but i _really can't_ insert a duplicate key! - Mailing list pgsql-hackers

I have a table:

CREATE TABLE "link_tst" (   "c_id"        int4,   "s_date"      timestamp,   "r_id"        int4,   "r_tally"     int8
);

create unique INDEX "link_tst_idx" on "link_tst" USING btree (r_id, c_id, s_date);

create rule link_tst_rule as on insert to link_tst where exists (   select     c_id   from     link_tst   where
r_id= NEW.r_id     AND c_id = NEW.c_id     AND s_date = NEW.s_date ) do instead   update     link_tst   set     r_hits
=r_hits + NEW.r_hits   where     r_id = NEW.r_id     AND c_id = NEW.c_id     AND s_date = NEW.s_date
 
;       

now when i select from another table with identical fields
but not the UNIQUE qualifier on it's index (there may be duplicates)
I get this:

select now(); insert into link_tst select * from r_link; select now();          now
------------------------2000-05-27 15:08:23-07
(1 row)

ERROR:  Cannot insert a duplicate key into unique index link_tst_idx         now
------------------------2000-05-27 15:10:14-07
(1 row)

How is that possible?  My only guess is that the rule is only being applied
to the table _before_ the query, and if there actually are duplicate rows
to be inserted the rule isn't catching them because the exists clause is
only running on the snapshot of the table before the insert starts.

is there a workaround or is this a possible bug?

--
-Alfred Perlstein - [bright@wintelcom.net|alfred@freebsd.org]
"I have the heart of a child; I keep it in a jar on my desk."