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From: Peter Eisentraut <peter.eisentraut@2ndquadrant.com>
To: Pavel Stehule <pavel.stehule@gmail.com>
Cc: pgsql-hackers <pgsql-hackers@postgresql.org>
Cc: Sergei Kornilov <sk@zsrv.org>
Cc: Michael Paquier <michael.paquier@gmail.com>
Cc: Jaime Casanova <jaime.casanova@2ndquadrant.com>
Subject: Re: [HACKERS] generated columns
Date: Sun, 13 Jan 2019 10:43:28 +0100
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On 11/01/2019 16:22, Pavel Stehule wrote:
> The documentation contains paragraph
> 
> +      The generation expression can only use immutable functions and cannot
> +      use subqueries or reference anything other than the current row
> in any
> +      way.
> 
> It is necessary for stored columns?

See here:
https://www.postgresql.org/message-id/b5c27634-1d44-feba-7494-ce5a31f914ca@2ndquadrant.com

> I tested it with pseudo constant - current_timestamp, session_user. But
> current_database() is disallowed.
> 
> on second hand, this is strange
> 
> postgres=# create table foo3 (inserted text generated always as
> (current_timestamp) virtual);
> CREATE TABLE

Ah, the volatility checking needs some improvements.  I'll address that
in the next patch version.

-- 
Peter Eisentraut              http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services




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