Message-ID: <8034d1c6-5f0e-e858-9af9-45d5e246515e@gmail.com>
Date: Tue, 30 Apr 2024 06:00:00 +0300
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Subject: Re: Add SPLIT PARTITION/MERGE PARTITIONS commands
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To: Dmitry Koval <d.koval@postgrespro.ru>,
 Alexander Korotkov <aekorotkov@gmail.com>
Cc: Robert Haas <robertmhaas@gmail.com>,
 PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
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From: Alexander Lakhin <exclusion@gmail.com>
In-Reply-To: <d95dc63f-e805-44bc-8429-9be423293620@postgrespro.ru>
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30.04.2024 03:10, Dmitry Koval wrote:
> Hi!
>
> 1.
> 29.04.2024 21:00, Alexander Lakhin wrote:
>> I still wonder, why that constraint (now with a less questionable name) is
>> created during MERGE?
>
> The SPLIT/MERGE PARTITION(S) commands for creating partitions reuse the existing code of CREATE TABLE .. LIKE ... 
> command. A new partition was created with the name "merge-16385-26BCB0-tmp" (since there was an old partition with the 
> same name). The constraint "merge-16385-26BCB0-tmp_i_not_null" was created too together with the partition. 
> Subsequently, the table was renamed, but the constraint was not.
> Now a new partition is immediately created with the correct name (the old partition is renamed).

Maybe I'm doing something wrong, but the following script:
CREATE TABLE t (i int, PRIMARY KEY(i)) PARTITION BY RANGE (i);
CREATE TABLE tp_0 PARTITION OF t FOR VALUES FROM (0) TO (1);
CREATE TABLE tp_1 PARTITION OF t FOR VALUES FROM (1) TO (2);

CREATE TABLE t2 (LIKE t INCLUDING ALL);
CREATE TABLE tp2 (LIKE tp_0 INCLUDING ALL);
creates tables t2, tp2 without not-null constraints.

But after
ALTER TABLE t MERGE PARTITIONS (tp_0, tp_1) INTO tp_0;
I see:
\d+ tp_0
...
Indexes:
     "tp_0_pkey" PRIMARY KEY, btree (i)
Not-null constraints:
     "tp_0_i_not_null" NOT NULL "i"

Best regards,
Alexander