Date: Wed, 4 Dec 2019 13:37:57 +0200
From: Eugen Konkov <kes-kes@yandex.ru>
Message-ID: <471116573.20191204133757@yandex.ru>
To: Bruce Momjian <bruce@momjian.us>
CC: PostgreSQL-development <pgsql-hackers@postgreSQL.org>,
 pgsql-docs@lists.postgresql.org
Subject: Re: Does 'instead of delete' trigger support modification of OLD
In-Reply-To: <20191107222818.GA18712@momjian.us>
References: <919823407.20191029175436@yandex.ru>
 <20191106185935.GE1843@momjian.us>
  <1771593631.20191107112032@yandex.ru> <352093181.20191107112429@yandex.ru>
  <20191107212655.GA487@momjian.us> <20191107222818.GA18712@momjian.us>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Transfer-Encoding: 7bit
Precedence: bulk

Hi again.

> Thinking some more on this, I now don't think a TODO makes sense, so I
> have removed it.

Please look into this example: https://dbfiddle.uk/?rdbms=postgres_12&fiddle=95ed9fab6870d7c4b6266ea4d93def13
This is real life code from our production.

You  can  see that this is important to get correct info about deleted
data

    -- EXPECTED app_period: ["2018-08-20", "2018-08-25")
    -- ACTUAL   app_period: ["2018-08-14", )

> Triggers are designed to check and modify input data, and since DELETE
> has no input data, it makes no sense.

Please   put   back   into   TODO  list this feature  request to allow
triggers to modify output data.

INPUT     -- receives data                         OK (behavior is expected)
UPDATE  -- receives and returns data     OK (behavior is expected)
DELETE  -- returns data                           FAIL (behavior is not expected)

This  is  inconsistent  to  allow  modify  output  data for UPDATE and
restrict to do this for DELETE


Thank you

-- 
Best regards,
Eugen Konkov