From: | Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com> |
---|---|
To: | Peter Eisentraut <peter(dot)eisentraut(at)2ndquadrant(dot)com> |
Cc: | pgsql-hackers <pgsql-hackers(at)postgresql(dot)org>, Sergei Kornilov <sk(at)zsrv(dot)org>, Michael Paquier <michael(dot)paquier(at)gmail(dot)com>, Jaime Casanova <jaime(dot)casanova(at)2ndquadrant(dot)com> |
Subject: | Re: [HACKERS] generated columns |
Date: | 2019-01-13 14:31:23 |
Message-ID: | CAFj8pRB=L3At5R=DXWRw7OFCdaeZ_+3S5e==DbGgD_7POsqngA@mail.gmail.com |
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Lists: | pgsql-hackers |
ne 13. 1. 2019 v 10:43 odesílatel Peter Eisentraut <
peter(dot)eisentraut(at)2ndquadrant(dot)com> napsal:
> 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 understand - it is logical. But it is sad, so this feature is not
complete. The benefit is not too big - against functional indexes or views.
But it can be first step.
>
> > 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.
>
ok
> --
> Peter Eisentraut http://www.2ndQuadrant.com/
> PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
>
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