Re: Finding number of rows deleted in a stored procedure - Mailing list pgsql-general

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Ross Bagley wrote:
> Newbie to pl/pgsql here.
>
> I'm trying to create a function that cleans up the foreign keys
> referring to a particular row (if any exist), then removes the row (if
> it exists), and returns the number of rows of br_role that were
> deleted (0 or 1).

Maybe I am missing something, but wouldn't ON DELETE CASCADE do what you
need?

>
> Newbie stored procedure:
>
> CREATE OR REPLACE FUNCTION delete_role(del_role_pk bigint) RETURNS int AS $$
> BEGIN
>     DELETE FROM br_actor_role_mm WHERE role_fk = del_role_pk;
>     DELETE FROM br_role_permission_mm WHERE role_fk = del_role_pk;
>     RETURN DELETE FROM br_role WHERE role_pk = del_role_pk;
> END;
> $$ LANGUAGE plpgsql;
>
> Here's what hapens when I call it in psql using the "SELECT proc(...);" syntax:
>
> bedrock=> select delete_role(1892);
> ERROR:  column "delete" does not exist
> CONTEXT:  SQL statement "SELECT  DELETE FROM br_role WHERE role_pk =  $1 "
> PL/pgSQL function "delete_role" line 4 at return
>
> Hm.  That's not quite right.  It should be returning the result of the
> DELETE query, not the DELETE query itself.

You don't return a query... you return the result of the query.

Take a look at:

http://www.postgresql.org/docs/8.2/static/plpgsql-statements.html#PLPGSQL-STATEMENTS-SQL-NORESULT

Section 37.6.3. Executing a Query with a Single-Row Result

>
> I did come across FOUND, which leads to this:
>
> CREATE OR REPLACE FUNCTION delete_role(del_role_pk bigint) RETURNS int AS $$
> BEGIN
>     DELETE FROM br_actor_role_mm WHERE role_fk = del_role_pk;
>     DELETE FROM br_role_permission_mm WHERE role_fk = del_role_pk;
>     DELETE FROM br_role WHERE role_pk = del_role_pk;
>     IF FOUND THEN
>         RETURN 1;
>     ELSE
>         RETURN 0;
>     END IF;
> END;
> $$ LANGUAGE plpgsql;
>
> But this technique isn't usable in the next use case, where the number
> of deleted rows may be more than one.  Seems nasty to have immediate
> values in the return statements, too.
>
> Seems like there should be some equivalent to FOUND that stores the
> number of updated/deleted rows, but after reading over the docs a
> couple of times, I haven't found it.
>
> So, how do I discover the number of rows deleted by a DELETE query?
>
> Thanks in advance,
> Ross
>


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