Chapter 15 The InnoDB Storage Engine

15.6.1.3 Importing InnoDB Tables

This section describes how to import tables using the Transportable Tablespaces feature, which permits importing tables, partitioned tables, or individual table partitions that reside in file-per-table tablespaces. There are many reasons why you might want to import tables:

To run reports on a non-production MySQL server instance to avoid placing extra load on a production server.
To copy data to a new replica server.
To restore a table from a backed-up tablespace file.
As a faster way of moving data than importing a dump file, which requires reinserting data and rebuilding indexes.
To move a data to a server with storage media that is better suited to your storage requirements. For example, you might move busy tables to an SSD device, or move large tables to a high-capacity HDD device.

The Transportable Tablespaces feature is described under the following topics in this section:

Prerequisites

The innodb_file_per_table variable must be enabled, which it is by default.
The page size of the tablespace must match the page size of the destination MySQL server instance. InnoDB page size is defined by the innodb_page_size variable, which is configured when initializing a MySQL server instance.
If the table has a foreign key relationship, foreign_key_checks must be disabled before executing DISCARD TABLESPACE. Also, you should export all foreign key related tables at the same logical point in time, as ALTER TABLE ... IMPORT TABLESPACE does not enforce foreign key constraints on imported data. To do so, stop updating the related tables, commit all transactions, acquire shared locks on the tables, and perform the export operations.
When importing a table from another MySQL server instance, both MySQL server instances must have General Availability (GA) status and must be the same version. Otherwise, the table must be created on the same MySQL server instance into which it is being imported.
If the table was created in an external directory by specifying the DATA DIRECTORY clause in the CREATE TABLE statement, the table that you replace on the destination instance must be defined with the same DATA DIRECTORY clause. A schema mismatch error is reported if the clauses do not match. To determine if the source table was defined with a DATA DIRECTORY clause, use SHOW CREATE TABLE to view the table definition. For information about using the DATA DIRECTORY clause, see Section 15.6.1.2, “Creating Tables Externally”.
If a ROW_FORMAT option is not defined explicitly in the table definition or ROW_FORMAT=DEFAULT is used, the innodb_default_row_format setting must be the same on the source and destination instances. Otherwise, a schema mismatch error is reported when you attempt the import operation. Use SHOW CREATE TABLE to check the table definition. Use SHOW VARIABLES to check the innodb_default_row_format setting. For related information, see Defining the Row Format of a Table.

Importing Tables

This example demonstrates how to import a regular non-partitioned table that resides in a file-per-table tablespace.

On the destination instance, create a table with the same definition as the table you intend to import. (You can obtain the table definition using SHOW CREATE TABLE syntax.) If the table definition does not match, a schema mismatch error is reported when you attempt the import operation.
```
mysql> USE test;
mysql> CREATE TABLE t1 (c1 INT) ENGINE=INNODB;
```
On the destination instance, discard the tablespace of the table that you just created. (Before importing, you must discard the tablespace of the receiving table.)
```
mysql> ALTER TABLE t1 DISCARD TABLESPACE;
```
On the source instance, run FLUSH TABLES ... FOR EXPORT to quiesce the table you intend to import. When a table is quiesced, only read-only transactions are permitted on the table.
```
mysql> USE test;
mysql> FLUSH TABLES t1 FOR EXPORT;
```
FLUSH TABLES ... FOR EXPORT ensures that changes to the named table are flushed to disk so that a binary table copy can be made while the server is running. When FLUSH TABLES ... FOR EXPORT is run, InnoDB generates a .cfg metadata file in the schema directory of the table. The .cfg file contains metadata that is used for schema verification during the import operation.
Copy the .ibd file and .cfg metadata file from the source instance to the destination instance. For example:
```
shell> scp /path/to/datadir/test/t1.{ibd,cfg} destination-server:/path/to/datadir/test
```
The .ibd file and .cfg file must be copied before releasing the shared locks, as described in the next step.

~~Note~~注意

If you are importing a table from an encrypted tablespace, InnoDB generates a .cfp file in addition to a .cfg metadata file. The .cfp file must be copied to the destination instance together with the .cfg file. The .cfp file contains a transfer key and an encrypted tablespace key. On import, InnoDB uses the transfer key to decrypt the tablespace key. For related information, see Section 15.13, “InnoDB Data-at-Rest Encryption”.
On the source instance, use UNLOCK TABLES to release the locks acquired by the FLUSH TABLES ... FOR EXPORT statement:
```
mysql> USE test;
mysql> UNLOCK TABLES;
```

On the destination instance, import the tablespace:

mysql> USE test;
mysql> ALTER TABLE t1 IMPORT TABLESPACE;

Importing Partitioned Tables

This example demonstrates how to import a partitioned table, where each table partition resides in a file-per-table tablespace.

On the destination instance, create a partitioned table with the same definition as the partitioned table that you want to import. (You can obtain the table definition using SHOW CREATE TABLE syntax.) If the table definition does not match, a schema mismatch error is reported when you attempt the import operation.
```
mysql> USE test;
mysql> CREATE TABLE t1 (i int) ENGINE = InnoDB PARTITION BY KEY (i) PARTITIONS 3;
```
In the /datadir/test directory, there is a tablespace .ibd file for each of the three partitions.
```
mysql> \! ls /path/to/datadir/test/
t1#p#p0.ibd  t1#p#p1.ibd  t1#p#p2.ibd
```
On the destination instance, discard the tablespace for the partitioned table. (Before the import operation, you must discard the tablespace of the receiving table.)
```
mysql> ALTER TABLE t1 DISCARD TABLESPACE;
```
The three tablespace .ibd files of the partitioned table are discarded from the /datadir/test directory.
On the source instance, run FLUSH TABLES ... FOR EXPORT to quiesce the partitioned table that you intend to import. When a table is quiesced, only read-only transactions are permitted on the table.
```
mysql> USE test;
mysql> FLUSH TABLES t1 FOR EXPORT;
```
FLUSH TABLES ... FOR EXPORT ensures that changes to the named table are flushed to disk so that binary table copy can be made while the server is running. When FLUSH TABLES ... FOR EXPORT is run, InnoDB generates .cfg metadata files in the schema directory of the table for each of the table's tablespace files.
```
mysql> \! ls /path/to/datadir/test/
t1#p#p0.ibd  t1#p#p1.ibd  t1#p#p2.ibd
t1#p#p0.cfg  t1#p#p1.cfg  t1#p#p2.cfg
```
The .cfg files contain metadata that is used for schema verification when importing the tablespace. FLUSH TABLES ... FOR EXPORT can only be run on the table, not on individual table partitions.
Copy the .ibd and .cfg files from the source instance schema directory to the destination instance schema directory. For example:
```
shell>scp /path/to/datadir/test/t1*.{ibd,cfg} destination-server:/path/to/datadir/test
```
The .ibd and .cfg files must be copied before releasing the shared locks, as described in the next step.

~~Note~~注意

If you are importing a table from an encrypted tablespace, InnoDB generates a .cfp files in addition to a .cfg metadata files. The .cfp files must be copied to the destination instance together with the .cfg files. The .cfp files contain a transfer key and an encrypted tablespace key. On import, InnoDB uses the transfer key to decrypt the tablespace key. For related information, see Section 15.13, “InnoDB Data-at-Rest Encryption”.
On the source instance, use UNLOCK TABLES to release the locks acquired by FLUSH TABLES ... FOR EXPORT:
```
mysql> USE test;
mysql> UNLOCK TABLES;
```
On the destination instance, import the tablespace of the partitioned table:
```
mysql> USE test;
mysql> ALTER TABLE t1 IMPORT TABLESPACE;
```

Importing Table Partitions

This example demonstrates how to import individual table partitions, where each partition resides in a file-per-table tablespace file.

In the following example, two partitions (p2 and p3) of a four-partition table are imported.

