How to auto generate uuid in cassandra CQL 3 command line
A UUID is a Universally Unique ID used to avoid collisions.
Cassandra 2.0.7 and later versions include the uuid()
function that takes no parameters and generates a Type 4 UUID for use in INSERT
or SET
statements.
You can also use a timeuuid
type with a function like now()
. They generate a Type 1 UUID.
The difference between Type 1 and Type 4 UUIDs is that a Type 1 UUID is generated using a timestamp and a Type 4 is generated using random numbers.
If you want to use a timeuuid
as a uuid
use something like blobAsUuid(timeuuidAsBlob(now()))
, since the value returned by now()
is guaranteed to be unique.
References:
http://docs.datastax.com/en/cql/3.3/cql/cql_reference/uuid_type_r.html
http://docs.datastax.com/en/cql/3.3/cql/cql_reference/timeuuid_functions_r.html
http://docs.datastax.com/en/cql/3.3/cql/cql_reference/blob_r.html
Actually there is a way to do that using the blob conversion functions - blobAsType()
and typeAsBlob()
. In your case this should be:
insert into stuff (uid, name) values(blobAsUuid(timeuuidAsBlob(now())), 'my name');
This converts timeuuid
to blob
and from the blob
converts it to uuid
.
You can with time uuids (type 1 UUID) using the now() function e.g.
insert into stuff (uid, name) values(now(), 'my name');
Works with uid or timeuuid. It generates a "guaranteed unique" UID value, which also contains the timestamp so is sortable by time.
There isn't such a function for type 4 UUIDs though.
UPDATE: This note pertains to older versions of Cassandra. For newer versions, see below.
As of Cassandra 2.0.7 you can just use uuid(), which generates a random type 4 UUID:
INSERT INTO users(uid, name) VALUES(uuid(), 'my name');