Data retrieval with Paging¶

Backendless operations returning a collection of objects automatically break up the complete result set into pages. Backendless paging uses two parameters to enable paged data retrieval:

where:

Argument	Description
`page size`	identifies how many objects a single page contains.
`offset`	identifies the position of the object from which to retrieve the number of records identified by `page size`

The diagrams below illustrate the paging process. The first diagram shows the first request to retrieve a collection of records. The request includes the parameters of 5 objects in the page, starting from offset 0:

findrequest1

To retrieve the next page of data, the client must set the offset to the index of the first not retrieved object, which is 5:

findrequest2

Important

Backendless server sets the maximum allowed value for the page size to 100 objects. The minimum value is 1. Default page size is 10

Paging using the REST API is implemented with the pageSize and offset parameters in the data retrieval URL:

https://xxxx.backendless.app/api/data/<table-name>?pageSize=XX&offset=ZZ

pageSize and offset can be used with all other parameters supported by Backendless. Suppose a data table on the server contains 200 objects. To retrieve the first page of data with 100 objects in it, use the following request:

curl "https://xxxx.backendless.app[`/api/data/Person?pageSize=100`](/api/data/Person?pageSize=100)"

The following request can retrieve the next page (the remaining 100 objects):

curl "https://xxxx.backendless.app[`/api/data/Person?pageSize=100&offset=100`](/api/data/Person?pageSize=100&offset=100)"

Codeless Reference¶

Consider the following data table called Movie that contains 8 records:

data_service_data_retrieval_with_paging_0

Suppose you want to retrieve only four records from the data table. To achieve this, you can set the value of the page size property to 4. To facilitate comparison between the data table shown above and the subsequent output, the properties parameter was utilized. It includes specific column names(movieName and totalBoxOffice) whose values should be exclusively included in the response, while disregarding all other values.

data_service_data_retrieval_with_paging_1

Important

For a detailed description of all input parameters see the Basic Object Retrieval topic of this guide.

After the Codeless Logic runs, the operation returns 4 objects from the data table:

data_service_data_retrieval_with_paging_2

Using the page offset property, you can skip a specified number of objects from the beginning of the data table and retrieve the remaining ones.

In the example below, by setting the page offset property to 4, the operation skips the first 4 objects in the data table. Consequently, it retrieves the subsequent 4 objects after the skipped ones.

To demonstrate in more detail how the page offset parameter works, an additional properties parameter was used which contains the list of column names ("movieName" and "totalBoxOffice") - This parameter instructs the operation to return values only from the specified columns, while ignoring all others.

By using the properties parameter, you will visually see which objects were returned after calling the operation.

data_service_data_retrieval_with_paging_3

The result will look as shown below after the Codeless Logic runs:

data_service_data_retrieval_with_paging_4