diff core/lib/Drupal/Core/Cache/DatabaseBackend.php @ 0:4c8ae668cc8c

Initial import (non-working)

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/core/lib/Drupal/Core/Cache/DatabaseBackend.php	Wed Nov 29 16:09:58 2017 +0000
@@ -0,0 +1,537 @@
+<?php
+
+namespace Drupal\Core\Cache;
+
+use Drupal\Component\Utility\Crypt;
+use Drupal\Core\Database\Connection;
+use Drupal\Core\Database\SchemaObjectExistsException;
+
+/**
+ * Defines a default cache implementation.
+ *
+ * This is Drupal's default cache implementation. It uses the database to store
+ * cached data. Each cache bin corresponds to a database table by the same name.
+ *
+ * @ingroup cache
+ */
+class DatabaseBackend implements CacheBackendInterface {
+
+  /**
+   * The default maximum number of rows that this cache bin table can store.
+   *
+   * This maximum is introduced to ensure that the database is not filled with
+   * hundred of thousand of cache entries with gigabytes in size.
+   *
+   * Read about how to change it in the @link cache Cache API topic. @endlink
+   */
+  const DEFAULT_MAX_ROWS = 5000;
+
+  /**
+   * -1 means infinite allows numbers of rows for the cache backend.
+   */
+  const MAXIMUM_NONE = -1;
+
+  /**
+   * The maximum number of rows that this cache bin table is allowed to store.
+   *
+   * @see ::MAXIMUM_NONE
+   *
+   * @var int
+   */
+  protected $maxRows;
+
+  /**
+   * @var string
+   */
+  protected $bin;
+
+
+  /**
+   * The database connection.
+   *
+   * @var \Drupal\Core\Database\Connection
+   */
+  protected $connection;
+
+  /**
+   * The cache tags checksum provider.
+   *
+   * @var \Drupal\Core\Cache\CacheTagsChecksumInterface
+   */
+  protected $checksumProvider;
+
+  /**
+   * Constructs a DatabaseBackend object.
+   *
+   * @param \Drupal\Core\Database\Connection $connection
+   *   The database connection.
+   * @param \Drupal\Core\Cache\CacheTagsChecksumInterface $checksum_provider
+   *   The cache tags checksum provider.
+   * @param string $bin
+   *   The cache bin for which the object is created.
+   * @param int $max_rows
+   *   (optional) The maximum number of rows that are allowed in this cache bin
+   *   table.
+   */
+  public function __construct(Connection $connection, CacheTagsChecksumInterface $checksum_provider, $bin, $max_rows = NULL) {
+    // All cache tables should be prefixed with 'cache_'.
+    $bin = 'cache_' . $bin;
+
+    $this->bin = $bin;
+    $this->connection = $connection;
+    $this->checksumProvider = $checksum_provider;
+    $this->maxRows = $max_rows === NULL ? static::DEFAULT_MAX_ROWS : $max_rows;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function get($cid, $allow_invalid = FALSE) {
+    $cids = [$cid];
+    $cache = $this->getMultiple($cids, $allow_invalid);
+    return reset($cache);
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getMultiple(&$cids, $allow_invalid = FALSE) {
+    $cid_mapping = [];
+    foreach ($cids as $cid) {
+      $cid_mapping[$this->normalizeCid($cid)] = $cid;
+    }
+    // When serving cached pages, the overhead of using ::select() was found
+    // to add around 30% overhead to the request. Since $this->bin is a
+    // variable, this means the call to ::query() here uses a concatenated
+    // string. This is highly discouraged under any other circumstances, and
+    // is used here only due to the performance overhead we would incur
+    // otherwise. When serving an uncached page, the overhead of using
+    // ::select() is a much smaller proportion of the request.
+    $result = [];
+    try {
+      $result = $this->connection->query('SELECT cid, data, created, expire, serialized, tags, checksum FROM {' . $this->connection->escapeTable($this->bin) . '} WHERE cid IN ( :cids[] ) ORDER BY cid', [':cids[]' => array_keys($cid_mapping)]);
+    }
+    catch (\Exception $e) {
+      // Nothing to do.
