If a CSV contains boolean values in all caps (TRUE/FALSE), Elasticsearch will index "FALSE" as a truthy value. This is because the sever side CSV parser does not recognize FALSE as a boolean value, and sends it as a JSON string. To make matters worse, the client side parser DOES detect it as a boolean value, so the user will think everything is working fine until they realize every FALSE value has been indexed as true.

I can think of a couple ways to fix this:

• Turn off auto type detection on the server side and use the client side selections. We'd just have to normalize things like geo_point to their JSON values. This is probably the correct solution.
• Somehow normalize capitalization of boolean values.