pgplsql SELECT INTO ... FOR UPDATE (transaction/locking question)

I've got a few plpgsql stored functions (in 7.4.x) that use the

select x into y from table where condition for update

syntax without any problem.

Maybe there's something else going on?

John Sidney-Woollett

Eric Brown wrote:

On Wed, 2004-12-15 at 01:38 -0800, Eric Brown wrote:

______________________________________________________________________

I'm trying to write a stored procedure in plpgsql that selects a row
and possibly increments one of its fields. I thought I would do SELECT
INTO my_record * FROM my_table FOR UPDATE WHERE ..., but apparently
plpgsql doesn't like the FOR UPDATE in a stored procedure.

the docs seem to imply that the FOR UPDATE clause should follow the
WHERE clause.
and indeed, it would seem that your should follow the '*'
try
SELECT * INTO my_record WHERE ... FOR UPDATE

gnari

I'm trying to write a stored procedure in plpgsql that selects a row
and possibly increments one of its fields. I thought I would do SELECT
INTO my_record * FROM my_table FOR UPDATE WHERE ..., but apparently
plpgsql doesn't like the FOR UPDATE in a stored procedure. Does plpgsql
automatically lock any rows I read until the stored procedure exits?
I'm just not sure how to get the functionality I'm looking for and not
have to concern myself with concurrency.

Example:
create table t_test (x int, y int);
create or replace function f_test(int) returns void as '
declare r record;
begin
select into r *, oid from t_test -- FOR UPDATE
where x = $1;
if found then
update t_test set y=y+1 where oid = r.oid;
end if;
return;
end' language plpgsql;
insert into t_test values (1,1);
select f_test(1);

Would it be better to just write

update t_test set y=y+1 where x = $1;