BUG #4973: number precision or scale lost when altering table column

The following bug has been logged online:

Bug reference: 4973
Logged by: terry
Email address: 94487509@qq.com
PostgreSQL version: 8.3.3
Operating system: linux
Description: number precision or scale lost when altering table
column
Details:

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TEST=# CREATE TABLE B (C NUMERIC(8,3));
CREATE TABLE
TEST=# INSERT INTO B VALUES (12345.678);
INSERT 0 1
TEST=# SELECT * FROM B;
c
-----------
12345.678
(1 row)

TEST=# ALTER TABLE B ALTER COLUMN C TYPE NUMERIC(4,0);
ERROR: numeric field overflow
DETAIL: A field with precision 4, scale 0 must round to an absolute value
less than 10^4.
TEST=# ALTER TABLE B ALTER COLUMN C TYPE NUMERIC(5,0);
ALTER TABLE

/* scale lost */
TEST=# SELECT * FROM B;
c
-------
12346
(1 row)

TEST=#

oracle:
SQL> CREATE TABLE Y (I NUMERIC(4,2));

Table created.

SQL> INSERT INTO Y VALUES (12.21);

1 row created.

SQL> SELECT * FROM Y;

I
----------
12.21

ORACLE can not modify, because precision or scale will be lost
SQL> ALTER TABLE Y MODIFY I NUMERIC(3,0);
ALTER TABLE Y MODIFY I NUMERIC(3,0)
*
ERROR at line 1:
ORA-01440: column to be modified must be empty to decrease precision or
scale

SQL> ALTER TABLE Y MODIFY I NUMERIC(5,3);

Table altered.

SQL> INSERT INTO Y VALUES (12.123);

1 row created.

SQL> SELECT * FROM Y;

I
----------
12.21
12.123