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Showing entries 1 to 27

Displaying posts with tag: usability (reset)

Old and new MySQL verbosity
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I was pleased to see Morgan’s announcement about a fix to an old problem of mine. In March 2012 I complained about MySQL verbosity during installation.

In MySQL 5.7.3, this behavior was changed. While the default is still as loud as it can, you can now add an option (log_error_verbosity) to send only errors to STDERR, which allows you to hide the output of mysql_install_db, and still get the errors, if they occur.

Well done!

However, the same obnoxious verbosity is also in MariaDB 10.0.x. Since I discussed this specific bug with a few MariaDB developers early in 2012, I was disappointed to see this same output when running mysql_install_db with MariaDB.

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Parallel replication: off by one
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One of the most common errors in development is where a loop or a retrieval by index falls short or long by one unit, usually because of an oversight or a logic in coding.

Of the following snippets, which one will run 10 times?

/* #1 */    for (N = 0 ; N < 10; N++) printf("%d\n", N);

/* #2 */ for (N = 0 ; N <= 10; N++) printf("%d\n", N);

/* #3 */ for (N = 1 ; N <= 10; N++) printf("%d\n", N);

/* #4 */ for (N = 1 ; N < 10; N++) printf("%d\n", N);

The question is deceptive, as there are two snippets that will run 10 times (1 and 3). But they will print different numbers. If you ware aiming for numbers from 1 to 10, only #3 is good.

After many years of programming, off-by-one errors are rare in my code, and I have been able to spot

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Welcome Tungsten Replicator 2.1.0!
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First off, the important news. Tungsten Replicator 2.1.0 was released today.
You can download it and give it a try right now.

Second, I would say that I am quite surprised at how much we have done in this release. The previous release (2.0.7) was in February, which is just a few months ago, and yet it looks like ages when I see the list of improvements, new features and bug fixes in the Release Notes. I did not realized it until I ran my last batch of checks to test the upgrade from the previous release, which I hadn’t run for quite a long

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Installing and administering Tungsten Replicator - Part 2 : advanced
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Switching roles

To get a taste of the power of Tungsten Replicator, we will show how to switch roles. This is a controlled operation (as opposed to fail-over), where we can decide when to switch and which nodes are involved.

In our topology, host1 is the master, and we have three slaves. We can either ask for a switch and let the script select the first available slave, or tell the script which slave should be promoted. The script will show us the steps needed to perform the operation.

IMPORTANT! Please note that this operation is not risk free. Tungsten replicator is a simple replication system, not a complete management tool like Continuent Tungsten. WIth the replicator, you must make sure that the applications have stopped writing to the master before starting the switch, and then you

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Parallel replication and GTID - A tale of two implementations
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MySQL 5.6 is probably the version of MySQL with the biggest bundle of new features. You may want to try it soon, since it's now released as GA, and I would like to offer some practical experience on how to use some of the advanced features.

Since replication is my main interest, I will focus on some of the new features in this field, and I will compare what's available in MySQL 5.6 with Tungsten Replicator.

The focus of the comparison is usability, manageability, and some hidden functionality. Parallel replication has been available with Tungsten Replicator for almost two years, and Global Transaction Identifiers for much longer than that. With MySQL 5.6, it seems that the MySQL team wants to close the gap. While the main feature (parallel execution threads) is available and performing well, there are some

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MySQL Sandbox 3.0.30 - now adapted to work with 5.5.30 and 5.6.10
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The latest releases of MySQL Sandbox, in addition to deal with minor bugs, have mostly been necessary because of compatibility issues in MySQL, both 5.5 and 5.6.

When I found that MySQL 5.6 has some InnoDB tables inside the 'mysql' schema, I had to change the way that the sandbox used to remove all contents (the ./clear command.)

To achieve a smooth clean up, MySQL Sandbox now performs a dump of the mysql schema, and uses that saved data to restore the schema after a complete wipeout.

Unfortunately, when 5.5.30 was released, this operation resulted in a warning, due to a behavioral change.

After a careful change, and about 1200 unit tests, the latest version of MySQL Sandbox should work well with every MySQL release from 5.0 to 5.6.

