From: Andres Freund <andres@2ndquadrant.com>
To: Robert Haas <robertmhaas@gmail.com>
Cc: Satoshi Nagayasu <snaga@uptime.jp>
Cc: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Josh Berkus <josh@agliodbs.com>
Cc: Fujii Masao <masao.fujii@gmail.com>
Cc: Michael Paquier <michael.paquier@gmail.com>
Cc: Jim Nasby <jim@nasby.net>
Cc: Greg Stark <stark@mit.edu>
Cc: Hannu Krosing <hannu@2ndquadrant.com>
Cc: Alvaro Herrera <alvherre@2ndquadrant.com>
Cc: PostgreSQL-development <pgsql-hackers@postgresql.org>
Subject: Re: pg_system_identifier()
Date: Tue, 17 Sep 2013 16:59:59 +0200
Message-ID: <20130917145959.GL5452@awork2.anarazel.de> (raw)
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On 2013-09-17 10:57:46 -0400, Robert Haas wrote:
> On Mon, Sep 16, 2013 at 1:25 AM, Satoshi Nagayasu <snaga@uptime.jp> wrote:
> > How about adding new system view with new function which returns
> > a single pg_controldata value in text type, and using a cast for
> > each column in the view definition?
> >
> > CREATE VIEW pg_catalog.pg_controldata AS
> > SELECT pg_controldata('control_version')::integer AS control_version,
> > pg_controldata('catalog_version')::integer AS catalog_version,
> > pg_controldata('system_identifier')::bigint AS system_identifier,
> > ...
> > pg_controldata('next_xlog_file')::char(25) AS next_xlog_file,
> > ...
> > pg_controldata('encoding')::text AS encoding;
> >
> > Given that the view can work like a SRF, and it allows us to retrieve
> > all the values of pg_controldata with appropriate types in single
> > record from the view:
>
> I like this idea. I think having an easy way to get the values with
> the right types will be a plus. But adding a separate function for
> each field seems excessive, so I think this is a good compromise.
Why not add a single function returning a composite type then? That'd at
least have a chance of returning consistent values for the individual
values that change during runtime. It would also produce proper errors
when you load a view using columns that don't exist anymore instead of
just at runtime.
Greetings,
Andres Freund
--
Andres Freund http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services
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Cc: andres@2ndquadrant.com, robertmhaas@gmail.com, snaga@uptime.jp, tgl@sss.pgh.pa.us, josh@agliodbs.com, masao.fujii@gmail.com, michael.paquier@gmail.com, jim@nasby.net, stark@mit.edu, hannu@2ndquadrant.com, alvherre@2ndquadrant.com
Subject: Re: pg_system_identifier()
In-Reply-To: <20130917145959.GL5452@awork2.anarazel.de>
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