Purpose of RDB$FUNCTION_NAME in RDB$CHARACTER_SETS and RDB$COLLATIONS, and does it need schema support

[Mark Rotteveel]

The RDB$CHARACTER_SETS and RDB$COLLATIONS tables have a column
RDB$FUNCTION_NAME.

The language reference documents it for RDB$CHARACTER_SETS as:

"""
For a user-defined character set that is accessed via an external
function, the name of the external function
"""

And for RDB$COLLATIONS as:

"""
Not currently used
"""

Is this in anyway still supported (if ever)?

If so, shouldn't they also receive a RDB$FUNCTION_SCHEMA_NAME to point
to the declaration of the external function in RDB$FUNCTIONS?

If not, shouldn't this column simply be removed from both tables?

Mark
--
Mark Rotteveel

[Dmitry Yemanov]

16.03.2026 16:35, 'Mark Rotteveel' via firebird-devel wrote:
>
> If not, shouldn't this column simply be removed from both tables?

Even if unused, they may be queried by connectivity drivers and they may
be outdated/unsupported to fix/adjust them easily. I always treat the
existing system schema as a lifetime contract with users and breaking it
just for cleanup is not something I'd support.


Dmitry

[Mark Rotteveel]

Well, if it is truly unused, we could also consider at least changing
the type to a domain, e.g. "RDB$UNUSED_NAME", declared as CHAR(1)
CHARACTER SET ASCII and save 251 bytes in the in-memory image of each row ;)

Mark
--
Mark Rotteveel

[F. D. Castel]

While I like the idea and think it makes sense, it would STILL introduce a breaking change.

For example: Delphi VCL datasets often persist column metadata in .dfm files, and they can raise runtime exceptions when that metadata no longer matches. Even something as simple as changing a column’s size can break older clients. Not that they would actually use the column, but plenty of people seem to love using `SELECT *` for some crazy reason...

I’m fully supportive of modernization and removing legacy crutches, but in this case I have to admit that Dmitry’s approach is ultimately the safer option.