How to optimize PHP's database connection and query performance?

How to optimize PHP's database connection and query performance?

The database is an indispensable part of Web development, and PHP, as a widely used server-side scripting language, its connection to the database and query performance are crucial to the performance of the entire system. This article will introduce some tips and suggestions for optimizing PHP database connection and query performance.

1. Use persistent connections:
   In PHP, a database connection is established every time a database query is executed. Persistent connections can reuse the same database connection in multiple queries, thereby reducing the cost of connection establishment. Persistent connections can be implemented through extensions such as mysqli and PDO, by simply marking the connection as persistent.
2. Set the connection pool size reasonably:
   The connection pool is a buffer pool used to store and manage database connections. Properly setting the connection pool size can ensure that the system can handle database requests normally under high concurrency conditions. If the connection pool is too large, it will occupy too many system resources; if the connection pool is too small, requests may be queued waiting for the connection to be released. This can be adjusted by modifying the configuration parameters of the database connection pool.
3. Use prepared statements:
   Preprocessed statements can separate SQL statements and parameters, thereby avoiding the overhead of parsing and optimizing SQL statements for each query, and improving query performance. In PHP, you can use the prepared statement function provided by extensions such as mysqli and PDO to separate parameters from SQL statements, and then bind parameters for query.
4. Reduce the number of queries:
   Reducing the number of database queries is a common database optimization strategy. The number of complex queries can be reduced by properly designing the table structure and indexes of the database, and using JOIN statements and subqueries. In addition, you can consider using cache to store some frequently queried data, such as using Redis as a cache to store query results to avoid frequent database queries.
5. Use appropriate indexes:
   Indexes can speed up database queries. In PHP, you can add indexes to a table by using the CREATE INDEX statement, and select the appropriate index type according to actual needs. However, indexes also have some side effects, such as increasing the overhead of write operations and taking up storage space. Therefore, there is a trade-off between query performance and write performance when designing indexes.
6. Database sub-database and sub-table:
   When the amount of system data increases to a certain level, a single database may not be able to meet the query performance requirements. At this time, you can consider splitting the database into multiple libraries or splitting the table into multiple tables to distribute the database load. In PHP, you can use distributed databases or sharding technology based on consistent hashing to shard databases and tables.
7. Use cache:

Cache is a common means to improve system performance. Some query results or calculation results can be cached and read directly from the cache during the next query, avoiding access to the database. In PHP, you can use extensions such as Memcache or Redis to implement caching functions.

In summary, optimizing PHP's database connection and query performance requires comprehensive consideration of multiple aspects, including reducing connection establishment overhead, setting the connection pool size appropriately, using preprocessing statements, reducing the number of queries, and using appropriate Indexing, database sharding, and using cache, etc. By properly applying these tips and suggestions, you can improve system performance and user experience.

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