Dashboard: Slow loading of data unless I change a variable value

### What happened? I have a dashboard with a "data source" variable. I also has a variable called "schema" which queries the "data source" to find all available schemas for that data source. If I open the dashboard, and the variables have their default values, loading data takes a lot of time (+10 seconds). However if I change "data source" from "data source A" (default) to "data source B", and then immediately back to "data source A" again, the data is loaded instantely. Is this a bug? What could be wrong here? The data source is a databricks SQL warehouse. I use the same data across multiple panels, with different transformations, so I first load the "base data" in two table panels. These two table panels are in a row which is collapsed. I then create panels that query the table panels containing base data (using the "-- Grafana --" data source). Usually, it's only one of the table panels that takes a while to load. I have tried to reorder the table panels to see if it makes a difference. ### What did you expect to happen? I expceted the data to be loaded in the same amount of time, regardless of whether I change a variable from it's default value or not. ### Did this work before? Not sure, this is the first time I experience this issue. ### How do we reproduce it? Not sure if this will reproduce the problem, but this is my setup: 1. Create a variable selecting a data source. 2. Create another variable querying the selected data source. 3. Create a table panel to read data from the selected data source. Use the second variable in this query in some way. 4. Create a second panel that uses data from the table panel and applies some kind of transformation. 5. Do (3) and (4) for a second query. 6. Load the dashboard without changing the variable values. Observe slow loading. 7. Load the dashboard again, but now change a variable from A -> B -> A (without waiting for the queries to complete before changing). Observe the data being loaded instantely. ### Is the bug ins…