SERVER-43877 Remove raw projection BSON from projection stages

13 files changed, 130 insertions, 112 deletions

diff --git a/src/mongo/db/commands/find_and_modify.cpp b/src/mongo/db/commands/find_and_modify.cpp
index fbe9235c19e..7a0c7f038e1 100644
--- a/src/mongo/db/commands/find_and_modify.cpp
+++ b/src/mongo/db/commands/find_and_modify.cpp
@@ -267,8 +267,8 @@ public:
             css->checkShardVersionOrThrow(opCtx, autoColl.getCollection());
 
             Collection* const collection = autoColl.getCollection();
-            const auto exec =
-                uassertStatusOK(getExecutorDelete(opCtx, opDebug, collection, &parsedDelete));
+            const auto exec = uassertStatusOK(
+                getExecutorDelete(opCtx, opDebug, collection, &parsedDelete, verbosity));
 
             auto bodyBuilder = result->getBodyBuilder();
             Explain::explainStages(exec.get(), collection, verbosity, BSONObj(), &bodyBuilder);
@@ -292,8 +292,8 @@ public:
             css->checkShardVersionOrThrow(opCtx, autoColl.getCollection());
 
             Collection* const collection = autoColl.getCollection();
-            const auto exec =
-                uassertStatusOK(getExecutorUpdate(opCtx, opDebug, collection, &parsedUpdate));
+            const auto exec = uassertStatusOK(
+                getExecutorUpdate(opCtx, opDebug, collection, &parsedUpdate, verbosity));
 
             auto bodyBuilder = result->getBodyBuilder();
             Explain::explainStages(exec.get(), collection, verbosity, BSONObj(), &bodyBuilder);
@@ -381,8 +381,8 @@ public:
                 Collection* const collection = autoColl.getCollection();
                 checkIfTransactionOnCappedColl(collection, inTransaction);
 
-                const auto exec =
-                    uassertStatusOK(getExecutorDelete(opCtx, opDebug, collection, &parsedDelete));
+                const auto exec = uassertStatusOK(getExecutorDelete(
+                    opCtx, opDebug, collection, &parsedDelete, boost::none /* verbosity */));
 
                 {
                     stdx::lock_guard<Client> lk(*opCtx->getClient());
@@ -487,8 +487,8 @@ public:
 
                 checkIfTransactionOnCappedColl(collection, inTransaction);
 
-                const auto exec =
-                    uassertStatusOK(getExecutorUpdate(opCtx, opDebug, collection, &parsedUpdate));
+                const auto exec = uassertStatusOK(getExecutorUpdate(
+                    opCtx, opDebug, collection, &parsedUpdate, boost::none /* verbosity */));
 
                 {
                     stdx::lock_guard<Client> lk(*opCtx->getClient());
diff --git a/src/mongo/db/commands/find_cmd.cpp b/src/mongo/db/commands/find_cmd.cpp
index 82f9dd07c96..56e65aad432 100644
--- a/src/mongo/db/commands/find_cmd.cpp
+++ b/src/mongo/db/commands/find_cmd.cpp
@@ -76,8 +76,10 @@ std::unique_ptr<QueryRequest> parseCmdObjectToQueryRequest(OperationContext* opC
     return qr;
 }
 
-boost::intrusive_ptr<ExpressionContext> makeExpressionContext(OperationContext* opCtx,
-                                                              const QueryRequest& queryRequest) {
+boost::intrusive_ptr<ExpressionContext> makeExpressionContext(
+    OperationContext* opCtx,
+    const QueryRequest& queryRequest,
+    boost::optional<ExplainOptions::Verbosity> verbosity) {
     std::unique_ptr<CollatorInterface> collator;
     if (!queryRequest.getCollation().isEmpty()) {
         collator = uassertStatusOK(CollatorFactoryInterface::get(opCtx->getServiceContext())
@@ -100,9 +102,9 @@ boost::intrusive_ptr<ExpressionContext> makeExpressionContext(OperationContext*
     // sense to start initializing these fields for find operations as well.
     auto expCtx =
         make_intrusive<ExpressionContext>(opCtx,
-                                          boost::none,  // explain
-                                          false,        // fromMongos
-                                          false,        // needsMerge
+                                          verbosity,
+                                          false,  // fromMongos
+                                          false,  // needsMerge
                                           queryRequest.allowDiskUse(),
                                           false,  // bypassDocumentValidation
                                           queryRequest.nss(),
@@ -227,7 +229,7 @@ public:
 
