Domain Constraint Violation Error Messages

Hello,

Please consider domains with domain constraints such as the following:

CREATE DOMAIN "t_txt" text NOT NULL
CONSTRAINT "dc_txt" CHECK (VALUE <> '');

CREATE DOMAIN "t_sha1" varchar(40) COLLATE "C" NOT NULL DEFAULT ''
CONSTRAINT "dc_sha1" CHECK (VALUE ~ '^([a-f0-9]{40})?$');

... and some table such as this contrived example:

CREATE TABLE "myusers" (
"name" "t_txt",
"email" "t_txt",
"token" "t_sha1"
);

Now, on inserting or updating the table with invalid data, appropriate domain constraint violations occur. But unfortunatly the associated error messages only reference the domain and not the underlying column, e.g. "ERROR: domain public.t_txt does not allow null values".

That is a huge problem. When domain types are reused in a single table or across multiple tables/schemata it becomes unclear and hard to debug because one doesn't know what specific data item caused the violation as there is no reference to the originating column. In the example above, even a single INSERT INTO "myusers" statement with a constraint violation on the "t_txt" domain wouldn't be clear on whether it originated because of a bad value in "name" or "email". The use of multi-statement queries and writable CTEs make this problem even worse.

On stackoverflow there are some comments suggesting that one should simply stick to single-use domains, but then what's the benefit of using custom domains in the first place? IMHO the biggest value of domain types is the reusability accross the entire database. In our case whe have one base/public schema with a set of domain types and multiple uniform schemata (think multi-tenancy) with thousands of tables that reference those few same domains. This allows us to make universal schema changes easier and more efficient, and it also saves a lot of redundant catalog data, such as repetitive column level constraints and default expressions).

Is there any way you could display the underlying column and schema-qualified table names at least as DETAIL on cosntraint violation?
I'm aware that this is not per se a bug, but without the column info, domains are somewhat useless for all practical purposes. Wouldn't you agree?

Thanks in advance.

Benjamin Coutu

ZeyOS, Inc.

ben(dot)coutu(at)zeyos(dot)com
http://www.zeyos.com