Index: src/wp-admin/includes/ms.php
===================================================================
--- src/wp-admin/includes/ms.php	(revision 42444)
+++ src/wp-admin/includes/ms.php	(working copy)
@@ -135,6 +135,13 @@
 			$wpdb->query( "DROP TABLE IF EXISTS `$table`" );
 		}
 
+		if ( is_site_meta_supported() ) {
+			$blog_meta_ids = $wpdb->get_col( $wpdb->prepare( "SELECT meta_id FROM $wpdb->blogmeta WHERE blog_id = %d ", $blog_id ) );
+			foreach ( $blog_meta_ids as $mid ) {
+				delete_metadata_by_mid( 'blog', $mid );
+			}
+		}
+
 		$wpdb->delete( $wpdb->blogs, array( 'blog_id' => $blog_id ) );
 
 		/**
Index: src/wp-admin/includes/schema.php
===================================================================
--- src/wp-admin/includes/schema.php	(revision 42444)
+++ src/wp-admin/includes/schema.php	(working copy)
@@ -267,6 +267,15 @@
   PRIMARY KEY  (blog_id),
   KEY db_version (db_version)
 ) $charset_collate;
+CREATE TABLE $wpdb->blogmeta (
+  meta_id bigint(20) unsigned NOT NULL auto_increment,
+  blog_id bigint(20) NOT NULL default '0',
+  meta_key varchar(255) default NULL,
+  meta_value longtext,
+  PRIMARY KEY  (meta_id),
+  KEY meta_key (meta_key($max_index_length)),
+  KEY blog_id (blog_id)
+) $charset_collate;
 CREATE TABLE $wpdb->registration_log (
   ID bigint(20) NOT NULL auto_increment,
   email varchar(255) NOT NULL default '',
Index: src/wp-admin/includes/upgrade.php
===================================================================
--- src/wp-admin/includes/upgrade.php	(revision 42444)
+++ src/wp-admin/includes/upgrade.php	(working copy)
@@ -2133,6 +2133,13 @@
 			}
 		}
 	}
+
+	// 5.0
+	if ( $wp_current_db_version < 42125 ) {
+		$network_id = get_main_network_id();
+		delete_network_option( $network_id, 'site_meta_supported' );
+		is_site_meta_supported();
+	}
 }
 
