SERVER-70830 Unit test `WiredTigerOperationStats`

9 files changed, 474 insertions, 180 deletions

diff --git a/src/mongo/db/storage/recovery_unit.h b/src/mongo/db/storage/recovery_unit.h
index 20c49c637d3..9e173d632e7 100644
--- a/src/mongo/db/storage/recovery_unit.h
+++ b/src/mongo/db/storage/recovery_unit.h
@@ -37,6 +37,7 @@
 #include "mongo/bson/timestamp.h"
 #include "mongo/db/repl/read_concern_level.h"
 #include "mongo/db/storage/snapshot.h"
+#include "mongo/db/storage/storage_stats.h"
 #include "mongo/util/decorable.h"
 
 namespace mongo {
@@ -76,37 +77,6 @@ enum class PrepareConflictBehavior {
 };
 
 /**
- * Storage statistics management class, with interfaces to provide the statistics in the BSON format
- * and an operator to add the statistics values.
- */
-class StorageStats {
-    StorageStats(const StorageStats&) = delete;
-    StorageStats& operator=(const StorageStats&) = delete;
-
-public:
-    StorageStats() = default;
-
-    virtual ~StorageStats(){};
-
-    /**
-     * Provides the storage statistics in the form of a BSONObj.
-     */
-    virtual BSONObj toBSON() = 0;
-
-    /**
-     * Add the statistics values.
-     */
-    virtual StorageStats& operator+=(const StorageStats&) = 0;
-
-    /**
-     * Provides the ability to create an instance of this class outside of the storage integration
-     * layer.
-     */
-    virtual std::shared_ptr<StorageStats> getCopy() = 0;
-};
-
-
-/**
  * A RecoveryUnit is responsible for ensuring that data is persisted.
  * All on-disk information must be mutated through this interface.
  */
diff --git a/src/mongo/db/storage/storage_stats.h b/src/mongo/db/storage/storage_stats.h
new file mode 100644
index 00000000000..b0afd2ba16d
--- /dev/null
+++ b/src/mongo/db/storage/storage_stats.h
@@ -0,0 +1,57 @@
+/**
+ *    Copyright (C) 2022-present MongoDB, Inc.
+ *
+ *    This program is free software: you can redistribute it and/or modify
+ *    it under the terms of the Server Side Public License, version 1,
+ *    as published by MongoDB, Inc.
+ *
+ *    This program is distributed in the hope that it will be useful,
+ *    but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *    Server Side Public License for more details.
+ *
+ *    You should have received a copy of the Server Side Public License
+ *    along with this program. If not, see
+ *    <http://www.mongodb.com/licensing/server-side-public-license>.
+ *
+ *    As a special exception, the copyright holders give permission to link the
+ *    code of portions of this program with the OpenSSL library under certain
+ *    conditions as described in each individual source file and distribute
+ *    linked combinations including the program with the OpenSSL library. You
+ *    must comply with the Server Side Public License in all respects for
+ *    all of the code used other than as permitted herein. If you modify file(s)
+ *    with this exception, you may extend this exception to your version of the
+ *    file(s), but you are not obligated to do so. If you do not wish to do so,
+ *    delete this exception statement from your version. If you delete this
+ *    exception statement from all source files in the program, then also delete
+ *    it in the license file.
+ */
+
+#pragma once
+
+#include "mongo/bson/bsonobj.h"
+
+namespace mongo {
+
+/**
+ * Manages statistics from the storage engine, allowing addition of statistics and serialization to
+ * BSON.
