Thread: Numeric modulo operator is incorrect.

Dear sir,

I build PostgreSQL 7.0.3 with jumbo-20010318.patch.gz on Vine Linux2.1.5.

Following result are incorrect. Am I under an illusion?

test=# select '34666624082'::numeric % '34666671'::numeric;
 ?column?
----------
   -46918
(1 row)

test=# select '34666624082'::numeric - '34666671'::numeric
    * trunc('34666624082'::numeric / '34666671'::numeric);
 ?column?
----------
 34619753
(1 row)

Ken-ichi Yamasaki <yama@yuzu.gr.jp> writes:
> I build PostgreSQL 7.0.3 with jumbo-20010318.patch.gz on Vine Linux2.1.5.

> Following result are incorrect. Am I under an illusion?

> test=# select '34666624082'::numeric % '34666671'::numeric;
>  ?column?
> ----------
>    -46918
> (1 row)

This is a bug; looks like mod_var() is using a rather silly estimate
of how many digits of precision it needs to keep in the division step.

I have a fix but I'm not sure if it will get into 7.1 or be held
for 7.1.1 ...

            regards, tom lane