 //
Index: src/wp-includes/class-wp-site-query.php
===================================================================
--- src/wp-includes/class-wp-site-query.php	(revision 42444)
+++ src/wp-includes/class-wp-site-query.php	(working copy)
@@ -92,86 +92,90 @@
 	 *
 	 * @since 4.6.0
 	 * @since 4.8.0 Introduced the 'lang_id', 'lang__in', and 'lang__not_in' parameters.
+	 * @since 5.0.0 Introduced the 'update_site_meta_cache' parameter.
 	 *
 	 * @param string|array $query {
 	 *     Optional. Array or query string of site query parameters. Default empty.
 	 *
-	 *     @type array        $site__in          Array of site IDs to include. Default empty.
-	 *     @type array        $site__not_in      Array of site IDs to exclude. Default empty.
-	 *     @type bool         $count             Whether to return a site count (true) or array of site objects.
-	 *                                           Default false.
-	 *     @type array        $date_query        Date query clauses to limit sites by. See WP_Date_Query.
-	 *                                           Default null.
-	 *     @type string       $fields            Site fields to return. Accepts 'ids' (returns an array of site IDs)
-	 *                                           or empty (returns an array of complete site objects). Default empty.
-	 *     @type int          $ID                A site ID to only return that site. Default empty.
-	 *     @type int          $number            Maximum number of sites to retrieve. Default 100.
-	 *     @type int          $offset            Number of sites to offset the query. Used to build LIMIT clause.
-	 *                                           Default 0.
-	 *     @type bool         $no_found_rows     Whether to disable the `SQL_CALC_FOUND_ROWS` query. Default true.
-	 *     @type string|array $orderby           Site status or array of statuses. Accepts 'id', 'domain', 'path',
-	 *                                           'network_id', 'last_updated', 'registered', 'domain_length',
-	 *                                           'path_length', 'site__in' and 'network__in'. Also accepts false,
-	 *                                           an empty array, or 'none' to disable `ORDER BY` clause.
-	 *                                           Default 'id'.
-	 *     @type string       $order             How to order retrieved sites. Accepts 'ASC', 'DESC'. Default 'ASC'.
-	 *     @type int          $network_id        Limit results to those affiliated with a given network ID. If 0,
-	 *                                           include all networks. Default 0.
-	 *     @type array        $network__in       Array of network IDs to include affiliated sites for. Default empty.
-	 *     @type array        $network__not_in   Array of network IDs to exclude affiliated sites for. Default empty.
-	 *     @type string       $domain            Limit results to those affiliated with a given domain. Default empty.
-	 *     @type array        $domain__in        Array of domains to include affiliated sites for. Default empty.
-	 *     @type array        $domain__not_in    Array of domains to exclude affiliated sites for. Default empty.
-	 *     @type string       $path              Limit results to those affiliated with a given path. Default empty.
-	 *     @type array        $path__in          Array of paths to include affiliated sites for. Default empty.
-	 *     @type array        $path__not_in      Array of paths to exclude affiliated sites for. Default empty.
-	 *     @type int          $public            Limit results to public sites. Accepts '1' or '0'. Default empty.
-	 *     @type int          $archived          Limit results to archived sites. Accepts '1' or '0'. Default empty.
-	 *     @type int          $mature            Limit results to mature sites. Accepts '1' or '0'. Default empty.
-	 *     @type int          $spam              Limit results to spam sites. Accepts '1' or '0'. Default empty.
-	 *     @type int          $deleted           Limit results to deleted sites. Accepts '1' or '0'. Default empty.
-	 *     @type int          $lang_id           Limit results to a language ID. Default empty.
-	 *     @type array        $lang__in          Array of language IDs to include affiliated sites for. Default empty.
-	 *     @type array        $lang__not_in      Array of language IDs to exclude affiliated sites for. Default empty.
-	 *     @type string       $search            Search term(s) to retrieve matching sites for. Default empty.
-	 *     @type array        $search_columns    Array of column names to be searched. Accepts 'domain' and 'path'.
-	 *                                           Default empty array.
-	 *     @type bool         $update_site_cache Whether to prime the cache for found sites. Default true.
+	 *     @type array        $site__in               Array of site IDs to include. Default empty.
+	 *     @type array        $site__not_in           Array of site IDs to exclude. Default empty.
+	 *     @type bool         $count                  Whether to return a site count (true) or array of site objects.
+	 *                                                Default false.
+	 *     @type array        $date_query             Date query clauses to limit sites by. See WP_Date_Query.
+	 *                                                Default null.
+	 *     @type string       $fields                 Site fields to return. Accepts 'ids' (returns an array of site IDs)
+	 *                                                or empty (returns an array of complete site objects). Default empty.
+	 *     @type int          $ID                     A site ID to only return that site. Default empty.
+	 *     @type int          $number                 Maximum number of sites to retrieve. Default 100.
+	 *     @type int          $offset                 Number of sites to offset the query. Used to build LIMIT clause.
