From e4e310501447bf0cdea238b984044f7762126bd0 Mon Sep 17 00:00:00 2001
From: bharatnc <bharatnc@gmail.com>
Date: Mon, 14 Sep 2020 19:37:44 -0700
Subject: [PATCH] Construct query_start_time(_microseconds) from same timespec

---
 src/Interpreters/ThreadStatusExt.cpp | 11 ++++++++---
 src/Interpreters/executeQuery.cpp    | 11 +++++++++--
 2 files changed, 17 insertions(+), 5 deletions(-)

diff --git a/src/Interpreters/ThreadStatusExt.cpp b/src/Interpreters/ThreadStatusExt.cpp
index 34efdda9097..5766472156a 100644
--- a/src/Interpreters/ThreadStatusExt.cpp
+++ b/src/Interpreters/ThreadStatusExt.cpp
@@ -146,9 +146,14 @@ void ThreadStatus::initPerformanceCounters()
     memory_tracker.resetCounters();
     memory_tracker.setDescription("(for thread)");
 
-    query_start_time_nanoseconds = getCurrentTimeNanoseconds();
-    query_start_time = time(nullptr);
-    query_start_time_microseconds = getCurrentTimeMicroseconds();
+    // query_start_time_{microseconds, nanoseconds} are all constructed from the same timespec
+    // to ensure that they are all atelast equal upto the precision of a second.
+    struct timespec ts;
+    clock_gettime(CLOCK_MONOTONIC, &ts);
+
+    query_start_time_nanoseconds = UInt64(ts.tv_sec * 1000000000LL + ts.tv_nsec);
+    query_start_time = ts.tv_sec;
+    query_start_time_microseconds = UInt64((ts.tv_sec * 1000000LL) + (ts.tv_nsec / 1000));
     ++queries_started;
 
     *last_rusage = RUsageCounters::current(query_start_time_nanoseconds);
diff --git a/src/Interpreters/executeQuery.cpp b/src/Interpreters/executeQuery.cpp
index 478eed65ae1..be18fb20d29 100644
--- a/src/Interpreters/executeQuery.cpp
+++ b/src/Interpreters/executeQuery.cpp
@@ -196,6 +196,8 @@ static void onExceptionBeforeStart(const String & query_for_logging, Context & c
 
     elem.type = QueryLogElementType::EXCEPTION_BEFORE_START;
 
+    // the assumption here is that the callers of onExceptionBeforeStart construct both params current_time and the current_time_microseconds
+    // from the same timespec so that both of the times are equal upto the precision of a second.
     elem.event_time = current_time;
     elem.query_start_time = current_time;
     elem.query_start_time_microseconds = current_time_microseconds;
@@ -251,8 +253,13 @@ static std::tuple<ASTPtr, BlockIO> executeQueryImpl(
     bool has_query_tail,
     ReadBuffer * istr)
 {
-    time_t current_time = time(nullptr);
-    UInt64 current_time_microseconds = getCurrentTimeMicroseconds();
+    // current_time and current_time_microseconds are both constructed from the same timespec
+    // to ensure that both the times are equal upto the precision of a second.
+    struct timespec ts;
+    clock_gettime(CLOCK_MONOTONIC, &ts);
+
+    time_t current_time = ts.tv_sec;
+    UInt64 current_time_microseconds = UInt64((ts.tv_sec * 1000000LL) + (ts.tv_nsec / 1000));
 
     /// If we already executing query and it requires to execute internal query, than
     /// don't replace thread context with given (it can be temporary). Otherwise, attach context to thread.