Canvas Filter Dropdown Not Working

I have what I think should be a simple use case for Kibana canvas (Kibana 7.8.1), this is the query:

filters
| timelion query=".es(index=the-index*)"
| pointseries x="@timestamp" y="value"
| plot defaultStyle={seriesStyle points="0" lines="4" bars="0"}
| render

I've added a date filter (which works) and I'm trying to add a filter on the field in the index. I'm using Group By to get a distinct set of company names.

essql
query="SELECT CompanyName.raw FROM \"the-index*\"
WHERE CompanyName.raw IS NOT NULL
GROUP By CompanyName.raw"
| dropdownControl valueColumn="CompanyName.raw" filterColumn="CompanyName.raw"
| render

The CompanyName.raw field is a keyword field in the-index. Selecting options from the dropdown does not filter query at all.

Please help.