+	 *                                                Default 0.
+	 *     @type bool         $no_found_rows          Whether to disable the `SQL_CALC_FOUND_ROWS` query. Default true.
+	 *     @type string|array $orderby                Site status or array of statuses. Accepts 'id', 'domain', 'path',
+	 *                                                'network_id', 'last_updated', 'registered', 'domain_length',
+	 *                                                'path_length', 'site__in' and 'network__in'. Also accepts false,
+	 *                                                an empty array, or 'none' to disable `ORDER BY` clause.
+	 *                                                Default 'id'.
+	 *     @type string       $order                  How to order retrieved sites. Accepts 'ASC', 'DESC'. Default 'ASC'.
+	 *     @type int          $network_id             Limit results to those affiliated with a given network ID. If 0,
+	 *                                                include all networks. Default 0.
+	 *     @type array        $network__in            Array of network IDs to include affiliated sites for. Default empty.
+	 *     @type array        $network__not_in        Array of network IDs to exclude affiliated sites for. Default empty.
+	 *     @type string       $domain                 Limit results to those affiliated with a given domain. Default empty.
+	 *     @type array        $domain__in             Array of domains to include affiliated sites for. Default empty.
+	 *     @type array        $domain__not_in         Array of domains to exclude affiliated sites for. Default empty.
+	 *     @type string       $path                   Limit results to those affiliated with a given path. Default empty.
+	 *     @type array        $path__in               Array of paths to include affiliated sites for. Default empty.
+	 *     @type array        $path__not_in           Array of paths to exclude affiliated sites for. Default empty.
+	 *     @type int          $public                 Limit results to public sites. Accepts '1' or '0'. Default empty.
+	 *     @type int          $archived               Limit results to archived sites. Accepts '1' or '0'. Default empty.
+	 *     @type int          $mature                 Limit results to mature sites. Accepts '1' or '0'. Default empty.
+	 *     @type int          $spam                   Limit results to spam sites. Accepts '1' or '0'. Default empty.
+	 *     @type int          $deleted                Limit results to deleted sites. Accepts '1' or '0'. Default empty.
+	 *     @type int          $lang_id                Limit results to a language ID. Default empty.
+	 *     @type array        $lang__in               Array of language IDs to include affiliated sites for. Default empty.
+	 *     @type array        $lang__not_in           Array of language IDs to exclude affiliated sites for. Default empty.
+	 *     @type string       $search                 Search term(s) to retrieve matching sites for. Default empty.
+	 *     @type array        $search_columns         Array of column names to be searched. Accepts 'domain' and 'path'.
+	 *                                                Default empty array.
+	 *     @type bool         $update_site_cache      Whether to prime the cache for found sites. Default true.
+	 *     @type bool         $update_site_meta_cache Whether to prime the metadata cache for found comments.
+	 *                                                Default true.
 	 * }
 	 */
 	public function __construct( $query = '' ) {
 		$this->query_var_defaults = array(
-			'fields'            => '',
-			'ID'                => '',
-			'site__in'          => '',
-			'site__not_in'      => '',
-			'number'            => 100,
-			'offset'            => '',
-			'no_found_rows'     => true,
-			'orderby'           => 'id',
-			'order'             => 'ASC',
-			'network_id'        => 0,
-			'network__in'       => '',
-			'network__not_in'   => '',
-			'domain'            => '',
-			'domain__in'        => '',
-			'domain__not_in'    => '',
-			'path'              => '',
-			'path__in'          => '',
-			'path__not_in'      => '',
-			'public'            => null,
-			'archived'          => null,
-			'mature'            => null,
-			'spam'              => null,
-			'deleted'           => null,
-			'lang_id'           => null,
-			'lang__in'          => '',
-			'lang__not_in'      => '',
-			'search'            => '',
-			'search_columns'    => array(),
-			'count'             => false,
-			'date_query'        => null, // See WP_Date_Query
-			'update_site_cache' => true,
+			'fields'                 => '',
+			'ID'                     => '',
+			'site__in'               => '',
+			'site__not_in'           => '',
+			'number'                 => 100,
+			'offset'                 => '',
+			'no_found_rows'          => true,
+			'orderby'                => 'id',
+			'order'                  => 'ASC',
+			'network_id'             => 0,
+			'network__in'            => '',
+			'network__not_in'        => '',
+			'domain'                 => '',
+			'domain__in'             => '',
+			'domain__not_in'         => '',
+			'path'                   => '',
+			'path__in'               => '',
+			'path__not_in'           => '',
+			'public'                 => null,
+			'archived'               => null,
+			'mature'                 => null,
+			'spam'                   => null,
+			'deleted'                => null,
+			'lang_id'                => null,
+			'lang__in'               => '',
+			'lang__not_in'           => '',
+			'search'                 => '',
+			'search_columns'         => array(),
+			'count'                  => false,
+			'date_query'             => null, // See WP_Date_Query
+			'update_site_cache'      => true,
+			'update_site_meta_cache' => true,
 		);
 
 		if ( ! empty( $query ) ) {
@@ -288,7 +292,7 @@
 
 		// Prime site network caches.
 		if ( $this->query_vars['update_site_cache'] ) {
-			_prime_site_caches( $site_ids );
+			_prime_site_caches( $site_ids, $this->query_vars['update_site_meta_cache'] );
 		}
 
 		// Fetch full site objects from the primed cache.
Index: src/wp-includes/functions.php
===================================================================
--- src/wp-includes/functions.php	(revision 42444)
+++ src/wp-includes/functions.php	(working copy)
@@ -4717,6 +4717,40 @@
 }
 
 /**
+ * Determines whether site meta is enabled.
+ *
+ * This function checks whether the 'blogmeta' database table exists. The result is saved as
+ * a setting for the main network, making it essentially a global setting. Subsequent requests
+ * will refer to this setting instead of running the query. The $force parameter can be used
+ * to bypass the setting, and reset it accordingly, however this is not recommended.
+ *
+ * The 'is_site_meta_supported' filter can be used to bypass the database checks completely.
+ *
+ * @since 4.9.0
+ *
+ * @global wpdb $wpdb WordPress database abstraction object.
+ *
+ * @return bool True if site meta is supported, false otherwise.
+ */
+function is_site_meta_supported() {
+	global $wpdb;
+
+	if ( ! is_multisite() ) {
+		return false;
+	}
+
+	$network_id = get_main_network_id();
+
+	if ( false === ( $supported = get_network_option( $network_id, 'site_meta_supported', false ) ) ) {
+		$supported = $wpdb->get_var( "SHOW TABLES LIKE '{$wpdb->blogmeta}'" ) ? 1 : 0;
+
+		update_network_option( $network_id, 'site_meta_supported', $supported );
+	}
+
+	return (bool) $supported;
+}
+
+/**
  * gmt_offset modification for smart timezone handling.
  *
  * Overrides the gmt_offset option if we have a timezone_string available.
Index: src/wp-includes/load.php
===================================================================
--- src/wp-includes/load.php	(revision 42444)
+++ src/wp-includes/load.php	(working copy)
@@ -567,7 +567,7 @@
 	}
 
 	if ( function_exists( 'wp_cache_add_global_groups' ) ) {
-		wp_cache_add_global_groups( array( 'users', 'userlogins', 'usermeta', 'user_meta', 'useremail', 'userslugs', 'site-transient', 'site-options', 'blog-lookup', 'blog-details', 'site-details', 'rss', 'global-posts', 'blog-id-cache', 'networks', 'sites' ) );
+		wp_cache_add_global_groups( array( 'users', 'userlogins', 'usermeta', 'user_meta', 'useremail', 'userslugs', 'site-transient', 'site-options', 'blog-lookup', 'blog-details', 'site-details', 'rss', 'global-posts', 'blog-id-cache', 'networks', 'sites', 'blog_meta' ) );
 		wp_cache_add_non_persistent_groups( array( 'counts', 'plugins' ) );
 	}
 }
Index: src/wp-includes/ms-blogs.php
===================================================================
--- src/wp-includes/ms-blogs.php	(revision 42444)
+++ src/wp-includes/ms-blogs.php	(working copy)
@@ -474,6 +474,7 @@
 	wp_cache_delete( $domain_path_key, 'blog-id-cache' );
 	wp_cache_delete( 'current_blog_' . $blog->domain, 'site-options' );
 	wp_cache_delete( 'current_blog_' . $blog->domain . $blog->path, 'site-options' );
+	wp_cache_delete( $blog_id, 'blog_meta' );
 
 	/**
 	 * Fires immediately after a site has been removed from the object cache.
@@ -560,21 +561,23 @@
  * Adds any sites from the given ids to the cache that do not already exist in cache.
  *
  * @since 4.6.0
+ * @since 5.0.0 Introduced the `$update_meta_cache` parameter.
  * @access private
  *
  * @see update_site_cache()
  * @global wpdb $wpdb WordPress database abstraction object.
  *
  * @param array $ids ID list.
+ * @param bool  $update_meta_cache Optional. Whether to update the meta cache. Default true.
  */
-function _prime_site_caches( $ids ) {
+function _prime_site_caches( $ids, $update_meta_cache = true ) {
 	global $wpdb;
 
 	$non_cached_ids = _get_non_cached_ids( $ids, 'sites' );
 	if ( ! empty( $non_cached_ids ) ) {
 		$fresh_sites = $wpdb->get_results( sprintf( "SELECT * FROM $wpdb->blogs WHERE blog_id IN (%s)", join( ',', array_map( 'intval', $non_cached_ids ) ) ) );
 
-		update_site_cache( $fresh_sites );
+		update_site_cache( $fresh_sites, $update_meta_cache );
 	}
 }
 
@@ -582,18 +585,44 @@
  * Updates sites in cache.
  *
  * @since 4.6.0
+ * @since 5.0.0 Introduced the `$update_meta_cache` parameter.
  *
- * @param array $sites Array of site objects.
+ * @param array $sites             Array of site objects.
+ * @param bool  $update_meta_cache Whether to update site meta cache. Default true.
  */
-function update_site_cache( $sites ) {
+function update_site_cache( $sites, $update_meta_cache = true ) {
 	if ( ! $sites ) {
 		return;
 	}
-
+	$site_ids = array();
 	foreach ( $sites as $site ) {
+		$site_ids[] = $site->blog_id;
 		wp_cache_add( $site->blog_id, $site, 'sites' );
 		wp_cache_add( $site->blog_id . 'short', $site, 'blog-details' );
 	}
+
+	if ( $update_meta_cache ) {
+		update_sitemeta_cache( $site_ids );
+	}
+}
+
+/**
+ * Updates metadata cache for list of site IDs.
+ *
+ * Performs SQL query to retrieve all metadata for the sites matching `$site_ids` and stores them in the cache.
+ * Subsequent calls to `get_site_meta()` will not need to query the database.
+ *
+ * @since 5.0.0
+ *
+ * @param array $site_ids List of site IDs.
+ * @return array|false Returns false if there is nothing to update. Returns an array of metadata on success.
+ */
+function update_sitemeta_cache( $site_ids ) {
+	if ( ! is_site_meta_supported() ) {
+		return false;
+	}
+
+	return update_meta_cache( 'blog', $site_ids );
 }
 
 /**
@@ -658,6 +687,7 @@
 	return $query->query( $args );
 }
 
+
 /**
  * Retrieve option value for a given blog id based on name of option.
  *
@@ -796,6 +826,162 @@
 	return $return;
 }
 
+
+
+/**
+ * Add meta data field to a site.
+ *
+ * Site meta data is called "Custom Fields" on the Administration Screen.
+ *
+ * @since 5.0.0
+ *
+ * @param int    $site_id    Site ID.
+ * @param string $meta_key   Metadata name.
+ * @param mixed  $meta_value Metadata value. Must be serializable if non-scalar.
+ * @param bool   $unique     Optional. Whether the same key should not be added.
+ *                           Default false.
+ * @return int|false Meta ID on success, false on failure.
+ */
+function add_site_meta( $site_id, $meta_key, $meta_value, $unique = false ) {
+	// Bail if site meta table is not installed.
+	if ( ! is_site_meta_supported() ) {
+		_doing_it_wrong( __FUNCTION__, __( 'Site meta table is not installed. Please run database upgrade.' ), '5.0.0' );
+
+		return false;
+	}
+
+	$added = add_metadata( 'blog', $site_id, $meta_key, $meta_value, $unique );
+
+	// Bust site query cache.
+	if ( $added ) {
+		// @todo use clean_blog_cache here
+		wp_cache_set( 'last_changed', microtime(), 'sites' );
+	}
+
+	return $added;
+}
+
+/**
+ * Remove metadata matching criteria from a site.
+ *
+ * You can match based on the key, or key and value. Removing based on key and
+ * value, will keep from removing duplicate metadata with the same key. It also
+ * allows removing all metadata matching key, if needed.
+ *
+ * @since 5.0.0
+ *
+ * @param int    $site_id    Site ID.
+ * @param string $meta_key   Metadata name.
+ * @param mixed  $meta_value Optional. Metadata value. Must be serializable if
+ *                           non-scalar. Default empty.
+ * @return bool True on success, false on failure.
+ */
+function delete_site_meta( $site_id, $meta_key, $meta_value = '' ) {
+	// Bail if site meta table is not installed.
+	if ( ! is_site_meta_supported() ) {
+		_doing_it_wrong( __FUNCTION__, __( 'Site meta table is not installed. Please run database upgrade.' ), '5.0.0' );
+
+		return false;
+	}
+
+	$deleted = delete_metadata( 'blog', $site_id, $meta_key, $meta_value );
+
+	// Bust site query cache.
+	if ( $deleted ) {
+		// @todo use clean_blog_cache here
+		wp_cache_set( 'last_changed', microtime(), 'sites' );
+	}
+
+	return $deleted;
+}
+
+/**
+ * Retrieve site meta field for a site.
+ *
+ * @since 5.0.0
+ *
+ * @param int    $site_id Site ID.
+ * @param string $key     Optional. The meta key to retrieve. By default, returns
+ *                        data for all keys. Default empty.
+ * @param bool   $single  Optional. Whether to return a single value. Default false.
+ * @return mixed Will be an array if $single is false. Will be value of meta data
+ *               field if $single is true.
+ */
+function get_site_meta( $site_id, $key = '', $single = false ) {
+	// Bail if site meta table is not installed.
+	if ( ! is_site_meta_supported() ) {
+		_doing_it_wrong( __FUNCTION__, __( 'Site meta table is not installed. Please run database upgrade.' ), '5.0.0' );
+
+		return false;
+	}
+
+	return get_metadata( 'blog', $site_id, $key, $single );
+}
+
+/**
+ * Update site meta field based on site ID.
+ *
+ * Use the $prev_value parameter to differentiate between meta fields with the
+ * same key and site ID.
+ *
+ * If the meta field for the site does not exist, it will be added.
+ *
+ * @since 5.0.0
+ *
+ * @param int    $site_id    Site ID.
+ * @param string $meta_key   Metadata key.
+ * @param mixed  $meta_value Metadata value. Must be serializable if non-scalar.
+ * @param mixed  $prev_value Optional. Previous value to check before removing.
+ *                           Default empty.
+ * @return int|bool Meta ID if the key didn't exist, true on successful update,
+ *                  false on failure.
+ */
+function update_site_meta( $site_id, $meta_key, $meta_value, $prev_value = '' ) {
+	// Bail if site meta table is not installed.
+	if ( ! is_site_meta_supported() ) {
+		_doing_it_wrong( __FUNCTION__, __( 'Site meta table is not installed. Please run database upgrade.' ), '5.0.0' );
+
+		return false;
+	}
+
+	$updated = update_metadata( 'blog', $site_id, $meta_key, $meta_value, $prev_value );
+
+	// Bust site query cache.
+	if ( $updated ) {
+		// @todo use clean_blog_cache here
+		wp_cache_set( 'last_changed', microtime(), 'sites' );
+	}
+
+	return $updated;
+}
+
+/**
+ * Delete everything from site meta matching meta key.
+ *
+ * @since 5.0.0
+ *
+ * @param string $meta_key Metadata key to search for when deleting.
+ * @return bool Whether the site meta key was deleted from the database.
+ */
+function delete_site_meta_by_key( $meta_key ) {
+	// Bail if site meta table is not installed.
+	if ( ! is_site_meta_supported() ) {
+		_doing_it_wrong( __FUNCTION__, __( 'Site meta table is not installed. Please run database upgrade.' ), '5.0.0' );
+
+		return false;
+	}
+
+	$deleted = delete_metadata( 'blog', null, $meta_key, '', true );
+
+	// Bust site query cache.
+	if ( $deleted ) {
+		// @todo use clean_blog_cache here
+		wp_cache_set( 'last_changed', microtime(), 'sites' );
+	}
+
+	return $deleted;
+}
+
 /**
  * Switch the current blog.
  *
@@ -869,7 +1055,7 @@
 			if ( is_array( $global_groups ) ) {
 				wp_cache_add_global_groups( $global_groups );
 			} else {
-				wp_cache_add_global_groups( array( 'users', 'userlogins', 'usermeta', 'user_meta', 'useremail', 'userslugs', 'site-transient', 'site-options', 'blog-lookup', 'blog-details', 'rss', 'global-posts', 'blog-id-cache', 'networks', 'sites', 'site-details' ) );
+				wp_cache_add_global_groups( array( 'users', 'userlogins', 'usermeta', 'user_meta', 'useremail', 'userslugs', 'site-transient', 'site-options', 'blog-lookup', 'blog-details', 'rss', 'global-posts', 'blog-id-cache', 'networks', 'sites', 'site-details', 'blog_meta' ) );
 			}
 			wp_cache_add_non_persistent_groups( array( 'counts', 'plugins' ) );
 		}
@@ -937,7 +1123,7 @@
 			if ( is_array( $global_groups ) ) {
 				wp_cache_add_global_groups( $global_groups );
 			} else {
-				wp_cache_add_global_groups( array( 'users', 'userlogins', 'usermeta', 'user_meta', 'useremail', 'userslugs', 'site-transient', 'site-options', 'blog-lookup', 'blog-details', 'rss', 'global-posts', 'blog-id-cache', 'networks', 'sites', 'site-details' ) );
+				wp_cache_add_global_groups( array( 'users', 'userlogins', 'usermeta', 'user_meta', 'useremail', 'userslugs', 'site-transient', 'site-options', 'blog-lookup', 'blog-details', 'rss', 'global-posts', 'blog-id-cache', 'networks', 'sites', 'site-details', 'blog_meta' ) );
 			}
 			wp_cache_add_non_persistent_groups( array( 'counts', 'plugins' ) );
 		}
Index: src/wp-includes/version.php
===================================================================
--- src/wp-includes/version.php	(revision 42444)
+++ src/wp-includes/version.php	(working copy)
@@ -11,7 +11,7 @@
  *
  * @global int $wp_db_version
  */
-$wp_db_version = 38590;
+$wp_db_version = 42125;
 
