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• Some Original Expressions

  - by Phil Factor

  Guest Editorial for Simple-Talk newsletterIn a guest editorial for the Simple-Talk Newsletter, Phil Factor wonders if we are still likely to find some more novel and unexpected ways of using the newer features of Transact SQL: or maybe in some features that have always been there! There can be a great deal of fun to be had in trying out recent features of SQL Expressions to see if  they provide new functionality.  It is surprisingly rare to find things that couldn’t be done before, but in a different   and more cumbersome way; but it is great to experiment or to read of someone else making that discovery.  One such recent feature is the ‘table value constructor’, or ‘VALUES constructor’, that managed to get into SQL Server 2008 from Standard SQL.  This allows you to create derived tables of up to 1000 rows neatly within select statements that consist of  lists of row values.  E.g. SELECT Old_Welsh, number FROM (VALUES ('Un',1),('Dou',2),('Tri',3),('Petuar',4),('Pimp',5),('Chwech',6),('Seith',7),('Wyth',8),('Nau',9),('Dec',10)) AS WelshWordsToTen (Old_Welsh, number) These values can be expressions that return single values, including, surprisingly, subqueries. You can use this device to create views, or in the USING clause of a MERGE statement. Joe Celko covered  this here and here.  It can become extraordinarily handy to use once one gets into the way of thinking in these terms, and I’ve rewritten a lot of routines to use the constructor, but the old way of using UNION can be used the same way, but is a little slower and more long-winded. The use of scalar SQL subqueries as an expression in a VALUES constructor, and then applied to a MERGE, has got me thinking. It looks very clever, but what use could one put it to? I haven’t seen anything yet that couldn’t be done almost as  simply in SQL Server 2000, but I’m hopeful that someone will come up with a way of solving a tricky problem, just in the same way that a freak of the XML syntax forever made the in-line  production of delimited lists from an expression easy, or that a weird XML pirouette could do an elegant  pivot-table rotation. It is in this sort of experimentation where the community of users can make a real contribution. The dissemination of techniques such as the Number, or Tally table, or the unconventional ways that the UPDATE statement can be used, has been rapid due to articles and blogs. However, there is plenty to be done to explore some of the less obvious features of Transact SQL. Even some of the features introduced into SQL Server 2000 are hardly well-known. Certain operations on data are still awkward to perform in Transact SQL, but we mustn’t, I think, be too ready to state that certain things can only be done in the application layer, or using a CLR routine. With the vast array of features in the product, and with the tools that surround it, I feel that there is generally a way of getting tricky things done. Or should we just stick to our lasts and push anything difficult out into procedural code? I’d love to know your views.

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• T-SQL Tuesday #025 &ndash; CHECK Constraint Tricks

  - by Most Valuable Yak (Rob Volk)

  Allen White (blog | twitter), marathoner, SQL Server MVP and presenter, and all-around awesome author is hosting this month's T-SQL Tuesday on sharing SQL Server Tips and Tricks.  And for those of you who have attended my Revenge: The SQL presentation, you know that I have 1 or 2 of them.  You'll also know that I don't recommend using anything I talk about in a production system, and will continue that advice here…although you might be sorely tempted.  Suffice it to say I'm not using these examples myself, but I think they're worth sharing anyway. Some of you have seen or read about SQL Server constraints and have applied them to your table designs…unless you're a vendor ;)…and may even use CHECK constraints to limit numeric values, or length of strings, allowable characters and such.  CHECK constraints can, however, do more than that, and can even provide enhanced security and other restrictions. One tip or trick that I didn't cover very well in the presentation is using constraints to do unusual things; specifically, limiting or preventing inserts into tables.  The idea was to use a CHECK constraint in a way that didn't depend on the actual data: -- create a table that cannot accept data CREATE TABLE dbo.JustTryIt(a BIT NOT NULL PRIMARY KEY, CONSTRAINT chk_no_insert CHECK (GETDATE()=GETDATE()+1)) INSERT dbo.JustTryIt VALUES(1)   I'll let you run that yourself, but I'm sure you'll see that this is a pretty stupid table to have, since the CHECK condition will always be false, and therefore will prevent any data from ever being inserted.  I can't remember why I used this example but it was for some vague and esoteric purpose that applies to about, maybe, zero people.  I come up with a lot of examples like that. However, if you realize that these CHECKs are not limited to column references, and if you explore the SQL Server function list, you could come up with a few that might be useful.  I'll let the names describe what they do instead of explaining them all: CREATE TABLE NoSA(a int not null, CONSTRAINT CHK_No_sa CHECK (SUSER_SNAME()<>'sa')) CREATE TABLE NoSysAdmin(a int not null, CONSTRAINT CHK_No_sysadmin CHECK (IS_SRVROLEMEMBER('sysadmin')=0)) CREATE TABLE NoAdHoc(a int not null, CONSTRAINT CHK_No_AdHoc CHECK (OBJECT_NAME(@@PROCID) IS NOT NULL)) CREATE TABLE NoAdHoc2(a int not null, CONSTRAINT CHK_No_AdHoc2 CHECK (@@NESTLEVEL>0)) CREATE TABLE NoCursors(a int not null, CONSTRAINT CHK_No_Cursors CHECK (@@CURSOR_ROWS=0)) CREATE TABLE ANSI_PADDING_ON(a int not null, CONSTRAINT CHK_ANSI_PADDING_ON CHECK (@@OPTIONS & 16=16)) CREATE TABLE TimeOfDay(a int not null, CONSTRAINT CHK_TimeOfDay CHECK (DATEPART(hour,GETDATE()) BETWEEN 0 AND 1)) GO -- log in as sa or a sysadmin server role member, and try this: INSERT NoSA VALUES(1) INSERT NoSysAdmin VALUES(1) -- note the difference when using sa vs. non-sa -- then try it again with a non-sysadmin login -- see if this works: INSERT NoAdHoc VALUES(1) INSERT NoAdHoc2 VALUES(1) GO -- then try this: CREATE PROCEDURE NotAdHoc @val1 int, @val2 int AS SET NOCOUNT ON; INSERT NoAdHoc VALUES(@val1) INSERT NoAdHoc2 VALUES(@val2) GO EXEC NotAdHoc 2,2 -- which values got inserted? SELECT * FROM NoAdHoc SELECT * FROM NoAdHoc2   -- and this one just makes me happy :) INSERT NoCursors VALUES(1) DECLARE curs CURSOR FOR SELECT 1 OPEN curs INSERT NoCursors VALUES(2) CLOSE curs DEALLOCATE curs INSERT NoCursors VALUES(3) SELECT * FROM NoCursors   I'll leave the ANSI_PADDING_ON and TimeOfDay tables for you to test on your own, I think you get the idea.  (Also take a look at the NoCursors example, notice anything interesting?)  The real eye-opener, for me anyway, is the ability to limit bad coding practices like cursors, ad-hoc SQL, and sa use/abuse by using declarative SQL objects.  I'm sure you can see how and why this would come up when discussing Revenge: The SQL.;) And the best part IMHO is that these work on pretty much any version of SQL Server, without needing Policy Based Management, DDL/login triggers, or similar tools to enforce best practices. All seriousness aside, I highly recommend that you spend some time letting your mind go wild with the possibilities and see how far you can take things.  There are no rules! (Hmmmm, what can I do with rules?) #TSQL2sDay

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• Abstracting entity caching in XNA

  - by Grofit

  I am in a situation where I am writing a framework in XNA and there will be quite a lot of static (ish) content which wont render that often. Now I am trying to take the same sort of approach I would use when doing non game development, where I don't even think about caching until I have finished my application and realise there is a performance problem and then implement a layer of caching over whatever needs it, but wrap it up so nothing is aware its happening. However in XNA the way we would usually cache would be drawing our objects to a texture and invalidating after a change occurs. So if you assume an interface like so: public interface IGameComponent { void Update(TimeSpan elapsedTime); void Render(GraphicsDevice graphicsDevice); } public class ContainerComponent : IGameComponent { public IList<IGameComponent> ChildComponents { get; private set; } // Assume constructor public void Update(TimeSpan elapsedTime) { // Update anything that needs it } public void Render(GraphicsDevice graphicsDevice) { foreach(var component in ChildComponents) { // draw every component } } } Then I was under the assumption that we just draw everything directly to the screen, then when performance becomes an issue we just add a new implementation of the above like so: public class CacheableContainerComponent : IGameComponent { private Texture2D cachedOutput; private bool hasChanged; public IList<IGameComponent> ChildComponents { get; private set; } // Assume constructor public void Update(TimeSpan elapsedTime) { // Update anything that needs it // set hasChanged to true if required } public void Render(GraphicsDevice graphicsDevice) { if(hasChanged) { CacheComponents(graphicsDevice); } // Draw cached output } private void CacheComponents(GraphicsDevice graphicsDevice) { // Clean up existing cache if needed var cachedOutput = new RenderTarget2D(...); graphicsDevice.SetRenderTarget(renderTarget); foreach(var component in ChildComponents) { // draw every component } graphicsDevice.SetRenderTarget(null); } } Now in this example you could inherit, but your Update may become a bit tricky then without changing your base class to alert you if you had changed, but it is up to each scenario to choose if its inheritance/implementation or composition. Also the above implementation will re-cache within the rendering cycle, which may cause performance stutters but its just an example of the scenario... Ignoring those facts as you can see that in this example you could use a cache-able component or a non cache-able one, the rest of the framework needs not know. The problem here is that if lets say this component is drawn mid way through the game rendering, other items will already be within the default drawing buffer, so me doing this would discard them, unless I set it to be persisted, which I hear is a big no no on the Xbox. So is there a way to have my cake and eat it here? One simple solution to this is make an ICacheable interface which exposes a cache method, but then to make any use of this interface you would need the rest of the framework to be cache aware, and check if it can cache, and to then do so. Which then means you are polluting and changing your main implementations to account for and deal with this cache... I am also employing Dependency Injection for alot of high level components so these new cache-able objects would be spat out from that, meaning no where in the actual game would they know they are caching... if that makes sense. Just incase anyone asked how I expected to keep it cache aware when I would need to new up a cachable entity.

