Re: Overlapping values (?) in multi-column partitioned tables - Mailing list pgsql-general

The comparisons for partitions are lower <= value < upper, so this works fine:

> xof=# create table t (pk bigint not null, ts timestamp not null) partition by range (ts);
> CREATE TABLE
> xof=# create table t1 partition of t for values from ('2024-01-01'::timestamp) to ('2024-02-01'::timestamp);
> CREATE TABLE
> xof=# create table t2 partition of t for values from ('2024-02-01'::timestamp) to ('2024-03-01'::timestamp);
> CREATE TABLE

In both cases, it's unambiguous that a record with ('2024-02-01'::timestamp) would go into t2.

> On Sep 10, 2024, at 15:23, Brent Wood <Brent.Wood@niwa.co.nz> wrote:
>
> I'm not sure of the less than vs less than or equals in this one, so it may be my ignorance... but which partition
getsrecords with a date of '24-02-01", it seems that without a more explicit definition there is ambiguity on dates at
thepartition limits when those dates are common to multiple partitions? 
>
> To avoid this shouldn't the definition be:
>
>> xof=# create table t (pk bigint not null, ts timestamp not null) partition by range (ts, pk);
>> CREATE TABLE
>> xof=# create table t1 partition of t for values from ('2024-01-01'::timestamp, minvalue) to
('2024-01-31'::timestamp,maxvalue); 
>> CREATE TABLE
>> xof=# create table t2 partition of t for values from ('2024-02-01'::timestamp, minvalue) to
('2024-02-29'::timestamp,maxvalue); 
>
>
> Brent Wood
>
> Principal Technician, Fisheries
> NIWA
> DDI:  +64 (4) 3860529
> From: Christophe Pettus <xof@thebuild.com>
> Sent: Wednesday, September 11, 2024 10:13
> To: pgsql-general <pgsql-general@postgresql.org>
> Subject: Overlapping values (?) in multi-column partitioned tables
> Hi,
>
> I am clearly not understanding something.  Consider:
>
>> xof=# create table t (pk bigint not null, ts timestamp not null) partition by range (ts, pk);
>> CREATE TABLE
>> xof=# create table t1 partition of t for values from ('2024-01-01'::timestamp, minvalue) to
('2024-02-01'::timestamp,maxvalue); 
>> CREATE TABLE
>> xof=# create table t2 partition of t for values from ('2024-02-01'::timestamp, minvalue) to
('2024-03-01'::timestamp,maxvalue); 
>> ERROR:  partition "t2" would overlap partition "t1"
>> LINE 1: ...on of t for values from ('2024-02-01'::timestamp, minvalue) ...
>>                                                            ^
>> xof=#
>
> In what way do those partitions overlap?  In other words, there does not appear to be a value of (ts, pk) having
'2024-01-01'::timestamp<= ts < '2024-03-01'::timestamp for any pk where it would be ambiguous which partition that row
wouldgo into.  (I'm imagining it on a cartesian plane, and there isn't any overlap between the rectangles those
partitionboundaries define.) 
>
> I'm obviously missing something, but... what?  Thank you!
>
> Brent Wood
> Principal Technician - GIS and Spatial Data Management
> Programme Leader - Environmental Information Delivery
> +64-4-386-0529
>
> National Institute of Water & Atmospheric Research Ltd (NIWA)
> 301 Evans Bay Parade Hataitai Wellington New Zealand
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