Localizing stored functions by replacing placeholders in their body

[Alexander Farber <alexander.farber@xxxxxxxxx>]

Hello,

I have an app using PostgreSQL 13.2, in 6 different human languages (each using different database, but same source code).

Currently to localize strings return/set by the stored functions I either get localized strings from a table or maintain stored function source code in 6 different languages.

This is not very comfortable and I would like to switch to using same source code (regardless of the human language) for all stored functions. And after deploying a database, just run few commands to replace placeholders in the stored functions.

So I am trying:

CREATE OR REPLACE FUNCTION localize_hello()

        RETURNS text AS

$func$

        SELECT '$(hello)';

$func$ LANGUAGE sql IMMUTABLE;

And then:

update pg_proc set prosrc = regexp_replace(prosrc, '$\(\w+\)','Hi english','g') where proname='localize_hello';

But the error is:

ERROR:  permission denied for table pg_proc

So I connect as user "postgres" and then the command seemingly succeeds, but when I call it, the delivered string is still old:

 select * from localize_hello();

 localize_hello

----------------

 $(hello)

(1 row)

Is this a right approach? Do you please have any advice here?

Thanks

Alex