Re: pg_system_identifier()

On Tue, Sep 17, 2013 at 10:59 AM, Andres Freund <andres@2ndquadrant.com> wrote:
> 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.

Hmm.  Yeah, that might be better.

-- 
Robert Haas
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