cms/drupal/includes/update.inc
changeset 541 e756a8c72c3d
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/cms/drupal/includes/update.inc	Fri Sep 08 12:04:06 2017 +0200
@@ -0,0 +1,1489 @@
+<?php
+
+/**
+ * @file
+ * Drupal database update API.
+ *
+ * This file contains functions to perform database updates for a Drupal
+ * installation. It is included and used extensively by update.php.
+ */
+
+/**
+ * Minimum schema version of Drupal 6 required for upgrade to Drupal 7.
+ *
+ * Upgrades from Drupal 6 to Drupal 7 require that Drupal 6 be running
+ * the most recent version, or the upgrade could fail. We can't easily
+ * check the Drupal 6 version once the update process has begun, so instead
+ * we check the schema version of system.module in the system table.
+ */
+define('REQUIRED_D6_SCHEMA_VERSION', '6055');
+
+/**
+ * Disable any items in the {system} table that are not core compatible.
+ */
+function update_fix_compatibility() {
+  $incompatible = array();
+  $result = db_query("SELECT name, type, status FROM {system} WHERE status = 1 AND type IN ('module','theme')");
+  foreach ($result as $row) {
+    if (update_check_incompatibility($row->name, $row->type)) {
+      $incompatible[] = $row->name;
+    }
+  }
+  if (!empty($incompatible)) {
+    db_update('system')
+      ->fields(array('status' => 0))
+      ->condition('name', $incompatible, 'IN')
+      ->execute();
+  }
+}
+
+/**
+ * Tests the compatibility of a module or theme.
+ */
+function update_check_incompatibility($name, $type = 'module') {
+  static $themes, $modules;
+
+  // Store values of expensive functions for future use.
+  if (empty($themes) || empty($modules)) {
+    // We need to do a full rebuild here to make sure the database reflects any
+    // code changes that were made in the filesystem before the update script
+    // was initiated.
+    $themes = system_rebuild_theme_data();
+    $modules = system_rebuild_module_data();
+  }
+
+  if ($type == 'module' && isset($modules[$name])) {
+    $file = $modules[$name];
+  }
+  elseif ($type == 'theme' && isset($themes[$name])) {
+    $file = $themes[$name];
+  }
+  if (!isset($file)
+      || !isset($file->info['core'])
+      || $file->info['core'] != DRUPAL_CORE_COMPATIBILITY
+      || version_compare(phpversion(), $file->info['php']) < 0) {
+    return TRUE;
+  }
+  return FALSE;
+}
+
+/**
+ * Performs extra steps required to bootstrap when using a Drupal 6 database.
+ *
+ * Users who still have a Drupal 6 database (and are in the process of
+ * updating to Drupal 7) need extra help before a full bootstrap can be
+ * achieved. This function does the necessary preliminary work that allows
+ * the bootstrap to be successful.
+ *
+ * No access check has been performed when this function is called, so no
+ * irreversible changes to the database are made here.
+ */
+function update_prepare_d7_bootstrap() {
+  // Allow the bootstrap to proceed even if a Drupal 6 settings.php file is
+  // still being used.
+  include_once DRUPAL_ROOT . '/includes/install.inc';
+  drupal_bootstrap(DRUPAL_BOOTSTRAP_CONFIGURATION);
+  global $databases, $db_url, $db_prefix, $update_rewrite_settings;
+  if (empty($databases) && !empty($db_url)) {
+    $databases = update_parse_db_url($db_url, $db_prefix);
+    // Record the fact that the settings.php file will need to be rewritten.
+    $update_rewrite_settings = TRUE;
+    $settings_file = conf_path() . '/settings.php';
+    $writable = drupal_verify_install_file($settings_file, FILE_EXIST|FILE_READABLE|FILE_WRITABLE);
+    $requirements = array(
+      'settings file' => array(
+        'title' => 'Settings file',
+        'value' => $writable ? 'The settings file is writable.' : 'The settings file is not writable.',
+        'severity' => $writable ? REQUIREMENT_OK : REQUIREMENT_ERROR,
+        'description' => $writable ? '' : 'Drupal requires write permissions to <em>' . $settings_file . '</em> during the update process. If you are unsure how to grant file permissions, consult the <a href="http://drupal.org/server-permissions">online handbook</a>.',
+      ),
+    );
+    update_extra_requirements($requirements);
+  }
+
+  // The new {blocked_ips} table is used in Drupal 7 to store a list of
+  // banned IP addresses. If this table doesn't exist then we are still
+  // running on a Drupal 6 database, so we suppress the unavoidable errors
+  // that occur by creating a static list.
+  $GLOBALS['conf']['blocked_ips'] = array();
+
+  // Check that PDO is available and that the correct PDO database driver is
+  // loaded. Bootstrapping to DRUPAL_BOOTSTRAP_DATABASE will result in a fatal
+  // error otherwise.
+  $message = '';
+  $pdo_link = 'http://drupal.org/requirements/pdo';
+  // Check that PDO is loaded.
+  if (!extension_loaded('pdo')) {
+    $message = '<h2>PDO is required!</h2><p>Drupal 7 requires PHP ' . DRUPAL_MINIMUM_PHP . ' or higher with the PHP Data Objects (PDO) extension enabled.</p>';
+  }
+  // The PDO::ATTR_DEFAULT_FETCH_MODE constant is not available in the PECL
+  // version of PDO.
+  elseif (!defined('PDO::ATTR_DEFAULT_FETCH_MODE')) {
+    $message = '<h2>The wrong version of PDO is installed!</h2><p>Drupal 7 requires the PHP Data Objects (PDO) extension from PHP core to be enabled. This system has the older PECL version installed.';
+    $pdo_link = 'http://drupal.org/requirements/pdo#pecl';
+  }
+  // Check that the correct driver is loaded for the database being updated.
+  // If we have no driver information (for example, if someone tried to create
+  // the Drupal 7 $databases array themselves but did not do it correctly),
+  // this message will be confusing, so do not perform the check; instead, just
+  // let the database connection fail in the code that follows.
+  elseif (isset($databases['default']['default']['driver']) && !in_array($databases['default']['default']['driver'], PDO::getAvailableDrivers())) {
+    $message = '<h2>A PDO database driver is required!</h2><p>You need to enable the PDO_' . strtoupper($databases['default']['default']['driver']) . ' database driver for PHP ' . DRUPAL_MINIMUM_PHP . ' or higher so that Drupal 7 can access the database.</p>';
+  }
+  if ($message) {
+    print $message . '<p>See the <a href="' . $pdo_link . '">system requirements page</a> for more information.</p>';
+    exit();
+  }
+
+  // Allow the database system to work even if the registry has not been
+  // created yet.
+  drupal_bootstrap(DRUPAL_BOOTSTRAP_DATABASE);
+
+  // If the site has not updated to Drupal 7 yet, check to make sure that it is
+  // running an up-to-date version of Drupal 6 before proceeding. Note this has
+  // to happen AFTER the database bootstraps because of
+  // drupal_get_installed_schema_version().
