Month: July 2014

It looks like the white dots in this optical illusion are all orbiting an imaginary point in space that, at the same time, is orbiting the center of that red circle. They are not. In reality, they are all moving in straight lines going from one side of the red circle to the opposite one.

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via Gizmodo
Wow, all these rotating white dots are actually moving in straight lines

I recently worked on a case where one node of a Galera cluster had its schema desynchronized with the other nodes. And that was although Total Order Isolation method was in effect to perform the schema changes. Let’s see what happened. Background For those of you who are not familiar with how Galera can perform […]

The post A schema change inconsistency with Galera Cluster for MySQL appeared first on MySQL Performance Blog.

via MySQL Performance Blog
A schema change inconsistency with Galera Cluster for MySQL

I’ve been shooting airguns, on and off, for thirty years. In the USSR, break-open .177 pellet guns were common at indoor arcades, and I spent many a 5-copek coin to buy two pellets and launch them against reactive metal targets 5-10 meters away. In 1990 Illinois, my father bought a pump pellet gun, a surprisingly[…..]
via AllOutdoor.com
Crosman 2300S Air Pistol Review

It’s been 15 years since I was a Boy Scout and, by all accounts, I’m now a grown ass man. But, the impact the organization had on my life is still evident in my daily life. Here’s how.

That’s me, turned sideways in the front row above.

Boy Scouts Taught Me To Shoot: Late last November, I had the opportunity to jump in on a last minute hunting trip. I showed up, was handed an unfamiliar rifle, shot three rounds on a range, then headed into the field with six bullets in my pocket. The next morning, I came back with five of those bullets and the pig you see here. I hadn’t even handled a rifle in 10 years or more, but picking up this Weatherby Mark V, I was immediately able to use it with confidence. As the herd of pigs ran across me 50 yards away, at full speed, I was able to pick the fattest sow, line her up and shoot her square in the heart. She was dead before she hit the ground and I took home 75lbs of the nicest tasting, healthiest pork possible.

Who do I have to thank for that? Mr. Switzer, my old Scout Master. A former Army Ranger sniper in Vietnam, he instilled in the troop both a respect for firearms, and the ability to use one. I didn’t have to buy meat for months thanks to Boy Scouts.http://ift.tt/1k96EKP…

Boy Scouts Gave Me Confidence: I know I can handle a gun, shoot an arrow, build a fire, paddle a canoe, build a shelter, use a knife, save a life and about a million other skills. No, I don’t get to show off my sweet whittling skills every day here in Hollywood, but the subconscious memory of those capabilities has a way of putting everyday challenges into perspective.

This weekend, I’m going spearfishing for the first time. Bet I catch something. Every new challenge is now just another small addition to a solid foundation of capability. In the case of spearfishing, all the swimming and fishing and paddling I did as a Scout will help out, but even when it comes to launching a new site around a totally new topic within Gawker, I know I’m up to the task.http://ift.tt/1wAAOxw…

Boy Scouts Gave Me The Ability To Save Lives: Back in college, I was sitting in a pub with my little sister and her friends when I had to pee. When I walked into the bathroom upstairs, an elderly man was rolling around on the ground, in the last throes of choking before passing out. I picked him up, gave him the Heimlich maneuver, then sat with him until he recovered. This being England, you don’t make a fuss out of things, so when we walked back down 30 minutes later, everyone got quite the giggle out of me showing up after a very long bathroom break with a new, red-faced friend thanking me profusely. I didn’t want to embarrass him in front of his family, so didn’t explain things until after they left.

And that’s just one incident. Elsewhere, I’ve pulled people out of the ocean, from wrecked cars, used my motorcycle to stop highway traffic on the 405 to protect a crashed biker and probably a few other incidents I’ve forgotten. That’s not me being a hero, that’s an Eagle Scout doing his job.

Boy Scouts Gave Me The Outdoors: As you’d expect, we spent some time outside as Scouts, doing everything from canoe trips to rock climbing to sailing on the ocean. That experience doing those things and learning to master them has given me the ability to continue to enjoy all that to this day. Whether it was rafting last weekend or going kayak camping/spear fishing tomorrow, an entire world of outdoor recreation is now easily accessible thanks to the skills, confidence and experience Scouts gave me.http://ift.tt/1lS2FaC…

Scouts Taught Me To Survive: Know how everyone thinks they’re a survival expert now that Bear Grylls taught them how to drink their own urine? Survival entertainment is massively misleading and downright dangerous. It’s extraordinarily unrealistic that you’d be able to start a fire with nothing but two sticks and, in most survival scenarios, you wouldn’t need to. The genre has created unrealistic expectations and armed people with false confidence. Know what Scouts taught me? Be Prepared. That approach has served me equally well when weather has taken an unexpected turn for the worse while camping or when needing to self rescue after a dirt bike accident in a remote desert. It’s planning ahead, identifying potential risks, then preparing for them that will save your ass, not eating grubs.

