* If the tablespace id of the IMPORTing instance had changed then the import would fail. * If the table and index ids in the tablespace were different than the importing server.因为两个实例表创建的顺序可能不一致，导致tablespace id会不一致。[参照](http://www.jzxue.com/shujuku/mysql/201109/13-8842.html) * InnoDB uses a global row id, this is used for tables without an explicit primary key, the row id if present in a to be imported tablespace had to be lower than importing server current maximum.当表没有显示的制定主键时，innodb使用隐藏的row id来表示主键，这个保存在共享表空间中会存在不一致。 * Maximum LSN of the tablespace had to be lower than the server current max LSN * The maximum trx id of the tablespace had to be lower than the server current max trx id. * Purge and change buffer issues**The Solution** Do the flush (export) properly and also the import. During flushing we disable purge, merge all pending change buffer entries to the tablespace and then flush all the dirty pages to disk. **Note: Purge will remain disabled until UNLOCK TABLES; is issued**. Write out a meta-data file that contains the table schema, hostname of the exporting server, page size of the exporting instance and the highest autoinc value in memory etc.. So that when we do an import we can check if the table schema matches (currently ignores foreign key relationships) and also restore the autoinc value. This meta-data file is created in the same directory as the tablespace, it has a suffix of .cfg. If the tables is named _customer_ then the meta-data file will be named _customer.cfg_ and the tablespace will be named _customer.ibd._ Note: FLUSH TABLES and IMPORT only work for tables that are stored outside the system tablespace, in their own tablespace. The InnoDB config parameter [innodb_file_per_table](http://dev.mysql.com/doc/refman/5.6/en/innodb-parameters.html#sysvar_innodb_file_per_table "innodb_file_per_table") must be set when creating the table.**Example** If you want to backup a single table: CREATE DATABASE ftwrl; CREATE TABLE ftwrl.t (C INT) ENGINE=InnoDB; INSERT INTO ftwrl.t VALUES(1),(2),(3); SELECT * FROM ftwrl.t; FLUSH TABLES ftwrl.t WITH READ LOCK; From the command line, copy the t.ibd and t.cfg to your backup directory. The files should in the ftwrl/ sub-directory under [datadir](http://dev.mysql.com/doc/refman/5.6/en/mysql-install-db.html#option_mysql_install_db_datadir "--datadir"). UNLOCK TABLES; - **Note: This will remove the t.cfg file.** DROP TABLE ftwrl.t; CREATE TABLE ftwrl.t (C INT) ENGINE=InnoDB; ALTER TABLE ftwrl.t DISCARD TABLESPACE; The DISCARD tablespace will rename the t.ibd file to t.ibt in the same directory, you have to remove this file manually for now. Once you've removed this file, copy the backed up tablespace t.ibd and the meta-data file t.cfg to the ftwrl/ sub-directory. Then issue the folowing: ALTER TABLE ftwrl.t IMPORT TABLESPACE; CHECK TABLE ftwrl.t; SELECT * FROM t; You should be good to go. If you want to backup multiple tables together then the syntax for that is: FLUSH TABLES t1, t2, ..., tn WITH READ LOCK; Copy as before but this time the multiple tablespaces and meta-data files UNLOCK TABLES; Then first discard the tablespace as above followed by an import as above. **Other changes** Errors and warnings will be pushed to the client so that the user doesn't need to poke around in the server error log files to check why an operation failed. The intention is to send enough information to the user so that the problem can be clearly identified and understood. **Conclusion** The syntax for "export" is not finalised yet and may change, for now the above examples using FLUSH TABLES WITH READ LOCK should work. To export tables that are in a foreign key relationship you must export and import all the tables together, otherwise you may end up with inconsistencies. The export/import doesn't work on partitioned tables, this limitation will be addressed later. A matching table definition must exist in the importing server instance, currently we don't automagically create the table using the saved meta-data during import. The .cfg format is not written in stone yet, we may add more data to this file, e.g., when we add partition support.