RecordProjection

A query's projection over a whole record, for a backend that reads the record and projects it itself: what the includes keep (the whole record when there are none), less what the excludes remove. Each path is the field's segments in the record as the backend built it.

An include keeps the subtree at its path. Through an array it keeps that subtree in every element, at the element's position: an object element by its own fields, an array element (an array of arrays) by its own elements, so the nesting is kept. A scalar element holds nothing to keep: it becomes an empty object where a later element keeps something, so the kept elements stay at their positions, and is left out after the last one ([1, {"a": 2}, 3] projected to a is [{}, {"a": 2}]; an array of scalars alone is []). An exclude removes the subtree at its path in every element on the way and leaves scalar elements as they are.