Full-text index implementation and optimization in MySQL

MySQL is a commonly used relational database management system with the advantages of high reliability and strong performance. Full-text search is an important function of MySQL, which can search text content through keywords. This article will introduce the implementation and optimization of full-text search in MySQL.

1. The concept and purpose of full-text retrieval

Full-text retrieval is to solve the shortcomings of traditional database query methods for text data query. It builds an index for a string type field, performs fuzzy matching on this field, can implement keyword search functions, and provides users with a convenient query method. Compared with fuzzy queries, full-text retrieval is more efficient, the results are more accurate, and the response is faster. MySQL's full-text search function mainly includes statements such as MATCH and AGAINST, which can achieve efficient full-text search.

2. Implementation of MySQL full-text retrieval

Full-text retrieval in MySQL is achieved by creating a full-text index. This index refers to the appropriate processing of words, phrases, etc. in text data to enable efficient and accurate searches and improve retrieval efficiency. Compared with ordinary indexes, the biggest difference between full-text indexing and ordinary indexing is the word segmentation of text content.

1. Create a full-text index

In MySQL, you need to use the FULLTEXT keyword to create a full-text index. It limits the field type to the TEXT type when creating a table, and creates a full-text index when you need to create a full-text index. Add a FULLTEXT index after the full-text index field. The specific operation is as follows:

CREATE TABLE article (

id INT UNSIGNED AUTO_INCREMENT NOT NULL PRIMARY KEY,
title VARCHAR(200) NOT NULL,
content TEXT NOT NULL,
FULLTEXT (title, content)

);

Through the above operations, you can add title, The content field creates a full-text index to achieve efficient and accurate full-text retrieval.

2. MATCH, AGAINST statement

In MySQL, MATCH refers to the full-text search for the FULLTEXT index. It specifies the fields to be retrieved and the search terms that need to be matched. The specific syntax As follows:

SELECT * FROM article WHERE MATCH (title, content) AGAINST ('search term');

When using the MATCH statement, you must specify the fields and keywords to be searched, MySQL All rows matching the keyword will be returned. Among them, AGAINST represents the search keyword, which must be placed in single quotes or double quotes, such as 'search term' or 'search term'.

It should be noted that only the InnoDB engine supports full-text search, and for the MyISAM engine, the FULLTEXT index must be added when designing the table.

3. MySQL full-text index optimization

1. Optimizing the use of MATCH AGAINST

In MySQL, the full-text index is required when executing the MATCH AGAINST statement. When long text is indexed in full text, its performance will be affected to a certain extent. Therefore, we can optimize in the following ways:

(1) Properly format and clean the fields to be full-text indexed, remove useless information, and reduce the amount of data for full-text search.

(2) Optimize keywords for FULLTEXT search. Keywords can be "word segmented" to remove meaningless words or punctuation to avoid searching for irrelevant words.

(3) Set the parameters of the maximum number of columns and the maximum number of rows to limit the full-text index search range and improve performance.

2. Using multi-field index

In MySQL, when creating a full-text index, you can create indexes on multiple fields at the same time. If the query statement involves full-text retrieval of multiple fields, you can use a multi-field index, which can greatly improve retrieval performance. The specific method is to list the fields that need to be indexed in order after the FULLTEXT keyword, as follows:

CREATE TABLE article (

id INT UNSIGNED AUTO_INCREMENT NOT NULL PRIMARY KEY,
title VARCHAR(200) NOT NULL,
author VARCHAR(50) NOT NULL,
content TEXT NOT NULL,
FULLTEXT (title, author, content)

);

At the same time, you need to use the MATCH AGAINST statement Specify the search fields in the order given in the FULLTEXT index, as follows:

SELECT * FROM article WHERE MATCH (title, author, content) AGAINST ('search term');

3. Use memcached, CDN and other caching technologies

In MySQL, full-text search will match the search conditions and then return the results. If the data volume is large and the complexity is high, the query time will become longer and the query performance will be affected. You can use caching technology, such as memcached, CDN and other technologies, to cache the results of full-text retrieval. For the next same query, the results will be fetched directly from the cache to improve the retrieval speed.

4. Summary

The full-text search function of MySQL makes the search more efficient, accurate and fast. Full-text retrieval is achieved by creating a full-text index and using MATCH and AGAINST statements for retrieval. There are many tips for optimizing full-text search query performance, including optimizing keywords, multi-field indexes, caching technology, etc. In practical applications, based on specific retrieval requirements and data scale, rational use of these optimization techniques will lead to better query results.

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