title: Mongodb query explain opterationTime meaning?
body: <p>We want to find the performance difference between the regular string comparison vs regex comparison. need the further understanding/explanation about the 'operationTime'.</p>
  
  <p>any one can explain the meaning of 'operationTime'?</p>
  
  <p>"operationTime" : Timestamp(1573768915, 16291) // it takes 16.291ms ?
  "operationTime" : Timestamp(1573768904, 15024) // it takes 15.024ms ?</p>
  
  <pre><code>db.getCollection("customer").find({accountId: "abcdefg"}).explain()
  { 
      "queryPlanner" : {
          "plannerVersion" : 1.0, 
          "namespace" : "myserver.customer", 
          "indexFilterSet" : false, 
          "parsedQuery" : {
              "accountId" : {
                  "$eq" : "abcdefg"
              }
          }, 
          "winningPlan" : {
              "stage" : "FETCH", 
              "inputStage" : {
                  "stage" : "IXSCAN", 
                  "indexName" : "accountId_partnerId", 
                  "isMultiKey" : false, 
                  "multiKeyPaths" : {
                  }, 
                  "isUnique" : true, 
                  "isSparse" : false, 
                  "isPartial" : true, 
                  "indexVersion" : 2.0, 
                  "direction" : "forward", 
                  "indexBounds" : {
                      "accountId" : [
                          "[\"abcdefg\", \"abcdefg\"]"
                      ], 
                      "partnerId" : [
                          "[MinKey, MaxKey]"
                      ]
                  }
              }
          }, 
      }, 
      "serverInfo" : {
          "host" : "mongodb-delta-02", 
          "port" : 27017.0, 
          "version" : "3.6.10", 
          "gitVersion" : "3e3ab85bfb98875af3bc6e74eeb945b0719f69c8"
      }, 
      "ok" : 1.0, 
      **"operationTime" : Timestamp(1573768915, 16291),**
      "$clusterTime" : {
          "clusterTime" : Timestamp(1573768915, 16291)
      }
  }
  
  db.getCollection("customer").find({accountId: /^abcdefg$/}).explain()
  { 
      "queryPlanner" : {
          "plannerVersion" : 1.0, 
          "namespace" : "myserver-customer", 
          "indexFilterSet" : false, 
          "parsedQuery" : {
              "accountId" : {
                  "$regex" : "^abcdefg$"
              }
          }, 
          "winningPlan" : {
              "stage" : "FETCH", 
              "inputStage" : {
                  "stage" : "IXSCAN", 
                  "filter" : {
                      "accountId" : {
                          "$regex" : "^abcdefg$"
                      }
                  },
                  "indexName" : "accountId_partnerId", 
                  "isMultiKey" : false, 
                  "isUnique" : true, 
                  "isSparse" : false, 
                  "isPartial" : true, 
                  "indexVersion" : 2.0, 
                  "direction" : "forward", 
                  "indexBounds" : {
                      "accountId" : [
                          "[\"abcdefg\", \"abcdef:\")", 
                          "[/^abcdefg$/, /^abcdefg$/]"
                      ], 
                      "partnerId" : [
                          "[MinKey, MaxKey]"
                      ]
                  }
              }
          },
      }, 
      "serverInfo" : {
          "host" : "mongodb-delta-02", 
          "port" : 27017.0, 
          "version" : "3.6.10", 
          "gitVersion" : "3e3ab85bfb98875af3bc6e74eeb945b0719f69c8"
      }, 
      "ok" : 1.0, 
      **"operationTime" : Timestamp(1573768904, 15024),**
      "$clusterTime" : {
          "clusterTime" : Timestamp(1573768904, 15024)
      }
  }```
  </code></pre>