DatabaseCacheTagsChecksum.php

<?php

namespace Drupal\Core\Cache;

use Drupal\Core\Database\Connection;
use Drupal\Core\Database\DatabaseException;

/**
 * Cache tags invalidations checksum implementation that uses the database.
 */
class DatabaseCacheTagsChecksum implements CacheTagsChecksumInterface, CacheTagsInvalidatorInterface {
    use CacheTagsChecksumTrait;
    
    /**
     * The database connection.
     *
     * @var \Drupal\Core\Database\Connection
     */
    protected $connection;
    
    /**
     * Constructs a DatabaseCacheTagsChecksum object.
     *
     * @param \Drupal\Core\Database\Connection $connection
     *   The database connection.
     */
    public function __construct(Connection $connection) {
        $this->connection = $connection;
    }
    
    /**
     * {@inheritdoc}
     */
    protected function doInvalidateTags(array $tags) {
        try {
            foreach ($tags as $tag) {
                $this->connection
                    ->merge('cachetags')
                    ->insertFields([
                    'invalidations' => 1,
                ])
                    ->expression('invalidations', '[invalidations] + 1')
                    ->key('tag', $tag)
                    ->execute();
            }
        } catch (\Exception $e) {
            // Create the cache table, which will be empty. This fixes cases during
            // core install where cache tags are invalidated before the table is
            // created.
            if (!$this->ensureTableExists()) {
                throw $e;
            }
        }
    }
    
    /**
     * {@inheritdoc}
     */
    protected function getTagInvalidationCounts(array $tags) {
        try {
            return $this->connection
                ->query('SELECT [tag], [invalidations] FROM {cachetags} WHERE [tag] IN ( :tags[] )', [
                ':tags[]' => $tags,
            ])
                ->fetchAllKeyed();
        } catch (\Exception $e) {
            // If the table does not exist yet, create.
            if (!$this->ensureTableExists()) {
                throw $e;
            }
        }
        return [];
    }
    
    /**
     * Check if the cache tags table exists and create it if not.
     */
    protected function ensureTableExists() {
        try {
            $database_schema = $this->connection
                ->schema();
            $schema_definition = $this->schemaDefinition();
            $database_schema->createTable('cachetags', $schema_definition);
        } catch (DatabaseException $e) {
        } catch (\Exception $e) {
            return FALSE;
        }
        return TRUE;
    }
    
    /**
     * Defines the schema for the {cachetags} table.
     *
     * @internal
     */
    public function schemaDefinition() {
        $schema = [
            'description' => 'Cache table for tracking cache tag invalidations.',
            'fields' => [
                'tag' => [
                    'description' => 'Namespace-prefixed tag string.',
                    'type' => 'varchar_ascii',
                    'length' => 255,
                    'not null' => TRUE,
                    'default' => '',
                ],
                'invalidations' => [
                    'description' => 'Number incremented when the tag is invalidated.',
                    'type' => 'int',
                    'not null' => TRUE,
                    'default' => 0,
                ],
            ],
            'primary key' => [
                'tag',
            ],
        ];
        return $schema;
    }
    
    /**
     * {@inheritdoc}
     */
    public function getDatabaseConnection() {
        return $this->connection;
    }

}