You cannot code a full outer join within the recursive statement of a recursive view definition.
Full outer joins can be used without restriction in the seed statement of a recursive view definition.
The first recursive view definition demonstrates a correct use of a full outer join, which is bold. The usage is valid because the full outer join is coded within the seed statement of the view definition.
CREATE RECURSIVE VIEW rec (f1, mycount) AS (
SELECT a1, 0 AS mycount
FROM nonrec1 FULL OUTER JOIN nonrec2 ON nonrec1.a1 = nonrec2.a2
UNION ALL
SELECT a2, mycount + 1
FROM nonrec, rec
WHERE rec.mycount <= 100);
The second recursive view definition demonstrates a non-valid use of a full outer join, which is bold. The usage is not valid because the recursive relation in the recursive statement of the view definition is used as the inner relation in the full outer join.
CREATE RECURSIVE VIEW rec (f1, mycount) AS (
SELECT a1, 0 AS mycount
FROM nonrec
UNION ALL
SELECT a2, mycount + 1
FROM nonrec FULL OUTER JOIN rec ON nonrec.a1 = rec.f1
WHERE rec.mycount <= 100);