I have DB with all character fields of UTF8 charset. I've connected to DB with UTF8 charset and tried to add computed field to existing table:

1) ALTER TABLE "Test" ADD STR1 COMPUTED BY ('BLA-BLA-BLA');

After this i've got next error when tried to read table's data: "Arithmetic exception, numeric overflow or string truncation"

2) ALTER TABLE "Test" ADD STR2 COMPUTED BY (_UTF8 'BLA-BLA-BLA');

First time server crashes with "Terminated abnormally" in log file. After server restarted field wass successfully created, but when i tried to read records i've got same error as above.