Lesson 2.3.7
See the whole workflow as a flowchart
What this costs
Free. Reading the workflow costs nothing, which is the point of reading it before you run it.
Before you start
A project with a few columns that feed each other.
This whole course argues that the table is a workflow rather than a spreadsheet. The flowchart is that argument made visible: every column, and the columns it waits on, drawn as a graph. It is the fastest way to see why a run cost what it cost, and the fastest way to spot the dependency you did not mean to create.
What the chart is actually showing you
Each box is a column. Each arrow is a dependency: this column reads that one, so it cannot run until that one has finished. A column with three arrows into it runs last and fails if any of the three came back empty. That is the whole model, and once you can see it the credit bill stops being a surprise.
- A long chain means a slow run, because each step waits on the one before it.
- A column with no arrows into it can run immediately, and usually should run first.
- A wide fan out from one column means that column is load bearing. If it is wrong, everything downstream is wrong.
- Anything sitting on its own is either a free qualifier or a column nobody wired up.
The two shapes worth recognising
| Shape | What it means | What to do |
|---|---|---|
| A filter sitting late in the chain | You are paying to enrich rows you are about to cut | Move the filter in front of the paid columns |
| One column feeding many | A single point of failure for the whole table | Check its fill rate before running anything downstream |
| A chain five deep | Every run waits on five sequential steps | Look for steps that could run in parallel instead |
| An orphan column | Either a free qualifier, or dead weight nobody reads | Delete it or wire it in |
A column never runs
- What you see
- It stays empty while everything else fills
- The fix
- It is waiting on a dependency that returned nothing. Follow the arrows back to the first empty box.
The run costs more than you estimated
- What you see
- Credits spent well above the preview
- The fix
- A paid column is sitting upstream of your filter, so it ran on every row rather than the qualified ones.
Check yourself
0 of 3 answered1.What does an arrow between two columns mean?
2.Your run cost far more than the preview estimated. What shape explains it?
3.One column fans out to many others. Why does that matter?
Try it yourself
Open the flowchart on a project you have already run, and find the one column everything else depends on.
- You have done it when
- You can name the load bearing column, and say what would break downstream if it came back empty.
- Credit budget
- Free.