+  $system_schema = drupal_get_installed_schema_version('system');
+  if ($system_schema < 7000) {
+    $has_required_schema = $system_schema >= REQUIRED_D6_SCHEMA_VERSION;
+    $requirements = array(
+      'drupal 6 version' => array(
+        'title' => 'Drupal 6 version',
+        'value' => $has_required_schema ? 'You are running a current version of Drupal 6.' : 'You are not running a current version of Drupal 6',
+        'severity' => $has_required_schema ? REQUIREMENT_OK : REQUIREMENT_ERROR,
+        'description' => $has_required_schema ? '' : 'Please update your Drupal 6 installation to the most recent version before attempting to upgrade to Drupal 7',
+      ),
+    );
+
+    // Make sure that the database environment is properly set up.
+    try {
+      db_run_tasks(db_driver());
+    }
+    catch (DatabaseTaskException $e) {
+      $requirements['database tasks'] = array(
+        'title' => 'Database environment',
+        'value' => 'There is a problem with your database environment',
+        'severity' => REQUIREMENT_ERROR,
+        'description' => $e->getMessage(),
+      );
+    }
+
+    update_extra_requirements($requirements);
+
+    // Allow a D6 session to work, since the upgrade has not been performed yet.
+    $d6_session_name = update_get_d6_session_name();
+    if (!empty($_COOKIE[$d6_session_name])) {
+      // Set the current sid to the one found in the D6 cookie.
+      $sid = $_COOKIE[$d6_session_name];
+      $_COOKIE[session_name()] = $sid;
+      session_id($sid);
+    }
+
+    // Upgrading from D6 to D7.{0,1,2,3,4,8,...} is different than upgrading
+    // from D6 to D7.{5,6,7} which should be considered broken. To be able to
+    // properly handle this difference in node_update_7012 we need to keep track
+    // of whether a D6 > D7 upgrade or a D7 > D7 update is running.
+    // Since variable_set() is not available here, the D6 status is being saved
+    // in a local variable to be able to store it later.
+    $update_d6 = TRUE;
+  }
+
+  // Create the registry tables.
+  if (!db_table_exists('registry')) {
+    $schema['registry'] = array(
+      'fields' => array(
+        'name'   => array('type' => 'varchar', 'length' => 255, 'not null' => TRUE, 'default' => ''),
+        'type'   => array('type' => 'varchar', 'length' => 9, 'not null' => TRUE, 'default' => ''),
+        'filename'   => array('type' => 'varchar', 'length' => 255, 'not null' => TRUE, 'default' => ''),
+        'module'   => array('type' => 'varchar', 'length' => 255, 'not null' => TRUE, 'default' => ''),
+        'weight'   => array('type' => 'int', 'not null' => TRUE, 'default' => 0),
+      ),
+      'primary key' => array('name', 'type'),
+      'indexes' => array(
+        'hook' => array('type', 'weight', 'module'),
+      ),
+    );
+    db_create_table('registry', $schema['registry']);
+  }
+  if (!db_table_exists('registry_file')) {
+    $schema['registry_file'] = array(
+      'fields' => array(
+        'filename'   => array('type' => 'varchar', 'length' => 255, 'not null' => TRUE),
+        'hash'   => array('type' => 'varchar', 'length' => 64, 'not null' => TRUE),
+      ),
+      'primary key' => array('filename'),
+    );
+    db_create_table('registry_file', $schema['registry_file']);
+  }
+
+  // Older versions of Drupal 6 do not include the semaphore table, which is
+  // required to bootstrap, so we add it now so that we can bootstrap and
+  // provide a reasonable error message.
+  if (!db_table_exists('semaphore')) {
+    $semaphore = array(
+      'description' => 'Table for holding semaphores, locks, flags, etc. that cannot be stored as Drupal variables since they must not be cached.',
+      'fields' => array(
+        'name' => array(
+          'description' => 'Primary Key: Unique name.',
+          'type' => 'varchar',
+          'length' => 255,
+          'not null' => TRUE,
+          'default' => ''
+        ),
+        'value' => array(
+          'description' => 'A value for the semaphore.',
+          'type' => 'varchar',
+          'length' => 255,
+          'not null' => TRUE,
+          'default' => ''
+        ),
+        'expire' => array(
+          'description' => 'A Unix timestamp with microseconds indicating when the semaphore should expire.',
+          'type' => 'float',
+          'size' => 'big',
+          'not null' => TRUE
+        ),
+      ),
+      'indexes' => array(
+        'value' => array('value'),
+        'expire' => array('expire'),
+      ),
+      'primary key' => array('name'),
+    );
+    db_create_table('semaphore', $semaphore);
+  }
+
+  // The new cache_bootstrap bin is required to bootstrap to
+  // DRUPAL_BOOTSTRAP_SESSION, so create it here rather than in
+  // update_fix_d7_requirements().
+  if (!db_table_exists('cache_bootstrap')) {
+    $cache_bootstrap = array(
+      'description' => 'Cache table for data required to bootstrap Drupal, may be routed to a shared memory cache.',
+      'fields' => array(
+        'cid' => array(
+          'description' => 'Primary Key: Unique cache ID.',
+          'type' => 'varchar',
+          'length' => 255,
+          'not null' => TRUE,
+          'default' => '',
+        ),
+        'data' => array(
+          'description' => 'A collection of data to cache.',
+          'type' => 'blob',
+          'not null' => FALSE,
+          'size' => 'big',
+        ),
+        'expire' => array(
+          'description' => 'A Unix timestamp indicating when the cache entry should expire, or 0 for never.',
+          'type' => 'int',
+          'not null' => TRUE,
+          'default' => 0,
+        ),
+        'created' => array(
+          'description' => 'A Unix timestamp indicating when the cache entry was created.',
+          'type' => 'int',
+          'not null' => TRUE,
+          'default' => 0,
+        ),
+        'serialized' => array(
+          'description' => 'A flag to indicate whether content is serialized (1) or not (0).',
+          'type' => 'int',
+          'size' => 'small',
+          'not null' => TRUE,
+          'default' => 0,
+        ),
+      ),
+      'indexes' => array(
+        'expire' => array('expire'),
+      ),
+      'primary key' => array('cid'),
+    );
+    db_create_table('cache_bootstrap', $cache_bootstrap);
+  }
+
+  // Set a valid timezone for 6 -> 7 upgrade process.
+  drupal_bootstrap(DRUPAL_BOOTSTRAP_VARIABLES);
+  $timezone_offset = variable_get('date_default_timezone', 0);
+  if (is_numeric($timezone_offset)) {
+    // Save the original offset.
+    variable_set('date_temporary_timezone', $timezone_offset);
+    // Set the timezone for this request only.
+    $GLOBALS['conf']['date_default_timezone'] = 'UTC';
+  }
+
+  // This allows update functions to tell if an upgrade from D6 is running.
+  if (!empty($update_d6)) {
+    variable_set('update_d6', TRUE);
+  }
+}
+
+/**
+ * A helper function that modules can use to assist with the transformation
+ * from numeric block deltas to string block deltas during the 6.x -> 7.x
+ * upgrade.
+ *
+ * @todo This function should be removed in 8.x.
+ *
+ * @param $sandbox
+ *   An array holding data for the batch process.
+ * @param $renamed_deltas
+ *   An associative array.  Keys are module names, values an associative array
+ *   mapping the old block deltas to the new block deltas for the module.
