3126
MariaDBERRORNotableDDLHIGH confidence
ALTER TABLE IGNORE not supported with INPLACE algorithm
Production Risk
High — IGNORE silently deletes data; always take a backup first.
What this means
ALTER TABLE ... IGNORE was requested with ALGORITHM=INPLACE, but the IGNORE clause requires a table copy to silently discard duplicate or constraint-violating rows.
Why it happens
- 1Using ALTER TABLE IGNORE with ALGORITHM=INPLACE.
How to reproduce
trigger — this will error
trigger — this will error
ALTER IGNORE TABLE t1 ADD UNIQUE KEY (col), ALGORITHM=INPLACE;
expected output
ERROR 3126 (HY000): ALGORITHM=INPLACE is not supported. Reason: IGNORE requires table copy.
Fix
Use ALGORITHM=COPY with IGNORE
Use ALGORITHM=COPY with IGNORE
ALTER IGNORE TABLE t1 ADD UNIQUE KEY (col), ALGORITHM=COPY;
Why this works
Allows duplicate rows to be silently discarded during the rebuild.
What not to do
✕
Sources
Official documentation ↗
MySQL 8.0 — 3126 ER_ALTER_OPERATION_NOT_SUPPORTED_REASON_IGNORE2
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