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Description

This error occurs when you attempt to create or alter a table in MySQL that defines more partitions and subpartitions than the system's maximum allowed limit. It typically arises during table creation or ALTER TABLE operations when dealing with very large datasets requiring extensive partitioning schemes.

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Error Message

Too many partitions (including subpartitions) were defined

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Known Causes

4 known causes

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Exceeding MySQL Partition Limit

MySQL imposes a maximum limit (e.g., 8192 in some versions) on the total number of partitions and subpartitions for a single table. Attempting to define more than this limit will trigger error 1499.

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Overly Granular Partitioning

Designing a partitioning strategy that uses too many small partitions or subpartitions without a clear performance benefit can quickly hit the system limit, especially when partitioning by many columns or small ranges.

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Automated Partition Script Error

Scripts or ORM tools that automatically generate partitioning clauses might inadvertently create a table definition with more partitions than allowed if not configured to respect MySQL's limits.

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Misconfigured Partitioning Strategy

Users might define an excessive number of partitions based on a misunderstanding of how partitioning works or its practical limits, leading to an overly complex and invalid table definition.

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Solutions

3 solutions available

1. Reduce the Number of Partitions medium

Re-evaluate your partitioning strategy to use fewer, broader partitions.

1

Analyze your current partitioning scheme. Identify if the granularity of your partitions is unnecessarily high. For example, partitioning by day might be excessive if you only need to query monthly or yearly data.

2

Determine a new partitioning strategy that aggregates data into fewer, larger partitions. This might involve changing the partitioning key or the range/list of values for each partition.

3

If possible, create a new table with the desired partitioning scheme and migrate your data. This is often the safest approach for existing, large tables.

CREATE TABLE new_table LIKE original_table;
ALTER TABLE new_table PARTITION BY HASH(column_name) PARTITIONS 16; -- Example: HASH partitioning with 16 partitions
INSERT INTO new_table SELECT * FROM original_table;
RENAME TABLE original_table TO old_table, new_table TO original_table;
DROP TABLE old_table;

4

Alternatively, if the table is not too large or downtime is acceptable, you can drop and recreate the table with the correct partitioning.

DROP TABLE your_table_name;
CREATE TABLE your_table_name (
  -- your columns and constraints
) ENGINE=InnoDB
PARTITION BY RANGE(column_name) (
  PARTITION p0 VALUES LESS THAN (100),
  PARTITION p1 VALUES LESS THAN (200),
  PARTITION p2 VALUES LESS THAN MAXVALUE -- Example: 3 partitions
);

2. Increase the Maximum Number of Partitions (with caution) medium

Temporarily increase the system limit for partitions if absolutely necessary and you understand the implications.

1

Check the current maximum number of partitions allowed by your MySQL version. This is controlled by the `max_heap_table_size` and `tmp_table_size` system variables, and more directly by the `table_definition_cache` and `table_open_cache` variables. The effective limit can also be influenced by operating system limits.

SHOW VARIABLES LIKE 'table_definition_cache';
SHOW VARIABLES LIKE 'table_open_cache';

2

Increase the `table_definition_cache` and `table_open_cache` values in your `my.cnf` (or `my.ini`) configuration file. The maximum number of partitions is often tied to these values. A common recommendation is to set them to a value significantly larger than the expected number of partitions, e.g., 2048 or higher.

[mysqld]
table_definition_cache = 2048
table_open_cache = 2048

3

Restart your MySQL server for the changes to take effect.

sudo systemctl restart mysql # or mysqld

4

Be aware that increasing these values can consume more memory. Monitor your server's memory usage closely after making this change. This is generally a temporary workaround and not a long-term solution if your partitioning strategy is fundamentally flawed.

3. Consolidate Partitions advanced

Merge existing partitions to reduce the total count.

1

This is a complex operation that usually involves creating a new table with consolidated partitions, migrating data, and then replacing the original table. It's similar to the first solution but focuses on modifying an existing table's partitioning structure by recreating it.

2

Create a new table with your desired, consolidated partitioning scheme.

CREATE TABLE new_table (
  -- your columns and constraints
) ENGINE=InnoDB
PARTITION BY RANGE(column_name) (
  PARTITION p0 VALUES LESS THAN (1000),
  PARTITION p1 VALUES LESS THAN (2000),
  PARTITION p2 VALUES LESS THAN MAXVALUE
);

3

Migrate the data from the original table to the new table. This might require careful handling of partition boundaries to ensure data integrity. You might need to insert data in batches or use specific `INSERT ... SELECT` statements.

INSERT INTO new_table SELECT * FROM original_table WHERE column_name < 1000;
INSERT INTO new_table SELECT * FROM original_table WHERE column_name >= 1000 AND column_name < 2000;
INSERT INTO new_table SELECT * FROM original_table WHERE column_name >= 2000;

4

Once data migration is complete and verified, swap the tables.

RENAME TABLE original_table TO old_table, new_table TO original_table;
DROP TABLE old_table;

5

This process can be time-consuming and requires careful planning and testing to avoid data loss or corruption.

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Related Errors

5 related errors

MySQL Error 1499: Too Many Table Partitions