Re: pg_system_identifier()

From: Robert Haas <robertmhaas(at)gmail(dot)com>
To: Satoshi Nagayasu <snaga(at)uptime(dot)jp>
Cc: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Andres Freund <andres(at)2ndquadrant(dot)com>, Josh Berkus <josh(at)agliodbs(dot)com>, Fujii Masao <masao(dot)fujii(at)gmail(dot)com>, Michael Paquier <michael(dot)paquier(at)gmail(dot)com>, Jim Nasby <jim(at)nasby(dot)net>, Greg Stark <stark(at)mit(dot)edu>, Hannu Krosing <hannu(at)2ndquadrant(dot)com>, Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: pg_system_identifier()
Date: 2013-09-17 14:57:46
Message-ID: CA+TgmoYzaAjFXJZ3MT+XCquL8KB=JkUfYEAGtdsDQOqppp9thg@mail.gmail.com
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On Mon, Sep 16, 2013 at 1:25 AM, Satoshi Nagayasu <snaga(at)uptime(dot)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.

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

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