Hello, the file format topic is still confusing me and I would appreciate if you could share your thoughts and experience with me.
>From reading different books/articles/websites I understand that - Sequence files (used frequently but not only for binary data), - AVRO, - RC (was developed to work best with Hive -columnar storage) and - ORC (a successor of RC to give Hive another performance boost - Stinger initiative) are all container file formats to solve the "small files problem" and all support compression and splitting. Additionally, each file format was developed with specific features/benefits in mind. Imagine I have the following text source data - 1 TB of XML documents (some millions of small files) - 1 TB of JSON documents (some hundred thousands of medium sized files) - 1 TB of Apache log files (some thousands of bigger files) How should I store this data in HDFS to process it using Java MapReduce and Pig and Hive? I want to use the best tool for my specific problem - with "best" performance of course - i.e. maybe one problem on the apache log data can be best solved using Java MapReduce, another one using Hive or Pig. Should I simply put the data into HDFS as the data comes from - i.e. as plain text files? Or should I convert all my data to a container file format like sequence files, AVRO, RC or ORC? Based on this example, I believe - the XML documents will be need to be converted to a container file format to overcome the "small files problem". - the JSON documents could/should not be affected by the "small files problem" - the Apache files should definitely not be affected by the "small files problem", so they could be stored as plain text files. So, some source data needs to be converted to a container file format, others not necessarily. But what is really advisable? Is it advisable to store all data (XML, JSON, Apache logs) in one specific container file format in the cluster- let's say you decide to use sequence files? Having only one file format in HDFS is of course a benefit in terms of managing the files and writing Java MapReduce/Pig/Hive code against it. Sequence files in this case is certainly not a bad idea, but Hive queries could probably better benefit from let's say RC/ORC. Therefore, is it better to use a mix of plain text files and/or one or more container file formats simultaneously? I know that there will be no crystal-clear answer here as it always "depends", but what approach should be taken here, or what is usually used in the community out there? I welcome any feedback and experiences you made. Thanks
