Re: [HACKERS] Q: RI and isolevels

In Informix:

> Standard (draft) says:
>
> Regardless of the isolation level of the SQL-transaction, phenomena
> P1, P2, and P3 shall not occur during the implied reading of schema
> definitions performed on behalf of executing an SQL-statement, the
>
an alter table, create index or the like (tx must see new schema)

> checking of integrity constraints, and the execution of referen-
> tial actions associated with referential constraints.
>
> I'm not sure what they exactly mean. Could someone run two tests
> for me (in Oracle and Informix/Sybase)?
>
> create table p (k integer primary key);
> create table f (k integer references p(k));
>
> session-1:
begin work;
> set transaction isolation level serializable;
Informix needs: ^^^^^ level not mode
> select * from f; -- just to ensure that xaction began -:)
>
> session-2:
begin work;
> insert into p values (1);
> commit work;
>
> session-1:
> insert into f values (1);
> --
> -- Results? Abort?
> --
>
Goes ok in both isolation levels. Only if session-2 insert is not committed,
the session-1 insert fails with:
691: Missing key in referenced table for referential constraint
(zeu.r155_262).
144: ISAM error: key value locked

> What's the result in the case of read committed isolevel in
> session-1? Is insert succeeded?
>
Yes.

Andreas