             // Finish the parsing step by using the QueryRequest to create a CanonicalQuery.
             const ExtensionsCallbackReal extensionsCallback(opCtx, &nss);
-            auto expCtx = makeExpressionContext(opCtx, *qr);
+            auto expCtx = makeExpressionContext(opCtx, *qr, verbosity);
             auto cq = uassertStatusOK(
                 CanonicalQuery::canonicalize(opCtx,
                                              std::move(qr),
@@ -425,7 +427,7 @@ public:
 
             // Finish the parsing step by using the QueryRequest to create a CanonicalQuery.
             const ExtensionsCallbackReal extensionsCallback(opCtx, &nss);
-            auto expCtx = makeExpressionContext(opCtx, *qr);
+            auto expCtx = makeExpressionContext(opCtx, *qr, boost::none /* verbosity */);
             auto cq = uassertStatusOK(
                 CanonicalQuery::canonicalize(opCtx,
                                              std::move(qr),
diff --git a/src/mongo/db/commands/write_commands/write_commands.cpp b/src/mongo/db/commands/write_commands/write_commands.cpp
index 8d7339d1d80..4c9671b9e34 100644
--- a/src/mongo/db/commands/write_commands/write_commands.cpp
+++ b/src/mongo/db/commands/write_commands/write_commands.cpp
@@ -377,8 +377,11 @@ private:
             // info is more accurate.
             AutoGetCollection collection(opCtx, _batch.getNamespace(), MODE_IX);
 
-            auto exec = uassertStatusOK(getExecutorUpdate(
-                opCtx, &CurOp::get(opCtx)->debug(), collection.getCollection(), &parsedUpdate));
+            auto exec = uassertStatusOK(getExecutorUpdate(opCtx,
+                                                          &CurOp::get(opCtx)->debug(),
+                                                          collection.getCollection(),
+                                                          &parsedUpdate,
+                                                          verbosity));
             auto bodyBuilder = result->getBodyBuilder();
             Explain::explainStages(
                 exec.get(), collection.getCollection(), verbosity, BSONObj(), &bodyBuilder);
@@ -451,8 +454,11 @@ private:
             AutoGetCollection collection(opCtx, _batch.getNamespace(), MODE_IX);
 
             // Explain the plan tree.
-            auto exec = uassertStatusOK(getExecutorDelete(
-                opCtx, &CurOp::get(opCtx)->debug(), collection.getCollection(), &parsedDelete));
+            auto exec = uassertStatusOK(getExecutorDelete(opCtx,
+                                                          &CurOp::get(opCtx)->debug(),
+                                                          collection.getCollection(),
+                                                          &parsedDelete,
+                                                          verbosity));
             auto bodyBuilder = result->getBodyBuilder();
             Explain::explainStages(
                 exec.get(), collection.getCollection(), verbosity, BSONObj(), &bodyBuilder);
diff --git a/src/mongo/db/exec/projection.cpp b/src/mongo/db/exec/projection.cpp
index d824df21a6c..514b90a78a4 100644
--- a/src/mongo/db/exec/projection.cpp
+++ b/src/mongo/db/exec/projection.cpp
@@ -45,9 +45,6 @@
 #include "mongo/util/str.h"
 
 namespace mongo {
-
-static const char* kIdField = "_id";
-
 namespace {
 
 void transitionMemberToOwnedObj(Document&& doc, WorkingSetMember* member) {
@@ -115,36 +112,14 @@ auto rehydrateIndexKey(const BSONObj& keyPattern, const BSONObj& dehydratedKey)
 }
 }  // namespace
 
