Re: [HACKERS] Tree type, how best to impliment?

Hi again

I got to thinking that doing a tree address like this, the parent address
is all but the last dot-number of the current address, so is redundant,
as it can be derived from the current address.

So, the new idea looks something like this:
CREATE TABLE categories (  category       char(30)    NOT NULL,  cat_id         char(255)   PRIMARY KEY,  nidsufix
int4        DEFAULT 1 NOT NULL,  UNIQUE ( category, substr(cat_id, 1,     lenght(cat_id) - (lenght(cat_id) -
strpos(cat_id,'.')))));
 

Two problems
1.  functions can not be called from inside of the UNIQUE constraint?
2.  strpos() returns the FIRST '.', and I need the LAST '.'.  Is there a
similar function that will return the last position of the substring?

If both of these can not be resolved, then it will be neccesary to use a
parent id field, even though that infomation is contained with in the
cat_id field.

Thanks
Terry Mackintosh <terry@terrym.com>          http://www.terrym.com
sysadmin/owner  Please! No MIME encoded or HTML mail, unless needed.

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