Subject: Re: create table like: ACCESS METHOD
To: Vik Fearing <vik@postgresfriends.org>,
 Justin Pryzby <pryzby@telsasoft.com>, Simon Riggs <simon@2ndquadrant.com>
Cc: Michael Paquier <michael@paquier.xyz>, pgsql-hackers@postgresql.org,
 Jacob Champion <pchampion@vmware.com>, Heikki Linnakangas <hlinnaka@iki.fi>,
 Ashwin Agrawal <aagrawal@pivotal.io>, Ashutosh Sharma
 <ashu.coek88@gmail.com>, Andres Freund <andres@anarazel.de>,
 Robert Haas <robertmhaas@gmail.com>, Amit Kapila <amit.kapila16@gmail.com>,
 Alvaro Herrera <alvherre@alvh.no-ip.org>
References: <20201209201328.GT24052@telsasoft.com>
 <X+WJqu4X4EniF6xT@paquier.xyz> <20201229230805.GE25152@telsasoft.com>
 <CANP8+j+UihfCrudMprFaTxXFzGw_1W5yHHFSHpRB7xRigOBeww@mail.gmail.com>
 <20210119210331.GN8560@telsasoft.com> <20210323003926.GV4203@telsasoft.com>
 <b6102f5b-0753-3f96-071d-5c2b99795159@postgresfriends.org>
From: Peter Eisentraut <peter.eisentraut@enterprisedb.com>
Message-ID: <8b530d40-1e85-e3b4-774f-b9cb4e2b7ca2@enterprisedb.com>
Date: Thu, 9 Sep 2021 14:30:51 +0200
User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:78.0)
 Gecko/20100101 Thunderbird/78.13.0
MIME-Version: 1.0
In-Reply-To: <b6102f5b-0753-3f96-071d-5c2b99795159@postgresfriends.org>
Content-Type: text/plain; charset=windows-1252; format=flowed
Content-Language: en-US
Content-Transfer-Encoding: 7bit
Archived-At: 
 <https://www.postgresql.org/message-id/8b530d40-1e85-e3b4-774f-b9cb4e2b7ca2%40enterprisedb.com>
Precedence: bulk

On 27.08.21 12:37, Vik Fearing wrote:
> It seems like this should error to me:
> 
> CREATE ACCESS METHOD heapdup TYPE TABLE HANDLER heap_tableam_handler;
> CREATE TABLE likeam1() USING heap;
> CREATE TABLE likeam2() USING heapdup;
> CREATE TABLE likeamlike(
>      LIKE likeam1 INCLUDING ACCESS METHOD,
>      LIKE likeam2 INCLUDING ACCESS METHOD
> );
> 
> At the very least, the documentation should say that the last one wins.

Hmm.  The problem is that the LIKE clause is really a macro that expands 
to the column definitions of the other table.  So there is, so far, no 
such as thing as two LIKE clauses contradicting.  Whereas the access 
method is a table property.  So I don't think this syntax is the right 
approach for this feature.

You might think about something like

CREATE TABLE t2 (...) USING (LIKE t1);

At least in terms of how the syntax should be structured.