Re: BUG #18536: Using WITH inside WITH RECURSIVE triggers a "shouldn't happen" error

PG Bug reporting form <noreply(at)postgresql(dot)org> writes:
> The following query:
> WITH RECURSIVE t(n) AS (
> WITH t1 AS (SELECT 1 FROM t) SELECT 1
> UNION
> SELECT 1 FROM t1)
> SELECT * FROM t;

That should throw an error, certainly: it's not a valid recursive
structure. (Since the inner WITH clause spans the whole
"SELECT 1 UNION SELECT 1 FROM t1" structure, we don't have a top-
level UNION anymore.) But it shouldn't throw this error:

> ERROR: XX000: missing recursive reference
> LOCATION: checkWellFormedRecursion, parse_cte.c:896

We do get the right behaviors for WITHs that are down inside one
side or the other of the UNION:

WITH RECURSIVE t(n) AS (
(WITH t1 AS (SELECT 1 FROM t) SELECT 1 FROM t1)
UNION
SELECT 1)
SELECT * FROM t;
ERROR: recursive reference to query "t" must not appear within its non-recursive term
LINE 2: (WITH t1 AS (SELECT 1 FROM t) SELECT 1 FROM t1)
^

WITH RECURSIVE t(n) AS (
SELECT 1
UNION
(WITH t1 AS (SELECT 1 FROM t) SELECT 1 FROM t1))
SELECT * FROM t;
n
---
1
(1 row)

I think the case you show should be throwing

ERROR: recursive query "t" does not have the form non-recursive-term UNION [ALL] recursive-term

Will look closer later. Thanks for the report.

regards, tom lane