Re: plpgsql plan caching allowing invalid data to enter table? - Mailing list pgsql-general

On 07/09/2013 04:05 PM, Joe Van Dyk wrote:

It's looking like I can use a plpgsql function to insert data into a
table that violates a domain constraint. Is this a known problem?

Session 1:

create domain my_domain text check (length(value) > 2);
create table my_table (name my_domain);

create function f(text) returns void as $$
declare my_var my_domain := $1;
begin
    insert into my_table values (my_var);
end $$ language plpgsql;

Session 2:
select f('test');
delete from my_table;
-- Keep session open!

Session 1:
alter domain my_domain drop constraint my_domain_check;
alter domain my_domain add constraint my_domain_check check
(length(value) > 5);

Session 2:
select f('test');
-- This works, but it should fail.
-- I have a constraint of more than 5 characters on the domain.
-- But I can insert a row with 4 characters.

My guess this has more to do with MVCC. Session 1 and 2 are looking at different snapshots of the database and acting accordingly.