Scott Bailey wrote:
Grzegorz Jaśkiewicz wrote:
Why is it not possible to create domain on composite type ?
Consider the example, I got (a bytea, b timestamp, c timestamp). Where
b < c always, and both b and c have some default value, a can stay
null.
Now, I don't want to go berserk, and create aditional table for that,
because type is shared between two tables. But it would be nice, to be
able to create domain based on that type.
Any reasons I can't , or is it just something I do wrong?
That's on 8.3/8.4
I think Postgres' type system is as good any and better than most...
even if it doesn't do what you are asking. They ALL have their problems.
What I do is handle it in the constructors. So if someone passes b > c
it swaps them. It doesn't help for casts, so I'm careful to always use
the constructors.
I wrote a couple articles about doing this in Postgres and Oracle on my
blog.
http://scottrbailey.wordpress.com/2009/05/19/timespan-postgresql/
Scott
I was also thinking that if you wanted more of the domain behavior; your
constructors could throw an exception rather than silently swapping b
and c, as I chose to do.
Scott
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