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Category: MySQL Data Recovery

Resolving ERROR 1050 42S01 At Line 1 Table Already Exists

When ALTER TABLE crashes the MySQL server, it leaves orphaned records in the InnoDB dictionary. It is annoying because next time you run the same ALTER TABLE query, it will fail with error:

This post explains why it happens and how to fix it. When you run ALTER table, InnoDB follows the plan: Block […]

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Recover Table Structure From InnoDB Dictionary

When a table gets dropped, MySQL removes the respective .frm file. This post explains how to recover the table structure if the table was dropped. You need the table structure to recover a dropped table from the InnoDB tablespace. The B+tree structure of the InnoDB index doesn’t contain any information about field types. MySQL needs […]

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Recovering A Corrupt MySQL Database

UPDATE: We announced online data recovery from corrupt databases. Check it out on https://recovery.twindb.com/ The unDROP for InnoDB tool can be used to recover corrupt MySQL databases. In this post, we will show how to repair a MySQL database if its files got corrupted and even innodb_force_recovery=6 doesn’t help. The corruption of InnoDB tablespace may […]

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Repair Corrupted InnoDB Tables With Secondary Index Corruption

UPDATE: We announced online data recovery from corrupt databases. Check it out on https://recovery.twindb.com/ UPDATE (01/01/2017): We stopped further development of undrop-for-innodb and don’t support its open source versions anymore. InnoDB provides no means to repair corrupted table space. Once a table got corrupted, the only way to repair MySQL files is to start it […]

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Recovery After DROP TABLE, With Innodb_file_per_table ON

UPDATE (01/01/2017): We stopped further development of undrop-for-innodb and don’t support its open source versions anymore. Introduction In the previous post, we described a situation when the TwinDB recovery toolkit can be used to recover an accidentally dropped table with innodb_file_per_table=OFF. In this post, we’ll show how to recover MySQL tables or databases if innodb_file_per_table is ON. So, […]

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Recovery After DROP TABLE, With Innodb_file_per_table OFF

UPDATE (01/01/2017): We stopped further development of undrop-for-innodb and don’t support its open source versions anymore. Introduction Unfortunately, human mistakes are inevitable. That’s how life is. Wrong “DROP DATABASE” or “DROP TABLE” may destroy critical data on the MySQL server. Obviously, backups would help, however they’re not always available. This situation is frightening but not […]

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