+ *   Example:
+ *   @code
+ *     $renamed_deltas = array(
+ *       'mymodule' =>
+ *         array(
+ *           0 => 'mymodule-block-1',
+ *           1 => 'mymodule-block-2',
+ *         ),
+ *     );
+ *   @endcode
+ * @param $moved_deltas
+ *   An associative array. Keys are source module names, values an associative
+ *   array mapping the (possibly renamed) block name to the new module name.
+ *   Example:
+ *   @code
+ *     $moved_deltas = array(
+ *       'user' =>
+ *         array(
+ *           'navigation' => 'system',
+ *         ),
+ *     );
+ *   @endcode
+ */
+function update_fix_d7_block_deltas(&$sandbox, $renamed_deltas, $moved_deltas) {
+  // Loop through each block and make changes to the block tables.
+  // Only run this the first time through the batch update.
+  if (!isset($sandbox['progress'])) {
+    // Determine whether to use the old or new block table names.
+    $block_tables = db_table_exists('blocks') ? array('blocks', 'blocks_roles') : array('block', 'block_role');
+    foreach ($block_tables as $table) {
+      foreach ($renamed_deltas as $module => $deltas) {
+        foreach ($deltas as $old_delta => $new_delta) {
+          // Only do the update if the old block actually exists.
+          $block_exists = db_query("SELECT COUNT(*) FROM {" . $table . "} WHERE module = :module AND delta = :delta", array(
+              ':module' => $module,
+              ':delta' => $old_delta,
+            ))
+            ->fetchField();
+          if ($block_exists) {
+            // Delete any existing blocks with the new module+delta.
+            db_delete($table)
+              ->condition('module', $module)
+              ->condition('delta', $new_delta)
+              ->execute();
+            // Rename the old block to the new module+delta.
+            db_update($table)
+              ->fields(array('delta' => $new_delta))
+              ->condition('module', $module)
+              ->condition('delta', $old_delta)
+              ->execute();
+          }
+        }
+      }
+      foreach ($moved_deltas as $old_module => $deltas) {
+        foreach ($deltas as $delta => $new_module) {
+          // Only do the update if the old block actually exists.
+          $block_exists = db_query("SELECT COUNT(*) FROM {" . $table . "} WHERE module = :module AND delta = :delta", array(
+              ':module' => $old_module,
+              ':delta' => $delta,
+            ))
+            ->fetchField();
+          if ($block_exists) {
+            // Delete any existing blocks with the new module+delta.
+            db_delete($table)
+              ->condition('module', $new_module)
+              ->condition('delta', $delta)
+              ->execute();
+            // Rename the old block to the new module+delta.
+            db_update($table)
+              ->fields(array('module' => $new_module))
+              ->condition('module', $old_module)
+              ->condition('delta', $delta)
+              ->execute();
+          }
+        }
+      }
+    }
+
+    // Initialize batch update information.
+    $sandbox['progress'] = 0;
+    $sandbox['last_user_processed'] = -1;
+    $sandbox['max'] = db_query("SELECT COUNT(*) FROM {users} WHERE data LIKE :block", array(
+        ':block' => '%' . db_like(serialize('block')) . '%',
+      ))
+      ->fetchField();
+  }
+  // Now do the batch update of the user-specific block visibility settings.
+  $limit = 100;
+  $result = db_select('users', 'u')
+    ->fields('u', array('uid', 'data'))
+    ->condition('uid', $sandbox['last_user_processed'], '>')
+    ->condition('data', '%' . db_like(serialize('block')) . '%', 'LIKE')
+    ->orderBy('uid', 'ASC')
+    ->range(0, $limit)
+    ->execute();
+  foreach ($result as $row) {
+    $data = unserialize($row->data);
+    $user_needs_update = FALSE;
+    foreach ($renamed_deltas as $module => $deltas) {
+      foreach ($deltas as $old_delta => $new_delta) {
+        if (isset($data['block'][$module][$old_delta])) {
+          // Transfer the old block visibility settings to the newly-renamed
+          // block, and mark this user for a database update.
+          $data['block'][$module][$new_delta] = $data['block'][$module][$old_delta];
+          unset($data['block'][$module][$old_delta]);
+          $user_needs_update = TRUE;
+        }
+      }
+    }
+    foreach ($moved_deltas as $old_module => $deltas) {
+      foreach ($deltas as $delta => $new_module) {
+        if (isset($data['block'][$old_module][$delta])) {
+          // Transfer the old block visibility settings to the moved
+          // block, and mark this user for a database update.
+          $data['block'][$new_module][$delta] = $data['block'][$old_module][$delta];
+          unset($data['block'][$old_module][$delta]);
+          $user_needs_update = TRUE;
+        }
+      }
+    }
+    // Update the current user.
+    if ($user_needs_update) {
+      db_update('users')
+        ->fields(array('data' => serialize($data)))
+        ->condition('uid', $row->uid)
+        ->execute();
+    }
+    // Update our progress information for the batch update.
+    $sandbox['progress']++;
+    $sandbox['last_user_processed'] = $row->uid;
+  }
+  // Indicate our current progress to the batch update system.
+  if ($sandbox['progress'] < $sandbox['max']) {
+    $sandbox['#finished'] = $sandbox['progress'] / $sandbox['max'];
+  }
+}
+
+/**
+ * Perform Drupal 6.x to 7.x updates that are required for update.php
+ * to function properly.
+ *
+ * This function runs when update.php is run the first time for 7.x,
+ * even before updates are selected or performed. It is important
+ * that if updates are not ultimately performed that no changes are
+ * made which make it impossible to continue using the prior version.
+ */
+function update_fix_d7_requirements() {
+  global $conf;
+
+  // Rewrite the settings.php file if necessary, see
+  // update_prepare_d7_bootstrap().
+  global $update_rewrite_settings, $db_url, $db_prefix;
+  if (!empty($update_rewrite_settings)) {
+    $databases = update_parse_db_url($db_url, $db_prefix);
+    $salt = drupal_hash_base64(drupal_random_bytes(55));
+    file_put_contents(conf_path() . '/settings.php', "\n" . '$databases = ' . var_export($databases, TRUE) . ";\n\$drupal_hash_salt = '$salt';", FILE_APPEND);
+  }
+  if (drupal_get_installed_schema_version('system') < 7000 && !variable_get('update_d7_requirements', FALSE)) {
+    // Change 6.x system table field values to 7.x equivalent.
+    // Change field values.
+    db_change_field('system', 'schema_version', 'schema_version', array(
+     'type' => 'int',
+     'size' => 'small',
+     'not null' => TRUE,
+     'default' => -1)
+    );
+    db_change_field('system', 'status', 'status', array(
+      'type' => 'int', 'not null' => TRUE, 'default' => 0));
+    db_change_field('system', 'weight', 'weight', array(
+      'type' => 'int', 'not null' => TRUE, 'default' => 0));
+    db_change_field('system', 'bootstrap', 'bootstrap', array(
+      'type' => 'int', 'not null' => TRUE, 'default' => 0));
+    // Drop and recreate 6.x indexes.
+    db_drop_index('system', 'bootstrap');
+    db_add_index('system', 'bootstrap', array(
+      'status', 'bootstrap', array('type', 12), 'weight', 'name'));
+
+    db_drop_index('system' ,'modules');
+    db_add_index('system', 'modules', array(array(
+      'type', 12), 'status', 'weight', 'name'));
+
+    db_drop_index('system', 'type_name');
+    db_add_index('system', 'type_name', array(array('type', 12), 'name'));
+    // Add 7.x indexes.
