Where to put a function to perform only once?

Question #1: I am writing an applet, and as part of it I have created a custom canvas class which extends the canvas class... When this is created I would like to perform a custom calculation of the size that it should be. Where is the best place to put this function? Right now I have put it in getPreferredSize(), but I'm afraid it might be called everytime i scroll or resize or whatever?
Question #2: When I load my IE browser and go to the page with my applet, then call the applet.getSize() function it works. When I hit the refresh button on IE, getSize returns 0. Is there a workaround to this? I have the getSize() in the init of the applet...
Thank you!
Rusty

Hi
About #1 question, the best place is at constructor class, "once a time" right? but getPreferredSize really is called so many time as needed, you know the reason. The simple workaround for #2 question is to store applet dimension at the very first call, also at applet construction.
Regards.

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Where to put custom function at?

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Also, I think you have misunderstood the purpose of
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Where to put the commit in the FORALL BULK COLLECT LOOP

Hi,
Have the following LOOP code using FORALL and bulk collect, but didnt know where to put the
'commit' :
open f_viewed;
LOOP
fetch f_viewed bulk collect into f_viewed_rec LIMIT 2000;
forall i in 1..f_viewed_rec.count
insert into jwoodman.jw_job_history_112300
values f_viewed_rec(i);
--commit; [Can I put this 'commit' here? - Jenny]
EXIT when f_viewed%NOTFOUND;
END LOOP;
commit;
Thanks,
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mc**** wrote:
Bulk collect normally used with large data sets. If you have less dataset such as 1000-2000 records then you canot get such a performance improvent using bulk collect.(Please see oracle documents for this)
When you update records Oracle acquire exclusive lock for that. So if you use commit inside the loop then it will process number of records defined by limit parameter at ones and then commit those changes.
That will release all locks acquired by Oracle and also teh memory used to keep those uncommited transactions.
If you use commit outside the loop,
Just assume that you insert 100,000 records, all those records will store in oracle memory and it will affect all other users performance as well.
Further more if you update 100,000 records then it will hold exclusive lock for all 100,000 records addtion to the usage of the oracle memory.
I am using this for telco application which we process over 30 million complex records (one row has 234 columns).
When we work with large data sets we do not depends with the oracle basic rollback function. because when you keep records without commit itb uses oracle memory and badly slowdown all other processes.Hi mc****,
What a load of dangerous and inaccurate rubbish to be telling a new Oracle developer. Commit processing should be driven by the logical unit of a transaction. This should hold true whether that transaction involves a few rows or millions. If, and only if, the transaction is so large that it affects the size constraints of the database resources, in particular, rollback or redo space, then you can consider breaking that transaction up to smaller transactions.
Why is frequent committing undesirable I hear you ask?
First of all it is hugely wasteful of rollback or redo space. This is because while the database is capable of locking at a row level, redo is written at a block level, which means that if you update, delete or insert a million rows and commit after each individual statement, then that is a million blocks that need to go into redo. As many of these rows will be in the same block, if you instead do these as one transaction, then the same block in redo can be transacted upon, making the operation more efficient. True, locks will be held for longer, but if this is new data being done in batches then users will rarely be inconvenienced. If locking is a problem then I would suggest that you should be looking at how you are doing your processing.
Secondly, committing brings into play one of the major serialization points in the database, log sync. When a transaction is committed, the log buffer needs to be written to disc. This occurs serially for multiple commits. Each commit has to wait until the commit before has completed. This becomes even more of a bottleneck if you are using Data Guard in SYNC mode, as the commit cycle does not complete until the remote log is notified as written.
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1. Commit as infrequently as possible, usually at the logical unit of a transaction
2. When building transactions, first of all seek to do it using straight SQL (CTAS, insert select, update where etc). If this can't be easily achieved, then use PL/SQL bulk operations.
Regards
Andre

Architecture question...where to put the code

Newbie here, so please be gentle and explicit (no detail is
too much to give or insulting to me).
I'm hoping one of you architecture/design gurus can help me
with this. I am trying to use good principals of design and not
have code scattered all over the place and also use OO as much as
possible. Therefore I would appreciate very much some advice on
best practices/good design for the following situation.
On my main timeline I have a frame where I instantiate all my
objects. These objects refer to movieClips and textFields etc. that
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and backward in (lets call it NavClip) . For example on frame 1 I
might have a button, on frame 2 and 3 nothing, on frame 4 maybe a
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itself, and then address the asset that way (i.e.
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checking when you use the NavClip["interactive_mc"] form.
I hope I'm not being too dim a bulb on this and have missed
something really obvious. Thanks in advance to anyone who can help
me use a best practice.