-ProjectionStage::ProjectionStage(OperationContext* opCtx,
+ProjectionStage::ProjectionStage(boost::intrusive_ptr<ExpressionContext> expCtx,
                                  const BSONObj& projObj,
                                  WorkingSet* ws,
                                  std::unique_ptr<PlanStage> child,
                                  const char* stageType)
-    : PlanStage(opCtx, std::move(child), stageType), _projObj(projObj), _ws(*ws) {}
-
-// static
-void ProjectionStage::getSimpleInclusionFields(const BSONObj& projObj, FieldSet* includedFields) {
-    // The _id is included by default.
-    bool includeId = true;
-
-    // Figure out what fields are in the projection. We could eventually do this using the
-    // Projection AST.
-    BSONObjIterator projObjIt(projObj);
-    while (projObjIt.more()) {
-        BSONElement elt = projObjIt.next();
-        // Must deal with the _id case separately as there is an implicit _id: 1 in the
-        // projection.
-        if ((elt.fieldNameStringData() == kIdField) && !elt.trueValue()) {
-            includeId = false;
-            continue;
-        }
-        (*includedFields)[elt.fieldNameStringData()] = true;
-    }
-
-    if (includeId) {
-        (*includedFields)[kIdField] = true;
-    }
-}
+    : PlanStage{expCtx->opCtx, std::move(child), stageType},
+      _projObj{expCtx->explain ? boost::make_optional(projObj.getOwned()) : boost::none},
+      _ws{*ws} {}
 
 bool ProjectionStage::isEOF() {
     return child()->isEOF();
@@ -184,7 +159,7 @@ std::unique_ptr<PlanStageStats> ProjectionStage::getStats() {
     auto ret = std::make_unique<PlanStageStats>(_commonStats, stageType());
 
     auto projStats = std::make_unique<ProjectionStats>(_specificStats);
-    projStats->projObj = _projObj;
+    projStats->projObj = _projObj.value_or(BSONObj{});
     ret->specific = std::move(projStats);
 
     ret->children.emplace_back(child()->getStats());
@@ -196,7 +171,7 @@ ProjectionStageDefault::ProjectionStageDefault(boost::intrusive_ptr<ExpressionCo
                                                const projection_ast::Projection* projection,
                                                WorkingSet* ws,
                                                std::unique_ptr<PlanStage> child)
-    : ProjectionStage{expCtx->opCtx, projObj, ws, std::move(child), "PROJECTION_DEFAULT"},
+    : ProjectionStage{expCtx, projObj, ws, std::move(child), "PROJECTION_DEFAULT"},
       _wantRecordId{projection->metadataDeps()[DocumentMetadataFields::kRecordId]},
       _projectType{projection->type()},
       _executor{projection_executor::buildProjectionExecutor(expCtx, projection, {})} {}
@@ -241,16 +216,15 @@ Status ProjectionStageDefault::transform(WorkingSetMember* member) const {
     return Status::OK();
 }
 
-ProjectionStageCovered::ProjectionStageCovered(OperationContext* opCtx,
+ProjectionStageCovered::ProjectionStageCovered(boost::intrusive_ptr<ExpressionContext> expCtx,
                                                const BSONObj& projObj,
+                                               const projection_ast::Projection* projection,
                                                WorkingSet* ws,
                                                std::unique_ptr<PlanStage> child,
                                                const BSONObj& coveredKeyObj)
-    : ProjectionStage(opCtx, projObj, ws, std::move(child), "PROJECTION_COVERED"),
-      _coveredKeyObj(coveredKeyObj) {
-    invariant(projObjHasOwnedData());
-    // Figure out what fields are in the projection.
-    getSimpleInclusionFields(_projObj, &_includedFields);
+    : ProjectionStage{expCtx, projObj, ws, std::move(child), "PROJECTION_COVERED"},
+      _coveredKeyObj{coveredKeyObj} {
+    invariant(projection->isSimple());
 
     // If we're pulling data out of one index we can pre-compute the indices of the fields
     // in the key that we pull data from and avoid looking up the field name each time.
@@ -258,6 +232,8 @@ ProjectionStageCovered::ProjectionStageCovered(OperationContext* opCtx,
     // Sanity-check.
     invariant(_coveredKeyObj.isOwned());
 
