cqlsh

interactive Cassandra Query Language shell

TLDR

Start CQL shell

$ cqlsh

Connect to remote host

$ cqlsh [hostname] [9042]

Connect with authentication

$ cqlsh -u [username] -p [password]

Execute CQL from file

$ cqlsh -f [script.cql]

Execute single statement

$ cqlsh -e "SELECT * FROM [keyspace].[table]"

Check node status

$ nodetool status

View cluster info

$ nodetool info

Repair a node

$ nodetool repair

SYNOPSIS

cqlsh [options] [host] [port]nodetool [options] command [args]

cqlsh is the Cassandra Query Language shell for executing CQL statements interactively or from scripts. nodetool manages Cassandra node operations.CQL resembles SQL with some differences. Keyspaces are like databases; tables have partition keys and clustering columns. Queries must include partition key for efficient lookups.nodetool status shows cluster health with Up/Down/Normal/Leaving/Joining states and token ownership. nodetool repair ensures data consistency across replicas.Snapshots create hard-linked backups of SSTables for point-in-time recovery. cleanup removes data after topology changes. compact forces SSTable compaction.Node lifecycle operations: drain prepares for shutdown, decommission removes node from cluster streaming data to others.

CONFIGURATION

~/.cassandra/cqlshrc

User-specific cqlsh settings including connection defaults, display formatting, and authentication credentials.

/etc/cassandra/cassandra.yaml

Main Cassandra configuration file controlling cluster behavior, data directories, network settings, and replication.

CQLSH PARAMETERS

-u, --username user

Authentication username.

-p, --password pass

Authentication password.

-k, --keyspace keyspace

Initial keyspace.

-f file

Execute CQL file.

-e statement

Execute single CQL statement.

--ssl

Use SSL connection.

--connect-timeout secs

Connection timeout.

--request-timeout secs

Query timeout.

NODETOOL COMMANDS

status

Show cluster node status.

info

Node information.

ring

Token ring information.

repair [keyspace]

Run anti-entropy repair.

cleanup [keyspace]

Remove data not belonging to node.

compact [keyspace]

Force compaction.

flush [keyspace]

Flush memtables to SSTables.

snapshot [name]

Take snapshot backup.

decommission

Decommission the node.

drain

Drain node for shutdown.

describecluster

Cluster information.

CAVEATS

CQL is not SQL; avoid joins and complex queries. Wide partitions impact performance. Repair is resource-intensive; schedule appropriately. Decommission before removing nodes. Authentication default is off.

HISTORY

Apache Cassandra was initially developed at Facebook for inbox search and open-sourced in 2008. It became an Apache project in 2009 and top-level in 2010. Cassandra combines Dynamo's distribution model with Bigtable's data model. DataStax was founded in 2010 to provide commercial support. Version 4.0 (2021) brought major improvements after extensive testing.