Re: Partitioning with range types

On Fri, Jun 15, 2018 at 11:23 AM, Adrian Klaver <adrian(dot)klaver(at)aklaver(dot)com>
wrote:

> On 06/15/2018 08:26 AM, Jeremy Finzel wrote:
>
>> Several months ago we had some detailed discussions about whether to use
>> separate date columns to indicate a date range, or to use the daterange
>> data type. We opted for the latter because this type is specifically
>> designed for this use case - a table that has a range of valid dates for
>> the data it contains. It also has some great operators and functions.
>>
>> But I recently discovered that daterange is not supported in any way as a
>> partition key because it depends on an expression. I was excited
>>
>
> A quick test:
>
> Postgres 10.4
>
> create table dr_partition(id integer, dr daterange) PARTITION BY LIST(dr);
>
> \d dr_partition
> Table "public.dr_partition"
> Column | Type | Collation | Nullable | Default
> --------+-----------+-----------+----------+---------
> id | integer | | |
> dr | daterange | | |
> Partition key: LIST (dr)
>
>
> create table dr_1 PARTITION OF dr_partition FOR VALUES IN ('[06/01/2018,
> 06/30/2018]');
>
> \d dr_1
> Table "public.dr_1"
> Column | Type | Collation | Nullable | Default
> --------+-----------+-----------+----------+---------
> id | integer | | |
> dr | daterange | | |
> Partition of: dr_partition FOR VALUES IN ('[2018-06-01,2018-07-01)')
>
>
>
> about this possibility in pg11 with unique constraints on the parent
>> table, but now it appears it may have instead been to our advantage if we
>> had two separate date columns instead, so that we could use UPSERT
>> transparently for date-ranged tables.
>>
>> Is there any possibility of this feature coming for range types, or, if
>> we really want to partition using daterange, should we look instead at two
>> separate date columns?
>>
>> Thanks,
>> Jeremy
>>
>
>
> --
> Adrian Klaver
> adrian(dot)klaver(at)aklaver(dot)com
>

Let me clarify - what I said was not accurate. What I meant is that using
an UPSERT on a parent partition is not supported with range types
specifically because we can't create unique indexes involving expressions
on parent partitions:

CREATE UNIQUE INDEX ON foo (id, lower(as_of_date));
ERROR: unsupported UNIQUE constraint with partition key definition
DETAIL: UNIQUE constraints cannot be used when partition keys include
expressions.

Workaround is of course not to use UPSERT, but we all know the advantages
of using UPSERT to handle concurrency and the like and to make our queries
simpler. We are currently using UPSERT for many of these tables, but they
are not partitioned yet.

Thanks,
Jeremy