Apache Cassandra - Awesome Part 2 - Data Modelling

Gaurav Gupta — Sat, 23 Apr 2022 18:48:09 +0000

Data Modelling

Basically Before understanding the wide columnar stores, we have to first look at the way that how cassandra stores the data.
So if you are coming from RDBMS background. Then please hold your horses and i request you to forget everything about it.

Let's get to bottom up approach of understanding the Data modelling in Cassandra.

So if you have to store the information say information of user, then in that case you will have an array of String in which you have to store the data.

eg.

String[] information = new String[3];

["Gaurav","25","Post Graduation"]

but as you can see that storing information in such a way is waste. Since first you have to maintain a record of what information[0] represents and so on.

and next time you have to insert the data in the same approach.

Here comes your saviour called MAPS.
So we will assign each values with names, and then we will fetch the values by name so now ordering is not so important. Let's see how?

Going with same above example:

Map<String, String> information = new HashMap<>();
information.put("name","gaurav");
information.put("age","25");
information.put("education","Post graduation");

NAME           AGE      Education
 |              |           |
gaurav          25         PG

So now what do you think?

Is it looking ok?
Let's say i now need to store other information of user, then?

It means there is no way of unify some collection of name/value pairs.
and no way to repeat the same column name.

Because if you again do

information.put("names","joshua");

then the previous name will be lost.

So we need something that will group some of the column
values together in a distinctly addressable group.
We need a key to refer this group of columns.
We need rows.

Then if we get single row then we can get the entire column family.

So now what we need is something like this.

Map<Row(Primary Key), ColumnarClass> cassandraDataModelling = new HashMap<>();

class ColumnarClass<T>{
   Dynamic column names;
   TimeStamp; (necessary field)
}

and now the image of above data structure is:

Image Link

Cassandra defines a column family to be a logical division that associates similar data.
For example, we might have a User column family, a Hotel column family, an
AddressBook column family, and so on. In this way, a column family is somewhat
analogous to a table in the relational world.

To make it more easy and visually appealing.

User: ColumnFamily 1
 Josh: RowKey
     email: josh@ssd.com, ColumnName:Value
     age: 22 ColumnName:Value
 Gaurav: RowKey
     email: gaurav@mailcom ColumnName:Value
Vehicle: ColumnFamily 2
 Bike: RowKey
     Period: 1968-2010 ColumnName:Value

Similarly you can have a super columnar family, which is nothing but a maps of map i.e

Map<RowKey, Map<RowKey, ColumnarClass>> = new HashMap<>();

Image Link

Where a row in a column family holds a collection of name/value pairs, the super
column family holds subcolumns, where subcolumns are named groups of columns.
So the address of a value in a regular column family is a row key pointing to a column
name pointing to a value, while the address of a value in a column family of type
“super” is a row key pointing to a column name pointing to a subcolumn name
pointing to a value. Put slightly differently, a row in a super column family still contains
columns, each of which then contains subcolumns.
(This text Source came from Cassandra The definitive guide.)

So that’s the bottom-up approach to looking at Cassandra’s data model.

There is many more to this. But again you have to hold your horses and stay tuned for next Awesome Cassandra article.

If you have any suggestions or something that you feel is wrong. Feel free to drop your comments.

Thank you

Apache Cassandra - Awesome Part 1 - What is Apache Cassandra

Gaurav Gupta — Sat, 23 Apr 2022 02:26:01 +0000

Overview

Apache Cassandra is an open source, distributed, NoSQL database. It presents a partitioned wide column storage model with eventually consistent semantics.

Open source - cassandra is open licensed. Anyone can contribute in this project.
Distributed - These are the database that are stored on multiple locations either with Homogeneous or Heterogenous properties.
Link: GFG fauna
NoSQl Database - NoSQL databases (aka "not only SQL") are non-tabular databases and store data differently than relational tables. NoSQL databases come in a variety of types based on their data model. The main types are document, key-value, wide-column, and graph.

For partitioned wide column storage model, let's discuss this on next series.

Apache Cassandra - Awesome Part 0 - Beginning

Gaurav Gupta — Sat, 23 Apr 2022 02:01:53 +0000

Hi, In this series of articles we will explore that why apache cassandra is so awesome as NoSQL database.
I will be going to write each and every detail of Documentation, and If in any case if there are keywords on which i got stuck then we will start on that topic first and will follow the Depth first search mechanism.

Let's start with this series of article and hope to see you soon on the next one i.e Apache Cassandra - Awesome Part 1.

DEV Community: Gaurav Gupta

Apache Cassandra - Awesome Part 2 - Data Modelling

Apache Cassandra - Awesome Part 1 - What is Apache Cassandra

Apache Cassandra - Awesome Part 0 - Beginning