That's right. It can be a bit hard to keep track of but the rules are quite simple. You start with all the columns from a `from`, then any `derive` just adds co

That's right. It can be a bit hard to keep track of but the rules are quite simple. You start with all the columns from a `from`, then any `derive` just adds columns. A `select` restricts the columns to those selected and a `group + aggregate` replaces the columns with those from the `group` + those from the `aggregate`. I once tabled a proposal whether each query should be forced to end with a `select` to make the final column list explicit. This could be generated by the compiler. It was felt that that wasn't necessary though and would also be somewhat arbitrary since you also need to know what columns are available at each previous step of the pipeline if you want to be able to make modifications. As the tooling improves, you could perhaps be shown the current list of columns as you hover over each line?