We've been working on the design of a protocol which would enable promotion of a slave to a master in a MySQL replication cluster.

Right now, if a MySQL master fails, most people just deal with a temporary outage. They bring the box back up, run REPAIR TABLEs if necessary, and generally take a few hours of downtime.

Google, Flickr, and Friendster have protocols in place for handling master failure but for the most part these are undocumented.

One solution would be to use a system like DRDB to get a synchronous copy of the data into a backup DB. This would work of course but would require more hardware and a custom kernel.

You could also use a second master in multi-master replication but this would require more hardware as well and complicates matters now that you're using multi-master replication which has a few technical issues.

A simpler approach is to just take a slave and promote it to the master. …

Enjoy!

I just opened MySQL Bug #26123, to attempt to find out how many people are seeing this possible replication bug. A few Proven Scaling customers have seen the same bug, and I haven’t been able to reproduce it, so I opened a bug as a feeler. It appears to have something to do with using BLOB or TEXT fields in replication.

Are you seeing slaves stop with corrupted relay logs? Does restarting replication using CHANGE MASTER and the Exec_Master_Log_Pos from the stopped slave1 work just fine? Do the master’s binary logs look perfectly OK? Leave a comment on the bug.

1 This effectively forces the slave to re-download the exact same log events that it currently has in its relay logs. Since the corruption appears to happen either …

If you use Cocoa Bindings and have an array of NSStrings where one entry controls a check box in your user interface, you need to provide a Value Transformer in Interface Builder.

I couldn't find one, so I wrote one. The core are two methods:

- (id)transformedValue:(id)value
{
  if(value 
  && [[NSString stringWithString:value] 
  isEqualToString:@"1"]) {
    return [NSNumber numberWithBool:YES];
  } else {
    return [NSNumber numberWithBool:NO];
  }
}

- (id)reverseTransformedValue:(id)value
{
  if([value boolValue] == YES) {
    return [NSString stringWithString:@"1"];
  } else {
    return [NSString stringWithString:@"0"];
  }
}

They convert an NSString to a BOOL and vice versa. This is not exactly true, as these functions work …

It's time for the 3rd Belgian MySQL UG meetup! this time we head to Leuven where L2U expects us the day after Valentine and Geert will be talking about his trip to Orlando

By reader request, this article explains ways to remove duplicate rows when they are completely identical, and you don't have a primary key or other criterion to identify which rows to "save."

I and David went to go visit Solid DB yesterday. They are one of the
companies now producing storage engines for MySQL. You can find a
copy of their engine here:

http://dev.soliddb.com/en/download/download_files.php

What is special about their engine? Its transactional engine, MVCC
engine, that has foreign keys. It keeps the transaction in memory
until it is time to commit. More about their own technical
information here:

http://dev.soliddb.com/doc

We spent the time going over changes the loadable engine interface,
which includes the I_S for loadable interface. I also got to see a
preview of what they will be showing at the MySQL User's Conference (which I am excited
to see …

Every so often I have someone ask me "does it really matter if I pool
connections?".

The answer is yes!

We are currently looking at patches for MySQL to disconnect thread
context from actual threads (and yes, that means that if I can get
some bugs worked out I will have a copy of MySQL running with
libevent, Monty is working on a Windows and Solaris specific patch).
I was curious though about the current context cost so I rigged up a
million row insert test with the number of threads growing by a
hundred at each test run.

The run used:
~/mysqlds/5.1/bin/mysqlslap --create=create2.sql --query="INSERT
INTO accesslog VALUES (1,'GET','4428','HTTP/1.1','/
index.pl','lastnode_id=305&node_id=2802','krow.net','10.10.10.10',NULL,N
ULL,'somedork','2006-08-28 08:32:28')" --
…

According to analyst firm Evans Data Corp, MySQL has a 44% share of the global RDBMS market making it the #1 database in the world. The article explains all the basic stuff about MySQL, with information such as where it started, what it is for or what systems it runs on. My favourite is “What makes it special?”

EDC’s research among users found that proprietary database servers were “almost twice as likely” as MySQL servers to have suffered a security breach.

According to MySQL AB, using MySQL can reduce database licensing costs by 90%, and administration, engineering and support costs by up to 50%. There is also a 60% reduction in downtime. …

I continue to work on figuring out why some feed entries aren't making it into the PlanetMySQL aggregated feed database. Even with all the logging printouts I've added, some feeds continue to get left out; I'm not sure if it is a Magpie caching issue or not, but that's the first place I'm going to examine. In the meantime, if you know your feed entries are not making it into the planet feed, please shoot the community team an email at community at mysql dot com and let us know the details of the feed so that we can diagnose the issues.

While working on the planet code, I started thinking about ways that we can improve the PlanetMySQL website and functionality. One of the most frequent issues that I hear come up is the sheer volume of items that get aggregated by PlanetMySQL (when it's working correctly of course... ) and the fact that some folks just don't care about certain blog entries …