From 0b8144a4728e357965b2e3027535148870f0d0fd Mon Sep 17 00:00:00 2001
From: Daniel Black <grooverdan@users.sourceforge.net>
Date: Fri, 23 Oct 2015 23:23:36 +1100
Subject: [PATCH] MDEV-8981: Analyze stmt - cycles can overflow

A 64bit counter can overflow within the time of a query
so lets take it that the measurement is the small value
rather than an order 1e12 millisecond query.

tested with:

int main()
{
  ulonglong start = ULONGLONG_MAX - 30;
  ulonglong end = 600;
  ulonglong cycles = 10000;

  cycles += end - start;
  if (unlikely(end < start))
     cycles += ULONGLONG_MAX;

  printf("cycles %llu\n", cycles);
}
---
 sql/sql_analyze_stmt.h | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/sql/sql_analyze_stmt.h b/sql/sql_analyze_stmt.h
index bf800fd1df6..d7634bdfb85 100644
--- a/sql/sql_analyze_stmt.h
+++ b/sql/sql_analyze_stmt.h
@@ -47,6 +47,14 @@ protected:
   ulonglong count;
   ulonglong cycles;
   ulonglong last_start;
+
+  void cycles_stop_tracking()
+  {
+    ulonglong end= my_timer_cycles();
+    cycles += end - last_start;
+    if (unlikely(end < last_start))
+      cycles += ULONGLONG_MAX;
+  }
 public:
   Exec_time_tracker() : count(0), cycles(0) {}
   
@@ -59,7 +67,7 @@ public:
   void stop_tracking()
   {
     count++;
-    cycles += my_timer_cycles()- last_start;
+    cycles_stop_tracking();
   }
 
   // interface for getting the time
@@ -93,7 +101,7 @@ public:
   */
   void stop_tracking()
   {
-    cycles += my_timer_cycles()- last_start;
+    cycles_stop_tracking();
   }
 };