Query related to alter table ... attach partition

Hi All,

I have created a regular table with CHECK constraint on the partition
key column and it conflicts with the partition constraint but, still,
i could attach the table with the partitioned table. Here is what i am
trying to do,

postgres[76308]=# create table part_tab (b int, a int) partition by range (a);
CREATE TABLE

postgres[76308]=# create table part1 (a int, b int CHECK (a >= 5));
CREATE TABLE

postgres[76308]=# alter table part_tab attach partition part1 for
values from (0) to (5); -- the partition constraint applied here
conflicts with CHECK (a >= 5) applied on part1.
ALTER TABLE

postgres[76308]=# \d+ part1;
                                    Table "public.part1"
+--------+---------+-----------+----------+---------+---------+--------------+-------------+
| Column |  Type   | Collation | Nullable | Default | Storage | Stats
target | Description |
+--------+---------+-----------+----------+---------+---------+--------------+-------------+
| a      | integer |           |          |         | plain   |
      |             |
| b      | integer |           |          |         | plain   |
      |             |
+--------+---------+-----------+----------+---------+---------+--------------+-------------+
Partition of: part_tab FOR VALUES FROM (0) TO (5)
Partition constraint: ((a IS NOT NULL) AND (a >= 0) AND (a < 5))
Check constraints:
    "part1_a_check" CHECK (a >= 5)
Options: storage_engine=zheap

As shown in the description of part1 (child table) above, Partition
constraint i.e.  (a >= 0) AND (a < 5) and the CHECK constraint  a >= 5
conflicts with each other but still alter table ... attach partition
succeeded. Isn't that a bug?

--
With Regards,
Ashutosh Sharma
EnterpriseDB:http://www.enterprisedb.com