The ‘Existing File Action’ configuration setting needs to address the situation where columns change.
Currently the following options exist, with instruction as follows at https://help.alteryx.com/20213/designer/microsoft-power-bi-output-tool:
There are two expectations when using this tool:
1. Reloads are built to completely replace the contents of a dataset, i.e. an Append is not being performed
2. Columns will change over time with continued development
There is therefore a need for an ‘Overwrite (update columns)’ option. However, when this Existing File Action is used it updates column names, but it does not delete the contents prior to upload. An append onto the existing data, but with new column names is therefore performed.
I acknowledge that the instructions do not say that existing rows are deleted.
This leaves the need to perform a workaround:
- Publish with ‘Overwrite (update columns)’
- Publish (immediately after) with ‘Overwrite (keep existing columns)’
If step 2 is not done data will be appended which would lead to duplication issues.
Either these Existing File Actions need to be renamed to be clearer as to their operation, or preferably an option that updates the columns and sets up new (non-appended) data is required.