we can very well specify to range where the plans caching will be
> explicitly controlled. It is well readable and static.
The complaint I have about PRAGMA is that it's yet another syntax for
accomplishing pretty much the same thing. If you don't like the GUC
solution, we've already got the "comp_option" syntax for static options
in plpgsql. Sure, that's not too pretty, but that's not a good reason
to invent yet another way to do it.
comp_option has only function scope, what is too limited for this purpose.
I don't prefer GUC for this purpose because you need to do SET/RESET on two places. With GUC the code can looks like:
PERFORM set_config('cachexx', 'off')
FOR r IN SELECT ...
LOOP
PERFORM set_config(' cachexx', 'on')
....
PERFORM set_config('cachexx', 'off')
END LOOP;
PERFORM set_config('cachexx', 'on');
The another reason for inventing PRAGMA syntax to PLpgSQL was support for autonomous transaction and I am thinking so is good idea using same syntax like PL/SQL does.
regards, tom lane
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