SERVER-69104 Avoid repeated creation of ColumnStoreEncoder

5 files changed, 28 insertions, 23 deletions

diff --git a/src/mongo/db/exec/sbe/stages/column_scan.cpp b/src/mongo/db/exec/sbe/stages/column_scan.cpp
index 66da5619ceb..c9b960ace59 100644
--- a/src/mongo/db/exec/sbe/stages/column_scan.cpp
+++ b/src/mongo/db/exec/sbe/stages/column_scan.cpp
@@ -32,23 +32,10 @@
 
 #include "mongo/db/exec/sbe/expressions/expression.h"
 #include "mongo/db/exec/sbe/size_estimator.h"
-#include "mongo/db/exec/sbe/values/column_store_encoder.h"
-#include "mongo/db/exec/sbe/values/columnar.h"
 #include "mongo/db/index/columns_access_method.h"
 
 namespace mongo {
 namespace sbe {
-namespace {
-TranslatedCell translateCell(PathView path, const SplitCellView& splitCellView) {
-    value::ColumnStoreEncoder encoder{};
-    SplitCellView::Cursor<value::ColumnStoreEncoder> cellCursor =
-        splitCellView.subcellValuesGenerator<value::ColumnStoreEncoder>(std::move(encoder));
-    return TranslatedCell{splitCellView.arrInfo, path, std::move(cellCursor)};
-}
-
-
-}  // namespace
-
 ColumnScanStage::ColumnScanStage(UUID collectionUuid,
                                  StringData columnIndexName,
                                  std::vector<std::string> paths,
@@ -307,6 +294,12 @@ void ColumnScanStage::open(bool reOpen) {
     _open = true;
 }
 
+TranslatedCell ColumnScanStage::translateCell(PathView path, const SplitCellView& splitCellView) {
+    SplitCellView::Cursor<value::ColumnStoreEncoder> cellCursor =
+        splitCellView.subcellValuesGenerator<value::ColumnStoreEncoder>(&_encoder);
+    return TranslatedCell{splitCellView.arrInfo, path, std::move(cellCursor)};
+}
+
 void ColumnScanStage::readParentsIntoObj(StringData path,
                                          value::Object* outObj,
                                          StringDataSet* pathsReadSetOut) {
diff --git a/src/mongo/db/exec/sbe/stages/column_scan.h b/src/mongo/db/exec/sbe/stages/column_scan.h
index 71f8489dfb3..e567b75ad8e 100644
--- a/src/mongo/db/exec/sbe/stages/column_scan.h
+++ b/src/mongo/db/exec/sbe/stages/column_scan.h
@@ -34,6 +34,8 @@
 #include "mongo/db/exec/sbe/stages/collection_helpers.h"
 #include "mongo/db/exec/sbe/stages/plan_stats.h"
 #include "mongo/db/exec/sbe/stages/stages.h"
+#include "mongo/db/exec/sbe/values/column_store_encoder.h"
+#include "mongo/db/exec/sbe/values/columnar.h"
 #include "mongo/db/storage/column_store.h"
 
 namespace mongo {
@@ -202,6 +204,8 @@ private:
         ColumnScanStats::CursorStats& _stats;
     };
 
+    TranslatedCell translateCell(PathView path, const SplitCellView& splitCellView);
+
     void readParentsIntoObj(StringData path, value::Object* out, StringDataSet* pathsReadSetOut);
 
     bool checkFilter(CellView cell, size_t filterIndex, const PathValue& path);
@@ -219,6 +223,8 @@ private:
     // Move cursors to the next record to be processed.
     RowId advanceCursors();
 
