How to Implement Caching for Database Queries with wpdb in WordPress Plugin
Posted on 20th June 2023
Caching is a common technique for optimizing web applications. It can speed up your website by caching static resources like images and CSS files, and by caching dynamic content like database queries.
When it comes to WordPress plugins, caching can be a great way to improve performance. In this article, we’ll show you how to implement caching for database queries with wpdb in WordPress Plugin.
First, you need to install and activate the WP Query Cache plugin. For more information, please see our article on how to install a WordPress plugin.
Once the plugin is activated, it will start caching all your WordPress database queries. However, it’s not always ideal to cache all database queries. For example, you might not want to cache queries that are made when a user is logged in, or queries that are made to the WordPress admin area.
To exclude certain database queries from being cached, you need to add a filter to your WordPress code. The following code snippet shows how to exclude queries made to the WordPress admin area:
add_filter( ‘wpdb_query_args’, function( $args ) {
if ( is_admin() ) {
$args[‘no_cache’] = true;
}
return $args;
} );
This code snippet shows how to exclude queries made when a user is logged in:
add_filter( ‘wpdb_query_args’, function( $args ) {
if ( is_user_logged_in() ) {
$args[‘no_cache’] = true;
}
return $args;
} );
You can also use the wpdb_query_args filter to exclude specific database tables from being cached. For example, the following code snippet excludes all database queries made to the wp_options table:
add_filter( ‘wpdb_query_args’, function( $args ) {
if ( isset( $args[‘table’] ) && $args[‘table’] === ‘wp_options’ ) {
$args[‘no_cache’] = true;
}
return $args;
} );
You can also use this filter to exclude specific database queries based on their SQL syntax. For example, the following code snippet excludes all database queries that use the LIKE operator:
add_filter( ‘wpdb_query_args’, function( $args ) {
if ( isset( $args[‘sql’] ) && strpos( $args[‘sql’], ‘LIKE’ ) !== false ) {
$args[‘no_cache’] = true;
}
return $args;
} );
Once you’ve added the code snippet to your WordPress site, all database queries made to the WordPress admin area will be cached.
If you want to cache database queries made to specific tables or queries based on their SQL syntax, you can use the wpdb_query_args filter. This filter allows you to exclude certain database queries from being cached.
The WP Query Cache plugin is a great way to improve the performance of your WordPress site. It’s easy to use and it can speed up your website by caching database queries.
Caching is one of the most important performance optimization techniques. It can speed up your website by reducing the number of requests to the server and reducing the amount of processing required for each request.
When it comes to caching database queries, there are two main approaches:
Caching the results of each query
Caching the entire database
Caching the results of each query
The first approach is to cache the results of each query. This can be done using the WordPress Transients API.
First, you need to add a code to your plugin that will check if a transient exists for the current query. If it does, it will return the cached results. Otherwise, it will run the query and store the results in a transient.
Here is an example:
if ( false === ( $results = get_transient( ‘my_plugin_query_results’ ) ) ) { // Run the query $results = $wpdb->get_results( $sql ); // Store the results in a transient set_transient( ‘my_plugin_query_results’, $results, DAY_IN_SECONDS ); }
In this example, we are using the get_transient() and set_transient() functions to check for and store the results of a query. The results are stored in a transient with the name ‘my_plugin_query_results’.
We are also using the DAY_IN_SECONDS constant to set the expiration time of the transient to one day. This means that the transient will be refreshed every day.
Caching the entire database
The second approach is to cache the entire database. This can be done using the WordPress Object Cache.
The Object Cache is a feature of WordPress that allows you to store data in memory for faster access. By default, the Object Cache is not enabled.
To enable the Object Cache, you need to add the following code to your wp-config.php file:
define( ‘WP_CACHE’, true );
Once the Object Cache is enabled, you can start caching your database. To do this, you need to use the wp_cache_add() function.
Here is an example:
$key = ‘my_plugin_db’; $value = $wpdb->get_results( $sql ); wp_cache_add( $key, $value, ”, DAY_IN_SECONDS );
In this example, we are using the wp_cache_add() function to cache the results of a database query. The results are stored in the Object Cache with the key ‘my_plugin_db’.
We are also using the DAY_IN_SECONDS constant to set the expiration time of the Object Cache to one day. This means that the Object Cache will be refreshed every day.
Conclusion
Caching is a powerful performance optimization technique that can speed up your website. When it comes to caching database queries, there are two main approaches: caching the results of each query and caching the entire database.
Both approaches have their own advantages and disadvantages. You need to decide which approach is best for your website.
If you want to implement caching for database queries with the wpdb class in WordPress, there are a few things you need to keep in mind. First, you need to make sure that the data you’re caching is static. This means that it doesn’t change often, if at all. Second, you need to make sure that the data you’re caching is not too large. If it is, it will take up too much memory and could slow down your website.
Third, you need to decide how long you want to cache the data. This will depend on how often the data changes. If it changes frequently, you’ll want to cache it for a shorter period of time. If it changes infrequently, you can cache it for a longer period of time. Finally, you need to decide where you want to store the cached data. The easiest option is to store it in a file, but you can also store it in a database or in memory.
Once you’ve decided how you’re going to cache the data, you need to write the code to do it. The first step is to create a function that will return the data you want to cache. This function should take one argument, which is the key you want to use to store the data in the cache. The function should then return the data you want to cache. For example, if you want to cache the results of a database query, the function might look like this:
function get_cached_data( $key ) {
// Code to get data from the database goes here…
return $data;
}
Once you have the function that will return the data you want to cache, you need to add the code to actually cache the data. The first step is to check if the data is already cached. You can do this by checking if the key exists in the cache. If it does, you can return the data from the cache. If it doesn’t, you need to cache the data. To do this, you first need to get the data from the function you created earlier. You then need to store the data in the cache. The code to do this might look like this:
function cache_data( $key, $data ) {
// Code to store data in the cache goes here…
}
Finally, you need to add the code to retrieve the data from the cache. This is similar to the code to cache the data, but you don’t need to check if the data is already cached. You can just get the data from the cache and return it. The code to do this might look like this:
function get_cached_data( $key ) {
// Code to get data from the cache goes here…
return $data;
}
You can then use these functions to cache the data you want to cache. For example, if you want to cache the results of a database query, you would use the following code:
$data = get_cached_data( ‘query_results’ );
if ( ! $data ) {
$data = get_results_from_database();
cache_data( ‘query_results’, $data );
}
return $data;
This code will first check if the data is already cached. If it is, it will return the data from the cache. If it isn’t, it will get the data from the database and cache it.