On the destination instance, create a partitioned table with the same definition as the partitioned table that you want to import partitions from. (You can obtain the table definition using SHOW CREATE TABLE syntax.) If the table definition does not match, a schema mismatch error is reported when you attempt the import operation.
```
mysql> USE test;
mysql> CREATE TABLE t1 (i int) ENGINE = InnoDB PARTITION BY KEY (i) PARTITIONS 4;
```
In the /datadir/test directory, there is a tablespace .ibd file for each of the four partitions.
```
mysql> \! ls /path/to/datadir/test/
t1#p#p0.ibd  t1#p#p1.ibd  t1#p#p2.ibd t1#p#p3.ibd
```
On the destination instance, discard the partitions that you intend to import from the source instance. (Before importing partitions, you must discard the corresponding partitions from the receiving partitioned table.)
```
mysql> ALTER TABLE t1 DISCARD PARTITION p2, p3 TABLESPACE;
```
The tablespace .ibd files for the two discarded partitions are removed from the /datadir/test directory on the destination instance, leaving the following files:
```
mysql> \! ls /path/to/datadir/test/
t1#p#p0.ibd  t1#p#p1.ibd
```
~~Note~~注意

When ALTER TABLE ... DISCARD PARTITION ... TABLESPACE is run on subpartitioned tables, both partition and subpartition table names are permitted. When a partition name is specified, subpartitions of that partition are included in the operation.
On the source instance, run FLUSH TABLES ... FOR EXPORT to quiesce the partitioned table. When a table is quiesced, only read-only transactions are permitted on the table.
```
mysql> USE test;
mysql> FLUSH TABLES t1 FOR EXPORT;
```
FLUSH TABLES ... FOR EXPORT ensures that changes to the named table are flushed to disk so that binary table copy can be made while the instance is running. When FLUSH TABLES ... FOR EXPORT is run, InnoDB generates a .cfg metadata file for each of the table's tablespace files in the schema directory of the table.
```
mysql> \! ls /path/to/datadir/test/
t1#p#p0.ibd  t1#p#p1.ibd  t1#p#p2.ibd t1#p#p3.ibd
t1#p#p0.cfg  t1#p#p1.cfg  t1#p#p2.cfg t1#p#p3.cfg
```
The .cfg files contain metadata that used for schema verification during the import operation. FLUSH TABLES ... FOR EXPORT can only be run on the table, not on individual table partitions.
Copy the .ibd and .cfg files for partition p2 and partition p3 from the source instance schema directory to the destination instance schema directory.
```
shell> scp t1#p#p2.ibd t1#p#p2.cfg t1#p#p3.ibd t1#p#p3.cfg destination-server:/path/to/datadir/test
```
The .ibd and .cfg files must be copied before releasing the shared locks, as described in the next step.

~~Note~~注意

If you are importing partitions from an encrypted tablespace, InnoDB generates a .cfp files in addition to a .cfg metadata files. The .cfp files must be copied to the destination instance together with the .cfg files. The .cfp files contain a transfer key and an encrypted tablespace key. On import, InnoDB uses the transfer key to decrypt the tablespace key. For related information, see Section 15.13, “InnoDB Data-at-Rest Encryption”.
On the source instance, use UNLOCK TABLES to release the locks acquired by FLUSH TABLES ... FOR EXPORT:
```
mysql> USE test;
mysql> UNLOCK TABLES;
```
On the destination instance, import table partitions p2 and p3:
```
mysql> USE test;
mysql> ALTER TABLE t1 IMPORT PARTITION p2, p3 TABLESPACE;
```
~~Note~~注意

When ALTER TABLE ... IMPORT PARTITION ... TABLESPACE is run on subpartitioned tables, both partition and subpartition table names are permitted. When a partition name is specified, subpartitions of that partition are included in the operation.

Limitations

The Transportable Tablespaces feature is only supported for tables that reside in file-per-table tablespaces. It is not supported for the tables that reside in the system tablespace or general tablespaces. Tables in shared tablespaces cannot be quiesced.
FLUSH TABLES ... FOR EXPORT is not supported on tables with a FULLTEXT index, as full-text search auxiliary tables cannot be flushed. After importing a table with a FULLTEXT index, run OPTIMIZE TABLE to rebuild the FULLTEXT indexes. Alternatively, drop FULLTEXT indexes before the export operation and recreate the indexes after importing the table on the destination instance.
Due to a .cfg metadata file limitation, schema mismatches are not reported for partition type or partition definition differences when importing a partitioned table. Column differences are reported.
Prior to MySQL 8.0.19, index key part sort order information is not stored to the .cfg metadata file used during a tablespace import operation. The index key part sort order is therefore assumed to be ascending, which is the default. As a result, records could be sorted in an unintended order if one table involved in the import operation is defined with a DESC index key part sort order and the other table is not. The workaround is to drop and recreate affected indexes. For information about index key part sort order, see Section 13.1.15, “CREATE INDEX Statement”.

