The following bug has been logged on the website:
Bug reference: 15434
Logged by: Andrey L
Email address: parihaaraka@gmail.com
PostgreSQL version: 10.5
Operating system: Ubuntu 16.04
Description:
# select
1800000000000000001::numeric / (10^18)::numeric truncated, -- truncates to
16 digits after decimal point
1800000000000000001::numeric(48,18) / (10^18)::numeric correct,
1800000000000000001::numeric / (10^18)::numeric * (10^18)::numeric
to_be_sure;
truncated | correct | to_be_sure
--------------------+----------------------+--------------------------------------
1.8000000000000000 | 1.800000000000000001 |
1800000000000000000.0000000000000000
(1 row)