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The Tao of Oracle

Mihajlo Tekic - Fri, 2006-03-24 11:11




VI.
The Oracle Masters have no mind of their own.
They are aware of the needs of others.
They are good to users who are good.
They are also good to users who are not good.
Because Virtue is goodness.
They have faith in servers that are faithful.
They also have faith in servers that are not faithful.
Because Virtue is faithfulness.
The Master is shy and humble - to the world he seems confusing.
Others look to him and listen.
He behaves like a little child.




more about The Tao of Oracle by Roby Sherman

Usings Sets with UIData

Adam Winer - Wed, 2006-03-22 18:24
One of the more personally surprising usability complaints I've heard was that the JSF UIData component does not support Sets. I hadn't anticipated that one. The underlying reason is that UIData is built around indexed data. For example, you can ask it to show rows 10,000 through 10,099. Such an operation would be nightmarishly expensive in a Set:



Iterator iter = collection.iterator();
for (int i = 0; i < 10000; i++) { iter.next(); }
// Hey, now we can start reading our data!



But, hey, we still got it wrong: we should have supported it. Yeah, it'd be slow - O(N) where N is the size of the set, not the amount of data actually displayed at one time - but the ease of use argument is compelling.

That said, there's nothing stopping you from using Sets with UIData right now... if you use the following class:


import java.util.AbstractMap;
import java.util.AbstractList;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.RandomAccess;
import java.util.Set;

public class ListFromCollection
{
public ListFromCollection()
{
_map = new MakeList();
_size = _DEFAULT_SIZE;
}

public Map<Collection, List> getList()
{
return _map;
}

public int getSize()
{
return _size;
}

public void setSize(int size)
{
_size = size;
}

private class MakeList extends AbstractMap<Collection, List>
{
public List get(Object o)
{
if (!(o instanceof Collection))
return null;

// Just send RandomAccess lists out; wrap any other Collection
// into a List
if ((o instanceof List) &&
(o instanceof RandomAccess))
return (List) o;

Collection c = (Collection) o;
if (c.isEmpty())
return Collections.EMPTY_LIST;

return new ListImpl(c, getSize());
}

public Set<Map.Entry<Collection, List>> entrySet()
{
// Not worth implementing at the moment; this Map is only
// accessed from
return Collections.emptySet();
}
}

static private class ListImpl extends AbstractList
{
public ListImpl(Collection c, int size)
{
_c = c;
_cSize = c.size();
if (size == 0)
_bufferSize = _cSize;
else
_bufferSize = Math.min(size, _cSize);

_buffer = new ArrayList(_bufferSize);
_offset = -1;
}

public int size()
{
return _cSize;
}

public Object get(int index)
{
if ((index < 0) || (index >= _cSize))
throw new IndexOutOfBoundsException();

int offset = (index / _bufferSize) * _bufferSize;
if (offset != _offset)
{
_loadBuffer(offset);
_offset = offset;
}

return _buffer.get(index - _offset);
}

private void _loadBuffer(int offset)
{
Iterator iter = _c.iterator();
int i = 0;

while (i < offset)
{
assert iter.hasNext();
iter.next();
i++;
}

_buffer.clear();

int count = 0;
while ((count < _bufferSize) && (i < _cSize))
{
assert iter.hasNext();
_buffer.add(iter.next());
i++;
count++;
}
}

private final Collection _c;
private final int _bufferSize;
private final int _cSize;
private int _offset;
private ArrayList _buffer;
}

private Map<Collection, List> _map;
private int _size;

static private int _DEFAULT_SIZE = 50;
}


So, what's this all mean? Well, say you want to write:


<h:dataTable value="#{mySet}">


... but that doesn't work. Just add one managed-bean entry to your faces-config.xml:


<managed-bean>
<managed-bean-name>makeList</managed-bean-name>
<managed-bean-class>
yourPackageHere.ListFromCollection
</managed-bean-class>
<managed-bean-scope>
request
</managed-bean-scope>
</managed-bean>


... and now, you can use sets on dataTable via:


