Explore API

[OpenSource03]

Description

Please consider implementing some kind of API for the Explore view.

It should be easy to retrieve data from Druid in a structured way - such as Pivot (probably the most important), time chart, bar chart etc. As instance, Pivot may respond with Table columns and rows, pie chart would respond with percentages of each grouped dimension, bar chart would similarly also respond with the the grouped destination -> metric value key pair etc.

Motivation

While I see that some of these can easily be done with a simple druid query API request, in my view, it should be easier to retrieve data, and even users who don't know how to write SQL queries/native queries should be able to get structured data easily. While on the other hand, stuff like Pivot are incredibly hard to code and in most languages (such as PHP) there are no good Pivot libraries, so by making it possible to easily get some sort of structured Pivot data directly from the backend which can easily be displayed on the frontend.