Changeset 36566 for trunk/src/wp-includes/meta.php

Timestamp:

02/17/2016 10:57:33 PM (9 years ago)

Author:

boonebgorges

Message:

More performance improvements to metadata lazyloading.

Comment and term meta lazyloading for WP_Query loops, introduced in 4.4,
depended on filter callback methods belonging to WP_Query objects. This meant
storing WP_Query objects in the $wp_filter global (via add_filter()),
requiring that PHP retain the objects in memory, even when the local variables
would typically be expunged during normal garbage collection. In cases where a
large number of WP_Query objects were instantiated on a single pageload,
and/or where the contents of the WP_Query objects were quite large, serious
performance issues could result.

We skirt this problem by moving metadata lazyloading out of WP_Query. The
new WP_Metadata_Lazyloader class acts as a lazyload queue. Query instances
register items whose metadata should be lazyloaded - such as post terms, or
comments - and a WP_Metadata_Lazyloader method will intercept comment and
term meta requests to perform the cache priming. Since WP_Metadata_Lazyloader
instances are far smaller than WP_Query (containing only object IDs), and
clean up after themselves far better than the previous WP_Query methods (bp
only running their callbacks a single time for a given set of queued objects),
the resource use is decreased dramatically.

See [36525] for an earlier step in this direction.

Props lpawlik, stevegrunwell, boonebgorges.
Fixes #35816.

File:

• trunk/src/wp-includes/meta.php (modified) (1 diff)

trunk/src/wp-includes/meta.php

@@ -853 +853 @@
 
 /**
+ * Get the metadata lazyloading queue.
+ *
+ * @since 4.5.0
+ *
+ * @return WP_Metadata_Lazyloader $lazyloader Metadata lazyloader queue.
+ */
+function wp_metadata_lazyloader() {
+    static $wp_metadata_lazyloader;
+
+    if ( null === $wp_metadata_lazyloader ) {
+        $wp_metadata_lazyloader = new WP_Metadata_Lazyloader();
+    }
+
+    return $wp_metadata_lazyloader;
+}
+
+/**
  * Given a meta query, generates SQL clauses to be appended to a main query.
  *