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In-Reply-To: <26fe1a14-89aa-415d-a1b1-176526e54d3b@postgrespro.ru>
From: jian he <jian.universality@gmail.com>
Date: Wed, 11 Jun 2025 21:22:22 +0800
Message-ID: 
 <CACJufxE=Qqtku4Ra3mZN-wQgdwyyHcwWN3jE=Wxfpwyd1UHZKQ@mail.gmail.com>
Subject: Re: Add SPLIT PARTITION/MERGE PARTITIONS commands
To: Dmitry Koval <d.koval@postgrespro.ru>
Cc: Junwang Zhao <zhjwpku@gmail.com>, pgsql-hackers@lists.postgresql.org
Content-Type: multipart/mixed; boundary="00000000000031edbf06374bb6d4"
Archived-At: 
 <https://www.postgresql.org/message-id/CACJufxE%3DQqtku4Ra3mZN-wQgdwyyHcwWN3jE%3DWxfpwyd1UHZKQ%40mail.gmail.com>
Precedence: bulk

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Content-Type: text/plain; charset="UTF-8"

hi.

+ /* Copy data from merged partitions to new partition. */
+ moveMergedTablesRows(rel, mergingPartitionsList, newPartRel);
+
+ /* Drop the current partitions before attaching the new one. */
+ foreach_ptr(RelationData, mergingPartition, mergingPartitionsList)
+ {
+ ObjectAddress object;
+
+ /* Get relation id before table_close() call. */
+ object.objectId = RelationGetRelid(mergingPartition);
+ object.classId = RelationRelationId;
+ object.objectSubId = 0;
+
+ /* Keep the lock until commit. */
+ table_close(mergingPartition, NoLock);
+
+ performDeletion(&object, DROP_RESTRICT, 0);
+ }
+ list_free(mergingPartitionsList);
In here, should performDeletion last flags have PERFORM_DELETION_INTERNAL?

also this is not ideal, imagine you first did all the main work in
moveMergedTablesRows,
then suddenly error out, saying:

ERROR:  cannot drop table public.pk_1 because other objects depend on it
DETAIL:  view public.v1 depends on table public.pk_1
HINT:  Use DROP ... CASCADE to drop the dependent objects too.
(this errhint, seems not ideal in this context)

We can perform a preliminary check to determine whether dropping a partition is
allowed, and raise an error if it's not. To do it, I invented a new
function, performDeletionCheck to verify whether an object can be
safely dropped.

please check attached, it was based on v43.

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