Re: Is my MySQL Gaining ? - Mailing list pgsql-general

On Tue, 30 Dec 2003, Tom Lane wrote:

> Date: Tue, 30 Dec 2003 02:07:23 -0500
> From: Tom Lane <tgl@sss.pgh.pa.us>
> To: Bret Busby <bret@busby.net>
> Cc: pgsql-advocay@postgresql.org, pgsql-general@postgresql.org
> Subject: Re: [GENERAL] Is my MySQL Gaining ?
>
> Bret Busby <bret@busby.net> writes:
> > Does PostgreSQL yet allow the user or programmer, to determine where the
> > database will be stored?
>
> You speak as though you think that would be a good idea.
>
> In my mind, "where the database is stored" is not a matter for users,
> nor for programmers, but for DBAs --- that is, the grunts who have to
> worry about backup policies and suchlike.  This is not an issue that
> should be exposed at the SQL-command level, and therefore it does not
> concern either users or database programmers.
>
> That's not to say that we don't have work to do here.  There's
> considerable interest in developing "tablespace" features to help the
> DBA manage his problems.  But I absolutely will not buy into any
> suggestion that user foo's tables must be stored in user foo's home
> directory (even if I thought that Postgres user foo must correspond
> to a local Unix user foo ... which I don't ...)
>
>             regards, tom lane
>
>

This is where terminology becomes amusing.

I meant the OS user, not the DBMS user, and I am not suggesting that
DBMS users should be able to set where their tables are stored.

All kinds of scenarios can arise; where the DBA and the developer are
the same person, or, employed in the same department of the same
company; where the DBA is employed by the company, and the developer is
a contractor, or an employee of a contractor, and, as I previosuly
mentioned, the scenario where an ISP, by hosting a web site with a
database backend, has a database in the same holding area as is held all
the databases of all of the ISP's clients who similarly have web sites
with database backends.

I would feel more confident about having a personal database "on the
Internet"; a backend to my web site, if I knew that the database wasn't
thrown into the same storage area as everyone of the ISP's other account
holders, who also have the same DBMS database backends to their web
sites. You never know what else is sharing the same storage area, or how
safe your database is in there. It is a bit like having a cat; I would
rather that the cat is with me, and that I know where it is, and what is
happening with the cat, than having the cat locked away in a common room
for all cats. Also, using that analogy, if I decide to move away with my
cat, if it is with me, it is much simpler, and, cleaner, for me to
simply pick up the cat and take it with me, than to try to find all of
its bits, in a common room full of other cats. If I have a database
system hosted by an ISP, and I try to move it to another ISP, surely, it
would be simpler and cleaner, if I know that the database is stored in
or under my home directory with the ISP, than having the database stored
in a central repository with all of the other accounts holders'
databases.

There is also the issue of security, in the same context; I would feel
much more secure, with a database hosted by an ISP, if I could control
the privileges on the database directory, rather than allowing the ISP
the control. Having been a user on various UNIX systems, I have seen
some pretty lax security by systems administrators, and other users, and
I am reminded of a senior university computing lecturer, who had the
exam for an advanced computing unit, with such lax security that some
students wandering through the system, found the exam, and, when they
sat the exam, were surprisingly well prepared (no, I was not one of the
students), resulting in all the students in the unit, having to re-sit
the exam, and, other effects. A DBA should be able to control where a
database is stored, and the level of security applicable to where the
database is stored (privileges applicable to the directory, etc), and,
as I have previously mentioned, it can occur that the DBA and the
developer/programmer, are the same person.

As an example, on a personal basis, if I ever get the number of names in
my genealogy system, up to around 10,000, I would really want, if using
a database backend (which would, I believe, be required), to have
control over where the data is stored, so that I can easily and reliably
back it up, as such data can be unreplaceable, and can take decades to
accumulate.

Similarly, for commercial databases, now that DVD's are writable,
backing up a largish database, using OS backing up, would be much
better, and moreso, witth the data for a database, stored where it is
wanted.

I am not sure whether it can all be done with symbolic links, to place
PostgreSQL databases where a (OS, not DBMS) user or developer or DBA
wants them to be stored, but I suggest that provision should exist for a
person to determine where the person's (as owner of the database)
database file(s) exist, for security, backing up, etc.

--
Bret Busby
Armadale
West Australia
..............

"So once you do know what the question actually is,
 you'll know what the answer means."
- Deep Thought,
  Chapter 28 of
  "The Hitchhiker's Guide to the Galaxy:
  A Trilogy In Four Parts",
  written by Douglas Adams,
  published by Pan Books, 1992
....................................................