Scouts Made Me A Leader: There’s not much that’s more confidence destroying than being an awkward 13-year old boy like the one pictured above (that’s me). But, even then, when any other kid like me would have just hidden in their shell, Scouts gave me responsibility and the opportunity to lead others, something that gave me a huge amount of confidence at the time and has stuck with me until today. 11 people are tagging along on our trip to Catalina this weekend with total confidence that they’re going to have a great time and be safe, even on the ocean in freakin’ kayaks. All I had to do was suggest the idea. This is a fairly typical scenario, whether it be with colleagues or friends.

Scouts Are The Best Secret Society: Forget the Illuminati or the Skull and Bones. You want to be part of a fraternal order that means something? At 33 years old, I still put "Eagle Scout" on my resume and keep my membership card in that organization behind my driver’s license. It’s gotten me into jobs, out of trouble and immediately marks me out to other members as a peer that can be relied upon. We actually kinda run the world.

Scouts Made Me A Worker: When I’m not cranking out 5 to 10,000 words a day, you’ll find me working out at the gym, taking my dog hiking or fixing up my house. I never stop. It’s not an illness, it’s an appreciation of the value of hard work and a mindset that values long term goals. You won’t find a colleague of mine that wouldn’t immediately describe me as the hardest working guy on the team and I more than pull my weight in any endeavor I embark upon, even if that’s just making sure I’ve got the heaviest pack on a backpacking trip. Guess where I learned that? You got it.

Scouts Made Me Value Difficulty: I have a habit of making things difficult for myself. Some would describe it as self destructive, but I don’t often meet people who aren’t a little jealous of the life I’ve built for myself as a result. Five years ago, I quit what would be many people’s dream job — Jalopnik’s first Road Test Editor — to go full time on a business I’d been building my whole time working there, my very own motorcycle publication. Media is a hard industry right now and motorcycles is an even worse one, but I wasn’t intimidated. I slaved away, had a lot of great experiences, built something that mattered and then decided I wanted to do something else. So, I pitched Gawker on launching a site around adventure travel in the outdoors and here I am today. We just decided to make it a permanent part of the mix here at Gizmodo. Not bad, right? Thanks Scouts.

IndefinitelyWild is a new publication about adventure travel in the outdoors, the vehicles and gear that get us there and the people we meet along the way. Follow us on Facebook, Twitter and Instagram.

via Gizmodo
​Boy Scouts Made Me The Man I Am Today, Here’s How

Just when you thought that mankind’s genius could stretch no further, a solid year of research has given birth to a new apex in cake innovation. Friends, say hello to Spray Cake, the Harvard-bred cake batter in a can.

People have shoved a lot of weird things in aerosol cans over the years, but Harvard Student John McCallum ignored weird and saw the potential for something wonderful. After learning about the chemistry behind what makes cakes rise, the 20-year-old decided to see if the accelerant in aerosol cans, which releases bubbles into the product as it comes out, would also allow cakes to rise without any baking soda or baking powder. Luckily for us, it did.

And after spending months perfecting the recipe in his dorm, McCallum is now in the process of patenting what he ultimately dubbed Spray Cake. Meaning that this could actually become a real thing on your grocery store shelf, and that there’s still some hope for the human race yet.

McCallum and his business partner/lady friend Brooke Nowakowski assured The Boston Globe that their fully microwavable product has the same mouthfeel as traditional cakes. And since it comes out pre-risen, it cooks in a fraction of the time (about one minute for a full cake).

Apparently, the two young entrepreneurs have already found a seller and are now just shopping for the manufacturer. What’s more? Bakery superstar Joanne Chang has even tasted the cakes and offered her thumb of approval. We’ll take 20. [Boston Globe]

via Gizmodo
Aerosol Cake Batter Is Real Now and Nothing Will Ever Be the Same

Lots of schools now offer free, online courses, but here’s a doozy from MIT: an introductory course about documentary photography and photojournalism that won’t cost you a cent to work through.