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• User Produtivity Kit - Powerful Packages (Part 1)

  - by [email protected]

  User Productivity Kit provides the ability to create a variety of content types including robust topics on system process and web pages with formatted text and graphics. There are times when you want to enhance content with media types not naively created by User Productivity Kit, media types such as video, custom animations, forms, and more. One method of doing this is to maintain these media files on a web server - separate from the User Productivity Kit player content and link to the files using absolute URLs such as http://myserver/overview.html. While this will get you going, you won't benefit from the content management capabilities of the UPK Developer. Features such as check-in / check-out, history, document properties, folder permissions and more are not available to this external content. Further, if you ever need to move that content to a server with a different name or domain, you'd need to update all your links. UPK version 3.1 introduced a new document type - the package. A package is a group of folders and files that you manage in the Developer library as a single document. These package documents work in the same manner as any other document in the library and you can use all of the collaborative content development features you see with other document types. Packages can be used for anything from single Word documents, PDF files, and graphics to more intricate sets of inter-related files commonly seen with HTML files and their graphics, style sheets, and JavaScript files. The structure of the files and folders within a package will always be preserved so this means that any relative links between files in the package will work. For example, an HTML file containing an image tag with a relative link to a graphic elsewhere in the same package will continue to function properly both when viewed in the Developer and when published to outputs such as the UPK Player. Once you start to use packages, you'll soon discover that there is a lot of existing content that can be re-purposed by placing it into UPK packages. Packages are easily created by selecting File...New...Package. Files can be added in a number of ways including the "Add Files" button, copy & paste from Windows Explorer, and drag & drop. To use one of the files in the package, just create a link to the file in the package you want to target. This is supported throughout the Developer in places such as section & topic concepts, frame links and hyperlinks in web pages. A little more challenging is determining how to structure packages in your library. As I mentioned earlier, a package can contain anything from a single file to dozens of files and folders. So what should you do? You could create a package for each file. You could create one package for all your files. But which one is right? Well, there's not a right and wrong answer to this question. There are advantages and disadvantages to each. The right decision will be influenced by the package files themselves, the structure of the content in the library, the size and working style of the development team, how content is shared between different outlines and more. The first consideration can be assessed the quickest. If the content to be placed in the package is composed of multiple files and those files reference each other, they should be in the same package. There are loads of examples of this type of content. HTML files with graphics and style sheets, HTML files with embedded Flash movies, and Word documents saved as HTML are all examples where the content is composed of multiple files and the files reference each other in some way. Content like this should always be placed in a singe package such that these relative links between the files are preserved and play properly in the UPK Player. In upcoming posts, I'll explain additional considerations.

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• A story of Murphy&ndash;my technical issues at TechDays Switzerland #chtd

  - by Laurent Bugnion

  I had two sessions at the recent Swiss TechDays. While the first one (Advanced Development for Windows Phone 8) went extremely well (I think), I had a very annoying technical issue in the beginning of my second session. First let me add that I talked to Microsoft about that and I hope they will change a few things in the room assignment for next year. My two sessions were one right after the other, with only 15 minutes break to change room. I don’t mind having two sessions so close from each other, but I would really like them to be in the same room in order to avoid having to move my laptops (plural, that will become important later) and redoing the tech check. That being said, I am guilty of not checking where my talks would be before the day before the conference, and when I did notice, it was too late to change it. After my first session, I quickly moved to the other room and setup my main laptop, a Dell Precision. We tested the video output (VGA) and didn’t notice anything special. The projectors are using a fairly high resolution (kudos to the Basel conference center for not having old school 1024x768 projectors anymore, that makes Blend really hard to demo ;) but since everything went great during the first talk, I was not worried. In fact I even had some time to chat with some early attendees about my Microsoft Surface and the Samsung Slate 7, which I had carried with me in addition to the Precision. I just thought it would be nice to show the hardware that Windows 8 can run on, without thinking any further. When the session started, I immediately noticed that the main screen was not showing anything. I thought I had just forgotten to switch to “duplicate” for the video output, and did that with a quick Win-P. However it didn’t “hold”. After 2 seconds, it reverted back to a black display for my attendees. Then I started to really worry. We tried everything, switching from VGA to HDMI, changing the resolution, setting the projector as primary display, but nothing did the trick. The projector was just refusing to show my screen. Now, to show you how despaired I started to be, I even considered using the “extend” setting (which worked just fine), and to use one of the feedback monitors on the floor but really it was super cumbersome. Eventually, my last resort arrived: I started my Samsung Slate 7, which by chance has Visual Studio 12 and Blend 5 installed, plugged the HDMI projector in the dock (yes, I had the dock with me, which I usually don’t!), connected it to internet (had to enter a long password for that), loaded the source code from my main machine using a USB stick and…. finally started to give my presentation. All in all I think we lost about 10 minutes. Amongst the most horrible minutes of my whole life, truly (yes I am blessed, I didn’t have that many horrible minutes in my life ;) I really want to apologize to my attendees. We joked a bit during the attempts to resolve the issue, the reactions I had after the session were all very nice and sympathetic. Only a handful of people left my session while I was having the issues, and I really don’t blame them (who knew how long the problem would last!!). But still, I probably talked at more than 60 sessions over the years, and this was by far my most painful moment. What did I learn? So what did I learn from this? Well from now on I will always have my slate ready with the latest source code, internet connection and every tool I might need during the presentation. This way, if I detect even a hint that the Precision might not work, I will just switch to the Slate. The experience of presenting on the slate is actually not bad at all, it is just a bit slow for my taste, but it does work. By the way, I will be posting the code and slides for my sessions very soon, I just need to “clean it and zip it”. Stay tuned, and thanks again for your patience in that horrible circumstance. Cheers Laurent   Laurent Bugnion (GalaSoft) Subscribe | Twitter | Facebook | Flickr | LinkedIn

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• SQLAuthority News – Advantages of Distance Learning

  - by Pinal Dave

  Distance education is extremely popular – almost overnight, it seems.  Almost everyone has taken an online course, or knows someone who has, or is considering joining an online school.  There are many advantages and disadvantages to attending an online school – but the same can be said of attending a physical school!  Let’s take a look at the top reasons to use distance education. 1) Flexibility.  Physical universities are usually willing to make some concessions to student – like night classes, study hours, and online networks.  However, nothing is going to beat the flexibility of distance education.  You can attend classes and take notes anytime, anywhere, wearing anything you’d like! 2) Affordability.  We don’t need to get into hard numbers to understand how an expensive university can be.  Students are taking on more and more debt just to get an education.  Many of these fees pay for room, board, and facilities.   Distance education cuts out all these costs, and makes attending school much more affordable for the average student. 3) Try before you buy.  Did you know that the average college student changes his or her major 10 times before they graduate?  You can imagine that this kind of indecision plays a huge part in WHEN you graduate – not being able to make up your mind can cost you big bucks if you have to stay in school for extra years!  Distance education allows you to take different classes from a wide range of disciplines.  Do you want to study forensic science or English literature?  Now you don’t have to pay for classes you can’t afford just to find out. 4) Pace yourself.  Some students struggle in a traditional classroom setting – classes can be taught too fast, too slow, or there are too many distractions.  Distance education allows mature students to set the pace themselves.  They can rewatch lectures they didn’t catch the first time, or go through classes quickly if they are already familiar with the material – cutting out the chance of burning out or getting bored. 5) Lifelong learning.  Maybe you already have a degree, but would like to learn more about your field, or a related field, or maybe even about something completely unrelated – just because you are curious!  Distance education allows you to learn whatever you want ,whenever you want (and yes, wearing anything you’d like!). 6) Attend whatever college you want.  Because of the popularity of distance education, physical campuses are getting in on the game by offering online courses – often just uploaded versions of classes already taught at their campus.  Ever wanted to attend Harvard, but knew you couldn’t get in?  Take a class online!  Of course, you probably should not attempt to lie and say you have a Harvard degree, but Ivy League colleges are prestigious because they are the best in their field – take advantage of the best by taking an online course! I am a big believer in continuing education, whether it is online courses, returning to school, or even take informal classes online.  Distance education can be a great way to accomplish these goals and become a lifelong learner. My friends at provides training through virtual classrooms for students who want to avoid travelling. Distance learning course allows IT aspirants to connect with trainers using the internet.  I encourage everyone to check it out! Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, SQL Training, T SQL, Technology

