This was because each subpanel generated a separate round-trip HTTP transaction from the browser to Sugar web server in order to fetch the related records for each represented relationship.
However, in Sugar 7.6 this behavior has been improved due to the introduction of the Bulk API.
Sugar 7 Bulk API
The Bulk API was introduced in Sugar 7.5, however the Sugar 7 client code did not start fully taking advantage of it for subpanels until the Sugar 7.6 release. It exists at the /rest/v10/bulk endpoint.
For convenience, I'm including some of the in-app documentation for the Bulk API here but you can find more detailed API docs by visiting the /rest/v10/help endpoint on a Sugar 7.6 instance.
This request will run a sequence of API requests within one query. The requests are executed sequentially and their results are returned as one response. Some requests may return failure code, that does not interrupt the execution of the batch, and the overall request will still be considered successful.
|requests||Array||The list of requests||True|
Each of the requests can have the following fields:
|url||String||The request URL, starting with version.||True|
|data||JSON String||The data for the POST/PUT body. Must be a JSON-encoded string.||False|
|headers||Array||The request headers||False|
|method||String||The HTTP method (default is GET)||False|
The response will contain an array of response objects, each of them will correspond to the individual request. The following fields are in the response objects:
|contents||Array or String||The response contents, can be JSON object or string depending on what the individual request is supposed to return.|
|headers||Array||The response headers|
|status||Integer||HTTP status code of the response. Will be 2XX for successful requests and 4XX or 5XX for errors.|
A Short Example
Imagine building an integration where you need to keep track of Accounts and Contacts that exist within the state of North Carolina. This can be done with the v10 REST API today but it requires a separate Filter API request for each the Accounts and Contacts modules. With the Bulk API, it is possible to combine the two requests into a single HTTP transaction.
POST /v10/rest/bulkRequest Body
An important thing that should be pointed out for Bulk API requests. When using the data property, the contents needs to be a JSON encoded string. This means that JSON request bodies appear to be double encoded when used as part of a Bulk API sequence which explains the escaped quote marks in the example above.
When passing JSON data via Bulk API, this JSON data will need to contained within a JSON encoded string.Response
When parsing result array from a Bulk API request, the actual response bodies are stored under the contents properties. Also keep in mind the order requests are listed since each request is executed in turn. If you make an update in the first request, later requests in the sequence will be affected by that update.
The Bulk API executes requests in array order sequence but returns all responses at once.
Taking advantage of Bulk API to improve performance
Using the Bulk API will have immediate beneficial impact for any long sequence of API calls. It eliminates a lot of network roundtrip overhead that can be a real bottleneck for higher latency connections. This benefit should be evident by the improved responsiveness of subpanels in Sugar 7.6. But really where it shines is in clients or interfaces that need to move CRM data around in real time.
The Bulk API is the ideal solution when you need to move a lot of data in real time.
It is also easy to adopt as a standard gateway for the Sugar API since it can be used to execute a single request at a time. So even if you don't have a need for bulk transactions all the time, you can allow yourself flexibility to support them as needed.