SERVER-62247 Avoid making copies of the vector in TargetedWriteBatch::getWrites()

2 files changed, 10 insertions, 20 deletions

diff --git a/src/mongo/s/write_ops/batch_write_op.cpp b/src/mongo/s/write_ops/batch_write_op.cpp
index 4ac63ff2b1b..85138b92db0 100644
--- a/src/mongo/s/write_ops/batch_write_op.cpp
+++ b/src/mongo/s/write_ops/batch_write_op.cpp
@@ -392,7 +392,7 @@ Status BatchWriteOp::targetBatch(const NSTargeter& targeter,
         // StaleShardVersion and has to return number of errors equivalent to the number of writes
         // in the batch, the response size will not exceed the max BSON size.
         //
-        // The constant of 272 is chosen as an approximation of the size of the BSON representataion
+        // The constant of 272 is chosen as an approximation of the size of the BSON representation
         // of the StaleConfigInfo (which contains the shard id) and the adjacent error message.
         const int errorResponsePotentialSizeBytes =
             ordered ? 0 : write_ops::kWriteCommandBSONArrayPerElementOverheadBytes + 272;
@@ -474,7 +474,7 @@ BatchedCommandRequest BatchWriteOp::buildBatchRequest(const TargetedWriteBatch&
     boost::optional<std::vector<write_ops::UpdateOpEntry>> updates;
     boost::optional<std::vector<write_ops::DeleteOpEntry>> deletes;
 
-    for (const auto& targetedWrite : targetedBatch.getWrites()) {
+    for (auto&& targetedWrite : targetedBatch.getWrites()) {
         const WriteOpRef& writeOpRef = targetedWrite->writeOpRef;
 
         switch (batchType) {
@@ -625,7 +625,7 @@ void BatchWriteOp::noteBatchResponse(const TargetedWriteBatch& targetedBatch,
     }
 
     //
-    // Go through all pending responses of the op and sorted remote reponses, populate errors
+    // Go through all pending responses of the op and sorted remote responses, populate errors
     // This will either set all errors to the batch error or apply per-item errors as-needed
     //
     // If the batch is ordered, cancel all writes after the first error for retargeting.
@@ -757,7 +757,7 @@ bool BatchWriteOp::isFinished() {
 }
 
 void BatchWriteOp::buildClientResponse(BatchedCommandResponse* batchResp) {
-    // Note: we aggresively abandon the batch when encountering errors during transactions, so
+    // Note: we aggressively abandon the batch when encountering errors during transactions, so
     // it can be in a state that is not "finished" even for unordered batches.
     dassert(_inTransaction || isFinished());
 
@@ -892,13 +892,8 @@ void BatchWriteOp::_cancelBatches(const WriteErrorDetail& why,
     // Collect all the writeOps that are currently targeted
     for (TargetedBatchMap::iterator it = batchMap.begin(); it != batchMap.end();) {
         TargetedWriteBatch* batch = it->second;
-        const std::vector<TargetedWrite*>& writes = batch->getWrites();
-
-        for (std::vector<TargetedWrite*>::const_iterator writeIt = writes.begin();
-             writeIt != writes.end();
-             ++writeIt) {
-            TargetedWrite* write = *writeIt;
 
+        for (auto&& write : batch->getWrites()) {
             // NOTE: We may repeatedly cancel a write op here, but that's fast and we want to cancel
             // before erasing the TargetedWrite* (which owns the cancelled targeting info) for
             // reporting reasons.
@@ -973,13 +968,6 @@ const std::vector<ShardError>& TrackedErrors::getErrors(int errCode) const {
     return _errorMap.find(errCode)->second;
 }
 
-std::vector<TargetedWrite*> TargetedWriteBatch::getWrites() const {
-    std::vector<TargetedWrite*> rv;
-    std::transform(
-        _writes.begin(), _writes.end(), std::back_inserter(rv), [](auto&& w) { return w.get(); });
-    return rv;
-}
-
 void TargetedWriteBatch::addWrite(std::unique_ptr<TargetedWrite> targetedWrite, int estWriteSize) {
     _writes.push_back(std::move(targetedWrite));
     _estimatedSizeBytes += estWriteSize;
diff --git a/src/mongo/s/write_ops/batch_write_op.h b/src/mongo/s/write_ops/batch_write_op.h
index 70c3a3ba7b1..83156122a3b 100644
--- a/src/mongo/s/write_ops/batch_write_op.h
+++ b/src/mongo/s/write_ops/batch_write_op.h
@@ -267,7 +267,9 @@ public:
         return _endpoint;
     }
 
-    std::vector<TargetedWrite*> getWrites() const;
+    const std::vector<std::unique_ptr<TargetedWrite>>& getWrites() const {
+        return _writes;
+    };
 
     size_t getNumOps() const {
         return _writes.size();
@@ -290,8 +292,8 @@ private:
     // TargetedWrite*s are owned by the TargetedWriteBatch
     std::vector<std::unique_ptr<TargetedWrite>> _writes;
 
-    // Conservatvely estimated size of the batch, for ensuring it doesn't grow past the maximum BSON
-    // size
+    // Conservatively estimated size of the batch, for ensuring it doesn't grow past the maximum
+    // BSON size
     int _estimatedSizeBytes{0};
 };