Re: constraint with reference to the same table

Hi,

Can I confirm what this means then ..

For large table's each column with ref. inegritry I should create an
index on those columns ?

So if I create a table like this :
CREATE TABLE business_businesstype
(
b_bt_id serial PRIMARY KEY,
b_id integer REFERENCES business ON UPDATE CASCADE ON DELETE CASCADE NOT
NULL,
bt_id integer REFERENCES businesstype ON UPDATE CASCADE ON DELETE
CASCADE NOT NULL
);

I should then create 2 index's

CREATE INDEX business_idx ON business_businesstype (business);
CREATE INDEX businesstype_idx ON business_businesstype (businesstype);

Thanks
Regards
Rudi.

Stephan Szabo wrote:

>On Thu, 15 May 2003, Victor Yegorov wrote:
>
>
>
>>I'm using PostgreSQL 7.3.1 on i686-pc-linux-gnu, compiled by GCC egcs-2.91.66.
>>
>>Here is topic. Table transactions:
>>
>>=> \d transactions
>> Table "public.transactions"
>> Column | Type | Modifiers
>>-------------+--------------+-----------
>> trxn_id | integer | not null
>> trxn_ret | integer |
>> trxn_for | integer |
>> status | numeric(2,0) | not null
>> auth_status | numeric(2,0) | not null
>>Indexes: transactions_pkey primary key btree (trxn_id)
>>Foreign Key constraints: trxns_id FOREIGN KEY (trxn_id) REFERENCES connections(conn_id) ON UPDATE NO ACTION ON DELETE NO ACTION,
>> trxns_ret FOREIGN KEY (trxn_ret) REFERENCES transactions(trxn_id) ON UPDATE NO ACTION ON DELETE NO ACTION,
>> trxns_for FOREIGN KEY (trxn_for) REFERENCES transactions(trxn_id) ON UPDATE NO ACTION ON DELETE NO ACTION
>>
>>As you can see, trxns_ret and trxns_for constraints references to the same table they come from.
>>
>>Maintenance of system includes the following step:
>>delete from transactions where transactions.trxn_id = uneeded_trxns.trxn_id;
>>transactions volume is about 10K-20K rows.
>>uneeded_trxns volume is about 3K-5K rows.
>>
>>
>>Problem: It takes to MUCH time. EXPLAIN says:
>>
>>I was waiting for about 30 minutes and then hit ^C.
>>
>>After some time spent dropping indexes and constraints, I've found out, that problem was in
>>those 2 "cyclic" constraints. After drop, query passed in some seconds (that is suitable).
>>
>>Question: why so?
>>
>>
>
>For each row dropped it's making sure that no row has either a trxn_ret or
>trxn_for that pointed to that row. If those columns aren't indexed it's
>going to be amazingly slow (if they are indexed it'll probably only be
>normally slow ;) ).
>
>
>
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