Re: no default hash partition

At Tue, 6 Aug 2019 23:26:19 -0400, Robert Haas <robertmhaas@gmail.com> wrote in <CA+TgmoZpAsYY+naYpuw+fG=J1wYTXrhk=3uEYYa_Nz=Jwck+eg@mail.gmail.com>
> On Tue, Aug 6, 2019 at 6:58 PM Tom Lane <tgl@sss.pgh.pa.us> wrote:
> I think, as Amit says, that having an automatic partition creation
> feature for hash partitions (and maybe other kinds, but certainly for
> hash) would be a useful thing to add to the system. I also think that
> it might be useful to add some commands to automate partition
> splitting (and maybe combining) although I think there's some design
> work to be done there to figure out exactly what we should build.  I
> don't think it's ever useful to have a hash-partitioned table with an
> incomplete set of partitions long term, but it makes things simpler to
> allow that temporarily, for example during dump restoration.
> Therefore, I see no reason why we would want to go to the trouble of
> allowing hash-partitioned tables to have default partitions; it would
> just encourage people to do things that don't really make any sense.

+1.

By the way, couldn't we offer a means to check for gaps in a hash
partition? For example, the output of current \d+ <parent>
contains the Partitoins section that shows a list of
partitions. I think that we can show all gaps there.

=# \d+ p
                               Partitioned table "public.p"
...
Partition key: HASH (a)
Partitions: c1 FOR VALUES WITH (modulus 4, remainder 0),
            c3 FOR VALUES WITH (modulus 4, remainder 3),
            GAP (modulus 4, remainder 1),
            GAP (modulus 4, remainder 2)

Or

Partitions: c1 FOR VALUES WITH (modulus 4, remainder 0),
            c3 FOR VALUES WITH (modulus 4, remainder 3),
Gaps: (modulus 4, remainder 1), (modulus 4, remainder 2)


regards.

-- 
Kyotaro Horiguchi
NTT Open Source Software Center