bzr commit into mysql-6.0 branch (gshchepa:2706) Bug#35848

[Gleb Shchepa]

#At file:///work/bzr/mysql-6.0-bugteam/

 2706 Gleb Shchepa	2008-07-11
      rollback of bug #35848 patch in 6.0: this code have to be ported
      into ./mysys/my_uuid.c
modified:
  mysql-test/r/func_misc.result
  mysql-test/t/func_misc.test
  sql/item_strfunc.cc

=== modified file 'mysql-test/r/func_misc.result'
--- a/mysql-test/r/func_misc.result	2008-07-10 03:29:11 +0000
+++ b/mysql-test/r/func_misc.result	2008-07-10 23:18:00 +0000
@@ -310,20 +310,6 @@ drop table t1;
 SELECT NAME_CONST('var', 'value') COLLATE latin1_general_cs;
 NAME_CONST('var', 'value') COLLATE latin1_general_cs
 value
-select @@session.time_zone into @save_tz;
-set @@session.time_zone='UTC';
-select uuid() into @my_uuid;
-select mid(@my_uuid,15,1);
-mid(@my_uuid,15,1)
-1
-select 24 * 60 * 60 * 1000 * 1000 * 10 into @my_uuid_one_day;
-select concat('0',mid(@my_uuid,16,3),mid(@my_uuid,10,4),left(@my_uuid,8)) into @my_uuidate;
-select floor(conv(@my_uuidate,16,10)/@my_uuid_one_day) into @my_uuid_date;
-select 141427 + datediff(curdate(),'1970-01-01') into @my_uuid_synthetic;
-select @my_uuid_date - @my_uuid_synthetic;
-@my_uuid_date - @my_uuid_synthetic
-0
-set @@session.time_zone=@save_tz;
 End of 5.0 tests
 select connection_id() > 0;
 connection_id() > 0

=== modified file 'mysql-test/t/func_misc.test'
--- a/mysql-test/t/func_misc.test	2008-07-10 03:29:11 +0000
+++ b/mysql-test/t/func_misc.test	2008-07-10 23:18:00 +0000
@@ -426,25 +426,6 @@ drop table t1;
 #
 SELECT NAME_CONST('var', 'value') COLLATE latin1_general_cs;
 
-#
-# Bug #35848: UUID() returns UUIDs with the wrong time
-#
-select @@session.time_zone into @save_tz;
-
-# make sure all times are UTC so the DayNr won't differ
-set @@session.time_zone='UTC';
-select uuid() into @my_uuid;
-# if version nibble isn't 1, the following calculations will be rubbish
-select mid(@my_uuid,15,1);
-select 24 * 60 * 60 * 1000 * 1000 * 10 into @my_uuid_one_day;
-select concat('0',mid(@my_uuid,16,3),mid(@my_uuid,10,4),left(@my_uuid,8)) into @my_uuidate;
-select floor(conv(@my_uuidate,16,10)/@my_uuid_one_day) into @my_uuid_date;
-select 141427 + datediff(curdate(),'1970-01-01') into @my_uuid_synthetic;
-# these should be identical; date part of UUID should be current date
-select @my_uuid_date - @my_uuid_synthetic;
-
-set @@session.time_zone=@save_tz;
-
 --echo End of 5.0 tests
 
 #

=== modified file 'sql/item_strfunc.cc'
--- a/sql/item_strfunc.cc	2008-07-10 03:29:11 +0000
+++ b/sql/item_strfunc.cc	2008-07-10 23:18:00 +0000
@@ -3557,8 +3557,7 @@ static char clock_seq_and_node_str[]="-0
   number of 100-nanosecond intervals between
   1582-10-15 00:00:00.00 and 1970-01-01 00:00:00.00.
 */
-#define UUID_TIME_OFFSET ((ulonglong) 141427 * 24 * 60 * 60 * \
-                          1000 * 1000 * 10)
+#define UUID_TIME_OFFSET ((ulonglong) 141427 * 24 * 60 * 60 * 1000 * 10 )
 
 #define UUID_VERSION      0x1000
 #define UUID_VARIANT      0x8000
@@ -3617,64 +3616,24 @@ String *Item_func_uuid::val_str(String *
     set_clock_seq_str();
   }
 
-  ulonglong tv= my_getsystime() + UUID_TIME_OFFSET + nanoseq;
-
-  if (likely(tv > uuid_time))
+  ulonglong tv=my_getsystime() + UUID_TIME_OFFSET + nanoseq;
+  if (unlikely(tv < uuid_time))
+    set_clock_seq_str();
+  else if (unlikely(tv == uuid_time))
   {
-    /*
-      Current time is ahead of last timestamp, as it should be.
-      If we "borrowed time", give it back, just as long as we
-      stay ahead of the previous timestamp.
-    */
-    if (nanoseq)
-    {
-      DBUG_ASSERT((tv > uuid_time) && (nanoseq > 0));
-      /*
-        -1 so we won't make tv= uuid_time for nanoseq >= (tv - uuid_time)
-      */
-      long delta= min(nanoseq, tv - uuid_time -1);
-      tv-= delta;
-      nanoseq-= delta;
-    }
+    /* special protection from low-res system clocks */
+    nanoseq++;
+    tv++;
   }
   else
   {
-    if (unlikely(tv == uuid_time))
-    {
-      /*
-        For low-res system clocks. If several requests for UUIDs
-        end up on the same tick, we add a nano-second to make them
-        different.
-        ( current_timestamp + nanoseq * calls_in_this_period )
-        may end up > next_timestamp; this is OK. Nonetheless, we'll
-        try to unwind nanoseq when we get a chance to.
-        If nanoseq overflows, we'll start over with a new numberspace
-        (so the if() below is needed so we can avoid the ++tv and thus
-        match the follow-up if() if nanoseq overflows!).
-      */
-      if (likely(++nanoseq))
-        ++tv;
-    }
-
-    if (unlikely(tv <= uuid_time))
+    if (nanoseq)
     {
-      /*
-        If the admin changes the system clock (or due to Daylight
-        Saving Time), the system clock may be turned *back* so we
-        go through a period once more for which we already gave out
-        UUIDs.  To avoid duplicate UUIDs despite potentially identical
-        times, we make a new random component.
-        We also come here if the nanoseq "borrowing" overflows.
-        In either case, we throw away any nanoseq borrowing since it's
-        irrelevant in the new numberspace.
-      */
-      set_clock_seq_str();
-      tv= my_getsystime() + UUID_TIME_OFFSET;
-      nanoseq= 0;
-      DBUG_PRINT("uuid",("making new numberspace"));
+      tv-=nanoseq;
+      nanoseq=0;
     }
+    DBUG_ASSERT(tv > uuid_time);
   }
-
   uuid_time=tv;
   pthread_mutex_unlock(&LOCK_uuid_generator);