update.inc 58.6 KB
Newer Older
1 2 3 4 5 6 7 8 9 10
<?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.
 */

11
use Drupal\Component\Graph\Graph;
12
use Drupal\Component\Utility\Settings;
13
use Drupal\Core\Config\FileStorage;
14
use Drupal\Core\Config\ConfigException;
15
use Drupal\Core\DrupalKernel;
16
use Drupal\Component\Uuid\Uuid;
17
use Drupal\Component\Utility\NestedArray;
18
use Symfony\Component\HttpFoundation\Request;
19

20
/**
21
 * Minimum schema version of Drupal 7 required for upgrade to Drupal 8.
22
 *
23
 * Upgrades from Drupal 7 to Drupal 8 require that Drupal 7 be running
24
 * the most recent version, or the upgrade could fail. We can't easily
25
 * check the Drupal 7 version once the update process has begun, so instead
26
 * we check the schema version of system.module.
27
 */
28
const REQUIRED_D7_SCHEMA_VERSION = '7069';
29

30
/**
31
 * Disables any extensions that are incompatible with the current core version.
32 33
 */
function update_fix_compatibility() {
34 35 36 37 38 39 40 41 42 43 44 45 46 47
  foreach (array('module', 'theme') as $type) {
    $config = config("system.$type");
    $save = FALSE;
    foreach ($config->get('enabled') as $name => $weight) {
      if (update_check_incompatibility($name, $type)) {
        $config->clear("enabled.$name");
        $save = TRUE;
      }
    }
    if ($save) {
      if ($type == 'module') {
        $config->set('enabled', module_config_sort($config->get('enabled')));
      }
      $config->save();
48 49 50 51 52
    }
  }
}

/**
53
 * Tests the compatibility of a module or theme.
54 55 56 57 58 59
 */
function update_check_incompatibility($name, $type = 'module') {
  static $themes, $modules;

  // Store values of expensive functions for future use.
  if (empty($themes) || empty($modules)) {
60 61 62 63
    // 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();
64
    $modules = system_rebuild_module_data();
65 66 67 68 69 70 71 72 73 74 75
  }

  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
76
      || version_compare(phpversion(), $file->info['php']) < 0) {
77 78 79 80 81 82
    return TRUE;
  }
  return FALSE;
}

/**
83
 * Performs extra steps required to bootstrap when using a Drupal 7 database.
84
 *
85 86
 * Users who still have a Drupal 7 database (and are in the process of
 * updating to Drupal 8) need extra help before a full bootstrap can be
87 88 89 90
 * 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
91
 * irreversible changes to the database are made here.
92
 */
93
function update_prepare_d8_bootstrap() {
94 95
  include_once __DIR__ . '/install.inc';
  include_once __DIR__ . '/schema.inc';
96
  // Bootstrap to configuration.
97
  drupal_bootstrap(DRUPAL_BOOTSTRAP_CONFIGURATION);
98

99 100 101
  // During the bootstrap to DRUPAL_BOOTSTRAP_PAGE_CACHE, code will try to read
  // the cache but the cache tables are not compatible yet. Use the Null backend
  // by default to avoid exceptions.
102 103 104
  $settings = settings()->getAll();
  $settings['cache']['default'] = 'cache.backend.memory';
  new Settings($settings);
105

106 107 108 109
  // Enable UpdateBundle service overrides. While the container_bundles array
  // does not need a key, let's use so it can be removed once the upgrade are
  // finished. @see update_flush_all_caches()
  $GLOBALS['conf']['container_bundles']['UpdateBundle'] = 'Drupal\Core\DependencyInjection\UpdateBundle';
110

111 112 113 114 115 116 117
  // Check whether settings.php needs to be rewritten.
  $settings_exist = !empty($GLOBALS['config_directories']);

  if (!$settings_exist || !is_dir(config_get_config_directory('active')) || !is_dir(config_get_config_directory('staging'))) {
    drupal_install_config_directories();
  }

118 119 120 121 122
  // Bootstrap the kernel.
  // Do not attempt to dump and write it.
  $kernel = new DrupalKernel('update', FALSE, drupal_classloader(), FALSE);
  $kernel->boot();

123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143
  // If any of the required settings needs to be written, then settings.php
  // needs to be writable.
  if (!$settings_exist) {
    $settings_file = conf_path() . '/settings.php';
    $writable = drupal_verify_install_file($settings_file, FILE_EXIST | FILE_READABLE | FILE_WRITABLE);
    $requirements['settings file']['title'] = 'Settings file';
    if ($writable) {
      $requirements['settings file'] += array(
        'value' => 'settings.php is writable.',
      );
    }
    else {
      $requirements['settings file'] += array(
        'value' => 'settings.php is not writable.',
        'severity' => REQUIREMENT_ERROR,
        'description' => '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);
  }

