MySQL throws Error 1150 when the delayed insert thread cannot obtain a write lock on the target table, usually due to long-running reads or explicit LOCK TABLES statements.
MySQL Error 1150 (ER_UNUSED1) appears when the delayed insert thread cannot secure the table lock it needs for buffering writes. Free the lock by ending long reads, removing explicit LOCK TABLES, or converting to non-DELAYED inserts to resolve the issue quickly in the US region.
Delayed insert thread couldn't get requested lock for
MySQL returns error code 1150 with message “Delayed insert thread couldn't get requested lock for table %s” when the server’s delayed insert handler fails to lock the destination MyISAM table.
The delayed insert thread buffers rows in memory and flushes them asynchronously. It must obtain a WRITE lock on the table.
If another client holds a conflicting READ or WRITE lock for too long, the thread gives up and surfaces Error 1150.
Prolonged SELECT queries on the same MyISAM table hold a READ lock that blocks the delayed insert thread’s WRITE lock, eventually triggering the error.
Explicit LOCK TABLES tbl READ; or LOCK TABLES tbl WRITE; statements prevent the delayed insert thread from progressing and raise the error once the wait timeout expires.
Low delayed_insert_timeout or delayed_queue_size settings shorten the grace period or buffer space, increasing the likelihood of Error 1150 under moderate workloads.
Terminate or optimize the blocking SELECT sessions so the delayed insert thread can acquire its lock.
Remove or shorten explicit table locks in application code, or switch to transaction-safe row-level locking storage engines like InnoDB where DELAYED is ignored.
Increase delayed_insert_timeout and delayed_queue_size to give the thread more time and memory to obtain the lock.
Heavy reporting queries during peak ingest cause lock contention.
Offload reporting to replicas or use InnoDB to eliminate the issue.
Maintenance scripts using LOCK TABLES conflict with DELAYED inserts.
Rewrite scripts to use transactions instead of global table locks.
Avoid DELAYED inserts in new code; they are deprecated and ignored by modern MySQL for InnoDB tables.
Migrate MyISAM tables to InnoDB to benefit from row-level locking and eliminate delayed insert threads entirely.
Monitor SHOW PROCESSLIST and performance_schema for long-running reads that starve writers.
Error 1205 (Lock wait timeout exceeded) indicates row lock contention in InnoDB rather than table locks in MyISAM.
Error 1025 (Error on rename of…) can follow failed delayed inserts if table alterations collide with pending locks.
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No rows are lost; they remain queued in memory. Once the lock is free, inserts resume or you can reissue them manually.
No. MySQL silently ignores the DELAYED keyword for InnoDB tables, preventing Error 1150.
Galaxy highlights long-running queries and suggests converting MyISAM tables to InnoDB via its AI copilot, reducing lock contention.
Yes. MySQL 8.0 marks DELAYED inserts as deprecated and advises immediate inserts or row-level storage engines instead.
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