Cassandra

Query Overview

For more information on the Cassandra Query Language (CQL), see

https://docs.datastax.com/en/astra-db-serverless/cql/develop-with-cql.html

and

https://docs.datastax.com/en/cql/dse-6.9/develop/introduction-cql.html

Per the DataStax cassandra-driver authors guidance, only use one Client instance per keyspace or use a single Client and explicitly specify the keyspace in your queries. For other guidance see

https://docs.datastax.com/en/developer/nodejs-driver/4.7/coding-rules/index.html

Note that “DESCRIBE TABLES” and other similar requests are cqlsh commands, not CQL queries. It works in the Cassandra shell and many Cassandra-compatible GUIs, but not via the standard CQL Node.js driver.

Data Type Handling

A discussion on mapping JavaScript data types to CQL data types is at
https://docs.datastax.com/en/developer/nodejs-driver/4.7/features/datatypes/index.html

Consider a table defined using the following statements.

// Create a UDT for nested address info
CREATE TYPE IF NOT EXISTS address (
street text,
city text,
zip int
)

CREATE TABLE IF NOT EXISTS complex_items (
  id UUID PRIMARY KEY,
  name TEXT,
  age INT,
  scores LIST<FLOAT>,
  tags SET<TEXT>,
  attributes MAP<TEXT, TEXT>,
  created_at TIMESTAMP,
  active BOOLEAN,
  address FROZEN<address>
)

In the query tools the schema would be represented as shown below.

A simple query is

select * from complex_items limit 1

A sample result is shown below.

The details of the row are shown below.

Notice that the complex data structure is maintained and values are appropriate even the TIMESTAMP created_at column value. With Qarbine, there is no “flattening” or any convoluted data gymnastics needed from legacy SQL-centric approaches.

Keyspace Context

The Qarbine data service configuration may optionally specify a keyspace. When this is done the query context is within that keyspace. When a keyspace is not set then keep the following guidelines in mind:

Unquoted keyspace names are considered lowercase in Cassandra.

Use lowercase in queries or quote the name if created with mixed case.

Consider a keyspace named “myKeyspace”. Note that the case is mixed. This query

select * from myKeyspace.complex_items limit 1

results in

{"error":"Cassandra 1.0 error keyspace mykeyspace does not exist"}

This query

select * from "myKeyspace".complex_items limit 1

results in

Troubleshooting

DataStax Astra

Because Astra DB Serverless is powered by Apache Cassandra®, you can use Cassandra Query Language (CQL) to programmatically interact with your databases through the CQL shell. Information on running the CQL shell with DataStax is located at
https://docs.datastax.com/en/astra-db-serverless/databases/connection-methods-comparison.html#cql-shell

Azure Managed Cassandra

Azure Cosmos DB Data Explorer is a web-based interface that allows you to view and manage the data stored in Azure Cosmos DB. The dedicated Azure Cosmos DB Data Explorer (https://cosmos.azure.com). For more details see

https://learn.microsoft.com/en-us/azure/cosmos-db/data-explorer

For operational issues see the guides at
https://learn.microsoft.com/en-us/azure/cosmos-db/cassandra/troubleshoot-common-issues

and
https://learn.microsoft.com/en-us/azure/cosmos-db/cassandra/error-codes-solution