drupal/modules/comment/comment.install

<?php
// $Id$

/**
 * Implementation of hook_enable().
 */
function comment_enable() {
  // Insert records into the node_comment_statistics for nodes that are missing.
  db_query("INSERT INTO {node_comment_statistics} (nid, last_comment_timestamp, last_comment_name, last_comment_uid, comment_count) SELECT n.nid, n.changed, NULL, n.uid, 0 FROM {node} n LEFT JOIN {node_comment_statistics} c ON n.nid = c.nid WHERE c.comment_count IS NULL");
}

/**
 * Changed node_comment_statistics to use node->changed to avoid future
 * timestamps.
 */
function comment_update_1() {
  // Change any future last comment timestamps to now.
  db_query('UPDATE {node_comment_statistics} SET last_comment_timestamp = %d WHERE last_comment_timestamp > %d', time(), time());

  // Unstuck node indexing timestamp if needed.
  if (($last = variable_get('node_cron_last', FALSE)) !== FALSE) {
    variable_set('node_cron_last', min(time(), $last));
  }
  return array();
}

/**
 * Implementation of hook_schema().
 */
function comment_schema() {
  $schema['comments'] = array(
    'description' => t('Stores comments and associated data.'),
    'fields' => array(
      'cid' => array(
        'type' => 'serial',
        'not null' => TRUE,
        'description' => t('Primary Key: Unique comment ID.'),
      ),
      'pid' => array(
        'type' => 'int',
        'not null' => TRUE,
        'default' => 0,
        'description' => t('The {comments}.cid to which this comment is a reply. If set to 0, this comment is not a reply to an existing comment.'),
      ),
      'nid' => array(
        'type' => 'int',
        'not null' => TRUE,
        'default' => 0,
        'description' => t('The {node}.nid to which this comment is a reply.'),
      ),
      'uid' => array(
        'type' => 'int',
        'not null' => TRUE,
        'default' => 0,
        'description' => t('The {users}.uid who authored the comment. If set to 0, this comment was created by an anonymous user.'),
      ),
      'subject' => array(
        'type' => 'varchar',
        'length' => 64,
        'not null' => TRUE,
        'default' => '',
        'description' => t('The comment title.'),
      ),
      'comment' => array(
        'type' => 'text',
        'not null' => TRUE,
        'size' => 'big',
        'description' => t('The comment body.'),
      ),
      'hostname' => array(
        'type' => 'varchar',
        'length' => 128,
        'not null' => TRUE,
        'default' => '',
        'description' => t("The author's host name."),
      ),
      'timestamp' => array(
        'type' => 'int',
        'not null' => TRUE,
        'default' => 0,
        'description' => t('The time that the comment was created, or last edited by its author, as a Unix timestamp.'),
      ),
      'status' => array(
        'type' => 'int',
        'unsigned' => TRUE,
        'not null' => TRUE,
        'default' => 0,
        'size' => 'tiny',
        'description' => t('The published status of a comment. (0 = Published, 1 = Not Published)'),
      ),
      'format' => array(
        'type' => 'int',
        'size' => 'small',
        'not null' => TRUE,
        'default' => 0,
        'description' => t('The {filter_formats}.format of the comment body.'),
      ),
      'thread' => array(
        'type' => 'varchar',
        'length' => 255,
        'not null' => TRUE,
        'description' => t("The vancode representation of the comment's place in a thread."),
      ),
      'name' => array(
        'type' => 'varchar',
        'length' => 60,
        'not null' => FALSE,
        'description' => t("The comment author's name. Uses {users}.name if the user is logged in, otherwise uses the value typed into the comment form."),
      ),
      'mail' => array(
        'type' => 'varchar',
        'length' => 64,
        'not null' => FALSE,
        'description' => t("The comment author's e-mail address from the comment form, if user is anonymous, and the 'Anonymous users may/must leave their contact information' setting is turned on."),
      ),
      'homepage' => array(
        'type' => 'varchar',
        'length' => 255,
        'not null' => FALSE,
        'description' => t("The comment author's home page address from the comment form, if user is anonymous, and the 'Anonymous users may/must leave their contact information' setting is turned on."),
      )
    ),
    'indexes' => array(
      'nid'    => array('nid'),
      'status' => array('status')
    ),
    'primary key' => array('cid'),
  );

    $schema['node_comment_statistics'] = array(
     'description' => t('Maintains statistics of node and comments posts to show "new" and "updated" flags.'),
      'fields' => array(
       'nid' => array(
         'type' => 'int',
         'unsigned' => TRUE,
         'not null' => TRUE,
         'default' => 0,
         'description' => t('The {node}.nid for which the statistics are compiled.'),
       ),
       'last_comment_timestamp' => array(
         'type' => 'int',
         'not null' => TRUE,
         'default' => 0,
         'description' => t('The Unix timestamp of the last comment that was posted within this node, from {comments}.timestamp.'),
       ),
       'last_comment_name' => array(
         'type' => 'varchar',
         'length' => 60,
         'not null' => FALSE,
         'description' => t('The name of the latest author to post a comment on this node, from {comments}.name.'),
       ),
       'last_comment_uid' => array(
         'type' => 'int',
         'not null' => TRUE,
         'default' => 0,
         'description' => t('The user ID of the latest author to post a comment on this node, from {comments}.uid.'),
       ),
       'comment_count' => array(
         'type' => 'int',
         'unsigned' => TRUE,
         'not null' => TRUE,
         'default' => 0,
         'description' => t('The total number of comments on this node.'),
       ),
      ),
      'indexes' => array('node_comment_timestamp' => array('last_comment_timestamp')),
      'primary key' => array('nid'),
  );

  return $schema;
}