Published through MIT’s Open Courseware project, the course—Documentary Photography and Photojournalism: Still Images of a World in Motion—was originally taught by Prof. B. D. Colen. The class is pretty full-on: there are readings, and assignments you need to work through, plus an image gallery and course material to download, too. But it should provide you with a great understanding of the theory and practice of photojournalism. You can investigate it and download the course materials here. [MIT via Reddit via Peta Pixel]

via Gizmodo
MIT Has a Free Photojournalism Course You Should Do

Following a Thursday announcement that Bill Campbell would retire as a member of Apple’s board of directors, Fortune published an interview in which the Intuit chairman describes his time in Cupertino, relationship with cofounder Steve Jobs and "coach" to silicon valley elite.

via AppleInsider – Frontpage News
Outgoing Apple board member Bill Campbell offers insight into company, Steve Jobs in interview

Food dehydrators are a great way to prepare tasty snacks, but they can be expensive. When the time comes to replace your old fridge, don’t immediately send it off to the dump—you can give it a new lease of life.

Instructables memberWillie Kruger’s dehydrator project can be used to product dried fruit, biltong ( a kind of beef jerky), and all sorts of other goodies Consumer dehydrators are available to buy, but they are not cheap and are usually quite small. Willie worked with a full-sized refrigerator, but the same could be done to a mini fridge.

After gutting the inside of the fridge, you can paint the exterior however you like, but dehydrators are usually black. Willie also sprayed the words Vleis Kas (Afrikaans for Meat Box) on the unit. He had to build a new door and added an inspection window. Heat in the dehydrator comes from light bulbs, and computer fans keep air moving around. Take care with the electrics, and keep in mind that you’ll need a 12V transformer for the fans.

You can hang meat from hooks attached to the shelves to create biltong, and Willie has other ideas for dried fruit on his website. Click the Instructables link below for full details.

