Re: DOMAIN/composite TYPE vs. base TYPE

Hello Tom,

On 28/9/20 17:25, Tom Lane wrote:
> Domain-over-composite might be a slightly simpler answer than your first
> one. It's only available in relatively late-model PG, and I'm not sure
> about its performance relative to your other design, but it is an
> alternative to think about.

"Domain-over-composite" meaning create a TYPE first (DATE, CHAR(1)) and
then a DOMAIN based on that type? (1) How late model are we talking?
The DOMAIN syntax doesn't seem changed from PG 11 to PG 13? (2) Can a
CHECK constraint specify attributes of the composite?

> Note that attaching NOT NULL constraints at the domain level is almost
> never a good idea, because then you find yourself with a semantically
> impossible situation when, say, a column of that type is on the nullable
> side of an outer join. We allow such constraints, but they will be
> nominally violated in cases like that.

NULLs: Tony Hoare's "billion dollars of pain and damage" transported to SQL.

Joe