Re: Overlapping values (?) in multi-column partitioned tables

[Brent Wood <Brent.Wood@xxxxxxxxxx>]

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 gets records with a date of '24-02-01", it seems that without a more explicit definition there is ambiguity on dates at the partition 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

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From: Christophe Pettus <xof@xxxxxxxxxxxx>
Sent: Wednesday, September 11, 2024 10:13
To: pgsql-general <pgsql-general@xxxxxxxxxxxxxx>
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 would go into.  (I'm imagining it on a cartesian plane, and there isn't any overlap between the rectangles those partition boundaries 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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