Find COLLSCAN Queries in MongoDB
Lists queries doing collection scans in the profiler, with the examined-to-returned document ratio. The fastest way to find missing indexes.
db.system.profile.find(
{ planSummary: "COLLSCAN", ns: { $not: /system\.profile/ } },
{ ns: 1, op: 1, millis: 1, docsExamined: 1, nreturned: 1, command: 1, ts: 1 }
).sort({ millis: -1 }).limit(20);COLLSCAN operations scan every document in the collection; add supporting indexes to eliminate collection scans.
- This script is designed for read-only diagnostics; it does not alter schema or modify data directly.
- Prior to executing on production systems under high load, verify the target database version (Min. Version: 4.0).
- Exercise caution with mutating actions (e.g., terminating sessions or dropping indexes) referenced in the notes section.
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