144
  // Bootstrap the database.
145 146
  drupal_bootstrap(DRUPAL_BOOTSTRAP_DATABASE);

147 148
  // If the site has not updated to Drupal 8 yet, check to make sure that it is
  // running an up-to-date version of Drupal 7 before proceeding. Note this has
149 150
  // to happen AFTER the database bootstraps because of
  // drupal_get_installed_schema_version().
151 152 153 154 155 156
  try {
    $system_schema = drupal_get_installed_schema_version('system');
  }
  catch (\Exception $e) {
    $system_schema = db_query('SELECT schema_version FROM {system} WHERE name = :system', array(':system' => 'system'))->fetchField();
  }
157
  if ($system_schema < 8000) {
158
    $has_required_schema = $system_schema >= REQUIRED_D7_SCHEMA_VERSION;
159
    $requirements = array(
160 161 162
      'drupal 7 version' => array(
        'title' => 'Drupal 7 version',
        'value' => $has_required_schema ? 'You are running a current version of Drupal 7.' : 'You are not running a current version of Drupal 7',
163
        'severity' => $has_required_schema ? NULL : REQUIREMENT_ERROR,
164
        'description' => $has_required_schema ? '' : 'Please update your Drupal 7 installation to the most recent version before attempting to upgrade to Drupal 8',
165 166
      ),
    );
167 168
    update_extra_requirements($requirements);

169 170 171 172
    // @todo update.php stages seem to be completely screwed up; the initial
    //   requirements check is not supposed to change the system. All of the
    //   following code seems to have been mistakenly/unknowingly added here and
    //   does not belong into update_prepare_d8_bootstrap().
173
    if ($has_required_schema) {
174 175
      if (!db_table_exists('key_value')) {
        $specs = array(
176
          'description' => 'Generic key-value storage table. See the state system for an example.',
177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203
          'fields' => array(
            'collection' => array(
              'description' => 'A named collection of key and value pairs.',
              'type' => 'varchar',
              'length' => 128,
              'not null' => TRUE,
              'default' => '',
            ),
            'name' => array(
              'description' => 'The key of the key-value pair. As KEY is a SQL reserved keyword, name was chosen instead.',
              'type' => 'varchar',
              'length' => 128,
              'not null' => TRUE,
              'default' => '',
            ),
            'value' => array(
              'description' => 'The value.',
              'type' => 'blob',
              'not null' => TRUE,
              'size' => 'big',
              'translatable' => TRUE,
            ),
          ),
          'primary key' => array('collection', 'name'),
        );
        db_create_table('key_value', $specs);
      }
204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313
      if (!db_table_exists('cache_tags')) {
        $table = array(
          'description' => 'Cache table for tracking cache tags related to the cache bin.',
          'fields' => array(
            'tag' => array(
              'description' => 'Namespace-prefixed tag string.',
              'type' => 'varchar',
              'length' => 255,
              'not null' => TRUE,
              'default' => '',
            ),
            'invalidations' => array(
              'description' => 'Number incremented when the tag is invalidated.',
              'type' => 'int',
              'not null' => TRUE,
              'default' => 0,
            ),
            'deletions' => array(
              'description' => 'Number incremented when the tag is deleted.',
              'type' => 'int',
              'not null' => TRUE,
              'default' => 0,
            ),
          ),
          'primary key' => array('tag'),
        );
        db_create_table('cache_tags', $table);
      }
      if (!db_table_exists('cache_config')) {
        $spec = array(
          'description' =>  'Cache table for configuration data.',
          '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,
            ),
            'tags' => array(
              'description' => 'Space-separated list of cache tags for this entry.',
              'type' => 'text',
              'size' => 'big',
              'not null' => FALSE,
            ),
            'checksum_invalidations' => array(
              'description' => 'The tag invalidation sum when this entry was saved.',
              'type' => 'int',
              'not null' => TRUE,
              'default' => 0,
            ),
            'checksum_deletions' => array(
              'description' => 'The tag deletion sum when this entry was saved.',
              'type' => 'int',
              'not null' => TRUE,
              'default' => 0,
            ),
          ),
          'indexes' => array(
            'expire' => array('expire'),
          ),
          'primary key' => array('cid'),
        );
        db_create_table('cache_config', $spec);
      }

      require_once DRUPAL_ROOT . '/core/modules/system/system.install';
      $tables = array(
        'cache',
        'cache_bootstrap',
        'cache_block',
        'cache_field',
        'cache_filter',
        'cache_form',
        'cache_image',
        'cache_menu',
        'cache_page',
        'cache_path',
        'cache_update',
      );

      foreach ($tables as $table) {
        update_add_cache_columns($table);
      }

314 315 316
      // Bootstrap variables so we can update theme while preparing the update
      // process.
      drupal_bootstrap(DRUPAL_BOOTSTRAP_VARIABLES);
317