+ */
+class StorageStats {
+public:
+    StorageStats() = default;
+
+    StorageStats(const StorageStats&) = delete;
+    StorageStats(StorageStats&&) = delete;
+    StorageStats& operator=(const StorageStats&) = delete;
+
+    virtual ~StorageStats() = default;
+
+    virtual BSONObj toBSON() const = 0;
+
+    virtual std::shared_ptr<StorageStats> clone() const = 0;
+
+    virtual StorageStats& operator+=(const StorageStats&) = 0;
+};
+
+}  // namespace mongo
diff --git a/src/mongo/db/storage/wiredtiger/SConscript b/src/mongo/db/storage/wiredtiger/SConscript
index 68a76639ed5..638cf0b933c 100644
--- a/src/mongo/db/storage/wiredtiger/SConscript
+++ b/src/mongo/db/storage/wiredtiger/SConscript
@@ -37,6 +37,7 @@ wtEnv.Library(
         'wiredtiger_index.cpp',
         'wiredtiger_index_util.cpp',
         'wiredtiger_kv_engine.cpp',
+        'wiredtiger_operation_stats.cpp',
         'wiredtiger_oplog_manager.cpp',
         'wiredtiger_parameters.cpp',
         'wiredtiger_prepare_conflict.cpp',
@@ -133,6 +134,7 @@ wtEnv.CppUnitTest(
         'wiredtiger_init_test.cpp',
         'wiredtiger_c_api_test.cpp',
         'wiredtiger_kv_engine_test.cpp',
+        'wiredtiger_operation_stats_test.cpp',
         'wiredtiger_recovery_unit_test.cpp',
         'wiredtiger_session_cache_test.cpp',
         'wiredtiger_util_test.cpp',
diff --git a/src/mongo/db/storage/wiredtiger/wiredtiger_operation_stats.cpp b/src/mongo/db/storage/wiredtiger/wiredtiger_operation_stats.cpp
new file mode 100644
index 00000000000..ebf3842e7bc
--- /dev/null
+++ b/src/mongo/db/storage/wiredtiger/wiredtiger_operation_stats.cpp
@@ -0,0 +1,139 @@
+/**
+ *    Copyright (C) 2022-present MongoDB, Inc.
+ *
+ *    This program is free software: you can redistribute it and/or modify
+ *    it under the terms of the Server Side Public License, version 1,
+ *    as published by MongoDB, Inc.
+ *
+ *    This program is distributed in the hope that it will be useful,
+ *    but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *    Server Side Public License for more details.
+ *
+ *    You should have received a copy of the Server Side Public License
+ *    along with this program. If not, see
+ *    <http://www.mongodb.com/licensing/server-side-public-license>.
+ *
+ *    As a special exception, the copyright holders give permission to link the
+ *    code of portions of this program with the OpenSSL library under certain
+ *    conditions as described in each individual source file and distribute
+ *    linked combinations including the program with the OpenSSL library. You
+ *    must comply with the Server Side Public License in all respects for
+ *    all of the code used other than as permitted herein. If you modify file(s)
+ *    with this exception, you may extend this exception to your version of the
+ *    file(s), but you are not obligated to do so. If you do not wish to do so,
+ *    delete this exception statement from your version. If you delete this
+ *    exception statement from all source files in the program, then also delete
+ *    it in the license file.
+ */
+
+#include "mongo/db/storage/wiredtiger/wiredtiger_operation_stats.h"
+
+#include "mongo/bson/bsonobjbuilder.h"
+#include "mongo/db/storage/wiredtiger/wiredtiger_util.h"
+
+namespace mongo {
+namespace {
+
+enum class StatType { kData, kWait };
+
+struct StatInfo {
+    StringData name;
+    StatType type;
+};
+
+stdx::unordered_map<int, StatInfo> statInfo = {
+    {WT_STAT_SESSION_BYTES_READ, {"bytesRead"_sd, StatType::kData}},
+    {WT_STAT_SESSION_BYTES_WRITE, {"bytesWritten"_sd, StatType::kData}},
+    {WT_STAT_SESSION_LOCK_DHANDLE_WAIT, {"handleLock"_sd, StatType::kWait}},
+    {WT_STAT_SESSION_READ_TIME, {"timeReadingMicros"_sd, StatType::kData}},
+    {WT_STAT_SESSION_WRITE_TIME, {"timeWritingMicros"_sd, StatType::kData}},
+    {WT_STAT_SESSION_LOCK_SCHEMA_WAIT, {"schemaLock"_sd, StatType::kWait}},
+    {WT_STAT_SESSION_CACHE_TIME, {"cache"_sd, StatType::kWait}}};
+
+}  // namespace
+
+WiredTigerOperationStats::WiredTigerOperationStats(WT_SESSION* session) {
+    invariant(session);
+
+    WT_CURSOR* c;
+    uassert(ErrorCodes::CursorNotFound,
+            "Unable to open statistics cursor",
+            !session->open_cursor(session, "statistics:session", nullptr, "statistics=(fast)", &c));
+
+    ScopeGuard guard{[c] { c->close(c); }};
+
+    int32_t key;
+    uint64_t value;
+    while (c->next(c) == 0 && c->get_key(c, &key) == 0) {
+        fassert(51035, c->get_value(c, nullptr, nullptr, &value) == 0);
+        _stats[key] = WiredTigerUtil::castStatisticsValue<long long>(value);
+    }
+
+    // Reset the statistics so that the next fetch gives the recent values.
