Caching And Custom Fields: Optimizing Your Wordpress Site

Improving Performance with Caching and Custom Fields

Custom fields in WordPress allow you to store extra data attached to posts, pages, or custom post types. This can be very useful for adding related information to your content. However, custom fields can also lead to performance issues if not used carefully, especially on sites with a lot of traffic and content.

Excessive custom fields can create bloated database tables that are resource intensive to query. They can also easily lead to slow and complex database queries that put strain on your server. In this guide, we’ll explore strategies for optimizing your use of custom fields in WordPress. This includes implementing caching to reduce database load as well as optimizing custom field usage through careful query planning and limiting requests.

What’s Slowing Down My Site?

The first step in speeding up a WordPress site using custom fields more efficiently is identifying where performance bottlenecks exist. There are a few key indicators that custom fields and related queries may be causing slow downs.

Table of Contents

Identifying database queries and custom fields as performance bottlenecks

The main contributor to WordPress performance issues from custom fields is increased database load. Queries that check for custom field values can be complex and scan large amounts of data, creating strain. This manifests in symptoms like:

Slow initial page load times
Lag when interacting with site features
Spikes in database CPU or memory usage

These can indicate that your database is being overwhelmed with requests related to custom fields. Some example queries that demonstrate this issue are explored next.

Examples of slow queries from custom fields

Let’s look at some actual custom field queries that could cause performance regressions. For example, consider a site storing extra data like ratings and categories in custom fields across different post types like movies and books.

Fetching all movies with a rating over 4 stars could involve a slow post meta query like:

SELECT * 
FROM wp_posts
INNER JOIN wp_postmeta
    ON (wp_posts.ID = wp_postmeta.post_id)
WHERE wp_posts.post_type = 'movies'
    AND ( wp_postmeta.meta_key = 'rating' AND CAST(wp_postmeta.meta_value AS SIGNED) > 4 )

Similarly, getting related category information across both movies and books using custom taxonomy and field data might look like:

SELECT DISTINCT wp_posts.*, wp_postmeta.* 
FROM wp_posts  
INNER JOIN wp_term_relationships
    ON (wp_posts.ID = wp_term_relationships.object_id)
INNER JOIN wp_postmeta
    ON (wp_posts.ID = wp_postmeta.post_id)
WHERE (wp_term_relationships.term_taxonomy_id IN (15, 28, 31))
  AND 
    (
      (wp_posts.post_type = 'books' AND wp_postmeta.meta_key = 'category')
      OR  
      (wp_posts.post_type = 'movies' AND wp_postmeta.meta_key = 'genre')
    )

These types of queries require Accessing information across multiple database tables and can be very slow with sufficient data size and traffic. Caching and optimization approaches explored in the next sections can help.

Implementing Object Caching

A very effective way to reduce database load from custom field queries is implementing some form of object caching. This involves storing a copy of database queries and results in a persistent, fast cache like memory or Redis instead of hitting the database each time.

Explanation of object caching to reduce database load

With object caching enabled, when a query like those in the prior section need to run, the cache will be checked first to see if the result set is available there. If a cache hit occurs, the cached data is served instead of running the actual query. This saves tremendous database resources over time.

By default, caches will invalidate after a certain time period or when the underlying data changes. So further queries will again hit the database. But during periods of repeated reads without data changes, the cache can shoulder almost all the load.

Code examples of setting up persistent caching

Implementing object caching requires using a persistent store like Memcached or Redis and integrating this with WordPress through a system like the built-in WordPress Object Cache. Let’s walk through a simple setup using Redis as an example backend:

Get Redis server installed and running locally or on a cloud provider
Install WordPress Redis plugin via command line:

wp plugin install redis-cache
Activate Redis object cache plugin in WordPress admin
Add wp-config.php code to connect Redis with credentials:

define( 'WP_CACHE_KEY_SALT', 'unique phrase' );
define( 'WP_REDIS_HOST', '127.0.0.1' );
define( 'WP_REDIS_PORT', 6379 );
define( 'WP_REDIS_PASSWORD', 'redispass' );

After following these steps, there will now be an active Redis integration that can work to improve custom field query performance. More advanced configurations are possible, like adding persistence for permanent storage of cache data.

Optimizing Custom Field Usage

In addition to backend caching, optimizing how custom fields are queried and used in code can also help minimize performance impacts. There are WordPress-specific approaches as well as more general web development best practices that are beneficial.