318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337
      // Update the 'language_default' system variable, if configured.
      // Required to run before drupal_install_config_directories(), since that
      // triggers a call into system_stream_wrappers(), which calls t(), which
      // calls into language_default().
      $language_default = variable_get('language_default');
      if (!empty($language_default) && (isset($language_default->langcode) || isset($language_default->language))) {
        if (!isset($language_default->langcode)) {
          $language_default->langcode = $language_default->language;
        }
        unset($language_default->language);
        // In D8, the 'language_default' is not anymore an object, but an array,
        // so make sure that the new value that is saved into this variable is an
        // array.
        variable_set('language_default', (array) $language_default);
      }

      $module_config = config('system.module');
      $disabled_modules = config('system.module.disabled');
      $theme_config = config('system.theme');
      $disabled_themes = config('system.theme.disabled');
338
      $schema_store = Drupal::keyValue('system.schema');
339 340 341 342 343 344

      // Load system.module, because update_prepare_d8_bootstrap() is called in
      // the initial minimal update.php bootstrap that performs the core
      // requirements check.
      require_once DRUPAL_ROOT . '/core/modules/system/system.module';

345 346
      // Make sure that the bootstrap cache is cleared as that might contain
      // incompatible data structures.
347
      cache('bootstrap')->deleteAll();
348

349 350 351 352 353 354 355
      // Retrieve all installed extensions from the {system} table.
      // Uninstalled extensions are ignored and not converted.
      $result = db_query('SELECT name, status, weight, schema_version, type FROM {system} WHERE type = :theme OR (type = :module AND schema_version <> :schema_uninstalled)', array(
        ':theme' => 'theme',
        ':module' => 'module',
        ':schema_uninstalled' => SCHEMA_UNINSTALLED,
      ));
356

357 358 359 360 361
      $module_data = _system_rebuild_module_data();

      // Migrate each extension into configuration, varying by the extension's
      // status, and record its schema version.
      foreach ($result as $record) {
362 363 364 365 366 367 368 369 370 371 372 373
        // Before migrating any extension into configuration, make sure the
        // extensions name length is not higher than the limit.
        if (drupal_strlen($record->name) > 50) {
          $requirements['module name too long ' . $record->name] = array(
            'title' => 'Module name too long',
            'value' => format_string('@name is @count characters long.', array('@name' => $record->name, '@count' => drupal_strlen($record->name))),
            'description' => 'Module names longer than 50 characters are <a href="https://drupal.org/node/2014073">no longer supported</a>.',
            'severity' => REQUIREMENT_ERROR,
          );
          update_extra_requirements($requirements);
        }

374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391
        if ($record->type == 'module') {
          if ($record->status && isset($module_data[$record->name])) {
            $module_config->set('enabled.' . $record->name, $record->weight);
          }
          else {
            $disabled_modules->set($record->name, $record->weight);
          }
        }
        elseif ($record->type == 'theme') {
          if ($record->status) {
            $theme_config->set('enabled.' . $record->name, 0);
          }
          else {
            $disabled_themes->set($record->name, 0);
          }
        }
        $schema_store->set($record->name, $record->schema_version);
      }
392 393 394 395 396 397
      $sorted_modules = module_config_sort($module_config->get('enabled'));
      $module_config->set('enabled', $sorted_modules)->save();
      $sorted_with_filenames = array();
      foreach (array_keys($sorted_modules) as $m) {
        $sorted_with_filenames[$m] = drupal_get_filename('module', $m);
      }
398
      Drupal::moduleHandler()->setModuleList($sorted_with_filenames);
399 400 401 402
      $disabled_modules->save();
      $theme_config->save();
      $disabled_themes->save();

403 404 405 406 407 408
      // Migrate the private key to state. This is used to create the token for
      // the upgrade batch so needs to be be done before the upgrade has begun.
      update_variables_to_state(array(
        'drupal_private_key' => 'system.private_key',
      ));

409 410 411 412 413
      // Update the dynamic include paths that might be used before running the
      // proper update functions.
      update_prepare_stored_includes();
      // Update the environment for the language bootstrap if needed.
      update_prepare_d8_language();
414 415 416
      // Rebuild kernel after new language fields are added in the database
      // because the translation service depends on them being there.
      Drupal::service('kernel')->updateModules($sorted_with_filenames, $sorted_with_filenames);
417