1. First of all, the code should be:
var myDraggable:Draggable=new Draggable(myClip_mc);
myDraggable.initDrag();
Where initDrag() is defined in the Draggable class. When you
start coding functions on the timeline... that's asking for
problems.
>>Do I wind up with another object each time this
function is called
Well, no, but. That would totally depend on the code in the
(Draggable) class. Let's say you would have a private static var
counter (private static, so a class property instead of an instance
property) and you would increment that counter using a
setInterval(). The second time you enter the frame and create a new
Draggable object... the counter starts at the last value of the
'old' object. So, you don't get another object with your function
literal but you still end up with a faulty program. And the same
goes for listener objects that are not removed, tweens that are
running and so on.
The destroy() method in a custom class (=object, I can't
stress that enough...) needs to do the cleanup, removing anything
you don't need anymore.
2. if myDraggable != undefined
You shouldn't be using that, period. If you don't need the
asset anymore, delete it using the destroy() method. Again, if you
want to make sure only one instance of a custom object is alive,
use the Singleton design pattern. To elaborate on inheritance:
define the Draggable class (class Draggable extends MovieClip) and
connect it to the myClip_mc using the linkage identifier in the
library). In the Draggable class you can define a function unOnLoad
(an event fired when myClip_mc is removed using
myClip_mc.removeMovieClip()...) and do the cleanup there.
3. A destroy() method performs a cleanup of any assets we
don't need anymore to make sure we don't end up with all kinds of
stuff hanging around in the memory. When you extend the MovieClip
Class you can (additionally) use the onUnLoad event. And with the
code you posted, no it wouldn't delete the myClip_mc unless you
program it to do so.

Where to put GUI_PROGRESS_INDICATOR and error in CLOI_PUT_SIGN_IN_FRONT.

Hello experts,
I am currently debuggin my report and it is giving me a dump when I am trying to use FM
CLOI_PUT_SIGN_IN_FRONT. It says that it only accepts character based values. Also,
based on my code below, where can I put the function GUI_PROGRESS_INDICATOR so users can know
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ENDLOOP.
Again, thanks alot guys and take care!

1) CLOI_PUT_SIGN_IN_FRONT will take any values, Character and numeric. It basically make the sign as pre-fix. Eg 53.6- to -53.6. Better way you could assign it to a Packed decimal and pass it to FM and then reassign it to the field.
2)GUI_PROGRESS_INDICATOR can be used before the process stats.. For example: you can use it before the select statment with the text 'Database selection...'
rgds,
TM
Message was edited by: Thomas Mann
Message was edited by: Thomas Mann

Where to put javascript code?

Hello,
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***If my post is answer for your query please mark as answer***
***If my answer is helpful please vote***

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Regards,
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Oracle 9i function to perform data manipulation

Hi everyone,
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If it does not have a parent record (null or blank) then I take this value, join with another table, perform some processing and return one varchar2 value.
If it has a parent record (not null or not blank) then I need to retrieve all the other children records associated with this same parent record, take this value, join with another table,perform some processing and return one varchar2 value.
I have two simple queries that I wrote: one for record with null/blank parent, and the other for record with same parent and other children. These two queries work individually, when I combine them is where I run into problems. Sample table:
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child parent
1234
5107 3167
6259 3652
5678 9754
3167 3167
3652 3652
1649
2306 9754
4657 3652
9754 9754
8753 3652
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FROM OTHERTABLE C,
(SELECT TableA.child, TableA.parent
FROM XYZ TableA
WHERE TableA.child ='1234')A
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passing record 4657 into the function
SELECT c.CHILDfield, c.PARENTfield, TableOther.field1
FROM OTHERTABLE TableOther,(
(SELECT B.CHILDfield, B.PARENTfield FROM
(SELECT A.PARENTfield, i.CHILDfield FROM TableB,
(SELECT TableA.CHILDfield, TableA.PARENTfield
FROM XYZ TableA
WHERE TableA.CHILDfield ('4657' ))A
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WHERE A.PARENTfield = TableB.PARENTfield)B
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-- note: parent can exist in the parent and child fields
WHERE B.CHILDfield <> B.PARENTfield))C
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The dilemma is writing a generic query to accommodate both these situations. My current function can handle each of these situations individually, but not both. For testing purposes, I change the select statement depending on whether I have a record that has a parent on not!
Any help is greatly appreciated.

You want one function to handle two cases? This is the best opportunity to use the IF STATEMENT.
FUNCTION MyFunc (p_input IN VARCHAR2) RETURN VARCHAR2 IS
ReturnValue VARCHAR2;
BEGIN
IF <blank or null test> THEN
SELECT ... -- Blank or null select statement
... -- Blank or null data processing
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Hello,
I'm having little troubles while writing a query for which is needed a where condition on a function.
Here a little example:
select id_vehicle from vehicle_list where id_user = 1 and function(id_vehicle) = 1;
that function is using locator (quite heavy).
as I would like to execute the function just for the id_user = 1 and not for the whole table (like it seemed it does in the privous query) I tried this second:
select id_vehicle from (select id_vehicle from vehicle_list where id_user = 1) where function(id_vehicle) = 1;
Nothing changed, neither the execution explain.
Finally I found this syntax, that works as I would:
select id_vehicle from vehicle_list where id_user = 1 group by id_vehicle having function(id_vehicle) = 1;
Is this the only solution to achieve my goal?
Thanks in advance,
Samuel Rabini

