Problems with RULE - Mailing list pgsql-sql

Hello all,

I tried to implement the following rule: if someone wants to delete a record
from a table t_xyz (id integer, deleted boolean) the record should get a
delete-flag (deleted = true). When this "pre-deleted" record is deleted for
the next time it should be physically deleted from the database.

I implemented the following rule:
 CREATE RULE r_del_xyz AS ON DELETE TO t_xyz WHERE (old.deleted = false) DO INSTEAD   UPDATE t_xyz   SET deleted = true
 WHERE id = old.id;
 

Now I tested the new rule:
 INSERT INTO t_xyz VALUES (1, false); INSERT INTO t_xyz VALUES (2, false); DELETE FROM t_xyz WHERE id = 1; SELECT *
FROMt_xyz ;
 
  id | deleted ----+---------   2 | f

What has happened? The rule seems to be ignored and the record was deleted!

I dropped the rule, deleted all records and recreated the rule without the
additional WHERE-Clause in the UPDATE-Statement:
 DROP RULE r_del_xyz;
 DELETE FROM t_xyz;
 CREATE RULE r_del_xyz AS ON DELETE TO t_xyz WHERE (old.deleted = false) DO INSTEAD   UPDATE t_xyz   SET deleted =
true;
 INSERT INTO t_xyz VALUES (1, false); INSERT INTO t_xyz VALUES (2, false);

The same test again:
 DELETE FROM t_xyz WHERE id = 1; SELECT * FROM t_xyz ;
  id | deleted ----+---------   2 | t

It seems to me that PostgreSQL executed the rule, but ignored the keyword
INSTEAD and deleted the record after having updated it?!

One last test with a slightly different rule (look at the WHERE-clause in
the "AS-ON"-clause):
 DROP RULE r_del_xyz;
 DELETE FROM t_xyz;
 CREATE RULE r_del_xyz AS ON DELETE TO t_xyz WHERE (1 = 1) DO INSTEAD   UPDATE t_xyz   SET deleted = true   WHERE id =
old.id;
 INSERT INTO t_xyz VALUES (1, false); INSERT INTO t_xyz VALUES (2, false);
 DELETE FROM t_xyz WHERE id = 1; SELECT * FROM t_xyz ;
  id | deleted ----+---------   2 | f   1 | t
 DELETE FROM t_xyz WHERE id = 1; SELECT * FROM t_xyz ;

Everything is alright now! Am I wrong? Is the WHERE-clause "WHERE
(old.deleted = false)" not correct? Any hints? Or it is really a bug?

Best regards, Jens Hartwig

PS: You will find the scripts in the attachment.

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T-Systems
Projektleiter
debis Systemhaus GEI GmbH
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