Question related to partitioning with pg_partman

Starting a new thread...

Something interesting and not sure if its expected behaviour as below. We
are also confused a bit here.

In the below example we created two partitioned tables on timestamptz type
columns with different time zones and the child partitions are created
appropriately with boundaries as one mid night to next mid night of a day
and so on. But when we change the time zone and query the data dictionary
views again, it shows the start and end of the partition boundary as not
midnights but different times of the day's values.

So I was wondering if this can cause us any unforeseen issues in the long
run while creating the partitions though partman and persisting the data
into the tables from the end users then querying those and having queries
properly partitioned pruned?
or
should we always set the local timezone as UTC always before running or
calling the pg_partman/pg_cron process which creates the partitions? Mainly
in a database which serves global users sitting across multiple timezones.
And same thing while inserting data into the table, we should use UTC
timezone conversion function. Can you please confirm.

And while checking the timezone using the "show timezone" function it shows
the local timezone, so is there any way to see postgres DB the server
timezone?

*******Example********

SET SESSION TIME ZONE 'UTC';
CREATE TABLE test_timestamp (
ts TIMESTAMP,
tstz TIMESTAMPTZ) PARTITION BY RANGE (tstz);

SELECT partman.create_parent(
p_parent_table := 'public.test_timestamp',
p_control := 'tstz',
p_type := 'native',
p_interval := '1 day',
p_premake := 4,
p_start_partition => '2024-03-07 00:00:00'
);

UPDATE partman.part_config SET infinite_time_partitions = 'true' WHERE
parent_table = 'public.test_timestamp';

with recursive inh as (
select i.inhrelid, null::text as parent
from pg_catalog.pg_inherits i
join pg_catalog.pg_class cl on i.inhparent = cl.oid
join pg_catalog.pg_namespace nsp on cl.relnamespace = nsp.oid
where nsp.nspname = 'public'
and cl.relname = 'test_timestamp2'
union all
select i.inhrelid, (i.inhparent::regclass)::text
from inh
join pg_catalog.pg_inherits i on (inh.inhrelid = i.inhparent)
)
select c.relname as partition_name,
pg_get_expr(c.relpartbound, c.oid, true) as partition_expression
from inh
join pg_catalog.pg_class c on inh.inhrelid = c.oid
join pg_catalog.pg_namespace n on c.relnamespace = n.oid
left join pg_partitioned_table p on p.partrelid = c.oid
order by n.nspname, c.relname;

test_timestamp_default DEFAULT
test_timestamp_p2024_03_07 FOR VALUES FROM ('2024-03-07 00:00:00+00') TO
('2024-03-08 00:00:00+00')
test_timestamp_p2024_03_08 FOR VALUES FROM ('2024-03-08 00:00:00+00') TO
('2024-03-09 00:00:00+00')
test_timestamp_p2024_03_09 FOR VALUES FROM ('2024-03-09 00:00:00+00') TO
('2024-03-10 00:00:00+00')
test_timestamp_p2024_03_10 FOR VALUES FROM ('2024-03-10 00:00:00+00') TO
('2024-03-11 00:00:00+00')
test_timestamp_p2024_03_11 FOR VALUES FROM ('2024-03-11 00:00:00+00') TO
('2024-03-12 00:00:00+00')

SET SESSION TIME ZONE 'EST';

test_timestamp_default DEFAULT
test_timestamp_p2024_03_07 FOR VALUES FROM ('2024-03-06 *19:00:00-05*') TO
('2024-03-07 19:00:00-05')
test_timestamp_p2024_03_08 FOR VALUES FROM ('2024-03-07 *19:00:00-05*') TO
('2024-03-08 19:00:00-05')
test_timestamp_p2024_03_09 FOR VALUES FROM ('2024-03-08 *19:00:00-05*') TO
('2024-03-09 19:00:00-05')
test_timestamp_p2024_03_10 FOR VALUES FROM ('2024-03-09 *19:00:00-05*') TO
('2024-03-10 19:00:00-05')
test_timestamp_p2024_03_11 FOR VALUES FROM ('2024-03-10 *19:00:00-05*') TO
('2024-03-11 19:00:00-05')

***********************

SET SESSION TIME ZONE 'EST';

CREATE TABLE test_timestamp2 (
ts TIMESTAMP,
tstz TIMESTAMPTZ) PARTITION BY RANGE (tstz);

SELECT partman.create_parent(
p_parent_table := 'public.test_timestamp2',
p_control := 'tstz',
p_type := 'native',
p_interval := '1 day',
p_premake := 4,
p_start_partition => '2024-03-07 00:00:00'
);

UPDATE partman.part_config SET infinite_time_partitions = 'true' WHERE
parent_table = 'public.test_timestamp2';

with recursive inh as (
select i.inhrelid, null::text as parent
from pg_catalog.pg_inherits i
join pg_catalog.pg_class cl on i.inhparent = cl.oid
join pg_catalog.pg_namespace nsp on cl.relnamespace = nsp.oid
where nsp.nspname = 'public'
and cl.relname = 'test_timestamp2'
union all
select i.inhrelid, (i.inhparent::regclass)::text
from inh
join pg_catalog.pg_inherits i on (inh.inhrelid = i.inhparent)
)
select c.relname as partition_name,
pg_get_expr(c.relpartbound, c.oid, true) as partition_expression
from inh
join pg_catalog.pg_class c on inh.inhrelid = c.oid
join pg_catalog.pg_namespace n on c.relnamespace = n.oid
left join pg_partitioned_table p on p.partrelid = c.oid
order by n.nspname, c.relname;

test_timestamp2_default DEFAULT
test_timestamp2_p2024_03_07 FOR VALUES FROM ('2024-03-07 00:00:00-05') TO
('2024-03-08 00:00:00-05')
test_timestamp2_p2024_03_08 FOR VALUES FROM ('2024-03-08 00:00:00-05') TO
('2024-03-09 00:00:00-05')
test_timestamp2_p2024_03_09 FOR VALUES FROM ('2024-03-09 00:00:00-05') TO
('2024-03-10 00:00:00-05')
test_timestamp2_p2024_03_10 FOR VALUES FROM ('2024-03-10 00:00:00-05') TO
('2024-03-11 00:00:00-05')
test_timestamp2_p2024_03_11 FOR VALUES FROM ('2024-03-11 00:00:00-05') TO
('2024-03-12 00:00:00-05')

SET SESSION TIME ZONE 'UTC';

test_timestamp2_default DEFAULT
test_timestamp2_p2024_03_07 FOR VALUES FROM ('2024-03-07 *05:00:00+00*') TO
('2024-03-08 05:00:00+00')
test_timestamp2_p2024_03_08 FOR VALUES FROM ('2024-03-08 *05:00:00+00*') TO
('2024-03-09 05:00:00+00')
test_timestamp2_p2024_03_09 FOR VALUES FROM ('2024-03-09 *05:00:00+00*') TO
('2024-03-10 05:00:00+00')
test_timestamp2_p2024_03_10 FOR VALUES FROM ('2024-03-10 *05:00:00+00*') TO
('2024-03-11 05:00:00+00')
test_timestamp2_p2024_03_11 FOR VALUES FROM ('2024-03-11 *05:00:00+00*') TO
('2024-03-12 05:00:00+00')