From d2b666dfc5428b097f78fb6f9b27996ebd76be2e Mon Sep 17 00:00:00 2001
From: JaySon-Huang <tshent@qq.com>
Date: Wed, 8 Nov 2023 19:45:31 +0800
Subject: [PATCH 1/2] Fix time step backward for
 `Stopwatch::elapsedFromLastTime`

---
 dbms/src/Common/Stopwatch.h | 20 ++++++++++++--------
 1 file changed, 12 insertions(+), 8 deletions(-)

diff --git a/dbms/src/Common/Stopwatch.h b/dbms/src/Common/Stopwatch.h
index 853d53f0db8..28763478cf9 100644
--- a/dbms/src/Common/Stopwatch.h
+++ b/dbms/src/Common/Stopwatch.h
@@ -30,7 +30,7 @@ inline UInt64 clock_gettime_ns(clockid_t clock_type = CLOCK_MONOTONIC)
     {
     };
     clock_gettime(clock_type, &ts);
-    return UInt64(ts.tv_sec * 1000000000ULL + ts.tv_nsec);
+    return static_cast<UInt64>(ts.tv_sec * 1000000000ULL + ts.tv_nsec);
 }
 
 /// Sometimes monotonic clock may not be monotonic (due to bug in kernel?).
@@ -64,14 +64,14 @@ class Stopwatch
 
     void start()
     {
-        start_ns = nanoseconds();
+        start_ns = nanosecondsWithBound(start_ns);
         last_ns = start_ns;
         is_running = true;
     }
 
     void stop()
     {
-        stop_ns = nanoseconds();
+        stop_ns = nanosecondsWithBound(start_ns);
         is_running = false;
     }
 
@@ -82,14 +82,16 @@ class Stopwatch
         last_ns = 0;
         is_running = false;
     }
+
     void restart() { start(); }
-    UInt64 elapsed() const { return is_running ? nanoseconds() - start_ns : stop_ns - start_ns; }
+
+    UInt64 elapsed() const { return is_running ? nanosecondsWithBound(start_ns) - start_ns : stop_ns - start_ns; }
     UInt64 elapsedMilliseconds() const { return elapsed() / 1000000UL; }
     double elapsedSeconds() const { return static_cast<double>(elapsed()) / 1000000000ULL; }
 
     UInt64 elapsedFromLastTime()
     {
-        const auto now_ns = nanoseconds();
+        const auto now_ns = nanosecondsWithBound(last_ns);
         if (is_running)
         {
             auto rc = now_ns - last_ns;
@@ -100,7 +102,7 @@ class Stopwatch
         {
             return stop_ns - last_ns;
         }
-    };
+    }
 
     UInt64 elapsedMillisecondsFromLastTime() { return elapsedFromLastTime() / 1000000UL; }
     double elapsedSecondsFromLastTime() { return static_cast<double>(elapsedFromLastTime()) / 1000000000ULL; }
@@ -109,10 +111,12 @@ class Stopwatch
     UInt64 start_ns = 0;
     UInt64 stop_ns = 0;
     UInt64 last_ns = 0;
-    clockid_t clock_type;
+    const clockid_t clock_type;
     bool is_running = false;
 
-    UInt64 nanoseconds() const { return clock_gettime_ns_adjusted(start_ns, clock_type); }
+    // Get current nano seconds, ensuring the return value is not
+    // less than `lower_bound`.
+    UInt64 nanosecondsWithBound(UInt64 lower_bound) const { return clock_gettime_ns_adjusted(lower_bound, clock_type); }
 };
 
 

From be4fc0d597ff75ded5bfe36a3b0a037f94c295df Mon Sep 17 00:00:00 2001
From: JaySon <tshent@qq.com>
Date: Thu, 9 Nov 2023 09:54:01 +0800
Subject: [PATCH 2/2] Fix compile error

---
 dbms/src/Common/Stopwatch.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/dbms/src/Common/Stopwatch.h b/dbms/src/Common/Stopwatch.h
index 28763478cf9..af972610810 100644
--- a/dbms/src/Common/Stopwatch.h
+++ b/dbms/src/Common/Stopwatch.h
@@ -111,7 +111,7 @@ class Stopwatch
     UInt64 start_ns = 0;
     UInt64 stop_ns = 0;
     UInt64 last_ns = 0;
-    const clockid_t clock_type;
+    clockid_t clock_type;
     bool is_running = false;
 
     // Get current nano seconds, ensuring the return value is not