Postgres, How can I deny to create a database with a werid name (trailing space, leading space, or even avlid using space in a database name) - bash

Question

I'm trying to add some constraints on database creation command in PostgreSQL.
Currently, I could do
psql -c "CREATE database \" x y\"\"z' \""
Then, I will get a database named literally " x y"z' " (without the double-quotes boundary).
It seems that pgsql supports any characters in it's database name, which is cool.
But it leads me headaches when I am doing automation stuff with bash script.
Yes, some additional work could be done to handle these cases in script. But I think these kind of names are actually meaningless (at least in my situation :), so, is there a way to add some constraints on database naming. For example, only allow [a-zA-Z0-9_.]+.

Answer 1

Just do not use double quotes, which you should avoid anyway if at all possible. See Documentation:
SQL identifiers and key words must begin with a letter (a-z, but also
letters with diacritical marks and non-Latin letters) or an underscore
(_). Subsequent characters in an identifier or key word can be
letters, underscores, digits (0-9), or dollar signs ($). Note that
dollar signs are not allowed in identifiers according to the letter of
the SQL standard, so their use might render applications less
portable. The SQL standard will not define a key word that contains
digits or starts or ends with an underscore, so identifiers of this
form are safe against possible conflict with future extensions of the
standard. ... There is a second kind of identifier: the delimited
identifier or quoted identifier. It is formed by enclosing an
arbitrary sequence of characters in double-quotes ("). A delimited
identifier is always an identifier, never a key word. ... Quoted
identifiers can contain any character, except the character with code
zero. (To include a double quote, write two double quotes.) This
allows constructing table or column names that would otherwise not be
possible, such as ones containing spaces or ampersands.
Not doubling quoting in you examples makes those names invalid and Postgres has no problem telling about it. So just do not use them.
Alternately you could create an event trigger. Within there you can restrict object names as needed, esp useful if you have strict naming standards. This would allow for database enforcement of those standards;
create function app_validate_table_name()
returns event_trigger
language 'plpgsql'
as $$
begin
if obj.object_identity ~! '[A-Za-z$_][[A-Za-z0-9$_]{0,62}'
then
raise exception 'App Error: Request Name (%) is invalid for <Your App Name here>',obj.object_identity;
end if
return;
end ;
$$;
create event trigger app_table_event_trigger on ddl_command_end
when tag in ('ALTER TABLE', 'CREATE TABLE')
execute procedure app_validate_table_name();
While the same can be applied to other objects it unfortunately does not seem to apply to creating a database itself.
Disclamer: The above has NOT been tested.