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From: Lok P <loknath.73@gmail.com>
Date: Thu, 25 Jul 2024 00:54:47 +0530
Message-ID: <CAKna9VZ=b6f-zei3RY4uiKq7xjt0Ox_oftySPRq8t0YRWDN+4g@mail.gmail.com>
Subject: Partition boundary messed up
To: pgsql-general <pgsql-general@lists.postgresql.org>
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Hello All,
We normally operate on UTC timezone so we normally create partitions in UTC
timezone so that each day partition starts from today's midnight UTC to
next day's midnight UTC. The script looks something like below. And also
that way reference partition tables are also created in a similar way. Say
for example the 29th august partition in parent partition reference to 29th
august child partition as FK. This was working fine even for partition
maintenance(mainly while dropping historical partitions) too without any
issue.

For one of the newly introduced partition tables, by mistake somebody
created the initial partition definition without setting the timezone to
UTC and all the partitions created are in different time zones. And as this
table refers to another partition table (which is the parent and have
partitions created in UTC timezone) the rows are spanning across two
partitions and it's breaking the partition maintenance process while we try
to drop the historical partition.

Now the issue is that the newly introduced table already has billions of
rows pumped into it spanning across 40 partitions. So is there an easy way
to just alter the partition boundary to make it UTC midnight to midnight
range?
or
The only way is to create a new table from scratch with the correct
partition boundary in UTC timezone and then move the data and then create
foreign key on that(which I believe is going to take a lot of time too)?

Another thing we noticed, it shows initial partitions having boundaries in
NON UTC (which we understand because of the missing timezone syntax) but
then suddenly the subsequent partitions are getting created UTC too, not
sure how it happened. And I believe it will create issues while rows come
into the database which falls in between these ranges? Wondering if there
is any easy way to correct this mess now? Note- This is postgres version
15+.

Below partition creation script we use:-
set timesozne='UTC';
SELECT partman.create_parent(
   p_parent_table := 'schema1.tab1',
   p_control := 'TRAN_DATE',
   p_type := 'native',
   p_interval := '1 day',
   p_premake := 90,
   p_start_partition => '2024-02-15 00:00:00'
);
UPDATE partman.part_config SET infinite_time_partitions = 'true' ,
premake=20 WHERE parent_table = 'schema1.tab1';
CALL partman.run_maintenance_proc();

Below details i fetched from  pg_class for the table which is messed up:-

Partition_name       Partition Expressions
TAB1_p2024_08_29 FOR VALUES FROM ('2024-08-29 00:00:00+05:30') TO
('2024-08-30 00:00:00+05:30')
TAB1_p2024_08_30 FOR VALUES FROM ('2024-08-30 00:00:00+05:30') TO
('2024-08-31 00:00:00+05:30')
TAB1_p2024_08_31 FOR VALUES FROM ('2024-08-31 00:00:00+05:30') TO
('2024-09-01 00:00:00+05:30')
TAB1_p2024_09_01 FOR VALUES FROM ('2024-09-01 00:00:00+05:30') TO
('2024-09-02 00:00:00+05:30')

*TAB1_p2024_09_02 FOR VALUES FROM ('2024-09-02 00:00:00+05:30') TO
('2024-09-03 00:00:00+05:30')*
*TAB1_p2024_09_03 FOR VALUES FROM ('2024-09-03 05:30:00+05:30') TO
('2024-09-04 05:30:00+05:30')*TAB1_p2024_09_04 FOR VALUES FROM ('2024-09-04
05:30:00+05:30') TO ('2024-09-05 05:30:00+05:30')
TAB1_p2024_09_05 FOR VALUES FROM ('2024-09-05 05:30:00+05:30') TO
('2024-09-06 05:30:00+05:30')
TAB1_p2024_09_06 FOR VALUES FROM ('2024-09-06 05:30:00+05:30') TO
('2024-09-07 05:30:00+05:30')

