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In 5.5, a crashing, regression bug exists if you use SELECT COUNT(DISTINCT) *and* one of the WHERE operands is in the Primary Key (or just a unique index).

This simple crash (if only one row is in the table) will crash mysqld.

Of course I’ve filed a bug report, but that has been nearly 3 months and no updates yet.

Here is the bug I filed (which you won’t be able to view):

http://bugs.mysql.com/bug.php?id=61842

Really, the only thing that happened to my bug report was that it was designated a duplicate of another bug (which we also cannot view):

http://bugs.mysql.com/bug.php?id=61101

Based on the id, and the submitted dates of bugs 61100 and 61102, this initial bug (61101) was filed on May 9, 2011. So, in fact, this bug has been present for over …

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There are a number of significant new features in MySQL 5.5 including semi-synchronous replication, SIGNAL and RESIGNAL, the PERFORMANCE_SCHEMA, additional STATUS variables, new partitioning options, different default storage engine, better UTF8 support and removal of deprecated functions just to list key considerations.

However some of the performance improvements are worth the investment of time. For a high concurrency InnoDB environment one new configuration alone can provide a …

Reading MySQL security: inconsistencies I remembered a few related experiments that I did several years ago when I was studying for the MySQL certification. The first fact that came to mind is about the clause "WITH GRANT OPTION", which can only be given on the full set of options, not on a single grant. For example

GRANT INSERT,DELETE,UPDATE on world.* to myuser identified by 'mypass';
GRANT SELECT on world.* to myuser identified by 'mypass' WITH GRANT OPTION;
show grants for myuser\G
*************************** 1. row ***************************
Grants for myuser@%: GRANT USAGE ON *.* TO 'myuser'@'%' IDENTIFIED BY PASSWORD '*6C8989366EAF75BB670AD8EA7A7FC1176A95CEF4'
*************************** 2. row ***************************
Grants for myuser@%: GRANT SELECT, INSERT, UPDATE, DELETE ON `world`.* TO 'myuser'@'%' WITH GRANT …

Some time ago I wrote about MySQL 5.5 semi-synchronous replication. Since then, I have wanted to benchmark the overhead of semi-synchronous replication with a decent server. Now the occasion presented itself, thanks to some related business that I had to benchmark, and thus I did a few simple runs with and without semi-synchronous replication enabled, to see the impact of this feature on performance. If you haven't read the article on semi-synchronous replication, the bottom line is that, with this feature enabled, the master waits until at least one slave has acknowledged receipt for the data before returning a positive result to the client. This means that for each commit there are two network calls between master and slave. My gut feeling was that this feature would be costly in terms of query response time, although I was not prepared to …

  I am excited to see that MySQL 5.5 GA (5.5.8) has been finally released . All of my ex-colleagues at MySQL/Oracle have done amazing jobs. I was also positively surprised that 5.5 was released on schedule:). So far I have felt that Oracle is leading MySQL development and product management very well.
  5.5 has lots of practical features not only for web services providers, but also for enterprise users. Especially I like the following features.
Improved concurrency  Very often lots of concurrent sessions access to the same table. In such cases, one of MySQL internal global mutexes (LOCK_open) becomes very hot and serious concurrency problems have happened. Increasing table_cache have caused even negative impacts (because MySQL has to do linear search here. See bug#33948 for details). In 5.5, the problem has been fixed. Here is a very simple concurrent PK …

The first addition is something that users of stored routines have been waiting for since MySQL 5.0. No, it is not SIGNAL and its close associate RESIGNAL, which have been publicized enough. I am talking about the stored routine parameters, for which now there is a dedicated table in the information_schema.
Let's see an example, with a simple …

In my continuing MySQL 5.5 blog series, today I am covering what's new on the replication front.  MySQL replication is my favorite server feature and what drew me to MySQL during my tenure with Embarcadero Technologies.  Others seem to agree as based on community and customer surveys, MySQL replication is the most popular and widely used database feature.  Mostly because it is easy to set up and ease, it enables scalability and provides a pretty robust solution for data redundancy, backup and overall availability.  In MySQL 5.5 replication has been enhanced in response to user requests that MySQL replication:

• Ensure data consistency between master and slave servers
• Immediately detect if replication is not working
• Allow a crashed slave to automatically recover from the master relay log
• Allow users to filter …

Why does this change make me feel better? Because cmake configuration is more user friendly than the old autoconf/automake/libtools horror syntax. Not only that, but there is a GUI!
I am a command line guy, as you probably know, but when the purpose of a GUI is not only to show off but to make …

UPDATE This matter was more tricky than it appeared at first sight. As Bug#49861 shows, several MySQL engineers were …

OverviewWhat's this new …