<p>MySQL throws ER_INNODB_INDEX_CORRUPT (Index corrupt) when the InnoDB storage engine detects structural damage inside an index tree.</p>
<p>MySQL Error 1817 ER_INNODB_INDEX_CORRUPT signals that an InnoDB index tree is damaged, blocking reads and writes. Run CHECK TABLE, rebuild or drop and recreate the affected index, and restore from a healthy backup to resolve the corruption.</p>
Index corrupt: %s
The error appears as Index corrupt: %s and means the InnoDB storage engine found an internal inconsistency in an index page or the B tree structure.
MySQL refuses to access the corrupted index to protect data integrity, so queries that reference it fail immediately.
The error surfaces during query execution, ALTER TABLE, or background purge when InnoDB reads a damaged index page from disk.
It can also appear after an unexpected shutdown, disk failure, or a bug in earlier MySQL versions that wrote bad pages.
Corrupted indexes can hide or duplicate rows, causing wrong query results. Ignoring the error risks further corruption and total table loss.
Hardware issues like sudden power loss or bad sectors frequently corrupt index pages.
File system or RAID controller bugs, out-of-space conditions, and MySQL crashes during heavy writes can also damage indexes.
Using experimental features or outdated MySQL versions with known InnoDB bugs increases risk.
First isolate the table, stop writes, and create a physical backup of the .ibd file.
Run CHECK TABLE tbl_name FOR UPGRADE; If corruption is confirmed, rebuild the index with ALTER TABLE tbl_name FORCE; or DROP and ADD the index.
If rebuild fails, dump the table with --skip-add-locks --single-transaction and reload into a new table.
Single-index corruption: rebuild the specific secondary index.
Clustered primary key corruption: use mysqldump and reload from backup because the table cannot be scanned safely.
Use reliable hardware with battery-backed write cache, enable InnoDB doublewrite, and keep MySQL upgraded.
Schedule regular CHECK TABLE runs and automatic backups to catch corruption early.
ER_INNODB_CORRUPT_INDEX_ON_IDLE_DROP signals corruption detected during index drop.
ER_INNODB_PAGE_CORRUPT indicates damage in any InnoDB page, not just indexes.
Sudden shutdown while InnoDB flushes dirty index pages can leave half-written pages on disk.
Failing SSD or HDD sectors overwrite index bytes, breaking page checksums.
Older releases before 5.7.28 had known InnoDB page-compression defects that produced corrupt indexes.
Out-of-space or journal failures in ext4/xfs can truncate index pages.
General page corruption detected anywhere in an InnoDB file, not limited to indexes.
Index corruption found while InnoDB attempted to drop an index during idle purge.
Occurs when InnoDB cannot locate the .ibd file, sometimes following disk errors similar to index corruption.
No. The corruption may silently spread and cause data loss. Fix or restore immediately.
REPAIR TABLE only works for MyISAM. Use ALTER TABLE ... FORCE or logical dump and reload for InnoDB.
OPTIMIZE TABLE rebuilds the table, so it removes corruption in most cases, similar to ALTER TABLE ... FORCE.
Galaxy tracks schema changes, encourages versioned queries, and surfaces long-running writes, helping teams catch risky operations that often precede corruption.
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