+    db_add_index('system', 'system_list', array('weight', 'name'));
+
+    // Add the cache_path table.
+    if (db_table_exists('cache_path')) {
+      db_drop_table('cache_path');
+    }
+    require_once('./modules/system/system.install');
+    $schema['cache_path'] = system_schema_cache_7054();
+    $schema['cache_path']['description'] = 'Cache table used for path alias lookups.';
+    db_create_table('cache_path', $schema['cache_path']);
+
+    // system_update_7042() renames columns, but these are needed to bootstrap.
+    // Add empty columns for now.
+    db_add_field('url_alias', 'source', array('type' => 'varchar', 'length' => 255, 'not null' => TRUE, 'default' => ''));
+    db_add_field('url_alias', 'alias', array('type' => 'varchar', 'length' => 255, 'not null' => TRUE, 'default' => ''));
+
+    // Add new columns to {menu_router}.
+    db_add_field('menu_router', 'delivery_callback', array('type' => 'varchar', 'length' => 255, 'not null' => TRUE, 'default' => ''));
+    db_add_field('menu_router', 'context', array(
+      'description' => 'Only for local tasks (tabs) - the context of a local task to control its placement.',
+      'type' => 'int',
+      'not null' => TRUE,
+      'default' => 0,
+    ));
+    db_drop_index('menu_router', 'tab_parent');
+    db_add_index('menu_router', 'tab_parent', array(array('tab_parent', 64), 'weight', 'title'));
+    db_add_field('menu_router', 'theme_callback', array('type' => 'varchar', 'length' => 255, 'not null' => TRUE, 'default' => ''));
+    db_add_field('menu_router', 'theme_arguments', array('type' => 'varchar', 'length' => 255, 'not null' => TRUE, 'default' => ''));
+
+    // Add the role_permission table.
+    $schema['role_permission'] = array(
+      'fields' => array(
+        'rid' => array(
+        'type' => 'int',
+        'unsigned' => TRUE,
+        'not null' => TRUE,
+      ),
+      'permission' => array(
+        'type' => 'varchar',
+        'length' => 128,
+        'not null' => TRUE,
+        'default' => '',
+      ),
+    ),
+    'primary key' => array('rid', 'permission'),
+    'indexes' => array(
+      'permission' => array('permission'),
+      ),
+    );
+    db_create_table('role_permission', $schema['role_permission']);
+
+    // Drops and recreates semaphore value index.
+    db_drop_index('semaphore', 'value');
+    db_add_index('semaphore', 'value', array('value'));
+
+    $schema['date_format_type'] = array(
+      'description' => 'Stores configured date format types.',
+      'fields' => array(
+        'type' => array(
+          'description' => 'The date format type, e.g. medium.',
+          'type' => 'varchar',
+          'length' => 64,
+          'not null' => TRUE,
+        ),
+        'title' => array(
+          'description' => 'The human readable name of the format type.',
+          'type' => 'varchar',
+          'length' => 255,
+          'not null' => TRUE,
+        ),
+        'locked' => array(
+          'description' => 'Whether or not this is a system provided format.',
+          'type' => 'int',
+          'size' => 'tiny',
+          'default' => 0,
+          'not null' => TRUE,
+        ),
+      ),
+      'primary key' => array('type'),
+    );
+
+    $schema['date_formats'] = array(
+      'description' => 'Stores configured date formats.',
+      'fields' => array(
+        'dfid' => array(
+          'description' => 'The date format identifier.',
+          'type' => 'serial',
+          'not null' => TRUE,
+          'unsigned' => TRUE,
+        ),
+        'format' => array(
+          'description' => 'The date format string.',
+          'type' => 'varchar',
+          'length' => 100,
+          'not null' => TRUE,
+        ),
+        'type' => array(
+          'description' => 'The date format type, e.g. medium.',
+          'type' => 'varchar',
+          'length' => 64,
+          'not null' => TRUE,
+        ),
+        'locked' => array(
+          'description' => 'Whether or not this format can be modified.',
+          'type' => 'int',
+          'size' => 'tiny',
+          'default' => 0,
+          'not null' => TRUE,
+        ),
+      ),
+      'primary key' => array('dfid'),
+      'unique keys' => array('formats' => array('format', 'type')),
+    );
+
+    $schema['date_format_locale'] = array(
+      'description' => 'Stores configured date formats for each locale.',
+      'fields' => array(
+        'format' => array(
+          'description' => 'The date format string.',
+          'type' => 'varchar',
+          'length' => 100,
+          'not null' => TRUE,
+        ),
+        'type' => array(
+          'description' => 'The date format type, e.g. medium.',
+          'type' => 'varchar',
+          'length' => 64,
+          'not null' => TRUE,
+        ),
+        'language' => array(
+          'description' => 'A {languages}.language for this format to be used with.',
+          'type' => 'varchar',
+          'length' => 12,
+          'not null' => TRUE,
+        ),
+      ),
+      'primary key' => array('type', 'language'),
+    );
+
+    db_create_table('date_format_type', $schema['date_format_type']);
+    // Sites that have the Drupal 6 Date module installed already have the
+    // following tables.
+    if (db_table_exists('date_formats')) {
+      db_rename_table('date_formats', 'd6_date_formats');
+    }
+    db_create_table('date_formats', $schema['date_formats']);
+    if (db_table_exists('date_format_locale')) {
+      db_rename_table('date_format_locale', 'd6_date_format_locale');
+    }
+    db_create_table('date_format_locale', $schema['date_format_locale']);
+
+    // Add the queue table.
+    $schema['queue'] = array(
+      'description' => 'Stores items in queues.',
+      'fields' => array(
+        'item_id' => array(
+          'type' => 'serial',
+          'unsigned' => TRUE,
+          'not null' => TRUE,
+          'description' => 'Primary Key: Unique item ID.',
+        ),
+        'name' => array(
+          'type' => 'varchar',
+          'length' => 255,
+          'not null' => TRUE,
+          'default' => '',
+          'description' => 'The queue name.',
+        ),
+        'data' => array(
+          'type' => 'blob',
+          'not null' => FALSE,
+          'size' => 'big',
+          'serialize' => TRUE,
+          'description' => 'The arbitrary data for the item.',
+        ),
+        'expire' => array(
+          'type' => 'int',
+          'not null' => TRUE,
+          'default' => 0,
+          'description' => 'Timestamp when the claim lease expires on the item.',
+        ),
+        'created' => array(
+          'type' => 'int',
+          'not null' => TRUE,
+          'default' => 0,
+          'description' => 'Timestamp when the item was created.',
+        ),
+      ),
+      'primary key' => array('item_id'),
+      'indexes' => array(
+        'name_created' => array('name', 'created'),
+        'expire' => array('expire'),
+      ),
+    );
+    // Check for queue table that may remain from D5 or D6, if found
+    //drop it.
+    if (db_table_exists('queue')) {
+      db_drop_table('queue');
+    }
+
+    db_create_table('queue', $schema['queue']);
+
+    // Create the sequences table.
