Re: New variable server_version_num

Quoth david(at)fetter(dot)org (David Fetter):
> On Tue, Aug 01, 2006 at 12:37:48PM -0500, Jim C. Nasby wrote:
>> On Sun, Jul 30, 2006 at 11:27:33AM -0400, Tom Lane wrote:
>> > David Fetter <david(at)fetter(dot)org> writes:
>> > > On Sat, Jul 29, 2006 at 09:44:10PM -0400, Tom Lane wrote:
>> > >> The correct solution is for client-side libraries to provide
>> > >> the feature.
>> >
>> > > Not if the app is written in SQL, as the bootstrap, regression
>> > > test, etc. code for modules frequently is.
>> >
>> > SQL doesn't really have any conditional ability strong enough to
>> > deal with existence or non-existence of features. What are you
>> > hoping to do, a CASE expression? Both arms of the CASE still have
>> > to parse, so I remain unconvinced that there are real world uses.
>
> CREATE OR REPLACE FUNCTION version_new_enough(
> in_version INTEGER
> )
> RETURNS BOOLEAN
> LANGUAGE sql
> AS $$
> SELECT
> COALESCE(
> s.setting::INTEGER, /* Cast setting to integer if it's there */
> $1 - 1 /* Otherwise, guarantee a lower number than the input */
> ) >= $1
> FROM
> (SELECT 'server_version_num'::text AS name) AS foo
> LEFT JOIN
> pg_catalog.pg_settings s
> ON (foo.name = s.name)
> $$;
>
>> There's also plpgsql, which afaik has no way to get the version
>> number (other than slogging though the output of version()).
>
> Right. String-mashing is great when you have to do it, but this patch
> sets it up so you don't have to. :)

There's *some* data to be gotten from
select setting from pg_catalog.pg_settings where name = 'server_version';

Seems to me that value isn't without its uses...

cbbrowne(at)dba2:pgsql-HEAD/doc/src/sgml> for port in 5432 5533 5532 5882; do
for> psql -p $port -h localhost -d template1 -c "select '$port',
setting from pg_catalog.pg_settings where name like 'server_version';"
for> done
?column? | setting
----------+---------
5432 | 7.4.13
(1 row)

?column? | setting
----------+---------
5533 | 7.4.10
(1 row)

?column? | setting
----------+---------
5532 | 8.0.5
(1 row)

?column? | setting
----------+----------
5882 | 8.2devel
(1 row)

If I wanted to, it oughtn't be difficult to "string smash" those
settings into something very nearly useful...
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