<p>MySQL reports that a system table has an unexpected number of columns, indicating corruption or an incomplete upgrade.</p>
<p>MySQL error 1547 ER_OBSOLETE_COL_COUNT_DOESNT_MATCH_CORRUPTED means the column count in a mysql.* system table differs from what the server expects, signaling table corruption. Run mysql_upgrade or rebuild the mysql schema to restore matching structures.</p>
Column count of mysql.%s is wrong. Expected %d, found %d.
MySQL error 1547 with condition name ER_OBSOLETE_COL_COUNT_DOESNT_MATCH_CORRUPTED appears when the server reads a system table inside the mysql schema and finds a different number of columns than it expects. The mismatch tells MySQL that the table definition is inconsistent with the version that the running server was compiled for.
The warning usually pops up during startup, mysql_upgrade, or any statement that touches privilege or help tables because these tables live in the mysql system database. Fixing it quickly is critical because corrupted or outdated system tables can break authentication, permissions, or upgrades.
The error surfaces when the on-disk .frm definition of a system table no longer matches the compiled-in definition that the server expects. This situation can be caused by skipped upgrades, partial restores, or disk corruption.
When column definitions are truncated or extended unexpectedly, MySQL reads past the allocated structure and raises error 1547 instead of crashing. The condition name ends with CORRUPTED to highlight the risk of further data loss.
The safest fix is to run the mysql_upgrade utility that ships with the same MySQL version as the server. mysql_upgrade reconnects to the running instance, recreates each mysql.* table with the expected structure, and repopulates data.
If mysql_upgrade fails or the server cannot start, manually rebuild the mysql system database from a clean install of the same major version. Copy the freshly generated .frm and .ibd files or run mysql_install_db or mysqld --initialize-insecure.
After an OS package upgrade you start an older mysqld binary. Start the correct new binary or reinstall matching packages to align structures.
You restored a logical dump that excluded ALTER statements on mysql.* tables. Re-run mysql_upgrade to complete the structural changes.
A sudden power loss corrupted the ibdata or redo logs. Restore from the most recent backup, then run mysqlcheck --repair on affected non-system databases.
Always execute mysql_upgrade immediately after every minor or major version upgrade before bringing applications back online.
Keep validated backups of the mysql schema and test restores in staging to ensure structural integrity.
Use tool-driven schema management like Galaxy Collections to version control DDL so unintended manual changes to system tables are caught during code review.
Error 1548 ER_OBSOLETE_COL_COUNT_DOESNT_MATCH_PLEASE_UPDATE indicates a mismatch but suggests running mysql_upgrade rather than corruption. Fix it with the same process.
Error 1558 ER_BAD_DB_ERROR signals that a required database is missing, often following system table corruption. Recreate missing databases or restore backups.
Launching an older mysqld against a data directory that was already upgraded causes column definitions to disagree with compiled-in expectations.
If mysql_upgrade was interrupted the privilege tables may be half-altered, leaving mismatched column counts.
Directly altering tables in the mysql schema can introduce or remove columns, breaking internal metadata.
Bit rot or unsafe shutdowns can corrupt .frm or .ibd files, leading MySQL to misread the stored column count.
Restoring dumps or physical files from a different MySQL version can leave outdated structures in place.
Mismatch detected but not marked corrupted. Run mysql_upgrade.
Collation mismatches in system tables can appear after upgrades. Rebuild affected tables.
MySQL cannot open a table file, possibly due to corruption or missing files.
Ignoring it is risky. System tables govern authentication and privileges. Corruption can escalate and cause outages. Fix immediately.
mysqlcheck can repair user tables but cannot change system table structures. Use mysql_upgrade or rebuild the mysql schema.
The utility only touches tables in the mysql system database, leaving user databases untouched. It is safe when run on a backup first.
Galaxy versions and validates every DDL statement, preventing accidental changes to the mysql schema and flagging mismatches during code review.
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