Loading...

XML

Word

Printable

JSON

Backwards Compatibility:
Fully Compatible
Operating System:
ALL
Steps To Reproduce:

Hide

Run an _id query driven workload under 'perf top', and notice the IDHackRunner in the output. Re-run with $isolated, and note that the IDHackRunner goes away, and the QueryPlanner::plan function appears. Also, if you measure throughput, it is noticeably slower.

Show
Run an _id query driven workload under 'perf top', and notice the IDHackRunner in the output. Re-run with $isolated, and note that the IDHackRunner goes away, and the QueryPlanner::plan function appears. Also, if you measure throughput, it is noticeably slower.

Normally, a query like

{ _id : 1 }

will be routed to the "id hack" query runner. However, if the query is marked isolated with

{ _id : 1, $isolated : 1 }

, then the query execution is routed through QueryPlanner::plan, rather than redirected to the id hack runner, which greatly reduces performance.