Regards
Lok

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<div dir=3D"ltr">Hello All,<br>We normally operate on UTC timezone so we no=
rmally create partitions in UTC timezone so that each day partition starts =
from today&#39;s midnight UTC to next day&#39;s midnight UTC. The script lo=
oks something like below. And also that way reference partition tables are =
also created in a similar way. Say for example the 29th august partition in=
 parent partition reference to 29th august child partition as FK. This was =
working fine even for partition maintenance(mainly while dropping historica=
l partitions) too without any issue.<br><br>For one of the newly introduced=
 partition tables, by mistake somebody created the initial partition defini=
tion without setting the timezone to UTC and all the partitions created are=
 in different time zones. And as this table refers to another partition tab=
le (which is the parent and have partitions created in UTC timezone) the ro=
ws are spanning across two partitions and it&#39;s breaking the partition m=
aintenance process while we try to drop the historical partition.<br><br>No=
w the issue is that the newly introduced table already has billions of rows=
 pumped into it spanning across 40 partitions. So is there an easy way to j=
ust alter the partition boundary to make it UTC midnight to midnight range?=
 <br>or <br>The only way is to create a new table from scratch with the cor=
rect partition boundary in UTC timezone and then move the data and then cre=
ate foreign key on that(which I believe is going to take a lot of time too)=
?<br><br>Another thing we noticed, it shows initial partitions having bound=
aries in NON UTC (which we understand because of the missing timezone synta=
x) but then suddenly the subsequent partitions are getting created UTC too,=
 not sure how it happened. And I believe it will create issues while rows c=
ome into the database which falls in between these ranges? Wondering if the=
re is any easy way to correct this mess now? Note- This is postgres version=
 15+.<div><div><br>Below partition creation script we use:-<div><span style=
=3D"font-family:monospace">set timesozne=3D&#39;UTC&#39;;</span></div><div>=
<font face=3D"monospace">SELECT partman.create_parent(<br>=C2=A0 =C2=A0p_pa=
rent_table :=3D &#39;schema1.tab1&#39;,<br>=C2=A0 =C2=A0p_control :=3D &#39=
;TRAN_DATE&#39;,<br>=C2=A0 =C2=A0p_type :=3D &#39;native&#39;,<br>=C2=A0 =
=C2=A0p_interval :=3D &#39;1 day&#39;,<br>=C2=A0 =C2=A0p_premake :=3D 90,<b=
r>=C2=A0 =C2=A0p_start_partition =3D&gt; &#39;2024-02-15 00:00:00&#39;<br>)=
;<br>UPDATE partman.part_config SET infinite_time_partitions =3D &#39;true&=
#39; , premake=3D20 WHERE parent_table =3D &#39;schema1.tab1&#39;;<br>CALL =
partman.run_maintenance_proc();</font><br><br>Below details i fetched from=
=C2=A0 pg_class for the table which is messed up:-<br><br><font face=3D"mon=
ospace">Partition_name =C2=A0 =C2=A0 =C2=A0 Partition Expressions<br>TAB1_p=
2024_08_29	FOR VALUES FROM (&#39;2024-08-29 00:00:00+05:30&#39;) TO (&#39;2=
024-08-30 00:00:00+05:30&#39;)<br>TAB1_p2024_08_30	FOR VALUES FROM (&#39;20=
24-08-30 00:00:00+05:30&#39;) TO (&#39;2024-08-31 00:00:00+05:30&#39;)<br>T=
AB1_p2024_08_31	FOR VALUES FROM (&#39;2024-08-31 00:00:00+05:30&#39;) TO (&=
#39;2024-09-01 00:00:00+05:30&#39;)<br>TAB1_p2024_09_01	FOR VALUES FROM (&#=
39;2024-09-01 00:00:00+05:30&#39;) TO (&#39;2024-09-02 00:00:00+05:30&#39;)=
<br><b>TAB1_p2024_09_02	FOR VALUES FROM (&#39;2024-09-02 00:00:00+05:30&#39=
;) TO (&#39;2024-09-03 00:00:00+05:30&#39;)<br></b><b>TAB1_p2024_09_03	FOR =
VALUES FROM (&#39;2024-09-03 05:30:00+05:30&#39;) TO (&#39;2024-09-04 05:30=
:00+05:30&#39;)<br></b>TAB1_p2024_09_04	FOR VALUES FROM (&#39;2024-09-04 05=
:30:00+05:30&#39;) TO (&#39;2024-09-05 05:30:00+05:30&#39;)<br>TAB1_p2024_0=
9_05	FOR VALUES FROM (&#39;2024-09-05 05:30:00+05:30&#39;) TO (&#39;2024-09=
-06 05:30:00+05:30&#39;)<br>TAB1_p2024_09_06	FOR VALUES FROM (&#39;2024-09-=
06 05:30:00+05:30&#39;) TO (&#39;2024-09-07 05:30:00+05:30&#39;)</font><br>=
<div><font face=3D"monospace"><br></font></div><div><font face=3D"monospace=
">Regards</font></div><div><font face=3D"monospace">Lok</font></div></div><=
/div></div></div>

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