Re: Adding support for Default partition in partitioning

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
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