Fix for bug #16546: DATETIME+0 not always coerced the same way

mysql-test/r/func_time.result:
  Fix for bug #16546: DATETIME+0 not always coerced the same way
    - test case
mysql-test/t/func_time.test:
  Fix for bug #16546: DATETIME+0 not always coerced the same way
    - test case
sql/item_timefunc.cc:
  Fix for bug #16546: DATETIME+0 not always coerced the same way
    - set decimals to DATETIME_DEC
sql/item_timefunc.h:
  Fix for bug #16546: DATETIME+0 not always coerced the same way
    - set decimals to DATETIME_DEC

mysql-test/r/func_time.result

@@ -7,20 +7,20 @@ period_add("9602",-12)	period_diff(199505,"9404")
 199502	13
 select now()-now(),weekday(curdate())-weekday(now()),unix_timestamp()-unix_timestamp(now());
 now()-now()	weekday(curdate())-weekday(now())	unix_timestamp()-unix_timestamp(now())
-0	0	0
+0.000000	0	0
 select from_unixtime(unix_timestamp("1994-03-02 10:11:12")),from_unixtime(unix_timestamp("1994-03-02 10:11:12"),"%Y-%m-%d %h:%i:%s"),from_unixtime(unix_timestamp("1994-03-02 10:11:12"))+0;
 from_unixtime(unix_timestamp("1994-03-02 10:11:12"))	from_unixtime(unix_timestamp("1994-03-02 10:11:12"),"%Y-%m-%d %h:%i:%s")	from_unixtime(unix_timestamp("1994-03-02 10:11:12"))+0
-1994-03-02 10:11:12	1994-03-02 10:11:12	19940302101112
+1994-03-02 10:11:12	1994-03-02 10:11:12	19940302101112.000000
 select sec_to_time(9001),sec_to_time(9001)+0,time_to_sec("15:12:22"),
 sec_to_time(time_to_sec("0:30:47")/6.21);
 sec_to_time(9001)	sec_to_time(9001)+0	time_to_sec("15:12:22")	sec_to_time(time_to_sec("0:30:47")/6.21)
-02:30:01	23001	54742	00:04:57
+02:30:01	23001.000000	54742	00:04:57
 select sec_to_time(time_to_sec('-838:59:59'));
 sec_to_time(time_to_sec('-838:59:59'))
 -838:59:59
 select now()-curdate()*1000000-curtime();
 now()-curdate()*1000000-curtime()
-0
+0.000000
 select strcmp(current_timestamp(),concat(current_date()," ",current_time()));
 strcmp(current_timestamp(),concat(current_date()," ",current_time()))
 0
@@ -626,3 +626,7 @@ last_day('2005-01-00')
 NULL
 Warnings:
 Warning	1292	Truncated incorrect datetime value: '2005-01-00'
+select now() - now() + 0, curtime() - curtime() + 0, 
+sec_to_time(1) + 0, from_unixtime(1) + 0;
+now() - now() + 0	curtime() - curtime() + 0	sec_to_time(1) + 0	from_unixtime(1) + 0
+0.000000	0.000000	1.000000	19700101030001.000000

mysql-test/t/func_time.test

@@ -315,4 +315,12 @@ select last_day('2005-00-00');
 select last_day('2005-00-01');
 select last_day('2005-01-00');
 
+#
+# Bug #16546
+# 
+
+select now() - now() + 0, curtime() - curtime() + 0, 
+       sec_to_time(1) + 0, from_unixtime(1) + 0;
+
+
 # End of 4.1 tests

sql/item_timefunc.cc

@@ -1372,7 +1372,7 @@ void Item_func_curtime::fix_length_and_dec()
 {
   TIME ltime;
 
-  decimals=0;
+  decimals= DATETIME_DEC;
   collation.set(&my_charset_bin);
   store_now_in_TIME(&ltime);
   value= TIME_to_ulonglong_time(&ltime);
@@ -1419,7 +1419,7 @@ String *Item_func_now::val_str(String *str)
 
 void Item_func_now::fix_length_and_dec()
 {
-  decimals=0;
+  decimals= DATETIME_DEC;
   collation.set(&my_charset_bin);
 
   store_now_in_TIME(&ltime);
@@ -1680,7 +1680,7 @@ void Item_func_from_unixtime::fix_length_and_dec()
 { 
   thd= current_thd;
   collation.set(&my_charset_bin);
-  decimals=0;
+  decimals= DATETIME_DEC;
   max_length=MAX_DATETIME_WIDTH*MY_CHARSET_BIN_MB_MAXLEN;
   maybe_null= 1;
   thd->time_zone_used= 1;

sql/item_timefunc.h

@@ -580,6 +580,7 @@ class Item_func_sec_to_time :public Item_str_func
   { 
     collation.set(&my_charset_bin);
     maybe_null=1;
+    decimals= DATETIME_DEC;
     max_length=MAX_TIME_WIDTH*MY_CHARSET_BIN_MB_MAXLEN;
   }
   enum_field_types field_type() const { return MYSQL_TYPE_TIME; }