In this post, I am sharing small demonstration to create CQL User Defined Data Type in Cassandra.

Using user defined data types, you can handle multiple fields into one user-defined column.
For example, You can create user-defined data type for Address related columns, in which you can specify a Street name, City name, Pincode, etc.

Create Keyspace if not exists:

CREATE KEYSPACE IF NOT EXISTS dbrnd WITH replication = {'class': 'SimpleStrategy', 'replication_factor' : 3};

Use a Keyspace:

USE dbrnd;

Create user defined data type:

CREATE TYPE dbrnd.EmployeeAddress
(
    StreetName TEXT
    ,CityName TEXT
    ,ZipCode INT
);

Create sample table:
frozen is require to define a column.

CREATE TABLE dbrnd.tbl_EmployeeInfo
(
    EmpID INT PRIMARY KEY
    ,EmpName VARCHAR
    ,EmpAddress frozen<EmployeeAddress>
);

Insert sample records:

INSERT INTO dbrnd.tbl_EmployeeInfo 
(EmpID,EmpName,EmpAddress)
VALUES
(1,'Anvesh',{StreetName:'Kondapuar', CityName:'Hyderabad', ZipCode:580084});

INSERT INTO dbrnd.tbl_EmployeeInfo 
(EmpID,EmpName,EmpAddress)
VALUES
(2,'Neevan',{StreetName:'Hilldrive', CityName:'Bhavnagar', ZipCode:364002});

Select properties of User defined data type column:

cassandra@cqlsh:dbrnd> SELECT EmpAddress.StreetName FROM dbrnd.tbl_EmployeeInfo;

@ Row 1
-----------------------+-----------
 empaddress.streetname | Kondapuar

@ Row 2
-----------------------+-----------
 empaddress.streetname | Hilldrive

(2 rows)

In this post, I am sharing basic help to execute multiple statements using one single Cassandra batch.

Many times, it is required to execute multiple statements using single batch.
Cassandra CQL provides the BEGIN BATCH…APPLY BATCH command to execute multiple statements.

Below is a small demonstration:

Create Keyspace if not exists:

CREATE KEYSPACE IF NOT EXISTS dbrnd WITH replication = {'class': 'SimpleStrategy', 'replication_factor' : 3};

USE dbrnd;

CREATE TABLE IF NOT EXISTS tbl_Employee 
(
  EmpID INT PRIMARY KEY
  ,EmpFirstName VARCHAR
  ,EmpLastName VARCHAR
  ,EmpSalary INT
);

INSERT INTO tbl_Employee 
(EmpID,EmpFirstName,EmpLastName,EmpSalary)
VALUES
(1,'Anvesh','Patel',50000);

INSERT INTO tbl_Employee 
(EmpID,EmpFirstName,EmpLastName,EmpSalary)
VALUES
(2,'Neevan','Patel',150000);

cassandra@cqlsh:dbrnd> 
    begin batch
         INSERT INTO tbl_Employee
         (EmpID,EmpFirstName,EmpLastName,EmpSalary)
         VALUES
         (3,'Meera','Patel',80000);
         UPDATE tbl_Employee SET EmpFirstName ='Martin' WHERE EmpID=2;
         
         DELETE FROM tbl_Employee WHERE EmpID=3;
    apply batch;

cassandra@cqlsh:dbrnd> SELECT *FROM tbl_Employee;

@ Row 1
--------------+--------
 empid        | 1
 empfirstname | Anvesh
 emplastname  | Patel
 empsalary    | 50000

@ Row 2
--------------+--------
 empid        | 2
 empfirstname | Martin
 emplastname  | Patel
 empsalary    | 150000

(2 rows)

JSON + RDBMS is one of the interesting topics, in the new version of SQL Server 2016 we can store JSON formatted data.

Now a day JSON data type is a standard feature for all new coming RDBMS product versions like PostgreSQL 9.4, and MySQL 5.7 have already introduced this.

