Making use of GetSystemTimePreciseAsFileTime dynamic to not

break compatibility with Windows 7. The issue with rotated logs
was fixed other way.

db/auto_roll_logger.cc

@@ -32,8 +32,17 @@ Status AutoRollLogger::ResetLogger() {
 }
 
 void AutoRollLogger::RollLogFile() {
-  std::string old_fname = OldInfoLogFileName(
-      dbname_, env_->NowMicros(), db_absolute_path_, db_log_dir_);
+  uint64_t now = env_->NowMicros();
+  std::string old_fname;
+  // Try to check target name only 10 times at most
+  for (int i = 0; i < 10; i++) {
+    old_fname = OldInfoLogFileName(
+      dbname_, now, db_absolute_path_, db_log_dir_);
+    if (!env_->FileExists(old_fname).ok()) {
+      break;
+    }
+    now++;
+  };
   env_->RenameFile(log_fname_, old_fname);
 }
 

port/win/env_win.cc

@@ -1138,6 +1138,8 @@ void WinthreadCall(const char* label, std::error_code result) {
 }
 }
 
+typedef VOID(WINAPI * FnGetSystemTimePreciseAsFileTime)(LPFILETIME);
+
 class WinEnv : public Env {
  public:
   WinEnv();
@@ -1676,25 +1678,29 @@ class WinEnv : public Env {
   }
 
   virtual uint64_t NowMicros() override {
-    // all std::chrono clocks on windows proved to return
-    // values that may repeat that is not good enough for some uses.
-    const int64_t c_UnixEpochStartTicks = 116444736000000000i64;
-    const int64_t c_FtToMicroSec = 10;
-
-    // This interface needs to return system time and not
-    // just any microseconds because it is often used as an argument
-    // to TimedWait() on condition variable
-    FILETIME ftSystemTime;
-    GetSystemTimePreciseAsFileTime(&ftSystemTime);
-
-    LARGE_INTEGER li;
-    li.LowPart = ftSystemTime.dwLowDateTime;
-    li.HighPart = ftSystemTime.dwHighDateTime;
-    // Subtract unix epoch start
-    li.QuadPart -= c_UnixEpochStartTicks;
-    // Convert to microsecs
-    li.QuadPart /= c_FtToMicroSec;
-    return li.QuadPart;
+    if (GetSystemTimePreciseAsFileTime_ != NULL) {
+      // all std::chrono clocks on windows proved to return
+      // values that may repeat that is not good enough for some uses.
+      const int64_t c_UnixEpochStartTicks = 116444736000000000i64;
+      const int64_t c_FtToMicroSec = 10;
+
+      // This interface needs to return system time and not
+      // just any microseconds because it is often used as an argument
+      // to TimedWait() on condition variable
+      FILETIME ftSystemTime;
+      GetSystemTimePreciseAsFileTime_(&ftSystemTime);
+
+      LARGE_INTEGER li;
+      li.LowPart = ftSystemTime.dwLowDateTime;
+      li.HighPart = ftSystemTime.dwHighDateTime;
+      // Subtract unix epoch start
+      li.QuadPart -= c_UnixEpochStartTicks;
+      // Convert to microsecs
+      li.QuadPart /= c_FtToMicroSec;
+      return li.QuadPart;
+    }
+    using namespace std::chrono;
+    return duration_cast<microseconds>(system_clock::now().time_since_epoch()).count();
   }
 
   virtual uint64_t NowNanos() override {
@@ -2104,15 +2110,30 @@ class WinEnv : public Env {
   std::vector<ThreadPool> thread_pools_;
   mutable std::mutex mu_;
   std::vector<std::thread> threads_to_join_;
+  static FnGetSystemTimePreciseAsFileTime GetSystemTimePreciseAsFileTime_;
+  static bool GetSystemTimePreciseAsFileTimeInitialized_;
 };
 
+FnGetSystemTimePreciseAsFileTime WinEnv::GetSystemTimePreciseAsFileTime_ = NULL;
+bool WinEnv::GetSystemTimePreciseAsFileTimeInitialized_ = false;
+
 WinEnv::WinEnv()
     : checkedDiskForMmap_(false),
       forceMmapOff(false),
       page_size_(4 * 1012),
       allocation_granularity_(page_size_),
       perf_counter_frequency_(0),
       thread_pools_(Priority::TOTAL) {
+
+  if (!GetSystemTimePreciseAsFileTimeInitialized_) {
+    HMODULE module = GetModuleHandle("kernel32.dll");
+    if (module != NULL) {
+      GetSystemTimePreciseAsFileTime_ = (FnGetSystemTimePreciseAsFileTime)GetProcAddress(
+        module, "GetSystemTimePreciseAsFileTime");
+    }
+    GetSystemTimePreciseAsFileTimeInitialized_ = true;
+  }
+
   SYSTEM_INFO sinfo;
   GetSystemInfo(&sinfo);