Re: Using EO
Re: Using EO
- Subject: Re: Using EO
- From: Sacha Mallais <email@hidden>
- Date: Wed, 25 May 2005 11:45:22 -0700
Hello all,
I agree totally with everything that's been said here about making it
OO first, then optimizing it if necessary. It is rare that you have to
optimize, so don't try it before you know you're getting value for the
time spent. In this specific case, don't use the SQL unless you know
you're going to need it.
Here's the value-added part of the post: an article on Java vs C++,
speed-wise:
http://www.idiom.com/~zilla/Computer/javaCbenchmark.html
Cheers,
sacha
On May 25, 2005, at 11:30 am, James Cicenia wrote:
Ah yes.. I remember those concerns well.. I was one who had the
"serious" concerns. Turns out it was totally unfounded. My application
performs extremely well. And, yes I do aggregation here and there for
some the charting in my application. Let me just say, my application
is fast!!
By the way, I also work in PHP, etc., and those apps are noticeably
slower. I actually have come to love and appreciate WebObjects.
Actually to the detriment of my career... try finding a WebObjects
gig?!! No, one must use J2EE, WebSphere, WebLogic, JBoss, Oracle,
.Net, PHP, Hibernate, Struts, yada, yada, yada. However, for our
startup, WebObjects has been our secret weapon in that we are able to
maintain our application very easily.
It many not be Lisp, or Ruby on Rails (both of which I have no
experience in), but it is very, very fast.
- James Cicenia
On May 25, 2005, at 11:25 AM, Chuck Hill wrote:
I'll follow up on Jerry's reply with a focus on Jon's comment, "I
guess my only question is which way has the best performance. " This
is a common concern for new comers to WO and IMHO a common mistake.
Heed Jerry's advice: get your objects well designed and working and
only then and only if you see a real problem, start to optimize. I
recall someone else who wandered in here with the same concerns.
Again and again I said "don't worry about optimization". Finally, he
relented, but there was a lot of fretting. :-) After he finally
deployed, he came back with the comment "It's so fast that my user's
won't believe that it is a real, deployed web app and not a local
demo."
Chuck
On May 25, 2005, at 6:27 AM, Jerry W. Walker wrote:
Though I don't disagree with specific point made in this thread, I
hate the direction that it has taken.
If this is your first WO project, then there are a few reasons to do
this without using raw SQL. Probably the first, and foremost, is to
get used to doing things with objects rather than with tables. My
first concern is the statement of the original question:
"is there a way to build a FetchSpecification that would
accomplish the sql equivalent of "SELECT SUM(COLUMN_NAME) FROM
TABLE_NAME"
This question is clearly framed from the perspective of "I have a
table of rows with which I want to do something, now how do I get WO
to help me do that thing to my table in the same way I've always
done these things with SQL?"
Experienced WO developers would think instead of the object graph
that we are manipulating in our object oriented java application
rather than the rows we have stored in our relational database.
Rephrasing the question, "I have a set of objects 'O' with an
attribute 'a'. How do I obtain the sum of that attribute across
those objects?"
The obvious first answer is Sacha's first answer:
"My preferred method is to use the NSArray @sum key value coding
(note: no need to do an enumeration). "
Perhaps those objects have already been cached and we don't need to
fetch raw rows. Perhaps the sum could be obtained as a side effect
of another necessary operation on those objects later when they have
already been fetched.
Failing either of those two possibilities, I would still first write
the fetch without referencing raw rows and get it to work. Finally,
if the result is clearly taking too long, I would profile where the
delays are occurring and, if in database fetches, then would start
to consider raw rows. The point being that referencing raw rows is a
last resort rather than a way to move into the comfort zone of old
habits with result sets.
So what are the down sides to just moving immediately to raw rows?
* a missed opportunitiy to get used to the WO way
* the short circuiting of several elegant features built into WO
to help one deal with objects rather than rows
* the higher probability of weak object oriented design built up
from this raw row decision
I'm sure others could add more with a little more thought, but I
have to catch a train.
Good luck with WebObjects and welcome to the fold.
Best regards,
Jerry
On May 25, 2005, at 3:37 AM, Sacha Mallais wrote:
On May 25, 2005, at 12:15 am, Jonathan Miller wrote:
Hmm... I guess my only question is which way has the best
performance. To answer my own question I would assume it to by
passing raw SQL. This is my first web site with WO and I was
hoping I could avoid doing that however(it's just too cool not to
have to use SQL).
My preferred method is to use the NSArray @sum key value coding
(note: no need to do an enumeration). However, if you have many
many values to aggregate, then you're best bet is indeed raw SQL.
sacha
On May 24, 2005, at 5:19 PM, Sacha Mallais wrote:
On May 24, 2005, at 8:00 pm, Jonathan Miller wrote:
is there a way to build a FetchSpecification that would
accomplish the sql equivalent of "SELECT SUM(COLUMN_NAME) FROM
TABLE_NAME"
I know you can select the objects and then add them using a java
enumeration but I was wondering if there is another way.
The most obvious is to construct the SQL yourself and send it
directly using the low-level EOF stuff (or even the JDBC
stuff...). I mention it because, as WO developers, we sometimes
forget that there's SQL back there ;-)
A more interesting (if not hackish...) way to accomplish this
would be to create a new entity with the same table name and a
single derived attribute of "sum(column_name)". You can then
either generate a full Java class for that or just use raw rows.
Also, the PracticalWO frameworks (and the GVC frameworks -- also
to be released soon, and, come to think about it, probably the
ProjectWOnder frameworks too...) have a helper method that makes
aggregate queries more simple.
HTH,
sacha
-- Sacha Michel Mallais - 400 lb. chimp
Global Village Consulting Inc.: http://www.global-village.net/
1. Never tell everything at once.
-- Ken Venturi, Ken Venturi's Two Great Rules of Life
-- Sacha Michel Mallais
President / Developer Extraodinaire
Global Village Consulting Inc. http://www.global-village.net/
The bird of paradise alights only upon the hand that does not grasp.
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