Re: [HACKERS] proposal: session server side variables

> because MySQL variables are not declared - and allows assign everywhere -

Ok. I do not do MySQL.

> and MSSQL variables are not persistent.

Yep, but they might be?

> In one session you can use lot of roles - some code can be used for
> securing interactive work, some can be for securing some API, sometimes you
> can secure a access to some sources. You can switch lot of roles by using
> security definer functions.

Hmmm. Switching role within a transaction. I never did need that... but 
that is a use case.

>> If you need transactional content - then you should to use tables.
>>
>> Why not.
>>
>> Maybe variables just need be a syntactic convenience around that?
>
> There is pretty similar relation between sequences and tables and variables
> and tables.

Yep. A sequence is a one row table, so a variable may be also a one row 
table as well, but with more flexibility about its type, and some nice 
syntactic sugar (like SERIAL which is syntactic sugar for CREATE SEQUENCE 
...).

> In first iteration the constraint can be implemented with domains - but
> there is not any break to implement constraints directly on variables.

Hmmm. If a variable is implemented as a one row table, then constraints 
are already available there, as well as grant & revoke, they can be any 
type including composite, nearly nothing to implement to get...

A "one row" table would be a CREATE + one INSERT, UPDATE allowed, further 
INSERT and DELETE are disallowed by construction. Then some syntactic 
sugar for variables (session => temporary table, persistent => standard 
table). Note sure about a "transaction variable", though... maybe an 
[unlogged] table automatically dropped on commit?

-- 
Fabien.