Hi ORC stores nested fields as separate columns. For example: The following table create table orc_nested (key string, nested struct<k:string,v:string>, zip long) stored as orc; will be flattened and stored as separated columns like below key, nested, nested.k, nested.v, zip
you can have a look at the structure of ORC files using "hive —orcfiledump” utility. With regard to your next question, predicate pushdown is not supported for complex types at this point. There is a JIRA already for supporting it https://issues.apache.org/jira/browse/HIVE-7214 At this point, schema 2 will make you enable predicate pushdown. The performance difference depends mainly on the data layout/if column is sorted or not. Thanks Prasanth Jayachandran On Sep 8, 2014, at 6:16 AM, Abhishek Agarwal <abhishc...@gmail.com> wrote: > Hi all, > I have few questions with regards to nested columns in Hive. > > How does ORC internally stores the complex types such as a struct? Are the > > nested fields stored as separate columns or is the whole struct is > > serialized as one column? > > > Is predicate pushdown supported for queries which access nested columns? In > > general, is there a significant performance difference in following schemas > > with regards to query execution and storage? > > Schema1: > > { > string a; > struct b { > string b1; > string b2; > } > } > > Schema 2: > { > string a; > string b.b1; > string b.b2; > } > > -- > Regards, > Abhishek Agarwal > -- CONFIDENTIALITY NOTICE NOTICE: This message is intended for the use of the individual or entity to which it is addressed and may contain information that is confidential, privileged and exempt from disclosure under applicable law. If the reader of this message is not the intended recipient, you are hereby notified that any printing, copying, dissemination, distribution, disclosure or forwarding of this communication is strictly prohibited. If you have received this communication in error, please contact the sender immediately and delete it from your system. Thank You.
