Date: Mon, 28 Aug 2023 02:49:08 +0900
From: Yugo NAGATA <nagata@sraoss.co.jp>
To: jian he <jian.universality@gmail.com>
Cc: pgsql-hackers@postgresql.org
Subject: Re: Incremental View Maintenance, take 2
Message-Id: <20230828024908.2667bcde8d2963256375bd6c@sraoss.co.jp>
In-Reply-To: <CACJufxF-HGe9zLaGaSryeYVq9abz2FyKKtdgghNWktkjnFXOJQ@mail.gmail.com>
References: <20230601235909.0e1572c27e59112f9d0cbe86@sraoss.co.jp>
	<20230601034703.9e4f81f5d92ae6e3949b84d2@sraoss.co.jp>
	<CACJufxE8Kct5=c1KKi_JgP09WApCk0Myk6=a5xo05_J_mB7hRQ@mail.gmail.com>
	<20230628170604.505955118ac2f91abd554f13@sraoss.co.jp>
	<CACJufxEA-V+0Fa3Q6xQrFwG6wLs4DsX7E4exdfA=rO-70svmBw@mail.gmail.com>
	<CACJufxHZkF_e4JvcXCfaYkOSs0p6-S2SFQk1+iOHdDL6kvngKg@mail.gmail.com>
	<CACJufxHtG9h_1V2pr+Hx9amWE9fW0z3dcW9t8yMiBgiSsEjBQA@mail.gmail.com>
	<CACJufxHVrgBM1FhM7=df9Cky_uPJ8o3wTjT0iKJWDgmbYPTYqw@mail.gmail.com>
	<CACJufxHJQ-Tvxyj1Fy5O3ULXn912bnF1pHfCmLTR72Qcy2_-iQ@mail.gmail.com>
	<CACJufxHMG9Pmc=W8QMHvk_RwUBABDZNh9HgO4JSQtp1+JUPTJg@mail.gmail.com>
	<CACJufxF-HGe9zLaGaSryeYVq9abz2FyKKtdgghNWktkjnFXOJQ@mail.gmail.com>
Mime-Version: 1.0
Content-Type: text/plain; charset=US-ASCII
Content-Transfer-Encoding: 7bit
Archived-At: <https://www.postgresql.org/message-id/20230828024908.2667bcde8d2963256375bd6c%40sraoss.co.jp>
Precedence: bulk

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>