Function handle_grant_table

sql/sql_acl.cc:10485–10615

*/

static int handle_grant_table(THD *thd, const Grant_table_base& grant_table,
                              enum enum_acl_tables which_table, bool drop,
                              LEX_USER *user_from, LEX_USER *user_to)
{
  int result= 0;
  int error;
  TABLE *table= grant_table.table();
  DBUG_ENTER("handle_grant_table");
  if (!table)
    DBUG_RETURN(0);

  Field *host_field= table->field[0];
  Field *user_field= table->field[which_table == USER_TABLE ||
                                  which_table == PROXIES_PRIV_TABLE ? 1 : 2];
  uchar user_key[MAX_KEY_LENGTH];
  uint key_prefix_length;

  if (which_table == ROLES_MAPPING_TABLE)
  {
    result= handle_roles_mappings_table(table, drop, user_from, user_to);
    DBUG_RETURN(result);
  }

  table->use_all_columns();
  if (which_table == USER_TABLE) // mysql.user table
  {
    /*
      The 'user' table has an unique index on (host, user).
      Thus, we can handle everything with a single index access.
      The host- and user fields are consecutive in the user table records.
      So we set host- and user fields of table->record[0] and use the
      pointer to the host field as key.
      index_read_idx() will replace table->record[0] (its first argument)
      by the searched record, if it exists.
    */
    DBUG_PRINT("info",("read table: '%s'  search: '%s'@'%s'",
                       table->s->table_name.str,
                       user_from->user.str, user_from->host.str));
    host_field->store(user_from->host, system_charset_info);
    user_field->store(user_from->user, system_charset_info);

    key_prefix_length= (table->key_info->key_part[0].store_length +
                        table->key_info->key_part[1].store_length);
    key_copy(user_key, table->record[0], table->key_info, key_prefix_length);

    error= table->file->ha_index_read_idx_map(table->record[0], 0,
                                              user_key, (key_part_map)3,
                                              HA_READ_KEY_EXACT);
    if (!unlikely(error) && !*user_from->host.str)
    {
      // verify that we got a role or a user, as needed
      if (static_cast<const User_table&>(grant_table).get_is_role() !=
          user_from->is_role())
        error= HA_ERR_KEY_NOT_FOUND;
    }
    if (unlikely(error))
    {
      if (error != HA_ERR_KEY_NOT_FOUND && error != HA_ERR_END_OF_FILE)