ull2dec: exact calculation of the precision

mysql-test/r/bigint.result

@@ -385,7 +385,7 @@ def					-((9223372036854775808))	8	20	20	N	32897	0	63
 -9223372036854775808
 select -(-(9223372036854775808));
 Catalog	Database	Table	Table_alias	Column	Column_alias	Type	Length	Max length	Is_null	Flags	Decimals	Charsetnr
-def					-(-(9223372036854775808))	246	21	19	N	32897	0	63
+def					-(-(9223372036854775808))	246	20	19	N	32897	0	63
 -(-(9223372036854775808))
 9223372036854775808
 select --9223372036854775808, ---9223372036854775808, ----9223372036854775808;
@@ -402,7 +402,7 @@ drop table t1;
 create table t1 select -9223372036854775809 bi;
 describe t1;
 Field	Type	Null	Key	Default	Extra
-bi	decimal(20,0)	NO		NULL	
+bi	decimal(19,0)	NO		NULL	
 drop table t1;
 #
 # Bug #45360: wrong results

mysql-test/r/dyncol.result

@@ -91,19 +91,19 @@ hex(COLUMN_CREATE(1, NULL AS decimal))
 000000
 select hex(COLUMN_CREATE(1, 1212 AS decimal));
 hex(COLUMN_CREATE(1, 1212 AS decimal))
-0001000100040900800004BC
+000100010004040084BC
 select hex(COLUMN_CREATE(1, 7 AS decimal));
 hex(COLUMN_CREATE(1, 7 AS decimal))
-000100010004090080000007
+000100010004010087
 select hex(COLUMN_CREATE(1, 8 AS decimal));
 hex(COLUMN_CREATE(1, 8 AS decimal))
-000100010004090080000008
+000100010004010088
 select hex(COLUMN_CREATE(1, 127 AS decimal));
 hex(COLUMN_CREATE(1, 127 AS decimal))
-00010001000409008000007F
+0001000100040300807F
 select hex(COLUMN_CREATE(1, 128 AS decimal));
 hex(COLUMN_CREATE(1, 128 AS decimal))
-000100010004090080000080
+00010001000403008080
 select hex(COLUMN_CREATE(1, 12.12 AS decimal));
 hex(COLUMN_CREATE(1, 12.12 AS decimal))
 00010001000402028C0C

strings/decimal.c

@@ -1005,8 +1005,7 @@ static int ull2dec(ulonglong from, decimal_t *to)
     error=E_DEC_OVERFLOW;
   }
   to->frac=0;
-  /* intg can't be bigger than number of digits in a ulonglong (20) */
-  to->intg= MY_MIN(intg1*DIG_PER_DEC1, 20);
+  for(to->intg= (intg1-1)*DIG_PER_DEC1; from; to->intg++, from/=10) {}
 
   for (buf=to->buf+intg1; intg1; intg1--)
   {