+    invariantWTOK(c->reset(c), c->session);
+}
+
+BSONObj WiredTigerOperationStats::toBSON() const {
+    boost::optional<BSONObjBuilder> dataSection;
+    boost::optional<BSONObjBuilder> waitSection;
+
+    for (auto&& [stat, value] : _stats) {
+        if (value == 0) {
+            continue;
+        }
+
+        auto it = statInfo.find(stat);
+        if (it == statInfo.end()) {
+            continue;
+        }
+        auto&& [name, type] = it->second;
+
+        auto appendToSection = [name = name,
+                                value = value](boost::optional<BSONObjBuilder>& section) {
+            if (!section) {
+                section.emplace();
+            }
+            section->append(name, value);
+        };
+
+        switch (type) {
+            case StatType::kData:
+                appendToSection(dataSection);
+                break;
+            case StatType::kWait:
+                appendToSection(waitSection);
+                break;
+        }
+    }
+
+    BSONObjBuilder builder;
+    if (dataSection) {
+        builder.append("data", dataSection->obj());
+    }
+    if (waitSection) {
+        builder.append("timeWaitingMicros", waitSection->obj());
+    }
+
+    return builder.obj();
+}
+
+std::shared_ptr<StorageStats> WiredTigerOperationStats::clone() const {
+    auto copy = std::make_shared<WiredTigerOperationStats>();
+    *copy += *this;
+    return copy;
+}
+
+WiredTigerOperationStats& WiredTigerOperationStats::operator+=(
+    const WiredTigerOperationStats& other) {
+    for (auto&& [stat, value] : other._stats) {
+        _stats[stat] += value;
+    }
+    return *this;
+}
+
+StorageStats& WiredTigerOperationStats::operator+=(const StorageStats& other) {
+    return *this += checked_cast<const WiredTigerOperationStats&>(other);
+}
+
+}  // namespace mongo
diff --git a/src/mongo/db/storage/wiredtiger/wiredtiger_operation_stats.h b/src/mongo/db/storage/wiredtiger/wiredtiger_operation_stats.h
new file mode 100644
index 00000000000..581303e30b8
--- /dev/null
+++ b/src/mongo/db/storage/wiredtiger/wiredtiger_operation_stats.h
@@ -0,0 +1,55 @@
+/**
+ *    Copyright (C) 2022-present MongoDB, Inc.
+ *
+ *    This program is free software: you can redistribute it and/or modify
+ *    it under the terms of the Server Side Public License, version 1,
+ *    as published by MongoDB, Inc.
+ *
+ *    This program is distributed in the hope that it will be useful,
+ *    but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *    Server Side Public License for more details.
+ *
+ *    You should have received a copy of the Server Side Public License
+ *    along with this program. If not, see
+ *    <http://www.mongodb.com/licensing/server-side-public-license>.
+ *
+ *    As a special exception, the copyright holders give permission to link the
+ *    code of portions of this program with the OpenSSL library under certain
+ *    conditions as described in each individual source file and distribute
+ *    linked combinations including the program with the OpenSSL library. You
+ *    must comply with the Server Side Public License in all respects for
+ *    all of the code used other than as permitted herein. If you modify file(s)
+ *    with this exception, you may extend this exception to your version of the
+ *    file(s), but you are not obligated to do so. If you do not wish to do so,
+ *    delete this exception statement from your version. If you delete this
+ *    exception statement from all source files in the program, then also delete
+ *    it in the license file.