418 419 420 421 422 423 424 425 426
      // Change language column to langcode in url_alias.
      if (db_table_exists('url_alias') && db_field_exists('url_alias', 'language')) {
        db_drop_index('url_alias', 'alias_language_pid');
        db_drop_index('url_alias', 'source_language_pid');
        $langcode_spec = array(
          'description' => "The language code this alias is for; if 'und', the alias will be used for unknown languages. Each Drupal path can have an alias for each supported language.",
          'type' => 'varchar',
          'length' => 12,
          'not null' => TRUE,
427
          'default' => '',
428 429 430 431 432 433 434 435 436
        );
        $langcode_indexes = array('indexes' =>
          array(
            'alias_langcode_pid' => array('alias', 'langcode', 'pid'),
            'source_langcode_pid' => array('source', 'langcode', 'pid'),
          ),
        );
        db_change_field('url_alias', 'language', 'langcode', $langcode_spec, $langcode_indexes);
      }
437 438
    }
  }
439
  // Now remove the cache override.
440 441 442 443 444
  $settings = settings()->getAll();
  unset($settings['cache']['default']);
  new Settings($settings);
  $kernel = new DrupalKernel('update', FALSE, drupal_classloader(), FALSE);
  $kernel->boot();
445 446
}

447
/**
448
 * Fixes stored include paths to match the "/core" migration.
449 450 451
 */
function update_prepare_stored_includes() {
  // Update language negotiation settings.
452
  foreach (language_types_get_all() as $language_type) {
453
    $negotiation = variable_get("language_negotiation_$language_type", array());
454
    foreach ($negotiation as &$method) {
455
      if (isset($method['file']) && $method['file'] == 'includes/locale.inc') {
456
        $method['file'] = 'core/modules/language/language.negotiation.inc';
457 458 459 460 461 462
      }
    }
    variable_set("language_negotiation_$language_type", $negotiation);
  }
}

463
/**
464
 * Prepares Drupal 8 language changes for the bootstrap if needed.
465 466 467
 */
function update_prepare_d8_language() {
  if (db_table_exists('languages')) {
468 469 470

    module_enable(array('language'));

471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486
    $languages = db_select('languages', 'l')
      ->fields('l')
      ->execute();
    $plurals = array();
    $javascript = array();
    $prefixes = array();
    $domains = array();
    foreach ($languages as $language) {
      $plurals[$language->language] = array(
        'plurals' => $language->plurals,
        'formula' => $language->formula,
      );
      $javascript[$language->language] = $language->javascript;
      $prefixes[$language->language] = $language->prefix;
      $domains[$language->language] = $language->domain;
    }
487 488
    Drupal::state()->set('locale.translation.plurals', $plurals);
    Drupal::state()->set('locale.translation.javascript', $javascript);
489 490 491 492
    config('language.negotiation')
      ->set('url.prefixes', $prefixes)
      ->set('url.domains', $domains)
      ->save();
493 494 495 496 497 498 499 500

    // Drop now unneeded columns.
    db_drop_field('languages', 'plurals');
    db_drop_field('languages', 'formula');
    db_drop_field('languages', 'javascript');
    db_drop_field('languages', 'prefix');
    db_drop_field('languages', 'domain');
    db_drop_field('languages', 'native');
501 502 503 504
    db_drop_field('languages', 'enabled');

    // Update language count.
    variable_set('language_count', db_query('SELECT COUNT(language) FROM {languages}')->fetchField());
505 506 507 508

    // Rename the languages table to language.
    db_rename_table('languages', 'language');

509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532
    // Rename language column to langcode and set it again as the primary key.
    if (db_field_exists('language', 'language')) {
      db_drop_primary_key('language');
      $langcode_spec = array(
        'type' => 'varchar',
        'length' => 12,
        'not null' => TRUE,
        'default' => '',
        'description' => "Language code, e.g. 'de' or 'en-US'.",
      );
      db_change_field('language', 'language', 'langcode', $langcode_spec, array('primary key' => array('langcode')));
    }

    // Adds the locked column and saves the special languages.
    if (!db_field_exists('language', 'locked')) {
      $locked_spec = array(
        'type' => 'int',
        'size' => 'tiny',
        'not null' => TRUE,
        'default' => 0,
        'description' => 'A boolean indicating whether the administrator can edit or delete the language.',
      );
      db_add_field('language', 'locked', $locked_spec);

533
      $max_language_weight = db_query('SELECT MAX(weight) FROM {language}')->fetchField();
534
      $languages = language_default_locked_languages($max_language_weight);
535 536 537 538 539 540 541 542 543 544 545 546
      foreach ($languages as $language) {
        db_insert('language')
          ->fields(array(
            'langcode' => $language->langcode,
            'name' => $language->name,
            'weight' => $language->weight,
            // These languages are locked, default to enabled.
            'locked' => 1,
          ))
          ->execute();
      }
    }
547 548 549 550 551 552 553 554 555

    // Update the 'language_default' system variable with the langcode change.
    $language_default = variable_get('language_default');
    if (!empty($language_default)) {
      if (isset($language_default->language)) {
        $language_default->langcode = $language_default->language;
        unset($language_default->language);
      }
      unset($language_default->enabled);
556 557 558 559
      // In D8, the 'language_default' is not anymore an object, but an array,
      // so make sure that the new value that is saved into this variable is an
      // array.
      variable_set('language_default', (array) $language_default);
560
    }
561 562 563 564 565 566 567 568 569 570 571 572 573