+    }
+    $cache = [];
+    foreach ($result as $item) {
+      // Map the cache ID back to the original.
+      $item->cid = $cid_mapping[$item->cid];
+      $item = $this->prepareItem($item, $allow_invalid);
+      if ($item) {
+        $cache[$item->cid] = $item;
+      }
+    }
+    $cids = array_diff($cids, array_keys($cache));
+    return $cache;
+  }
+
+  /**
+   * Prepares a cached item.
+   *
+   * Checks that items are either permanent or did not expire, and unserializes
+   * data as appropriate.
+   *
+   * @param object $cache
+   *   An item loaded from cache_get() or cache_get_multiple().
+   * @param bool $allow_invalid
+   *   If FALSE, the method returns FALSE if the cache item is not valid.
+   *
+   * @return mixed|false
+   *   The item with data unserialized as appropriate and a property indicating
+   *   whether the item is valid, or FALSE if there is no valid item to load.
+   */
+  protected function prepareItem($cache, $allow_invalid) {
+    if (!isset($cache->data)) {
+      return FALSE;
+    }
+
+    $cache->tags = $cache->tags ? explode(' ', $cache->tags) : [];
+
+    // Check expire time.
+    $cache->valid = $cache->expire == Cache::PERMANENT || $cache->expire >= REQUEST_TIME;
+
+    // Check if invalidateTags() has been called with any of the items's tags.
+    if (!$this->checksumProvider->isValid($cache->checksum, $cache->tags)) {
+      $cache->valid = FALSE;
+    }
+
+    if (!$allow_invalid && !$cache->valid) {
+      return FALSE;
+    }
+
+    // Unserialize and return the cached data.
+    if ($cache->serialized) {
+      $cache->data = unserialize($cache->data);
+    }
+
+    return $cache;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function set($cid, $data, $expire = Cache::PERMANENT, array $tags = []) {
+    $this->setMultiple([
+      $cid => [
+        'data' => $data,
+        'expire' => $expire,
+        'tags' => $tags,
+      ],
+    ]);
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function setMultiple(array $items) {
+    $try_again = FALSE;
+    try {
+      // The bin might not yet exist.
+      $this->doSetMultiple($items);
+    }
+    catch (\Exception $e) {
+      // If there was an exception, try to create the bins.
+      if (!$try_again = $this->ensureBinExists()) {
+        // If the exception happened for other reason than the missing bin
+        // table, propagate the exception.
+        throw $e;
+      }
+    }
+    // Now that the bin has been created, try again if necessary.
+    if ($try_again) {
+      $this->doSetMultiple($items);
+    }
+  }
+
+  /**
+   * Stores multiple items in the persistent cache.
+   *
+   * @param array $items
+   *   An array of cache items, keyed by cid.
+   *
+   * @see \Drupal\Core\Cache\CacheBackendInterface::setMultiple()
+   */
+  protected function doSetMultiple(array $items) {
+    $values = [];
+
+    foreach ($items as $cid => $item) {
+      $item += [
+        'expire' => CacheBackendInterface::CACHE_PERMANENT,
+        'tags' => [],
+      ];
+
+      assert('\Drupal\Component\Assertion\Inspector::assertAllStrings($item[\'tags\'])', 'Cache Tags must be strings.');
+      $item['tags'] = array_unique($item['tags']);
+      // Sort the cache tags so that they are stored consistently in the DB.
+      sort($item['tags']);
+
+      $fields = [
+        'cid' => $this->normalizeCid($cid),
+        'expire' => $item['expire'],
+        'created' => round(microtime(TRUE), 3),
+        'tags' => implode(' ', $item['tags']),
+        'checksum' => $this->checksumProvider->getCurrentChecksum($item['tags']),
+      ];
+
+      if (!is_string($item['data'])) {
+        $fields['data'] = serialize($item['data']);
+        $fields['serialized'] = 1;
+      }
+      else {
+        $fields['data'] = $item['data'];
+        $fields['serialized'] = 0;
+      }
+      $values[] = $fields;
+    }
+
+    // Use an upsert query which is atomic and optimized for multiple-row
+    // merges.