<h:dataTable value="#{makeList.list[mySet]}">

ANT and PL/SQL

Scott Schwab - Tue, 2006-03-21 10:10
I have some task to add to ant, to run my PL/SQL test, luckily I found this link about it.Scott Schwabhttp://www.blogger.com/profile/14014003619353346507noreply@blogger.com0

Google Home Page for Me

Scott Schwab - Tue, 2006-03-21 09:38
Last night, I received my invite to build a Google Home Page. It was perfect timing as I am writing a presentation on Qute and the need for unit testing, and wanted to post it some place. A warning about power point + visio, if you are using photo clip art, watch the sizes. My initial version of the presentation was 50+ meg, fixing the photos size and resolution its is down 8 meg. Still large, Scott Schwabhttp://www.blogger.com/profile/14014003619353346507noreply@blogger.com0

instrumentation and Schrodinger's cat

Scott Schwab - Fri, 2006-03-17 09:15
I am working on a presentation about need for instrumentation in production code. This morning after talking to my daughter, I realized an analogy for the need to instrument code; it is the Schrodinger’s cat paradox. When you run you applications, as it if off chewing up the CPU, you cannot say, with certainty, that it is working correctly or it is failing, so in fact it is doing both. In Scott Schwabhttp://www.blogger.com/profile/14014003619353346507noreply@blogger.com0

Fixing JSF state saving: Save vs. Restore

Adam Winer - Fri, 2006-03-17 00:17
(A bit of esoterica, but probably of interest here to those deeply focused on JSF performance...)

An update: I got a chance to take some timings. As expected, saving state is now much faster: 85-90% faster, roughly equivalent to the improvements in the size of the saved state. But I was very surprised to discover that restoring the view isn't any faster, perhaps even marginally slower - until I realized that was the only possible result.

Restore View has to create a full tree, starting from zero. What could possibly be faster than creating that tree from an object tree that specifies every attribute that needs to be set, every class name that needs to be instantiated? Put another way, the old restoreVIew() approach, for all of its memory inefficiencies, is essentially an equivalent workload to building the tree in the first place, and might be even faster. This new approach starts with the overhead of building the tree from scratch, plus the overhead of setting some additional state. (That additional overhead is fairly negligible, but the point remains: fixing JSF state saving doesn't make Restore View fast.)

A slight clarification, BTW: I'm not using client-side state saving a la the RI or MyFaces, which serializes the entire tree to the client. Instead, we use ADF Faces's tokenized client-side state saving - run saveSerializedView, but then stash the result on the session, and only send a token to the client. If we were using fully serialized trees, then you would get a performance boost even in Restore View, because you'd only have to unserialize a small block, instead of the whole thing.

So, does that mean that restoreView() is necessarily slow? Well, no. There are approaches to optimizing restoreView(). The most direct is optimizing building the component tree - which will help both with initial component tree creation and with restoreView(). How to do that in another post. (Hint: FacesBean and Facelets are a huge help here, too!)

64 bit Oracle Speed?

Scott Schwab - Thu, 2006-03-16 09:01
Sitting at my cube, I overhead a discussion about 64-bit Oracle, mainly about the speed increase it would bring to an application. At Hotsos last week, I was sitting in a session and I remember someone saying, (very roughtly) that "64 bit Oracle is not about speed, it is about size, and that you have to remember that all those addresses are now twice as big".The problem is, I don't remember if Scott Schwabhttp://www.blogger.com/profile/14014003619353346507noreply@blogger.com1

Fixing JSF state saving: a progress report

Adam Winer - Wed, 2006-03-15 19:08
I've implemented the first version of an improved JSF state saving architecture, essentially what I talked about in my last post.

The very latest and greatest Facelets source code has a facelets.BUILD_BEFORE_RESTORE initialization parameter. When turned on, it changes ViewHandler.restoreView() to build the view before asking the StateManager for help.

And the latest ADF Faces code adds a new markInitialState() method to our components - which calls through to FacesBean.markInitialState(). When our MyFaces svn repository is set up, you'll be able to see this code too...

