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Commitb2d4792

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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: 46 additions & 27 deletions
Original file line numberDiff line numberDiff line change
@@ -4235,67 +4235,86 @@ int64_to_numeric(int64 val)
42354235
}
42364236

42374237
/*
4238-
* Convert val1/(10**val2) to numeric. This is much faster than normal
4238+
* Convert val1/(10**log10val2) to numeric. This is much faster than normal
42394239
* numeric division.
42404240
*/
42414241
Numeric
42424242
int64_div_fast_to_numeric(int64val1,intlog10val2)
42434243
{
42444244
Numericres;
42454245
NumericVarresult;
4246-
int64saved_val1=val1;
4246+
intrscale;
42474247
intw;
42484248
intm;
42494249

4250+
init_var(&result);
4251+
4252+
/* result scale */
4253+
rscale=log10val2<0 ?0 :log10val2;
4254+
42504255
/* how much to decrease the weight by */
42514256
w=log10val2 /DEC_DIGITS;
4252-
/* how much is left */
4257+
/* how much is leftto divide by*/
42534258
m=log10val2 %DEC_DIGITS;
4259+
if (m<0)
4260+
{
4261+
m+=DEC_DIGITS;
4262+
w--;
4263+
}
42544264

42554265
/*
4256-
* If there is anything left, multiply the dividend by what's left, then
4257-
* shift the weight by one more.
4266+
* If there is anything left to divide by (10^m with 0 < m < DEC_DIGITS),
4267+
* multiply the dividend by 10^(DEC_DIGITS - m), and shift the weight by
4268+
* one more.
42584269
*/
42594270
if (m>0)
42604271
{
42614272
#ifDEC_DIGITS==4
4262-
staticintpow10[]= {1,10,100,1000};
4273+
staticconstintpow10[]= {1,10,100,1000};
42634274
#elifDEC_DIGITS==2
4264-
staticintpow10[]= {1,10};
4275+
staticconstintpow10[]= {1,10};
42654276
#elifDEC_DIGITS==1
4266-
staticintpow10[]= {1};
4277+
staticconstintpow10[]= {1};
42674278
#else
42684279
#error unsupported NBASE
42694280
#endif
4281+
int64factor=pow10[DEC_DIGITS-m];
4282+
int64new_val1;
42704283

42714284
StaticAssertDecl(lengthof(pow10)==DEC_DIGITS,"mismatch with DEC_DIGITS");
42724285

4273-
if (unlikely(pg_mul_s64_overflow(val1,pow10[DEC_DIGITS-m],&val1)))
4286+
if (unlikely(pg_mul_s64_overflow(val1,factor,&new_val1)))
42744287
{
4275-
/*
4276-
* If it doesn't fit, do the whole computation in numeric the slow
4277-
* way. Note that va1l may have been overwritten, so use
4278-
* saved_val1 instead.
4279-
*/
4280-
intval2=1;
4288+
#ifdefHAVE_INT128
4289+
/* do the multiplication using 128-bit integers */
4290+
int128tmp;
42814291

4282-
for (inti=0;i<log10val2;i++)
4283-
val2 *=10;
4284-
res=numeric_div_opt_error(int64_to_numeric(saved_val1),int64_to_numeric(val2),NULL);
4285-
res=DatumGetNumeric(DirectFunctionCall2(numeric_round,
4286-
NumericGetDatum(res),
4287-
Int32GetDatum(log10val2)));
4288-
returnres;
4292+
tmp= (int128)val1* (int128)factor;
4293+
4294+
int128_to_numericvar(tmp,&result);
4295+
#else
4296+
/* do the multiplication using numerics */
4297+
NumericVartmp;
4298+
4299+
init_var(&tmp);
4300+
4301+
int64_to_numericvar(val1,&result);
4302+
int64_to_numericvar(factor,&tmp);
4303+
mul_var(&result,&tmp,&result,0);
4304+
4305+
free_var(&tmp);
4306+
#endif
42894307
}
4308+
else
4309+
int64_to_numericvar(new_val1,&result);
4310+
42904311
w++;
42914312
}
4292-
4293-
init_var(&result);
4294-
4295-
int64_to_numericvar(val1,&result);
4313+
else
4314+
int64_to_numericvar(val1,&result);
42964315

42974316
result.weight-=w;
4298-
result.dscale+=w*DEC_DIGITS- (DEC_DIGITS-m);
4317+
result.dscale=rscale;
42994318

43004319
res=make_result(&result);
43014320

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