<p>MySQL cannot change a column's data type using an INPLACE algorithm during ALTER TABLE when this error appears.</p>
<p>MySQL Error 1850: ER_ALTER_OPERATION_NOT_SUPPORTED_REASON_COLUMN_TYPE occurs when ALTER TABLE tries to modify a column data type with ALGORITHM=INPLACE. Switch to ALGORITHM=COPY or drop conflicting features to resolve the issue.</p>
Cannot change column type INPLACE
The server raises MySQL Error 1850 with message ER_ALTER_OPERATION_NOT_SUPPORTED_REASON_COLUMN_TYPE when an ALTER TABLE statement attempts to change a column's data type using the INPLACE algorithm. The storage engine cannot perform the operation online, so it blocks the request.
The error appears from MySQL 5.7.1 onward and is common in production environments that default to ALGORITHM=INPLACE for zero-downtime schema changes.
The INPLACE algorithm is limited to metadata-only or light changes. Converting a column from INT to BIGINT, or CHAR to VARCHAR, alters physical row storage and therefore requires table copy or rebuild. MySQL refuses the request and throws error 1850.
The error also fires if a secondary index, foreign key, or partitioning setting prevents an online change to the column definition.
Leaving the schema unchanged blocks feature delivery and may cause application failures that rely on the new data type. Addressing the error ensures smooth deployments and protects data consistency.
Galaxy's AI copilot flags ALTER TABLE statements likely to trigger Error 1850 and suggests the correct algorithm or a safer migration plan, reducing downtime and manual debugging.
Conversions that rewrite every row (INT to BIGINT, TEXT to MEDIUMTEXT) cannot run INPLACE.
These index types block online column type changes.
Referenced columns force a table copy when their data type changes.
Occurs when renaming a column referenced by a foreign key with ALGORITHM=INPLACE.
Raised if partitioned tables block certain online alterations.
Triggered when altering an AUTO_INCREMENT column in place.
No. The ALTER TABLE fails and leaves the schema unchanged.
Yes, COPY copies the entire table and holds metadata locks, but ensures the change completes.
Yes. InnoDB has specific limitations, while other engines may behave differently.
Galaxy highlights the failed statement, shows the exact error text, and offers AI-powered fixes.
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