Projections... You probably have a good idea of what that means already. Who remembers Plato's cave from high school? It's basically a group of people locked in a cave, staring at a blank wall all the time. All they see on that wall, are shadows of objects in the real world, projections if you will. Plato argued that, for these prisoners, these projections are as close as it gets to reality. However, people who reason about reality, and not just absorb it, free themselves from the cave. And can perceive reality as it really is. Not just its projections.
In a relational database, you typically have tables, containing your data and its relations. This is reality. If you want to see it from a particular angle, you can project your data into a view. A view might be a subset of columns of a table or a combination of some columns of one table, with some other columns of another table. These things exist in Vertica as well, and they are called projections. But it pushes this notion one step further. In Vertica, there are no tables, only projections. And a collection of projections can represent a table, or multiple tables.
So Vertica's idea of a projection is really Plato's cave turned inside-out. There is no reality. Only a collection of projections from which we can create that reality if we need to. Sounds familiar?
