Subject: Re: how to use function from different database
To: pgsql-sql@lists.postgresql.org
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From: Rob Sargent <robjsargent@gmail.com>
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Date: Thu, 30 Jul 2020 18:28:44 -0600
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On 7/30/20 6:03 PM, Bhupendra Babu wrote:
> Hi,
> 
> I created a generic function (DATEFIFF) login to postgres database using 
> psql. ANd I wanted to use across the entire instance , from all other 
> databases.
> 
> postgres=> CREATE FUNCTION DateDiff (units VARCHAR(30), start_t 
> TIMESTAMP, end_t TIMESTAMP)
> postgres->      RETURNS INT AS $$
> postgres$>    DECLARE
> postgres$>      diff_interval INTERVAL;
> ...
> ...
> 
> grant execute on function DATEDIFF to public;
> grant execute on function DATEDIFF(varchar,timestamp,timestamp) to public;
> 
> I tried both the grant one at a time, none of them works.
> ------------------------------------------
> Connected to another database
> \c application1
> 
> application1=> SELECT * from DATEDIFF('second', '2011-12-30 
> 08:54:55'::timestamp, '2011-12-30 08:56:10'::timestamp);
> ERROR:  function datediff(unknown, timestamp without time zone, 
> timestamp without time zone) does not exist
> LINE 1: SELECT * from DATEDIFF('second', '2011-12-30 08:54:55'::time...
>                        ^
> HINT:  No function matches the given name and argument types. You might 
> need to add explicit type casts.
> application1=>
> ------------------------------------------
> 
> How can I use this function across my entire postgresql instance from 
> any databases ?
> 
> -- 
> Thanks.
> Bhupendra B Babu
You can create public.datadiff in the template1 database. Thereafter all 
created databases in that cluster will get the function.  However, for 
existing databases, you'll need to apply the function by hand.  I 
recommend using the public schema explicitly.  It should be fairly 
straight forward to script this.

superuser privilege is of course required.