+    _includedFields = {projection->getRequiredFields().begin(),
+                       projection->getRequiredFields().end()};
     BSONObjIterator kpIt(_coveredKeyObj);
     while (kpIt.more()) {
         BSONElement elt = kpIt.next();
@@ -269,7 +245,7 @@ ProjectionStageCovered::ProjectionStageCovered(OperationContext* opCtx,
             _includeKey.push_back(false);
         } else {
             // If we are including this key field store its field name.
-            _keyFieldNames.push_back(fieldIt->first);
+            _keyFieldNames.push_back(*fieldIt);
             _includeKey.push_back(true);
         }
     }
@@ -297,14 +273,15 @@ Status ProjectionStageCovered::transform(WorkingSetMember* member) const {
     return Status::OK();
 }
 
-ProjectionStageSimple::ProjectionStageSimple(OperationContext* opCtx,
+ProjectionStageSimple::ProjectionStageSimple(boost::intrusive_ptr<ExpressionContext> expCtx,
                                              const BSONObj& projObj,
+                                             const projection_ast::Projection* projection,
                                              WorkingSet* ws,
                                              std::unique_ptr<PlanStage> child)
-    : ProjectionStage(opCtx, projObj, ws, std::move(child), "PROJECTION_SIMPLE") {
-    invariant(projObjHasOwnedData());
-    // Figure out what fields are in the projection.
-    getSimpleInclusionFields(_projObj, &_includedFields);
+    : ProjectionStage{expCtx, projObj, ws, std::move(child), "PROJECTION_SIMPLE"} {
+    invariant(projection->isSimple());
+    _includedFields = {projection->getRequiredFields().begin(),
+                       projection->getRequiredFields().end()};
 }
 
 Status ProjectionStageSimple::transform(WorkingSetMember* member) const {
@@ -317,8 +294,8 @@ Status ProjectionStageSimple::transform(WorkingSetMember* member) const {
     // Look at every field in the source document and see if we're including it.
     auto objToProject = member->doc.value().toBson();
     for (auto&& elt : objToProject) {
-        auto fieldIt = _includedFields.find(elt.fieldNameStringData());
-        if (_includedFields.end() != fieldIt) {
+        if (auto fieldIt = _includedFields.find(elt.fieldNameStringData());
+            _includedFields.end() != fieldIt) {
             bob.append(elt);
         }
     }
diff --git a/src/mongo/db/exec/projection.h b/src/mongo/db/exec/projection.h
index 5b368750cad..0866dbdd150 100644
--- a/src/mongo/db/exec/projection.h
+++ b/src/mongo/db/exec/projection.h
@@ -43,7 +43,7 @@ namespace mongo {
  */
 class ProjectionStage : public PlanStage {
 protected:
-    ProjectionStage(OperationContext* opCtx,
+    ProjectionStage(boost::intrusive_ptr<ExpressionContext> expCtx,
                     const BSONObj& projObj,
                     WorkingSet* ws,
                     std::unique_ptr<PlanStage> child,
@@ -60,22 +60,11 @@ public:
     }
 
 protected:
-    using FieldSet = StringMap<bool>;  // Value is unused.
+    using FieldSet = StringSet;
 
-    /**
-     * Given the projection spec for a simple inclusion projection,
-     * 'projObj', populates 'includedFields' with the set of field
-     * names to be included.
-     */
-    static void getSimpleInclusionFields(const BSONObj& projObj, FieldSet* includedFields);
-
-    bool projObjHasOwnedData() {
-        return _projObj.isOwned() && !_projObj.isEmpty();
-    }
-
-    // The projection object used by all projection implementations. We lack a ProjectionExpression
-    // or similar so we use a BSONObj.
-    BSONObj _projObj;
+    // The raw BSON projection used to populate projection stats. Optional, since it is required
+    // only in explain mode.
+    boost::optional<BSONObj> _projObj;
 
 private:
     /**
@@ -128,8 +117,9 @@ public:
     /**
      * ProjectionNodeCovered should obtain a fast-path object through this constructor.
      */
-    ProjectionStageCovered(OperationContext* opCtx,
+    ProjectionStageCovered(boost::intrusive_ptr<ExpressionContext> expCtx,
                            const BSONObj& projObj,
+                           const projection_ast::Projection* projection,
                            WorkingSet* ws,
                            std::unique_ptr<PlanStage> child,
                            const BSONObj& coveredKeyObj);
@@ -141,7 +131,7 @@ public:
 private:
     Status transform(WorkingSetMember* member) const final;
 
