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Bug#37662 nested if() inside sum() is parsed in exponential time

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min() and max() functions are implemented in MySQL as macros.
This means that max(a,b) is expanded to: ((a) > (b) ? (a) : (b))
Note how 'a' is quoted two times.
Now imagine 'a' is a recursive function call that's several 10s of levels deep.
And the recursive function does max() with a function arg as well to dive into
recursion.
This means that simple function call can take most of the clock time.
Identified and fixed several such calls to max()/min() : including the IF() 
sql function implementation.

mysql-test/r/func_if.result:
  Bug#37662 test case
mysql-test/t/func_if.test:
  Bug#37662 test case
sql/item.cc:
  Bug#37662 don't call expensive functions as arguments to min/max
sql/item_cmpfunc.cc:
  Bug#37662 don't call expensive functions as arguments to min/max
sql/item_func.cc:
  Bug#37662 don't call expensive functions as arguments to min/max
This commit is contained in:
Georgi Kodinov 2008-07-30 14:07:37 +03:00
parent 7f615b2c14
commit ae4a35fd5c
5 changed files with 113 additions and 15 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

46
mysql-test/r/func_if.result
View File

@ -131,3 +131,49 @@ drop table t1;
select if(0, 18446744073709551610, 18446744073709551610);
if(0, 18446744073709551610, 18446744073709551610)
18446744073709551610
CREATE TABLE t1(a DECIMAL(10,3));
SELECT t1.a,
IF((ROUND(t1.a,2)=1), 2,
IF((ROUND(t1.a,2)=1), 2,
IF((ROUND(t1.a,2)=1), 2,
IF((ROUND(t1.a,2)=1), 2,
IF((ROUND(t1.a,2)=1), 2,
IF((ROUND(t1.a,2)=1), 2,
IF((ROUND(t1.a,2)=1), 2,
IF((ROUND(t1.a,2)=1), 2,
IF((ROUND(t1.a,2)=1), 2,
IF((ROUND(t1.a,2)=1), 2,
IF((ROUND(t1.a,2)=1), 2,
IF((ROUND(t1.a,2)=1), 2,
IF((ROUND(t1.a,2)=1), 2,
IF((ROUND(t1.a,2)=1), 2,
IF((ROUND(t1.a,2)=1), 2,
IF((ROUND(t1.a,2)=1), 2,
IF((ROUND(t1.a,2)=1), 2,
IF((ROUND(t1.a,2)=1), 2,
IF((ROUND(t1.a,2)=1), 2,
IF((ROUND(t1.a,2)=1), 2,
IF((ROUND(t1.a,2)=1), 2,
IF((ROUND(t1.a,2)=1), 2,
IF((ROUND(t1.a,2)=1), 2,
IF((ROUND(t1.a,2)=1), 2,
IF((ROUND(t1.a,2)=1), 2,
IF((ROUND(t1.a,2)=1), 2,
IF((ROUND(t1.a,2)=1), 2,
IF((ROUND(t1.a,2)=1), 2,
IF((ROUND(t1.a,2)=1), 2,
IF((ROUND(t1.a,2)=1), 2,0)))))))))))))))))))))))))))))) + 1
FROM t1;
a IF((ROUND(t1.a,2)=1), 2,
IF((ROUND(t1.a,2)=1), 2,
IF((ROUND(t1.a,2)=1), 2,
IF((ROUND(t1.a,2)=1), 2,
IF((ROUND(t1.a,2)=1), 2,
IF((ROUND(t1.a,2)=1), 2,
IF((ROUND(t1.a,2)=1), 2,
IF((ROUND(t1.a,2)=1), 2,
IF((ROUND(t1.a,2)=1), 2,
IF((ROUND(t1.a,2)=1), 2,
IF((R
DROP TABLE t1;
End of 5.0 tests

43
mysql-test/t/func_if.test
View File

@ -108,3 +108,46 @@ drop table t1;
select if(0, 18446744073709551610, 18446744073709551610);
#
# Bug #37662: nested if() inside sum() is parsed in exponential time
#
CREATE TABLE t1(a DECIMAL(10,3));
# check : should be fast. more than few secs means failure.
SELECT t1.a,
IF((ROUND(t1.a,2)=1), 2,
IF((ROUND(t1.a,2)=1), 2,
IF((ROUND(t1.a,2)=1), 2,
IF((ROUND(t1.a,2)=1), 2,
IF((ROUND(t1.a,2)=1), 2,
IF((ROUND(t1.a,2)=1), 2,
IF((ROUND(t1.a,2)=1), 2,
IF((ROUND(t1.a,2)=1), 2,
IF((ROUND(t1.a,2)=1), 2,
IF((ROUND(t1.a,2)=1), 2,
IF((ROUND(t1.a,2)=1), 2,
IF((ROUND(t1.a,2)=1), 2,
IF((ROUND(t1.a,2)=1), 2,
IF((ROUND(t1.a,2)=1), 2,
IF((ROUND(t1.a,2)=1), 2,
IF((ROUND(t1.a,2)=1), 2,
IF((ROUND(t1.a,2)=1), 2,
IF((ROUND(t1.a,2)=1), 2,
IF((ROUND(t1.a,2)=1), 2,
IF((ROUND(t1.a,2)=1), 2,
IF((ROUND(t1.a,2)=1), 2,
IF((ROUND(t1.a,2)=1), 2,
IF((ROUND(t1.a,2)=1), 2,
IF((ROUND(t1.a,2)=1), 2,
IF((ROUND(t1.a,2)=1), 2,
IF((ROUND(t1.a,2)=1), 2,
IF((ROUND(t1.a,2)=1), 2,
IF((ROUND(t1.a,2)=1), 2,
IF((ROUND(t1.a,2)=1), 2,
IF((ROUND(t1.a,2)=1), 2,0)))))))))))))))))))))))))))))) + 1
FROM t1;
DROP TABLE t1;
--echo End of 5.0 tests