+    $query = $this->connection
+      ->upsert($this->bin)
+      ->key('cid')
+      ->fields(['cid', 'expire', 'created', 'tags', 'checksum', 'data', 'serialized']);
+    foreach ($values as $fields) {
+      // Only pass the values since the order of $fields matches the order of
+      // the insert fields. This is a performance optimization to avoid
+      // unnecessary loops within the method.
+      $query->values(array_values($fields));
+    }
+
+    $query->execute();
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function delete($cid) {
+    $this->deleteMultiple([$cid]);
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function deleteMultiple(array $cids) {
+    $cids = array_values(array_map([$this, 'normalizeCid'], $cids));
+    try {
+      // Delete in chunks when a large array is passed.
+      foreach (array_chunk($cids, 1000) as $cids_chunk) {
+        $this->connection->delete($this->bin)
+          ->condition('cid', $cids_chunk, 'IN')
+          ->execute();
+      }
+    }
+    catch (\Exception $e) {
+      // Create the cache table, which will be empty. This fixes cases during
+      // core install where a cache table is cleared before it is set
+      // with {cache_render} and {cache_data}.
+      if (!$this->ensureBinExists()) {
+        $this->catchException($e);
+      }
+    }
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function deleteAll() {
+    try {
+      $this->connection->truncate($this->bin)->execute();
+    }
+    catch (\Exception $e) {
+      // Create the cache table, which will be empty. This fixes cases during
+      // core install where a cache table is cleared before it is set
+      // with {cache_render} and {cache_data}.
+      if (!$this->ensureBinExists()) {
+        $this->catchException($e);
+      }
+    }
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function invalidate($cid) {
+    $this->invalidateMultiple([$cid]);
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function invalidateMultiple(array $cids) {
+    $cids = array_values(array_map([$this, 'normalizeCid'], $cids));
+    try {
+      // Update in chunks when a large array is passed.
+      foreach (array_chunk($cids, 1000) as $cids_chunk) {
+        $this->connection->update($this->bin)
+          ->fields(['expire' => REQUEST_TIME - 1])
+          ->condition('cid', $cids_chunk, 'IN')
+          ->execute();
+      }
+    }
+    catch (\Exception $e) {
+      $this->catchException($e);
+    }
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function invalidateAll() {
+    try {
+      $this->connection->update($this->bin)
+        ->fields(['expire' => REQUEST_TIME - 1])
+        ->execute();
+    }
+    catch (\Exception $e) {
+      $this->catchException($e);
+    }
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function garbageCollection() {
+    try {
+      // Bounded size cache bin, using FIFO.
+      if ($this->maxRows !== static::MAXIMUM_NONE) {
+        $first_invalid_create_time = $this->connection->select($this->bin)
+          ->fields($this->bin, ['created'])
+          ->orderBy("{$this->bin}.created", 'DESC')
+          ->range($this->maxRows, $this->maxRows + 1)
+          ->execute()
+          ->fetchField();
+
+        if ($first_invalid_create_time) {
+          $this->connection->delete($this->bin)
+            ->condition('created', $first_invalid_create_time, '<=')
+            ->execute();
+        }
+      }
+
+      $this->connection->delete($this->bin)
+        ->condition('expire', Cache::PERMANENT, '<>')
+        ->condition('expire', REQUEST_TIME, '<')
+        ->execute();
+    }
+    catch (\Exception $e) {
+      // If the table does not exist, it surely does not have garbage in it.
+      // If the table exists, the next garbage collection will clean up.
+      // There is nothing to do.
+    }
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function removeBin() {
+    try {
+      $this->connection->schema()->dropTable($this->bin);
+    }
+    catch (\Exception $e) {
+      $this->catchException($e);
+    }
+  }
+
+  /**
+   * Check if the cache bin exists and create it if not.
