Re: Incremental View Maintenance, take 2

On Sun, 2 Jul 2023 10:38:20 +0800
jian he <jian.universality@gmail.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@sraoss.co.jp>