Cassandra Cheat Sheet

cqlsh localhost 9042DESCRIBE KEYSPACES;USE mykeyspace;DESCRIBE TABLE users;CREATE KEYSPACE mykeyspaceWITH replication = {'class': 'SimpleStrategy', 'replication_factor': 3};

CREATE TABLE users (  id UUID PRIMARY KEY,  email TEXT,  created_at TIMESTAMP);INSERT INTO users (id, email, created_at)VALUES (uuid(), '[email protected]', toTimestamp(now()));SELECT * FROM usersWHERE id = 123e4567-e89b-12d3-a456-426614174000;UPDATE users SET email = '[email protected]'WHERE id = 123e4567-e89b-12d3-a456-426614174000;

-- Set consistency level for the cqlsh sessionCONSISTENCY QUORUM;-- Row automatically expires after 3600 secondsINSERT INTO users (id, email) VALUES (uuid(), '[email protected]') USING TTL 3600;-- Check remaining TTL on a columnSELECT TTL(email) FROM usersWHERE id = 123e4567-e89b-12d3-a456-426614174000;

-- INSERT only if the row doesn't already existINSERT INTO users (id, email, created_at)VALUES (123e4567-e89b-12d3-a456-426614174000, '[email protected]', toTimestamp(now()))IF NOT EXISTS;-- Conditional UPDATE (optimistic locking on a version column)UPDATE users SET email = '[email protected]', version = 2WHERE id = 123e4567-e89b-12d3-a456-426614174000IF version = 1;-- Conditional DELETEDELETE FROM usersWHERE id = 123e4567-e89b-12d3-a456-426614174000IF email = '[email protected]';-- [applied] column in the result tells you whether the CAS succeeded

CREATE TYPE address (  street TEXT,  city TEXT,  zip TEXT);CREATE TABLE users (  id UUID PRIMARY KEY,  emails SET<TEXT>,  logins LIST<TIMESTAMP>,  attributes MAP<TEXT, TEXT>,  home_address FROZEN<address>);-- Append to a set/list without a readUPDATE users SET emails = emails + {'[email protected]'} WHERE id = 123e4567-e89b-12d3-a456-426614174000;UPDATE users SET logins = logins + [toTimestamp(now())] WHERE id = 123e4567-e89b-12d3-a456-426614174000;UPDATE users SET attributes['plan'] = 'pro' WHERE id = 123e4567-e89b-12d3-a456-426614174000;

-- BATCH only guarantees atomicity within a single partition; avoid multi-partition batches for perfBEGIN BATCH  INSERT INTO users_by_email (email, id) VALUES ('[email protected]', 123e4567-e89b-12d3-a456-426614174000);  UPDATE users SET email = '[email protected]' WHERE id = 123e4567-e89b-12d3-a456-426614174000;APPLY BATCH;-- Counter columns require a dedicated table typeCREATE TABLE page_views (  page_id TEXT PRIMARY KEY,  views COUNTER);UPDATE page_views SET views = views + 1 WHERE page_id = 'home';

from cassandra.cluster import Clusterfrom cassandra.query import SimpleStatementcluster = Cluster(['10.0.0.1', '10.0.0.2'])session = cluster.connect('mykeyspace')# Prepared statements are parsed once, reused many times — always prefer over string interpolationinsert_stmt = session.prepare("INSERT INTO users (id, email) VALUES (?, ?)")session.execute(insert_stmt, [uuid.uuid4(), '[email protected]'])# Automatic paging keeps memory bounded on large partitionsstatement = SimpleStatement("SELECT * FROM users", fetch_size=100)for row in session.execute(statement):    process(row)