mySQL MATCH across multiple tables

Question

I have a set of 4 tables that I want to search across. Each has a full text index. Can a query make use of every index?

CREATE TABLE `categories` (
  `id` in         


        

Answer 1

• You can't define fulltext indexes (or any kind of index) across multiple tables in MySQL. Each index definition references exactly one table. All columns in a given fulltext index must be from the same table.

• The columns named as arguments to the MATCH() function must be part of a single fulltext index. You can't use a single call to MATCH() to search all columns that are part of all fulltext indexes in your database.

• Fulltext indexes only index columns defined with CHAR, VARCHAR, and TEXT datatypes.

• You can define a fulltext index in each table.

Example:

CREATE TABLE categories (
  id SERIAL PRIMARY KEY,
  name VARCHAR(100),
  FULLTEXT INDEX ftcat (name)
);

CREATE TABLE host_types (
  id SERIAL PRIMARY KEY,
  category_id BIGINT UNSIGNED,
  name VARCHAR(100),
  FULLTEXT INDEX ftht (name)
);

CREATE TABLE hosts (
  id SERIAL PRIMARY KEY,
  host_id BIGINT UNSIGNED,
  category_id BIGINT UNSIGNED,
  name VARCHAR(100),
  FULLTEXT INDEX fthost (name)
);

CREATE TABLE products (
  id SERIAL PRIMARY KEY,
  name VARCHAR(100),
  keywords VARCHAR(100),
  uid VARCHAR(100),
  description VARCHAR(100),
  quantity INTEGER,
  price NUMERIC(9,2),
  host_id BIGINT UNSIGNED,
  FULLTEXT INDEX ftprod (name, keywords, description, uid)
);

And then you can write a query that uses each respective fulltext index:

SELECT ...
  MATCH(categories.name) AGAINST('search term') as cscore, 
  MATCH(host_types.name) AGAINST('search term') as htscore,
  MATCH(hosts.name) AGAINST('search term') as hscore,
  MATCH(products.name, products.keywords, products.description, products.uid)
    AGAINST('search term') as score
FROM products
LEFT JOIN hosts ON products.host_id = hosts.id
LEFT JOIN host_types ON hosts.host_id = host_types.id
LEFT JOIN categories ON host_types.category_id = categories.id
WHERE
  MATCH(categories.name) AGAINST('search term') OR
  MATCH(host_types.name) AGAINST('search term') OR
  MATCH(hosts.name) AGAINST('search term') OR
  MATCH(products.name, products.keywords, products.description, products.uid)
    AGAINST('search term')
ORDER BY score DESC;