So far, we have been working with a database that has just a few rows, and therefore, the HTTP GET requests to the different resource collections for our RESTful Web Service don't have problems with the amount of data in the JSON body of the responses. However, this situation changes as the number of rows in the database tables increases.
Let's imagine we have 300 rows in the drones_pilots table that persists pilots. We don't want to retrieve the data for 300 pilots whenever we make an HTTP GET request to localhost:8000/pilots/. Instead, we just take advantage of the pagination features available in the Django REST framework to make it easy to specify how we want the large result sets to be split into individual pages of data. This way, each request will retrieve only one page of data, instead of the entire result set. For example, we can make the necessary configurations to retrieve only the data for a page of a maximum of four pilots.
Whenever we enable a pagination scheme, the HTTP GET requests must specify the pieces of data that they want to retrieve, that is, the details for the specific pages, based on predefined pagination schemes. In addition, it is extremely useful to have data about the total number of resources, the next page, and the previous one, in the response body. This way, the user or the application that is consuming the RESTful Web Service knows the additional requests that need to be made to retrieve the required pages.
We can work with page numbers and the client can request a specific page number in the HTTP GET request. Each page will include a maximum amount of resources. For example, if we request the first page for the 300 pilots, the web service will return the first four pilots in the response body. The second page will return the pilots from the fifth to the eighth position in the response body.
Another option is to specify an offset combined with a limit. For example, if we request a page with an offset equal to 0 and a limit of 4, the web service will return the first four pilots in the response body. A second request with an offset equal to 4 and a limit of 4 will return the pilots from the fifth to the eighth position in the response body.
Right now, each of the database tables that persist the models we have defined has a few rows. However, after we start working with our web service in a real-life production environment, we will have hundreds of competitions, pilots, drones, and drone categories. Hence, we will definitely have to deal with large result sets. We will usually have the same situation in most RESTful Web Services, and therefore, it is very important to work with pagination mechanisms.