Re: proposal: schema variables

ne 10. 11. 2024 v 17:19 odesílatel Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com>
napsal:

>
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> ne 10. 11. 2024 v 16:24 odesílatel Dmitry Dolgov <9erthalion6(at)gmail(dot)com>
> napsal:
>
>> Hi folks,
>>
>> Thanks for continuing this work. As a side note, I would like to mention
>> how strange the situation in this CF item is. If I understand correctly,
>> there are two hackers threads discussing the same patch, with recent
>> patches posted in both of them. This is obviously confusing, e.g. the
>> main concern from another thread, about names clashing, wasn't even
>> mentioned in this one. Is it possible to reconcile development in one
>> thread?
>>
>
> This is probably my error. I don't try to organize threads, just I'll try
> to reply in the thread where I got a question.
>

I thought a lot of time about better solutions for identifier collisions
and I really don't think so there is some consistent user friendly syntax.
Personally I think there is an easy already implemented solution -
convention - just use a dedicated schema for variables and this schema
should not be in the search path. Or use secondary convention - like using
prefix "__" for session variables. Common convention is using "_" for
PLpgSQL variables. I searched how this issue is solved in other databases,
or in standard, and I found nothing special. The Oracle and SQL/PSM has a
concept of visibility - the variables are not visible outside packages or
modules, but Postgres has nothing similar. It can be emulated by a
dedicated schema without inserting a search path, but it is less strong.

I think we can introduce an alternative syntax, that will not be user
friendly or readable friendly, but it can be without collisions - or can
decrease possible risks.

It is nothing new - SQL does it with old, "new" syntax of inner joins, or
in Postgres we can

where salary < 40000

or

where pg_catalog.int4lt(salary, 40000);

or some like we use for operators OPERATOR(*schema*.*operatorname*)

So introducing VARIABLE(schema.variablename) syntax as an alternative
syntax for accessing variables I really like. I strongly prefer to use this
as only alternative (secondary) syntax, because I don't think it is
friendly syntax or writing friendly, but it is safe, and I can imagine
tools that can replace generic syntax to this special, or that detects
generic syntax and shows some warning. Then users can choose what they
prefer. Two syntaxes - generic and special can be good enough for all - and
this can be perfectly consistent with current Postgres.

Regards

Pavel

> Regards
>
> Pavel
>
>