On 3/10/24 10:51, sud wrote:
On Sun, Mar 10, 2024 at 10:32 PM Adrian Klaver
<adrian.klaver@xxxxxxxxxxx <mailto:adrian.klaver@xxxxxxxxxxx>> wrote:
On 3/10/24 05:12, sud wrote:
>
> In my example in the first post, I see, if someone connected to a
RDS
> Postgres database and run the create partition command using
pg_partman
> by setting the timezone as "UTC", the 7th march partition looks
to be
> spanned from "7th march midnight" to "8th march midnight", when
queried
> the partition_experession from the data dictionary view. Which is
correct.
>
> And same information if someone querying by setting the timezone
as EST
> is showing spanning from "6th march 7PM" to "7th March 7PM". And
this
> can cause sometimes the partition may shift to other days all
together.
> Similar differences happen if creating the partitions using EST
timezone
> initially and then querying the data dictionary from UTC timezone.
The above is at odds with your example below which has the correct
values:
2024-03-07 00:00:00+00 = 2024-03-06 19:00:00-05
>
> So my question was, if in these types of scenarios, we should
follow a
> standard approach of setting the timezone as UTC in such a type of
> global user use case, while the system can persist data from
multiple
> users sitting across different time zones? So that the
boundary(start
> and end time) of each of the range partitions will be set as
consistent
> in one timezone across all the partitioned tables?
You need to first determine what your time frames are going to be?
1) Midnight to Midnight in UTC will be consistent when viewed in
UTC. It
will not be when viewed in other time zone +/- the offset from UTC.
2) Or Midnight to Midnight in the users time zone, in which case the
UTC
values will differ.
You have to decide which of the above is your goal. The bottom line is
by definition the local wall clock time will not equal UTC, GMT
excepted. This comes down to what the purpose of the partitions are? In
other words how do you want to organize the data?
>
> And even while inserting the data , should we set the timezone to
first
> UTC and do the data load ?
>
> ******* Partition created by pg_partman by setting timezone as UTC
> ***************
>
> *UTC*
> *Partition_name Partition_expression*
> test_timestamp_p2024_03_07 FOR VALUES FROM ('2024-03-07
00:00:00+00') TO
> ('2024-03-08 00:00:00+00')
>
> when queried the partition_expression using EST ..
>
> *EST*
> *Partition_name Partition_expression*
> test_timestamp_p2024_03_07 FOR VALUES FROM ('2024-03-06
19:00:00-05') TO
> ('2024-03-07 19:00:00-05')
>
>
> ******* Partition created by pg_partman by setting timezone as EST
> ***************
>
> *EST*
> *Partition_name Partition_expression*
> test_timestamp2_p2024_03_07 FOR VALUES FROM ('2024-03-07
00:00:00-05')
> TO ('2024-03-08 00:00:00-05')
>
> when queried the partition_expression using UTC ..
>
> *UTC*
> *Partition_name Partition_expression*
> test_timestamp2_p2024_03_07 FOR VALUES FROM ('2024-03-07
05:00:00+00')
> TO ('2024-03-08 05:00:00+00')
>
> *******
>
> Also i see both the "setting" and "reset_val" is showing as local
> timezone only. If we set the timezone to a different value than the
> local timezone then it gets updated on the "setting".
Our requirement is to have the transaction table partitioned by
range daily on the transaction_date column(i.e one midnight to next
midnight transaction data in one partition). Transaction date column
will be of timestamptz data type. And this application/database might be
consuming data from users across multiple time zones in future. These
tables will be queried based on the date range (minimum being ~1
transaction day) and also will be purged one day partition.
So for above I understand , it might not be possible to keep the users
data restricted to one day partition in the table considering the users
will perform transactions across multiple timezones, but we are thinking
of restricting the database with UTC timezone irrespective of the users.
And thus during creating the table partitions , we need to ensure the
UTC timezone is set , such that the upper and lower boundary for the
daily range partitions remains consistent for all. Correct me if my
understanding is wrong.
1) The partition will be across one day(24 hours) it is just the times
may confuse people. Per you example 2024-03-07 00:00:00+00 is the same
time as 2024-03-06 19:00:00-05 for EST. The issue is that the +00 and
-05 maybe ignored. Also it depends on the clients being consistent in
using timestamptz.
2) You still have not answered what the datetime range(not date range)
is that will be queried. If you have the partitions Midnight to Midnight
UTC and the clients are querying Midnight to Midnight local time the
query will not match the partitions.
--
Adrian Klaver
adrian.klaver@xxxxxxxxxxx
