Date: Fri, 19 Aug 2022 15:16:32 -0400
From: Bruce Momjian <bruce@momjian.us>
To: Peter Geoghegan <pg@bowt.ie>
Cc: Tom Lane <tgl@sss.pgh.pa.us>, Alvaro Herrera <alvherre@alvh.no-ip.org>,
	shangzi.x@columbia.edu, Pg Docs <pgsql-docs@lists.postgresql.org>
Subject: Re: relpages in pg_class
Message-ID: <Yv/hkEf1fFDIGl6m@momjian.us>
References: <20220819160133.l2m47puqpjzk3mrh@alvherre.pgsql>
 <3203690.1660927195@sss.pgh.pa.us>
 <CAH2-Wz=xFBK69PiXo8aFQhDYvKqVtaVTQfS+LD1aAtacbPfh=w@mail.gmail.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: 
 <CAH2-Wz=xFBK69PiXo8aFQhDYvKqVtaVTQfS+LD1aAtacbPfh=w@mail.gmail.com>
Archived-At: 
 <https://www.postgresql.org/message-id/Yv/hkEf1fFDIGl6m%40momjian.us>
Precedence: bulk

On Fri, Aug 19, 2022 at 11:25:52AM -0700, Peter Geoghegan wrote:
> On Fri, Aug 19, 2022 at 9:40 AM Tom Lane <tgl@sss.pgh.pa.us> wrote:
> > Yeah, we use "blocks" and "pages" interchangeably, which is something
> > I don't feel a need to change; but evidently the OP didn't realize that.
> > This is a job for the glossary, perhaps?
> 
> I think that they're synonyms that can often (but not always) be used
> interchangeably. I *think* that this understanding is shared by other
> people, though I should check. Here goes:
> 
> To me, "block" emphasizes on-disk/relfilenode storage. Something that
> exists at a particular physical offset in a particular file (a
> BlockNumber + relfilenode). On the other hand, the term "page"
> emphasizes the in-memory format, and the indirection provided by the
> bufpage.c slotted page format (i.e. line pointer array indirection).

Yes, I have heard the block-disk, page-memory explanation before.

-- 
  Bruce Momjian  <bruce@momjian.us>        https://momjian.us
  EDB                                      https://enterprisedb.com

  Indecision is a decision.  Inaction is an action.  Mark Batterson