Date: Mon, 6 May 2019 11:22:51 -0500
From: Justin Pryzby <pryzby@telsasoft.com>
To: Rafia Sabih <rafia.pghackers@gmail.com>
Cc: PostgreSQL-development <pgsql-hackers@postgresql.org>
Subject: Re: make \d pg_toast.foo show its indices ; and, \d toast show its
 main table
Message-ID: <20190506162251.GN3925@telsasoft.com>
References: <20190422154902.GH14223@telsasoft.com>
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 <20190503142721.GC3925@telsasoft.com>
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On Mon, May 06, 2019 at 09:13:52AM +0200, Rafia Sabih wrote:
> On Fri, 3 May 2019 at 16:27, Justin Pryzby <pryzby@telsasoft.com> wrote:
> >
> > On Fri, May 03, 2019 at 02:55:47PM +0200, Rafia Sabih wrote:
> > > On Mon, 22 Apr 2019 at 17:49, Justin Pryzby <pryzby@telsasoft.com> wrote:
> > > >
> > > > It's deliberate that \dt doesn't show toast tables.
> > > > \d shows them, but doesn't show their indices.
> > > >
> > > > It seems to me that their indices should be shown, without having to think and
> > > > know to query pg_index.
> > > >
> > > > postgres=# \d pg_toast.pg_toast_2600
> > > > TOAST table "pg_toast.pg_toast_2600"
> > > >    Column   |  Type
> > > > ------------+---------
> > > >  chunk_id   | oid
> > > >  chunk_seq  | integer
> > > >  chunk_data | bytea
> > > > Indexes:
> > > >     "pg_toast_2600_index" PRIMARY KEY, btree (chunk_id, chunk_seq)
> > >
> > > +1.
> >
> > Thanks - what about also showing the associated non-toast table ?
> >
> IMHO, what makes more sense is to show the name of associated toast
> table in the \dt+ of the normal table.

Perhaps ... but TOAST is an implementation detail, and I think it should rarely
be important to know the toast table for a given table.

I think it's more useful to go the other way (at least), to answer questions
when pg_toast.* table shows up in a query like these:

 - SELECT relpages, relname FROM pg_class ORDER BY 1 DESC;
 - SELECT COUNT(1), relname FROM pg_class c JOIN pg_buffercache b ON b.relfilenode=c.oid GROUP BY 2 ORDER BY 1 DESC LIMIT 9;

Justin