Re: [HACKERS] proposal: schema variables

On 4/20/18 13:45, Pavel Stehule wrote:
> I dunno, it seems awfully different to me.  There's only one "column",
> right?  What code is really shared here?  Are constraints and triggers
> even desirable feature for variables?  What would be the use case?
>
>
> The schema variable can hold composite value. The patch allows to use
> any composite type or adhoc composite values
>
> DECLARE x AS compositetype;
> DECLARE x AS (a int, b int, c int);

I'm not sure that this anonymous composite type thing is such a good
idea. Such a variable will then be incompatible with anything else,
because it's of a different type.

In any case, I find that a weak argument for storing this in pg_class.
You could just as well create these pg_class entries implicitly and link
them from "pg_variable", same as composite types have a main entry in
pg_type and additional stuff in pg_class.

> I think stuffing this into pg_class is pretty strange.
>
> It will be if variable is just scalar value without any possibilities.
> But then there is only low benefit
>
> The access rights implementation is shared with other from pg_class too.

In DB2, the privileges for variables are named READ and WRITE. That
would make more sense to me than reusing the privilege names for tables.

--
Peter Eisentraut http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services