Ray's playground

摘要： A replica set is basically a master-slave cluster with automatic failover. The biggestdifference between a master-slave cluster and a replica set is that a replica set does nothave a single master: on... 阅读全文

摘要： MongoDB supports reading configuration information from a file. This can be usefulif you have a large set of options you want to use or are automating the task ofstarting up MongoDB. To tell the serve... 阅读全文

摘要： In addition to these basic operations, MongoDB supports a wide rangeof advanced operations that are implemented as commands. Commands implement allof the functionality that doesn’t fit neatly in... 阅读全文

摘要： MapReduce is the Uzi of aggregation tools. Everything described with count,　distinct, and group can be done with MapReduce, and more. It is a method of aggregation　that can be easily parallelized acro... 阅读全文

摘要： explain is an incredibly handy tool that will give you lots of information about your　queries. You can run it on any query by tacking it on to a cursor. explain returns a　document, not the cursor itse... 阅读全文

摘要： The main.m file has two jobs. First, it creates a primary autorelease pool for your application.Second, it invokes the application event loop.These two elements provide critical elementsto get your ap... 阅读全文

摘要： Sometimes, you do not need all of the key/value pairs in a document returned. If thisis the case, you can pass a second argument to find (or findOne) specifying the keys youwant. This reduces both the... 阅读全文

摘要： "$set" sets the value of a key. If the key does not yet exist, it will be created. This canbe handy for updating schema or adding user-defined keys.　　The "$inc" modifier can be used to change the valu... 阅读全文

摘要： Designed for humans first and machines second, microformats are a set of simple, open data formats built upon existing and widely adopted standards. Instead of throwing away what works today, microfor... 阅读全文

摘要： Rabin–Karp string search algorithmfunction RabinKarp(string s[1..n], string sub[1..m])hsub := hash(sub[1..m]); hs := hash(s[1..m])for i from 1 to n-m+1if hs = hsubif s[i..i+m-1] = subreturn ihs ... 阅读全文