-    // Has the field names present in the simple projection.
+    // Field names present in the simple projection.
     FieldSet _includedFields;
 
     // This is the key pattern we're extracting covered data from. It is maintained here since
@@ -166,8 +156,9 @@ public:
     /**
      * ProjectionNodeSimple should obtain a fast-path object through this constructor.
      */
-    ProjectionStageSimple(OperationContext* opCtx,
+    ProjectionStageSimple(boost::intrusive_ptr<ExpressionContext> expCtx,
                           const BSONObj& projObj,
+                          const projection_ast::Projection* projection,
                           WorkingSet* ws,
                           std::unique_ptr<PlanStage> child);
 
diff --git a/src/mongo/db/ops/delete.cpp b/src/mongo/db/ops/delete.cpp
index 3a95b360a47..85b06c4e7db 100644
--- a/src/mongo/db/ops/delete.cpp
+++ b/src/mongo/db/ops/delete.cpp
@@ -56,8 +56,11 @@ long long deleteObjects(OperationContext* opCtx,
     ParsedDelete parsedDelete(opCtx, &request);
     uassertStatusOK(parsedDelete.parseRequest());
 
-    auto exec = uassertStatusOK(
-        getExecutorDelete(opCtx, &CurOp::get(opCtx)->debug(), collection, &parsedDelete));
+    auto exec = uassertStatusOK(getExecutorDelete(opCtx,
+                                                  &CurOp::get(opCtx)->debug(),
+                                                  collection,
+                                                  &parsedDelete,
+                                                  boost::none /* verbosity */));
 
     uassertStatusOK(exec->executePlan());
 
diff --git a/src/mongo/db/ops/update.cpp b/src/mongo/db/ops/update.cpp
index f6e0fcd3eaa..6f12b861cc4 100644
--- a/src/mongo/db/ops/update.cpp
+++ b/src/mongo/db/ops/update.cpp
@@ -97,7 +97,8 @@ UpdateResult update(OperationContext* opCtx, Database* db, const UpdateRequest&
     uassertStatusOK(parsedUpdate.parseRequest());
 
     OpDebug* const nullOpDebug = nullptr;
-    auto exec = uassertStatusOK(getExecutorUpdate(opCtx, nullOpDebug, collection, &parsedUpdate));
+    auto exec = uassertStatusOK(getExecutorUpdate(
+        opCtx, nullOpDebug, collection, &parsedUpdate, boost::none /* verbosity */));
 
     uassertStatusOK(exec->executePlan());
 
diff --git a/src/mongo/db/ops/write_ops_exec.cpp b/src/mongo/db/ops/write_ops_exec.cpp
index d640bbf8113..3f22f0fd379 100644
--- a/src/mongo/db/ops/write_ops_exec.cpp
+++ b/src/mongo/db/ops/write_ops_exec.cpp
@@ -636,8 +636,11 @@ static SingleWriteResult performSingleUpdateOp(OperationContext* opCtx,
 
     assertCanWrite_inlock(opCtx, ns, collection->getCollection());
 
-    auto exec = uassertStatusOK(
-        getExecutorUpdate(opCtx, &curOp.debug(), collection->getCollection(), &parsedUpdate));
+    auto exec = uassertStatusOK(getExecutorUpdate(opCtx,
+                                                  &curOp.debug(),
+                                                  collection->getCollection(),
+                                                  &parsedUpdate,
+                                                  boost::none /* verbosity */));
 
     {
         stdx::lock_guard<Client> lk(*opCtx->getClient());
@@ -865,8 +868,11 @@ static SingleWriteResult performSingleDeleteOp(OperationContext* opCtx,
     CurOpFailpointHelpers::waitWhileFailPointEnabled(
         &hangWithLockDuringBatchRemove, opCtx, "hangWithLockDuringBatchRemove");
 
-    auto exec = uassertStatusOK(
-        getExecutorDelete(opCtx, &curOp.debug(), collection.getCollection(), &parsedDelete));
+    auto exec = uassertStatusOK(getExecutorDelete(opCtx,
+                                                  &curOp.debug(),
+                                                  collection.getCollection(),
+                                                  &parsedDelete,
+                                                  boost::none /* verbosity */));
 
