Subquery Support

Prometheus 2.7 introduces subqueries, allowing for range queries within a query – a previously unavailable feature. This eliminates the need to create recording rules for complex calculations like combining rates with different resolutions, saving time and reducing frustration. Subqueries function like an embedded `/query_range` API call, returning a range vector and enabling more dynamic and efficient PromQL expressions, though excessive use may impact performance and should be optimized with recording rules when possible.