Performance Notes

Like any profiler, the Profile API introduce a non-negligible overhead to query execution. The act of instrumenting low-level method calls such as advance and next_doc can be fairly expensive, since these methods are called in tight loops. Therefore, profiling should not be enabled in production settings by default, and should not be compared against non-profiled query times. Profiling is just a diagnostic tool.

There are also cases where special Lucene optimizations are disabled, since they are not amenable to profiling. This could cause some queries to report larger relative times than their non-profiled counterparts, but in general should not have a drastic effect compared to other components in the profiled query.