    // Add column to track customized string status to locales_target.
    // When updating in a non-English language, the locale translation system is
    // triggered, which attempts to query string translations already.
    if (db_table_exists('locales_target') && !db_field_exists('locales_target', 'customized')) {
      $spec = array(
        'type' => 'int',
        'not null' => TRUE,
        'default' => 0, // LOCALE_NOT_CUSTOMIZED
        'description' => 'Boolean indicating whether the translation is custom to this site.',
      );
      db_add_field('locales_target', 'customized', $spec);
    }
574 575 576 577 578 579 580 581 582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613 614 615 616 617 618 619 620 621 622 623 624 625 626 627
    // Add locales_location table to track string locations.
    // When updating in a non-English language, this table is used for
    // refreshing JavaScript translations.
    if (db_table_exists('locales_source') && !db_table_exists('locales_location')) {
      $table = array(
        'description' => 'Location information for source strings.',
        'fields' => array(
          'lid' => array(
            'type' => 'serial',
            'not null' => TRUE,
            'description' => 'Unique identifier of this location.',
          ),
          'sid' => array(
            'type' => 'int',
            'not null' => TRUE,
            'description' => 'Unique identifier of this string.',
          ),
          'type' => array(
            'type' => 'varchar',
            'length' => 50,
            'not null' => TRUE,
            'default' => '',
            'description' => 'The location type (file, config, path, etc).',
          ),
          'name' => array(
            'type' => 'varchar',
            'length' => 255,
            'not null' => TRUE,
            'default' => '',
            'description' => 'Type dependent location information (file name, path, etc).',
          ),
          'version' => array(
            'type' => 'varchar',
            'length' => 20,
            'not null' => TRUE,
            'default' => 'none',
            'description' => 'Version of Drupal where the location was found.',
          ),
        ),
        'primary key' => array('lid'),
        'foreign keys' => array(
          'locales_source' => array(
            'table' => 'locales_source',
            'columns' => array('sid' => 'lid'),
          ),
        ),
        'indexes' => array(
          'string_id' => array('sid'),
          'string_type' => array('sid', 'type'),
        ),
      );

      db_create_table('locales_location', $table);
    }
628 629 630
  }
}

631
/**
632
 * Performs Drupal 7.x to 8.x required update.php updates.
633
 *
634
 * This function runs when update.php is run the first time for 8.x,
635 636 637 638
 * 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.
 */
639
function update_fix_d8_requirements() {
640
  if (drupal_get_installed_schema_version('system') < 8000 && !update_variable_get('update_d8_requirements', FALSE)) {
641 642 643

    // Make sure that file.module is enabled as it is required for the user
    // picture upgrade path.
644
    module_enable(array('file'));
645

646 647 648 649 650 651 652 653 654 655 656 657 658 659 660 661 662 663 664 665 666 667 668 669 670 671 672 673 674 675 676 677 678 679 680 681 682 683
    $schema = array(
      'description' => 'Generic key/value storage table with an expiration.',
      'fields' => array(
        'collection' => array(
          'description' => 'A named collection of key and value pairs.',
          'type' => 'varchar',
          'length' => 128,
          'not null' => TRUE,
          'default' => '',
        ),
        'name' => array(
          // KEY is an SQL reserved word, so use 'name' as the key's field name.
          'description' => 'The key of the key/value pair.',
          'type' => 'varchar',
          'length' => 128,
          'not null' => TRUE,
          'default' => '',
        ),
        'value' => array(
          'description' => 'The value of the key/value pair.',
          'type' => 'blob',
          'not null' => TRUE,
          'size' => 'big',
        ),
        'expire' => array(
          'description' => 'The time since Unix epoch in seconds when this item expires. Defaults to the maximum possible time.',
          'type' => 'int',
          'not null' => TRUE,
          'default' => 2147483647,
        ),
      ),
      'primary key' => array('collection', 'name'),
      'indexes' => array(
        'all' => array('name', 'collection', 'expire'),
      ),
    );
    db_create_table('key_value_expire', $schema);

684 685 686 687 688 689 690
    // Views module is required to convert all previously existing listings into
    // views configurations.
    // Like any other module APIs and services, Views' services are not available
    // in update.php. Existing listings are migrated into configuration, using
    // the limited standard tools of raw database queries and config().
    module_enable(array('views'));

691
    update_variable_set('update_d8_requirements', TRUE);
692
  }
693
}
694 695

/**
696
 * Forces a module to a given schema version.
697
 *
698
 * This function is rarely necessary.
699
 *
700 701 702 703
 * @param string $module
 *   Name of the module.
 * @param string $schema_version
 *   The schema version the module should be set to.
704
 */
705 706 707 708 709 710
function update_set_schema($module, $schema_version) {
  Drupal::keyValue('system.schema')->set($module, $schema_version);
  // system_list_reset() is in module.inc but that would only be available
  // once the variable bootstrap is done.
  require_once __DIR__ . '/module.inc';
  system_list_reset();
711
}
712

