Sql Distinct Performance

Using hive, you can write complex MapReduce query logic efficiently and quickly. In some cases, however, the Hive Computing task can become very inefficient or even impossible to get results, because it is unfamiliar with data attributes or if the Hive optimization convention is not followed. A "good" hive program still needs to have a deep understanding of the hive operating mechanism. Some of the most familiar optimization conventions include the need to write large tables on the right side of the join, and try to use UDF instead of transfrom ... Like。 Here are 5 performance and logic ...

Hadoop is a large data distributed system infrastructure developed by the Apache Foundation, the earliest version of which was the 2003 original Yahoo! Doug cutting is based on Google's published academic paper. Users can easily develop and run applications that process massive amounts of data in Hadoop without knowing the underlying details of the distribution. The features of low cost, high reliability, high scalability, high efficiency and high fault tolerance make Hadoop the most popular large data analysis system, yet its HDFs and mapred ...

Hive in the official document of the query language has a very detailed description, please refer to: http://wiki.apache.org/hadoop/Hive/LanguageManual, most of the content of this article is translated from this page, Some of the things that need to be noted during the use process are added. Create tablecreate [EXTERNAL] TABLE [IF not EXISTS] table_name [col_name data_t ...

Hive is the most widely used SQL on Hadoop tool, and recently many major data companies have introduced new SQL tools such as Impala,tez,spark, based on column or memory hot data, although many people have a view of hive, inefficient, slow query, and many bugs. But Hive is still the most widely used and ubiquitous SQL on Hadoop tool. Taobao survey analysis of the previous report, Taobao 90% of the business run in hive above. The ratio of the storm audio and video ...

Hadoop is a large data distributed system infrastructure developed by the Apache Foundation, the earliest version of which was the 2003 original Yahoo! Dougcutting based on Google's published academic paper. Users can easily develop and run applications that process massive amounts of data in Hadoop without knowing the underlying details of the distribution. The features of low cost, high reliability, high scalability, high efficiency and high fault tolerance make Hadoop the most popular large data analysis system, yet its HDFs and mapreduc ...

"Zhongguancun Large Data Industry alliance" launched the "Big Data 100 Points" forum, at night 9 o'clock, in the "Zhongguancun Large Data Industry alliance" micro-letter group for 100 minutes of communication and discussion. Bai: As today's Speaker is the Chinese Academy of Sciences Cheng researcher, we welcome! Bai: Deputy General engineer, researcher, doctoral tutor, director of Network Science and Technology Key Laboratory, Institute of Technology, Chinese Academy of Sciences. As the Chinese Academy of Sciences, the Internet high-performance software and algorithm theory, network search, network information security direction of the team leader and discipline leader, led group ...

"Zhongguancun Large Data Industry alliance" launched the "Big Data 100 Points" forum, at night 9 o'clock, in the "Zhongguancun Large Data Industry alliance" micro-letter group for 100 minutes of communication and discussion. Bai: As today's Speaker is the Chinese Academy of Sciences Cheng researcher, we welcome! Bai: Deputy General engineer, researcher, doctoral tutor, director of Network Science and Technology Key Laboratory, Institute of Technology, Chinese Academy of Sciences. As the Chinese Academy of Sciences, the Internet high-performance software and algorithm theory, network search, network information security direction of the team leader and discipline leader, led group ...

Although the "editor's note" has been available for 9 years, the popularity of Mongodb,hamsterdb is still lacking, and it has been rated as a Non-mainstream database. Hamsterdb is an open source key value type database. However, unlike other Nosql,hamsterdb, which are single-threaded and not distributed, they are designed to be more like a column store database, while also supporting acid transactions at the Read-committed isolation level. Then compare Leveldb,hamsterdb will have any advantage, here we go ...

Facebook officially announces open source presto--data query engine, which enables fast interactive analysis of more than 250PB of data. The project began to be developed in the autumn of 2012 and is currently being used by more than 1000 http://www.aliyun.com/zixun/aggregation/1560.html ">facebook employees, running over 30000 Queries, daily data at 1PB level. Fa ...

Facebook officially announces open source presto--data query engine, which enables fast interactive analysis of more than 250PB of data. The project, which began development in the fall of 2012, has been used by more than 1000 Facebook employees, running more than 30,000 queries, with daily data at 1PB levels. Facebook says Presto's performance is 10 times times better than Hive and Map*reduce. Prest ...