+    $schema['sequences'] = array(
+      'description' => 'Stores IDs.',
+      'fields' => array(
+        'value' => array(
+          'description' => 'The value of the sequence.',
+          'type' => 'serial',
+          'unsigned' => TRUE,
+          'not null' => TRUE,
+        ),
+       ),
+      'primary key' => array('value'),
+    );
+    // Check for sequences table that may remain from D5 or D6, if found
+    //drop it.
+    if (db_table_exists('sequences')) {
+      db_drop_table('sequences');
+    }
+    db_create_table('sequences', $schema['sequences']);
+    // Initialize the table with the maximum current increment of the tables
+    // that will rely on it for their ids.
+    $max_aid = db_query('SELECT MAX(aid) FROM {actions_aid}')->fetchField();
+    $max_uid = db_query('SELECT MAX(uid) FROM {users}')->fetchField();
+    $max_batch_id = db_query('SELECT MAX(bid) FROM {batch}')->fetchField();
+    db_insert('sequences')->fields(array('value' => max($max_aid, $max_uid, $max_batch_id)))->execute();
+
+    // Add column for locale context.
+    if (db_table_exists('locales_source')) {
+      db_add_field('locales_source', 'context', array('type' => 'varchar', 'length' => 255, 'not null' => TRUE, 'default' => '', 'description' => 'The context this string applies to.'));
+    }
+
+    // Rename 'site_offline_message' variable to 'maintenance_mode_message'
+    // and 'site_offline' variable to 'maintenance_mode'.
+    // Old variable is removed in update for system.module, see
+    // system_update_7072().
+    if ($message = variable_get('site_offline_message', NULL)) {
+      variable_set('maintenance_mode_message', $message);
+    }
+    // Old variable is removed in update for system.module, see
+    // system_update_7069().
+    $site_offline = variable_get('site_offline', -1);
+    if ($site_offline != -1) {
+      variable_set('maintenance_mode', $site_offline);
+    }
+
+    // Add ssid column and index.
+    db_add_field('sessions', 'ssid', array('description' => "Secure session ID. The value is generated by Drupal's session handlers.", 'type' => 'varchar', 'length' => 128, 'not null' => TRUE, 'default' => ''));
+    db_add_index('sessions', 'ssid', array('ssid'));
+    // Drop existing primary key.
+    db_drop_primary_key('sessions');
+    // Add new primary key.
+    db_add_primary_key('sessions', array('sid', 'ssid'));
+
+    // Allow longer javascript file names.
+    if (db_table_exists('languages')) {
+      db_change_field('languages', 'javascript', 'javascript', array('type' => 'varchar', 'length' => 64, 'not null' => TRUE, 'default' => ''));
+    }
+
+    // Rename action description to label.
+    db_change_field('actions', 'description', 'label', array('type' => 'varchar', 'length' => 255, 'not null' => TRUE, 'default' => '0'));
+
+    variable_set('update_d7_requirements', TRUE);
+  }
+
+  update_fix_d7_install_profile();
+}
+
+/**
+ * Register the currently installed profile in the system table.
+ *
+ * Installation profiles are now treated as modules by Drupal, and have an
+ * upgrade path based on their schema version in the system table.
+ *
+ * The installation profile will be set to schema_version 0, as it has already
+ * been installed. Any other hook_update_N functions provided by the
+ * installation profile will be run by update.php.
+ */
+function update_fix_d7_install_profile() {
+  $profile = drupal_get_profile();
+
+  // 'Default' profile has been renamed to 'Standard' in D7.
+  // We change the profile here to prevent a broken record in the system table.
+  // See system_update_7049().
+  if ($profile == 'default') {
+    $profile = 'standard';
+    variable_set('install_profile', $profile);
+  }
+
+  $results = db_select('system', 's')
+    ->fields('s', array('name', 'schema_version'))
+    ->condition('name', $profile)
+    ->condition('type', 'module')
+    ->execute()
+    ->fetchAll();
+
+  if (empty($results)) {
+    $filename = 'profiles/' . $profile . '/' . $profile . '.profile';
+
+    // Read profile info file
+    $info = drupal_parse_info_file(dirname($filename) . '/' . $profile . '.info');
+
+    // Merge in defaults.
+    $info = $info + array(
+      'dependencies' => array(),
+      'description' => '',
+      'package' => 'Other',
+      'version' => NULL,
+      'php' => DRUPAL_MINIMUM_PHP,
+      'files' => array(),
+    );
+
+    $values = array(
+      'filename' => $filename,
+      'name' => $profile,
+      'info' => serialize($info),
+      'schema_version' => 0,
+      'type' => 'module',
+      'status' => 1,
+      'owner' => '',
+    );
+
+    // Installation profile hooks are always executed last by the module system
+    $values['weight'] = 1000;
+
+    // Initializing the system table entry for the installation profile
+    db_insert('system')
+      ->fields(array_keys($values))
+      ->values($values)
+      ->execute();
+
+    // Reset the cached schema version.
+    drupal_get_installed_schema_version($profile, TRUE);
+
+    // Load the updates again to make sure the installation profile updates
+    // are loaded.
+    drupal_load_updates();
+  }
+}
+
+/**
+ * Parse pre-Drupal 7 database connection URLs and return D7 compatible array.
+ *
+ * @return
+ *   Drupal 7 DBTNG compatible array of database connection information.
+ */
+function update_parse_db_url($db_url, $db_prefix) {
+  $databases = array();
+  if (!is_array($db_url)) {
+    $db_url = array('default' => $db_url);
+  }
+  foreach ($db_url as $database => $url) {
+    $url = parse_url($url);
+    $databases[$database]['default'] = array(
+      // MySQLi uses the mysql driver.
+      'driver' => $url['scheme'] == 'mysqli' ? 'mysql' : $url['scheme'],
+      // Remove the leading slash to get the database name.
+      'database' => substr(urldecode($url['path']), 1),
+      'username' => urldecode($url['user']),
+      'password' => isset($url['pass']) ? urldecode($url['pass']) : '',
+      'host' => urldecode($url['host']),
+      'port' => isset($url['port']) ? urldecode($url['port']) : '',
+    );
+    if (isset($db_prefix)) {
+      $databases[$database]['default']['prefix'] = $db_prefix;
+    }
+  }
+  return $databases;
+}
+
+/**
+ * Constructs a session name compatible with a D6 environment.
+ *
+ * @return
+ *   D6-compatible session name string.
+ *
+ * @see drupal_settings_initialize()
+ */
+function update_get_d6_session_name() {
+  global $base_url, $cookie_domain;
+  $cookie_secure = ini_get('session.cookie_secure');
+
+  // If a custom cookie domain is set in settings.php, that variable forms
+  // the basis of the session name. Re-compute the D7 hashing method to find
+  // out if $cookie_domain was used as the session name.
+  if (($cookie_secure ? 'SSESS' : 'SESS') . substr(hash('sha256', $cookie_domain), 0, 32) == session_name()) {
+    $session_name = $cookie_domain;
+  }
+  else {
+    // Otherwise use $base_url as session name, without the protocol
+    // to use the same session identifiers across HTTP and HTTPS.
+    list( , $session_name) = explode('://', $base_url, 2);
+  }
+
+  if ($cookie_secure) {
+    $session_name .= 'SSL';
+  }
+
+  return 'SESS' . md5($session_name);
+}
+
+/**
+ * Implements callback_batch_operation().
+ *
+ * Performs one update and stores the results for display on the results page.
