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- <?php
- namespace Drupal\Core\Cache;
- use Drupal\Component\Assertion\Inspector;
- 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) {
- $item += [
- 'expire' => CacheBackendInterface::CACHE_PERMANENT,
- 'tags' => [],
- ];
- assert(Inspector::assertAllStrings($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;
- }
- }
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