As the sun rises and the forest mist clears, and the clouds return and the caves darken, these changes of light and shadow are the morning and evening in the mountains. Wildflowers bloom with their subtle fragrance, fine trees flourish with their dense shade, the wind and frost are pure and clean, and the water recedes to reveal the rocks—these are the four seasons in the mountains. Going out in the morning and returning in the evening, the scenery of the four seasons is different, and the joy is endless.至于负者歌于途,行者休于树,前者呼,后者应,伛偻提携,往来而不绝者,滁人游也。临溪而渔,溪深而鱼肥,酿泉为酒,泉香而酒洌,山肴野蔌,杂然而前陈者,太守宴也。宴酣之乐,非丝非竹,射者中,弈者胜,觥筹交错,起坐而喧哗者,众宾欢也。苍颜白发,颓然乎其间者,太守醉也。
<?php
/**
* Meta API: WP_Metadata_Lazyloader class
*
* @package WordPress
* @subpackage Meta
* @since 4.5.0
*/
/**
* Core class used for lazy-loading object metadata.
*
* When loading many objects of a given type, such as posts in a WP_Query loop, it often makes
* sense to prime various metadata caches at the beginning of the loop. This means fetching all
* relevant metadata with a single database query, a technique that has the potential to improve
* performance dramatically in some cases.
*
* In cases where the given metadata may not even be used in the loop, we can improve performance
* even more by only priming the metadata cache for affected items the first time a piece of metadata
* is requested - ie, by lazy-loading it. So, for example, comment meta may not be loaded into the
* cache in the comments section of a post until the first time get_comment_meta() is called in the
* context of the comment loop.
*
* WP uses the WP_Metadata_Lazyloader class to queue objects for metadata cache priming. The class
* then detects the relevant get_*_meta() function call, and queries the metadata of all queued objects.
*
* Do not access this class directly. Use the wp_metadata_lazyloader() function.
*
* @since 4.5.0
*/
#[AllowDynamicProperties]
class WP_Metadata_Lazyloader {
/**
* Pending objects queue.
*
* @since 4.5.0
* @var array
*/
protected $pending_objects;
/**
* Settings for supported object types.
*
* @since 4.5.0
* @var array
*/
protected $settings = array();
/**
* Constructor.
*
* @since 4.5.0
*/
public function __construct() {
$this->settings = array(
'term' => array(
'filter' => 'get_term_metadata',
'callback' => array( $this, 'lazyload_meta_callback' ),
),
'comment' => array(
'filter' => 'get_comment_metadata',
'callback' => array( $this, 'lazyload_meta_callback' ),
),
'blog' => array(
'filter' => 'get_blog_metadata',
'callback' => array( $this, 'lazyload_meta_callback' ),
),
);
}
/**
* Adds objects to the metadata lazy-load queue.
*
* @since 4.5.0
*
* @param string $object_type Type of object whose meta is to be lazy-loaded. Accepts 'term' or 'comment'.
* @param array $object_ids Array of object IDs.
* @return void|WP_Error WP_Error on failure.
*/
public function queue_objects( $object_type, $object_ids ) {
if ( ! isset( $this->settings[ $object_type ] ) ) {
return new WP_Error( 'invalid_object_type', __( 'Invalid object type.' ) );
}
$type_settings = $this->settings[ $object_type ];
if ( ! isset( $this->pending_objects[ $object_type ] ) ) {
$this->pending_objects[ $object_type ] = array();
}
foreach ( $object_ids as $object_id ) {
// Keyed by ID for faster lookup.
if ( ! isset( $this->pending_objects[ $object_type ][ $object_id ] ) ) {
$this->pending_objects[ $object_type ][ $object_id ] = 1;
}
}
add_filter( $type_settings['filter'], $type_settings['callback'], 10, 5 );
/**
* Fires after objects are added to the metadata lazy-load queue.
*
* @since 4.5.0
*
* @param array $object_ids Array of object IDs.
* @param string $object_type Type of object being queued.
* @param WP_Metadata_Lazyloader $lazyloader The lazy-loader object.
*/
do_action( 'metadata_lazyloader_queued_objects', $object_ids, $object_type, $this );
}
/**
* Resets lazy-load queue for a given object type.
*
* @since 4.5.0
*
* @param string $object_type Object type. Accepts 'comment' or 'term'.
* @return void|WP_Error WP_Error on failure.
*/
public function reset_queue( $object_type ) {
if ( ! isset( $this->settings[ $object_type ] ) ) {
return new WP_Error( 'invalid_object_type', __( 'Invalid object type.' ) );
}
$type_settings = $this->settings[ $object_type ];
$this->pending_objects[ $object_type ] = array();
remove_filter( $type_settings['filter'], $type_settings['callback'] );
}
/**
* Lazy-loads term meta for queued terms.
*
* This method is public so that it can be used as a filter callback. As a rule, there
* is no need to invoke it directly.
*
* @since 4.5.0
* @deprecated 6.3.0 Use WP_Metadata_Lazyloader::lazyload_meta_callback() instead.
*
* @param mixed $check The `$check` param passed from the 'get_term_metadata' hook.
* @return mixed In order not to short-circuit `get_metadata()`. Generally, this is `null`, but it could be
* another value if filtered by a plugin.
*/
public function lazyload_term_meta( $check ) {
_deprecated_function( __METHOD__, '6.3.0', 'WP_Metadata_Lazyloader::lazyload_meta_callback' );
return $this->lazyload_meta_callback( $check, 0, '', false, 'term' );
}
/**
* Lazy-loads comment meta for queued comments.
*
* This method is public so that it can be used as a filter callback. As a rule, there is no need to invoke it
* directly, from either inside or outside the `WP_Query` object.
*
* @since 4.5.0
* @deprecated 6.3.0 Use WP_Metadata_Lazyloader::lazyload_meta_callback() instead.
*
* @param mixed $check The `$check` param passed from the {@see 'get_comment_metadata'} hook.
* @return mixed The original value of `$check`, so as not to short-circuit `get_comment_metadata()`.
*/
public function lazyload_comment_meta( $check ) {
_deprecated_function( __METHOD__, '6.3.0', 'WP_Metadata_Lazyloader::lazyload_meta_callback' );
return $this->lazyload_meta_callback( $check, 0, '', false, 'comment' );
}
/**
* Lazy-loads meta for queued objects.
*
* This method is public so that it can be used as a filter callback. As a rule, there
* is no need to invoke it directly.
*
* @since 6.3.0
*
* @param mixed $check The `$check` param passed from the 'get_*_metadata' hook.
* @param int $object_id ID of the object metadata is for.
* @param string $meta_key Unused.
* @param bool $single Unused.
* @param string $meta_type Type of object metadata is for. Accepts 'post', 'comment', 'term', 'user',
* or any other object type with an associated meta table.
* @return mixed In order not to short-circuit `get_metadata()`. Generally, this is `null`, but it could be
* another value if filtered by a plugin.
*/
public function lazyload_meta_callback( $check, $object_id, $meta_key, $single, $meta_type ) {
if ( empty( $this->pending_objects[ $meta_type ] ) ) {
return $check;
}
$object_ids = array_keys( $this->pending_objects[ $meta_type ] );
if ( $object_id && ! in_array( $object_id, $object_ids, true ) ) {
$object_ids[] = $object_id;
}
update_meta_cache( $meta_type, $object_ids );
// No need to run again for this set of objects.
$this->reset_queue( $meta_type );
return $check;
}
}