MySQL and warnings - Yet another compatibility break
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The MySQL team seems to have a very peculiar idea about defaults and compatibility. Recently, I wrote about an annoying warning that cannot be removed. And previously, I noticed that MySQL 5.6 mixes warnings, info lines and errors in the same bunch of excessive chattiness.

With MySQL 5.5.30 came another headache. When I run a mysqldump of the 'mysql' schema, I get this warning:

$. mysqldump mysql > m.sql
-- Warning: Skipping the data of table mysql.event. Specify the --events option explicitly.

OK. No big deal. What if I tell the little troublemaker that I DON'T WANT the events table?

$ mysqldump --skip-events mysql > m.sql

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Google Docs sharing and its cloudy usability
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Background: SkySQL is a distributed company. Nearly all of us work from home. To be productive, we need to emulate the best aspects of collaborating as if we were working next to one another. Given that nearly all of us had worked under similar distributed conditions at MySQL AB, we knew what we were getting into when we were founded. Obviously, we wanted to learn from our past experiences when making our choices for tools and processes.

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MySQL 5.6 too verbose when creating data directory
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When I install a MySQL package using MySQL Sandbox, if everything goes smoothly, I get an informative message on standard output, and I keep working.

This is OK

$HOME/opt/mysql/5.5.15/scripts/mysql_install_db --no-defaults \
--user=$USER --basedir=$HOME/opt/mysql/5.5.15 \
--datadir=$HOME/sandboxes/msb_5_5_15/data \
Installing MySQL system tables...
Filling help tables...

To start mysqld at boot time you have to copy
support-files/mysql.server to the right place for your system

To do so, start the server, then issue the following commands:

/Users/gmax/opt/mysql/5.5.15/bin/mysqladmin -u root password 'new-password'

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Tungsten 2.0.5 with more power and ease of use
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Tungsten Replicator 2.0.5 was released this week-end. The release notes have quite a long list of bug fixes. Thanks to all the ones who have submitted bug reports, and fixes! There are a couple of new features as well. The replicator includes now a slave prefetch service. Unlike parallel replication, this feature works fine with a single database, and provides performance improvements that in many cases solve the slave lagging problems. This was a bitch of a feature to get right. Many have tried it, many have experienced various degrees of success, and several failures. We started with the bold assertiveness of the brave after an exciting talk at  [Read more...]
Testing new builds with MySQL-Sandbox 3.0.24
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MySQL::Sandbox 3.0.24 was released yesterday, with many new features.

More than vanilla MySQL

If you have missed my previous announcement, here's the gist of it. MySQL Sandbox can now deal with tarballs from either Percona Server or MariaDB. The main difference after this change is that you can now create a directory called <PREFIX>5.5.16 and make_sandbox will recognize it as well as the plain 5.5.16.
$ make_sandbox --export_binaries --add_prefix=ps \
Percona-Server-5.5.11-rel20.2-114.Darwin.i386.tar.gz \
-- --sandbox_directory=msb_ps5_5_11

unpacking Percona-Server-5.5.11-rel20.2-114.Darwin.i386.tar.gz

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Upgrading Tungsten Replicator: as easy as ...
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When I talked about the usability improvements of Tungsten Replicator, I did not mention the procedure for upgrading. I was reminded about it by a question in the TR mailing list, and since the question was very relevant, I updated the Tungsten Cookbook with some quick upgrading instructions. A quick upgrading procedure is as important as the installer. Since we release software quite often, either because we have scheduled features to release or because of bug fixes, users want to apply a new release to an existing installation without much fuss. You can do the upgrade with a very quick and painless procedure. Let's suppose that you have installed one Tungsten Replicator cluster using this command:

# using

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Usability improvements in Tungsten Replicator 2.0.4
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If you love a software product, you should try to improve it, and not be afraid of criticizing it. This principle has guided me with MySQL (where I have submitted many usability bugs, and discussed interface with developers for years), and it proves true for Tungsten Replicator as well. When I started working at Continuent, while I was impressed by the technology, I found the installation procedure and the product logs quite discouraging. I would almost say disturbing. Fortunately, my colleagues have agreed on my usability focus, and we can enjoy some tangible improvements. I have already mentioned the new installation procedure, which requires just one command to install a full master/slave cluster. I would like to show how you can  [Read more...]
Getting started with Tungsten Replicator and Tungsten Sandbox
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We have been busy, at Continuent. In addition to our usual work with high performance replication, we have addressed usability issues, since we know that a hard-to-use problem, no matter how powerful, has low adoption. Thus, is with some personal satisfaction that I can announce the release of Tungsten Replicator 2.0.3, which comes with several huge improvements in matter of user friendliness. The new installation procedure is so user friendly, in fact, that I was able to build a sophisticated tungsten-sandbox with a  [Read more...]
Exchanging partitions with tables
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While I was presenting my partitioning tutorial at the latest MySQL Conference, I announced a new feature that was, as far as I knew, still in the planning stage. Mattias Jonsson, one of the partitions developers, was in attendance, and corrected me, explaining that the feature was actually available in a prototype.
So, we can have a look at this improvement, which I am sure will make DBAs quite happy. The new feature is an instantaneous exchange between a partition and a table with the same structure. Using this feature, you can transfer the contents of one partition to one table, and vice versa. Since the transition is done only in the
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Holiday gift - A deep look at MySQL 5.5 partitioning enhancements
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Half a day into my vacation, I managed to finish an article on a topic that has been intriguing me for a while.
Since several colleagues were baffled by the semantics of the new enhancements of MySQL 5.5 partitions, after talking at length with the creator and the author of the manual pages, I produced this article: A deep look at MySQL 5.5 partitioning enhancements.
Happy holidays!

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

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Forums are crap. Can we get some help?
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Amy Hoy has written a blog post about why forums are crap. And she is right. Forum software does not always do a good job of helping people communicate. I have worked with Amy. She did a great analysis of dealnews.com that led to our new design. So, she is not to be ignored.

However, as a software developer (Phorum), I see a lot of problems and no answers.  And it is not all on the software.  Web site owners use forums to solve problems that they really, really suck at.  Ideally, every web site would be very unique for their audience.  They would use a custom solution that fits a number of patterns that best solves their problem.  However, most web site owners don't want to take the time to do such things.  They want a one stop, drop

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OPTIMIZE TABLE on Cluster (revisited)
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Jonas just wrote a patch to this bug on OPTIMIZE TABLE, and the issue that was also discussed in this blog post. Jonas also fixed this bug when he was at it.

Before, OPTIMIZE TABLE hardly freed up any pages and to defragment you had to do a rolling restart of the data nodes.

Now, there is only a 2% discrepancy between OPTIMIZE TABLE and doing a rolling restart. This is great stuff.
This will fix will make it into 6.3.26 and 7.0.7.

See below for details:

Creating two tables, t5 and t6:

`id` varchar(32) CHARACTER SET utf8 NOT NULL,

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Problems with .FRM files, auto-discovery and MySQL Cluster
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There are some bug reports on the auto-discovery protocol in MySQL Cluster.
The idea of the auto-discovery protocol is to fetch the .frm files for the NDB tables stored in the data dictionary of the data nodes, and put them in the data directory of the mysql server.

However, sometimes (not always, which makes it more difficult to reproduce and hence fix), the auto-discovery seems to make strange things (from this bug report):
After shuting down and restoring my cluster I get the following error.

090211 9:59:26 [Note] NDB: mismatch in frm for panel.gatewayquestions, discovering...
090211 9:59:26 [Note] NDB Binlog: DISCOVER TABLE Event: REPL$panel/gatewayquestions
090211 9:59:26 [Note] NDB Binlog: logging ./panel/gatewayquestions (UPDATED,USE_WRITE)


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Failing by choice. Another bug-vs-feature debate ends
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A long standing bug

