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Commit86bfbea

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Make int64_div_fast_to_numeric() more robust.
The prior coding of int64_div_fast_to_numeric() had a number of bugsthat would cause it to fail under different circumstances, such aswith log10val2 <= 0, or log10val2 a multiple of 4, or in the "slow"numeric path with log10val2 >= 10.None of those could be triggered by any of our current code, whichonly uses log10val2 = 3 or 6. However, they made it a hazard for anyfuture code that might use it. Also, since this is exported bynumeric.c, users writing their own C code might choose to use it.Therefore fix, and back-patch to v14, where it was introduced.Dean Rasheed, reviewed by Tom Lane.Discussion:https://postgr.es/m/CAEZATCW8gXgW0tgPxPgHDPhVX71%2BSWFRkhnXy%2BTfGDsKLepu2g%40mail.gmail.com
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‎src/backend/utils/adt/numeric.c

Lines changed: 54 additions & 26 deletions
Original file line numberDiff line numberDiff line change
@@ -4089,58 +4089,86 @@ int64_to_numeric(int64 val)
40894089
}
40904090

40914091
/*
4092-
* Convert val1/(10**val2) to numeric. This is much faster than normal
4092+
* Convert val1/(10**log10val2) to numeric. This is much faster than normal
40934093
* numeric division.
40944094
*/
40954095
Numeric
40964096
int64_div_fast_to_numeric(int64val1,intlog10val2)
40974097
{
40984098
Numericres;
40994099
NumericVarresult;
4100-
int64saved_val1=val1;
4100+
intrscale;
41014101
intw;
41024102
intm;
41034103

4104+
init_var(&result);
4105+
4106+
/* result scale */
4107+
rscale=log10val2<0 ?0 :log10val2;
4108+
41044109
/* how much to decrease the weight by */
41054110
w=log10val2 /DEC_DIGITS;
4106-
/* how much is left */
4111+
/* how much is leftto divide by*/
41074112
m=log10val2 %DEC_DIGITS;
4113+
if (m<0)
4114+
{
4115+
m+=DEC_DIGITS;
4116+
w--;
4117+
}
41084118

41094119
/*
4110-
* If there is anything left, multiply the dividend by what's left, then
4111-
* shift the weight by one more.
4120+
* If there is anything left to divide by (10^m with 0 < m < DEC_DIGITS),
4121+
* multiply the dividend by 10^(DEC_DIGITS - m), and shift the weight by
4122+
* one more.
41124123
*/
41134124
if (m>0)
41144125
{
4115-
staticintpow10[]= {1,10,100,1000};
4126+
#ifDEC_DIGITS==4
4127+
staticconstintpow10[]= {1,10,100,1000};
4128+
#elifDEC_DIGITS==2
4129+
staticconstintpow10[]= {1,10};
4130+
#elifDEC_DIGITS==1
4131+
staticconstintpow10[]= {1};
4132+
#else
4133+
#error unsupported NBASE
4134+
#endif
4135+
int64factor=pow10[DEC_DIGITS-m];
4136+
int64new_val1;
41164137

41174138
StaticAssertStmt(lengthof(pow10)==DEC_DIGITS,"mismatch with DEC_DIGITS");
4118-
if (unlikely(pg_mul_s64_overflow(val1,pow10[DEC_DIGITS-m],&val1)))
4139+
4140+
if (unlikely(pg_mul_s64_overflow(val1,factor,&new_val1)))
41194141
{
4120-
/*
4121-
* If it doesn't fit, do the whole computation in numeric the slow
4122-
* way. Note that va1l may have been overwritten, so use
4123-
* saved_val1 instead.
4124-
*/
4125-
intval2=1;
4126-
4127-
for (inti=0;i<log10val2;i++)
4128-
val2 *=10;
4129-
res=numeric_div_opt_error(int64_to_numeric(saved_val1),int64_to_numeric(val2),NULL);
4130-
res=DatumGetNumeric(DirectFunctionCall2(numeric_round,
4131-
NumericGetDatum(res),
4132-
Int32GetDatum(log10val2)));
4133-
returnres;
4142+
#ifdefHAVE_INT128
4143+
/* do the multiplication using 128-bit integers */
4144+
int128tmp;
4145+
4146+
tmp= (int128)val1* (int128)factor;
4147+
4148+
int128_to_numericvar(tmp,&result);
4149+
#else
4150+
/* do the multiplication using numerics */
4151+
NumericVartmp;
4152+
4153+
init_var(&tmp);
4154+
4155+
int64_to_numericvar(val1,&result);
4156+
int64_to_numericvar(factor,&tmp);
4157+
mul_var(&result,&tmp,&result,0);
4158+
4159+
free_var(&tmp);
4160+
#endif
41344161
}
4162+
else
4163+
int64_to_numericvar(new_val1,&result);
4164+
41354165
w++;
41364166
}
4137-
4138-
init_var(&result);
4139-
4140-
int64_to_numericvar(val1,&result);
4167+
else
4168+
int64_to_numericvar(val1,&result);
41414169

41424170
result.weight-=w;
4143-
result.dscale+=w*DEC_DIGITS- (DEC_DIGITS-m);
4171+
result.dscale=rscale;
41444172

41454173
res=make_result(&result);
41464174

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