Re: the concept of a database cluster

Paul Weiss <[email protected]> Sat, 4 Jan 2020 09:58:57 +0000
Newsgroups gmane.comp.db.postgresql.devel.documentation
Message-ID <MWHPR15MB18397BC83DBD850FB8A2327CDC220@MWHPR15MB1839.namprd15.prod.outlook.com>
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Oh, I didn't mean to imply that I am confused. It is clear that there are t=
wo concepts here, sharing a term. I was trying to communicate that the manu=
al 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 "de=
lete the folder containing the databases", or "drop the databases". Those a=
ctions are not identical. I would think we would want to be clear to our us=
ers which we mean.

Paul

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

On Thursday, January 2, 2020, PG Doc comments form <[email protected]<=
mailto:[email protected]>> wrote:
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.

A garage is a =93car storage area for a house=94. 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 databas=
es stored in the cluster are managed by a single shared instance.  You will=
 need to better explain your confusion because the documentation is describ=
ing a complex system accurately but in parts that are related - two sides o=
f the same coin, if you will.

David J.


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Oh, I didn't mean to imply that I am confused. It is clear that there are t=
wo concepts here, sharing a term. I was trying to communicate that the manu=
al does not always make it immediately clear from context which concept is =
meant in a particular sentence.</div>
<div style=3D"font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;=
 color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);">
<br>
</div>
<div style=3D"font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;=
 color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);">
A garage is a good analogy. A garage is a container for cars rather than a =
collection of cars. You wouldn't say &quot;I sold my garage&quot; to mean &=
quot;I sold my car collection&quot;. Containers and collections are differe=
nt things.</div>
<div style=3D"font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;=
 color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);">
<br>
</div>
<div style=3D"font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;=
 color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);">
Here's a simple example In our context: &quot;remove the cluster&quot; coul=
d mean &quot;delete the folder containing the databases&quot;, or &quot;dro=
p the databases&quot;. Those actions are not identical. I would think we wo=
uld want to be clear to our users which we mean.</div>
<div style=3D"font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;=
 color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);">
<br>
</div>
<div style=3D"font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;=
 color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);">
Paul</div>
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<div id=3D"appendonsend"></div>
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 color: rgb(0, 0, 0);">
<br>
</div>
<hr tabindex=3D"-1" style=3D"display:inline-block; width:98%">
<div id=3D"divRplyFwdMsg" dir=3D"ltr"><font face=3D"Calibri, sans-serif" co=
lor=3D"#000000" style=3D"font-size: 11pt;" data-ogsc=3D""><b>From:</b> Davi=
d G. Johnston &lt;[email protected]&gt;<br>
<b>Sent:</b> Friday, January 3, 2020 12:21 AM<br>
<b>To:</b> [email protected] &lt;[email protected]&gt;; pgsql-docs@lists.=
postgresql.org &lt;[email protected]&gt;<br>
<b>Subject:</b> Re: the concept of a database cluster</font>
<div>&nbsp;</div>
</div>
<div>On Thursday, January 2, 2020, PG Doc comments form &lt;<a href=3D"mail=
to:[email protected]" style=3D"">[email protected]</a>&gt; wrote:=
<br>
<blockquote class=3D"x_gmail_quote" style=3D"margin:0 0 0 .8ex; border-left=
:1px #ccc solid; padding-left:1ex">
The following documentation comment has been logged on the website:<br>
<br>
Page: <a href=3D"https://www.postgresql.org/docs/12/creating-cluster.html" =
target=3D"_blank" style=3D"">
https://www.postgresql.org/<wbr>docs/12/creating-cluster.html</a><br>
Description:<br>
<br>
In 18.2, a database cluster is said to be &quot;a database storage area on =
disk&quot;,<br>
and then shortly afterward is is defined as &quot;a collection of databases=
 that<br>
is managed by a single instance of a running database server&quot;. Those s=
eem<br>
very different things. Sometimes in the manual I can't tell which usage is<=
br>
intended.<br>
</blockquote>
<div><br>
</div>
<div>A garage is a =93car storage area for a house=94. A garage can (typica=
lly) store multiple cars just as a database cluster can store multiple data=
bases.&nbsp; The files are only useful if there is a running instance and a=
ll databases stored in the cluster are managed
 by a single shared instance.&nbsp; You will need to better explain your co=
nfusion because the documentation is describing a complex system accurately=
 but in parts that are related - two sides of the same coin, if you will.</=
div>
<div><br>
</div>
<div>David J.</div>
<div><br>
</div>
</div>
</div>
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