+   */
+  protected function ensureBinExists() {
+    try {
+      $database_schema = $this->connection->schema();
+      if (!$database_schema->tableExists($this->bin)) {
+        $schema_definition = $this->schemaDefinition();
+        $database_schema->createTable($this->bin, $schema_definition);
+        return TRUE;
+      }
+    }
+    // If another process has already created the cache table, attempting to
+    // recreate it will throw an exception. In this case just catch the
+    // exception and do nothing.
+    catch (SchemaObjectExistsException $e) {
+      return TRUE;
+    }
+    return FALSE;
+  }
+
+  /**
+   * Act on an exception when cache might be stale.
+   *
+   * If the table does not yet exist, that's fine, but if the table exists and
+   * yet the query failed, then the cache is stale and the exception needs to
+   * propagate.
+   *
+   * @param $e
+   *   The exception.
+   * @param string|null $table_name
+   *   The table name. Defaults to $this->bin.
+   *
+   * @throws \Exception
+   */
+  protected function catchException(\Exception $e, $table_name = NULL) {
+    if ($this->connection->schema()->tableExists($table_name ?: $this->bin)) {
+      throw $e;
+    }
+  }
+
+  /**
+   * Normalizes a cache ID in order to comply with database limitations.
+   *
+   * @param string $cid
+   *   The passed in cache ID.
+   *
+   * @return string
+   *   An ASCII-encoded cache ID that is at most 255 characters long.
+   */
+  protected function normalizeCid($cid) {
+    // Nothing to do if the ID is a US ASCII string of 255 characters or less.
+    $cid_is_ascii = mb_check_encoding($cid, 'ASCII');
+    if (strlen($cid) <= 255 && $cid_is_ascii) {
+      return $cid;
+    }
+    // Return a string that uses as much as possible of the original cache ID
+    // with the hash appended.
+    $hash = Crypt::hashBase64($cid);
+    if (!$cid_is_ascii) {
+      return $hash;
+    }
+    return substr($cid, 0, 255 - strlen($hash)) . $hash;
+  }
+
+  /**
+   * Defines the schema for the {cache_*} bin tables.
+   *
+   * @internal
+   */
+  public function schemaDefinition() {
+    $schema = [
+      'description' => 'Storage for the cache API.',
+      'fields' => [
+        'cid' => [
+          'description' => 'Primary Key: Unique cache ID.',
+          'type' => 'varchar_ascii',
+          'length' => 255,
+          'not null' => TRUE,
+          'default' => '',
+          'binary' => TRUE,
+        ],
+        'data' => [
+          'description' => 'A collection of data to cache.',
+          'type' => 'blob',
+          'not null' => FALSE,
+          'size' => 'big',
+        ],
+        'expire' => [
+          'description' => 'A Unix timestamp indicating when the cache entry should expire, or ' . Cache::PERMANENT . ' for never.',
+          'type' => 'int',
+          'not null' => TRUE,
+          'default' => 0,
+        ],
+        'created' => [
+          'description' => 'A timestamp with millisecond precision indicating when the cache entry was created.',
+          'type' => 'numeric',
+          'precision' => 14,
+          'scale' => 3,
+          'not null' => TRUE,
+          'default' => 0,
+        ],
+        'serialized' => [
+          'description' => 'A flag to indicate whether content is serialized (1) or not (0).',
+          'type' => 'int',
+          'size' => 'small',
+          'not null' => TRUE,
+          'default' => 0,
+        ],
+        'tags' => [
+          'description' => 'Space-separated list of cache tags for this entry.',
+          'type' => 'text',
+          'size' => 'big',
+          'not null' => FALSE,
+        ],
+        'checksum' => [
+          'description' => 'The tag invalidation checksum when this entry was saved.',
+          'type' => 'varchar_ascii',
+          'length' => 255,
+          'not null' => TRUE,
+        ],
+      ],
+      'indexes' => [
+        'expire' => ['expire'],
+        'created' => ['created'],
+      ],
+      'primary key' => ['cid'],
+    ];
+    return $schema;
+  }
+
+  /**
+   * The maximum number of rows that this cache bin table is allowed to store.
+   *
+   * @return int
+   */
+  public function getMaxRows() {
+    return $this->maxRows;
+  }
+
+}