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1 <?php |
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2 /** |
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3 * Meta API: WP_Metadata_Lazyloader class |
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4 * |
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5 * @package WordPress |
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6 * @subpackage Meta |
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7 * @since 4.5.0 |
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8 */ |
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9 |
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10 /** |
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11 * Core class used for lazy-loading object metadata. |
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12 * |
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13 * When loading many objects of a given type, such as posts in a WP_Query loop, it often makes |
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14 * sense to prime various metadata caches at the beginning of the loop. This means fetching all |
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15 * relevant metadata with a single database query, a technique that has the potential to improve |
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16 * performance dramatically in some cases. |
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17 * |
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18 * In cases where the given metadata may not even be used in the loop, we can improve performance |
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19 * even more by only priming the metadata cache for affected items the first time a piece of metadata |
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20 * is requested - ie, by lazy-loading it. So, for example, comment meta may not be loaded into the |
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21 * cache in the comments section of a post until the first time get_comment_meta() is called in the |
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22 * context of the comment loop. |
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23 * |
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24 * WP uses the WP_Metadata_Lazyloader class to queue objects for metadata cache priming. The class |
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25 * then detects the relevant get_*_meta() function call, and queries the metadata of all queued objects. |
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26 * |
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27 * Do not access this class directly. Use the wp_metadata_lazyloader() function. |
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28 * |
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29 * @since 4.5.0 |
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30 */ |
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31 class WP_Metadata_Lazyloader { |
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32 /** |
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33 * Pending objects queue. |
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34 * |
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35 * @since 4.5.0 |
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36 * @var array |
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37 */ |
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38 protected $pending_objects; |
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39 |
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40 /** |
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41 * Settings for supported object types. |
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42 * |
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43 * @since 4.5.0 |
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44 * @var array |
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45 */ |
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46 protected $settings = array(); |
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47 |
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48 /** |
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49 * Constructor. |
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50 * |
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51 * @since 4.5.0 |
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52 */ |
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53 public function __construct() { |
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54 $this->settings = array( |
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55 'term' => array( |
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56 'filter' => 'get_term_metadata', |
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57 'callback' => array( $this, 'lazyload_term_meta' ), |
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58 ), |
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59 'comment' => array( |
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60 'filter' => 'get_comment_metadata', |
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61 'callback' => array( $this, 'lazyload_comment_meta' ), |
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62 ), |
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63 ); |
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64 } |
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65 |
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66 /** |
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67 * Adds objects to the metadata lazy-load queue. |
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68 * |
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69 * @since 4.5.0 |
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70 * |
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71 * @param string $object_type Type of object whose meta is to be lazy-loaded. Accepts 'term' or 'comment'. |
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72 * @param array $object_ids Array of object IDs. |
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73 * @return bool|WP_Error True on success, WP_Error on failure. |
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74 */ |
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75 public function queue_objects( $object_type, $object_ids ) { |
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76 if ( ! isset( $this->settings[ $object_type ] ) ) { |
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77 return new WP_Error( 'invalid_object_type', __( 'Invalid object type' ) ); |
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78 } |
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79 |
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80 $type_settings = $this->settings[ $object_type ]; |
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81 |
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82 if ( ! isset( $this->pending_objects[ $object_type ] ) ) { |
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83 $this->pending_objects[ $object_type ] = array(); |
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84 } |
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85 |
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86 foreach ( $object_ids as $object_id ) { |
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87 // Keyed by ID for faster lookup. |
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88 if ( ! isset( $this->pending_objects[ $object_type ][ $object_id ] ) ) { |
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89 $this->pending_objects[ $object_type ][ $object_id ] = 1; |
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90 } |
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91 } |
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92 |
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93 add_filter( $type_settings['filter'], $type_settings['callback'] ); |
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94 |
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95 /** |
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96 * Fires after objects are added to the metadata lazy-load queue. |
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97 * |
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98 * @since 4.5.0 |
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99 * |
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100 * @param array $object_ids Object IDs. |
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101 * @param string $object_type Type of object being queued. |
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102 * @param WP_Metadata_Lazyloader $lazyloader The lazy-loader object. |
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103 */ |
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104 do_action( 'metadata_lazyloader_queued_objects', $object_ids, $object_type, $this ); |
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105 } |
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106 |
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107 /** |
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108 * Resets lazy-load queue for a given object type. |
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109 * |
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110 * @since 4.5.0 |
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111 * |
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112 * @param string $object_type Object type. Accepts 'comment' or 'term'. |
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113 * @return bool|WP_Error True on success, WP_Error on failure. |
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114 */ |
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115 public function reset_queue( $object_type ) { |
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116 if ( ! isset( $this->settings[ $object_type ] ) ) { |
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117 return new WP_Error( 'invalid_object_type', __( 'Invalid object type' ) ); |
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118 } |
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119 |
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120 $type_settings = $this->settings[ $object_type ]; |
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121 |
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122 $this->pending_objects[ $object_type ] = array(); |
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123 remove_filter( $type_settings['filter'], $type_settings['callback'] ); |
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124 } |
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125 |
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126 /** |
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127 * Lazy-loads term meta for queued terms. |
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128 * |
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129 * This method is public so that it can be used as a filter callback. As a rule, there |
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130 * is no need to invoke it directly. |
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131 * |
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132 * @since 4.5.0 |
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133 * |
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134 * @param mixed $check The `$check` param passed from the 'get_term_metadata' hook. |
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135 * @return mixed In order not to short-circuit `get_metadata()`. Generally, this is `null`, but it could be |
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136 * another value if filtered by a plugin. |
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137 */ |
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138 public function lazyload_term_meta( $check ) { |
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139 if ( ! empty( $this->pending_objects['term'] ) ) { |
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140 update_termmeta_cache( array_keys( $this->pending_objects['term'] ) ); |
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141 |
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142 // No need to run again for this set of terms. |
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143 $this->reset_queue( 'term' ); |
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144 } |
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145 |
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146 return $check; |
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147 } |
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148 |
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149 /** |
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150 * Lazy-loads comment meta for queued comments. |
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151 * |
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152 * 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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153 * directly, from either inside or outside the `WP_Query` object. |
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154 * |
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155 * @since 4.5.0 |
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156 * |
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157 * @param mixed $check The `$check` param passed from the {@see 'get_comment_metadata'} hook. |
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158 * @return mixed The original value of `$check`, so as not to short-circuit `get_comment_metadata()`. |
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159 */ |
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160 public function lazyload_comment_meta( $check ) { |
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161 if ( ! empty( $this->pending_objects['comment'] ) ) { |
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162 update_meta_cache( 'comment', array_keys( $this->pending_objects['comment'] ) ); |
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163 |
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164 // No need to run again for this set of comments. |
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165 $this->reset_queue( 'comment' ); |
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166 } |
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167 |
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168 return $check; |
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169 } |
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170 } |