[CASSANDRA-2480] Named keys / virtual columns

• Type: Sub-task
• Status: Resolved
• Priority: Normal
• Resolution: Fixed
• Fix Version/s: 0.8.1
• Component/s: Legacy/CQL
• Labels: cql
• Assignee: Pavel Yaskevich
• Reporter: Eric Evans

Authors

Pavel Yaskevich

Reviewers

Jonathan Ellis

• Created: 14/Apr/11 17:14
• Updated: 16/Apr/19 09:33
• Resolved: 11/Jun/11 01:45

Description

With the completion of CASSANDRA-2396, it is now possible to attach a name to keys (column family-wide). This could be utilized to introduce the concept of "virtual columns" in CQL. Here's how that would work:

Typically you would use the CQL keyword KEY to specify a row key, for example:

CQL 1.0

INSERT INTO cf (KEY, name1, name2) VALUES (key1, value1, value2)
-- or alternately
UPDATE cf SET name1 = value1, name2 = value2 WHERE KEY = key1

SELECT name1,name2 FROM cf WHERE KEY = key1

For CQL 1.1, that syntax would continue to work, but upon the completion of this issue it should also be possible to assign a name to the key and treat as if it were another column. For example:

CQL 1.1

INSERT INTO cf (keyname, name1, name2) VALUES (key1, value1, value2)
-- or alternately
UPDATE cf SET name1 = value1, name2 = value2 WHERE keyname = key1

-- Note how the keyname can now be used in the projection
SELECT keyname, name1, name2 FROM cf WHERE keyname = key1

-- And, there is no restriction on the order
SELECT name1, name2, keyname FROM cf WHERE keyname = key1 AND name2 = value2

The semantics will be such that the existing behavior is maintained (read: when using the KEY keyword), but if the key is named, and the name is used in a SELECT, the key's name and value will be returned in the column results, sorted according to the comparator (Note: we'll need to figure out what that means with respect to differently typed keys).