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MySQL 5.6 Reference Manual  /  ...  /  SQL Compression Syntax Warnings and Errors

14.9.7 SQL Compression Syntax Warnings and Errors

Specifying ROW_FORMAT=COMPRESSED or KEY_BLOCK_SIZE in CREATE TABLE or ALTER TABLE statements produces the following warnings if the Barracuda file format is not enabled. You can view them with the SHOW WARNINGS statement.

Level Code Message
Warning 1478 InnoDB: KEY_BLOCK_SIZE requires innodb_file_per_table.
Warning 1478 InnoDB: KEY_BLOCK_SIZE requires innodb_file_format=1
Warning 1478 InnoDB: ignoring KEY_BLOCK_SIZE=4.
Warning 1478 InnoDB: ROW_FORMAT=COMPRESSED requires innodb_file_per_table.
Warning 1478 InnoDB: assuming ROW_FORMAT=COMPACT.


  • By default, these messages are only warnings, not errors, and the table is created without compression, as if the options were not specified.

  • When innodb_strict_mode is enabled, MySQL generates an error, not a warning, for these cases. The table is not created if the current configuration does not permit using compressed tables.

The non-strict behavior lets you import a mysqldump file into a database that does not support compressed tables, even if the source database contained compressed tables. In that case, MySQL creates the table in ROW_FORMAT=COMPACT instead of preventing the operation.

To import the dump file into a new database, and have the tables re-created as they exist in the original database, ensure the server has the proper settings for the configuration parameters innodb_file_format and innodb_file_per_table.

The attribute KEY_BLOCK_SIZE is permitted only when ROW_FORMAT is specified as COMPRESSED or is omitted. Specifying a KEY_BLOCK_SIZE with any other ROW_FORMAT generates a warning that you can view with SHOW WARNINGS. However, the table is non-compressed; the specified KEY_BLOCK_SIZE is ignored).

Level Code Message
Warning 1478 InnoDB: ignoring KEY_BLOCK_SIZE=n unless ROW_FORMAT=COMPRESSED.

If you are running with innodb_strict_mode enabled, the combination of a KEY_BLOCK_SIZE with any ROW_FORMAT other than COMPRESSED generates an error, not a warning, and the table is not created.

Table 14.5, “ROW_FORMAT and KEY_BLOCK_SIZE Options” provides an overview the ROW_FORMAT and KEY_BLOCK_SIZE options that are used with CREATE TABLE or ALTER TABLE.

Table 14.5 ROW_FORMAT and KEY_BLOCK_SIZE Options

Option Usage Notes Description
ROW_FORMAT=​REDUNDANT Storage format used prior to MySQL 5.0.3 Less efficient than ROW_FORMAT=COMPACT; for backward compatibility
ROW_FORMAT=​COMPACT Default storage format since MySQL 5.0.3 Stores a prefix of 768 bytes of long column values in the clustered index page, with the remaining bytes stored in an overflow page
ROW_FORMAT=​DYNAMIC Available only with innodb_file​_format=Barracuda Store values within the clustered index page if they fit; if not, stores only a 20-byte pointer to an overflow page (no prefix)
ROW_FORMAT=​COMPRESSED Available only with innodb_file​_format=Barracuda Compresses the table and indexes using zlib
KEY_BLOCK_​SIZE=n Available only with innodb_file​_format=Barracuda Specifies compressed page size of 1, 2, 4, 8 or 16 kilobytes; implies ROW_FORMAT=COMPRESSED

Table 14.6, “CREATE/ALTER TABLE Warnings and Errors when InnoDB Strict Mode is OFF” summarizes error conditions that occur with certain combinations of configuration parameters and options on the CREATE TABLE or ALTER TABLE statements, and how the options appear in the output of SHOW TABLE STATUS.

When innodb_strict_mode is OFF, MySQL creates or alters the table, but ignores certain settings as shown below. You can see the warning messages in the MySQL error log. When innodb_strict_mode is ON, these specified combinations of options generate errors, and the table is not created or altered. To see the full description of the error condition, issue the SHOW ERRORS statement: example:



ERROR 1005 (HY000): Can't create table 'test.x' (errno: 1478)

| Level | Code | Message                                   |
| Error | 1478 | InnoDB: invalid KEY_BLOCK_SIZE=33333.     |
| Error | 1005 | Can't create table 'test.x' (errno: 1478) |

Table 14.6 CREATE/ALTER TABLE Warnings and Errors when InnoDB Strict Mode is OFF

Syntax Warning or Error Condition Resulting ROW_FORMAT, as shown in SHOW TABLE STATUS
ROW_FORMAT=COMPRESSED or ROW_FORMAT=DYNAMIC or KEY_BLOCK_SIZE is specified Ignored unless both innodb_file_format=Barracuda and innodb_file_per_table are enabled COMPACT
Invalid KEY_BLOCK_SIZE is specified (not 1, 2, 4, 8 or 16) KEY_BLOCK_SIZE is ignored the requested row format, or COMPACT by default
ROW_FORMAT=COMPRESSED and valid KEY_BLOCK_SIZE are specified None; KEY_BLOCK_SIZE specified is used COMPRESSED
ROW_FORMAT is not one of REDUNDANT, COMPACT, DYNAMIC or COMPRESSED Ignored if recognized by the MySQL parser. Otherwise, an error is issued. COMPACT or N/A

When innodb_strict_mode is ON, MySQL rejects invalid ROW_FORMAT or KEY_BLOCK_SIZE parameters. For compatibility with earlier versions of MySQL, strict mode is not enabled by default; instead, MySQL issues warnings (not errors) for ignored invalid parameters.

It is not possible to see the chosen KEY_BLOCK_SIZE using SHOW TABLE STATUS. The statement SHOW CREATE TABLE displays the KEY_BLOCK_SIZE (even if it was ignored when creating the table). The real compressed page size of the table cannot be displayed by MySQL.