Re: [HACKERS] [PATCH] Lockable views

From: Robert Haas <robertmhaas(at)gmail(dot)com>
To: Tatsuo Ishii <ishii(at)sraoss(dot)co(dot)jp>
Cc: Thomas Munro <thomas(dot)munro(at)enterprisedb(dot)com>, Yugo Nagata <nagata(at)sraoss(dot)co(dot)jp>, "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: [HACKERS] [PATCH] Lockable views
Date: 2018-02-06 03:00:44
Message-ID: CA+TgmoZqDXb+ZBnBR9e8Pc=WkVAZ0yVqKyB_Mg14fySyOau7Eg@mail.gmail.com
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On Mon, Feb 5, 2018 at 8:18 PM, Tatsuo Ishii <ishii(at)sraoss(dot)co(dot)jp> wrote:
> We have: CREATE VIEW v1 AS SELECT * FROM t1 WHERE i = (SELECT i FROM t2);
>
> 1. Session A tries to lock v1 (I suppose it tries to acquire lock in
> the order of t1, then t2). A acquires lock on t1 but yet on t2.
>
> 2. Another session B acquires lock on t2.
>
> 3. A continues to try to acquire lock on t2 (blocked).
>
> 4. B tries to acquire lock on t1. Deadlock occurs.

True. But the same exact analysis also applies to this definition,
which contains no subquery:

CREATE VIEW v1 AS SELECT t1.* FROM t1, t2 WHERE t1.i = t2.i;

--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company

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