EC
2034
MySQLERRORCriticalLockingMEDIUM confidence

INSERT DELAYED cannot change lock

Production Risk

Low — insert is rejected; data is not written.

What this means

The INSERT DELAYED handler thread could not acquire or change the table lock needed to process delayed inserts. This is specific to the DELAYED INSERT mechanism which was deprecated and removed in MySQL 5.7.

Why it happens
  1. 1Conflicting DDL or table lock preventing the delayed insert handler from running.
  2. 2Table locked by another session during delayed insert processing.
How to reproduce
trigger — this will error
trigger — this will error
INSERT DELAYED INTO t VALUES (1); -- MySQL 5.x

expected output

ERROR 2034 (HY000): INSERT DELAYED can't be used with table that has been locked with LOCK TABLES.

Fix 1

Release table locks before using INSERT DELAYED

Release table locks before using INSERT DELAYED
UNLOCK TABLES;
INSERT DELAYED INTO t VALUES (1);

Why this works

The delayed handler needs to acquire its own lock.

Fix 2

Migrate to regular INSERT or INSERT LOW_PRIORITY (MySQL 5.7+)

Migrate to regular INSERT or INSERT LOW_PRIORITY (MySQL 5.7+)
INSERT LOW_PRIORITY INTO t VALUES (1);

Why this works

INSERT DELAYED is removed in MySQL 5.7; use LOW_PRIORITY or async application-level inserts.

What not to do

✕

Version notes

Sources
Official documentation ↗

MySQL 5.6 — 2034 ER_DELAYED_CANT_CHANGE_LOCK

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