And the results? Well, one test case with a fairly large page dropped from nearly 10K of client-side state to only 600 bytes. That's more than a 90% reduction in saved state! (Presumably, CPU usage is way down, but I haven't measured that yet.)

There's still potential improvements: I could get that 600 bytes down further by overriding the state saving in UIViewRoot. Also, Jacob's suggestion to use a flat Map instead of a hierarchy would also help - currently, if one component deep in the hierarchy needs to store state, we build up a large hierarchy of mostly null Object arrays. This isn't especially expensive, but it is avoidable.

A footnote: Mike Youngstrom cogently noted in a comment to my last post that a delta approach to state saving would let us make UIData both simpler and more generic - instead of handcoding a specific set of properties to save on certain types of child components, just run state saving. Absolutely, Mike! I haven't prototyped this on our UIXTable component (which doesn't extend UIData, FWIW), but that's a great thing to try.

Raptor 1.0 takes flight

Scott Schwab - Wed, 2006-03-15 08:31
Oracle SQLDeveloper (Raptor) had its 1.0 production release on Monday, March 13. Congrats to the developers at Oracle building this very help and free tool.Scott Schwabhttp://www.blogger.com/profile/14014003619353346507noreply@blogger.com0

Hotsos Symposium 06, day two

Scott Schwab - Wed, 2006-03-08 00:02
Well, it is then end of Hotsos Symposium 06, day two, and I am having a great time.I have learned many things, from the good and bad of parallel processing in Oracle, from a very funny Doug Burns, to how to tell Oracle CBO's how long your PL/SQL function will take.One of the big themes this year, and probably every year, is instrumentation. Make use of DBMS_APPLICATION_INFO and such, so you can Scott Schwabhttp://www.blogger.com/profile/14014003619353346507noreply@blogger.com0

Is Oracle really quicker on Windows than Solaris?

Neil Jarvis - Tue, 2006-03-07 06:05
I installed a 10gR2 on Solaris 5.10 as a development database. The developers here have their own databases on their own P.C. One of the developers queried the speed of the solaris.

As a test I exported his schema and put it in many environments (Solaris and windows 9i and 10g)

To my amazement the windows installations always outperformed the Solaris ones both on initial loading the pool cache and subsequent runs

The test package is rather large (5000+ lines), which is used in a form to display customer details. On solaris I was typically getting an initial return time of 5 seconds and on windows, typically, 1 second.

Even subsequent runs (i.e. cached) the windows outperformed solaris.

The parameter sizes for the SGA were approx. the same and the file systems are the conventional method.

In both cases the disk configuration is local.

So the only difference being the processor speeds and Kernal coding!!!!!

Hotsos Symposium 06

Scott Schwab - Fri, 2006-03-03 16:04
I will be in Dallas next week, attending the Hotsos Symposium and a training session on the Cost Base Optimizer. This is my first time to this conference, but it sounds like it will be fun. Others have blogged what session they are attending, but I am not sure yet. I do know I want to hear the talk on CBO's Costing Of PL/SQL Functions and End-to-End Performance Diagnosis in Oracle.Cool cool Scott Schwabhttp://www.blogger.com/profile/14014003619353346507noreply@blogger.com0

QUTE and Oracle XE

Scott Schwab - Fri, 2006-03-03 09:02
Last night I loaded Qute 1.0.4 onto a fresh version of Oracle XE. I did get it to work, but needed to do the following:Install utl_file into Oracle XE. This can be done by running the RDBMS\ADMIN\utlfile.sql as the sys user.After using the Qute installer, one important package body would not compile QU_DESCRIBE. I ended up going into the package body and stubbing out the procedures which are Scott Schwabhttp://www.blogger.com/profile/14014003619353346507noreply@blogger.com0

How we're going to fix JSF state saving

Adam Winer - Thu, 2006-03-02 11:16
State is not bad. Statelesness is not good. State is your friend. But like a bad friend, State can sometimes hang around the house, eating your Mitchell's ice cream and drinking your Amarula 'til he gets fat and lazy, turns your house into a pig sty, and makes you wonder why you ever were friends with him in the first place.

