Re: top-level DML under CTEs

Marko Tiikkaja <marko(dot)tiikkaja(at)cs(dot)helsinki(dot)fi> writes:
> On 2010-09-14 10:51 PM, Tom Lane wrote:
>> My recollection is that whether a CTE is marked RECURSIVE or not affects
>> its scope of visibility, so that confusing the two cases can result in
>> flat-out incorrect parser behavior.

> The worst I can think of is:

> CREATE TABLE foo(a int);

> WITH t AS (SELECT * FROM foo)
> INSERT INTO bar
> WITH RECURSIVE foo (SELECT 1 AS a)
> SELECT * FROM t;

> t will actually be populated with the results of the CTE, not the table foo.

> I don't think this is a huge problem in real life, but if someone thinks
> otherwise, I think we could just error out if the lists have a different
> RECURSIVE definition.

Wrong is wrong. Doesn't matter whether it's "a huge problem in real life".

Why is it so difficult to do this correctly?

regards, tom lane