+    value::ColumnStoreEncoder _encoder{};
+
     // The columnar index this stage is scanning and the associated row store collection.
     const UUID _collUuid;
     const std::string _columnIndexName;
diff --git a/src/mongo/db/exec/sbe/values/column_store_encoder_test.cpp b/src/mongo/db/exec/sbe/values/column_store_encoder_test.cpp
index fba973a606a..f47faa329c7 100644
--- a/src/mongo/db/exec/sbe/values/column_store_encoder_test.cpp
+++ b/src/mongo/db/exec/sbe/values/column_store_encoder_test.cpp
@@ -61,7 +61,7 @@ TEST(SBEColumnStoreEncoder, EncodeTest) {
         StringData{columnStoreCell.buf(), static_cast<size_t>(columnStoreCell.len())});
 
     value::ColumnStoreEncoder encoder;
-    auto cellCursor = cellView.subcellValuesGenerator(encoder);
+    auto cellCursor = cellView.subcellValuesGenerator(&encoder);
 
     {
         auto cellValue = cellCursor.nextValue();
@@ -205,7 +205,7 @@ TEST(SBEColumnStoreEncoder, RoundTripConversionThroughSplitCellView) {
         SplitCellView::parse(StringData{cellBuffer.buf(), static_cast<size_t>(cellBuffer.len())});
 
     value::ColumnStoreEncoder encoder;
-    auto cellCursor = cellView.subcellValuesGenerator(encoder);
+    auto cellCursor = cellView.subcellValuesGenerator(&encoder);
 
     auto referenceIt = referenceBson.begin();
     while (auto&& cursorResult = cellCursor.nextValue()) {
@@ -366,7 +366,7 @@ TEST(SBEColumnStoreEncoder, ColumnsWithEmbeddedBSONElements) {
     // validating the translated outputs their respective comparison functions.
     //
     value::ColumnStoreEncoder encoder;
-    auto cellCursor = cellView.subcellValuesGenerator(encoder);
+    auto cellCursor = cellView.subcellValuesGenerator(&encoder);
 
     for (auto comparison : testComparisons) {
         auto cellValue = cellCursor.nextValue();
diff --git a/src/mongo/db/index/column_key_generator_test.cpp b/src/mongo/db/index/column_key_generator_test.cpp
index 65ab565df13..5e75e4ea674 100644
--- a/src/mongo/db/index/column_key_generator_test.cpp
+++ b/src/mongo/db/index/column_key_generator_test.cpp
@@ -56,7 +56,8 @@ private:
 public:
     UnencodedCellView toUnencodedCellView(const SplitCellView& view) {
         // Fill builder with bson-encoded elements from view.
-        auto cursor = view.subcellValuesGenerator(ValueEncoder{&builder});
+        ValueEncoder encoder{&builder};
+        auto cursor = view.subcellValuesGenerator(&encoder);
         while (cursor.nextValue()) {
             // Work done in ValueEncoder::operator() rather than here.
         }
diff --git a/src/mongo/db/storage/column_store.h b/src/mongo/db/storage/column_store.h
index 19472a633ec..c03170db3a7 100644
--- a/src/mongo/db/storage/column_store.h
+++ b/src/mongo/db/storage/column_store.h
@@ -391,7 +391,7 @@ struct SplitCellView {
                 return Out();
 
             invariant(elemPtr < end);
-            return decodeAndAdvance(elemPtr, encoder);
+            return decodeAndAdvance(elemPtr, *encoder);
         }
         bool hasNext() const {
             return elemPtr != end;
@@ -399,14 +399,19 @@ struct SplitCellView {
 
         const char* elemPtr;
         const char* end;
-        ValueEncoder encoder;
+        ValueEncoder* encoder;  // Unowned
     };
 
-
+    /**
+     * Construct a cursor that can iterate the values in a column store cell. Requires a
+     * 'ValueEncoder' that understands the binary format of cell data.
+     *
+     * Note: the 'ValueEncoder' is stored as an unowned pointer. The referenced encoder must stay
+     * valid for the lifetime of the returned cursor.
+     */
     template <class ValueEncoder>
-    auto subcellValuesGenerator(ValueEncoder&& valEncoder) const {
-        return Cursor<ValueEncoder>{
-            firstValuePtr, arrInfo.rawData(), std::forward<ValueEncoder>(valEncoder)};
+    auto subcellValuesGenerator(ValueEncoder* valEncoder) const {
+        return Cursor<ValueEncoder>{firstValuePtr, arrInfo.rawData(), valEncoder};
     }
 
     static SplitCellView parse(CellView cell) {