713
/**
714
 * Performs one update and stores the results for display on the results page.
715
 *
716 717 718 719 720 721 722 723 724 725
 * 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
726 727
 * Drupal\Core\Utility\UpdateException with an appropriate error message, for
 * example:
728
 * @code
729 730
 * use Drupal\Core\Utility\UpdateException;
 * throw new UpdateException(t('Description of what went wrong'));
731 732
 * @endcode
 *
733 734 735 736
 * 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.
737
 *
738 739 740 741 742
 * 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.
 *
743 744 745 746
 * @param $module
 *   The module whose update will be run.
 * @param $number
 *   The update number to run.
747 748 749 750
 * @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.
751
 * @param $context
752 753 754
 *   The batch context array.
 *
 * @see update_resolve_dependencies()
755
 */
756 757 758 759 760
function update_do_one($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.
761
  if (!empty($context['results']['#abort']) && array_intersect($context['results']['#abort'], array_merge($dependency_map, array($function)))) {
762 763 764
    return;
  }

765
  $ret = array();
766
  if (function_exists($function)) {
767 768 769 770
    try {
      $ret['results']['query'] = $function($context['sandbox']);
      $ret['results']['success'] = TRUE;
    }
771 772 773
    // @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.
774
    catch (Exception $e) {
775 776
      watchdog_exception('update', $e);

777
      require_once __DIR__ . '/errors.inc';
778
      $variables = _drupal_decode_exception($e);
779
      unset($variables['backtrace']);
780 781
      // 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));
782
    }
783 784
  }

785 786 787 788 789
  if (isset($context['sandbox']['#finished'])) {
    $context['finished'] = $context['sandbox']['#finished'];
    unset($context['sandbox']['#finished']);
  }

790 791 792 793 794 795 796 797 798
  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'])) {
799 800
    // Record this function in the list of updates that were aborted.
    $context['results']['#abort'][] = $function;
801
  }
802

803
  // Record the schema update if it was completed successfully.
804
  if ($context['finished'] == 1 && empty($ret['#abort'])) {
805 806 807 808 809 810
    drupal_set_installed_schema_version($module, $number);
  }

  $context['message'] = 'Updating ' . check_plain($module) . ' module';
}

811
/**
812
 * Starts the database update batch process.
813 814
 *
 * @param $start
815 816 817 818 819
 *   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.
820 821 822 823 824 825 826
 * @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.
827 828 829
 * @param $redirect_callback
 *   (optional) Specify a function to be called to redirect to the progressive
 *   processing page.
830 831
 *
 * @see update_resolve_dependencies()
832
 */
833
function update_batch($start, $redirect = NULL, $url = NULL, $batch = array(), $redirect_callback = NULL) {
834 835
  // During the update, bring the site offline so that schema changes do not
  // affect visiting users.
836 837 838 839 840 841 842 843 844 845 846
  $maintenance_mode = config('system.maintenance')->get('enabled');
  if (isset($maintenance_mode)) {
    $_SESSION['maintenance_mode'] = $maintenance_mode;
  }
  if (empty($_SESSION['maintenance_mode'])) {
    $GLOBALS['conf']['system.maintenance']['enabled'] = TRUE;
    // @todo This is borderline state, not config. Or a global system
    //   "maintenance lock".
    if (db_table_exists('config')) {
      config('system.maintenance')->set('enabled', TRUE)->save();
    }
847 848
  }

849 850 851 852 853 854 855 856 857 858 859 860 861
  // 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();
  }

862
  $operations = array();
863 864 865 866 867 868 869 870
  foreach ($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']]);
871
      }
872
      // Add this update function to the batch.
873 874
      $function = $update['module'] . '_update_' . $update['number'];
      $operations[] = array('update_do_one', array($update['module'], $update['number'], $dependency_map[$function]));
875 876 877 878 879 880 881 882
    }
  }
  $batch['operations'] = $operations;
  $batch += array(
    'title' => 'Updating',
    'init_message' => 'Starting updates',
    'error_message' => 'An unrecoverable error has occurred. You can find the error message below. It is advised to copy it to the clipboard for reference.',
    'finished' => 'update_finished',
883
    'file' => 'core/includes/update.inc',
884 885
  );
  batch_set($batch);
886
  return batch_process($redirect, $url, $redirect_callback);
887 888 889
}

/**
890
 * Finishes the update process and stores the results for eventual display.
891 892 893 894 895 896 897 898 899 900 901 902 903 904 905 906 907
 *
 * 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) {
  // Clear the caches in case the data has been updated.
908
  update_flush_all_caches();
909 910 911 912 913 914

