revert a suggested "optimization" that introduced a bug

compilation error in mysys/my_getsystime.c fixed
some redundant code removed
sec_to_time, time_to_sec, from_unixtime, unix_timestamp, @@timestamp now
  use decimal, not double for numbers with a fractional part.
purge_master_logs_before_date() fixed
many bugs in corner cases fixed

mysys/my_getsystime.c:
  compilation failure fixed
sql/sql_parse.cc:
  don't cut corners. it backfires.

1 files changed, 16 insertions, 14 deletions

diff --git a/sql/item_func.cc b/sql/item_func.cc
index 5a8e8a4defd..b3eb991b747 100644
--- a/sql/item_func.cc
+++ b/sql/item_func.cc
@@ -664,8 +664,8 @@ void Item_num_op::find_num_type(void)
   DBUG_ENTER("Item_num_op::find_num_type");
   DBUG_PRINT("info", ("name %s", func_name()));
   DBUG_ASSERT(arg_count == 2);
-  Item_result r0= args[0]->result_type();
-  Item_result r1= args[1]->result_type();
+  Item_result r0= args[0]->cast_to_int_type();
+  Item_result r1= args[1]->cast_to_int_type();
 
   if (r0 == REAL_RESULT || r1 == REAL_RESULT ||
       r0 == STRING_RESULT || r1 ==STRING_RESULT)
@@ -674,7 +674,8 @@ void Item_num_op::find_num_type(void)
     max_length= float_length(decimals);
     hybrid_type= REAL_RESULT;
   }
-  else if (r0 == DECIMAL_RESULT || r1 == DECIMAL_RESULT)
+  else if (r0 == DECIMAL_RESULT || r1 == DECIMAL_RESULT ||
+           r0 == TIME_RESULT || r1 == TIME_RESULT)
   {
     hybrid_type= DECIMAL_RESULT;
     result_precision();
@@ -705,7 +706,7 @@ void Item_func_num1::find_num_type()
 {
   DBUG_ENTER("Item_func_num1::find_num_type");
   DBUG_PRINT("info", ("name %s", func_name()));
-  switch (hybrid_type= args[0]->result_type()) {
+  switch (hybrid_type= args[0]->cast_to_int_type()) {
   case INT_RESULT:
     unsigned_flag= args[0]->unsigned_flag;
     break;
@@ -714,9 +715,10 @@ void Item_func_num1::find_num_type()
     hybrid_type= REAL_RESULT;
     max_length= float_length(decimals);
     break;
+  case TIME_RESULT:
+    hybrid_type= DECIMAL_RESULT;
   case DECIMAL_RESULT:
     break;
-  case TIME_RESULT:
   case ROW_RESULT:
     DBUG_ASSERT(0);
   }
@@ -1815,7 +1817,7 @@ void Item_func_int_val::find_num_type()
 {
   DBUG_ENTER("Item_func_int_val::find_num_type");
   DBUG_PRINT("info", ("name %s", func_name()));
-  switch(hybrid_type= args[0]->result_type())
+  switch(hybrid_type= args[0]->cast_to_int_type())
   {
   case STRING_RESULT:
   case REAL_RESULT:
@@ -1823,6 +1825,7 @@ void Item_func_int_val::find_num_type()
     max_length= float_length(decimals);
     break;
   case INT_RESULT:
+  case TIME_RESULT:
   case DECIMAL_RESULT:
     /*
       -2 because in most high position can't be used any digit for longlong
@@ -1840,7 +1843,6 @@ void Item_func_int_val::find_num_type()
     }
     break;
   case ROW_RESULT:
-  case TIME_RESULT:
     DBUG_ASSERT(0);
   }
   DBUG_PRINT("info", ("Type: %s",
@@ -2240,16 +2242,9 @@ void Item_func_min_max::fix_length_and_dec()
     if (args[i]->maybe_null)
       maybe_null= 1;
     cmp_type= item_cmp_type(cmp_type,args[i]->result_type());
-    if (args[i]->cmp_type() == TIME_RESULT)
-    {
-      if (!compare_as_dates || args[i]->field_type() == MYSQL_TYPE_DATETIME)
-        compare_as_dates= args[i];
-    }
   }
   if (cmp_type == STRING_RESULT)
-  {
     agg_arg_charsets(collation, args, arg_count, MY_COLL_CMP_CONV, 1);
-  }
   else if ((cmp_type == DECIMAL_RESULT) || (cmp_type == INT_RESULT))
     max_length= my_decimal_precision_to_length_no_truncation(max_int_part +
                                                              decimals, decimals,
@@ -2257,8 +2252,15 @@ void Item_func_min_max::fix_length_and_dec()
   else if (cmp_type == REAL_RESULT)
     max_length= float_length(decimals);
 
+  compare_as_dates= find_date_time_item(args, arg_count, 0);
   if (compare_as_dates)
+  {
     cached_field_type= compare_as_dates->field_type();
+    if (mysql_type_to_time_type(cached_field_type) == MYSQL_TIMESTAMP_DATE)
+      decimals= 0;
+    else
+      set_if_smaller(decimals, TIME_SECOND_PART_DIGITS);
+  }
   else
     cached_field_type= agg_field_type(args, arg_count);
 }