Karthick_Arp wrote:
Samuel Rabini wrote:
Hello,
I'm having little troubles while writing a query for which is needed a where condition on a function.
Here a little example:
select id_vehicle from vehicle_list where id_user = 1 and function(id_vehicle) = 1;
that function is using locator (quite heavy). Locator? I don't get you what is that? Probably some geo/spatial stuff.
>
as I would like to execute the function just for the id_user = 1 and not for the whole table (like it seemed it does in the privous query) I tried this second:
select id_vehicle from (select id_vehicle from vehicle_list where id_user = 1) where function(id_vehicle) = 1; For oracle both the query are the same. Search the document for predicate pushing and read it.
You are in a wrong assumption that the function is applied for all the row in the table. Its only applied on the rows for which id_user is 1. How to check it? just pas id_user as and parameter to the function and print it in the function. You will get to know that. not always. it depends on many factors. The CBO might decide that the condition with the function will return less values then the id_use=1 condition. Therefore it might choose to execute the function first. An execution plan including join predicates would also show this.
There are some ways to influence the optimizers behaviour regarding function. One is to make it deterministic (if possible). Also one could give addition info to the optimizer about the function. Dynamic sampling could also be helpful, altough I'm not so sure in this case.
I myself would prefer to write the query in such a way that the optimizer is forced to execute it as late as possible.
There are different ways how to do this.
Using a subquery and a sort operation (order by, group by ) is one. That's why it was working for the op. Problem is this additional sort operation has its own performance cost.
Using COALESCE can be another way. It might be difficult rewrite the query in this case. But coalesce is one of the few commands (or the only one?) where the second parameter is not executed if the first one is fulfilling the condition.
Last but not least you can use hints to prevent the subquery rewriting.

Where to put java code - Best Practice

Hello. I am working with the Jdeveloper 11.2.2. I am trying to figure out the best practice for where to put code. After reviewing http://docs.oracle.com/cd/E26098_01/web.1112/e16182.pdf it seemed like the application module was the preferred spot (although many of the examples in the pdf are in main methods). After coding a while though, I noticed that there were quite a few libraries imported, and wondered whether this would impact performance.
I reviewed postings on the forum, especially Re: Access service method (client interface) programmatically . This link mentions accessing code from a backing bean -- and the gist of the recommendations seems to be to use the data control to drag it to the JSF, or use the bindings to access code.
My interest lies in where to put java code in the first place; In the View Object, Entity Object, and Am object, backing bean.....other?
I can outline several best guesses about where to put code and the pros and cons:
1. In the application module
Pros: Centralized location for code makes development and support more simple as there are not multiple access points. Much like a data control centralizes services, the application module can act as a conduit for different pieces of code you have in objects in your model.
Cons: Everything in one place means the application module becomes bloated. I am not sure how memory works in java -- if the app module has tons of different libraries are they all called when even a simple query re-execute method is called? Memory hog?
2. Write code in the objects it affects. If you are writing code that accesses a view object, write it in a view object. Then make it visible to the client.
pros: The code is accessed via fewer conduits (for example, I would expect that if you call the application module from a JSF backing bean, then the application module calls the view object, you have three different pieces of code --
conts: The code gets spread out, harder to locate etc.
I would greatly appreciate your thoughts on the matter.
Regards,
Stuart
Edited by: Stuart Fleming on May 20, 2012 5:25 AM
Edited by: Stuart Fleming on May 20, 2012 5:27 AM

First point here is when you say "where to put the java code" and you're referring to ADF BC, the point is you put "business logic java code" in the ADF Business Components. It's fine of course to have Java code in the ViewController layer that deals with the UI layer. Just don't put business logic in the UI layer, and don't put UI logic in the model layer. In your 2 examples you seem to be considering the ADF BC layer only, so I'll assume you mean business logic java code only.
Meanwhile I'm not keen on the term best practice as people follow best practices without thinking, typically best practices come with conditions and people forget to apply them. Luckily you're not doing that here as you've thought through the pros and cons of each (nice work).
Anyway, back on topic and off my soap box, as for where to put your code, my thoughts:
1) If you only have 1 or 2 methods put it in the AppModuleImpl
2) If you have hundreds of methods, or there's a chance #1 above will morph into #2, split the code up between the AppModuleImpl, ViewImpl and ViewRowImpls. Why? Because your AM will become overloaded with hundreds of methods making it unreadable. Instead put the code where it should logically go. Methods that work on a specific VO row go into the associated ViewRowImpl, methods that work across rows in a VO go into the ViewImpl, and methods that work across VOs in the associated AppModuleImpl.
To be honest which you ever option you choose, one thing I do recommend as a best practice is be consistent and document the standard so your other programmers know.
Btw there isn't an issue about loading lots of libraries/imports into a class, it has no runtime cost. However if your methods require lots of class variables, then yes this will have a memory cost.
On a side note if you're interested in more ideas around how to build ADF apps correctly think about joining the "ADF EMG", a free online forum which discusses ADF architecture, best practices (cough), deployment architectures and more.
Regards,
CM.

Where to put a function to perform only once?

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