Move all database code in a single file

db-backends.php

 <?php
 
-function noblogs_load_backends($hashptr) {
+require_once(dirname(__FILE__) . '/flexihash.php');
+require_once(ABSPATH . 'wp-config.php');
+
+$r2db_hash_map = new Flexihash(null, R2DB_FLEXIHASH_REPLICAS);
+
+/* Hashing function to map blogs to databases.
+ *
+ * Implements a consistent hashing scheme using Flexihash.
+ */
+function noblogs_db_callback($query, $wpdb) {
+  global $r2db_hash_map;
+  if (preg_match("/^{$wpdb->base_prefix}(\d+)_/", $wpdb->table, $matches)) {
+    $blog_id = $matches[1];
+    return $r2db_hash_map->lookup($blog_id);
+  }
+}
+
+$wpdb->add_callback('noblogs_db_callback');
+
+/* Load backend shards and add them to FlexiHash / $wpdb. */
+function noblogs_load_backends() {
   global $wpdb;
+  global $r2db_hash_map;
   global $noblogs_config;
   $backend_map = array();
   foreach ($noblogs_config['db_config']['backends'] as $backend_name => $backend) {
@@ -16,12 +37,13 @@ function noblogs_load_backends($hashptr) {
        "timeout" => 10
     );
     $wpdb->add_database($b);
-    $hashptr->addTarget($backend_name);
+    $r2db_hash_map->addTarget($backend_name);
     $backend_map[$backend_name] = $b;
   }
   return $backend_map;
 }
 
+/* Load the local and master backends to $wpdb. */
 function noblogs_load_global_dataset() {
   global $wpdb;
   global $noblogs_config;

db-config.php

@@ -8,11 +8,10 @@ $wpdb->max_connections = 30;
  connection errors for the wrong implementation */
 $wpdb->check_tcp_responsiveness = false;
 
-include_once('r2db/db-hash.php');
 include_once('r2db/db-backends.php');
 
 // Set up global dataset with master databases
 noblogs_load_global_dataset();
 
 // Add all the sharded blog databases.
-$wpdb_reverse_backend_map = noblogs_load_backends($r2db_hash_map);
+$wpdb_reverse_backend_map = noblogs_load_backends();

db-hash.php

-<?php
-
-require_once(dirname(__FILE__) . '/flexihash.php');
-require_once( ABSPATH . 'wp-config.php' );
-
-$r2db_hash_map = new Flexihash(null, R2DB_FLEXIHASH_REPLICAS);
-
-/* Hashing function to map blogs to databases.
- *
- * Implements a consistent hashing scheme using Flexihash.
- */
-function noblogs_db_callback($query, $wpdb) {
-  global $r2db_hash_map;
-  if (preg_match("/^{$wpdb->base_prefix}(\d+)_/", $wpdb->table, $matches)) {
-    $blog_id = $matches[1];
-    return $r2db_hash_map->lookup($blog_id);
-  }
-}
-$wpdb->add_callback('noblogs_db_callback');