+ *
+ * If an update function completes successfully, it should return a message
+ * as a string indicating success, for example:
+ * @code
+ * return t('New index added successfully.');
+ * @endcode
+ *
+ * Alternatively, it may return nothing. In that case, no message
+ * will be displayed at all.
+ *
+ * If it fails for whatever reason, it should throw an instance of
+ * DrupalUpdateException with an appropriate error message, for example:
+ * @code
+ * throw new DrupalUpdateException(t('Description of what went wrong'));
+ * @endcode
+ *
+ * If an exception is thrown, the current update and all updates that depend on
+ * it will be aborted. The schema version will not be updated in this case, and
+ * all the aborted updates will continue to appear on update.php as updates
+ * that have not yet been run.
+ *
+ * If an update function needs to be re-run as part of a batch process, it
+ * should accept the $sandbox array by reference as its first parameter
+ * and set the #finished property to the percentage completed that it is, as a
+ * fraction of 1.
+ *
+ * @param $module
+ *   The module whose update will be run.
+ * @param $number
+ *   The update number to run.
+ * @param $dependency_map
+ *   An array whose keys are the names of all update functions that will be
+ *   performed during this batch process, and whose values are arrays of other
+ *   update functions that each one depends on.
+ * @param $context
+ *   The batch context array.
+ *
+ * @see update_resolve_dependencies()
+ */
+function update_do_one($module, $number, $dependency_map, &$context) {
+  $function = $module . '_update_' . $number;
+
+  // If this update was aborted in a previous step, or has a dependency that
+  // was aborted in a previous step, go no further.
+  if (!empty($context['results']['#abort']) && array_intersect($context['results']['#abort'], array_merge($dependency_map, array($function)))) {
+    return;
+  }
+
+  $ret = array();
+  if (function_exists($function)) {
+    try {
+      $ret['results']['query'] = $function($context['sandbox']);
+      $ret['results']['success'] = TRUE;
+    }
+    // @TODO We may want to do different error handling for different
+    // exception types, but for now we'll just log the exception and
+    // return the message for printing.
+    catch (Exception $e) {
+      watchdog_exception('update', $e);
+
+      require_once DRUPAL_ROOT . '/includes/errors.inc';
+      $variables = _drupal_decode_exception($e);
+      // The exception message is run through check_plain() by _drupal_decode_exception().
+      $ret['#abort'] = array('success' => FALSE, 'query' => t('%type: !message in %function (line %line of %file).', $variables));
+    }
+  }
+
+  if (isset($context['sandbox']['#finished'])) {
+    $context['finished'] = $context['sandbox']['#finished'];
+    unset($context['sandbox']['#finished']);
+  }
+
+  if (!isset($context['results'][$module])) {
+    $context['results'][$module] = array();
+  }
+  if (!isset($context['results'][$module][$number])) {
+    $context['results'][$module][$number] = array();
+  }
+  $context['results'][$module][$number] = array_merge($context['results'][$module][$number], $ret);
+
+  if (!empty($ret['#abort'])) {
+    // Record this function in the list of updates that were aborted.
+    $context['results']['#abort'][] = $function;
+  }
+
+  // Record the schema update if it was completed successfully.
+  if ($context['finished'] == 1 && empty($ret['#abort'])) {
+    drupal_set_installed_schema_version($module, $number);
+  }
+
+  $context['message'] = 'Updating ' . check_plain($module) . ' module';
+}
+
+/**
+ * @class Exception class used to throw error if a module update fails.
+ */
+class DrupalUpdateException extends Exception { }
+
+/**
+ * Starts the database update batch process.
+ *
+ * @param $start
+ *   An array whose keys contain the names of modules to be updated during the
+ *   current batch process, and whose values contain the number of the first
+ *   requested update for that module. The actual updates that are run (and the
+ *   order they are run in) will depend on the results of passing this data
+ *   through the update dependency system.
+ * @param $redirect
+ *   Path to redirect to when the batch has finished processing.
+ * @param $url
+ *   URL of the batch processing page (should only be used for separate
+ *   scripts like update.php).
+ * @param $batch
+ *   Optional parameters to pass into the batch API.
+ * @param $redirect_callback
+ *   (optional) Specify a function to be called to redirect to the progressive
+ *   processing page.
+ *
+ * @see update_resolve_dependencies()
+ */
+function update_batch($start, $redirect = NULL, $url = NULL, $batch = array(), $redirect_callback = 'drupal_goto') {
+  // During the update, bring the site offline so that schema changes do not
+  // affect visiting users.
+  $_SESSION['maintenance_mode'] = variable_get('maintenance_mode', FALSE);
+  if ($_SESSION['maintenance_mode'] == FALSE) {
+    variable_set('maintenance_mode', TRUE);
+  }
+
+  // Resolve any update dependencies to determine the actual updates that will
+  // be run and the order they will be run in.
+  $updates = update_resolve_dependencies($start);
+
+  // Store the dependencies for each update function in an array which the
+  // batch API can pass in to the batch operation each time it is called. (We
+  // do not store the entire update dependency array here because it is
+  // potentially very large.)
+  $dependency_map = array();
+  foreach ($updates as $function => $update) {
+    $dependency_map[$function] = !empty($update['reverse_paths']) ? array_keys($update['reverse_paths']) : array();
+  }
+
+  $operations = array();
+  foreach ($updates as $update) {
+    if ($update['allowed']) {
+      // Set the installed version of each module so updates will start at the
+      // correct place. (The updates are already sorted, so we can simply base
+      // this on the first one we come across in the above foreach loop.)
+      if (isset($start[$update['module']])) {
+        drupal_set_installed_schema_version($update['module'], $update['number'] - 1);
+        unset($start[$update['module']]);
+      }
+      // Add this update function to the batch.
+      $function = $update['module'] . '_update_' . $update['number'];
+      $operations[] = array('update_do_one', array($update['module'], $update['number'], $dependency_map[$function]));
+    }
+  }
+  $batch['operations'] = $operations;
+  $batch += array(
+    'title' => 'Updating',
+    'init_message' => 'Starting updates',
+    'error_message' => 'An unrecoverable error has occurred. You can find the error message below. It is advised to copy it to the clipboard for reference.',
+    'finished' => 'update_finished',
+    'file' => 'includes/update.inc',
+  );
+  batch_set($batch);
+  batch_process($redirect, $url, $redirect_callback);
+}
+
+/**
+ * Implements callback_batch_finished().
+ *
+ * Finishes the update process and stores the results for eventual display.
+ *
+ * After the updates run, all caches are flushed. The update results are
+ * stored into the session (for example, to be displayed on the update results
+ * page in update.php). Additionally, if the site was off-line, now that the
+ * update process is completed, the site is set back online.
+ *
+ * @param $success
+ *   Indicate that the batch API tasks were all completed successfully.
+ * @param $results
+ *   An array of all the results that were updated in update_do_one().
+ * @param $operations
+ *   A list of all the operations that had not been completed by the batch API.
+ *
+ * @see update_batch()
+ */
+function update_finished($success, $results, $operations) {
+  // Remove the D6 upgrade flag variable so that subsequent update runs do not
+  // get the wrong context.
+  variable_del('update_d6');
+
+  // Clear the caches in case the data has been updated.
