Re: On partitioning

On Wed, Dec 10, 2014 at 12:46 PM, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
> On Tue, Dec 9, 2014 at 7:21 PM, Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>
> wrote:
>>
>> Amit Kapila wrote:
>> > On Tue, Dec 9, 2014 at 1:42 AM, Robert Haas <robertmhaas(at)gmail(dot)com>
>> > wrote:
>> > > On Mon, Dec 8, 2014 at 2:56 PM, Andres Freund <andres(at)2ndquadrant(dot)com>
>> > wrote:
>> > > >> I don't think that's mutually exclusive with the idea of
>> > > >> partitions-as-tables. I mean, you can add code to the ALTER TABLE
>> > > >> path that says if (i_am_not_the_partitioning_root) ereport(ERROR,
>> > > >> ...)
>> > > >> wherever you want.
>> > > >
>> > > > That'll be a lot of places you'll need to touch. More fundamentally:
>> > > > Why
>> > > > should we name something a table that's not one?
>> > >
>> > > Well, I'm not convinced that it isn't one. And adding a new relkind
>> > > will involve a bunch of code churn, too. But I don't much care to
>> > > pre-litigate this: when someone has got a patch, we can either agree
>> > > that the approach is OK or argue that it is problematic because X. I
>> > > think we need to hammer down the design in broad strokes first, and
>> > > I'm not sure we're totally there yet.
>> >
>> > That's right, I think at this point defining the top level
>> > behaviour/design
>> > is very important to proceed, we can decide about the better
>> > implementation approach afterwards (may be once initial patch is ready,
>> > because it might not be a major work to do it either way). So here's
>> > where
>> > we are on this point till now as per my understanding, I think that
>> > direct
>> > operations should be prohibited on partitions, you think that they
>> > should be
>> > allowed and Andres think that it might be better to allow direct
>> > operations
>> > on partitions for Read.
>>
>> FWIW in my original proposal I was rejecting some things that after
>> further consideration turn out to be possible to allow; for instance
>> directly referencing individual partitions in COPY. We could allow
>> something like
>>
>> COPY lineitems PARTITION FOR VALUE '2000-01-01' TO STDOUT
>> or maybe
>> COPY PARTITION FOR VALUE '2000-01-01' ON TABLE lineitems TO STDOUT
>>
> or
> COPY [TABLE] lineitems PARTITION FOR VALUE '2000-01-01' TO STDOUT
> COPY [TABLE] lineitems PARTITION <part_1,part_2,> TO STDOUT
>
> I think we should try to support operations on partitions via main
> table whereever it is required.
>

We can also allow to explicitly name a partition

COPY [TABLE ] lineitems PARTITION lineitems_2001 TO STDOUT;

Thanks,
Amit