Commit 8ca3b53a authored by sasha@mysql.sashanet.com's avatar sasha@mysql.sashanet.com
Browse files

fixed bug in Item_func_div::val_int() that broke all functions that 

do val_int() on their arguments before starting the computation. 
Similar fixes are need for +-* and probably several other but I want
to make sure Monty is fine with my fix approach before changing a lot
of code. 

Amazingly,
this bug is not as critical as you would expect since very few functions do val_int()
on their arguments ( from_unixtime(), sec_to_time()), and those not
very frequently perform a computation on their floating point arguments.
which is probably why no one has yet reported this bug. Another 
possibility is that the result is usually wrong by no more than 5%,
which makes it hard to catch it. I found it when trying to compute mile
splits for 30:47 10K - it told me 5:07, and I knew it was wrong because
5:00 mile gives you 31:08. However, if I had not run as many 10K races,
I would have easily believed that 30:47 10K is a 5:07 mile pace and 
would not have noticed the bug.
parent c68d7caa

mysql-test/r/func_time.result

+2 −2
Original line number Diff line number Diff line
@@ -6,8 +6,8 @@ now()-now() weekday(curdate())-weekday(now()) unix_timestamp()-unix_timestamp(no 
0	0	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

sec_to_time(9001)	sec_to_time(9001)+0	time_to_sec("15:12:22")

02:30:01	23001	54742

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

now()-curdate()*1000000-curtime()

0

strcmp(current_timestamp(),concat(current_date()," ",current_time()))

mysql-test/t/func_time.test

+2 −1
Original line number Diff line number Diff line
@@ -7,7 +7,8 @@ select from_days(to_days("960101")),to_days(960201)-to_days("19960101"),to_days( 
select period_add("9602",-12),period_diff(199505,"9404") ;

select now()-now(),weekday(curdate())-weekday(now()),unix_timestamp()-unix_timestamp(now());

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;

select sec_to_time(9001),sec_to_time(9001)+0,time_to_sec("15:12:22");

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);

select now()-curdate()*1000000-curtime();

select strcmp(current_timestamp(),concat(current_date()," ",current_time()));

select date_format("1997-01-02 03:04:05", "%M %W %D %Y %y %m %d %h %i %s %w");

sql/item_func.cc

+8 −5
Original line number Diff line number Diff line
@@ -309,11 +309,14 @@ double Item_func_div::val() 


longlong Item_func_div::val_int()

{

  longlong value=args[0]->val_int();

  longlong val2=args[1]->val_int();

  if ((null_value= val2 == 0 || args[0]->null_value || args[1]->null_value))

    return 0;

  return value/val2;

  // the integer result of division of two arguments needs to be computed

  // as a type-cast division of val(), not as diviion of val_int() of each

  // argument. For example, val_int(41.5/3.4) = val_int(12.206) = 12, but

  // if you do val_int(41.5)/val_int(3.4), as in the old code, we get 42/3=

  // 14, which is wrong. This would break sec_to_time(a/b),

  // from_unixtime(a/b), and

  // all functions that do val_int() on their arguments

  return (longlong)val();

}



void Item_func_div::fix_length_and_dec()