Subject: Re: Psql patch to show access methods info
To: s.cherkashin@postgrespro.ru, Alvaro Herrera <alvherre@2ndquadrant.com>
Cc: Michael Paquier <michael@paquier.xyz>,
 Nikita Glukhov <n.gluhov@postgrespro.ru>, pgsql-hackers@postgresql.org
References: <20181120104153.mgl5qy6uowryhesn@alvherre.pgsql>
 <64178681578cd2f1013db32bb7c00ddd@postgrespro.ru>
From: Arthur Zakirov <a.zakirov@postgrespro.ru>
Message-ID: <c94f871f-12e5-304e-a6b1-08eab7a94187@postgrespro.ru>
Date: Tue, 20 Nov 2018 17:32:57 +0300
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Hello,

On 20.11.2018 16:08, s.cherkashin@postgrespro.ru wrote:
> Ok, I fixed this.

I looked at the patch. It is in good shape. It compiles and tests are 
passed.

I have few a questions related with throwing errors. They might be silly :)

\dAp as well as \dA command throw an error if a server's version below 9.6:

"The server (version %s) does not support access methods"

But other \dA commands don't. It seems that there is enough information 
in catalog for servers below 9.6. That is there are pg_am, pg_opfamily, 
pg_amop and other catalog tables related with access methods.

\dAp calls pg_indexam_has_property() function, which doesn't exist in 
servers 9.5 and below. Is this the reason that it throws an error? If so 
then describeOneIndexColumnProperties() also should throw an error, 
because it calls pg_index_column_has_property() function, which doesn't 
exist in servers 9.5 and below.

What do you think?

-- 
Arthur Zakirov
Postgres Professional: http://www.postgrespro.com
Russian Postgres Company