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• October in Review

  - by Richard Bingham

  With OpenWorld over October was time to get back to serious work for everyone, including the Fusion Applications Developer Relations team. Don't forget the OpenWorld content is still available, including presentation downloads, for a limited period of time so be sure to grab anything you found useful or take another scan for anything you might have missed. Of all the announcements, the continued evolution of the Oracle Cloud services for extending and integrating with Fusion Applications is increasing in popularity, and certainly the Cloud Marketplace is something we're becoming involved in. More details to follow. Fusion Concepts Last week Vik from our team started the new "Fusion Concepts" series of articles, providing those new to Fusion Applications an explanation of the architectural basics, with the aim to reduce the learning curve and lay the platform for more efficient and effective development. The series begun with an insightful first post on the different schemas that exist in the Fusion Applications database. Look out for upcoming posts on multi-lingual entities, profile options, look-ups and more. New Learning Resources Our YouTube channel continued to expand with more 'how to' videos on using page composer, extending the Simplified UI (aka FUSE), and integrating BI reports and analytics. Also the Oracle Learning Library is now well established as a central resource for knowledge, now with thousands of tutorials, videos, and documents. Of particular note are the great new extensibility-related videos added by the CRM Product Management team, including more on the ever-expanding capabilities of Application Composer. To see some examples of these search using keyword 'customization' or the product 'Sales Cloud'. Finally on learning resources, as Oliver mentioned the Oracle Press book on Fusion Application Customization and Extensibility is now available for pre-order on Amazon (due out 1st Jan). Out And About October also saw us attend the annual Apps Conference held by the UK Oracle User Group in London. Interestingly there was an Applications Transformation stream of sessions and content that included Fusion Applications with all the latest in the Oracle Applications evolution, as always focused around the three tenets of social, mobile, and cloud. Read more in Richard's post-event write up. Other teams around Oracle have also been busy. Angelo from the Platform Technical Services group has done quite a bit of work using web services with Fusion SaaS and has published many interesting findings on his blog. It's definitely recommended reading if you are working on any related integration projects. The middleware-for-applications group has built a new tool called "AppAdvantage" offering an online assessment of your use of Fusion Middleware technologies with Oracle Applications. As the popularity of integrating cloud applications with on-premises systems continued to grow, leveraging existing middleware technologies (and licenses) to support the integration solution is likely to be of paramount importance. Similarly the "Build Enterprise Application Extensions with Ease" section of the related webpage has AppsUX director Killan Evers speaking about customization using the composer tools. Both are useful resources for those just getting started with a move to Fusion Applications. The Oracle A-Team, specialists in middleware technical architecture, always publish superb content via their 'chronicles' site, now with a substantial amount specifically related to Fusion Applications. Click on the Fusion Applications menu on the top right of their homepage to see more. Last month of particular note was an article on customizing the timeout pop-up message that shows to inactive users, providing design-time insight and easy-to-follow steps. Finally if you're looking at using Oracle Middleware and Cloud to tailor and extend your applications then you may also be interested in this new blog post on the roadmap for Oracle SOA and the latest on-demand Cloud Development webcast.

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• Moving from Silverlight 4 Beta to RC - Part 1

  The other day I had finished up my Task-It Webinar, written a few blog posts, and knew the time had come to move from my Silverlight 4 Beta environment up to the latest RC (release candidate) bits that were released last Monday. What disappointed me when I went to the Silverlight 4 Information Page is that it told me what to install, but not what to uninstall first. Uninstalling I'm not entirely sure if I had to uninstall anything, or if installing the new stuff would just work, but in poking around the web I found posts stating that you must uninstall the following items first. Unfortunately I'm going by memory here and have not been able to find my way back to the magic page I found in the myriad of posts that I went through: Microsoft VisualStudio Beta 2 Microsoft .NET Framework 4 Extended (apparently this must be done *before* the next one) Microsoft .NET Framework Client Profile Microsoft Silverlight 4 Tools for Visual Studio 2010 WCF RIA Services Preview for Visual Studio 2010 While I was at it, I removed a bunch of other stuff, like Blend 3, Blend 4, the SDK's associated with them, and a bunch other stuff that was old. Of course, I didn't really want/need to keep any Silverlight 3 stuff around as I am developing Task-It in Silverlight 4. If I need a Silverlight 3 environment at some point I'll set it up in a virtual environment. NOTE: One thing that I did not uninstall is the Microsoft Silverlight 4 Toolkit November 2009. The reason is that they have not released the March version yet, so if you uninstall this, youll end up having to reinstall it. Installing OK, now that I had all of that old stuff off my machine, now it was time to get the new stuff. For this part I liked Tim Heuer's post, A Guide to What has Changed in Silverlight 4 RC better than the Silverlight 4 Information Page. VisualStudio 2010 RC - I installed Ultimate, but you may not need that version. No harm, it's free for now anyway. I downloaded the .exe and the 3 .rar files, then ran the .exe. I then extracted the contents of the ISO (using WinZip) to a new directory, and now had Setup.exe, a bunch of .cab files and some other assorted stuff. I simply ran Setup.exe and chose custom install (only because I wanted to uncheck Visual C++...I don't really have a need for that) Silverlight 4 Tools for Visual Studio 2010 - As mentioned in Tim's blog post, this installs this installs Silverlight developer runtime, SDK, tools, and this installs Silverlight developer runtime, SDK, tools, and WCF RIA Services. WCF RIA Services Toolkit March 2010 - I'm not sure if/when I'll need any of this stuff, but no harm in installing it anyway. Expression Blend 4 beta - Only if you plan to use Blend, which I do. Windows Phone Developer Tools - Only if you are interested in playing with Windows Phone 7 development. Wrap Up Hopefully I got those steps right. If anyone finds anything I've missed, please just add a comment to this post and I'll update it accordingly.Did you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.

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• SQL SERVER – Curious Case of Disappearing Rows – ON UPDATE CASCADE and ON DELETE CASCADE – T-SQL Example – Part 2 of 2

  - by pinaldave

  Yesterday I wrote a real world story of how a friend who thought they have an issue with intrusion or virus whereas the issue was really in the code. I strongly suggest you read my earlier blog post Curious Case of Disappearing Rows – ON UPDATE CASCADE and ON DELETE CASCADE – Part 1 of 2 before continuing this blog post as this is second part of the first blog post. Let me reproduce the simple scenario in T-SQL. Building Sample Data USE [TestDB] GO -- Creating Table Products CREATE TABLE [dbo].[Products]( [ProductID] [int] NOT NULL, [ProductDesc] [varchar](50) NOT NULL, CONSTRAINT [PK_Products] PRIMARY KEY CLUSTERED ( [ProductID] ASC )) ON [PRIMARY] GO -- Creating Table ProductDetails CREATE TABLE [dbo].[ProductDetails]( [ProductDetailID] [int] NOT NULL, [ProductID] [int] NOT NULL, [Total] [int] NOT NULL, CONSTRAINT [PK_ProductDetails] PRIMARY KEY CLUSTERED ( [ProductDetailID] ASC )) ON [PRIMARY] GO ALTER TABLE [dbo].[ProductDetails] WITH CHECK ADD CONSTRAINT [FK_ProductDetails_Products] FOREIGN KEY([ProductID]) REFERENCES [dbo].[Products] ([ProductID]) ON UPDATE CASCADE ON DELETE CASCADE GO -- Insert Data into Table USE TestDB GO INSERT INTO Products (ProductID, ProductDesc) SELECT 1, 'Bike' UNION ALL SELECT 2, 'Car' UNION ALL SELECT 3, 'Books' GO INSERT INTO ProductDetails ([ProductDetailID],[ProductID],[Total]) SELECT 1, 1, 200 UNION ALL SELECT 2, 1, 100 UNION ALL SELECT 3, 1, 111 UNION ALL SELECT 4, 2, 200 UNION ALL SELECT 5, 3, 100 UNION ALL SELECT 6, 3, 100 UNION ALL SELECT 7, 3, 200 GO Select Data from Tables -- Selecting Data SELECT * FROM Products SELECT * FROM ProductDetails GO Delete Data from Products Table -- Deleting Data DELETE FROM Products WHERE ProductID = 1 GO Select Data from Tables Again -- Selecting Data SELECT * FROM Products SELECT * FROM ProductDetails GO Clean up Data -- Clean up DROP TABLE ProductDetails DROP TABLE Products GO My friend was confused as there was no delete was firing over ProductsDetails Table still there was a delete happening. The reason was because there is a foreign key created between Products and ProductsDetails Table with the keywords ON DELETE CASCADE. Due to ON DELETE CASCADE whenever is specified when the data from Table A is deleted and if it is referenced in another table using foreign key it will be deleted as well. Workaround 1: Design Changes – 3 Tables Change the design to have more than two tables. Create One Product Mater Table with all the products. It should historically store all the products list in it. No products should be ever removed from it. Add another table called Current Product and it should contain only the table which should be visible in the product catalogue. Another table should be called as ProductHistory table. There should be no use of CASCADE keyword among them. Workaround 2: Design Changes - Column IsVisible You can keep the same two tables. 1) Products and 2) ProductsDetails. Add a column with BIT datatype to it and name it as a IsVisible. Now change your application code to display the catalogue based on this column. There should be no need to delete anything. Workaround 3: Bad Advices (Bad advises begins here) The reason I have said bad advices because these are going to be bad advices for sure. You should make necessary design changes and not use poor workarounds which can damage the system and database integrity further. Here are the examples 1) Do not delete the data – well, this is not a real solution but can give time to implement design changes. 2) Do not have ON CASCADE DELETE – in this case, you will have entry in productsdetails which will have no corresponding product id and later on there will be lots of confusion. 3) Duplicate Data – you can have all the data of the product table move to the product details table and repeat them at each row. Now remove CASCADE code. This will let you delete the product table rows without any issue. There are so many things wrong this suggestion, that I will not even start here. (Bad advises ends here)  Well, did I miss anything? Please help me with your suggestions. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology

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• Is the Internet Making us Smarter or Not?

  - by BuckWoody

  I’ve been reading recently about an exchange among some very bright folks, some who posit that the Internet with its instant-on, sometimes-right, big-statement-wins mentality is making people think in a more shallow way, teaching us to rely on others as experts and diluting our logical thought process. Others state that it broadens our perspective and extends our mental reach. Whenever I see this kind of exchange on two ends of a spectrum, I begin to wonder if both sides might be correct.   I can certainly say that I have changed my way of learning, reading, and social interactions because of the Internet. And my tolerance for reading long missives has indeed gone down. I tend to (mentally and literally) “bookmark” things I never seem to have time to get back to. But I also agree that I’ve been exposed to thoughts, ideas and people I never would have encountered any other way. So how to deal with this dichotomy?   Well, I’m going to go off and think about it. No, I’m really going to go off for a full week to a cabin I’ve rented in a National Forest in the Midwest. It has no indoor plumbing, phones, Internet connections or anything else – only a bed to sleep in and a place to cook a little. I’m taking one book, some paper, and a guitar with me and that’s it. I plan to spend my days walking, reading a little, playing a little on the guitar, but mostly just thinking. Those of you who know me might find this unusual. I’m an always-on, hyper-caffeinated, overly-busy, connected person. I haven’t taken a vacation in five years, at least for more than two or three days at a time. Even then, I keep us on the move constantly – our vacations aren’t cruises or anything like that. I check e-mail, post and all that. When I’m not on vacation, I live with and leverage lots of technology, and work with those that do the same. This, however, is a really “unplugged” event, and I’m hoping that it will let me unpack the things I’ve been stuffing in my head. I plan to spend a lot of time on a single subject, writing notes, thinking, and writing more notes.   So after I post tomorrow's “quote of the day” I’ll be “going dark” for a week. No twitter, FaceBook, LinkedIn, e-mail, chat, none of my five blogs will get updated, and I’ll have to turn in my two articles for InformIT.com early. I won’t have access to my college class portal, so my students will be without me for a week. I will really be offline. I’ll see you in a week – hopefully a little more educated. See you then.   Share this post: email it! | bookmark it! | digg it! | reddit! | kick it! | live it!

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• Is the Internet Making us Smarter or Not?

  - by BuckWoody

  I’ve been reading recently about an exchange among some very bright folks, some who posit that the Internet with its instant-on, sometimes-right, big-statement-wins mentality is making people think in a more shallow way, teaching us to rely on others as experts and diluting our logical thought process. Others state that it broadens our perspective and extends our mental reach. Whenever I see this kind of exchange on two ends of a spectrum, I begin to wonder if both sides might be correct.   I can certainly say that I have changed my way of learning, reading, and social interactions because of the Internet. And my tolerance for reading long missives has indeed gone down. I tend to (mentally and literally) “bookmark” things I never seem to have time to get back to. But I also agree that I’ve been exposed to thoughts, ideas and people I never would have encountered any other way. So how to deal with this dichotomy?   Well, I’m going to go off and think about it. No, I’m really going to go off for a full week to a cabin I’ve rented in a National Forest in the Midwest. It has no indoor plumbing, phones, Internet connections or anything else – only a bed to sleep in and a place to cook a little. I’m taking one book, some paper, and a guitar with me and that’s it. I plan to spend my days walking, reading a little, playing a little on the guitar, but mostly just thinking. Those of you who know me might find this unusual. I’m an always-on, hyper-caffeinated, overly-busy, connected person. I haven’t taken a vacation in five years, at least for more than two or three days at a time. Even then, I keep us on the move constantly – our vacations aren’t cruises or anything like that. I check e-mail, post and all that. When I’m not on vacation, I live with and leverage lots of technology, and work with those that do the same. This, however, is a really “unplugged” event, and I’m hoping that it will let me unpack the things I’ve been stuffing in my head. I plan to spend a lot of time on a single subject, writing notes, thinking, and writing more notes.   So after I post tomorrow's “quote of the day” I’ll be “going dark” for a week. No twitter, FaceBook, LinkedIn, e-mail, chat, none of my five blogs will get updated, and I’ll have to turn in my two articles for InformIT.com early. I won’t have access to my college class portal, so my students will be without me for a week. I will really be offline. I’ll see you in a week – hopefully a little more educated. See you then.   Share this post: email it! | bookmark it! | digg it! | reddit! | kick it! | live it!

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• Where Twitter Stands Heading Into 2013

  - by Mike Stiles

  As Twitter continued throughout 2012 to be a stage on which global politics and culture played itself out, the company itself underwent some adjustments that give us a good indication of what users and brands can expect from the platform in 2013. The power of the network did anything but fade. Celebrities continued to use it to connect one-on-one. Even the Pope signed on this year. It continued to fuel revolutions. It played an exponentially large factor in this US Presidential election. And around the world, the freedom to speak was challenged as users were fired, sued, sometimes even jailed for their tweets. Expect more of the same in 2013, as Twitter has entrenched itself, for individuals, causes and brands, as the fastest, easiest, most efficient way to message the masses so some measure of impact can come from it. It’s changed everything, and it’s not finished. These fun facts reveal the position of strength with which Twitter enters 2013: It now generates a billion tweets every 2.5 days It has 500 million+ users The average Twitter user has tweeted 307 times 32% of everyone using the Internet uses Twitter It’s expected to bring in $540 million in ad revenue by 2014 11 new accounts are created every second High-level Executive Summary: people love it, people use it, and they’re going to keep loving and using it. Whether or not outside developers love it is a different matter. 2012 marked a shift from welcoming the third party support that played at least some role in Twitter being so warmly embraced, to discouraging anything that replicates what Twitter can do itself…or plans to do itself. It’s not the open playground it once was. Now Twitter must spend 2013 proving it can innovate in-house and keep us just as entranced. Likewise, Twitter is distancing itself from Facebook. Images from the #1 platform’s Instagram don’t work on Twitter anymore, and Twitter’s rolling out their own photo filter product. Where the two have lived in a “plenty of room for everybody” symbiosis up to now, 2013 could see the giants ramping up a full-on rivalry. Twitter is exhibiting a deliberate strategy. Updates have centered on more visually appealing search results, and making finding and sharing content easier. Deals have been cut with some media entities so their content stands out. CEO Dick Costolo has said tweets aren’t the attraction, they’re what leads you to content. Twitter aims to be a key distributor of media and info. Add the addition of former News Corp. President Peter Chernin to the board, and their hashtag landing page experience for events, and their media behemoth ambitions get pretty clear. There are challenges ahead and Costolo has also laid those out; entry into China, figuring out how to have Twitter deliver both comprehensive and relevant, targeted experiences, and the visualization of big data. What does this mean for corporations? They can expect a more media-rich evolution and growing emphases on imagery. They can expect more opportunities to create great media content and leverage Twitter for its distribution. And they can expect new ways to surface in searches. Are brands diving in? 56% of customer tweets to companies get completely and totally ignored. Ugh. A study Twitter recently conducted with Compete shows people who see tweets from retailers are more likely to buy a product. And, the more retailer tweets they see, the more likely they are to purchase on the retail site. As more of those tweets point to engaging media content from the brand, the results should get even better. Twitter appears ready for 2013. Enterprise brands have some work to do. @mikestilesPhoto Stuart Miles, freedigitalphotos.net

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• Government Mandates and Programming Languages

