Weird constraint output

[Please hold me on the to:/cc: list since I am not subscribed]

After talking this over with some of the great guys on IRC it was
suggested I ask here.

I am currently working on a document about how to convert from MySQL to
PostgreSQL (Sybase, Oracle, DB2, MS SQL Server are also going to be
done). I am now messing with CONSTRAINT CHECK and am encountering
something I don't see the logic of.

I decided to make sure Bugzilla works on pgsql 7.3.x and started to
convert the MySQL database schema to a pgsql one. One of the parts has
a layout like:

CREATE TABLE bugs (
-- ...skipping to relevant point
bug_severity character varying(50) -- in MySQL this is enum()
);

Next I did an:

ALTER TABLE ONLY bugs ADD CONSTRAINT bugs_severity_cstr CHECK
(bug_severity IN ('blocker', 'critical', 'major'));

Now, when I do a \d bugs I get:

Check constraints: "bugs_severity_cstr" (((bug_severity =
'blocker'::character varying) OR (bug_severity = 'critical'::character
varying)) OR (bug_severity = 'major'::character varying))

I would've expected:

Check constraints: "bugs_severity_cstr" ((bug_severity =
'blocker'::character varying) OR (bug_severity = 'critical'::character
varying) OR (bug_severity = 'major'::character varying))

If you have even more choices there (as Bugzilla does) you even get:

CONSTRAINT bugs_severity_cstr CHECK ((((((((bug_severity =
'blocker'::character varying) OR (bug_severity = 'critical'::character
varying)) OR (bug_severity = 'major'::character varying)) OR
(bug_severity = 'normal'::character varying)) OR (bug_severity =
'minor'::character varying)) OR (bug_severity = 'trivial'::character
varying)) OR (bug_severity = 'enhancement'::character varying)))
);

But there is no logic to have all those parens plus it makes pg_dump -s
and \d tablename a whole lot messier to read.

Can anyone clarify why we have it like this? Or whether or not it is a
bug perhaps? I could understand micro optimizations, but in this case?

Thanks,

--
Jeroen Ruigrok van der Werven <asmodai(at)wxs.nl> / asmodai
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