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Description

Error 3759 occurs when attempting to create a FULLTEXT index on a functional expression or a computed column in MySQL. This indicates that MySQL's native FULLTEXT indexing mechanism currently only supports direct indexing of base table columns, not the results of functions or expressions.

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Error Message

Fulltext functional index is not supported.

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Known Causes

3 known causes

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Attempting to Index an Expression

You are trying to create a FULLTEXT index directly on an expression or a function's result (e.g., FULLTEXT(LOWER(column_name))) in your CREATE TABLE or ALTER TABLE statement.

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Indexing a Virtual Generated Column

The FULLTEXT index is being applied to a virtual generated column whose definition itself involves a functional expression, which MySQL does not support for full-text indexing.

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Misunderstanding FULLTEXT Limitations

Lack of awareness that MySQL's native FULLTEXT indexes are designed for direct indexing of physical columns and do not support derived or computed values.

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Solutions

3 solutions available

1. Migrate to a Supported Full-Text Index Type medium

Recreate your index using standard FULLTEXT index syntax, which is widely supported.

1

Identify the table and columns involved in the unsupported functional index. The error message or your schema definition will provide this information.

2

Drop the existing unsupported index.

DROP INDEX index_name ON table_name;

3

Create a standard FULLTEXT index on the desired columns. Note that functional indexes often involve expressions; you'll need to apply the same logic to the indexed columns directly if possible, or consider pre-processing data.

ALTER TABLE table_name ADD FULLTEXT(column1, column2, ...);

4

If your functional index relied on a specific expression, you might need to add a generated column to your table that holds the result of that expression and then index that generated column. For example, if your functional index was on `LOWER(column_name)`:

ALTER TABLE table_name ADD COLUMN indexed_column VARCHAR(255) GENERATED ALWAYS AS (LOWER(column_name)) STORED;
ALTER TABLE table_name ADD FULLTEXT(indexed_column);

5

Test your full-text search queries to ensure they function correctly with the new index.

2. Upgrade MySQL Version medium

Update to a MySQL version that supports functional indexes for FULLTEXT. Check release notes for specific support.

1

Determine your current MySQL version using `SELECT VERSION();`.

SELECT VERSION();

2

Consult the official MySQL documentation or release notes for your current and potential upgrade versions to confirm support for functional indexes on FULLTEXT indexes. Support for functional indexes has been introduced and improved in later versions of MySQL (e.g., MySQL 8.0+).

3

Plan and execute a MySQL upgrade. This typically involves backing up your database, stopping the MySQL server, installing the new version, and running the `mysql_upgrade` utility.

sudo systemctl stop mysql
# Follow upgrade procedures for your OS and MySQL version
sudo mysql_upgrade -u root -p

4

After upgrading, attempt to create your functional index again. The syntax for creating it might be similar to what you tried initially, but now it should be supported.

ALTER TABLE table_name ADD FULLTEXT INDEX index_name (expression);

3. Pre-process and Index Raw Data medium

Modify your application logic to store processed data in a separate column and index that column.

1

Analyze the expression used in your functional index. For example, if it's `LOWER(column_name)` or `REPLACE(column_name, ' ', '')`.

2

Add a new column to your table that will store the pre-processed data. Choose an appropriate data type.

ALTER TABLE table_name ADD COLUMN processed_column VARCHAR(255);

3

Update your application's INSERT and UPDATE statements to populate this new `processed_column` with the result of the function applied to your original data. Alternatively, you can use a trigger or a scheduled job.

-- Example INSERT statement in your application:
INSERT INTO table_name (original_column, processed_column) VALUES ('Some Value', LOWER('Some Value'));

4

Create a standard FULLTEXT index on the new `processed_column`.

ALTER TABLE table_name ADD FULLTEXT(processed_column);

5

Modify your full-text search queries to search against the `processed_column` instead of using the functional index expression directly.

SELECT * FROM table_name WHERE MATCH(processed_column) AGAINST ('search term');

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Related Errors

5 related errors

MySQL Error 3759: Fulltext Functional Index Not Supported