Check the threads in hive user group under “Impact of partitioning on certain queries”
HTH Dr Mich Talebzadeh LinkedIn https://www.linkedin.com/profile/view?id=AAEAAAAWh2gBxianrbJd6zP6AcPCCdOABUrV8Pw Sybase ASE 15 Gold Medal Award 2008 A Winning Strategy: Running the most Critical Financial Data on ASE 15 http://login.sybase.com/files/Product_Overviews/ASE-Winning-Strategy-091908.pdf Author of the books "A Practitioner’s Guide to Upgrading to Sybase ASE 15", ISBN 978-0-9563693-0-7. co-author "Sybase Transact SQL Guidelines Best Practices", ISBN 978-0-9759693-0-4 Publications due shortly: Complex Event Processing in Heterogeneous Environments, ISBN: 978-0-9563693-3-8 Oracle and Sybase, Concepts and Contrasts, ISBN: 978-0-9563693-1-4, volume one out shortly http://talebzadehmich.wordpress.com <http://talebzadehmich.wordpress.com/> NOTE: The information in this email is proprietary and confidential. This message is for the designated recipient only, if you are not the intended recipient, you should destroy it immediately. Any information in this message shall not be understood as given or endorsed by Peridale Technology Ltd, its subsidiaries or their employees, unless expressly so stated. It is the responsibility of the recipient to ensure that this email is virus free, therefore neither Peridale Technology Ltd, its subsidiaries nor their employees accept any responsibility. From: Shubhvardhan Manjayya [mailto:shub...@gmail.com] Sent: 27 January 2016 04:14 To: user@hive.apache.org Subject: Partition performance Hi see this cloudera blog at: http://blog.cloudera.com/blog/2014/08/improving-query-performance-using-partitioning-in-apache-hive/ That mentions "Do not over-partition the data. With too many small partitions, the task of recursively scanning the directories becomes more expensive than a full table scan of the table." If I have two tables with this partition structure: 1. table1 pointing to hdfs location /c1/c2/data 2. table2 pointing to hdfs location /c1/c2/c3/data and hadoop fs -du -h -s /c1 has the same result for both these, and the files are splitttable, snappy compressed, when I compare the two queries, select count(1) from table1; select count(1) from table2; For which usecases do the two queries have different execution time? I am guessing both should perform the same always as long as we dont use the c3 partitioned column in the where clause? -- -Shubh