     {
         stdx::lock_guard<Client> lk(*opCtx->getClient());
diff --git a/src/mongo/db/query/find.cpp b/src/mongo/db/query/find.cpp
index 12b5f4073ee..0d903bd3086 100644
--- a/src/mongo/db/query/find.cpp
+++ b/src/mongo/db/query/find.cpp
@@ -591,7 +591,8 @@ std::string runQuery(OperationContext* opCtx,
     beginQueryOp(opCtx, nss, upconvertedQuery, q.ntoreturn, q.ntoskip);
 
     // Parse the qm into a CanonicalQuery.
-    const boost::intrusive_ptr<ExpressionContext> expCtx;
+    const boost::intrusive_ptr<ExpressionContext> expCtx =
+        make_intrusive<ExpressionContext>(opCtx, nullptr /* collator */);
     auto cq = uassertStatusOKWithContext(
         CanonicalQuery::canonicalize(opCtx,
                                      q,
@@ -607,10 +608,9 @@ std::string runQuery(OperationContext* opCtx,
     // Parse, canonicalize, plan, transcribe, and get a plan executor.
     AutoGetCollectionForReadCommand ctx(opCtx, nss, AutoGetCollection::ViewMode::kViewsForbidden);
     Collection* const collection = ctx.getCollection();
+    const QueryRequest& qr = cq->getQueryRequest();
 
     {
-        const QueryRequest& qr = cq->getQueryRequest();
-
         // Allow the query to run on secondaries if the read preference permits it. If no read
         // preference was specified, allow the query to run iff slaveOk has been set.
         const bool slaveOK = qr.hasReadPref()
@@ -622,10 +622,10 @@ std::string runQuery(OperationContext* opCtx,
     }
 
     // Get the execution plan for the query.
+    constexpr auto verbosity = ExplainOptions::Verbosity::kExecAllPlans;
+    expCtx->explain = qr.isExplain() ? boost::make_optional(verbosity) : boost::none;
     auto exec = uassertStatusOK(getExecutorLegacyFind(opCtx, collection, std::move(cq)));
 
-    const QueryRequest& qr = exec->getCanonicalQuery()->getQueryRequest();
-
     // If it's actually an explain, do the explain and return rather than falling through
     // to the normal query execution loop.
     if (qr.isExplain()) {
@@ -633,11 +633,7 @@ std::string runQuery(OperationContext* opCtx,
         bb.skip(sizeof(QueryResult::Value));
 
         BSONObjBuilder explainBob;
-        Explain::explainStages(exec.get(),
-                               collection,
-                               ExplainOptions::Verbosity::kExecAllPlans,
-                               BSONObj(),
-                               &explainBob);
+        Explain::explainStages(exec.get(), collection, verbosity, BSONObj(), &explainBob);
 
         // Add the resulting object to the return buffer.
         BSONObj explainObj = explainBob.obj();
diff --git a/src/mongo/db/query/get_executor.cpp b/src/mongo/db/query/get_executor.cpp
index 8f0623def21..b236de9e8ea 100644
--- a/src/mongo/db/query/get_executor.cpp
+++ b/src/mongo/db/query/get_executor.cpp
@@ -427,7 +427,11 @@ StatusWith<PrepareExecutionResult> prepareExecution(OperationContext* opCtx,
                     std::move(root));
             } else {
                 root = std::make_unique<ProjectionStageSimple>(
-                    opCtx, canonicalQuery->getQueryRequest().getProj(), ws, std::move(root));
+                    canonicalQuery->getExpCtx(),
+                    canonicalQuery->getQueryRequest().getProj(),
+                    canonicalQuery->getProj(),
+                    ws,
+                    std::move(root));
             }
         }
 
@@ -686,7 +690,11 @@ StatusWith<unique_ptr<PlanStage>> applyProjection(OperationContext* opCtx,
 //
 
