Multisite: Introduce WP_Network_Query.

Provides a consistent way to query `$wpdb->site` for `WP_Network` objects based on domain, path, network ID, and (main) site ID.

Introduces and uses update_network_cache() and _prime_network_caches() to maintain a cached list of WP_Network objects for use in multiple queries.

Props flixos90.
See #32504.


git-svn-id: https://develop.svn.wordpress.org/trunk@37894 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-includes/ms-blogs.php

@@ -1114,6 +1114,69 @@ function get_network( &$network = null ) {
 	return $_network;
 }
 
+/**
+ * Removes a network from the object cache.
+ *
+ * @since 4.6.0
+ *
+ * @param int|array $ids Network ID or an array of network IDs to remove from cache.
+ */
+function clean_network_cache( $ids ) {
+	foreach ( (array) $ids as $id ) {
+		wp_cache_delete( $id, 'networks' );
+
+		/**
+		 * Fires immediately after a network has been removed from the object cache.
+		 *
+		 * @since 4.6.0
+		 *
+		 * @param int $id Network ID.
+		 */
+		do_action( 'clean_network_cache', $id );
+	}
+
+	wp_cache_set( 'last_changed', microtime(), 'networks' );
+}
+
+/**
+ * Updates the network cache of given networks.
+ *
+ * Will add the networks in $networks to the cache. If network ID already exists
+ * in the network cache then it will not be updated. The network is added to the
+ * cache using the network group with the key using the ID of the networks.
+ *
+ * @since 4.6.0
+ *
+ * @param array $networks Array of network row objects.
+ */
+function update_network_cache( $networks ) {
+	foreach ( (array) $networks as $network ) {
+		wp_cache_add( $network->id, $network, 'networks' );
+	}
+}
+
+/**
+ * Adds any networks from the given IDs to the cache that do not already exist in cache.
+ *
+ * @since 4.6.0
+ * @access private
+ *
+ * @see update_network_cache()
+ * @global wpdb $wpdb WordPress database abstraction object.
+ *
+ * @param array $network_ids Array of network IDs.
+ */
+function _prime_network_caches( $network_ids ) {
+	global $wpdb;
+
+	$non_cached_ids = _get_non_cached_ids( $network_ids, 'networks' );
+	if ( !empty( $non_cached_ids ) ) {
+		$fresh_networks = $wpdb->get_results( sprintf( "SELECT $wpdb->site.* FROM $wpdb->site WHERE id IN (%s)", join( ",", array_map( 'intval', $non_cached_ids ) ) ) );
+
+		update_network_cache( $fresh_networks );
+	}
+}
+
 /**
  * Handler for updating the blog date when a post is published or an already published post is changed.
  *