Re: Add A Glossary

On 2020-May-17, Jürgen Purtz wrote:

> On 15.05.20 02:00, Alvaro Herrera wrote:
> > Thanks everybody. I have compiled together all the suggestions and the
> > result is in the attached patch. Some of it is of my own devising.
> >
> > * I changed "instance", and made "cluster" be mostly a synonym of that.
> In my understanding, "instance" and "cluster" should be different things,
> not only synonyms. "instance" can be the term for permanently fluctuating
> objects (processes and RAM) and "cluster" can denote the more static objects
> (directories and files). What do you think? If you agree, I would create a
> patch.

I don't think that's the general understanding of those terms. For all
I know, they *are* synonyms, and there's no specific term for "the
fluctuating objects" as you call them. The instance is either running
(in which case there are processes and RAM) or it isn't.

> > * I removed "global SQL object" and made "SQL object" explain it.
> +1., but see the (huge) different spellings in patch.

This seems a misunderstanding of what "local" means. Any object that
exists in a database is local, regardless of whether it exists in a
schema or not. "Extensions" is one type of object that does not belong
in a schema. "Foreign data wrapper" is another type of object that does
not belong in a schema. Same with data type casts. They are *not*
global objects.

> bloat: changed 'current row' to 'relevant row' because not only the youngest
> one is relevant (non-bloat).

Hm. TBH I'm not sure of this term at all. I think we sometimes use the
term "bloat" to talk about the dead rows only, ignoring the free space.

> data type casts: Are you sure that they are global? In pg_cast 'relisshared'
> is 'false'.

I'm not saying they're global. I'm saying they're outside schemas.
Maybe this definition needs more rewording, if this bit is unclear.

--
Álvaro Herrera https://www.2ndQuadrant.com/
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