for more details about identifiers in SQL, see the page

1. identifiers are names of different staff (spaces, indexes, sequences...)
2. all printable unicode characters allowed in identifiers
3. max identifier length is 65000

Tarantool allow identifier contain any printable Unicode character. This constraint was inspired by SQL ANSI ISO, which allows delimited identifier contain any valid Unicode character. The check is performed with help of ICU library.

1. space names
2. index names
3. column names
4. collation names
5. sequence names
6. function names
7. user names
8. role names
9. engine names (but it hasn't any API)

1. REPLACEMENT_CHARACTER (0xFFFD)
2. U_UNASSIGNED
3. U_LINE_SEPARATOR
4. U_CONTROL_CHAR
5. U_PARAGRAPH_SEPARATOR

for more info, see test/box/lua/identifier.lua and tests which uses it

The constraint is similar to glibc isprint(wchar) == true.