Uploaded image for project: 'MariaDB Server'
  1. MariaDB Server
  2. MDEV-29264

JSON function overflow error based on LONGTEXT field

    XMLWordPrintable

    Details

      Description

      Hi, I'm GSoC 2022 contributor, I'm working on the MCOL-785.
      Now I have a problem: The JSON Function result is truncated when the function is called based on LONGTEXT field.

      Take the JSON_ARRAY as an example:

      MariaDB root@(none):test> create table t1(t TEXT, l LONGTEXT) engine=columnstore;
      Query OK, 0 rows affected
      Time: 0.147s
      MariaDB root@(none):test> insert into t1 values('key1', 'key1');
      Query OK, 1 row affected
      Time: 0.179s
      MariaDB root@(none):test> select json_array(t), json_array(l) from t1;
      +---------------+---------------+
      | json_array(t) | json_array(l) |
      +---------------+---------------+
      | ["key1"]      | ["key         |
      +---------------+---------------+
      1 row in set
      Time: 0.097s
      MariaDB root@(none):test>
      

      After debugging, I found that such difference is caused by overflow error.

      bool Item_func_json_array::fix_length_and_dec(THD *thd)
      {
        ulonglong char_length= 2;
      ...
        for (n_arg=0 ; n_arg < arg_count ; n_arg++)
          char_length+= args[n_arg]->max_char_length() + 4;
      ...
      }
      

      First, the return type of args[n_arg]- >max_char_length() is uint32, the max value of uint32 is 4,294,967,295.
      When called based on LONGTEXT, the result of args[n_arg]- >max_char_length() is 4,294,967,295(Maximum value of LONGTEXT). So args[n_arg]->max_char_length()+4 will be 3 due to overflow. And there is no overflow when calling based on TEXT.

      I will make a patch to this issue. I would be very grateful if you can handle it soon.

      same issues exist in JSON_OBJECT, JSON_ARRAY_APPEND(INSERT), JSON_INSERT(REPLACE|SET)

        Attachments

          Activity

            People

            Assignee:
            rucha174 Rucha Deodhar
            Reporter:
            lunar_land ziyitan
            Votes:
            0 Vote for this issue
            Watchers:
            1 Start watching this issue

              Dates

              Created:
              Updated:
              Resolved:

                Git Integration

                Error rendering 'com.xiplink.jira.git.jira_git_plugin:git-issue-webpanel'. Please contact your Jira administrators.