12
sql/item.cc
View File

@ -429,8 +429,11 @@ uint Item::decimal_precision() const
Item_result restype= result_type();
if ((restype == DECIMAL_RESULT) || (restype == INT_RESULT))
return min(my_decimal_length_to_precision(max_length, decimals, unsigned_flag),
DECIMAL_MAX_PRECISION);
{
uint prec=
my_decimal_length_to_precision(max_length, decimals, unsigned_flag);
return min(prec, DECIMAL_MAX_PRECISION);
}
return min(max_length, DECIMAL_MAX_PRECISION);
}
@ -6838,8 +6841,9 @@ bool Item_type_holder::join_types(THD *thd, Item *item)
if (Field::result_merge_type(fld_type) == DECIMAL_RESULT)
{
decimals= min(max(decimals, item->decimals), DECIMAL_MAX_SCALE);
int precision= min(max(prev_decimal_int_part, item->decimal_int_part())
+ decimals, DECIMAL_MAX_PRECISION);
int item_int_part= item->decimal_int_part();
int item_prec = max(prev_decimal_int_part, item_int_part) + decimals;
int precision= min(item_prec, DECIMAL_MAX_PRECISION);
unsigned_flag&= item->unsigned_flag;
max_length= my_decimal_precision_to_length(precision, decimals,
unsigned_flag);

12
sql/item_cmpfunc.cc
View File

@ -2098,8 +2098,11 @@ Item_func_ifnull::fix_length_and_dec()
uint Item_func_ifnull::decimal_precision() const
{
int max_int_part=max(args[0]->decimal_int_part(),args[1]->decimal_int_part());
return min(max_int_part + decimals, DECIMAL_MAX_PRECISION);
int arg0_int_part= args[0]->decimal_int_part();
int arg1_int_part= args[1]->decimal_int_part();
int max_int_part= max(arg0_int_part, arg1_int_part);
int precision= max_int_part + decimals;
return min(precision, DECIMAL_MAX_PRECISION);
}
@ -2281,8 +2284,9 @@ Item_func_if::fix_length_and_dec()
uint Item_func_if::decimal_precision() const
{
int precision=(max(args[1]->decimal_int_part(),args[2]->decimal_int_part())+
decimals);
int arg1_prec= args[1]->decimal_int_part();
int arg2_prec= args[2]->decimal_int_part();
int precision=max(arg1_prec,arg2_prec) + decimals;
return min(precision, DECIMAL_MAX_PRECISION);
}

15
sql/item_func.cc
View File

@ -1156,9 +1156,10 @@ my_decimal *Item_func_plus::decimal_op(my_decimal *decimal_value)
void Item_func_additive_op::result_precision()
{
decimals= max(args[0]->decimals, args[1]->decimals);
int max_int_part= max(args[0]->decimal_precision() - args[0]->decimals,
args[1]->decimal_precision() - args[1]->decimals);
int precision= min(max_int_part + 1 + decimals, DECIMAL_MAX_PRECISION);
int arg1_int= args[0]->decimal_precision() - args[0]->decimals;
int arg2_int= args[1]->decimal_precision() - args[1]->decimals;
int est_prec= max(arg1_int, arg2_int) + 1 + decimals;
int precision= min(est_prec, DECIMAL_MAX_PRECISION);
/* Integer operations keep unsigned_flag if one of arguments is unsigned */
if (result_type() == INT_RESULT)
@ -1267,8 +1268,8 @@ void Item_func_mul::result_precision()
else
unsigned_flag= args[0]->unsigned_flag & args[1]->unsigned_flag;
decimals= min(args[0]->decimals + args[1]->decimals, DECIMAL_MAX_SCALE);
int precision= min(args[0]->decimal_precision() + args[1]->decimal_precision(),
DECIMAL_MAX_PRECISION);
uint est_prec = args[0]->decimal_precision() + args[1]->decimal_precision();
uint precision= min(est_prec, DECIMAL_MAX_PRECISION);
max_length= my_decimal_precision_to_length(precision, decimals,unsigned_flag);
}
@ -1315,8 +1316,8 @@ my_decimal *Item_func_div::decimal_op(my_decimal *decimal_value)
void Item_func_div::result_precision()
{
uint precision=min(args[0]->decimal_precision() + prec_increment,
DECIMAL_MAX_PRECISION);
uint arg_prec= args[0]->decimal_precision() + prec_increment;
uint precision=min(arg_prec, DECIMAL_MAX_PRECISION);
/* Integer operations keep unsigned_flag if one of arguments is unsigned */
if (result_type() == INT_RESULT)
unsigned_flag= args[0]->unsigned_flag | args[1]->unsigned_flag;