Re: [HACKERS] proposal: session server side variables

> There is a singleton table :)
>
> create table foo(x integer unique not null default 1 check(x = 1), y integer);
> insert into foo(y) values(100);
> analyze foo;

I know this one. It can be empty, which a singleton cannot be. For a 
singleton table, you should have one and only one row, you cannot insert 
or delete, so this is only part of the real thing.

> For example - MySQL @var is volatile - can be changed in query - that's
> mean, you cannot use it as const for planner :(

Indeed, because of the ":=" within in a SELECT query, the variable is 
updated at each round. Yuk.

-- 
Fabien.