Re: Incremental View Maintenance, take 2

On Sun, 2 Jul 2023 10:38:20 +0800
jian he <jian(dot)universality(at)gmail(dot)com> wrote:

> ok. Now I really found a small bug.
>
> this works as intended:
> BEGIN;
> CREATE INCREMENTAL MATERIALIZED VIEW test_ivm AS SELECT i, MIN(j) as
> min_j FROM mv_base_a group by 1;
> INSERT INTO mv_base_a select 1,-2 where false;
> rollback;
>
> however the following one:
> BEGIN;
> CREATE INCREMENTAL MATERIALIZED VIEW test_ivm1 AS SELECT MIN(j) as
> min_j FROM mv_base_a;
> INSERT INTO mv_base_a select 1, -2 where false;
> rollback;
>
> will evaluate
> tuplestore_tuple_count(new_tuplestores) to 1, it will walk through
> IVM_immediate_maintenance function to apply_delta.
> but should it be zero?

This is not a bug because an aggregate without GROUP BY always
results one row whose value is NULL.

The contents of test_imv1 would be always same as " SELECT MIN(j) as min_j
FROM mv_base_a;", isn't it?

Regards,
Yugo Nagata

--
Yugo NAGATA <nagata(at)sraoss(dot)co(dot)jp>