  $_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
915
  // previously in maintenance mode.
916 917 918 919
  if (isset($_SESSION['maintenance_mode'])) {
    $GLOBALS['conf']['system.maintenance']['enabled'] = FALSE;
    // At this point, the configuration system should exist.
    config('system.maintenance')->set('enabled', FALSE)->save();
920
    unset($_SESSION['maintenance_mode']);
921 922 923
  }
}

924
/**
925
 * Returns a list of all the pending database updates.
926 927 928 929 930 931 932 933 934 935 936 937 938 939 940 941 942 943 944
 *
 * @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());
945

946 947
  $modules = drupal_get_installed_schema_version(NULL, FALSE, TRUE);
  foreach ($modules as $module => $schema_version) {
948 949 950 951 952
    // Skip uninstalled and incompatible modules.
    if ($schema_version == SCHEMA_UNINSTALLED || update_check_incompatibility($module)) {
      continue;
    }
    // Otherwise, get the list of updates defined by this module.
953
    $updates = drupal_get_schema_versions($module);
954
    if ($updates !== FALSE) {
955 956 957 958 959 960 961
      // 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;
      }
962

963 964 965
      $updates = drupal_map_assoc($updates);
      foreach (array_keys($updates) as $update) {
        if ($update > $schema_version) {
966
          // The description for an update comes from its Doxygen.
967
          $func = new ReflectionFunction($module . '_update_' . $update);
968 969 970 971
          $description = str_replace(array("\n", '*', '/'), '', $func->getDocComment());
          $ret[$module]['pending'][$update] = "$update - $description";
          if (!isset($ret[$module]['start'])) {
            $ret[$module]['start'] = $update;
972 973 974 975 976 977 978 979
          }
        }
      }
      if (!isset($ret[$module]['start']) && isset($ret[$module]['pending'])) {
        $ret[$module]['start'] = $schema_version;
      }
    }
  }
980

981 982 983 984 985 986
  if (empty($ret['system'])) {
    unset($ret['system']);
  }
  return $ret;
}

987 988 989 990 991 992 993 994 995 996 997 998
/**
 * 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
999
 * algorithm in Drupal\Component\Graph\Graph::searchAndSort().
1000 1001 1002 1003 1004 1005 1006 1007 1008 1009 1010 1011
 *
 * @param $starting_updates
 *   An array whose keys contain the names of modules with updates to be run
 *   and whose values contain the number of the first requested update for that
 *   module.
 *
 * @return
 *   An array whose keys are the names of all update functions within the
 *   provided modules that would need to be run in order to fulfill the
 *   request, arranged in the order in which the update functions should be
 *   run. (This includes the provided starting update for each module and all
 *   subsequent updates that are available.) The values are themselves arrays
1012 1013 1014
 *   containing all the keys provided by the
 *   Drupal\Component\Graph\Graph::searchAndSort() algorithm, which encode
 *   detailed information about the dependency chain for this update function
1015 1016
 *   (for example: 'paths', 'reverse_paths', 'weight', and 'component'), as
 *   well as the following additional keys:
1017 1018 1019 1020 1021 1022 1023 1024 1025
 *   - 'allowed': A boolean which is TRUE when the update function's
 *     dependencies are met, and FALSE otherwise. Calling functions should
 *     inspect this value before running the update.
 *   - 'missing_dependencies': An array containing the names of any other
 *     update functions that are required by this one but that are unavailable
 *     to be run. This array will be empty when 'allowed' is TRUE.
 *   - 'module': The name of the module that this update function belongs to.
 *   - 'number': The number of this update function within that module.
 *
1026
 * @see Drupal\Component\Graph\Graph::searchAndSort()
1027 1028 1029 1030 1031 1032
 */
function update_resolve_dependencies($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);

