Code review comment for lp:~sergei.glushchenko/percona-xtrabackup/xb20-bug932623

Sergei,

Tables may be renamed into another database directory, which this fix doesn't take into account. I think we should do space ID verification in a different way:

let's initialize fil_system, in the same --backup or --prepare does it and then use fil_space_get_by_id() and possibly fil_space_get_by_name().

Now the problem is that fil_system will also be initialized later in --prepare when innodb_init() is called, and initializing fil_system multiple times in the same process is tricky. I had to write some extra code for that in the compact backups branch, see xb_data_files_init() and xb_data_files_close() in lp:~akopytov/percona-xtrabackup/compact-backups.

Other minor things:
- s/matchong/matching
- "cat $topdir/inc/ibdata1.meta" in the test case was probably just for debugging and doesn't make any sense as far as regression testing is concerned.