+ */
+
+#pragma once
+
+#include <wiredtiger.h>
+
+#include "mongo/db/storage/storage_stats.h"
+
+namespace mongo {
+
+class WiredTigerOperationStats final : public StorageStats {
+public:
+    WiredTigerOperationStats() = default;
+    WiredTigerOperationStats(WT_SESSION* session);
+
+    BSONObj toBSON() const final;
+
+    std::shared_ptr<StorageStats> clone() const final;
+
+    StorageStats& operator+=(const StorageStats&) final;
+
+    WiredTigerOperationStats& operator+=(const WiredTigerOperationStats&);
+
+private:
+    std::map<int, long long> _stats;
+};
+
+}  // namespace mongo
diff --git a/src/mongo/db/storage/wiredtiger/wiredtiger_operation_stats_test.cpp b/src/mongo/db/storage/wiredtiger/wiredtiger_operation_stats_test.cpp
new file mode 100644
index 00000000000..2494b49923f
--- /dev/null
+++ b/src/mongo/db/storage/wiredtiger/wiredtiger_operation_stats_test.cpp
@@ -0,0 +1,217 @@
+/**
+ *    Copyright (C) 2022-present MongoDB, Inc.
+ *
+ *    This program is free software: you can redistribute it and/or modify
+ *    it under the terms of the Server Side Public License, version 1,
+ *    as published by MongoDB, Inc.
+ *
+ *    This program is distributed in the hope that it will be useful,
+ *    but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *    Server Side Public License for more details.
+ *
+ *    You should have received a copy of the Server Side Public License
+ *    along with this program. If not, see
+ *    <http://www.mongodb.com/licensing/server-side-public-license>.
+ *
+ *    As a special exception, the copyright holders give permission to link the
+ *    code of portions of this program with the OpenSSL library under certain
+ *    conditions as described in each individual source file and distribute
+ *    linked combinations including the program with the OpenSSL library. You
+ *    must comply with the Server Side Public License in all respects for
+ *    all of the code used other than as permitted herein. If you modify file(s)
+ *    with this exception, you may extend this exception to your version of the
+ *    file(s), but you are not obligated to do so. If you do not wish to do so,
+ *    delete this exception statement from your version. If you delete this
+ *    exception statement from all source files in the program, then also delete
+ *    it in the license file.
+ */
+
+#include "mongo/db/storage/wiredtiger/wiredtiger_operation_stats.h"
+#include "mongo/unittest/temp_dir.h"
+#include "mongo/unittest/unittest.h"
+
+namespace mongo {
+namespace {
+
+#define ASSERT_WT_OK(result) ASSERT_EQ(result, 0) << wiredtiger_strerror(result)
+
+class WiredTigerOperationStatsTest : public unittest::Test {
+protected:
+    void setUp() override {
+        ASSERT_WT_OK(
+            wiredtiger_open(_path.path().c_str(), nullptr, "create,statistics=(fast),", &_conn));
+        ASSERT_WT_OK(_conn->open_session(_conn, nullptr, "isolation=snapshot", &_session));
+        ASSERT_WT_OK(_session->create(
+            _session, _uri.c_str(), "type=file,key_format=q,value_format=u,log=(enabled=false)"));
+    }
+
+    void tearDown() override {
+        ASSERT_EQ(_conn->close(_conn, nullptr), 0);
+    }
+
+    /**
+     * Writes the given data using WT. Causes the bytesWritten and timeWritingMicros stats to be
+     * incremented.
