Re: type aliases

James Harper wrote
>>
>> You probably should define your domain like this:
>>
>> CREATE DOMAIN myvarchar varchar(42);
>>
>
> That's what I thought, so it won't do what I want. I need to be able to
> set the length at the time of declaration.
>
> So suppose I wanted to implement myvarchar in C. In my _in function, how
> do I know how big my column declaration is? Eg if someone tries to insert
> 50 characters into my 42 character field, how do I get the declared length
> and then tell postgres that the data to be inserted is too big?
>
> Thanks
>
> James

IMO. You are abusing the type system to implement things that should be
defined using CHECK constraints. If indeed you are working with string I
would avoid length-limited type mods and rely on checks/constraints. There
isn't any viable alternative for numeric scale/precision type modifiers
though :(

There is no current way for a function body to examine the type modifiers of
its input, domain or otherwise.

David J.

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