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Humor me: Postgresql vs. MySql (esp. licensing)

Yes, I know you've seen the above subject before, so please be gentle with
the flamethrowers.

I'm preparing to enter a discussion with management at my company
regarding going forward as either a MySql shop or a Postgresql shop.

It's my opinion that we should be using PG, because of the full ACID
support, and the license involved. A consultant my company hired before
bringing me in is pushing hard for MySql, citing speed and community
support, as well as ACID support.

My biggest concern with MySQL is licensing. We need to keep costs low,
and last I remember the parent company was being pretty strict on "fair
use" under the GPL. If I recall, they even said a company would have to
license the commercial version if it were simply used operationally within
the company.

Also, I was under the impression that Postgresql had pretty much caught up
with MySql in the speed category...is this not the case?

Finally, ACID support in mysql always seemed kind of a hack....perhaps
this has changed?

Thanks for any input (armament ;) ) you can provide.

John

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Nov 12 '05
74 8081
On Wed, Oct 08, 2003 at 09:43:04PM -0500, no***@celery.ts si.com wrote:
If an open transaction is not explicitly committed and the client
disconnects, it is automatically rolled back.


So what would happen with MySQL? Does it leave the transaction
half-committed? The original implication was that data was lost, which
is what would happen with an uncommitted PG transaction as well.


It was not clear to me from the article that originally mentioned it
that it had an uncommitted transaction, though it may very well be the
case.

But given that ROLLBACK takes some unreasonable amount of time in MySQL,
what do you really expect? Did the rollback work when the poweroff was
requested? Or did it work only halfway, rendering the whole
"transactio n" model useless?

A "halfway rollback" would be one of the most stupid things I've heard
about.

--
Alvaro Herrera (<alvherre[a]dcc.uchile.cl>)
"El número de instalaciones de UNIX se ha elevado a 10,
y se espera que este número aumente" (UPM, 1972)

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Nov 12 '05 #21
On Wed, Oct 08, 2003 at 11:45:36AM -0400, Richard Welty wrote:
On Wed, 8 Oct 2003 11:28:00 -0400 (EDT) John Wells <jb@sourceillus trated.com> wrote:
It's my opinion that we should be using PG, because of the full ACID
support, and the license involved. A consultant my company hired before
bringing me in is pushing hard for MySql, citing speed and community
support, as well as ACID support.


you should also cite conformity to standards. MySQL is significantly
different from SQL standards in a number of regards. not that any are fully


I think very nice example is:

SELECT 'a' || 'b';

BTW, MySQL versions without transactions are unusable for 365/7/24
systems, because you cannot make backup of DB without transaction or
redo log.

Karel

--
Karel Zak <za***@zf.jcu.c z>
http://home.zf.jcu.cz/~zakkr/

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Nov 12 '05 #22
no***@celery.ts si.com wrote:
One of my friend lost data with mysql yesterday.. The machine was taken down for
disk upgrade and mysql apperantly did not commit the last insert.. OK he was
using myisam but still..:-)

It sounds like that is more a problem with improper operating protocols
than with the underlying database.


No. Problem is machine was shutdown with shutdown -h. It sends sigterm to
everybody. A good process would flsuh the buffers to disk before finishing.
Mysql didn't on that occasion.

Transactions or not, this behaviour is unacceptable for any serious app.

Would PG know enough to do a commit regardless of how the database was
shut down? A second question is whether doing a commit is what the user
or application would always want to have happen, as it could result in a
half-completed transaction.


Do a shutdown -h on a live database machine with pg. It will gracefully shut
itself down.

Shridhar
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Nov 12 '05 #23
In article <20************ *******@dcc.uch ile.cl>,
Alvaro Herrera <al******@dcc.u chile.cl> writes:
It was not clear to me from the article that originally mentioned it
that it had an uncommitted transaction, though it may very well be the
case.
Sridhar mentioned MyISAM tables - thus no transactions at all.
But given that ROLLBACK takes some unreasonable amount of time in MySQL,
what do you really expect? Did the rollback work when the poweroff was
requested? Or did it work only halfway, rendering the whole
"transactio n" model useless?


Been there, done that. You can kill the MySQL server when it's
rolling back a huge transaction. When you restart it, it just
continues the rollback.
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Nov 12 '05 #24
In article <20************ *******@zf.jcu. cz>,
Karel Zak <za***@zf.jcu.c z> writes:
BTW, MySQL versions without transactions are unusable for 365/7/24
systems, because you cannot make backup of DB without transaction or
redo log.


Huh? People have backed up their MyISAM tables with "mysqlhotco py" or
something like that for ages. This tool locks all tables and can take
a significant amount of time for large databases. Since many people
don't want that, they just create a small replication slave used
exclusively for backup.
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Nov 12 '05 #25

On Thu, Oct 09, 2003 at 01:33:39PM +0200, Harald Fuchs wrote:
In article <20************ *******@zf.jcu. cz>,
Karel Zak <za***@zf.jcu.c z> writes:
BTW, MySQL versions without transactions are unusable for 365/7/24
systems, because you cannot make backup of DB without transaction or
redo log.
Huh? People have backed up their MyISAM tables with "mysqlhotco py" or
something like that for ages. This tool locks all tables and can take

^^^^^
:-) a significant amount of time for large databases. Since many people
don't want that, they just create a small replication slave used
exclusively for backup.


