class FileStorageSchema

class FileStorageSchema extends SqlContentEntityStorageSchema {
    
    /**
     * {@inheritdoc}
     */
    protected function getSharedTableFieldSchema(FieldStorageDefinitionInterface $storage_definition, $table_name, array $column_mapping) {
        $schema = parent::getSharedTableFieldSchema($storage_definition, $table_name, $column_mapping);
        $field_name = $storage_definition->getName();
        if ($table_name == $this->storage
            ->getBaseTable()) {
            switch ($field_name) {
                case 'status':
                case 'changed':
                case 'uri':
                    $this->addSharedTableFieldIndex($storage_definition, $schema, TRUE);
                    break;
            }
        }
        // Entity keys automatically have not null assigned to TRUE, but for the
        // file entity, NULL is a valid value for uid.
        if ($field_name === 'uid') {
            $schema['fields']['uid']['not null'] = FALSE;
        }
        return $schema;
    }

}