The .cfg file format was updated in MySQL 8.0.19 to include index key part sort order information. The issue described above does not affect import operations between MySQL 8.0.19 server instances or higher.

Usage Notes

ALTER TABLE ... IMPORT TABLESPACE does not require a .cfg metadata file to import a table. However, metadata checks are not performed when importing without a .cfg file, and a warning similar to the following is issued:
```
Message: InnoDB: IO Read error: (2, No such file or directory) Error opening '.\
test\t.cfg', will attempt to import without schema verification
1 row in set (0.00 sec)
```
Importing a table without a .cfg metadata file should only be considered if no schema mismatches are expected. The ability to import without a .cfg file could be useful in crash recovery scenarios where metadata is not accessible.
On Windows, InnoDB stores database, tablespace, and table names internally in lowercase. To avoid import problems on case-sensitive operating systems such as Linux and Unix, create all databases, tablespaces, and tables using lowercase names. A convenient way to ensure that names are created in lowercase is to set lower_case_table_names to 1 before initializing the server. (It is prohibited to start the server with a lower_case_table_names setting that is different from the setting used when the server was initialized.)
```
[mysqld]
lower_case_table_names=1
```
When running ALTER TABLE ... DISCARD PARTITION ... TABLESPACE and ALTER TABLE ... IMPORT PARTITION ... TABLESPACE on subpartitioned tables, both partition and subpartition table names are permitted. When a partition name is specified, subpartitions of that partition are included in the operation.

Internals

The following information describes internals and messages written to the error log during a table import procedure.

When ALTER TABLE ... DISCARD TABLESPACE is run on the destination instance:

The table is locked in X mode.
The tablespace is detached from the table.

When FLUSH TABLES ... FOR EXPORT is run on the source instance:

The table being flushed for export is locked in shared mode.
The purge coordinator thread is stopped.
Dirty pages are synchronized to disk.
Table metadata is written to the binary .cfg file.

Expected error log messages for this operation:

[Note] InnoDB: Sync to disk of '"test"."t1"' started.
[Note] InnoDB: Stopping purge
[Note] InnoDB: Writing table metadata to './test/t1.cfg'
[Note] InnoDB: Table '"test"."t1"' flushed to disk

When UNLOCK TABLES is run on the source instance:

The binary .cfg file is deleted.
The shared lock on the table or tables being imported is released and the purge coordinator thread is restarted.

Expected error log messages for this operation:

[Note] InnoDB: Deleting the meta-data file './test/t1.cfg'
[Note] InnoDB: Resuming purge

When ALTER TABLE ... IMPORT TABLESPACE is run on the destination instance, the import algorithm performs the following operations for each tablespace being imported:

Each tablespace page is checked for corruption.
The space ID and log sequence numbers (LSNs) on each page are updated.
Flags are validated and LSN updated for the header page.
Btree pages are updated.
The page state is set to dirty so that it is written to disk.

Expected error log messages for this operation:

[Note] InnoDB: Importing tablespace for table 'test/t1' that was exported
from host 'host_name'
[Note] InnoDB: Phase I - Update all pages
[Note] InnoDB: Sync to disk
[Note] InnoDB: Sync to disk - done!
[Note] InnoDB: Phase III - Flush changes to disk
[Note] InnoDB: Phase IV - Flush complete

~~Note~~注意

You may also receive a warning that a tablespace is discarded (if you discarded the tablespace for the destination table) and a message stating that statistics could not be calculated due to a missing .ibd file:

[Warning] InnoDB: Table "test"."t1" tablespace is set as discarded.
7f34d9a37700 InnoDB: cannot calculate statistics for table
"test"."t1" because the .ibd file is missing. For help, please refer to
http://dev.mysql.com/doc/refman/8.0/en/innodb-troubleshooting.html