+  drupal_flush_all_caches();
+
+  $_SESSION['update_results'] = $results;
+  $_SESSION['update_success'] = $success;
+  $_SESSION['updates_remaining'] = $operations;
+
+  // Now that the update is done, we can put the site back online if it was
+  // previously in maintenance mode.
+  if (isset($_SESSION['maintenance_mode']) && $_SESSION['maintenance_mode'] == FALSE) {
+    variable_set('maintenance_mode', FALSE);
+    unset($_SESSION['maintenance_mode']);
+  }
+}
+
+/**
+ * Returns a list of all the pending database updates.
+ *
+ * @return
+ *   An associative array keyed by module name which contains all information
+ *   about database updates that need to be run, and any updates that are not
+ *   going to proceed due to missing requirements. The system module will
+ *   always be listed first.
+ *
+ *   The subarray for each module can contain the following keys:
+ *   - start: The starting update that is to be processed. If this does not
+ *       exist then do not process any updates for this module as there are
+ *       other requirements that need to be resolved.
+ *   - warning: Any warnings about why this module can not be updated.
+ *   - pending: An array of all the pending updates for the module including
+ *       the update number and the description from source code comment for
+ *       each update function. This array is keyed by the update number.
+ */
+function update_get_update_list() {
+  // Make sure that the system module is first in the list of updates.
+  $ret = array('system' => array());
+
+  $modules = drupal_get_installed_schema_version(NULL, FALSE, TRUE);
+  foreach ($modules as $module => $schema_version) {
+    // Skip uninstalled and incompatible modules.
+    if ($schema_version == SCHEMA_UNINSTALLED || update_check_incompatibility($module)) {
+      continue;
+    }
+    // Otherwise, get the list of updates defined by this module.
+    $updates = drupal_get_schema_versions($module);
+    if ($updates !== FALSE) {
+      // module_invoke returns NULL for nonexisting hooks, so if no updates
+      // are removed, it will == 0.
+      $last_removed = module_invoke($module, 'update_last_removed');
+      if ($schema_version < $last_removed) {
+        $ret[$module]['warning'] = '<em>' . $module . '</em> module can not be updated. Its schema version is ' . $schema_version . '. Updates up to and including ' . $last_removed . ' have been removed in this release. In order to update <em>' . $module . '</em> module, you will first <a href="http://drupal.org/upgrade">need to upgrade</a> to the last version in which these updates were available.';
+        continue;
+      }
+
+      $updates = drupal_map_assoc($updates);
+      foreach (array_keys($updates) as $update) {
+        if ($update > $schema_version) {
+          // The description for an update comes from its Doxygen.
+          $func = new ReflectionFunction($module . '_update_' . $update);
+          $description = str_replace(array("\n", '*', '/'), '', $func->getDocComment());
+          $ret[$module]['pending'][$update] = "$update - $description";
+          if (!isset($ret[$module]['start'])) {
+            $ret[$module]['start'] = $update;
+          }
+        }
+      }
+      if (!isset($ret[$module]['start']) && isset($ret[$module]['pending'])) {
+        $ret[$module]['start'] = $schema_version;
+      }
+    }
+  }
+
+  if (empty($ret['system'])) {
+    unset($ret['system']);
+  }
+  return $ret;
+}
+
+/**
+ * Resolves dependencies in a set of module updates, and orders them correctly.
+ *
+ * This function receives a list of requested module updates and determines an
+ * appropriate order to run them in such that all update dependencies are met.
+ * Any updates whose dependencies cannot be met are included in the returned
+ * array but have the key 'allowed' set to FALSE; the calling function should
+ * take responsibility for ensuring that these updates are ultimately not
+ * performed.
+ *
+ * In addition, the returned array also includes detailed information about the
+ * dependency chain for each update, as provided by the depth-first search
+ * algorithm in drupal_depth_first_search().
+ *
+ * @param $starting_updates
+ *   An array whose keys contain the names of modules with updates to be run
+ *   and whose values contain the number of the first requested update for that
+ *   module.
+ *
+ * @return
+ *   An array whose keys are the names of all update functions within the
+ *   provided modules that would need to be run in order to fulfill the
+ *   request, arranged in the order in which the update functions should be
+ *   run. (This includes the provided starting update for each module and all
+ *   subsequent updates that are available.) The values are themselves arrays
+ *   containing all the keys provided by the drupal_depth_first_search()
+ *   algorithm, which encode detailed information about the dependency chain
+ *   for this update function (for example: 'paths', 'reverse_paths', 'weight',
+ *   and 'component'), as well as the following additional keys:
+ *   - 'allowed': A boolean which is TRUE when the update function's
+ *     dependencies are met, and FALSE otherwise. Calling functions should
+ *     inspect this value before running the update.
+ *   - 'missing_dependencies': An array containing the names of any other
+ *     update functions that are required by this one but that are unavailable
+ *     to be run. This array will be empty when 'allowed' is TRUE.
+ *   - 'module': The name of the module that this update function belongs to.
+ *   - 'number': The number of this update function within that module.
+ *
+ * @see drupal_depth_first_search()
+ */
+function update_resolve_dependencies($starting_updates) {
+  // Obtain a dependency graph for the requested update functions.
+  $update_functions = update_get_update_function_list($starting_updates);
+  $graph = update_build_dependency_graph($update_functions);
+
+  // Perform the depth-first search and sort the results.
+  require_once DRUPAL_ROOT . '/includes/graph.inc';
+  drupal_depth_first_search($graph);
+  uasort($graph, 'drupal_sort_weight');
+
+  foreach ($graph as $function => &$data) {
+    $module = $data['module'];
+    $number = $data['number'];
+    // If the update function is missing and has not yet been performed, mark
+    // it and everything that ultimately depends on it as disallowed.
+    if (update_is_missing($module, $number, $update_functions) && !update_already_performed($module, $number)) {
+      $data['allowed'] = FALSE;
+      foreach (array_keys($data['paths']) as $dependent) {
+        $graph[$dependent]['allowed'] = FALSE;
+        $graph[$dependent]['missing_dependencies'][] = $function;
+      }
+    }
+    elseif (!isset($data['allowed'])) {
+      $data['allowed'] = TRUE;
+      $data['missing_dependencies'] = array();
+    }
+    // Now that we have finished processing this function, remove it from the
+    // graph if it was not part of the original list. This ensures that we
+    // never try to run any updates that were not specifically requested.
+    if (!isset($update_functions[$module][$number])) {
+      unset($graph[$function]);
+    }
+  }
+
+  return $graph;
+}
+
+/**
+ * Returns an organized list of update functions for a set of modules.
+ *
+ * @param $starting_updates
+ *   An array whose keys contain the names of modules and whose values contain
+ *   the number of the first requested update for that module.
+ *
+ * @return
+ *   An array containing all the update functions that should be run for each
+ *   module, including the provided starting update and all subsequent updates
+ *   that are available. The keys of the array contain the module names, and
+ *   each value is an ordered array of update functions, keyed by the update
+ *   number.
+ *
+ * @see update_resolve_dependencies()
+ */
+function update_get_update_function_list($starting_updates) {
+  // Go through each module and find all updates that we need (including the
+  // first update that was requested and any updates that run after it).
