In the absence of a fix for SERVER-15168 (now tracked as SERVER-8045), it would be useful to output a warning when a query is issued which uses $min but not $max, or vice-versa. This is because such usage can often have deleterious performance, and is contrary to the intended usage of $min/$max (see DOCS-4015).

Since the main in-server usage of $min/$max is for sharding, and always specifies both $min and $max, the warning would only occur with user queries that only specify either $min or $max (but not both).