 StatusWith<unique_ptr<PlanExecutor, PlanExecutor::Deleter>> getExecutorDelete(
-    OperationContext* opCtx, OpDebug* opDebug, Collection* collection, ParsedDelete* parsedDelete) {
+    OperationContext* opCtx,
+    OpDebug* opDebug,
+    Collection* collection,
+    ParsedDelete* parsedDelete,
+    boost::optional<ExplainOptions::Verbosity> verbosity) {
     const DeleteRequest* request = parsedDelete->getRequest();
 
     const NamespaceString& nss(request->getNamespaceString());
@@ -772,6 +780,9 @@ StatusWith<unique_ptr<PlanExecutor, PlanExecutor::Deleter>> getExecutorDelete(
     // This is the regular path for when we have a CanonicalQuery.
     unique_ptr<CanonicalQuery> cq(parsedDelete->releaseParsedQuery());
 
+    // Transfer the explain verbosity level into the expression context.
+    cq->getExpCtx()->explain = verbosity;
+
     const size_t defaultPlannerOptions = 0;
     StatusWith<PrepareExecutionResult> executionResult =
         prepareExecution(opCtx, collection, ws.get(), std::move(cq), defaultPlannerOptions);
@@ -816,7 +827,11 @@ StatusWith<unique_ptr<PlanExecutor, PlanExecutor::Deleter>> getExecutorDelete(
 //
 
 StatusWith<unique_ptr<PlanExecutor, PlanExecutor::Deleter>> getExecutorUpdate(
-    OperationContext* opCtx, OpDebug* opDebug, Collection* collection, ParsedUpdate* parsedUpdate) {
+    OperationContext* opCtx,
+    OpDebug* opDebug,
+    Collection* collection,
+    ParsedUpdate* parsedUpdate,
+    boost::optional<ExplainOptions::Verbosity> verbosity) {
     const UpdateRequest* request = parsedUpdate->getRequest();
     UpdateDriver* driver = parsedUpdate->getDriver();
 
@@ -913,6 +928,9 @@ StatusWith<unique_ptr<PlanExecutor, PlanExecutor::Deleter>> getExecutorUpdate(
     // This is the regular path for when we have a CanonicalQuery.
     unique_ptr<CanonicalQuery> cq(parsedUpdate->releaseParsedQuery());
 
+    // Transfer the explain verbosity level into the expression context.
+    cq->getExpCtx()->explain = verbosity;
+
     const size_t defaultPlannerOptions = 0;
     StatusWith<PrepareExecutionResult> executionResult =
         prepareExecution(opCtx, collection, ws.get(), std::move(cq), defaultPlannerOptions);
diff --git a/src/mongo/db/query/get_executor.h b/src/mongo/db/query/get_executor.h
index 51fd3b008af..99e1657c6a7 100644
--- a/src/mongo/db/query/get_executor.h
+++ b/src/mongo/db/query/get_executor.h
@@ -218,6 +218,9 @@ StatusWith<std::unique_ptr<PlanExecutor, PlanExecutor::Deleter>> getExecutorCoun
  *
  * 'opDebug' Optional argument. When not null, will be used to record operation statistics.
  *
+ * If the delete operation is executed in explain mode, the 'verbosity' parameter should be
+ * set to the requested verbosity level, or boost::none otherwise.
+ *
  * The returned PlanExecutor will used the YieldPolicy returned by parsedDelete->yieldPolicy().
  *
  * Does not take ownership of its arguments.
@@ -228,7 +231,11 @@ StatusWith<std::unique_ptr<PlanExecutor, PlanExecutor::Deleter>> getExecutorCoun
  * If the query cannot be executed, returns a Status indicating why.
  */
 StatusWith<std::unique_ptr<PlanExecutor, PlanExecutor::Deleter>> getExecutorDelete(
-    OperationContext* opCtx, OpDebug* opDebug, Collection* collection, ParsedDelete* parsedDelete);
+    OperationContext* opCtx,
+    OpDebug* opDebug,
+    Collection* collection,
+    ParsedDelete* parsedDelete,
+    boost::optional<ExplainOptions::Verbosity> verbosity);
 