+     */
+    void write(const std::string& data) {
+        ASSERT_WT_OK(_session->begin_transaction(_session, nullptr));
+
+        WT_CURSOR* cursor;
+        ASSERT_WT_OK(_session->open_cursor(_session, _uri.c_str(), nullptr, nullptr, &cursor));
+
+        cursor->set_key(cursor, _key++);
+
+        WT_ITEM item{data.data(), data.size()};
+        cursor->set_value(cursor, &item);
+
+        ASSERT_WT_OK(cursor->insert(cursor));
+        ASSERT_WT_OK(cursor->close(cursor));
+        ASSERT_WT_OK(_session->commit_transaction(_session, nullptr));
+        ASSERT_WT_OK(_session->checkpoint(_session, nullptr));
+    }
+
+    /**
+     * Reads all of the previously written data from WT. Causes the bytesRead and timeReadingMicros
+     * stats to be incremented.
+     */
+    void read() {
+        tearDown();
+        setUp();
+
+        ASSERT_WT_OK(_session->begin_transaction(_session, nullptr));
+
+        WT_CURSOR* cursor;
+        ASSERT_WT_OK(_session->open_cursor(_session, _uri.c_str(), nullptr, nullptr, &cursor));
+
+        for (int64_t i = 0; i < _key; ++i) {
+            cursor->set_key(cursor, i);
+            ASSERT_WT_OK(cursor->search(cursor));
+
+            WT_ITEM value;
+            ASSERT_WT_OK(cursor->get_value(cursor, &value));
+        }
+
+        ASSERT_WT_OK(cursor->close(cursor));
+        ASSERT_WT_OK(_session->commit_transaction(_session, nullptr));
+    }
+
+    unittest::TempDir _path{"wiredtiger_operation_stats_test"};
+    std::string _uri{"table:wiredtiger_operation_stats_test"};
+    WT_CONNECTION* _conn;
+    WT_SESSION* _session;
+    int64_t _key = 0;
+};
+
+TEST_F(WiredTigerOperationStatsTest, Empty) {
+    ASSERT_BSONOBJ_EQ(WiredTigerOperationStats{_session}.toBSON(), BSONObj{});
+}
+
+TEST_F(WiredTigerOperationStatsTest, Write) {
+    write("a");
+
+    auto statsObj = WiredTigerOperationStats{_session}.toBSON();
+
+    auto dataSection = statsObj["data"];
+    ASSERT_EQ(dataSection.type(), BSONType::Object) << statsObj;
+
+    ASSERT(dataSection["bytesWritten"]) << statsObj;
+    ASSERT(dataSection["timeWritingMicros"]) << statsObj;
+    for (auto&& [name, value] : dataSection.Obj()) {
+        ASSERT_EQ(value.type(), BSONType::NumberLong) << statsObj;
+        ASSERT_GT(value.numberLong(), 0) << statsObj;
+    }
+}
+
+TEST_F(WiredTigerOperationStatsTest, Read) {
+    write("a");
+    read();
+
+    auto statsObj = WiredTigerOperationStats{_session}.toBSON();
+
+    auto dataSection = statsObj["data"];
+    ASSERT_EQ(dataSection.type(), BSONType::Object) << statsObj;
+
+    ASSERT(dataSection["bytesRead"]) << statsObj;
+    ASSERT(dataSection["timeReadingMicros"]) << statsObj;
+    for (auto&& [name, value] : dataSection.Obj()) {
+        ASSERT_EQ(value.type(), BSONType::NumberLong) << statsObj;
+        ASSERT_GT(value.numberLong(), 0) << statsObj;
+    }
+}
+
+TEST_F(WiredTigerOperationStatsTest, Large) {
+    auto remaining = static_cast<int64_t>(std::numeric_limits<uint32_t>::max()) + 1;
+    while (remaining > 0) {
