In addition to Weibo, there is also WeChat
Please pay attention
WeChat public account
Shulou
2025-04-01 Update From: SLTechnology News&Howtos shulou NAV: SLTechnology News&Howtos > Servers >
Share
Shulou(Shulou.com)05/31 Report--
Editor to share with you how to calculate the number of reduce in hive, I believe most people do not know much about it, so share this article for your reference, I hope you can learn a lot after reading this article, let's go to know it!
Hive > select count (1) from serde_regex;Automatically selecting local only mode for queryQuery ID = hadoop_20160125101917_ab5615a4-e6f1-47e3-9e97-6795c3268ceaTotal jobs = 1Launching Job 1 out of 1Number of reduce tasks determined at compile time: 1In order to change the average load for a reducer (in bytes): set hive.exec.reducers.bytes.per.reducer=In order to limit the maximum number of reducers: set hive.exec.reducers.max=In order to set a constant number of reducers: set mapreduce.job.reduces=
Formula for calculation: number of reduce = InputFileSize / bytes per reducer
There are three parameters
Hive.exec.reducers.bytes.per.reducer controls how much input a reducer can handle. Default 256M
Hive > set hive.exec.reducers.bytes.per.reducer;hive.exec.reducers.bytes.per.reducer=256000000
Hive.exec.reducers.max controls the maximum number of reducer. If input / bytes per reduce > max starts the value set by this parameter
Hive > set hive.exec.reducers.max;hive.exec.reducers.max=1009
If the parameter mapreduce.reduce.tasks is specified, it will not be calculated. It will be used for calculation.
Hive > set mapreduce.reduce.tasks;mapred.reduce.tasks=-1 above are all the contents of the article "how to calculate the number of reduce in hive". Thank you for reading! I believe we all have a certain understanding, hope to share the content to help you, if you want to learn more knowledge, welcome to follow the industry information channel!
Welcome to subscribe "Shulou Technology Information " to get latest news, interesting things and hot topics in the IT industry, and controls the hottest and latest Internet news, technology news and IT industry trends.
Views: 235
*The comments in the above article only represent the author's personal views and do not represent the views and positions of this website. If you have more insights, please feel free to contribute and share.
Continue with the installation of the previous hadoop.First, install zookooper1. Decompress zookoope
"Every 5-10 years, there's a rare product, a really special, very unusual product that's the most un
© 2024 shulou.com SLNews company. All rights reserved.