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170 lines
5.3 KiB
170 lines
5.3 KiB
<?php |
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/** |
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* Meta API: WP_Metadata_Lazyloader class |
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* |
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* @package WordPress |
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* @subpackage Meta |
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* @since 4.5.0 |
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*/ |
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/** |
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* Core class used for lazy-loading object metadata. |
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* |
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* When loading many objects of a given type, such as posts in a WP_Query loop, it often makes |
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* sense to prime various metadata caches at the beginning of the loop. This means fetching all |
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* relevant metadata with a single database query, a technique that has the potential to improve |
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* performance dramatically in some cases. |
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* |
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* In cases where the given metadata may not even be used in the loop, we can improve performance |
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* even more by only priming the metadata cache for affected items the first time a piece of metadata |
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* is requested - ie, by lazy-loading it. So, for example, comment meta may not be loaded into the |
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* cache in the comments section of a post until the first time get_comment_meta() is called in the |
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* context of the comment loop. |
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* |
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* WP uses the WP_Metadata_Lazyloader class to queue objects for metadata cache priming. The class |
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* then detects the relevant get_*_meta() function call, and queries the metadata of all queued objects. |
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* |
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* Do not access this class directly. Use the wp_metadata_lazyloader() function. |
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* |
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* @since 4.5.0 |
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*/ |
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class WP_Metadata_Lazyloader { |
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/** |
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* Pending objects queue. |
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* |
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* @since 4.5.0 |
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* @var array |
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*/ |
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protected $pending_objects; |
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/** |
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* Settings for supported object types. |
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* |
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* @since 4.5.0 |
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* @var array |
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*/ |
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protected $settings = array(); |
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/** |
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* Constructor. |
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* |
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* @since 4.5.0 |
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*/ |
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public function __construct() { |
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$this->settings = array( |
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'term' => array( |
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'filter' => 'get_term_metadata', |
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'callback' => array( $this, 'lazyload_term_meta' ), |
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), |
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'comment' => array( |
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'filter' => 'get_comment_metadata', |
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'callback' => array( $this, 'lazyload_comment_meta' ), |
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), |
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); |
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} |
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/** |
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* Adds objects to the metadata lazy-load queue. |
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* |
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* @since 4.5.0 |
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* |
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* @param string $object_type Type of object whose meta is to be lazy-loaded. Accepts 'term' or 'comment'. |
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* @param array $object_ids Array of object IDs. |
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* @return bool|WP_Error True on success, WP_Error on failure. |
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*/ |
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public function queue_objects( $object_type, $object_ids ) { |
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if ( ! isset( $this->settings[ $object_type ] ) ) { |
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return new WP_Error( 'invalid_object_type', __( 'Invalid object type' ) ); |
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} |
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$type_settings = $this->settings[ $object_type ]; |
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if ( ! isset( $this->pending_objects[ $object_type ] ) ) { |
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$this->pending_objects[ $object_type ] = array(); |
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} |
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foreach ( $object_ids as $object_id ) { |
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// Keyed by ID for faster lookup. |
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if ( ! isset( $this->pending_objects[ $object_type ][ $object_id ] ) ) { |
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$this->pending_objects[ $object_type ][ $object_id ] = 1; |
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} |
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} |
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add_filter( $type_settings['filter'], $type_settings['callback'] ); |
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/** |
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* Fires after objects are added to the metadata lazy-load queue. |
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* |
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* @since 4.5.0 |
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* |
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* @param array $object_ids Array of object IDs. |
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* @param string $object_type Type of object being queued. |
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* @param WP_Metadata_Lazyloader $lazyloader The lazy-loader object. |
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*/ |
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do_action( 'metadata_lazyloader_queued_objects', $object_ids, $object_type, $this ); |
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} |
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/** |
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* Resets lazy-load queue for a given object type. |
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* |
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* @since 4.5.0 |
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* |
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* @param string $object_type Object type. Accepts 'comment' or 'term'. |
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* @return bool|WP_Error True on success, WP_Error on failure. |
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*/ |
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public function reset_queue( $object_type ) { |
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if ( ! isset( $this->settings[ $object_type ] ) ) { |
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return new WP_Error( 'invalid_object_type', __( 'Invalid object type' ) ); |
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} |
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$type_settings = $this->settings[ $object_type ]; |
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$this->pending_objects[ $object_type ] = array(); |
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remove_filter( $type_settings['filter'], $type_settings['callback'] ); |
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} |
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/** |
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* Lazy-loads term meta for queued terms. |
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* |
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* This method is public so that it can be used as a filter callback. As a rule, there |
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* is no need to invoke it directly. |
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* |
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* @since 4.5.0 |
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* |
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* @param mixed $check The `$check` param passed from the 'get_term_metadata' hook. |
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* @return mixed In order not to short-circuit `get_metadata()`. Generally, this is `null`, but it could be |
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* another value if filtered by a plugin. |
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*/ |
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public function lazyload_term_meta( $check ) { |
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if ( ! empty( $this->pending_objects['term'] ) ) { |
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update_termmeta_cache( array_keys( $this->pending_objects['term'] ) ); |
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// No need to run again for this set of terms. |
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$this->reset_queue( 'term' ); |
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} |
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return $check; |
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} |
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/** |
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* Lazy-loads comment meta for queued comments. |
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* |
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* This method is public so that it can be used as a filter callback. As a rule, there is no need to invoke it |
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* directly, from either inside or outside the `WP_Query` object. |
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* |
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* @since 4.5.0 |
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* |
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* @param mixed $check The `$check` param passed from the {@see 'get_comment_metadata'} hook. |
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* @return mixed The original value of `$check`, so as not to short-circuit `get_comment_metadata()`. |
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*/ |
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public function lazyload_comment_meta( $check ) { |
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if ( ! empty( $this->pending_objects['comment'] ) ) { |
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update_meta_cache( 'comment', array_keys( $this->pending_objects['comment'] ) ); |
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// No need to run again for this set of comments. |
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$this->reset_queue( 'comment' ); |
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} |
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return $check; |
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} |
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}
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