+        std::string data(1024 * 1024, 'a');
+        remaining -= data.size();
+        write(data);
+    }
+
+    auto statsObj = WiredTigerOperationStats{_session}.toBSON();
+    ASSERT_GT(statsObj["data"]["bytesWritten"].Long(), std::numeric_limits<uint32_t>::max())
+        << statsObj;
+
+    read();
+
+    statsObj = WiredTigerOperationStats{_session}.toBSON();
+    ASSERT_GT(statsObj["data"]["bytesRead"].Long(), std::numeric_limits<uint32_t>::max())
+        << statsObj;
+}
+
+TEST_F(WiredTigerOperationStatsTest, Add) {
+    std::vector<std::unique_ptr<WiredTigerOperationStats>> stats;
+
+    write("a");
+    stats.push_back(std::make_unique<WiredTigerOperationStats>(_session));
+
+    read();
+    stats.push_back(std::make_unique<WiredTigerOperationStats>(_session));
+
+    write("aa");
+    stats.push_back(std::make_unique<WiredTigerOperationStats>(_session));
+
+    read();
+    stats.push_back(std::make_unique<WiredTigerOperationStats>(_session));
+
+    long long bytesWritten = 0;
+    long long timeWritingMicros = 0;
+    long long bytesRead = 0;
+    long long timeReadingMicros = 0;
+
+    WiredTigerOperationStats combined;
+
+    for (auto&& op : stats) {
+        auto statsObj = op->toBSON();
+
+        bytesWritten += statsObj["data"]["bytesWritten"].numberLong();
+        timeWritingMicros += statsObj["data"]["timeWritingMicros"].numberLong();
+        bytesRead += statsObj["data"]["bytesRead"].numberLong();
+        timeReadingMicros += statsObj["data"]["timeReadingMicros"].numberLong();
+
+        combined += *op;
+    }
+
+    auto combinedObj = combined.toBSON();
+    auto dataSection = combinedObj["data"];
+    ASSERT_EQ(dataSection.type(), BSONType::Object) << combinedObj;
+    ASSERT_EQ(dataSection["bytesWritten"].Long(), bytesWritten) << combinedObj;
+    ASSERT_EQ(dataSection["timeWritingMicros"].Long(), timeWritingMicros) << combinedObj;
+    ASSERT_EQ(dataSection["bytesRead"].Long(), bytesRead) << combinedObj;
+    ASSERT_EQ(dataSection["timeReadingMicros"].Long(), timeReadingMicros) << combinedObj;
+}
+
+TEST_F(WiredTigerOperationStatsTest, Clone) {
+    write("a");
+
+    WiredTigerOperationStats stats{_session};
+    auto clone = stats.clone();
+
+    ASSERT_BSONOBJ_EQ(stats.toBSON(), clone->toBSON());
+
+    stats += *clone;
+    ASSERT_BSONOBJ_NE(stats.toBSON(), clone->toBSON());
+}
+
+}  // namespace
+}  // namespace mongo
diff --git a/src/mongo/db/storage/wiredtiger/wiredtiger_recovery_unit.cpp b/src/mongo/db/storage/wiredtiger/wiredtiger_recovery_unit.cpp
index 1f4d9d567b7..26f91072bbd 100644
--- a/src/mongo/db/storage/wiredtiger/wiredtiger_recovery_unit.cpp
+++ b/src/mongo/db/storage/wiredtiger/wiredtiger_recovery_unit.cpp
@@ -37,6 +37,7 @@
 #include "mongo/db/server_options.h"
 #include "mongo/db/storage/wiredtiger/wiredtiger_begin_transaction_block.h"
 #include "mongo/db/storage/wiredtiger/wiredtiger_kv_engine.h"
+#include "mongo/db/storage/wiredtiger/wiredtiger_operation_stats.h"
 #include "mongo/db/storage/wiredtiger/wiredtiger_prepare_conflict.h"