+  $update_functions = array();
+  foreach ($starting_updates as $module => $version) {
+    $update_functions[$module] = array();
+    $updates = drupal_get_schema_versions($module);
+    if ($updates !== FALSE) {
+      $max_version = max($updates);
+      if ($version <= $max_version) {
+        foreach ($updates as $update) {
+          if ($update >= $version) {
+            $update_functions[$module][$update] = $module . '_update_' . $update;
+          }
+        }
+      }
+    }
+  }
+  return $update_functions;
+}
+
+/**
+ * Constructs a graph which encodes the dependencies between module updates.
+ *
+ * This function returns an associative array which contains a "directed graph"
+ * representation of the dependencies between a provided list of update
+ * functions, as well as any outside update functions that they directly depend
+ * on but that were not in the provided list. The vertices of the graph
+ * represent the update functions themselves, and each edge represents a
+ * requirement that the first update function needs to run before the second.
+ * For example, consider this graph:
+ *
+ * system_update_7000 ---> system_update_7001 ---> system_update_7002
+ *
+ * Visually, this indicates that system_update_7000() must run before
+ * system_update_7001(), which in turn must run before system_update_7002().
+ *
+ * The function takes into account standard dependencies within each module, as
+ * shown above (i.e., the fact that each module's updates must run in numerical
+ * order), but also finds any cross-module dependencies that are defined by
+ * modules which implement hook_update_dependencies(), and builds them into the
+ * graph as well.
+ *
+ * @param $update_functions
+ *   An organized array of update functions, in the format returned by
+ *   update_get_update_function_list().
+ *
+ * @return
+ *   A multidimensional array representing the dependency graph, suitable for
+ *   passing in to drupal_depth_first_search(), but with extra information
+ *   about each update function also included. Each array key contains the name
+ *   of an update function, including all update functions from the provided
+ *   list as well as any outside update functions which they directly depend
+ *   on. Each value is an associative array containing the following keys:
+ *   - 'edges': A representation of any other update functions that immediately
+ *     depend on this one. See drupal_depth_first_search() for more details on
+ *     the format.
+ *   - 'module': The name of the module that this update function belongs to.
+ *   - 'number': The number of this update function within that module.
+ *
+ * @see drupal_depth_first_search()
+ * @see update_resolve_dependencies()
+ */
+function update_build_dependency_graph($update_functions) {
+  // Initialize an array that will define a directed graph representing the
+  // dependencies between update functions.
+  $graph = array();
+
+  // Go through each update function and build an initial list of dependencies.
+  foreach ($update_functions as $module => $functions) {
+    $previous_function = NULL;
+    foreach ($functions as $number => $function) {
+      // Add an edge to the directed graph representing the fact that each
+      // update function in a given module must run after the update that
+      // numerically precedes it.
+      if ($previous_function) {
+        $graph[$previous_function]['edges'][$function] = TRUE;
+      }
+      $previous_function = $function;
+
+      // Define the module and update number associated with this function.
+      $graph[$function]['module'] = $module;
+      $graph[$function]['number'] = $number;
+    }
+  }
+
+  // Now add any explicit update dependencies declared by modules.
+  $update_dependencies = update_retrieve_dependencies();
+  foreach ($graph as $function => $data) {
+    if (!empty($update_dependencies[$data['module']][$data['number']])) {
+      foreach ($update_dependencies[$data['module']][$data['number']] as $module => $number) {
+        $dependency = $module . '_update_' . $number;
+        $graph[$dependency]['edges'][$function] = TRUE;
+        $graph[$dependency]['module'] = $module;
+        $graph[$dependency]['number'] = $number;
+      }
+    }
+  }
+
+  return $graph;
+}
+
+/**
+ * Determines if a module update is missing or unavailable.
+ *
+ * @param $module
+ *   The name of the module.
+ * @param $number
+ *   The number of the update within that module.
+ * @param $update_functions
+ *   An organized array of update functions, in the format returned by
+ *   update_get_update_function_list(). This should represent all module
+ *   updates that are requested to run at the time this function is called.
+ *
+ * @return
+ *   TRUE if the provided module update is not installed or is not in the
+ *   provided list of updates to run; FALSE otherwise.
+ */
+function update_is_missing($module, $number, $update_functions) {
+  return !isset($update_functions[$module][$number]) || !function_exists($update_functions[$module][$number]);
+}
+
+/**
+ * Determines if a module update has already been performed.
+ *
+ * @param $module
+ *   The name of the module.
+ * @param $number
+ *   The number of the update within that module.
+ *
+ * @return
+ *   TRUE if the database schema indicates that the update has already been
+ *   performed; FALSE otherwise.
+ */
+function update_already_performed($module, $number) {
+  return $number <= drupal_get_installed_schema_version($module);
+}
+
+/**
+ * Invokes hook_update_dependencies() in all installed modules.
+ *
+ * This function is similar to module_invoke_all(), with the main difference
+ * that it does not require that a module be enabled to invoke its hook, only
+ * that it be installed. This allows the update system to properly perform
+ * updates even on modules that are currently disabled.
+ *
+ * @return
+ *   An array of return values obtained by merging the results of the
+ *   hook_update_dependencies() implementations in all installed modules.
+ *
+ * @see module_invoke_all()
+ * @see hook_update_dependencies()
+ */
+function update_retrieve_dependencies() {
+  $return = array();
+  // Get a list of installed modules, arranged so that we invoke their hooks in
+  // the same order that module_invoke_all() does.
+  $modules = db_query("SELECT name FROM {system} WHERE type = 'module' AND schema_version <> :schema ORDER BY weight ASC, name ASC", array(':schema' => SCHEMA_UNINSTALLED))->fetchCol();
+  foreach ($modules as $module) {
+    $function = $module . '_update_dependencies';
+    if (function_exists($function)) {
+      $result = $function();
+      // Each implementation of hook_update_dependencies() returns a
+      // multidimensional, associative array containing some keys that
+      // represent module names (which are strings) and other keys that
+      // represent update function numbers (which are integers). We cannot use
+      // array_merge_recursive() to properly merge these results, since it
+      // treats strings and integers differently. Therefore, we have to
+      // explicitly loop through the expected array structure here and perform
+      // the merge manually.
+      if (isset($result) && is_array($result)) {
+        foreach ($result as $module => $module_data) {
+          foreach ($module_data as $update => $update_data) {
+            foreach ($update_data as $module_dependency => $update_dependency) {
+              // If there are redundant dependencies declared for the same
+              // update function (so that it is declared to depend on more than
+              // one update from a particular module), record the dependency on
+              // the highest numbered update here, since that automatically
+              // implies the previous ones. For example, if one module's
+              // implementation of hook_update_dependencies() required this
+              // ordering:
+              //
+              // system_update_7001 ---> user_update_7000
+              //
+              // but another module's implementation of the hook required this
+              // one:
+              //
+              // system_update_7002 ---> user_update_7000
+              //
+              // we record the second one, since system_update_7001() is always
+              // guaranteed to run before system_update_7002() anyway (within
+              // an individual module, updates are always run in numerical
+              // order).
+              if (!isset($return[$module][$update][$module_dependency]) || $update_dependency > $return[$module][$update][$module_dependency]) {
+                $return[$module][$update][$module_dependency] = $update_dependency;
+              }
+            }
+          }
+        }
+      }
+    }
+  }
+
+  return $return;
+}