Cassandra Data Types:
Apache Cassandra data types are of different kinds. I will explain all data types one by one that the latest version Cassandra supports. Cassandra Query Language provides rich set of data types including different kind of collection. CQL also provide user the facility to create custom data types in Cassandra along with these pre-defined data types. The table below shows the pre-defined data types and their descriptions.
| Data Type | Constants | Description |
| Int | Integers | To store 32 bit signed integer |
| Bigint | Integers | Represents 64-bit signed long |
| Varint | Integers | Represents Arbitrary precision integer |
| Float | Integers, floats | To Store 32-bit floating point number |
| Double | Integers, floats | To Store 64-bit floating point number |
| Decimal | Integers, floats | Variable precision decimal |
| Counter | Integers | Distributed counter values 64 bit |
| Boolean | Booleans | Represents True or false value |
| Varchar | Strings | UTF-8 encoded string |
| Text | Strings | UTF-8 encoded strings |
| Inet | Strings | To Store IP address in IPV4 or IPV6 format |
| ascii | Strings | US-Ascii character string |
| Blob | Blobs | Arbitrary bytes in hexadecimal |
| Frozen | Tuples, collections, user defined types | Stores cassandra types |
| Tuple | A group of 2,3 fields | |
| List | Collection of elements | |
| Set | Collection of elements | |
| Map | Json style collection of elements | |
| Uuid | Uuids | Standard uuid |
| Timeuuid | Uuids | Type 1 uuid |
| Timestamp | Integers, strings | Id generated with date plus time |
Cassandra User-defined data types:
Cassandra Query Language also provides privileges to users to create their own data types based on their data. I have explains some Cqlsh command for dealing with user defined data types.
- CREATE TYPE – This command is used to create a user-defined DataType.
- DROP TYPE – Command used to drops a user-defined Data Type.
- ALTER TYPE – To modify a user-defined Data Type.
- DESCRIBE TYPE – To Describes a user-defined Data Type.
Collection Types in Cassandra Query Language (CQL):
Cassandra Query Language (CQL) also provides a collection data type to store object like data in Cassandra nosql database. The table below provides a list of Collections available in Cassandra Query Language.
| Collection | Description |
| set | Collection of one or more elements. |
| map | A collection of key-value pairs. |
| list | Collection of one or more ordered elements. |
Cassandra Automatic Data Expiration
Time to live (TTL) in Cassandra
Apache Cassandra also provides the facility of TTL. A user can set time to live property of each data record. It means that data record is expired after a certain time period. That you have already set while inserting data in Cassandra.
While inserting data on each record you have to set the “ttl” time to live time in seconds. After that much of time Cassandra automatically removes that data record. You can set the time from 1 second to many days.
For example, if you set ttl value 100 seconds while inserting a data record. The Data record will automatically be deleted as 100 seconds passes. When ttl time elapsed, that data record is marked with a tombstone.
A tombstone exists for a grace period. During compaction process data is permanently deleted from database.
Syntax for Cassandra Time to Live (TTL):
Insert
into KeyspaceName.TableName(ColumnNames) values(ColumnValues)
using ttl TimeInseconds;
Execution of Cassandra TTL
Here is the screenshot of data insertion example where data is being inserted in Student table with ttl value of 150 seconds.
Here is the screenshot which shows data expiration. Data is expired after 150 seconds and data is removed after the time elapsed.
See Also :
Cassandra Data Model
Cassandra Architecture
Download and install Cassandra
Cassandra Cluster setup
Summary:
This article briefly explain the Apache Cassandra data types as well as user defined data types in Cassandra nosql database. Cassandra query language commands for user defined data types to create alter and drop as well as describe the user defined data types. Cassandra time to live (TTL) property as well as collection data types in cassandra.