DocumentSourceSkip and DocumentSourceMatch getNext() should release GetNextResult reference prior to subsequent underlying source getNext() call

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      The following will cause mongod to abort when this issue is present:

      1. Add invariant(false); at the start of the clonedStorage() method in pipeline/document.h 
        DocumentStorage& clonedStorage() {
    invariant(false);
    reset(storagePtr()->clone());
    return const_cast<DocumentStorage&>(*storagePtr());
}
      2. Run the following via mongo shell
        For DocumentSourceSkip: 
        db.test.insert({x: [1,2,3]})
db.test.aggregate([{$unwind: {path: "$x"}}, {$skip: 3}]);

        For DocumentSourceMatch:

        db.test.insert({x: [1,2,3]})
db.test.aggregate([{$unwind: {path: "$x"}},{$match: {x: 2}}]);
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      The following will cause mongod to abort when this issue is present: Add invariant(false); at the start of the clonedStorage() method in pipeline/document.h DocumentStorage& clonedStorage() { invariant(false); reset(storagePtr()->clone()); return const_cast<DocumentStorage&>(*storagePtr()); } Run the following via mongo shell For DocumentSourceSkip: db.test.insert({x: [1,2,3]}) db.test.aggregate([{$unwind: {path: "$x"}}, {$skip: 3}]); For DocumentSourceMatch: db.test.insert({x: [1,2,3]}) db.test.aggregate([{$unwind: {path: "$x"}},{$match: {x: 2}}]);
    • Query 2017-01-23
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      Maintaining the reference can lead to unnecessary cloning of data when the underlying source is destructive, as is the case for DocumentSourceUnwind. This leads to a 15% performance degradation in the mongoperf Unwind test.

            Assignee:
            James Wahlin
            Reporter:
            James Wahlin
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              Created:
              Updated:
              Resolved: