Information about table definitions is stored both in the
.frm files, and in the InnoDB
data dictionary. If
.frm files around, or if the server
crashes in the middle of a data dictionary operation, these
sources of information can become inconsistent.
If a data dictionary corruption or consistency issue prevents you
Section 14.23.2, “Forcing InnoDB Recovery” for information about
A symptom of an out-of-sync data dictionary is that a
CREATE TABLE statement fails. If
this occurs, look in the server's error log. If the log says
that the table already exists inside the
InnoDB internal data dictionary, you have an
orphan table inside the
files that has no corresponding
The error message looks like this:
InnoDB: Error: table test/parent already exists in InnoDB internal InnoDB: data dictionary. Have you deleted the .frm file InnoDB: and not used DROP TABLE? Have you used DROP DATABASE InnoDB: for InnoDB tables in MySQL version <= 3.23.43? InnoDB: See the Restrictions section of the InnoDB manual. InnoDB: You can drop the orphaned table inside InnoDB by InnoDB: creating an InnoDB table with the same name in another InnoDB: database and moving the .frm file to the current database. InnoDB: Then MySQL thinks the table exists, and DROP TABLE will InnoDB: succeed.
You can drop the orphan table by following the instructions
given in the error message. If you are still unable to use
DROP TABLE successfully, the
problem may be due to name completion in the
mysql client. To work around this problem,
start the mysql client with the
option and try
DROP TABLE again.
(With name completion on, mysql tries to
construct a list of table names, which fails when a problem such
as just described exists.)
Another symptom of an out-of-sync data dictionary is that MySQL
prints an error that it cannot open an
ERROR 1016: Can't open file: 'child2.ibd'. (errno: 1)
In the error log you can find a message like this:
InnoDB: Cannot find table test/child2 from the internal data dictionary InnoDB: of InnoDB though the .frm file for the table exists. Maybe you InnoDB: have deleted and recreated InnoDB data files but have forgotten InnoDB: to delete the corresponding .frm files of InnoDB tables?
This means that there is an orphan
file without a corresponding table inside
InnoDB. You can drop the orphan
.frm file by deleting it manually.
If MySQL exits in the middle of an
TABLE operation, you may be left with an orphan
temporary table that takes up space on your system. This section
describes how to identify and remove orphan temporary tables.
Orphan temporary table names begin with an
#sql- prefix (e.g.,
#sql-540_3). The accompanying
.frm file has the same base name as the
orphan temporary table.
If there is no
.frm file, you can
recreate it. The
.frm file must have the
same table schema as the orphan temporary table (it must have
the same columns and indexes) and must be placed in the
database directory of the orphan temporary table.
To identify orphan temporary tables on your system, you can view
Table Monitor output.
Look for table names that begin with
If the original table resides in a
tablespace, the tablespace file (the
#sql-*.ibd file) for the orphan temporary
table should be visible in the database directory.
To remove an orphan temporary table, drop the table by issuing a
DROP TABLE statement, prefixing
the name of the table with
enclosing the table name in backticks. For example:
mysql> DROP TABLE `#mysql50##sql-540_3`;
#mysql50# prefix tells MySQL to ignore
file name safe encoding introduced in MySQL
5.1. Enclosing the table name in backticks is required to
perform SQL statements on table names with special characters
such as “#”.
enabled, the following message might occur if the
.ibd files (or
both) are missing:
InnoDB: in InnoDB data dictionary has tablespace id N, InnoDB: but tablespace with that id or name does not exist. Have InnoDB: you deleted or moved .ibd files? InnoDB: This may also be a table created with CREATE TEMPORARY TABLE InnoDB: whose .ibd and .frm files MySQL automatically removed, but the InnoDB: table still exists in the InnoDB internal data dictionary.
If this occurs, try the following procedure to resolve the problem:
Create a matching
.frmfile in some other database directory and copy it to the database directory where the orphan table is located.
DROP TABLEfor the original table. That should successfully drop the table and
InnoDBshould print a warning to the error log that the
.ibdfile was missing.