consistently issue a
Note 1618 DATA DIRECTORY option ignored
Note 1618 INDEX DIRECTORY option ignored
in archive/csv/innodb/rocksdb whenever an option is ignored.
Note that csv doesn't say "INDEX DIRECTORY option ignored"
because it does not create index files at all anywhere.
Other engines don't say "INDEX DIRECTORY option ignored"
if the table has no indexes.
additionally InnoDB doesn't say that if INDEX DIRECTORY is
the same as DATA DIRECTORY, because in that case indexes are
technically stored in INDEX DIRECTORY.
collateral fix: use strmake to zero-terminate the string
The InnoDB DATA DIRECTORY attribute is not implemented via
symbolic links but something similar, *.isl files that contain
the names of data files.
InnoDB failed to ignore the DATA DIRECTORY attribute even though
the server was started with --skip-symbolic-links.
Native ALTER TABLE in InnoDB will retain the DATA DIRECTORY attribute
of the table, no matter if the table will be rebuilt or not.
Generic ALTER TABLE (with ALGORITHM=COPY) as well as TRUNCATE TABLE
will discard the DATA DIRECTORY attribute.
All tests have been run with and without the ./mtr option
--mysqld=--skip-symbolic-links
and some tests that use the InnoDB DATA DIRECTORY attribute
have been adjusted for this.
