On Thu, May 18, 2023 at 3:34 AM Tom Lane <t...@sss.pgh.pa.us> wrote:
> After some poking at it I hit on what seems like a really simple > solution: we should be checking syn_righthand not min_righthand > to see whether a Var should be considered nullable by a given OJ. > Maybe that's still not quite right, but it seems like it might be > right given that the last fix reaffirmed our conviction that Vars > should be marked according to the syntactic structure. I thought about this solution before but proved it was not right in https://www.postgresql.org/message-id/CAMbWs48fObJJ%3DYVb4ip8tnwxwixUNKUThfnA1eGfPzJxJRRgZQ%40mail.gmail.com I checked the query shown there and it still fails with v3 patch. explain (costs off) select * from t1 left join (select t2.x from t2 left join t3 on t2.x where t3.x is null) s left join t4 on s.x on s.x = t1.x; server closed the connection unexpectedly The failure happens when we are forming the join of (t1/t2) to t3. Consider qual 't3.x is null'. It's a non-clone filter clause so clause_is_computable_at is supposed to think it's applicable here. We have an Assert for that. However, when checking outer join t1/t2, which has been performed but is not listed in the qual's nullingrels, clause_is_computable_at would think it'd null vars of the qual if we check syn_righthand not min_righthand, and get a conclusion that the qual is not applicable here. This is how the Assert is triggered. Thanks Richard