 #include "mongo/db/storage/wiredtiger/wiredtiger_session_cache.h"
 #include "mongo/db/storage/wiredtiger/wiredtiger_util.h"
@@ -82,107 +83,6 @@ void handleWriteContextForDebugging(WiredTigerRecoveryUnit& ru, Timestamp& ts) {
 
 AtomicWord<std::int64_t> snapshotTooOldErrorCount{0};
 
-using Section = WiredTigerOperationStats::Section;
-
-std::map<int, std::pair<StringData, Section>> WiredTigerOperationStats::_statNameMap = {
-    {WT_STAT_SESSION_BYTES_READ, std::make_pair("bytesRead"_sd, Section::DATA)},
-    {WT_STAT_SESSION_BYTES_WRITE, std::make_pair("bytesWritten"_sd, Section::DATA)},
-    {WT_STAT_SESSION_LOCK_DHANDLE_WAIT, std::make_pair("handleLock"_sd, Section::WAIT)},
-    {WT_STAT_SESSION_READ_TIME, std::make_pair("timeReadingMicros"_sd, Section::DATA)},
-    {WT_STAT_SESSION_WRITE_TIME, std::make_pair("timeWritingMicros"_sd, Section::DATA)},
-    {WT_STAT_SESSION_LOCK_SCHEMA_WAIT, std::make_pair("schemaLock"_sd, Section::WAIT)},
-    {WT_STAT_SESSION_CACHE_TIME, std::make_pair("cache"_sd, Section::WAIT)}};
-
-std::shared_ptr<StorageStats> WiredTigerOperationStats::getCopy() {
-    std::shared_ptr<WiredTigerOperationStats> copy = std::make_shared<WiredTigerOperationStats>();
-    *copy += *this;
-    return copy;
-}
-
-void WiredTigerOperationStats::fetchStats(WT_SESSION* session,
-                                          const std::string& uri,
-                                          const std::string& config) {
-    invariant(session);
-
-    WT_CURSOR* c = nullptr;
-    const char* cursorConfig = config.empty() ? nullptr : config.c_str();
-    int ret = session->open_cursor(session, uri.c_str(), nullptr, cursorConfig, &c);
-    uassert(ErrorCodes::CursorNotFound, "Unable to open statistics cursor", ret == 0);
-
-    invariant(c);
-    ON_BLOCK_EXIT([&] { c->close(c); });
-
-    const char* desc;
-    uint64_t value;
-    int32_t key;
-    while (c->next(c) == 0 && c->get_key(c, &key) == 0) {
-        fassert(51035, c->get_value(c, &desc, nullptr, &value) == 0);
-        _stats[key] = WiredTigerUtil::castStatisticsValue<long long>(value);
-    }
-
-    // Reset the statistics so that the next fetch gives the recent values.
-    invariantWTOK(c->reset(c), c->session);
-}
-
-BSONObj WiredTigerOperationStats::toBSON() {
-    BSONObjBuilder bob;
-    std::unique_ptr<BSONObjBuilder> dataSection;
-    std::unique_ptr<BSONObjBuilder> waitSection;
-
-    for (auto const& stat : _stats) {
-        // Find the user consumable name for this statistic.
-        auto statIt = _statNameMap.find(stat.first);
-
-        // Ignore the session statistic that is not reported for the slow operations.
-        if (statIt == _statNameMap.end())
-            continue;
-
-        auto statName = statIt->second.first;
-        Section subs = statIt->second.second;
-        long long val = stat.second;
-        // Add this statistic only if higher than zero.
-        if (val > 0) {
-            // Gather the statistic into its own subsection in the BSONObj.
