Using lightweight transactions

INSERT and UPDATE statements that use the IF clause support lightweight transactions, also known as Compare and Set (CAS).

INSERT and UPDATE statements using the IF clause support lightweight transactions, also known as Compare and Set (CAS). A common use for lightweight transactions is an insertion operation that must be unique, such as a cyclist's identification. Lightweight transactions should not be used casually, as the latency of operations increases fourfold due to the due to the round-trips necessary between the CAS coordinators.

Cassandra 2.1.1 and later support non-equal conditions for lightweight transactions. You can use <, <=, >, >=, != and IN operators in WHERE clauses to query lightweight tables.

It is important to note that using IF NOT EXISTS on an INSERT, the timestamp will be designated by the lightweight transaction, and USING TIMESTAMP is prohibited.

Procedure

  • Insert a new cyclist with their id. 
    cqlsh> INSERT INTO cycling.cyclist_name (id, lastname, firstname)
  VALUES (4647f6d3-7bd2-4085-8d6c-1229351b5498, 'KNETEMANN', 'Roxxane')
  IF NOT EXISTS;
  • Perform a CAS operation against a row that does exist by adding the predicate for the operation at the end of the query. For example, reset Roxane Knetemann's firstname because of a spelling error. 
    cqlsh> UPDATE cycling.cyclist_name
  SET firstname = ‘Roxane’
  WHERE id = 4647f6d3-7bd2-4085-8d6c-1229351b5498
  IF firstname = ‘Roxxane’;