Strategies like limiting queries and using caching plugins

Some WordPress-focused optimization techniques for custom field usage include:

Limit queries: Structure code to minimize total queries needed instead of separate queries for each custom field.
Strategic queries: Fetch only the specific custom fields needed for a template vs all fields.
Caching plugins: Server or browser caching of custom field output using available plugins.

These types of optimizations can make all custom field interactions faster without requiring backend changes. Some example code is next.

Code examples to implement query optimization

Applying custom field query best practices can look like:

// Bad: separate queries for each custom field
$plot = get_post_meta( $post_id, 'plot', true ); 
$rating = get_post_meta( $post_id, 'rating', true );

// Good: single query for all needed fields
$meta_fields = get_post_meta( $post_id, ['plot', 'rating'] );  
$plot = $meta_fields['plot'][0];
$rating = $meta_fields['rating'][0];

For caching, enabling a browser caching plugin and adding cache headers:

// Plugin setup
add_action( 'init', 'cache_enable' );
function cache_enable() {
  wp_enqueue_script( 'cache-plugin' ); 
}

// Cache output
$value = get_post_meta( $post_id, 'my_field', true );
header("Cache-Control: max-age=3600"); 
echo $value;

These patterns can significantly cut down on custom field overhead.

Caching Plugins for Custom Fields

In addition to object caching at the database level, implementing caching specifically for custom field queries and output can also boost performance. WordPress plugins exist that integrate various types of caching with custom field data.

Overview of plugin options like WP Query Cache and Cache Enabler

Some top plugins that can cache custom field queries and output include:

WP Query Cache: Intercepts queries for caching using WordPress transients API.
Cache Enabler: Browser and server caching of output from themes and plugins.
Hummingbird: Caching module with specific integration for custom field performance.

These plugins offer caching capabilities focused on aspects of custom fields and queries versus general page caching. They have options targeted at common WordPress pain points like custom post meta queries.

Configuration walkthroughs to enable custom field caching

Taking Cache Enabler as an example, integrating it with custom field output for caching involves:

Install and network activate plugin
Add cache headers to target output code:

 
// Fetch custom field
$data = get_post_meta( $post_id, 'key', true );

// Cache output for 1 hour 
Cache_Enabler::add_cache_headers( 3600 );

Whitelist necessary endpoints
Configure any necessary exemptions

With steps like these, plugins can dynamically handle caching of custom fields, shielding databases and systems from overload.

Measuring Performance Improvements

Leveraging caching and custom field optimization provides many opportunities for performance and efficiency gains. However, quantifying these improvements is key for properly evaluating and tuning the approaches discussed.

Using tools like query monitors to benchmark gains

By establishing performance baselines before applying optimizations and comparing after, tangible gains can be measured. Some useful WordPress tools include:

Query monitors: Plugins showing database queries, time, and resources.
Xdebug Profiler: Detailed traces of PHP scripts and functions.
New Relic: Application performance monitor with breakdowns.

These types of reprofiling tools show custom field specific metrics like number of queries, caching hit rate, and total query time that showcase optimization impact.

Interpreting metrics to refine caching approach

With performance data available, ongoing analysis and interpretation should occur to tune configurations. Some key statistics include:

Query counts: Needed queries should trend down over time from caching.
Cache hit rate: Higher percentages indicate sites benefiting from caching.
Query time: Individual query speed should improve after optimization.

Digging into metrics like these will demonstrate precisely where and how much custom field caching is improving site speed and throughput. This allows further tweaking of plugins and settings for maximal performance.

Getting Help with Further Optimization

Adopting caching strategies and careful custom field usage as detailed in this guide can provide huge performance and efficiency lifts for WordPress sites. However, fully optimizing at scale can require additional effort and expertise.

For sites with heavy traffic and complexity, developers and firms specializing in advanced WordPress implementations can take optimizations even further through:

Additional tweaks for maximizing site speed

Low level database tuning
Custom caching code and architecture
Migrating custom fields to custom tables

Approaches like these require deep WordPress technical skills but can extract maximum performance at scale.

Recommended developers and firms who specialize in WordPress performance

Some top WordPress specialty firms include:

Pagely
Pantheon
WPEngine

These companies maintain teams focused solely on enterprise-grade WordPress implementations. They utilize leading practices like those covered here along with proprietary methods and tools to push WordPress sites to new performance heights.

Investing in their services can pay dividends for sites needing to scale while making heavy use of custom fields and similar functionality.

Caching And Custom Fields: Optimizing Your WordPress Site