  A recent SEC proposal (which, at over 600 pages, I havent read in any detail) includes the following: We are proposing to require the filing of a computer program (the waterfall computer program, as defined in the proposed rule) of the contractual cash flow provisions of the securities in the form of downloadable source code in Python, a commonly used computer programming language that is open source and interpretive. The computer program would be tagged in XML and required to be filed with the Commission as an exhibit. Under our proposal, the filed source code for the computer program, when downloaded and run (by loading it into an open Python session on the investors computer), would be required to allow the user to programmatically input information from the asset data file that we are proposing to require as described above. We believe that, with the waterfall computer program and the asset data file, investors would be better able to conduct their own evaluations of ABS and may be less likely to be dependent on the opinions of credit rating agencies. With respect to any registration statement on Form SF-1 (Section 239.44) or Form SF-3 (Section 239.45) relating to an offering of an asset-backed security that is required to comply with Item 1113(h) of Regulation AB, the Waterfall Computer Program (as defined in Item 1113(h)(1) of Regulation AB) must be written in the Python programming language and able to be downloaded and run on a local computer properly configured with a Python interpreter. The Waterfall Computer Program should be filed in the manner specified in the EDGAR Filer Manual. I dont see how it can be in investors best interests that the SEC demand a particular programming language be used for software related to investment data.  I have a feeling that investors who use computers at all already have software with which they are familiar, and that the vast majority of them are not running an open source scripting language on their machines to do their financial analysis.  In fact, I would wager that most of them are using tools like Excel, and if they really need to script anything, its being done with VBA in Excel. Now, Im not proposing that the SEC should require that the data be provided in Excel format with VBA scripts included so everyone can easily access the data (despite the fact that this would actually be pretty useful generally).  Rather, I think it is ill-advised for a government agency to make recommendations of this nature, period.  If the goal of the recommendation is to ensure that the way things work is codified in a transparent manner, than I can certainly respect that.  It seems to me that this could be accomplished without dictating the technology to use.  To wit: An Excel document could contain all of the data as well as the formulae necessary, and most likely would not require the end-user to install anything on their machine The SEC could simply create a calculator in the cloud such that any/all investors could use a single canonical web-based (or web service based) tool Millions of Java and .NET developers could write their own implementations You can read more about this issue, including the favorable position on it, on Jayanth Varmas blog. Did you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.

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• Questions to ask to ensure someone understands programming? (and iOS)

  - by Stephen J

  So, I've been tutoring my friend for 2 years. Most people learn programming on their own in 3-6 months, (sans algorithms). It's confusing 'cause he'll run anywhere I tell him to, understands how to read C and C++ honestly better than the average college student, and he'll modify and repeat anything I do... but for the love of god he doesn't move on to new things and he still has test anxiety. I've recently realized he's copied and toyed with existing, but not once gained an understanding of why. I was under the impression he was learning fast because he could write it, but when you say "Make a function that takes an NSString" and he says "How?" and I say "The same way you make ANY function that takes any parameter, NSString is just a type like int" and all I hear is "No, it's an NSString, it's a special thing." and we get into an arguing match 'cause I'm like "It's just a class like any other class, you've used them for months now" and blah... I've subconsciously avoided comprehension questions because of this. Anyway, if you have him copy a program and say "Just initialize it" "Where?" "I don't care, didLoad or initWithCoder or Awake from nib, anywhere it gets initialized" and "No, it has to be exactly where you had it!" "No it doesn't!" I'm sick of this, but he won't give up. So I'm done avoiding these yelling matches and becoming a sadist from now on. I would like some help in finding questions to ask him that force him to understand what he's doing. I'd like some help and any resources I can find. CQuestions looked like a good site, but now I need some iPhone stuff. For example: *What do properties do? How are they changed? How do you change the name of the getter? *Why are Booleans inefficent? What advantage does int have over a boolean and how does the bit-shift operator help? *What does Copy do to a string? *What's the difference between a view controller and a uiview? *Write a program from memory that displays blah on screen, and flashes each view one by one. From beginner up to intermediate, hobbyist with some algebra at most. I'm just looking for resources to work with. I left in backstory so you know to "twist" the questions so he doesn't know he's supposed to init a variable here or there, but has to figure it out, and learn why it goes "here" or that "anywhere is fine as long as it's". Sample programs, anything. I'm relatively open about this because, being a programmer, I seriously doubt he's the only one who has this issue. I'd like to know how others have overcome similar. What made things "click"? for you? Did you have a hard time finding answers on Google, and how did you learn a better way to find what you were looking for? (He's so exact, he'll search for how to write a checkers program with color X and Y inside a uiview, as his search string, instead of breaking it up into components, I need help with that too, and believe it is related). This type of problem has to remind one of us of someone they know. So, Exercises to force them to think? Ways we overcame this thing in the past? I greatly appreciate any help.

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• Apache config that uses two document roots based on whether the requested resource exists in the first [closed]

  - by mattalexx

  Background I have a client site that consists of a CakePHP installation and a Magento installation: /web/example.com/ /web/example.com/app/ <== CakePHP /web/example.com/app/webroot/ <== DocumentRoot /web/example.com/app/webroot/store/ <== Magento /web/example.com/config/ <== Site-wide config /web/example.com/vendors/ <== Site-wide libraries The server runs Apache 2.2.3. The problem The whole company has FTP access and got used to clogging up the /web/example.com/, /web/example.com/app/webroot/, and /web/example.com/app/webroot/store/ directories with their own files. Sometimes these files need HTTP access and sometimes they don't. In any case, this mess makes my job harder when it comes to maintaining the site. Code merges, tarring the live code, etc, is very complicated and usually requires a bunch of filters. Abandoned solution At first, I thought I would set up a new subdomain on the same server, move all of their files there, and change their FTP chroot. But that wouldn't work for these reasons: Firstly, I have no idea (and neither do they remember) what marketing materials they've sent out that contain URLs to certain resources they've uploaded to the server, using the main domain, and also using abstract subdomains that use the main virtual host because it has ServerAlias *.example.com. So suddenly having them only use static.example.com isn't feasible. Secondly, The PHP scripts in their projects are potentially very non-portable. I want their files to stay in as similar an environment as they were built as I can. Also, I do not want to debug their code to make it portable. Half-baked solution After some thought, I decided to find a way to section off the actual website files into another directory that they would not touch. The company's uploaded files would stay where they were. This would ensure that I didn't break any of their projects that needed HTTP access. It would look something like this: /web/example.com/ <== A bunch of their files are in here /web/example.com/app/webroot/ <== 1st DocumentRoot; A bunch of their files are in here /web/example.com/app/webroot/store/ <== Some more are in here /web/example.com/site/ <== New dir; Contains only site files /web/example.com/site/app/ <== CakePHP /web/example.com/site/app/webroot/ <== 2nd DocumentRoot /web/example.com/site/app/webroot/store/ <== Magento /web/example.com/site/config/ <== Site-wide config /web/example.com/site/vendors/ <== Site-wide libraries After I made this change, I would not need to pay attention to anything except for the stuff within /web/example.com/site/ and my job would be a lot easier. I would be the only one changing stuff in there. So here's where the Apache magic would happen: I need an HTTP request to http://www.example.com/ to first use /web/example.com/app/webroot/ as the document root. If nothing is found (no miscellaneous uploaded company projects are found), try finding something within /web/example.com/site/app/webroot/. Another thing to keep in mind is, the site might have some problems if the $_SERVER['DOCUMENT_ROOT'] variable reads /web/example.com/app/webroot/ but the actual files are within /web/example.com/site/app/webroot/. It would be better if the DOCUMENT_ROOT environment variable could be /web/example.com/site/app/webroot/ for anything within the /web/example.com/site/app/webroot/ directory. Conclusion Is my half-baked solution possible with Apache 2.2.3? Is there a better way to solve this problem?

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• What Counts For a DBA – Depth

  - by Louis Davidson

  SQL Server offers very simple interfaces to many of its features. Most people could open up SSMS, connect to a server, write a simple query and see the results. Even several of the core DBA tasks are deceptively straightforward. It doesn’t take a rocket scientist to perform a basic database backup or run a trace (even using the newfangled Extended Events!). However, appearances can be deceptive, and often times it is really important that a DBA understands not just the basics of how to perform a task, but why we do a task, and how that task works. As an analogy, consider a child walking into a darkened room. Most would know that they need to turn on the light, and how to do it, so they flick the switch. But what happens if light fails to shine forth. Most would immediately tell you that you need to consider changing the light bulb. So you hop in the car and take them to the local home store and instruct them to buy a replacement. Confronted with a 40 foot display of light bulbs, how will they decide which of the hundreds of types of bulbs, of different types, fittings, shapes, colors, power and efficiency ratings, is the right choice? Obviously the main lesson the child is going to learn this day is how to use their cell phone as a flashlight so they don’t have to ask for help the next time. Likewise, when the metaphorical toddlers who use your database server have issues, they will instinctively know something is wrong, and may even have some idea what caused it, but will have no depth of knowledge to figure out the right solution. That is where the DBA comes in and attempts to save the day. However, when one looks beneath the shiny UI, SQL Server has its own “40 foot display of light bulbs”, in the form of the tremendous number of tools and the often-bewildering amount of information they can present to the DBA, to help us find issues. Unfortunately, resorting to guesswork, to trying different “bulbs” over and over, hoping to stumble on the answer. This is where the right depth of knowledge goes a long way. If we need to write a SELECT statement, then knowing the syntax and where to find the data is not enough. Knowledge of indexes and query plans is essential. Without it, we might hit on a query that “works”, but we are basically still a user, not a programmer, because we have no real control over our platform. Is that level of knowledge deep enough? Probably not, since knowledge of the underlying metadata and structures would be very useful in helping us make sense of any query plan. Understanding the structure of an index makes the “key lookup” operator not sound like what you do when someone tapes your car key to the ceiling. So is even this level of understanding deep enough? Do we need to understand the memory architecture used to process the query? It might be a comforting level of knowledge, and will doubtless come in handy at some point, but is not strictly necessary in most cases. Beyond that lies (more or less) full knowledge of SQL language and the intricacies of every step the SQL Server engine takes to process our query. My personal theory is that, as a professional, our knowledge of a given task should extend, at a minimum, one level deeper than is strictly necessary to perform the task. Anything deeper can be left to the ridiculously smart, or obsessive, or both. As an example. tasked with storing an integer value between 0 and 99999999, it’s essential that I know that choosing an Integer over Decimal(8,0) will likely offer performance benefits. It is then useful that I also understand the value of adding a CHECK constraint, to make sure the values are valid to the desired range; and comforting that I know a little about the underlying processors, registers and computer math. Anything further, I leave to the likes of Joe Chang, whose recent blog post on the topic offers depth by the bucketful!  

