Re: Adding support for Default partition in partitioning

>I suspect it could be done as of now, but I'm a little worried that it
>might create grammar conflicts in the future as we extend the syntax
>further. If we use CREATE TABLE ... PARTITION OF .. DEFAULT, then the
>word DEFAULT appears in the same position where we'd normally have FOR
>VALUES, and so the parser will definitely be able to figure out what's
>going on. When it gets to that position, it will see FOR or it will
>see DEFAULT, and all is clear. OTOH, if we use CREATE TABLE ...
>DEFAULT PARTITION OF ..., then we have action at a distance: whether
>or not the word DEFAULT is present before PARTITION affects which
>tokens are legal after the parent table name. bison isn't always very
>smart about that kind of thing. No particular dangers come to mind at
>the moment, but it makes me nervous anyway.

+1 for CREATE TABLE..PARTITION OF...DEFAULT syntax.
I think substituting DEFAULT for FOR VALUES is appropriate as
both cases are mutually exclusive.

One more thing that needs consideration is should default partitions be
partitioned further? Other databases allow default partitions to be
partitioned further. I think, its normal for users to expect the data in
default partitions to also be divided into sub partitions. So
it should be supported.
My colleague Rajkumar Raghuwanshi brought to my notice the current patch
does not handle this correctly.
I will include this in the updated patch if there is no objection.

On the other hand if sub partitions of a default partition is to be
prohibited,
an error should be thrown if PARTITION BY is specified after DEFAULT.

Thank you,
Rahila Syed

On Tue, Apr 25, 2017 at 1:46 AM, Robert Haas <robertmhaas(at)gmail(dot)com> wrote:

> On Mon, Apr 24, 2017 at 8:14 AM, Ashutosh Bapat
> <ashutosh(dot)bapat(at)enterprisedb(dot)com> wrote:
> > On Mon, Apr 24, 2017 at 4:24 PM, Robert Haas <robertmhaas(at)gmail(dot)com>
> wrote:
> >> On Mon, Apr 24, 2017 at 5:10 AM, Rahila Syed <rahilasyed90(at)gmail(dot)com>
> wrote:
> >>> Following can also be considered as it specifies more clearly that the
> >>> partition holds default values.
> >>>
> >>> CREATE TABLE ...PARTITION OF...FOR VALUES DEFAULT;
> >>
> >> The partition doesn't contain default values; it is itself a default.
> >
> > Is CREATE TABLE ... DEFAULT PARTITION OF ... feasible? That sounds more
> natural.
>
> I suspect it could be done as of now, but I'm a little worried that it
> might create grammar conflicts in the future as we extend the syntax
> further. If we use CREATE TABLE ... PARTITION OF .. DEFAULT, then the
> word DEFAULT appears in the same position where we'd normally have FOR
> VALUES, and so the parser will definitely be able to figure out what's
> going on. When it gets to that position, it will see FOR or it will
> see DEFAULT, and all is clear. OTOH, if we use CREATE TABLE ...
> DEFAULT PARTITION OF ..., then we have action at a distance: whether
> or not the word DEFAULT is present before PARTITION affects which
> tokens are legal after the parent table name. bison isn't always very
> smart about that kind of thing. No particular dangers come to mind at
> the moment, but it makes me nervous anyway.
>
> --
> Robert Haas
> EnterpriseDB: http://www.enterprisedb.com
> The Enterprise PostgreSQL Company
>