-            switch (subs) {
-                case Section::DATA:
-                    if (!dataSection)
-                        dataSection = std::make_unique<BSONObjBuilder>();
-
-                    dataSection->append(statName, val);
-                    break;
-                case Section::WAIT:
-                    if (!waitSection)
-                        waitSection = std::make_unique<BSONObjBuilder>();
-
-                    waitSection->append(statName, val);
-                    break;
-                default:
-                    MONGO_UNREACHABLE;
-            }
-        }
-    }
-
-    if (dataSection)
-        bob.append("data", dataSection->obj());
-    if (waitSection)
-        bob.append("timeWaitingMicros", waitSection->obj());
-
-    return bob.obj();
-}
-
-WiredTigerOperationStats& WiredTigerOperationStats::operator+=(
-    const WiredTigerOperationStats& other) {
-    for (auto const& otherStat : other._stats) {
-        _stats[otherStat.first] += otherStat.second;
-    }
-    return (*this);
-}
-
-StorageStats& WiredTigerOperationStats::operator+=(const StorageStats& other) {
-    *this += checked_cast<const WiredTigerOperationStats&>(other);
-    return (*this);
-}
-
 WiredTigerRecoveryUnit::WiredTigerRecoveryUnit(WiredTigerSessionCache* sc)
     : WiredTigerRecoveryUnit(sc, sc->getKVEngine()->getOplogManager()) {}
 
@@ -996,18 +896,7 @@ void WiredTigerRecoveryUnit::beginIdle() {
 }
 
 std::shared_ptr<StorageStats> WiredTigerRecoveryUnit::getOperationStatistics() const {
-    std::shared_ptr<WiredTigerOperationStats> statsPtr(nullptr);
-
-    if (!_session)
-        return statsPtr;
-
-    WT_SESSION* s = _session->getSession();
-    invariant(s);
-
-    statsPtr = std::make_shared<WiredTigerOperationStats>();
-    statsPtr->fetchStats(s, "statistics:session", "statistics=(fast)");
-
-    return statsPtr;
+    return _session ? std::make_shared<WiredTigerOperationStats>(_session->getSession()) : nullptr;
 }
 
 void WiredTigerRecoveryUnit::setCatalogConflictingTimestamp(Timestamp timestamp) {
diff --git a/src/mongo/db/storage/wiredtiger/wiredtiger_recovery_unit.h b/src/mongo/db/storage/wiredtiger/wiredtiger_recovery_unit.h
index 26102686dbd..2d38888dc90 100644
--- a/src/mongo/db/storage/wiredtiger/wiredtiger_recovery_unit.h
+++ b/src/mongo/db/storage/wiredtiger/wiredtiger_recovery_unit.h
@@ -56,41 +56,6 @@ extern AtomicWord<std::int64_t> snapshotTooOldErrorCount;
 
 class BSONObjBuilder;
 
-class WiredTigerOperationStats final : public StorageStats {
-public:
-    /**
-     *  There are two types of statistics provided by WiredTiger engine - data and wait.
-     */
-    enum class Section { DATA, WAIT };
-
-    BSONObj toBSON() final;
-
-    StorageStats& operator+=(const StorageStats&) final;
-
-    WiredTigerOperationStats& operator+=(const WiredTigerOperationStats&);
-
-    /**
-     * Fetches an operation's storage statistics from WiredTiger engine.
-     */
-    void fetchStats(WT_SESSION*, const std::string&, const std::string&);
-
-    std::shared_ptr<StorageStats> getCopy() final;
-
-private:
-    /**
-     * Each statistic in WiredTiger has an integer key, which this map associates with a section
-     * (either DATA or WAIT) and user-readable name.
-     */
-    static std::map<int, std::pair<StringData, Section>> _statNameMap;
-
-    /**
-     * Stores the value for each statistic returned by a WiredTiger cursor. Each statistic is
-     * associated with an integer key, which can be mapped to a name and section using the
-     * '_statNameMap'.
-     */
-    std::map<int, long long> _stats;
-};
-
 class WiredTigerRecoveryUnit final : public RecoveryUnit {
 public:
     WiredTigerRecoveryUnit(WiredTigerSessionCache* sc);
diff --git a/src/mongo/db/transaction/transaction_metrics_observer.cpp b/src/mongo/db/transaction/transaction_metrics_observer.cpp
index 0a503e3b135..7a6544a1b3b 100644
--- a/src/mongo/db/transaction/transaction_metrics_observer.cpp
+++ b/src/mongo/db/transaction/transaction_metrics_observer.cpp
@@ -188,7 +188,7 @@ void TransactionMetricsObserver::onTransactionOperation(OperationContext* opCtx,
         if (storageStats) {
             CurOp::get(opCtx)->debug().storageStats = storageStats;
             if (!_singleTransactionStats.getOpDebug()->storageStats) {
-                _singleTransactionStats.getOpDebug()->storageStats = storageStats->getCopy();
+                _singleTransactionStats.getOpDebug()->storageStats = storageStats->clone();
             } else {
                 *_singleTransactionStats.getOpDebug()->storageStats += *storageStats;
             }