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• When will EBS 12.2 be released?

  - by Steven Chan (Oracle Development)

  The most frequently asked question at OpenWorld this year was, "When will EBS 12.2 be released?" Sadly, Oracle's communication policies prohibit us from speculating about release dates for unreleased software. We are not permitted to give estimates, rough timelines, guesses, or anything else that remotely resembles specific guidance on release dates. You can monitor My Oracle Support and this blog for updates on EBS 12.2.  I'll post them here as soon as they're available.  I'm embedding an old favourite from 2007 in its entirety here, since it applies equally to new releases as well as certifications. "Loose Lips Sink Ships" (March 20, 2007)If I were to sort emails in my inbox into groups, the biggest -- by far -- would be the one for emails that start with, "When will _____ be certified with the E-Business Suite?"  I answer these dutifully but know that my replies can sometimes be maddening, for two reasons:  technical uncertainty, and Oracle's rules for such communications. On the Spiral Model of CertificationsTechnology stack certifications tend to be highly iterative in nature.  As a result, statements about certification dates tend to be accurate only when made in hindsight.  Laypeople are horrified to hear this, but it's the ugly truth.  Uncertainty is simply inherent to the process.  I've become inured to it over the years, but it might come as a surprise to you that it can take many cycles to get fully-released software to work together.  Take this scenario: We test a particular combination of Component A and B. If we encounter a problem, say, with Component A, we log a bug. We receive a new version of Component A. The process iterates again. The reality is this: until a certification is completed and released, there's no accurate way of telling how many iterations are yet to come.  This is true regardless of the number of iterations that have already been completed.  Our Lips Are SealedGenerally, people understand that things are subject to change, so the second reason I can't say anything specific is actually much more important than the first.  "Loose lips might sink ships" was coined in World War II in an effort to remind people that careless talk can have serious consequences.  Curiously, this applies to Oracle's communications about upcoming features, configurations, and releases, too.  As a publicly traded company, we have very strict policies that prohibit us from linking specific releases to specific dates.  If you've ever listened to an earnings call with analysts, you'll often hear them asking, "Can you add a little more color to that statement?"  For certifications, color is usually the only thing that I have.  Sometimes I can provide a bit more information about the technical nature of the certification in question, such as expected footprints or version levels.  I can occasionally share technical issues that we've found, too, to convey the degree of risk or complexity involved in the certification.  Aside from that, there's little additional information about specific dates, date ranges, or even speculation about dates that I can provide... that is, without having one of those uncomfortable conversations with Oracle Legal.  So, as much as it pains me to do so, when it comes to dates, I'm always forced to conclude with a generic reply that blandly states one of the following: We're working on that certification right now That certification is in the pipeline but hasn't been started yet We don't have plans for that certification Don't Shoot the MessengerThankfully, I've developed a thick skin over the years -- which is a good thing, considering the colorful and energetic responses I've received over the years after answering these questions.  However, on behalf of my Oracle colleagues who are faced with these questions every day in the field, I urge you to remember that they're required to follow these same corporate rules about date disclosures.  It never hurts to ask, but don't be too disappointed if we can't provide you with a detailed answer.  The Go-Go's had it right, after all.  Related Articles Webcast Replay Available: Technical Preview of EBS 12.2 Online Patching

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• Is Your Company Social on the Inside?

  - by Mike Stiles

  As we talk about the extension of social from an outbound-facing marketing tool to a platform that will reach across the entire enterprise, servicing multiple functions of that enterprise, it might be time to take a look at how social can be effectively employed for internal communications. Remember the printed company newsletter? Yeah, nobody reads it. Remember the emailed company newsletter? Yeah, nobody reads it. Why not? Shouldn’t your employees care about the company more than anything else in life and be voraciously hungry for any information related to it? The more realistic prospect is that a company’s employees don’t behave much differently at work where information is concerned than they do in their personal lives. They “tune in” to information that’s immediately relevant to them, that peaks their interest, and/or that’s presented in a visually engaging way. That currently makes an internal social platform the most ideal way to communicate within the organization. It not only facilitates more immediate, more targeted (and thus more relevant) messaging from the company out to employees, it sets a stage for employees to communicate with each other and efficiently get answers to questions from peers. It’s a collaboration tool on steroids. If you build such an internal social portal and you do it right, will employees use it? Considering social media has officially been declared more addictive than cigarettes, booze and sex…probably. But what does it mean to do an internal social platform “right”? The bar has been set pretty high. Your employees are used to Twitter and Facebook, and would roll their eyes at anything less simple or harder to navigate than those. All the Facebook best practices would apply to your internal social as well, including the importance of managing posting frequency, using photos and video, moderation & response, etc. And don’t worry, you won’t be the first to jump in. WPP's global digital agency Possible has its own social network called Colab. Nestle has “The Nest.” Red Robin’s got one. I myself got an in-depth look at McGraw-Hill’s internal social platform at Blogwell NYC. Some of these companies are building their own platforms, others are buying them off the shelf or customizing readymade solutions. But you won’t be the last either. Prescient Digital Media and the IABC learned 39% of companies don’t offer employees any social tools. Not a social network, not discussion forums, not even IM. And a great many continue to ban the use of Facebook and Twitter on the premises. That’s pretty astonishing since social has become as essential a modern day communications tool as the telephone. But such holdouts will pay a big price for being mired in fear while competitors exploit social connections unchallenged. Fish where the fish are. If social has become the way people communicate and take in information, let that be the way communication is trafficked in the organization.

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• Software Center seems to freeze system when installing, syslog has "blocked for more than 120 seconds" errors

  - by nbm

  12.04 (precise) 64-bit Kernel Linux 3.2.0-39 3.6GB memory Intel Core 2 Duo CPU @ 2.40GHz x2 WUBI-installed Ubuntu running on a MacBook Pro 7.1 with OSX running Vista via Boot Camp (hey, I like lots of OS's m'kay?) When installing from Ubuntu software center my system very frequently freezes. This has happened 4 of the last 5 installs. Most recently I was installing the Google Earth .deb from Google's website: clicking the .deb file automatically opens Software Center (otherwise I would have used Synaptic, as I've grown to expect Software Center to freeze my system and I'm rather tired of it.) By "freeze" I mean nothing works: no dash, no launcher, no mouse movement, no alt-tab, can't open terminal (keyboard does not work). Software center does show the "installing" icon but after that it greys out and I can't click anything. REISUB has no effect but a cold power-down and restart is possible. Occasionally, after 5-10 minutes, I'll be able to move the mouse / use the keyboard and run a launcher command or two, although other open apps (Chrome and Software Center) will still be greyed-out/frozen. (I've never waited longer than that - if still unresponsive after 15 minutes I just power down and restart.) Most recently, which is why I am finally posting a question, I waited about 15 minutes and was finally able to open System Monitor while this was going on. Processes tells me that System Monitor is using about 20% of CPU, and nothing else is using much (zeros mostly). In fact I didn't even see Software Center listed? However at this point the system finally partially unfroze, the installation completed, and while I wasn't about to close Software Center I was able to do a system shutdown and fresh restart and I went and took a look at the syslog. In /var/log/syslog I see a lot of ":blocked for more than 120 seconds" messages. Similar to ubuntu hang out with this message :blocked for more than 120 seconds Which has not been answered, and I'm not running a virtual machine. My full syslog with stack traces looks very, very similar to this: Why do tasks on Amazon Xen instance block for over 120 seconds causing server to hang? Note that that question was solved, but that's because the problem was being caused by Amazon and Amazon fixed the bug. I'm not running anything Amazon-related. My syslog does look very similar, however. My question is also similar to this: Troubleshooting server hang But the referenced "duplicate" in that question is about how to kill processes/restart when the system freezes. I know how to kill processes and restart. I want to figure out what is causing the problem so I can try to fix it. I realize that I could just use Synaptic instead of Ubuntu Software Center, but I'd like to try to solve the problem if possible. I'm thinking I should perhaps submit a bug report, but I wanted to first see if anyone else was having any similar problems, and if so what you all did to fix it. I see a number of questions about Software Center freezing and others, including those I linked, about the "blocked for more than 120 seconds" log error, but I didn't see any question that links the two. I did save a copy of the syslog report if anyone wants to see it, but as mentioned it's quite similar to the one posted in the Amazon-related question...and I didn't want to take up even more space unnecessarily as, my apologies - this question has already become extremely verbose!

