On Tue, Dec 9, 2014 at 8:08 AM, Amit Langote <
Langote_Amit_f8@lab.ntt.co.jp> wrote:
> > From: Robert Haas [mailto:
robertmhaas@gmail.com]
> > On Sat, Dec 6, 2014 at 2:59 AM, Amit Kapila <
amit.kapila16@gmail.com>
> > wrote:
> > >> I guess you could list or hash partition on multiple columns, too.
> > >
> > > How would you distinguish values in list partition for multiple
> > > columns? I mean for range partition, we are sure there will
> > > be either one value for each column, but for list it could
> > > be multiple and not fixed for each partition, so I think it will not
> > > be easy to support the multicolumn partition key for list
> > > partitions.
> >
> > I don't understand. If you want to range partition on columns (a, b),
> > you say that, say, tuples with (a, b) values less than (100, 200) go
> > here and the rest go elsewhere. For list partitioning, you say that,
> > say, tuples with (a, b) values of EXACTLY (100, 200) go here and the
> > rest go elsewhere. I'm not sure how useful that is but it's not
> > illogical.
> >
>
> In case of list partitioning, 100 and 200 would respectively be one of the values in lists of allowed values for a and b. I thought his concern is whether this "list of values for each column in partkey" is as convenient to store and manipulate as range partvalues.
>
Yeah and also how would user specify the values, as an example
assume that table is partitioned on monthly_salary, so partition
definition would look:
PARTITION BY LIST(monthly_salary)
(
PARTITION salary_less_than_thousand VALUES(300, 900),
PARTITION salary_less_than_two_thousand VALUES (500,1000,1500),
...
)
Now if user wants to define multi-column Partition based on
monthly_salary and annual_salary, how do we want him to
specify the values. Basically how to distinguish which values
belong to first column key and which one's belong to second
column key.
