The column accessor framework consists of a number of layers that combine to enable Drill to control the size of each record batch, which in turn allows Drill to implement effective memory management and admission control.
The material here starts with concepts, then provides a tour of the various components. Each component is heavily commented, so after reading this material, you should be able to get the details from the code itself.
The material here is a slightly-revised version of the material that orginally appeared in the paul-rogers/drill Wiki.
[[Result Set Loader|BH Result Set Loader]]
[[Operator Framework|BH Operator Framework]]
[[Projection Framework|BH Projection Framework]]
[[Scan Framework|BH Scan Framework]]
[[Easy Format Plugin|BH Easy Format Plugin]]
[[CSV (Compliant Text) Reader|BH Compliant Text Reader]]
[[JSON Reader|BH JSON Reader]]
The code for the mechanisms described here appears in multiple Drill modules, along with its unit tests. It is described here in one place to provide a complete overview.
It can be hard to understand complex code. To make doing so easier, we offer three paths:
The code itself has many comments and explanations; it is the best resource to understand the detailed algorithms and approaches.