<p>MySQL cannot create or alter the partitioned table because the combined length of all partition key columns exceeds the 3072-byte limit.</p>
<p>MySQL Error 1660: ER_PARTITION_FIELDS_TOO_LONG occurs when the combined length of columns used in a PARTITION BY clause is greater than 3072 bytes. Reduce column sizes, switch to smaller data types, or remove large TEXT/BLOB columns from the partition key to resolve the issue.</p>
The total length of the partitioning fields is too large
This runtime or DDL error signals that the total byte length of columns listed in a PARTITION BY clause exceeds MySQLs internal 3072-byte ceiling. When the limit is surpassed, CREATE TABLE, ALTER TABLE, and EXPLAIN PARTITIONS statements fail.
MySQL counts storage bytes, not character count. UTF8MB4 or variable-length types inflate the size calculation, so wide VARCHAR, BLOB, or TEXT columns in the partition key trigger the error quickly.
The limit breach usually happens when developers include multiple large VARCHAR columns in a composite partition key, or when the character set uses up to four bytes per character. Using BLOB or TEXT is disallowed entirely and will also raise this error.
Migrating tables from Latin1 to UTF8MB4 can silently increase byte length, causing previously valid partitions to break on the next ALTER TABLE.
First, audit the partition key columns and calculate their combined maximum byte length. Reduce individual column lengths, cast to smaller data types, or remove non-essential columns from the PARTITION BY clause. After changes, re-run the DDL statement.
Alternatively, switch partitioning strategy to RANGE on an INT or DATE surrogate key, which rarely exceeds the byte threshold.
Wide VARCHAR composite keys: shrink VARCHAR(1024) to VARCHAR(255) or store a hash in BINARY(16). Error disappears once total bytes fall below 3072.
UTF8MB4 upgrade fallout: recalculate size at four bytes per char. If needed, keep table charset at UTF8 but store partition key in ASCII.
Always design partitions around small, immutable columns like INT, BIGINT, or DATE. Run SHOW CREATE TABLE to verify key length during development. Add automated checks in CI pipelines.
When using Galaxy, the schema-aware AI copilot flags oversize partition keys as you type, preventing the issue before execution.
Error 1503 (ER_PARTITION_FUNC_NOT_ALLOWED): arises when unsupported functions are used in partition clauses. Replace the function or switch to expression-based partitioning supported in MySQL 8.0+
Error 1500 (ER_PARTITION_WRONG_VALUES): indicates wrong VALUES LESS THAN syntax. Correct the upper bounds or data types and retry.
Including multiple wide VARCHAR columns (e.g., VARCHAR(1024)) in PARTITION BY KEY.
Using UTF8MB4 or UTF16 character sets that multiply byte length per character.
Attempting to partition on TEXT or BLOB columns, which MySQL prohibits.
Migrating charset or increasing column size without revisiting partition design.
Raised when unsupported functions are used in partition expressions. Replace with permitted functions or upgrade MySQL.
Occurs when RANGE partition bounds are misdeclared. Ensure VALUES LESS THAN lists ascending non-overlapping limits.
Happens if column list does not match partition functions requirement. Align column order and types.
No. TEXT and BLOB types are not allowed in partition keys and will trigger Error 1660 or 1503.
MySQL stores up to 1024 three-byte integers internally for partition keys, resulting in a 3072-byte cap.
Yes. UTF8MB4 lines can quadruple byte usage compared to ASCII, pushing you past the limit.
Galaxys AI copilot inspects schema context and warns when your partition key design nears the 3072-byte threshold.
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