My records have a text field called "My Field". For some records these are the empty string and for others they have a value. I want to find all the ones for which "My Field" is not the empty string. In the KQL query bar of Discover I create a query that says "NOT My Field: (empty)". This returns all the records in the index. I get the same result if I temporarily disable this query clause. If instead I create a query of the form "My Field: some value" I do get records returned.
(The data is proprietary, so I can't post an example.)
I must not be understanding something about KQL. What am I doing wrong?