Re: proposal: schema variables - Mailing list pgsql-hackers

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