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On Mon, 17 Dec 2007 10:34:37 -0800, pan wrote:
> "Jim Henderson" <nos### [at] nospam com> wrote in message
> news:4766b26e$1@news.povray.org...
>> On Mon, 17 Dec 2007 16:33:54 +0000, Orchid XP v7 wrote:
>>
>>> Gail Shaw wrote:
>>>
>>>> University != experience.
>>>
>>> True. But my point is that I'm not entirely clueless about what
>>> databases are and how they work. I actually know stuff about this
>>> stuff.
>>>
>>>> You say that as if you're the only person here who did database
>>>> courses at university. You're not.
>>>
>>> I just object to being told I know nothing about databases when
>>> actually
>>> I do. I don't claim to be a world-renound expert, but I do know
>>> *something*.
>>
>> Hey, Orchid's got teeth! :-)
>>
>>
>
> So did Audrey (II); friend of Orin Scrivello, DDS.
[...]
My point here is that he's actually stood up and said "now wait just a
damned minute" - something that he has needed to do for a while. I don't
disagree with anything you said about the qualifications, theory and
reality are two entirely different things. But it's good that he's taken
the chance to stand up and say something forceful rather than to just say
"oh, OK, I guess I'm dumb" and slink off into the darkness.
It takes practice to stand up and do that. It takes experience to know
when it's the right thing to do, and that's something that comes with
time.
So I still say "well done!"
Jim
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"Orchid XP v7" <voi### [at] devnull> wrote in message
news:4766a720@news.povray.org...
>
> Personally I prefer Oracle's lockless multiversion system - although
> obviously that has its own set of drawbacks.
Yup. Storage/memory
SQL's got that now too. I considered switching one of my main apps over to
use version store rather than locking, but I didn't have a compelling reason
to do so.
Locking is a minimal overhead when transactions are kept short.
> --
> http://blog.orphi.me.uk/
> http://www.zazzle.com/MathematicalOrchid*
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"Orchid XP v7" <voi### [at] devnull> wrote in message
news:4766a681$1@news.povray.org...
> Gilles Tran wrote:
> > and keep having these
> > far-out opinions about things you are visibly ignorant about?
>
> I see. So thinking that transactions matter is "far-out" and "visibly
> ingorant"?
No, but saying that transactions are essential and anything that doesn't
implement them is a toy, on the other hand....
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"Orchid XP v7" <voi### [at] devnull> wrote in message
news:4766a4d1$1@news.povray.org...
> Gail Shaw wrote:
>
> > University != experience.
>
> True. But my point is that I'm not entirely clueless about what
> databases are and how they work. I actually know stuff about this stuff.
>
Yup. You know the theory. In practice however things are sometimes done
differently. Not because theory is wrong, but because sometimes shortcuts
are necessary.
In theory, you want to prevent any form of data anomaly from multiple
accesses. In reality, that often reduces concurrency to unacceptable levels,
so some possible anomolies are accepted to get higher throughput (probably
50% of the select statements done in my largest system use the read
uncommitted isolation level)
In theory, all tables should be at least 3rd normal form of Boyce-Codd
normal form. In reality, you will get tables that are intentionally in 1st
or 2nd normal form.
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"Orchid XP v7" <voi### [at] devnull> wrote in message
news:4766a720@news.povray.org...
> Personally I prefer Oracle's lockless multiversion system - although
> obviously that has its own set of drawbacks.
oh, btw, Oracle also uses locks.
http://download.oracle.com/docs/cd/B28359_01/server.111/b28318/consist.htm#i
5704
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Orchid XP v7 wrote:
> I just object to being told I know nothing about databases when actually
> I do. I don't claim to be a world-renound expert, but I do know
> *something*.
Nobody is claiming you know nothing. We're just claiming that you're
making incorrect claims about database systems that are easily checked,
and then basing vehement opinions on said incorrect information.
--
Darren New / San Diego, CA, USA (PST)
It's not feature creep if you put it
at the end and adjust the release date.
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Jim Henderson wrote:
> My point here is that he's actually stood up and said "now wait just a
> damned minute" - something that he has needed to do for a while.
Does that make him a triffid? ;-)
> So I still say "well done!"
True. :-)
--
Darren New / San Diego, CA, USA (PST)
It's not feature creep if you put it
at the end and adjust the release date.
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Gail Shaw wrote:
> In theory, you want to prevent any form of data anomaly from multiple
> accesses.
Or, in my examples, you only have one writer, and that writer is doing
atomic writes, and no reader looks at multiple records in one
transaction. So what's there to transactionify?
I have another table, where I have multiple processes going thru it,
doing what it says to do, each step taking maybe 10-30 seconds. Rather
than using a transactional table, I do things like
SELECT * from to_do where state = 3 limit 10
then for each of those rows, I do
UPDATE to_do SET state=4 WHERE id=$id AND state = 3
then I check if the num_rows_affected > 0, and if so, I know I'm the one
that changed that row. Just as an example. If the rows affected was
zero, someone else changed that specific ID.
A bit kludgey, I'll admit, but better than holding a transactional lock
on the table for 30 seconds at a time.
--
Darren New / San Diego, CA, USA (PST)
It's not feature creep if you put it
at the end and adjust the release date.
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Orchid XP v7 wrote:
> I see. So thinking that transactions matter is "far-out" and "visibly
> ingorant"?
No. Insisting that MySql is a toy that doesn't have them, even after
being told your information is long out of date, is "visibly ignorant". :-)
> Um... I did? [At least, I read the MySQL manual, and spent some time
> using it.]
And you missed the part about multiple users and the "Begin transaction"
statement?
> When somebody says "oh yeah, transactions aren't really all that
> important"
We said "they're not always important", not that they're not really
important.
--
Darren New / San Diego, CA, USA (PST)
It's not feature creep if you put it
at the end and adjust the release date.
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Orchid XP v7 wrote:
> Personally I prefer Oracle's lockless multiversion system - although
> obviously that has its own set of drawbacks.
There's also optimistic locking. I think MySql implements a number of
these techniques, depending on what you ask for. There are anumber of
levels of isolation in standard sql, which mysql implement.
--
Darren New / San Diego, CA, USA (PST)
It's not feature creep if you put it
at the end and adjust the release date.
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