Group By Query In Mongodb

Recently MongoDB in hack news is frequently shot. Many people even claim to hate Mongodb,david Mytton on his blog to expose MongoDB many existing problems. But those who hate have a lot in common, as a comeback: Russell Smith brings a summary of years of work experience. Russell Smith has worked as an OPS and a large website scaling advisor and has helped Guardian, Experian and many other companies, MongoDB Lond ...

MongoDB is currently the best document-oriented free Open-source NoSQL database. If you are preparing to participate in a technical interview for the MongoDB NoSQL database, you might want to look at the following MongoDB NoSQL interview questions and answers. These MongoDB NoSQL interview questions cover the basic concepts of NoSQL databases, replication (Replication), fragmentation (Sharding), Transactions and locks, trace analysis Tools (Profiler), nuances, and logging features. Let's look at the following ...

1.count Count returns the number of documents in the collection &http://www.aliyun.com/zixun/aggregation/37954.html ">nbsp;db.refactor.count () No matter how large the collection is, the number of documents can be returned quickly. You can pass the query, MongoDB calculates the number of query results Db.refactor.count ({...).

MongoDB released the 1.6.0 version, which is the fourth major stable version of the 1.0,1.2,1.4 version, and released the 1.6.1 release on August 17. This release focuses on enhanced dynamic expansion (Scale-out) features, http://www.aliyun.com/zixun/aggregation/14273.html ">sharding functionality is already available in the production environment." Use both horizontal and replication collections (replica sets ...).

In the past few years, relational databases have been the only choice for data persistence, and data workers are considering only filtering in these traditional databases, such as SQL Server, Oracle, or MySQL. Even make some default choices, such as using. NET will typically choose SQL Server, and Java may be biased toward Oracle,ruby, Mysql,python is PostgreSQL or MySQL, and so on. The reason is simple: In the past a long time, the relational database is robust ...

Introduction with the advent of the cloud computing era, various types of Internet applications are emerging, the relevant data model, distributed architecture, data storage and other database related technical indicators also put forward new requirements. Although the traditional relational database has occupied the unshakable position in the data storage, but because of its inherent limitation, has been unable to satisfy the cloud computing age to the data expansion, reads and writes the speed, the support capacity as well as the construction and the operation cost request. The era of cloud computing has put forward a new demand for database technology, which is mainly manifested in the following aspects. Mass data processing: to ...

"Guide" the author (Xu Peng) to see Spark source of time is not long, note the original intention is just to not forget later. In the process of reading the source code is a very simple mode of thinking, is to strive to find a major thread through the overall situation. In my opinion, the clue in Spark is that if the data is processed in a distributed computing environment, it is efficient and reliable. After a certain understanding of the internal implementation of spark, of course, I hope to apply it to practical engineering practice, this time will face many new challenges, such as the selection of which as a data warehouse, HB ...

After Facebook abandoned Cassandra, HBase 0.89 was given a lot of stability optimizations to make it truly an industrial-grade, structured data storage retrieval system. Facebook's Puma, Titan, ODS time Series monitoring system uses hbase as a back-end data storage System. 　　HBase is also used in some projects of domestic companies. HBase subordinate to the Hadoop ecosystem, from the beginning of the design of the system is very focused on the expansion of the dynamic expansion of the cluster, load are ...

As global corporate and personal data explode, data itself is replacing software and hardware as the next big "oil field" driving the information technology industry and the global economy. Compared with the fault-type information technology revolution such as PC and Web, the biggest difference of large data is that it is a revolution driven by "open source software". From giants such as IBM and Oracle to big data start-ups, the combination of open source software and big data has produced astonishing industrial subversion, and even VMware's past reliance on proprietary software has embraced big Open-source data ...

"IT168" I have always felt that nosql in fact very easy to understand, I have also had a very in-depth study of NoSQL, but in the recent preparation of yuntable chart, found that NoSQL not only very profound, 　　And my personal understanding of NoSQL is only superficial, but I am still a "shame and then Yong" people, so after a period of study, from the sixth part of this series, will talk to you nosql, and this article will be the main to do a NoSQL database review. ...