MySQL Error 1510: ER_REORG_HASH_ONLY_ON_SAME_NO - How to Fix and Prevent

August 7, 2025

<p>MySQL raises error 1510 when a REORGANIZE PARTITION statement tries to change the number of HASH partitions instead of simply redistributing existing partitions.</p>

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What is MySQL error code 1510 - ER_REORG_HASH_ONLY_ON_SAME_NO?

<p>MySQL Error 1510: ER_REORG_HASH_ONLY_ON_SAME_NO means REORGANIZE PARTITION attempted to change the number of HASH partitions. Keep the partition count unchanged or use ALTER TABLE ... PARTITION BY HASH to fix the issue.</p>

Error Highlights

Typical Error Message

REORGANIZE PARTITION can only be used to reorganize

Error Type

Partition Management Error

Language

MySQL

Symbol

ER_REORG_HASH_ONLY_ON_SAME_NO

Error Code

1510

SQL State

HY000

Explanation

Example H2

Example H3

What is MySQL error 1510 ER_REORG_HASH_ONLY_ON_SAME_NO?

Error 1510 appears when you run REORGANIZE PARTITION on a HASH partitioned table and the resulting partition list does not match the original partition count.

MySQL allows REORGANIZE PARTITION only to reshuffle existing partitions, not to add or remove partitions. If the partition count differs, the server aborts the statement with SQLSTATE HY000 and this error.

When does this error occur?

The error surfaces during ALTER TABLE ... REORGANIZE PARTITION commands on tables created with PARTITION BY HASH or LINEAR HASH.

It affects all supported MySQL versions that implement partitioning, including MySQL 5.7, 8.0, and compatible MariaDB releases.

Why is fixing it important?

Unresolved, the table structure stays unchanged, blocking maintenance tasks like data rebalancing or archive partition separation. Proper partition management maintains query performance and storage efficiency.

Common Causes

Incorrect target partition list

Specifying more or fewer partitions than the current HASH partition count triggers the error.

Mixing partitioning methods

Attempting to convert from HASH to RANGE or LIST using REORGANIZE leads to the same failure.

Misreading documentation

Developers sometimes expect REORGANIZE PARTITION to work like ADD PARTITION and DROP PARTITION combined.

Related Errors

MySQL Error 1505 partition_exists

Raised when a partition with the same name already exists.

MySQL Error 1514 partition_wrong_no

Appears when ADD PARTITION tries to create fewer partitions than required by the current partitioning function.

MySQL Error 1493 err_partition_wrong_values

Occurs when partition boundary values are invalid for RANGE or LIST partitions.

FAQs

Can I increase HASH partitions without dropping data?

Yes. Use ALTER TABLE ... PARTITION BY HASH with a higher PARTITIONS value; MySQL will redistribute rows automatically.

Is REORGANIZE PARTITION ever useful for HASH partitions?

It is mainly used to rename or merge partitions while keeping the total count unchanged.

Does this error affect RANGE partitions?

No. RANGE partitions allow changing the number of partitions with REORGANIZE as long as boundaries remain valid.

How does Galaxy help avoid partition errors?

Galaxy's schema-aware autocomplete and AI validation highlight invalid REORGANIZE statements before execution, saving time and preventing downtime.

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