JSF state is kind of like that. As I've said in a previous post, JSF state saving is way too hefty and saves far too much that doesn't need to be saved in the first place. So, here's my 5 step plan for fixing that.

Step 1
1. Use Facelets.

Step 2
2. Enhance the ADF Faces FacesBean API to support a "delta" mode - call a new markInitialState() method on it, and its saveState() implementation only saves all the changes made since markInitialState(). And if there's no changes, just return null. (You can't easily do this without FacesBean; see my earlier post on the subject.)

Step 3
3. Update the ADF Faces Facelets TagHandlers to call markInitialState() after creating the components.

Step 4
4. Implement Jacob Hookom's idea to save the tree of component state in a Map, not a gigantic Object array hierarchy.

Step 5
5. Rewrite the Facelets restoreView() implementation to recreate the tree from scratch in its original state, then call restoreState() on each component from the Map we built up in step 4.

And done. You don't need to save the tree structure anymore - Facelets is handling that by recreating the tree from its cached TagHandlers. And since most components don't actually change - unless you explicitly set properties on them - most components don't have to save any state.

(P.S.: there's some trickiness here that I'm ignoring: if you add components dynamically to the hierarchy, you do have to save their state and structure, since it's not present in the page. That's one reason why I strongly recommend making all dynamically created components transient if you have any choice in the matter, but that's a subject for another post.)

RAC on VMware

Wijaya Kusumo - Tue, 2006-02-28 20:15
There is an interesting article by Tarry Singh about Installing Oracle 10gR2 RAC on VMware. With VMware Server are being offered for free, I believe there will be more and more instances of Oracle running on VMware. But do we really want to have RAC on VMware? Perhaps I will use it for demo and learning purposes, but not in production system. To me, nothing beats the real stuff. VMware

Free Free Free

Scott Schwab - Tue, 2006-02-28 19:08
As reported everywhere, Oracle XE is now out and available. Add this to SQLDeveloper, Qute and you can do some rock solid PL/SQL programming for free.Scott Schwabhttp://www.blogger.com/profile/14014003619353346507noreply@blogger.com0

SQLDeveloper Export package file parsing

Scott Schwab - Sun, 2006-02-26 21:22
In my last post, I talked about the latest SQLDeveloper from Oracle, including a way to export all my packages in a single step, with their Tools->Export option. I had a Python script that did part of the job of breaking the outputted file into seperate files for package body and spec. Tonight, I reworked part of Python script, and then though I share it. Be warned, very little testing hasScott Schwabhttp://www.blogger.com/profile/14014003619353346507noreply@blogger.com3

SQLDeveloper EA 5

Scott Schwab - Sun, 2006-02-26 11:04
On OTN, Oracle has just released the fifth early adaptor version of SQL Developer (1.0.0.13.43). Going by the release notes, it fixed some bugs in the SQL Worksheet, UNICODE, and startup time.So far my favorite new feature, is the Tools->Export tool, which allows you to create a file of DDL and PL/SQL packages. This is great, as I end up writing lots of PL/SQL and leaving it in the databaseScott Schwabhttp://www.blogger.com/profile/14014003619353346507noreply@blogger.com0

Potential pitfall with Oracle Sequence

Wijaya Kusumo - Fri, 2006-02-24 00:44
Robert Vollman talks about Oracle sequences in his blog. Basically there are 3 potential issues with Oracle sequences that we need to consider when doing db design: 1. The squence number may "jump", that is 1,2,3,5,6,8,... with number 4 and 7 missing. One reason is if you do a transaction with NEXTVAL and then rollback, the sequence doesn't roll back to where you started. 2. By default,

A Simple Dual

Scott Schwab - Thu, 2006-02-23 20:14
What happens when this sql is called, but the tag you are looking for, is not in the XMLTYPE? SELECT extractvalue(my_xmltype, my_xpath_to, my_namespace) FROM dual; (1) Raise no data found exception (2) Returns null Answer: (2) returns null, so if you want to check to see if the text node exist for a x_path, don't expect a EXCEPTION clause to check it.Scott Schwabhttp://www.blogger.com/profile/14014003619353346507noreply@blogger.com0

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