From: Bob Smith <bsmith@h-e.com>
To: pgsql-sql <pgsql-sql@postgresql.org>
Subject: Problem with deferred referential integrity checks
Date: Mon, 24 Feb 2003 15:38:49 -0800
Message-ID: <1FADF813-4851-11D7-A2BB-0003933DD370@h-e.com> (raw)
I'm running Postgres 7.2.1 on MacOS X Server 10.1.5. Here's the
problem I'm having, by way of a simplified example. First create some
tables and data:
create table table1 (
key int primary key,
data text
);
create table table2 (
table1key int references table1 deferrable initially deferred,
moredata text
);
insert into table1 values (1, 'Item 1');
insert into table1 values (2, 'Item 2');
insert into table2 values (1, 'References Item 1');
insert into table2 values (2, 'References Item 2');
Now try to make a change:
begin work;
delete from table1 where key = 1;
insert into table1 values (1, 'Changed Item 1');
commit;
ERROR: <unnamed> referential integrity violation - key in table1
still
referenced from table2
I don't understand this, it doesn't seem like there should be a
referential violation. At the end of the transaction, there is a row
in table1 which satisfies every reference from table2. On the other
hand, the following does work:
begin work;
delete from table1 where key = 1;
insert into table1 values (3, 'Changed Item 1');
update table2 set table1key = 3 where table1key = 1;
commit;
No error. In this transaction the deferred referential check sees the
inserted row, but in the previous one it does not. Is this intentional
for some reason, a limitation of Postgres, a bug, or am I just not
"getting it"?
Obviously in this example the change could be done as an update,
avoiding the problem entirely. But the real database I'm working with
is much more complicated and an update isn't possible. I can solve the
problem by generating new primary keys for all rows in table1 each time
there is any change, thus making all transactions look like the second
one above, but that causes other problems which I'd like to avoid. Any
other suggestions?
Thanks for any help!
Bob Smith
Hammett & Edison, Inc.
bsmith@h-e.com
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To: pgsql-sql@postgresql.org
Cc: bsmith@h-e.com
Subject: Re: Problem with deferred referential integrity checks
In-Reply-To: <1FADF813-4851-11D7-A2BB-0003933DD370@h-e.com>
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