validate column: sum, min, max false success for numeric values with precision > 16

[nj1973]

Test BigQuery tables:

create table `dvt_test.tab_long_dec1` (
  id int64 not null
, col_16 numeric(16)
, col_17 numeric(17)
, col_18 numeric(18));
insert into dvt_test.tab_long_dec1 values
(1,NUMERIC '1234567890123456',NUMERIC '12345678901234567',NUMERIC '123456789012345678');
create table dvt_test.tab_long_dec2 (
  id int64 not null
, col_16 numeric(16)
, col_17 numeric(17)
, col_18 numeric(18));
insert into dvt_test.tab_long_dec2 values
(1,NUMERIC '1234567890123456'+1,NUMERIC '12345678901234567'+1,NUMERIC '123456789012345678'+1);

Note that tab_long_dec2 data differs from tab_long_dec1. The value in col_16, col_27 and col_18 has been incremented by 1.
Therefore sum and max comparison of these columns should fail.

col_16

data-validation validate column -sc bq -tc bq \
-tbls=dvt_test.tab_long_dec1=dvt_test.tab_long_dec2 \
-sum=col_16 -max=col_16

Correct behaviour, all columns have validation_status="fail"

col_17

data-validation validate column -sc bq -tc bq \
-tbls=dvt_test.tab_long_dec1=dvt_test.tab_long_dec2 \
-sum=col_17 -max=col_17

Incorrect behaviour, sum__col_17 and max__col_17 have validation_status="success". This is wrong.

col_18

data-validation validate column -sc bq -tc bq \
-tbls=dvt_test.tab_long_dec1=dvt_test.tab_long_dec2 \
-sum=col_18 -max=col_18

Incorrect behaviour, sum__col_18 and max__col_18 have validation_status="success". This is wrong.

I suspect this relates to code in data_validation/combiner.py that casts all values to float64. 64 bit float is a lossy data type for large values.
I saw the same issue when testing PostgreSQL too, I believe the problem is not engine specific.

[nj1973]

We should also add an integration test for this.

[nj1973]

Closed by fix for issue 900, duplicate issues.