abstract data types? - Mailing list pgsql-sql

Hi all,

I'm sure this has become somewhat of a FAQ recently, but I couldn't 
find  any reference to casting composite types in the mailing lists.  
I'm trying  to figure out what support PostgreSQL offers for SQL99 
abstract data types.

PostgreSQL version is cvs from about a week ago.

Given the following relations: 

test=> \d c_adtattr    Table "c_adtattr"
Attribute | Type | Modifier
-----------+------+----------
attr1     | text |
attr2     | text |

test=> \d c_adtparent     Table "c_adtparent"
Attribute |   Type    | Modifier
-----------+-----------+----------
basetype  | text      |
adtattr   | c_adtattr |

OK, now try and insert a tuple into the relation with the composite 
attribute:

test=> INSERT INTO c_adtparent values ('basetype','{"adtr1a1","adtr1a2"}');
ERROR:  Attribute 'adtattr' is of type 'c_adtattr' but expression is of 
type 'unknown'      You will need to rewrite or cast the expression

Is this use of the '{" delimiters correct?  I took it from the array 
docs, which was only reference that I could find to anything like 
inserting values into composite types.

OK, try something stupid (cast as pg_type.typname):

test=> INSERT INTO c_adtparent values ('basetype', CAST 
('{"adtr1a1","adtr1a2"}' AS c_adtattr));
ERROR:  pg_atoi: error in "{"adtr1a1","adtr1a2"}": can't parse 
"{"adtr1a1","adtr1a2"}"

OK, try insert into individual attributes:

test=>  INSERT INTO c_adtparent (basetype, adtattr.attr1, adtattr.attr2) 
VALUES  ('basetype', CAST ('adtr1a1') AS text, CAST ('adtr1a2') AS text);
ERROR:  parser: parse error at or near "."

OK, try double dot syntax from SQL99:

test=>  INSERT INTO c_adtparent (basetype, adtattr..attr1, 
adtattr..attr2) VALUES  ('basetype', CAST ('adtr1a1') AS text, CAST 
('adtr1a2') AS text);
ERROR:  parser: parse error at or near "."

So far, so bad.  Am I doing something really stupid with the syntax, 
should I be using a different approach, or does the support not yet 
exist?  If it's just my stupidity, can someone please give me some 
pointers to exactly where I should RTFM?

OK, so why am I attempting this lunacy?  I am interested in assisting 
with the development of a data store for GIS.  Looks like most of the 
mooted schemas will involve the creation of large numbers of tables of 
identical type.  Each of these in turn contains possibly repeating 
identical conceptual structures.  So to me it made sense, rather than 
producing application specific code to manage these, to see if support 
could be added to the backend DBMS, so that other applications (e.g. 
CAD) could make use of the functionality.

TIA for any assistance.

cheers,
John

-- 
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john reid                                  e-mail john_reid@uow.edu.au       
uproot your questions from their ground and the dangling roots will be
seen.  more questions!                                                      -mentat zensufi

apply standard disclaimers as desired...
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