type aliases

You probably should define your domain like this:

CREATE DOMAIN myvarchar varchar(42);

Best regards,
Behrang
http://www.behrang.org

On Sat, Feb 15, 2014 at 6:23 PM, James Harper <james.harper@bendigoit.com.au

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

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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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David Johnston <polobo@yahoo.com> writes:

James Harper wrote

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?

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

Actually the point here is to know the required type modifier of the
*output*. Type input functions do get passed the target typmod, as a
separate argument. See varcharin() for an example.

regards, tom lane

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