CouchDB has the handy ability to return warnings on mango queries. Most often it is a notification that the query could not find a suitable index, which of course is terrible for performance. However it is easy to miss this valuable information.

This patch adds a "Warning" property to FindResult and also the option to throw an exception if there a warning present on the FindResult.

This needs to be explicitly enabled by using ThrowOnQueryWarning() on the OptionsBuilder so it does not impact any existing code.

My personal intention for this feature it to enable it only in development so that if any of my tests cause a query that generates a warning then the test will fail and I can correct the problem (mostly likely by adding an appropriate index) before the issue makes it to production.

Could also be used in production if you are careful to catch the exception and do something with it, presumably log it somewhere that someone will actually see it.