Among the many outstanding bugs for MySQL, there is one that has sparked a fierce discussion, not only in the bug report itself, but also in blogs, forums, mailing lists.
Bug #19027: MySQL 5.0 starts even with Fatal InnoDB errors was neglected for long time, until finally it got fixed, and it is available in MySQL 5.1.36.
First off, what is it about?
In short, if an engine doesn't initialize correctly, the MySQL server starts anyway, without the offending engine. Depending on how you use the failing engine, this could be either a minor annoyance or a complete disaster.
Annoyance: ARCHIVE fails to initialize, and you create tables with the default engine (usually MyISAM), and after a while you realize that the disk is filling up faster than you expected. You will find

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MySQL Sandbox and laziness
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Laziness strikes again.
MySQL Sandbox was created with the intent of avoiding repetitive work when creating and using several servers. Turns out that even the current framework, which many say that is really time saving and enhances productivity, was not enough. So my desire for laziness, which is, as everybody should know a chief virtue for a programmer has made me code a shortcut script, which can joggle sandboxes as never before.
Enter the sb script (available in version 3.0.03). Now I can shorten my typing experience with sandboxes quite a lot:

$ sb 5135
# same as

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max_rows in cluster
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If you are going to load a lot of records into Cluster, don't forget to set max_rows!
My colleague, Yves at BigDBAhead, has also blogged about this, but I also ran into the same problem recently.

I did try to populate 100M records on a 4 node cluster, and the data nodes went down with the following error message in the error logs:

"2304 Array index out of range"

So the error message is crap - and my opinion is that there should be a proper error message propagated up to the mysql server. There is a bug report on this.

Simplified, what the error message means is that you have run out of "index slots" in the Hash Table storing the hashes of the Primary Keys. This is because each table is divided into a number of partitions, and

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The partition helper - Improving usability with MySQL 5.1 partitioning
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I talked several times about partitioning usability. In my many tests of partitioning I found myself in need of generating list of partitions for a given range.
I made the Partition Helper to scratch this particular itch, i.e. making partitions reasonably quickly and without thinking too much.
The Partition Helper is a Perl script that converts some simple options into lots of

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Partitions usability I - blues and a preview
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Pop quiz. Look at the picture below. Quick: can you tell me to which year and month partition P001 refers?

I couldn't say it without asking the database itself to revert the output of to_days:

select from_days(723180);
| from_days(723180) |
| 1980-01-01 |

Just to make the pain more clear, you do something like this, clean and neat, and you think you have done a good job.

PARTITION by range (to_days(d))

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?Me too? comments in bug systems
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I don’t know about “me too” types of bug replies, but before everyone goes to the bug database and starts saying “me too”, “this affects me”, “please fix this ASAP”, “I won’t use MySQL 5.1 till this is fixed”, I wonder if this will cause more harm (i.e. more bug spam for the developer, and all those subscribed to it) than good.

It seems like the public Worklog interface gets this right - via voting. Having a count of those that have the same problems, even displayed via “stars”, is

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Who is the Dick on my site?
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Who is the Dick on my site?
Dick Hardt

Most interesting keynote. About 1,000+ slides. Many slides per minute. Definitely a new way of presenting :)

  • What is identity? What is Identity 2.0?
  • Identity is a complicated topic, and you normally get the tip of the iceberg. Identity changes during your stages in life.
  • Works at SXIP Identity.
  • I wondered what the German’s thought about identity. Identat. “They’re German” <applause>
  • Answers.com had the best answers for identity.
  • There’s lots of different personas about a person. Women really are the masters of different personas (clothes, wife, mother, etc.). Reinventing oneself.
  • Identity allows you to predict behaviour…
  • When someone is in a “role” (fireman, etc.),

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Dear Technical Conference Organizer
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I am a conference junkie. I love attending them, organizing them, speaking at them, planning to attend them, seeing my friends at conferences, making friends with the nice (but often stressed) people who run conferences and so on. I even like eating the (often bad) food - kvetching about it builds a sense of camaraderie with the other participants.

Given how much time and money I spend on conferences already, it might be hard for you to be able to get more money directly out of me. However, here is one small tip on a way that you might be able to do this.

When you send me email about upcoming events, send me links to useful feed as well. Many of you are technologists who run technology conferences for other technologists. For Zarquon’s sake, use the common pieces of technology that many of us use.

What would such feeds look like? Well, to answer my own

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Showing entries 1 to 27

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