1033 1034 1035
  // Perform the depth-first search and sort on the results.
  $graph_object = new Graph($graph);
  $graph = $graph_object->searchAndSort();
1036 1037 1038 1039 1040 1041 1042 1043 1044 1045 1046 1047 1048 1049 1050 1051 1052 1053 1054 1055 1056 1057 1058 1059 1060 1061 1062 1063 1064 1065 1066 1067 1068 1069 1070 1071 1072 1073 1074 1075 1076 1077 1078 1079 1080 1081 1082 1083 1084 1085 1086 1087
  uasort($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);
1088 1089 1090 1091 1092 1093 1094
    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;
          }
1095 1096 1097 1098 1099 1100 1101 1102 1103 1104 1105 1106 1107 1108 1109 1110 1111 1112
        }
      }
    }
  }
  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:
 *
1113
 * system_update_8000 ---> system_update_8001 ---> system_update_8002
1114
 *
1115 1116
 * Visually, this indicates that system_update_8000() must run before
 * system_update_8001(), which in turn must run before system_update_8002().
1117 1118 1119 1120 1121 1122 1123 1124 1125 1126 1127 1128 1129
 *
 * 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 $update_functions
 *   An organized array of update functions, in the format returned by
 *   update_get_update_function_list().
 *
 * @return
 *   A multidimensional array representing the dependency graph, suitable for
1130 1131 1132 1133 1134 1135
 *   passing in to Drupal\Component\Graph\Graph::searchAndSort(), but with extra
 *   information about each update function also included. Each array key
 *   contains the name of an update function, including all update functions
 *   from the provided list as well as any outside update functions which they
 *   directly depend on. Each value is an associative array containing the
 *   following keys:
1136
 *   - 'edges': A representation of any other update functions that immediately
1137 1138
 *     depend on this one. See Drupal\Component\Graph\Graph::searchAndSort() for
 *     more details on the format.
1139 1140 1141
 *   - 'module': The name of the module that this update function belongs to.
 *   - 'number': The number of this update function within that module.
 *
1142
 * @see Drupal\Component\Graph\Graph::searchAndSort()
1143 1144 1145 1146 1147 1148 1149 1150 1151 1152 1153 1154 1155 1156 1157 1158 1159 1160 1161 1162 1163 1164 1165 1166 1167 1168
 * @see update_resolve_dependencies()
 */
function update_build_dependency_graph($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.
1169
  $update_dependencies = update_retrieve_dependencies();
1170 1171 1172 1173 1174 1175 1176 1177 1178 1179 1180 1181 1182 1183 1184 1185 1186 1187 1188 1189 1190 1191 1192 1193 1194 1195 1196 1197 1198 1199 1200 1201 1202 1203 1204 1205 1206 1207 1208 1209 1210 1211 1212 1213 1214 1215 1216 1217 1218 1219 1220
  foreach ($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);
}

/**
1221
 * Invokes hook_update_dependencies() in all installed modules.
1222
 *
1223 1224 1225 1226
 * 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.
1227 1228
 *
 * @return
1229 1230
 *   An array of return values obtained by merging the results of the
 *   hook_update_dependencies() implementations in all installed modules.
1231 1232
 *
 * @see module_invoke_all()
1233
 * @see hook_update_dependencies()
1234
 */
1235
function update_retrieve_dependencies() {
1236
  $return = array();
1237 1238
  // Get a list of installed modules, arranged so that we invoke their hooks in
  // the same order that module_invoke_all() does.
1239
  foreach (Drupal::keyValue('system.schema')->getAll() as $module => $schema) {
1240 1241 1242 1243
    if ($schema == SCHEMA_UNINSTALLED) {
      // Nothing to upgrade.
      continue;
    }
1244
    $function = $module . '_update_dependencies';
1245 1246
    // Ensure install file is loaded.
    module_load_install($module);
1247
    if (function_exists($function)) {
1248 1249 1250 1251 1252 1253 1254 1255 1256
      $result = $function();
      // Each implementation of hook_update_dependencies() returns a
      // multidimensional, associative array containing some keys that
      // represent module names (which are strings) and other keys that
      // represent update function numbers (which are integers). We cannot use
      // array_merge_recursive() to properly merge these results, since it
      // treats strings and integers differently. Therefore, we have to
      // explicitly loop through the expected array structure here and perform
      // the merge manually.
1257
      if (isset($result) && is_array($result)) {
1258 1259 1260 1261 1262 1263 1264 1265 1266 1267 1268
        foreach ($result as $module => $module_data) {
          foreach ($module_data as $update => $update_data) {
            foreach ($update_data as $module_dependency => $update_dependency) {
              // If there are redundant dependencies declared for the same
              // update function (so that it is declared to depend on more than
              // one update from a particular module), record the dependency on
              // the highest numbered update here, since that automatically
              // implies the previous ones. For example, if one module's
              // implementation of hook_update_dependencies() required this
              // ordering:
              //
1269
              // system_update_8001 ---> user_update_8000
1270 1271 1272 1273
              //
              // but another module's implementation of the hook required this
              // one:
              //
1274
              // system_update_8002 ---> user_update_8000
1275
              //
1276 1277
              // we record the second one, since system_update_8001() is always
              // guaranteed to run before system_update_8002() anyway (within
1278 1279 1280 1281 1282 1283 1284 1285
              // an individual module, updates are always run in numerical
              // order).
              if (!isset($return[$module][$update][$module_dependency]) || $update_dependency > $return[$module][$update][$module_dependency]) {
                $return[$module][$update][$module_dependency] = $update_dependency;
              }
            }
          }
        }
1286 1287 1288 1289 1290 1291 1292
      }
    }
  }

  return $return;
}

1293
/**
1294
 * Gets the value of a variable from the database during 7.x-8.x upgrades.
1295 1296 1297 1298 1299 1300 1301 1302 1303 1304 1305 1306 1307 1308 1309 1310