In The Princess Bride, every night the Dread Pirate Roberts tells Westley: “Good night, Westley. Good work. Sleep well. I’ll most likely kill you in the morning.” Let’s say the Dread Pirate Roberts wants to optimize this process, so he stores prisoners in a database. When he captures Westley, he can put: > db.prisoners.insert({ … [...]
I’ve been doing replica set “bootcamps” for new hires. It’s mainly focused on applying this to debug replica set issues and being able to talk fluently about what’s happening, but it occurred to me that you (blog readers) might be interested in it, too. There are 8 subjects I cover in my bootcamp: Elections Creating [...]
Having readahead set too high can slow your database to a crawl. This post discusses why that is and how you can diagnose it. The #1 sign that readahead is too high is that MongoDB isn’t using as much RAM as it should be. If you’re running Mongo Monitoring Service (MMS), take a look at [...]
MongoDB users often ask about the “killed” field in db.currentOp() output. For example, if you’ve run db.killOp(), you might see something like: > db.currentOp() { "inprog" : [ { "opid" : 3062962, "active" : true, "lockType" : "write", "waitingForLock" : false, "secs_running" : 32267, "op" : "update", "ns" : "httpdb.servers", "query" : { "_id" : [...]
I’ve been doing replica set “bootcamps” for new hires. It’s mainly focused on applying this to debug replica set issues and being able to talk fluently about what’s happening, but it occurred to me that you (blog readers) might be interested in it, too. There are 8 subjects I cover in my bootcamp: Elections Creating [...]
One of the most common questions I see about MongoDB schema design is: I have a collection of blog posts and each post has an array of comments. How do I get… …all comments by a given author …the most recent comments …the most popular commenters? And so on. The answer to this has always [...]
This is a supplement to the Hacking Chess with the MongoDB Pipeline. This post has instructions for rolling your own data sets from chess games. Download a collection of chess games you like. I’m using 1132 wins in less than 10 moves, but any of them should work. These files are in a format called [...]
MongoDB’s new aggegation framework is now available in the nightly build! This post demonstrates some of its capabilities by using it to analyze chess games. Make sure you have a the “Development Release (Unstable)” nightly running before trying out the stuff in this post. The aggregation framework will be in 2.1.0, but as of this [...]
I’ve been doing replica set “bootcamps” for new hires. It’s mainly focused on applying this to debug replica set issues and being able to talk fluently about what’s happening, but it occurred to me that you (blog readers) might be interested in it, too. There are 8 subjects I cover in my bootcamp: Elections Creating [...]
ObjectIds contain a timestamp, which tells you when the document was created. Because the _id field is always indexed, that means you have a “free” index on your “created at” time (unless you have persnickety requirements for creation times, like resolutions of less than a second, synchronization across app servers, etc.). Actually using this index [...]
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