Re: Not able to purge partition

----- Mail original -----
> De: "Laurenz Albe" <laurenz(dot)albe(at)cybertec(dot)at>
> À: "veem v" <veema0000(at)gmail(dot)com>, "pgsql-general" <pgsql-general(at)lists(dot)postgresql(dot)org>
> Envoyé: Jeudi 21 Mars 2024 13:48:19
> Objet: Re: Not able to purge partition

> On Thu, 2024-03-21 at 11:07 +0530, veem v wrote:
>> CREATE TABLE schema1.test_part_drop_parent
>> (
>>  c1 varchar(36)  NOT NULL ,
>>  c2_part_date timestamp with time zone  NOT NULL ,
>>  c3  numeric(12,0)  NOT NULL ,
>>  CONSTRAINT test_part_drop_parent_PK PRIMARY KEY (c1,c2_part_date)
>> ) PARTITION BY RANGE (c2_part_date);
>>
>> CREATE INDEX idx1_test_part_parent ON schema1.test_part_drop_parent( C3 ASC);
>>
>>
>> CREATE TABLE schema1.test_part_drop_child
>> (
>>  C1_child   varchar(36)  NOT NULL ,
>>  C1   varchar(36)  NOT NULL ,
>>  c2_part_date timestamp with time zone  NOT NULL ,
>>  C3  numeric(12,0)  NOT NULL ,
>>  CONSTRAINT test_part_drop_child_PK PRIMARY KEY (C1_child,c2_part_date),
>>  CONSTRAINT test_part_drop_child_FK1 FOREIGN KEY (C1,c2_part_date) REFERENCES
>>  schema1.test_part_drop_parent(c1,c2_part_date)
>> ) PARTITION BY RANGE (c2_part_date);
>>
>> CREATE INDEX test_part_drop_child_fk ON schema1.test_part_drop_child( c1,
>> c2_part_date);
>>
>> CREATE INDEX test_part_drop_child_idx ON schema1.test_part_drop_child( c1_child,
>> c2_part_date);
>>
>> [create some partitions, then drop a partition of the referenced table]
>>
>
>> SQL Error [P0001]: ERROR: cannot drop table
>> schema1.test_part_drop_parent_p2024_02_01 because other objects depend on it
>> CONTEXT: SQL statement "DROP TABLE schema1.test_part_drop_parent_p2024_02_01"
>
> That's normal. If you create a foreign key constraint to a partitioned table,
> you
> can no longer drop a partition of the referenced table.
>
> What you *can* do is detach the partition and then drop it, but detatching will
> be slow because PostgreSQL has to check for referencing rows.
>
> The best solution is to create the foreign key *not* between the partitioned
> tables, but between the individual table partitions. That should be easy if
> you have the same partition boundaries for both.
> Then you can simply drop a partition from both tables at the same time.
>
> Yours,
> Laurenz Albe
> --
> Cybertec | https://www.cybertec-postgresql.com

Also, as an aside, test_part_drop_child_idx index is redundant with test_part_drop_child_pk index created for the primary key

Regards
Gilles