Message-ID: <84ada05b-be5c-473e-6d1c-ebe5dd21b190@gmail.com>
Date: Fri, 19 Apr 2024 12:00:00 +0300
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Subject: Re: Add SPLIT PARTITION/MERGE PARTITIONS commands
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To: Alvaro Herrera <alvherre@alvh.no-ip.org>
Cc: Alexander Korotkov <aekorotkov@gmail.com>,
 Dmitry Koval <d.koval@postgrespro.ru>, Robert Haas <robertmhaas@gmail.com>,
 PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>,
 =?UTF-8?Q?Dagfinn_Ilmari_Manns=c3=a5ker?= <ilmari@ilmari.org>
References: <202404181749.2jibl7x2ao5n@alvherre.pgsql>
From: Alexander Lakhin <exclusion@gmail.com>
In-Reply-To: <202404181749.2jibl7x2ao5n@alvherre.pgsql>
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18.04.2024 20:49, Alvaro Herrera wrote:
> On 2024-Apr-18, Alexander Lakhin wrote:
>
>> I think the feature implementation should also provide tab completion
>> for SPLIT/MERGE.
> I don't think that we should be imposing on feature authors or
> committers the task of filling in tab-completion for whatever features
> they contribute.  I mean, if they want to add that, cool; but if not,
> somebody else can do that, too.  It's not a critical piece.

I agree, I just wanted to note the lack of the current implementation.
But now, thanks to Dagfinn, we have the tab completion too.

I have also a question regarding "ALTER TABLE ... SET ACCESS METHOD". The
current documentation says:
When applied to a partitioned table, there is no data to rewrite, but
partitions created afterwards will default to the given access method
unless overridden by a USING clause.

But MERGE/SPLIT behave differently (if one can assume that MERGE/SPLIT
create new partitions under the hood):
CREATE ACCESS METHOD heap2 TYPE TABLE HANDLER heap_tableam_handler;

CREATE TABLE t (i int, PRIMARY KEY(i)) PARTITION BY RANGE (i);
ALTER TABLE t SET ACCESS METHOD heap2;
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);
\d t+
                                       Partitioned table "public.t"
...
Access method: heap2

                                           Table "public.tp_0"
...
Access method: heap2

                                           Table "public.tp_1"
...
Access method: heap2

ALTER TABLE t MERGE PARTITIONS (tp_0, tp_1) INTO tp_0;
                                       Partitioned table "public.t"
...
Access method: heap2

                                           Table "public.tp_0"
...
Access method: heap

Shouldn't it be changed, what do you think?

Best regards,
Alexander