Subject: the concept of a database cluster

From: PG Doc comments form <[email-masked]>
Date: Fri, 03 Jan 2020 01:07:14 +0000

The following documentation comment has been logged on the website:

Page: https://www.postgresql.org/docs/12/creating-cluster.html
Description:

In 18.2, a database cluster is said to be "a database storage area on disk",
and then shortly afterward is is defined as "a collection of databases that
is managed by a single instance of a running database server". Those seem
very different things. Sometimes in the manual I can't tell which usage is
intended.

---

From: "David G. Johnston" <[email-masked]>
Date: Fri, 3 Jan 2020 01:21:05 -0700

> very different things. Sometimes in the manual I can't tell which usage is

A garage is a “car storage area for a house”. A garage can (typically)
store multiple cars just as a database cluster can store multiple
databases.  The files are only useful if there is a running instance and
all databases stored in the cluster are managed by a single shared
instance.  You will need to better explain your confusion because the
documentation is describing a complex system accurately but in parts that
are related - two sides of the same coin, if you will.

David J.

---

From: Paul Weiss <[email-masked]>
Date: Sat, 4 Jan 2020 09:58:57 +0000

Oh, I didn't mean to imply that I am confused. It is clear that there are two concepts here, sharing a term. I was trying to communicate that the manual does not always make it immediately clear from context which concept is meant in a particular sentence.

A garage is a good analogy. A garage is a container for cars rather than a collection of cars. You wouldn't say "I sold my garage" to mean "I sold my car collection". Containers and collections are different things.

Here's a simple example In our context: "remove the cluster" could mean "delete the folder containing the databases", or "drop the databases". Those actions are not identical. I would think we would want to be clear to our users which we mean.

Paul

________________________________
From: David G. Johnston <[email-masked]>
Sent: Friday, January 3, 2020 12:21 AM
To: [email-masked] <[email-masked]>; [email-masked] <[email-masked]>
Subject: Re: the concept of a database cluster

On Thursday, January 2, 2020, PG Doc comments form <[email-masked]<mailto:[email-masked]>> wrote:
The following documentation comment has been logged on the website:

A garage is a “car storage area for a house”. A garage can (typically) store multiple cars just as a database cluster can store multiple databases.  The files are only useful if there is a running instance and all databases stored in the cluster are managed by a single shared instance.  You will need to better explain your confusion because the documentation is describing a complex system accurately but in parts that are related - two sides of the same coin, if you will.

David J.

---

From: "David G. Johnston" <[email-masked]>
Date: Sat, 4 Jan 2020 09:11:56 -0700

On Saturday, January 4, 2020, Paul Weiss <[email-masked]> wrote:

> Oh, I didn't mean to imply that I am confused. It is clear that there are
> two concepts here, sharing a term. I was trying to communicate that the
> manual does not always make it immediately clear from context which concept
> is meant in a particular sentence.
>
> A garage is a good analogy. A garage is a container for cars rather than a
> collection of cars. You wouldn't say "I sold my garage" to mean "I sold my
> car collection". Containers and collections are different things.
>
> Here's a simple example In our context: "remove the cluster" could mean
> "delete the folder containing the databases", or "drop the databases".
> Those actions are not identical. I would think we would want to be clear to
> our users which we mean.
>

I’m sure we’d be willing to fix concrete problematic examples but a lack of
those suggests there is no actual problem here...as you aren’t confused or
providing concrete examples and suggestions I have no idea what you are
trying to accomplish with this thread.  Awareness of what seems to be a
non-existent issue?

David J.