[DRILL-3572] Provide a simple interface to append metadata to files and directories (.drill)

• Type: Improvement
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Fix Version/s: Future
• Component/s: Storage - Other
• Assignee: Unassigned
• Reporter: Jacques Nadeau
• Created: 28/Jul/15 22:59
• Updated: 21/Sep/16 16:05

Description

We need a way to store small amounts of metadata about a file or a collection of files. The current thinking was a way to have a "dot drill file" that ascribes metadata to a particular asset.

Initial example file might be something that includes the following:

{
  // Drill version identifier
  version: "dd1"  
  
  // Format Plugin Configuration
  format: {  
    type: "httpd", 
    format: "%h %l %u %t \"%r\" %>s %b \"%{Referer}i\" \"%{User-Agent}i\" \"%{Cookie}i\""}
  },
  
  // Traits of underlying data (a.k.a physical properties)
  traits: [ // traits of the underlying data
    {type: "sort_nulls_first", columns: ["request.uri", "client.host"]}
    {type: "unique", columns ["abc"]}
    {type: "unqiue", columns ["xy", "zz"]}
  ],
  
  // Mappings between directory names and exposed columns
  dirs: [
    {skip: true}, // don't include this directory name in the directory path.
    {name: "year", type: "integer"},
    {name: "month", type: "integer"},
    {name: "day", type: "integer"}
  ],

  // whether or not a user can add new columns to the table through insert
  rigid_table: true
  
}

We also need to support adding more machine-generated/managed data such as statistics. That should be done using a separate file from the one that is human description.

A user should be able to ascribe this metadata directly through the file system as well as through sql commands such as

ALTER TABLE ADD METADATA ...

Issue Links

• is related to: DRILL-4417 Umbrella: Faster Metadata Queries
• is related to: DRILL-4866 Provide TABLE and PARTITION information in INFORMATION_SCHEMA for parquet tables created by Drill

Sub-Tasks

• support for format in dot drill file: Open
• support schema configuration in dot drill file: Open
• Error handling in dot drill file: Open