I've been wondering recently why the external canonical form of types
like char and varchar doesn't match the typname in pg_type.
Additionally, the alternative/extended names are hardcoded in
format_type.c rather than being an additional column in that catalog
table.
I would have assumed there were largely historical reasons for this,
but I see the following relevant comments in that file:
/*
* See if we want to special-case the output for certain built-in types.
* Note that these special cases should all correspond to special
* productions in gram.y, to ensure that the type name will be taken as a
* system type, not a user type of the same name.
*
* If we do not provide a special-case output here, the type name will be
* handled the same way as a user type name --- in particular, it will be
* double-quoted if it matches any lexer keyword. This behavior is
* essential for some cases, such as types "bit" and "char".
*/
But I'm not following what would actually break if it weren't done
this way. Is the issue that a user defined type (in a different
schema, perhaps?) could overshadow the system type?
And would it make more sense (though I'm not volunteering right now to
write such a patch :D) to have these names be an additional column on
pg_type so that they can be queried by the user?
Thanks,
James