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• Using 3rd Party JavaScript Plugins Hardwired With &lsquo;document.write&rsquo;

  - by ToStringTheory

  Introduction Have you ever had the need to implement a 3rd party JavaScript plugin, but your needs didn’t fit the model and usage defined by the API or documentation of the plugin?  Recently I ran into this issue when I was trying to implement a web snapshot plugin into our site.  To use their plugin, you had to include a script tag to the plugin on their server with an API key.  The second part of the usage was to include a <script> tag around a function call wherever you wanted a snapshot to appear. The Problem When trying to use the service, the images did not display.  I checked a couple of things and didn’t find anything wrong at first..  It wasn’t until I looked at the function that was called by the inline script did I find the issue – a call to the webservice, followed by a call to ‘document.write’ in its callback.  The solution in which I was trying to implement the plugin happened to be in response to an AJAX call after the document had completely loaded.  After the page has loaded, document.write does nothing. My first thought for a solution was to just cache the script from the service, and edit it do something like a return function or callback that I could use to edit the document from.  However, I quickly discovered that there is no way to cache the script from the service, as it had a hash in the function where it would call the server.  The hash was updated every few seconds/minutes, expiring old hashes.  This meant that I wouldn’t be able to edit the script and upload a new version to my server, as the script would not work after a few minutes from originally getting the script from the service. Solution The solution eluded me until I realized that this was JavaScript I was dealing with.  A language designed so that you could do just about anything to any library, function, or object…  At this point, the solution was simple – take control of the document.write function.  Using a buffer variable, and a simple function call, it is eerily simple to perform: //what would have been output to the document var buffer = ""; //store a reference to the real document.write var dw = document.write; //redefine document.write to store to our buffer document.write = function (str) {buffer += str;} //execute the function containing calls to document.write eval('{function encapsulated in <script></script> tags}'); //restore the original document.write function (just in case) document.write = dw; That’s it.  Instead of using the script tags where I wanted to include a snapshot, I called a function passing in the URL to the page I wanted a snapshot of.  After that last line of code, what would have been output to the document (or not in the case of the ajax call) was instead stored in buffer. Conclusion While the solution itself is simple, coming from a background much more footed in the .Net platform, I believe that this is a prime example of always keeping the language that you are working in in mind.  While this may seem obvious at first, as I KNEW I was in JavaScript, I never thought of taking control of the document.write function because I am more accustomed to the .Net world.  I can’t simply replace the functionality of Console.WriteLine.

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• Stored Procedures with SSRS? Hmm… not so much

  - by Rob Farley

  Little Bobby Tables’ mother says you should always sanitise your data input. Except that I think she’s wrong. The SQL Injection aspect is for another post, where I’ll show you why I think SQL Injection is the same kind of attack as many other attacks, such as the old buffer overflow, but here I want to have a bit of a whinge about the way that some people sanitise data input, and even have a whinge about people who insist on using stored procedures for SSRS reports. Let me say that again, in case you missed it the first time: I want to have a whinge about people who insist on using stored procedures for SSRS reports. Let’s look at the data input sanitisation aspect – except that I’m going to call it ‘parameter validation’. I’m talking about code that looks like this: create procedure dbo.GetMonthSummaryPerSalesPerson(@eomdate datetime) as begin     /* First check that @eomdate is a valid date */     if isdate(@eomdate) != 1     begin         select 'Please enter a valid date' as ErrorMessage;         return;     end     /* Then check that time has passed since @eomdate */     if datediff(day,@eomdate,sysdatetime()) < 5     begin         select 'Sorry - EOM is not complete yet' as ErrorMessage;         return;     end         /* If those checks have succeeded, return the data */     select SalesPersonID, count(*) as NumSales, sum(TotalDue) as TotalSales     from Sales.SalesOrderHeader     where OrderDate >= dateadd(month,-1,@eomdate)         and OrderDate < @eomdate     group by SalesPersonID     order by SalesPersonID; end Notice that the code checks that a date has been entered. Seriously??!! This must only be to check for NULL values being passed in, because anything else would have to be a valid datetime to avoid an error. The other check is maybe fair enough, but I still don’t like it. The two problems I have with this stored procedure are the result sets and the small fact that the stored procedure even exists in the first place. But let’s consider the first one of these problems for starters. I’ll get to the second one in a moment. If you read Jes Borland (@grrl_geek)’s recent post about returning multiple result sets in Reporting Services, you’ll be aware that Reporting Services doesn’t support multiple results sets from a single query. And when it says ‘single query’, it includes ‘stored procedure call’. It’ll only handle the first result set that comes back. But that’s okay – we have RETURN statements, so our stored procedure will only ever return a single result set.  Sometimes that result set might contain a single field called ErrorMessage, but it’s still only one result set. Except that it’s not okay, because Reporting Services needs to know what fields to expect. Your report needs to hook into your fields, so SSRS needs to have a way to get that information. For stored procs, it uses an option called FMTONLY. When Reporting Services tries to figure out what fields are going to be returned by a query (or stored procedure call), it doesn’t want to have to run the whole thing. That could take ages. (Maybe it’s seen some of the stored procedures I’ve had to deal with over the years!) So it turns on FMTONLY before it makes the call (and turns it off again afterwards). FMTONLY is designed to be able to figure out the shape of the output, without actually running the contents. It’s very useful, you might think. set fmtonly on exec dbo.GetMonthSummaryPerSalesPerson '20030401'; set fmtonly off Without the FMTONLY lines, this stored procedure returns a result set that has three columns and fourteen rows. But with FMTONLY turned on, those rows don’t come back. But what I do get back hurts Reporting Services. It doesn’t run the stored procedure at all. It just looks for anything that could be returned and pushes out a result set in that shape. Despite the fact that I’ve made sure that the logic will only ever return a single result set, the FMTONLY option kills me by returning three of them. It would have been much better to push these checks down into the query itself. alter procedure dbo.GetMonthSummaryPerSalesPerson(@eomdate datetime) as begin     select SalesPersonID, count(*) as NumSales, sum(TotalDue) as TotalSales     from Sales.SalesOrderHeader     where     /* Make sure that @eomdate is valid */         isdate(@eomdate) = 1     /* And that it's sufficiently past */     and datediff(day,@eomdate,sysdatetime()) >= 5     /* And now use it in the filter as appropriate */     and OrderDate >= dateadd(month,-1,@eomdate)     and OrderDate < @eomdate     group by SalesPersonID     order by SalesPersonID; end Now if we run it with FMTONLY turned on, we get the single result set back. But let’s consider the execution plan when we pass in an invalid date. First let’s look at one that returns data. I’ve got a semi-useful index in place on OrderDate, which includes the SalesPersonID and TotalDue fields. It does the job, despite a hefty Sort operation. …compared to one that uses a future date: You might notice that the estimated costs are similar – the Index Seek is still 28%, the Sort is still 71%. But the size of that arrow coming out of the Index Seek is a whole bunch smaller. The coolest thing here is what’s going on with that Index Seek. Let’s look at some of the properties of it. Glance down it with me… Estimated CPU cost of 0.0005728, 387 estimated rows, estimated subtree cost of 0.0044385, ForceSeek false, Number of Executions 0. That’s right – it doesn’t run. So much for reading plans right-to-left... The key is the Filter on the left of it. It has a Startup Expression Predicate in it, which means that it doesn’t call anything further down the plan (to the right) if the predicate evaluates to false. Using this method, we can make sure that our stored procedure contains a single query, and therefore avoid any problems with multiple result sets. If we wanted, we could always use UNION ALL to make sure that we can return an appropriate error message. alter procedure dbo.GetMonthSummaryPerSalesPerson(@eomdate datetime) as begin     select SalesPersonID, count(*) as NumSales, sum(TotalDue) as TotalSales, /*Placeholder: */ '' as ErrorMessage     from Sales.SalesOrderHeader     where     /* Make sure that @eomdate is valid */         isdate(@eomdate) = 1     /* And that it's sufficiently past */     and datediff(day,@eomdate,sysdatetime()) >= 5     /* And now use it in the filter as appropriate */     and OrderDate >= dateadd(month,-1,@eomdate)     and OrderDate < @eomdate     group by SalesPersonID     /* Now include the error messages */     union all     select 0, 0, 0, 'Please enter a valid date' as ErrorMessage     where isdate(@eomdate) != 1     union all     select 0, 0, 0, 'Sorry - EOM is not complete yet' as ErrorMessage     where datediff(day,@eomdate,sysdatetime()) < 5     order by SalesPersonID; end But still I don’t like it, because it’s now a stored procedure with a single query. And I don’t like stored procedures that should be functions. That’s right – I think this should be a function, and SSRS should call the function. And I apologise to those of you who are now planning a bonfire for me. Guy Fawkes’ night has already passed this year, so I think you miss out. (And I’m not going to remind you about when the PASS Summit is in 2012.) create function dbo.GetMonthSummaryPerSalesPerson(@eomdate datetime) returns table as return (     select SalesPersonID, count(*) as NumSales, sum(TotalDue) as TotalSales, '' as ErrorMessage     from Sales.SalesOrderHeader     where     /* Make sure that @eomdate is valid */         isdate(@eomdate) = 1     /* And that it's sufficiently past */     and datediff(day,@eomdate,sysdatetime()) >= 5     /* And now use it in the filter as appropriate */     and OrderDate >= dateadd(month,-1,@eomdate)     and OrderDate < @eomdate     group by SalesPersonID     union all     select 0, 0, 0, 'Please enter a valid date' as ErrorMessage     where isdate(@eomdate) != 1     union all     select 0, 0, 0, 'Sorry - EOM is not complete yet' as ErrorMessage     where datediff(day,@eomdate,sysdatetime()) < 5 ); We’ve had to lose the ORDER BY – but that’s fine, as that’s a client thing anyway. We can have our reports leverage this stored query still, but we’re recognising that it’s a query, not a procedure. A procedure is designed to DO stuff, not just return data. We even get entries in sys.columns that confirm what the shape of the result set actually is, which makes sense, because a table-valued function is the right mechanism to return data. And we get so much more flexibility with this. If you haven’t seen the simplification stuff that I’ve preached on before, jump over to http://bit.ly/SimpleRob and watch the video of when I broke a microphone and nearly fell off the stage in Wales. You’ll see the impact of being able to have a simplifiable query. You can also read the procedural functions post I wrote recently, if you didn’t follow the link from a few paragraphs ago. So if we want the list of SalesPeople that made any kind of sales in a given month, we can do something like: select SalesPersonID from dbo.GetMonthSummaryPerSalesPerson(@eomonth) order by SalesPersonID; This doesn’t need to look up the TotalDue field, which makes a simpler plan. select * from dbo.GetMonthSummaryPerSalesPerson(@eomonth) where SalesPersonID is not null order by SalesPersonID; This one can avoid having to do the work on the rows that don’t have a SalesPersonID value, pushing the predicate into the Index Seek rather than filtering the results that come back to the report. If we had joins involved, we might see some of those being simplified out. We also get the ability to include query hints in individual reports. We shift from having a single-use stored procedure to having a reusable stored query – and isn’t that one of the main points of modularisation? Stored procedures in Reporting Services are just a bit limited for my liking. They’re useful in plenty of ways, but if you insist on using stored procedures all the time rather that queries that use functions – that’s rubbish. @rob_farley

