Re: [HACKERS] proposal: schema variables

Hi

2018-05-01 3:56 GMT+02:00 Peter Eisentraut <peter(dot)eisentraut(at)2ndquadrant(dot)com
>:

> 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.
>

Using anonymous composite type variable is just shortcut for situations
when mentioned feature is not a problem. These variables are global, so
there can be only one variable of some specific composite type, and
incompatibility with others is not a issue.

This feature can be interesting for short live temp variables - these
variables can be used for parametrization of anonymous block.

But this feature is not significant, and can be removed from patch.

> 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.
>
>
good idea

Regards

Pavel

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