 /**
  * Holds the TinyMCE version
Index: src/wp-includes/wp-db.php
===================================================================
--- src/wp-includes/wp-db.php	(revision 42444)
+++ src/wp-includes/wp-db.php	(working copy)
@@ -283,6 +283,7 @@
 	 */
 	var $ms_global_tables = array(
 		'blogs',
+		'blogmeta',
 		'signups',
 		'site',
 		'sitemeta',
@@ -400,6 +401,14 @@
 	public $blogs;
 
 	/**
+	 * Multisite Blog Metadata table
+	 *
+	 * @since 5.0.0
+	 * @var string
+	 */
+	public $blogmeta;
+
+	/**
 	 * Multisite Blog Versions table
 	 *
 	 * @since 3.0.0
Index: src/wp-settings.php
===================================================================
--- src/wp-settings.php	(revision 42444)
+++ src/wp-settings.php	(working copy)
@@ -95,6 +95,8 @@
 // Load early WordPress files.
 require( ABSPATH . WPINC . '/compat.php' );
 require( ABSPATH . WPINC . '/class-wp-list-util.php' );
+require( ABSPATH . WPINC . '/formatting.php' );
+require( ABSPATH . WPINC . '/meta.php' );
 require( ABSPATH . WPINC . '/functions.php' );
 require( ABSPATH . WPINC . '/class-wp-matchesmapregex.php' );
 require( ABSPATH . WPINC . '/class-wp.php' );
@@ -143,7 +145,6 @@
 // Load most of WordPress.
 require( ABSPATH . WPINC . '/class-wp-walker.php' );
 require( ABSPATH . WPINC . '/class-wp-ajax-response.php' );
-require( ABSPATH . WPINC . '/formatting.php' );
 require( ABSPATH . WPINC . '/capabilities.php' );
 require( ABSPATH . WPINC . '/class-wp-roles.php' );
 require( ABSPATH . WPINC . '/class-wp-role.php' );
@@ -158,7 +159,6 @@
 require( ABSPATH . WPINC . '/class-wp-user-query.php' );
 require( ABSPATH . WPINC . '/class-wp-session-tokens.php' );
 require( ABSPATH . WPINC . '/class-wp-user-meta-session-tokens.php' );
-require( ABSPATH . WPINC . '/meta.php' );
 require( ABSPATH . WPINC . '/class-wp-meta-query.php' );
 require( ABSPATH . WPINC . '/class-wp-metadata-lazyloader.php' );
 require( ABSPATH . WPINC . '/general-template.php' );
Index: tests/phpunit/includes/testcase.php
===================================================================
--- tests/phpunit/includes/testcase.php	(revision 42444)
+++ tests/phpunit/includes/testcase.php	(working copy)
@@ -328,7 +328,7 @@
 			$wp_object_cache->__remoteset();
 		}
 		wp_cache_flush();
-		wp_cache_add_global_groups( array( 'users', 'userlogins', 'usermeta', 'user_meta', 'useremail', 'userslugs', 'site-transient', 'site-options', 'blog-lookup', 'blog-details', 'rss', 'global-posts', 'blog-id-cache', 'networks', 'sites', 'site-details' ) );
+		wp_cache_add_global_groups( array( 'users', 'userlogins', 'usermeta', 'user_meta', 'useremail', 'userslugs', 'site-transient', 'site-options', 'blog-lookup', 'blog-details', 'rss', 'global-posts', 'blog-id-cache', 'networks', 'sites', 'site-details', 'blog_meta' ) );
 		wp_cache_add_non_persistent_groups( array( 'comment', 'counts', 'plugins' ) );
 	}
 