Food Dehydrator | Instructables

via Lifehacker
​Transform an Old Refrigerator Into a Food Dehydrator

On Wednesday I gave a presentation on “How to Avoid Even More Common (but Deadly) MySQL Development Mistakes” for Percona MySQL Webinars.  If you missed it, you can still register to view the recording and my slides.Thanks to everyone who attended, and especially to folks who asked the great questions.  I answered as many as we had time for  during the session, but here are all the questions with my complete answers:Q: Disk bandwidth also not infinite Indeed, you’re right!We discussed in the webinar the impact on network bandwidth from using column wildcards in queries like SELECT *, but it’s also possible that using SELECT * can impact disk operations. Varchar, Blob, or Text columns can be stored on extra pages in the database, and if you include those columns in your query needlessly, it can cause the storage engine to do a lot of seeks and page reads unnecessarily.For more details on string storage in InnoDB, see Peter Zaitsev’s blog on Blob Storage in Innodb.Q: How many tables can be joined in a single query? What is the optimal number of joins?MySQL has a limit of 63 table references in a given query. This limits how many JOIN operations you can do, and also limits the number of UNIONs. Actually you can go over this limit if your JOIN or UNION don’t reference any tables, that is, create a derived table of one row of expressions.If you do join a lot of tables (or even self-join the same table many times), you’re likely to hit a practical scaling limit long before you reach 63 table references. The practical limit in your case depends on many factors, including the length of the tables, the data types, the type of join expressions in your queries, and your physical server’s capabilities. It’s not a fixed limit I can cite for you.If you think you need dozens of table references in a single query, you should probably step back and reconsider your database design or your query design.I often see this type of question (“what is the limit on the number of joins?”) when people try to use key/value tables, also called Entity-Attribute-Value, and they’re trying to pivot attributes from rows into columns, as if the table were stored in a conventional way with one column per attribute. This is a broken design for many reasons, and the scalability of many-way joins is just one problem with it.Q: How many indexes can be created in a single table? Any limitation? What is the optimal number of indexes?All MySQL storage engines support at least 16 indexes per table.As far as the optimal number of indexes, I don’t pay attention to the number of indexes (as long as it remains lower than the max of 16). I try to make sure I have the right indexes for my queries. If you put an arbitrary cap of for example 8 or 10 indexes on a given table, then you might be running queries that lack a needed index, and the unnecessary extra cost of running that query is probably greater than the cost of maintaining the one extra index it needs.That said, there are cases where you have such variation in query types that there’s no way to have optimal indexes to cover every possible case. Given that you can have multi-column indexes, and multi-column indexes with columns in different orders, there are n-factorial possible indexes on a table with n columns.Q: There is a table with 3 columns: id(int), user_id(int), day(date). There is a high chance same user_id will ‘exist’ for every day. I read data by “where user_id = some_id” (very high throuhput) and delete all entries once a day by cron using “where sent_date = ’2014-01-01′ “. Have approx 6M rows per day deletion is pretty painfull. Will partitioning by column ‘day’ help me deleting those bulks faster? If yes – how much faster? How much will it slow down SELECTs? – not all entries are deleted, but only entries for some specific old day, e.g. ‘ WHERE day = ’1 week ago’Range partitioning by date would give you the opportunity to ALTER TABLE…DROP PARTITION, so you could remove all data for a given date very quickly, much faster than deleting millions of rows. The performance of DROP PARTITION is like that of DROP TABLE, because each partition is physically stored like a separate table.Searching for “where user_id = ?” would not be able to take advantage of partition pruning, but it would still be able to use an index on user_id. And if you drop old partitions, the benefit of searching a smaller table could be a good tradeoff.Q: Regarding 20% selectivity as a threshold for the optimizer preferring a table-scan to an index lookup – is that a tunable?No, it’s not tunable, it’s a fixed behavior of the query optimizer. If you search for a value and the optimizer estimates that > 20% of rows contain the value you search for, it will bypass the index and just do a table-scan.For the same reason that the index of a book doesn’t contain very common words, because the list of pages that word appears on would be too long, and flipping back and forth from the back of the book to each listed page would actually be more work than just reading the book.Also keep in mind my figure of 20% is approximate. Your results may vary. This is not a magic threshold in the source code, it’s just a tendency I have observed.Q: Regarding generating synthetic test data, it sounds like a pretty easy perl script to write.Yes, it might be easy to do that for one given table. But every table is different, and you might have hundreds of tables in dozens of applications to generate test data for. You might also want to vary the distribution of data values from one test to another.Writing a test-data generator for one particular case is easy, so you might reasonably do it as a one-off task. Writing a general-purpose test-data generator that you can use for many cases is more work.Q: Would love to have the set of URLs cited in the presentation without having to go back and mine them out of the presentation.Open source message queues:Redis (Resque)OpenMQActiveMQRabbitMQGearmanBeanstalkKafkaKestrelMySQL Performance Blog articles:Exploring Message BrokersKiss Kiss Kiss (keep it simple)Why you don’t want to shardOpen source test-data generator:Databene BeneratorLoad-testing tools for web applications:JMeterSiegeLoad-testing tools to replay query logs:Percona Playbackpt-log-playerFurther reading for implementing business rules:Real-World Rules EnginesThe Enterprise Rules Engine (a warning)Drools, the business logic integration platformQ: How to best use mysql query cache?Any cache is best used if you read from it many times for each time you write to it. So we’d like to estimate the average ratio of query cache reads to writes, to estimate how much leverage it’s giving us.mysql> SHOW GLOBAL STATUS LIKE ‘Qcache%’; Check the values for QCache_hits (which are cases when a query result was read from the query cache) over QCache_inserts (which are cases when the desired query result was not in the cache, and had to be run and then the result stored in the cache). I like to see a ratio of 1000% or more (i.e. 10:1 hits to inserts).If you have a poor ratio, for example less than 1:1 or less than 100%, then consider disabling the query cache, because it may be costing more to maintain it than the performance benefit it’s giving you.Keep in mind that this is only a guideline, because the calculation I described is only an average. It could be that the queries served by the query cache are very expensive, so using the cached result is a great benefit even if it accounts for a small number of hits. The only way to be certain is to load-test your application under your load, and compare overall performance results with the query cache enabled or disabled, and at different sizes.Q: How to detect when too much indexes start to affect performance?Some people are reluctant to create indexes because they have been warned that indexes require synchronous updates when you INSERT, UPDATE, or DELETE rows. Some people also make the generalization that indexes harm writes but benefit reads. Bot of these are not true.Your DML operations aren’t really updating indexes in real time. InnoDB includes a feature called change buffering, which defers index updates. The change buffer is gradually merged into the index over time. That way, InnoDB can handle a big spike in traffic without it hurting throughput as much. You can monitor how much content in the change buffer remains to be merged: mysql> SHOW GLOBAL STATUS LIKE ‘Innodb_ibuf_size’; It’s also not accurate that indexes hurt writes. UPDATE and DELETE statements usually have a WHERE clause, to apply the changes to particular rows. These conditions use indexes to reduce the examined rows, just like in SELECT statements. But in UPDATE and DELETE statements, it’s even more important to use indexes, because otherwise the statement has to lock a lot of rows to ensure it locks the rows you’re changing.So I generally say, don’t avoid indexes based only on the number of indexes you have, just make sure your indexes are being employed by the queries you run, and drop indexes that aren’t used. Here are a couple of past blog posts that show how to do this:Find unused indexesQuickly finding unused indexes (and estimating their size)Thanks again for attending my webinar!  Here are some more tips:Check out upcoming Percona Training classes in North America and Europe.Join Percona and the MySQL community at our Percona Live.Watch more webinars from Percona in the future!The post Q&A: Even More Deadly Mistakes of MySQL Development appeared first on MySQL Performance Blog.
via Planet MySQL
Q&A: Even More Deadly Mistakes of MySQL Development