Now We can say, we have SQL Server 2016 with the RDBMS + NoSQL concepts.
We can store JSON data as nvarchar, but the JSON related functions have the advantage of enforcing that each stored value is valid according to the JSON rules.

Small demonstration on SQL Server 2016 JSON:

Create a sample table and define two column as NVARCHAR to store JSON data:

CREATE TABLE tbl_TestSQLJSON
(
	ID INTEGER PRIMARY KEY
	,DepartmentName VARCHAR(250)
	,EmployeeName NVARCHAR(MAX)
	,EmployeeAddress NVARCHAR(MAX)
)
GO

Use ISJSON() and add check constraint in json columns:
If your json format and document is correct, It returns true other It returns false.

ALTER TABLE tbl_TestSQLJSON
ADD CONSTRAINT ck_tbl_TestSQLJSON_EmployeeName
CHECK (ISJSON( EmployeeName ) > 0)
GO

ALTER TABLE tbl_TestSQLJSON
ADD CONSTRAINT ck_tbl_TestSQLJSON_EmployeeAddress
CHECK (ISJSON( EmployeeAddress ) > 0)
GO

Insert few sample JSON data:

INSERT INTO tbl_TestSQLJSON
VALUES 
(
	1
	,'Sales'
	,N'{"firstName": "Anvesh", "lastName": "Patel"}'
	,N'
	{"address" : 
		{ 
			"India": "Hyderabad"
			,"USA": "Newyork"
		}
	}'
)
,(
	2
	,'Production'
	,N'{"firstName": "Neevan", "lastName": "Patel"}'
	,N'
	{"address" : 
		{ 
			"India": "Ahmedabad"
			,"USA": "Washington DC"
		}
	}'
)
,(
	3
	,'Animation'
	,N'{"firstName": "Eric", "lastName": "Lorn"}'
	,N'
	{"address" : 
		{ 
			"India": "Mumbai"
			,"USA": "Chicago"
		}
	}'
)
GO

SELECT json data:

SELECT 
	ID
	,DepartmentName
	,JSON_VALUE(EmployeeName, '$.firstName') AS EmployeeFirstName     
	,JSON_VALUE(EmployeeAddress, '$.address.India') AS AddressIndia
	,JSON_VALUE(EmployeeAddress, '$.address.USA') AS AddressUSA
	,JSON_QUERY(EmployeeAddress, '$.address') AS EmployeeAddressJSON
FROM tbl_TestSQLJSON
GO

Use JSON_VALUE() in WHERE Clause:

SELECT 
	ID
	,DepartmentName
	,JSON_VALUE(EmployeeName, '$.firstName') AS EmployeeFirstName     	
FROM tbl_TestSQLJSON
WHERE JSON_VALUE(EmployeeName, '$.firstName') = 'Anvesh'
GO

This is one of the interesting topics, in the new version of MySQL 5.7 we can store JSON formatted data.
Now a day JSON data type is a common feature for all new coming RDBMS product versions like: PostgreSQL 9.4 and SQL Server 2016 have already introduced this.

Now We can say, we have MySQL 5.7 with the RDBMS + NOSQL concepts.

We can store JSON data as strings, but the JSON Data types have the advantage of enforcing that each stored value is valid according to the JSON rules.

The size of JSON documents stored in JSON columns is limited to the value of the max_allowed_packet system variable.

The JSON columns cannot have a default value.

MySQL 5.7 also introduced a different function to manipulate and manage JSON data in MySQL.
Tomorrow, I will demonstrate these functions.

Small demonstration JSON Data Type:
Create table with JSON Data type:

CREATE TABLE tbl_TestJSON
(
	ID INTEGER PRIMARY KEY
	,DepartName VARCHAR(250)
	,EmployeeDetails JSON
	,Address JSON
);

Insert few sample record:

INSERT INTO tbl_TestJSON
VALUES 
(
	1
	,'Sales'
	,'{"firstName": "Anvesh", "lastName": "Patel"}'
	,'{"address" : "Hyderabad"}'
)
,(
	2
	,'Production'
	,'{"firstName": "Neevan", "lastName": "Patel"}'
	,'{"address" : "Ahmedabad"}'
)
,(
	3
	,'Animation'
	,'{"firstName": "Eric", "lastName": "Lorn"}'
	,'{"address" : "USA"}'
);

You can search key value in WHERE clause:

SELECT *FROM tbl_TestJSON 
WHERE EmployeeDetails->"$.firstName"="Neevan";

In this post, I am sharing an important list of Cassandra System Tables.

Cassandra DBA can use these tables for a different investigation like, Schema information, Roles information, Tracing information and others.

There are different keyspaces are available like, system, system_auth, system_schema, system_traces.

system_auth Keyspace:

SELECT *FROM system_auth.roles;
SELECT *FROM system_auth.role_permissions;

SELECT *FROM system_schema.views;
SELECT *FROM system_schema.types;
SELECT *FROM system_schema.triggers;
SELECT *FROM system_schema.tables;
SELECT *FROM system_schema.keyspaces;
SELECT *FROM system_schema.indexes;
SELECT *FROM system_schema.functions;
SELECT *FROM system_schema.columns;
SELECT *FROM system_schema.dropped_columns;
SELECT *FROM system_schema.aggregates;

SELECT *FROM system_traces.sessions;
SELECT *FROM system_traces.events;

SELECT *FROM system.available_ranges;
SELECT *FROM system.peers;
SELECT *FROM system.peer_events;
SELECT *FROM system.batchlog;
SELECT *FROM system.batches;

In this post, I am sharing a list of important CQL shell commands of the Cassandra.

Get the help of all commands:

cassandra@cqlsh:dbrnd> help

Check the host and version:

cassandra@cqlsh:dbrnd> show host
Connected to Test Cluster at 127.0.0.1:9042.
cassandra@cqlsh:dbrnd> show version
[cqlsh 5.0.1 | Cassandra 3.5 | CQL spec 3.4.0 | Native protocol v4]

Check the cluster information:

cassandra@cqlsh:dbrnd> describe cluster;

Cluster: Test Cluster
Partitioner: Murmur3Partitioner

Range ownership:
                     7198801157164107876  [127.0.0.1]
                    -6388269565477727734  [127.0.0.1]
                      -13424558412243369  [127.0.0.1]

Check the keyspaces:

cassandra@cqlsh:dbrnd> describe keyspaces;

tutorialspoint  system_auth  dbrnd               test
system_schema   system       system_distributed  system_traces

Check the user defined tables:

cassandra@cqlsh:dbrnd> describe tables;

tbl_employee  tbl_department  users

Check the user defined types:

cassandra@cqlsh:dbrnd> describe types

sports_details sport

Check the consistency level:

cassandra@cqlsh:dbrnd> consistency
Current consistency level is ONE.

Make your table output expanded:

cassandra@cqlsh:dbrnd> expand on
Now Expanded output is enabled
cassandra@cqlsh:dbrnd> select *from tbl_employee;

@ Row 1
--------------+--------
 empid        | 1
 empfirstname | Anvesh
 emplastname  | Patel
 empsalary    | 50000

@ Row 2
--------------+--------
 empid        | 2
 empfirstname | Neevan
 emplastname  | Patel
 empsalary    | 150000

(2 rows)

In this post, I am sharing an important list of ports which are used by the Cassandra for a different purpose.

Cassandra developer has to know about these ports because it is very important while they are configuring the firewall for Cassandra server.

9160: Cassandra Thrift client API
9042: Cassandra native client port

7000: Cassandra Internode cluster communication (not used if TLS enabled)
7001: Cassandra SSL Internode cluster communication.
7199 / 8080: JMX monitoring port

61620: Cassandra OpsCenter monitoring port
61621: Cassandra OpsCenter agent port

8888: OpsCenter browser http request

Prior to Cassandra 2.2, it supports only User base authentication, but now Cassandra introduces new Role-based authentication.

