Thread: Referential integrity Freeze

    Hello,

I have two 4 table with referential constraint's that are hanging when I 
try to delete from them.

I have a,
users table, ( 30000 rows )
suburbs table ( 16000 rows ),
regions table ( 54 rows )and
a bus_pc_idc table ( business type ) ( 30000 rows )

Here is my integrity rules:

create table bus_pc_idc (
id serial,
user_id        int4 REFERENCES users(user_id) ON DELETE CASCADE ON 
UPDATE CASCADE NOT NULL,
sub_id         int4 REFERENCES suburbs(sub_id) ON DELETE CASCADE ON 
UPDATE CASCADE NOT NULL,
idc_id         int4 REFERENCES idc(id) ON DELETE CASCADE ON UPDATE 
CASCADE NOT NULL,
active         bool NOT NULL DEFAULT 'f'::bool
);

As the system is still being developed I want to 'empty' out the 
database from titme to time and rebuild it.
I think that when I delete from the users table the delete should 
cascade through the bus_pc_idc table.
However it's justing hanging when I delete all from the users table. 
When the database is hanging the CPU is 99% for the Postgres process.

I can't see what's wrong. Perhaps I'm missing something in the 
referential integrity.
Thanks in advance
Cheers
Rudi.

>     Hello,
>
> I have two 4 table with referential constraint's that are hanging when I
> try to delete from them.
>
> I have a,
> users table, ( 30000 rows )
> suburbs table ( 16000 rows ),
> regions table ( 54 rows )and
> a bus_pc_idc table ( business type ) ( 30000 rows )
>
> Here is my integrity rules:
>
> create table bus_pc_idc (
> id serial,
> user_id        int4 REFERENCES users(user_id) ON DELETE CASCADE ON
> UPDATE CASCADE NOT NULL,
> sub_id         int4 REFERENCES suburbs(sub_id) ON DELETE CASCADE ON
> UPDATE CASCADE NOT NULL,
> idc_id         int4 REFERENCES idc(id) ON DELETE CASCADE ON UPDATE
> CASCADE NOT NULL,
> active         bool NOT NULL DEFAULT 'f'::bool
> );
>
> As the system is still being developed I want to 'empty' out the
> database from titme to time and rebuild it.
> I think that when I delete from the users table the delete should
> cascade through the bus_pc_idc table.
> However it's justing hanging when I delete all from the users table.
> When the database is hanging the CPU is 99% for the Postgres process.
>
> I can't see what's wrong. Perhaps I'm missing something in the
> referential integrity.

It shouldn't be hanging, however, do you have indexes on the *_id fields
in bus_pc_idc?  Otherwise it's going to be doing 1 sequence scan over
bus_pc_idc for each row in users.

Stephan,

Thanks for your reply.
No I don't have indexes on the *_id fields in bus_pc_idc. Now that you 
point it out it make perfect sense why this query would
take a while and give the impression it's hanging - it's all those seq 
scans.

Thank you kindly, I really appreicate it.
Regards
Rudi.