UserStorageSchema.php

<?php

namespace Drupal\user;

use Drupal\Core\Entity\ContentEntityTypeInterface;
use Drupal\Core\Entity\Sql\SqlContentEntityStorageSchema;
use Drupal\Core\Field\FieldStorageDefinitionInterface;

/**
 * Defines the user schema handler.
 */
class UserStorageSchema extends SqlContentEntityStorageSchema {
  
  /**
   * {@inheritdoc}
   */
  protected function getEntitySchema(ContentEntityTypeInterface $entity_type, $reset = FALSE) {
    $schema = parent::getEntitySchema($entity_type, $reset);
    if ($data_table = $this->storage
      ->getDataTable()) {
      $schema[$data_table]['unique keys'] += [
        'user__name' => [
          'name',
          'langcode',
        ],
      ];
    }
    return $schema;
  }
  
  /**
   * {@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 == 'users_field_data') {
      switch ($field_name) {
        case 'name':
          // Improves the performance of the user__name index defined
          // in getEntitySchema().
          $schema['fields'][$field_name]['not null'] = TRUE;
          // Make sure the field is no longer than 191 characters so we can
          // add a unique constraint in MySQL.
          $schema['fields'][$field_name]['length'] = UserInterface::USERNAME_MAX_LENGTH;
          break;

        case 'mail':
          $this->addSharedTableFieldIndex($storage_definition, $schema);
          break;

        case 'access':
        case 'created':
          $this->addSharedTableFieldIndex($storage_definition, $schema, TRUE);
          break;

      }
    }
    return $schema;
  }

}