[Power BI] Document query debugging steps

[flanakin]

⚠️ Problem

When Power BI returns an unknown error, we need to step through the query in order to identify the problem. This process requires detailed knowledge about Power BI debugging that isn't obvious.

🛠️ Solution

Document the steps needed to debug Power BI query failures:

Identifying the failing query

1. Open the report
2. In the ribbon, select Transform data > Transform data
3. From the Power Query Editor window, find the query that is failing in the list of queries on the left
4. Jump to the troubleshooting section based on the folder (e.g., Storage, Resource Graph)

Troubleshooting storage query errors

1. From the Power Query Editor window, select the query that is failing in the list of queries on the left
2. In the Applied Steps section on the right, select the RawData step
3. If that step errors, skip down to "Troubleshooting ftk_Storage errors"
4. If that step works, select the next step below it, skipping anything that starts with a lowercase or underscore
5. Repeat step 4 until you find the first step that errors
6. Share the step name in any issue or support request to help troubleshoot further

Troubleshooting ftk_Storage errors

1. From the Power Query Editor window, right-click the ftk_Storage function on the left and select Duplicate
2. Right-click ftk_Storage (2) and select Advanced Editor
3. Remove the first line and replace the data = if datasetType... line with data = "focuscost",
4. Select Done at the bottom-right of the dialog
5. Select ftk_Storage (2) on the left and then click Refresh Preview in the ribbon at the top
6. In the Applied Steps on the right, select the last step
7. If that step errors, select the one before it (skip anything with an underscore or lowercase first character)
8. Repeat 7 until you find one that works
9. Share the step name in any issue or support request to help troubleshoot further

Troubleshooting Resource Graph query errors

TODO

Troubleshooting open data query errors

TODO

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