Raghu Angadi commented on PIG-993:

API  is pretty simple : {code}
class org.apache.hadoop.zebra.BasicTable {
 /** see the patch for JavaDoc and attached example for usage */

public static void dropColumnGroup(Path path,
                                   Configuration conf,   String cgName)
                               throws IOException { ... }

  * Table schema is not modified.  
  * this API takes a name for a column group. PIG-986 adds explicit names for 
  * Once a CGs is deleted, NULL is returned for the fields that were stored in 
the CG. 
     ** This is the main difference between just manually deleting  a directory 
on filesystem and 'properly' deleting a CG.
     ** Many changes made in other parts of zebra are related to handling the 
missing CGs.

> [zebra] Abitlity to drop a column group in a table
> --------------------------------------------------
>                 Key: PIG-993
>                 URL: https://issues.apache.org/jira/browse/PIG-993
>             Project: Pig
>          Issue Type: Bug
>            Reporter: Raghu Angadi
>            Assignee: Raghu Angadi
>             Fix For: 0.5.0
> A Zebra table is stored as multiple sub tables each containing a set of 
> columns called column group (CG). The user specifies how these columns are 
> grouped while creating a table through the _storage hint_.
> For some of the large tables, it might be necessary for users to remove a set 
> of columns and retain the rest. This jira provides a way for users to delete 
> an entire column group. 
> The following comments will have more details on API and the semantics. 

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