 /**
  * Get a PlanExecutor for an update operation. 'parsedUpdate' describes the query predicate
@@ -238,6 +245,9 @@ StatusWith<std::unique_ptr<PlanExecutor, PlanExecutor::Deleter>> getExecutorDele
  *
  * 'opDebug' Optional argument. When not null, will be used to record operation statistics.
  *
+ * If the delete operation is executed in explain mode, the 'verbosity' parameter should be
+ * set to the requested verbosity level, or boost::none otherwise.
+ *
  * The returned PlanExecutor will used the YieldPolicy returned by parsedUpdate->yieldPolicy().
  *
  * Does not take ownership of its arguments.
@@ -248,5 +258,9 @@ StatusWith<std::unique_ptr<PlanExecutor, PlanExecutor::Deleter>> getExecutorDele
  * If the query cannot be executed, returns a Status indicating why.
  */
 StatusWith<std::unique_ptr<PlanExecutor, PlanExecutor::Deleter>> getExecutorUpdate(
-    OperationContext* opCtx, OpDebug* opDebug, Collection* collection, ParsedUpdate* parsedUpdate);
+    OperationContext* opCtx,
+    OpDebug* opDebug,
+    Collection* collection,
+    ParsedUpdate* parsedUpdate,
+    boost::optional<ExplainOptions::Verbosity> verbosity);
 }  // namespace mongo
diff --git a/src/mongo/db/query/stage_builder.cpp b/src/mongo/db/query/stage_builder.cpp
index d7afdebefbb..76b00bfd6b1 100644
--- a/src/mongo/db/query/stage_builder.cpp
+++ b/src/mongo/db/query/stage_builder.cpp
@@ -154,8 +154,9 @@ std::unique_ptr<PlanStage> buildStages(OperationContext* opCtx,
         case STAGE_PROJECTION_COVERED: {
             auto pn = static_cast<const ProjectionNodeCovered*>(root);
             auto childStage = buildStages(opCtx, collection, cq, qsol, pn->children[0], ws);
-            return std::make_unique<ProjectionStageCovered>(opCtx,
+            return std::make_unique<ProjectionStageCovered>(cq.getExpCtx(),
                                                             cq.getQueryRequest().getProj(),
+                                                            cq.getProj(),
                                                             ws,
                                                             std::move(childStage),
                                                             pn->coveredKeyObj);
@@ -163,8 +164,11 @@ std::unique_ptr<PlanStage> buildStages(OperationContext* opCtx,
         case STAGE_PROJECTION_SIMPLE: {
             auto pn = static_cast<const ProjectionNodeSimple*>(root);
             auto childStage = buildStages(opCtx, collection, cq, qsol, pn->children[0], ws);
-            return std::make_unique<ProjectionStageSimple>(
-                opCtx, cq.getQueryRequest().getProj(), ws, std::move(childStage));
+            return std::make_unique<ProjectionStageSimple>(cq.getExpCtx(),
+                                                           cq.getQueryRequest().getProj(),
+                                                           cq.getProj(),
+                                                           ws,
+                                                           std::move(childStage));
         }
         case STAGE_LIMIT: {
             const LimitNode* ln = static_cast<const LimitNode*>(root);
diff --git a/src/mongo/db/repl/storage_interface_impl.cpp b/src/mongo/db/repl/storage_interface_impl.cpp
index 79a05656b9d..0770b586e37 100644
--- a/src/mongo/db/repl/storage_interface_impl.cpp
+++ b/src/mongo/db/repl/storage_interface_impl.cpp
@@ -863,8 +863,8 @@ Status _updateWithQuery(OperationContext* opCtx,
             uassertStatusOK(opCtx->recoveryUnit()->setTimestamp(ts));
         }
 
-        auto planExecutorResult =
-            mongo::getExecutorUpdate(opCtx, nullptr, collection, &parsedUpdate);
+        auto planExecutorResult = mongo::getExecutorUpdate(
+            opCtx, nullptr, collection, &parsedUpdate, boost::none /* verbosity */);
         if (!planExecutorResult.isOK()) {
             return planExecutorResult.getStatus();
         }
@@ -992,8 +992,8 @@ Status StorageInterfaceImpl::deleteByFilter(OperationContext* opCtx,
         }
         auto collection = collectionResult.getValue();
 
-        auto planExecutorResult =
-            mongo::getExecutorDelete(opCtx, nullptr, collection, &parsedDelete);
+        auto planExecutorResult = mongo::getExecutorDelete(
+            opCtx, nullptr, collection, &parsedDelete, boost::none /* verbosity */);
         if (!planExecutorResult.isOK()) {
             return planExecutorResult.getStatus();
         }