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  2. SERVER-37821

Modify explain output for aggregations against mongos which target unsharded collections

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      On a sharded cluster

      1. Create unsharded collection
      2. Execute explain of an aggregate command with a single $out stage (defaulting to replace existing collection)
        Expected results:

      stages array is at the top level of the explain output

      Actual results

      stages array is nested within shards.<shard name>

      Sample output:

      {
  "splitPipeline" : null,
  "shards" : {
    "sh02" : {
      "host" : "localhost:27218",
      "stages" : [{
          "$cursor" : {
            "query" : { },
            "queryPlanner" : {
              "plannerVersion" : 1,
              "namespace" : "JavaDriverTest.com.mongodb.operation.AggregateToCollectionOperationSpecification",
              "indexFilterSet" : false,
              "parsedQuery" : { },
              "queryHash" : "8B3D4AB8",
              "winningPlan" : {
                "stage" : "FETCH",
                "inputStage" : {
                  "stage" : "IXSCAN",
                  "keyPattern" : {
                    "a" : 1
                  },
                  "indexName" : "a_1",
                  "isMultiKey" : false,
                  "multiKeyPaths" : {
                    "a" : []
                  },
                  "isUnique" : false,
                  "isSparse" : false,
                  "isPartial" : false,
                  "indexVersion" : 2,
                  "direction" : "forward",
                  "indexBounds" : {
                    "a" : ["[MinKey, MaxKey]"]
                  }
                }
              },
              "rejectedPlans" : []
            }
          }
        }, {
          "$out" : {
            "to" : "outputCollection",
            "db" : "JavaDriverTest",
            "mode" : "replaceCollection",
            "uniqueKey" : {
              "_id" : 1
            }
          }
        }]
    }
  },
  "ok" : 1.0,
   ...
}
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      On a sharded cluster Create unsharded collection Execute explain of an aggregate command with a single $out stage (defaulting to replace existing collection) Expected results: stages array is at the top level of the explain output Actual results stages array is nested within shards.<shard name> Sample output: { "splitPipeline" : null, "shards" : { "sh02" : { "host" : "localhost:27218", "stages" : [{ "$cursor" : { "query" : { }, "queryPlanner" : { "plannerVersion" : 1, "namespace" : "JavaDriverTest.com.mongodb.operation.AggregateToCollectionOperationSpecification", "indexFilterSet" : false, "parsedQuery" : { }, "queryHash" : "8B3D4AB8", "winningPlan" : { "stage" : "FETCH", "inputStage" : { "stage" : "IXSCAN", "keyPattern" : { "a" : 1 }, "indexName" : "a_1", "isMultiKey" : false, "multiKeyPaths" : { "a" : [] }, "isUnique" : false, "isSparse" : false, "isPartial" : false, "indexVersion" : 2, "direction" : "forward", "indexBounds" : { "a" : ["[MinKey, MaxKey]"] } } }, "rejectedPlans" : [] } } }, { "$out" : { "to" : "outputCollection", "db" : "JavaDriverTest", "mode" : "replaceCollection", "uniqueKey" : { "_id" : 1 } } }] } }, "ok" : 1.0, ... }

      On master with a sharded cluster but an unsharded collection, the stages array in the explain output of an aggregate command with hint and $out is nested in shards.<shard name>. This is different than 4.0 and earlier branches, in which the stages array is at the top level.

            Assignee:
            backlog-server-query Backlog - Query Team (Inactive)
            Reporter:
            jeff.yemin@mongodb.com Jeffrey Yemin
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              Created:
              Updated:
              Resolved: