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Displaying posts with tag: bug (reset)

On responsible bugs reporting
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Let me start with questions related to responsible MySQL bugs reporting that I'd like to be discussed and then present a history behind them.

Assuming that you, my dear reader from MySQL Community, noted or found some simple sequence of SQL statements that, when executed by authenticated MySQL user explicitly having all the privileges needed to execute these statements, crashes some version of your favorite MySQL fork, please, answer the following questions:
  • Do you consider this kind of a bug a "security vulnerability"?
  • Should you share complete test case at any public site (MySQL bugs database, Facebook, your personal blog, any)?
  • Should you share just a description of possible "attack vector", as Oracle does when they publish security bug fixes?
  • Should you share just a stack trace or failed assertion information,



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    Recalculating InnoDB Persistent Statistics - a Story of the Bug Report
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    One of the first posts in this blog was about reporting MySQL bugs "properly", in a way that maximizes chances for it to be processed really soon. I had written the following there:
    "Ideally, you should provide a complete test case and/or instructions that any reader can use to reproduce your problem"
    Indeed, if one can just copy/paste something to mysql command line client or run some file attached to see the problem, chances are high for the bug to be processed really soon. We all like to get low hanging fruits from time to time, and Oracle engineers who work on bugs are not exceptions. But does this mean that bug without clear test case has no value and is going to be ignored?

    It should NOT be the case. Let's


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    New MySQL 5.6-Feature host_cache_size does not work
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    Today as i was learning for the new MySQL 5.6-certification (more about that in a later post) i stumbled again across the host_cache-Table that was added to MySQL in 5.6.5. Before that you had no chance to check which hosts are already known by the MySQL-server.

    So thats a pretty good feature for us. And even better: you could resize the size of the host_cache now! Whoohoo, awesome! As we have a lot of servers that need to connect to one of our MySQL-server and we could not switch to ip-based-authentication we were really happy to tune the host_cache-size without recompiling MySQL.

    Unfortunately i noticed that the performance_schema.host_cache table only holds 128 rows and that the content was changing everytime i checked. So i logged in to a server that wasn’t already in the host_cache-table, made a connection attempt to the mysql server

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    phpMyAdmin breaks Replication in MySQL 5.6
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    Recently i updated to MySQL 5.6 and we were really excited about the very good overall performance. But beside a major bug concerning wrong results when running a SELECT that includes a HAVING based on a function (see http://bugs.mysql.com/bug.php?id=69638) we also noticed that from time to time the replication breaks with the following error:

    Last_SQL_Errno: 1590
    Last_SQL_Error: The incident LOST_EVENTS occured on the master. Message: error writing to the binary log

    After some investigation it seemed like this happens if one modifies some user privileges, so we stumbled upon http://bugs.mysql.com/bug.php?id=68892.

    Essentially the bug report says that if you use the wrong syntax for GRANT-statements the

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    Fix for INFORMATION_SCHEMA.PARTITIONS losing table stats
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    Here is a fix for the MySQL/TokuDB/MariaDB bug I reported earlier today.  I think this fix is correct (it is only one line) but I don’t delve into the storage engine very often (and particularly not into ha_partition.cc) so I think it would be good to wait for Oracle (or Percona, MariaDB, or Tokutek) to validate that it is correct before using it.

    diff -u ha_partition.cc /tmp/ha_partition.cc 
    --- ha_partition.cc 2013-04-05 05:27:18.000000000 -0700
    +++ /tmp/ha_partition.cc 2013-05-27 02:45:01.680676228 -0700
    @@ -6455,9 +6455,11 @@
    void ha_partition::get_dynamic_partition_info(PARTITION_STATS *stat_info,
    uint part_id)
    {
    +
    handler *file= m_file[part_id];
    DBUG_ASSERT(bitmap_is_set(&(m_part_info->read_partitions), part_id));
    - file->info(HA_STATUS_CONST | HA_STATUS_TIME | HA_STATUS_VARIABLE |
    + 
    + info(HA_STATUS_CONST |
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    xtrabackup_51: not found & no ‘mysqld’ group in MySQL options
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    Recently I happen to setup a new MySQL instance with my tools – a standard MySQL 5.1+, xtrabackup setup and last-hotbackup.tar.gz. To restore from the backup we used xtrabackup binaries and ran into issues following standard commands (assuming no changes): To prepare the backup I used apply-log as follows: $] innobackupex-1.5.1 --defaults-file=/usr/local/mysql/data/backup-my.cnf --apply-log  /usr/local/mysql/data --ibbackup […]
    Got a packet bigger than ‘slave_max_allowed_packet’ bytes and binlog_format = STATEMENT | MIXED
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    Got a packet bigger than ‘slave_max_allowed_packet’ bytes and binlog_format=STATEMENT|MIXED

    Since version 5.1.64 MySQL introduces a new variable named slave_max_allowed_packet, which was introduced to allow large updates using row-based replication do not cause replication to fail when exceeded max_allowed_packet.

    The problem is if you have you replication using binlog_format=STATEMENT or binlog_format=MIXED it ignores this option and use as

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    Maximum Open Files
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    Recently I was discussing with some colleagues the possibility of consolidating some MySQL servers. While the servers are not heavily loading (averaging less than 1,000 queries a second) they are pretty large in terms of storage requirements. Each server has roughly 200 databases on each with approximatley 50 tables. Thats 10,000 tables per server.  Each server contains up to 1 terabyte of data so if you consolidated servers at a 10:1 ratio you would have 10 terabytes of data, 2,000 databases and 100,000 tables with 10,000 queries per second average load.

     

    Alright, that's a lot. And without testing I don't know if it would work. It probably wouldn't.  But it might. And if it did, it would save the company a significant amount of money.  But, while discussing this,  someone brought up that open files limit might be a

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    IOUG Podcast 24-AUG-2012 Rumors of MySQL’s Doom by Oracle / Design Piracy
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    For the week of August 24th, 2012: Everybody’s Preparing for OpenWorld Dispelling the Rumors of MySQL’s Impending Doom On Piracy of Design IOUG Podcast 24-AUG-2012 Rumors of MySQL’s Doom by Oracle / Design Piracy Subscribe to this Podcast (RSS) or … Continue reading →
    Nasty InnoDB regression in MySQL 5.5.25
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    We just ran into a nasty InnoDB bug that only seems to exist in MySQL 5.5.25:

    An InnoDB update that modifies a rows primary key can trigger some recursive behavior that creates new rows until all disk space is exceeded. This does not affect all primary key updates in general but only gets triggered when a few other conditions are also met, so you're not too likely to run into it, but if you do your mysqld server will waste a lot of IO bandwidth and storage space on this and will usually eventually run out of disk space.

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