Delete ShardNamer interface.

Author: krk

src/mongo/db/SConscript

@@ -1028,7 +1028,6 @@ env.Library(
         'exec/shard_filter.cpp',
         'exec/shard_filterer_impl.cpp',
         'exec/shard_name.cpp',
-        'exec/shard_namer_impl.cpp',
         'exec/skip.cpp',
         'exec/sort.cpp',
         'exec/sort_key_generator.cpp',

src/mongo/db/exec/shard_name.cpp

@@ -36,6 +36,7 @@
 #include "mongo/db/exec/filter.h"
 #include "mongo/db/exec/scoped_timer.h"
 #include "mongo/db/exec/working_set_common.h"
+#include "mongo/db/s/sharding_state.h"
 #include "mongo/s/shard_key_pattern.h"
 
 namespace mongo {
@@ -49,12 +50,11 @@ using std::string;
 const char* ShardNameStage::kStageType = "SHARD_NAME";
 
 ShardNameStage::ShardNameStage(OperationContext* opCtx,
-                               ScopedCollectionMetadata metadata,
                                WorkingSet* ws,
                                std::unique_ptr<PlanStage> child)
-    : PlanStage(kStageType, opCtx), _ws(ws), _shardNamer(std::move(metadata)) {
+    : PlanStage(kStageType, opCtx), _ws(ws) {
     _children.emplace_back(std::move(child));
-}
+ }
 
 ShardNameStage::~ShardNameStage() {}
 
@@ -72,12 +72,12 @@ PlanStage::StageState ShardNameStage::doWork(WorkingSetID* out) {
 
     if (PlanStage::ADVANCED == status) {
         // If we're sharded make sure to add shardName to the output.
-        if (_shardNamer.isCollectionSharded()) {
+        auto sharding = ShardingState::get(this->getOpCtx());
+        if (sharding->enabled()) {
             WorkingSetMember* member = _ws->get(*out);
-            const StringData shardName = _shardNamer.shardName();
 
             // Populate the working set member with the shard name and return it.
-            member->metadata().setShardName(shardName);
+            member->metadata().setShardName(sharding->shardId());
         }
 
         // If we're here either we have shard state and added the shardName, or we have no shard

src/mongo/db/exec/shard_name.h

@@ -30,14 +30,12 @@
 #pragma once
 
 #include "mongo/db/exec/plan_stage.h"
-#include "mongo/db/exec/shard_namer_impl.h"
 
 namespace mongo {
 
 class ShardNameStage final : public PlanStage {
 public:
     ShardNameStage(OperationContext* opCtx,
-                   ScopedCollectionMetadata metadata,
                    WorkingSet* ws,
                    std::unique_ptr<PlanStage> child);
     ~ShardNameStage();
@@ -57,14 +55,6 @@ class ShardNameStage final : public PlanStage {
 
 private:
     WorkingSet* _ws;
-
-    // Note: it is important that this owns the ScopedCollectionMetadata from the time this stage
-    // is constructed. See ScopedCollectionMetadata class comment and MetadataManager comment for
-    // details. The existence of the ScopedCollectionMetadata prevents data which may have been
-    // migrated from being deleted while the query is still active. If we didn't hold one
-    // ScopedCollectionMetadata for the entire query, it'd be possible for data which the query
-    // needs to read to be deleted while it's still running.
-    ShardNamerImpl _shardNamer;
 };
 
 }  // namespace mongo

src/mongo/db/exec/shard_namer.h

@@ -283,12 +283,9 @@ std::unique_ptr<PlanStage> buildStages(OperationContext* opCtx,
             warning() << "building stage: STAGE_SHARD_NAME";
             const ShardNameNode* fn = static_cast<const ShardNameNode*>(root);
             auto childStage = buildStages(opCtx, collection, cq, qsol, fn->children[0], ws);
-            if (nullptr == childStage) {
-                return nullptr;
-            }
-
-            auto css = CollectionShardingState::get(opCtx, collection->ns());
-            return std::make_unique<ShardNameStage>(opCtx, css->getCurrentMetadata(), ws, std::move(childStage));
+            return childStage == nullptr
+                ? nullptr
+                : std::make_unique<ShardNameStage>(opCtx, ws, std::move(childStage));
         }
         case STAGE_DISTINCT_SCAN: {
             const DistinctNode* dn = static_cast<const DistinctNode*>(root);