Index: tests/phpunit/tests/multisite/siteMeta.php
===================================================================
--- tests/phpunit/tests/multisite/siteMeta.php	(revision 0)
+++ tests/phpunit/tests/multisite/siteMeta.php	(working copy)
@@ -0,0 +1,178 @@
+<?php
+
+if ( is_multisite() ) :
+
+	/**
+	 * @group ms-site
+	 * @group multisite
+	 * @group site-meta
+	 * @group meta
+	 * @ticket 37923
+	 */
+	class Tests_Multisite_Site_Meta extends WP_UnitTestCase {
+		protected static $site_id;
+		protected static $site_id2;
+		protected static $flag_was_set;
+
+		public static function wpSetUpBeforeClass( $factory ) {
+			self::$site_id  = $factory->blog->create( array( 'domain' => 'wordpress.org', 'path' => '/' ) );
+			self::$site_id2 = $factory->blog->create( array( 'domain' => 'wordpress.org', 'path' => '/foo/' ) );
+
+			// Populate the main network flag as necessary.
+			self::$flag_was_set = true;
+			if ( false === get_network_option( get_main_network_id(), 'site_meta_supported', false ) ) {
+				self::$flag_was_set = false;
+				is_site_meta_supported();
+			}
+		}
+
+		public static function wpTearDownAfterClass() {
+			// Delete the possibly previously populated main network flag.
+			if ( ! self::$flag_was_set ) {
+				delete_network_option( get_main_network_id(), 'site_meta_supported' );
+			}
+
+			wpmu_delete_blog( self::$site_id, true );
+			wpmu_delete_blog( self::$site_id2, true );
+
+			wp_update_network_site_counts();
+		}
+
+		public function test_is_site_meta_supported() {
+			$setting = get_network_option( get_main_network_id(), 'site_meta_supported' );
+			$this->assertTrue( is_site_meta_supported() );
+			$this->assertSame( $setting, '1' );
+		}
+
+		public function test_is_site_meta_supported_filtered() {
+			add_filter('pre_site_option_site_meta_supported', '__return_zero');
+			$setting = get_network_option( get_main_network_id(), 'site_meta_supported' );
+			$this->assertFalse( is_site_meta_supported() );
+			$this->assertSame( $setting, 0 );
+			remove_filter('pre_site_option_site_meta_supported', '__return_zero');
+		}
+
+		public function test_add() {
+			$key   = 'foo';
+			$value = 'bar';
+			$this->assertNotEmpty( add_site_meta( self::$site_id, $key, $value ) );
+			$this->assertSame( get_site_meta( self::$site_id, $key, true ), $value );
+		}
+
+		public function test_add_unique() {
+
+			$this->assertNotEmpty( add_site_meta( self::$site_id, 'foo', 'bar' ) );
+			$this->assertFalse( add_site_meta( self::$site_id, 'foo', 'bar', true ) );
+		}
+
+		public function test_delete() {
+
+			add_site_meta( self::$site_id, 'foo', 'bar' );
+
+			$this->assertTrue( delete_site_meta( self::$site_id, 'foo' ) );
+		}
+
+		public function test_delete_with_invalid_meta_key_should_return_false() {
+
+			$this->assertFalse( delete_site_meta( self::$site_id, 'foo' ) );
+		}
+
+		public function test_delete_should_respect_meta_value() {
+
+			add_site_meta( self::$site_id, 'foo', 'bar' );
+			add_site_meta( self::$site_id, 'foo', 'baz' );
+
+			$this->assertTrue( delete_site_meta( self::$site_id, 'foo', 'bar' ) );
+
+			$metas = get_site_meta( self::$site_id, 'foo', false );
+			$this->assertSame( array( 'baz' ), $metas );
+		}
+
+		public function test_get_with_no_key_should_fetch_all_keys() {
+
+			add_site_meta( self::$site_id, 'foo', 'bar' );
+			add_site_meta( self::$site_id, 'foo1', 'baz' );
+
+			$found    = get_site_meta( self::$site_id );
+			$expected = array(
+				'foo'  => array( 'bar' ),
+				'foo1' => array( 'baz' ),
+			);
+
+			$this->assertEqualSets( $expected, $found );
+		}
+
+		public function test_get_with_key_should_fetch_all_for_key() {
+
+			add_site_meta( self::$site_id, 'foo', 'bar' );
+			add_site_meta( self::$site_id, 'foo', 'baz' );
+			add_site_meta( self::$site_id, 'foo1', 'baz' );
+
+			$found    = get_site_meta( self::$site_id, 'foo' );
+			$expected = array( 'bar', 'baz' );
+
+			$this->assertEqualSets( $expected, $found );
+		}
+
+		public function test_get_should_respect_single_true() {
+
+			add_site_meta( self::$site_id, 'foo', 'bar' );
+			add_site_meta( self::$site_id, 'foo', 'baz' );
+
+			$found = get_site_meta( self::$site_id, 'foo', true );
+			$this->assertEquals( 'bar', $found );
+		}
+
+		public function test_update_should_pass_to_add_when_no_value_exists_for_key() {
+
+			$actual = update_site_meta( self::$site_id, 'foo', 'bar' );
+			$this->assertInternalType( 'int', $actual );
+			$this->assertNotEmpty( $actual );
+
+			$meta = get_site_meta( self::$site_id, 'foo', true );
+			$this->assertSame( 'bar', $meta );
+		}
+
+		public function test_update_should_return_true_when_updating_existing_value_for_key() {
+
+			add_site_meta( self::$site_id, 'foo', 'bar' );
+
+			$actual = update_site_meta( self::$site_id, 'foo', 'baz' );
+			$this->assertTrue( $actual );
+
+			$meta = get_site_meta( self::$site_id, 'foo', true );
+			$this->assertSame( 'baz', $meta );
+		}
+
+		public function test_delete_by_key() {
+
+			add_site_meta( self::$site_id, 'unique_delete_by_key', 'value', true );
+			add_site_meta( self::$site_id2, 'unique_delete_by_key', 'value', true );
+
+			$this->assertEquals( 'value', get_site_meta( self::$site_id, 'unique_delete_by_key', true ) );
+			$this->assertEquals( 'value', get_site_meta( self::$site_id2, 'unique_delete_by_key', true ) );
+
+			$this->assertTrue( delete_site_meta_by_key( 'unique_delete_by_key' ) );
+
+			$this->assertEquals( '', get_site_meta( self::$site_id, 'unique_delete_by_key', true ) );
+			$this->assertEquals( '', get_site_meta( self::$site_id2, 'unique_delete_by_key', true ) );
+		}
+
+		public function test_site_meta_should_be_deleted_when_site_is_deleted() {
+
+			$site_id = self::factory()->blog->create( array( 'domain' => 'foo.org', 'path' => '/' ) );
+
+			add_site_meta( $site_id, 'foo', 'bar' );
+			add_site_meta( $site_id, 'foo1', 'bar' );
+
+			$this->assertSame( 'bar', get_site_meta( $site_id, 'foo', true ) );
+			$this->assertSame( 'bar', get_site_meta( $site_id, 'foo1', true ) );
+
+			wpmu_delete_blog( $site_id, true );
+
+			$this->assertSame( '', get_site_meta( $site_id, 'foo', true ) );
+			$this->assertSame( '', get_site_meta( $site_id, 'foo1', true ) );
+		}
+	}
+
+endif;

Property changes on: tests/phpunit/tests/multisite/siteMeta.php
___________________________________________________________________
Added: svn:executable
## -0,0 +1 ##
+*
\ No newline at end of property
