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  1. Core Server
  2. SERVER-22048

Index access stats should be recorded for $match & mapReduce

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      Reproduction case for aggregation:

      db.test.drop();
      		 
      db.test.save({a: 1});
      		 
      db.test.ensureIndex({a: 1});
      		 
      db.test.aggregate([{$match: {a: 1}}]);
      		 
      var statsArr = db.test.aggregate([{"$indexStats": {}}]).toArray();
      		 
      for (var idx in statsArr) {
      		 
          var doc = statsArr[idx];
      		 
          if (doc.name === "a_1") {
      		 
              assert(doc.accesses.ops == 1);
      		 
          }
      		 
      }

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      Reproduction case for aggregation: db.test.drop(); db.test.save({a: 1}); db.test.ensureIndex({a: 1}); db.test.aggregate([{$match: {a: 1}}]); var statsArr = db.test.aggregate([{"$indexStats": {}}]).toArray(); for (var idx in statsArr) { var doc = statsArr[idx]; if (doc.name === "a_1") { assert(doc.accesses.ops == 1); } }
    • QuInt E (01/11/16), Query F (02/01/16)

    Description

      Index access stats, retrievable via the $indexStats aggregation source, track the number of times a given index was used to satisfy a user operation.

      $match as a document source in aggregation can make use of indexes to retrieve documents but is currently not recording usage statistics. Support should be added for $match as exclusion could lead to the wrong conclusion as to whether an index is being used.

      Also missing is a hook to record index access when a mapReduce uses an index to satisfy a "query" argument. This issue will add support for both aggregation and mapReduce.

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          is duplicated by

          Improvement - An improvement or enhancement to an existing feature or task. SERVER-22183 Aggregation $match doesn`t increase counter in the $indexStats

          • Critical - P2 - Crashes, loss of data, severe memory leak.
          • Closed
          related to

          Task - A task that needs to be done. DOCS-6973 Add note about $indexStats limitations in <3.2.2

          • Major - P3 - Major loss of function.
          • Closed

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              james.wahlin@mongodb.com James Wahlin
              james.wahlin@mongodb.com James Wahlin
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                Updated:
                Resolved: