About Grafana DataFrames and transformations
While it is easy to imagine that Grafana simply takes the results of one or more data source queries, and somehow feeds them to the panel visualization of your choice, the reality is a bit more complex than that.
Every query result from the Query tab is managed separately as an independent data series by Grafana. That way, you have full control over each series and how it may be displayed in a panel visualization.
Next, each of those datasets is packaged into a single object Grafana referred to as a DataFrame. If you are at all familiar with Excel or Google spreadsheets from the financial world, or pandas or Spark from the data science world, you already have experience with the concept.
A Grafana DataFrame is, like similar objects, a rows and columns (technically an array of arrays) data structure, with each row a combination of one or more columnar fields. Because the DataFrame is a consistent data structure, it can easily be...