How sure you with integrity of backup without transaction? For example
references between tables...

Karel

--
Karel Zak <za***@zf.jcu.c z>
http://home.zf.jcu.cz/~zakkr/

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Nov 12 '05 #26
On Wed, 2003-10-08 at 16:23, Joshua D. Drake wrote:
Here is the simple thing about MySQL licensing. It is GPL. If you
modify the mySQL source or you link a proprietary app to mySQL without
a commercial license. You must distrubute your changes and or
application as GPL or GPL compatibile.


You have two contradictory statements here, which unfortunately
represent the internal contradictions in MySQL's license (at least,
those versions after version 3.23.19, when MySQL AB adopted the current
licensing scheme).

Certainly, if MySQL is licensed under the GPL, you must distribute or
make available source code to any changed version of MySQL that you
distribute, or any other derivative works of MySQL that you distribute.
However, MySQL's stated license makes far greater requirements on those
who use MySQL.

Even though many distributors of MySQL, including the normally very
license-conscious Debian GNU/Linux, include only the GPL as its license,
there are in fact additional constraints which limit the rights that are
given by the GPL. MySQL AB's license information web page [1] includes
in plain language what their intent is, and that intent is not the GPL,
nor is it compatible with the GPL.

The non-commercial (free-of-charge) MySQL license extends the
requirement to make available source code to "your application",
regardless of whether or not your application is a derived work of
MySQL. All practical interpretations of the GPL, including the FSF's,
exclude from the requirement to distribute source code any works that
are collected by "simple aggregation", meaning they are present on the
same distribution medium or in the same distribution package as the
licensed work, but are not related to the licensed work by the sharing
of licensed components. MySQL does not distinguish between derivative
works of MySQL and those that are collected along with it by simple
aggregation.

So, for example, if I wish to sell a version of Debian with a
proprietary, closed-source installation tool (which does not use or
relate to MySQL in any way) and I wish to also include MySQL and its
source code in my distribution, I am required to get a commercial
license from MySQL. That is not consistent with the terms of the GPL
under which I received MySQL from Debian.

I don't know how to put it more plainly than that. Even though MySQL AB
claims that their product is licensed under the GPL, it is not, because
they put significant additional license terms on it that remove some
rights given by the GPL. The overall license terms of MySQL do not
meet any standard of "Free software" licenses that I know, including the
Debian Free Software Guidelines [2]. I believe that Debian and other
GNU/Linux distributions should move MySQL to their non-free sections,
along with other software that is "free for non-commercial use".

The consequences for any commercial enterprise using MySQL in any way
must be very closely examined, and certainly aren't obvious in the way
that the consequences of the GPL are obvious.

Thanks,
Bill Gribble

[1] http://www.mysql.com/products/licensing.html
[2] http://www.debian.org/social_contract#guidelines




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Nov 12 '05 #27
On Thu, 9 Oct 2003 01:28, John Wells wrote:
Yes, I know you've seen the above subject before, so please be gentle with
the flamethrowers.

I'm preparing to enter a discussion with management at my company
regarding going forward as either a MySql shop or a Postgresql shop.

It's my opinion that we should be using PG, because of the full ACID
support, and the license involved. A consultant my company hired before
bringing me in is pushing hard for MySql, citing speed and community
support, as well as ACID support.


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Nov 12 '05 #28
>>>>> "OE" == Oliver Elphick <ol**@lfix.co.u k> writes:

OE> MySQL's licence does not require you to buy a licence for _any_
OE> commercial use, but only for commercial use where you do not release
OE> your source code under a GPL-compatible licence.

So if I write my application in python, say, and only relase the .pyc
files, I'm not linked to mysql, but I use it via the API provided by
the python runtime. The GPL does not require me to release the source
code to my application, yet I'm using mysql in a commercial setting.
I believe that mysql will demand a license fee from me in this
situation.

It is very murky with mysql.

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Nov 12 '05 #29
> > It sounds like that is more a problem with improper operating protocols
than with the underlying database.
No. Problem is machine was shutdown with shutdown -h. It sends sigterm to
everybody. A good process would flsuh the buffers to disk before finishing.
Mysql didn't on that occasion.

Transactions or not, this behaviour is unacceptable for any serious app.
True, but was it because the shutdown scripts weren't set up properly
or does MySQL just not handle the 'kill' properly? (I would consider the
latter a serious bug.)

I still fault the operations protocol, part of what should be done in
setting up a production shop is testing various shutdown options, and it
sounds like that wasn't done in advance or they would have known to build
in extra steps for shutting down MySQL.
Do a shutdown -h on a live database machine with pg. It will gracefully shut
itself down.


Is that true for all OS flavors and is it dependent upon the DBA having
set up proper shutdown scripts?

I'm not trying to be argumentative here or defending MySQL, just noting
that a shutdown process that isn't tested can cause problems even with
commercial databases. And as someone who has to put up with MySQL on
occasion, I'm always looking for problem areas for the DBA.
--
Mike Nolan

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Nov 12 '05 #30

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