drupal/core/modules/history/history.install

<?php

/**
 * @file
 * Installation functions for History module.
 */

/**
 * Implements hook_schema().
 */
function history_schema() {
  $schema['history'] = [
    'description' => 'A record of which {users} have read which {node}s.',
    'fields' => [
      'uid' => [
        'description' => 'The {users}.uid that read the {node} nid.',
        'type' => 'int',
        'not null' => TRUE,
        'default' => 0,
      ],
      'nid' => [
        'description' => 'The {node}.nid that was read.',
        'type' => 'int',
        'unsigned' => TRUE,
        'not null' => TRUE,
        'default' => 0,
      ],
      'timestamp' => [
        'description' => 'The Unix timestamp at which the read occurred.',
        'type' => 'int',
        'not null' => TRUE,
        'default' => 0,
        'size' => 'big',
      ],
    ],
    'primary key' => ['uid', 'nid'],
    'indexes' => [
      'nid' => ['nid'],
    ],
  ];

  return $schema;
}

/**
 * Implements hook_update_last_removed().
 */
function history_update_last_removed() {
  return 10100;
}