Does the Azure Data Explorer optimize the entire query if your base table access is in a function?

When you call stored function in Kusto - it would be the same as if you would use the functions' "bodies" inline. This means that the function call will be optimized the same way as if the whole query is inlined. Kusto.Explorer (Windows Desktop app) - https://aka.ms/ke can show you the execution tree of the query. Write your query down in the query editor, and use ribbon Tools->Query Analyzer to run it and show you the optimized execution tree of the query. If you have specific question about why certain optimization is not kicking in - feel free to submit a separate question.