In this post, I am sharing a demonstration on how to create a Role in Cassandra and How to assign different permissions to that role.
You can directly use this Role for authentication and you can also assign same Role permission to another role.

First, login with Cassandra’s super user.

cqlsh -u cassanddra -p cassandra

Create keyspace if not exists:

CREATE KEYSPACE IF NOT EXISTS dbrnd WITH replication = {'class': 'SimpleStrategy', 'replication_factor' : 3};

USE dbrnd;

Create few sample tables:

CREATE TABLE IF NOT EXISTS tbl_Employee 
(
	EmpID INT PRIMARY KEY
	,EmpFirstName VARCHAR
	,EmpLastName VARCHAR
	,EmpSalary INT
);

CREATE TABLE IF NOT EXISTS tbl_Department
(
	DeptID INT PRIMARY KEY
	,DeptName VARCHAR
);

Create one sample Role without Superuser access:
If you get this error : “org.apache.cassandra.auth.CassandraRoleManager doesn’t support PASSWORD”, visit this solution.

CREATE ROLE ReportingRole WITH PASSWORD = 'pass123' AND LOGIN = true AND SUPERUSER = false;

Grant different permissions to this Role:

GRANT SELECT ON dbrnd.tbl_Employee TO ReportingRole;
GRANT MODIFY ON dbrnd.tbl_Department TO ReportingRole;

If you get any error like ” GRANT operation is not supported by AllowAllAuthorizer”, you have to modify the value of “authorizer” in cassandra.yaml file.

-- Old value:
 authorizer: AllowAllAuthorizer
 
 -- Change to this New value:
 authorizer: org.apache.cassandra.auth.CassandraAuthorizer

Grant over the all keyspaces:

GRANT SELECT ON ALL KEYSPACES TO ReportingRole;
GRANT MODIFY ON ALL KEYSPACES TO ReportingRole;

Create new test Role and make it a replica of the current role:

CREATE ROLE Test WITH PASSWORD = 'pass123' AND LOGIN = true AND SUPERUSER = false;

GRANT ReportingRole to Test;

List out all Roles and its permissions:

-- List out all Roles.
LIST ROLES;
-- List out all permissions of the Role.
LIST ALL PERMISSIONS OF ReportingRole;

Last week, I was creating my first database User and Role, but I got the below error in Cassandra – InvalidRequest: code=2200 [Invalid query] message=”org.apache.cassandra.auth.CassandraRoleManager doesn’t support PASSWORD”.

For me, this is very important to resolve this problem because the application requires different database users for each process.

I tried many options to solve this error and I have found that cassandra.yaml file require to edit.
It has an authenticator parameter which has by default allow all types of authentication.

You can find this parameter and can change as mentioned below steps.

Old value:

authenticator: AllowAllAuthenticator

Change with this new value:

authenticator: PasswordAuthenticator

Restart your Cassandra service:

$ sudo service cassandra restart

Login with default admin Cassandra user:

$ cqlsh -u cassandra -p cassandra

Additionally, you can also check role manager parameter is exists or not. If below mention parameter does not exist in cassandra.yaml, you can add it.

role_manager: CassandraRoleManager

What is cassandra.yaml configuration file?

The cassandra.yaml file is the main configuration file of Cassandra. This file is very important for all kinds of Cassandra node and cluster level configurations.
After changing properties in the cassandra.yaml file, you must restart the node for getting the configuration changes.

The default location of cassandra.yaml:

The default location in linux is: /etc/cassandra.
You can open this file with admin (sudo) user and can edit this.

Basic commands to locate this file:

-- to list out all folders and files
$ ls -a	

-- change directory
$ cd /etc
$ cd cassandra

Basic commands to open this file:

$ sudo nano cassandra.yaml

After edit, Restart the cassandra service:

-- restart service
$ sudo service cassandra restart
-- after restart check the service status
$ sudo service cassandra status