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• Flow-Design Cheat Sheet &ndash; Part I, Notation

  - by Ralf Westphal

  You want to avoid the pitfalls of object oriented design? Then this is the right place to start. Use Flow-Oriented Analysis (FOA) and –Design (FOD or just FD for Flow-Design) to understand a problem domain and design a software solution. Flow-Orientation as described here is related to Flow-Based Programming, Event-Based Programming, Business Process Modelling, and even Event-Driven Architectures. But even though “thinking in flows” is not new, I found it helpful to deviate from those precursors for several reasons. Some aim at too big systems for the average programmer, some are concerned with only asynchronous processing, some are even not very much concerned with programming at all. What I was looking for was a design method to help in software projects of any size, be they large or tiny, involing synchronous or asynchronous processing, being local or distributed, running on the web or on the desktop or on a smartphone. That´s why I took ideas from all of the above sources and some additional and came up with Event-Based Components which later got repositioned and renamed to Flow-Design. In the meantime this has generated some discussion (in the German developer community) and several teams have started to work with Flow-Design. Also I´ve conducted quite some trainings using Flow-Orientation for design. The results are very promising. Developers find it much easier to design software using Flow-Orientation than OOAD-based object orientation. Since Flow-Orientation is moving fast and is not covered completely by a single source like a book, demand has increased for at least an overview of the current state of its notation. This page is trying to answer this demand by briefly introducing/describing every notational element as well as their translation into C# source code. Take this as a cheat sheet to put next to your whiteboard when designing software. However, please do not expect any explanation as to the reasons behind Flow-Design elements. Details on why Flow-Design at all and why in this specific way you´ll find in the literature covering the topic. Here´s a resource page on Flow-Design/Event-Based Components, if you´re able to read German. Notation Connected Functional Units The basic element of any FOD are functional units (FU): Think of FUs as some kind of software code block processing data. For the moment forget about classes, methods, “components”, assemblies or whatever. See a FU as an abstract piece of code. Software then consists of just collaborating FUs. I´m using circles/ellipses to draw FUs. But if you like, use rectangles. Whatever suites your whiteboard needs best.   The purpose of FUs is to process input and produce output. FUs are transformational. However, FUs are not called and do not call other FUs. There is no dependency between FUs. Data just flows into a FU (input) and out of it (output). From where and where to is of no concern to a FU.   This way FUs can be concatenated in arbitrary ways:   Each FU can accept input from many sources and produce output for many sinks:   Flows Connected FUs form a flow with a start and an end. Data is entering a flow at a source, and it´s leaving it through a sink. Think of sources and sinks as special FUs which conntect wires to the environment of a network of FUs.   Wiring Details Data is flowing into/out of FUs through wires. This is to allude to electrical engineering which since long has been working with composable parts. Wires are attached to FUs usings pins. They are the entry/exit points for the data flowing along the wires. Input-/output pins currently need not be drawn explicitly. This is to keep designing on a whiteboard simple and quick.   Data flowing is of some type, so wires have a type attached to them. And pins have names. If there is only one input pin and output pin on a FU, though, you don´t need to mention them. The default is Process for a single input pin, and Result for a single output pin. But you´re free to give even single pins different names.   There is a shortcut in use to address a certain pin on a destination FU:   The type of the wire is put in parantheses for two reasons. 1. This way a “no-type” wire can be easily denoted, 2. this is a natural way to describe tuples of data.   To describe how much data is flowing, a star can be put next to the wire type:   Nesting – Boards and Parts If more than 5 to 10 FUs need to be put in a flow a FD starts to become hard to understand. To keep diagrams clutter free they can be nested. You can turn any FU into a flow: This leads to Flow-Designs with different levels of abstraction. A in the above illustration is a high level functional unit, A.1 and A.2 are lower level functional units. One of the purposes of Flow-Design is to be able to describe systems on different levels of abstraction and thus make it easier to understand them. Humans use abstraction/decomposition to get a grip on complexity. Flow-Design strives to support this and make levels of abstraction first class citizens for programming. You can read the above illustration like this: Functional units A.1 and A.2 detail what A is supposed to do. The whole of A´s responsibility is decomposed into smaller responsibilities A.1 and A.2. FU A thus does not do anything itself anymore! All A is responsible for is actually accomplished by the collaboration between A.1 and A.2. Since A now is not doing anything anymore except containing A.1 and A.2 functional units are devided into two categories: boards and parts. Boards are just containing other functional units; their sole responsibility is to wire them up. A is a board. Boards thus depend on the functional units nested within them. This dependency is not of a functional nature, though. Boards are not dependent on services provided by nested functional units. They are just concerned with their interface to be able to plug them together. Parts are the workhorses of flows. They contain the real domain logic. They actually transform input into output. However, they do not depend on other functional units. Please note the usage of source and sink in boards. They correspond to input-pins and output-pins of the board.   Implicit Dependencies Nesting functional units leads to a dependency tree. Boards depend on nested functional units, they are the inner nodes of the tree. Parts are independent, they are the leafs: Even though dependencies are the bane of software development, Flow-Design does not usually draw these dependencies. They are implicitly created by visually nesting functional units. And they are harmless. Boards are so simple in their functionality, they are little affected by changes in functional units they are depending on. But functional units are implicitly dependent on more than nested functional units. They are also dependent on the data types of the wires attached to them: This is also natural and thus does not need to be made explicit. And it pertains mainly to parts being dependent. Since boards don´t do anything with regard to a problem domain, they don´t care much about data types. Their infrastructural purpose just needs types of input/output-pins to match.   Explicit Dependencies You could say, Flow-Orientation is about tackling complexity at its root cause: that´s dependencies. “Natural” dependencies are depicted naturally, i.e. implicitly. And whereever possible dependencies are not even created. Functional units don´t know their collaborators within a flow. This is core to Flow-Orientation. That makes for high composability of functional units. A part is as independent of other functional units as a motor is from the rest of the car. And a board is as dependend on nested functional units as a motor is on a spark plug or a crank shaft. With Flow-Design software development moves closer to how hardware is constructed. Implicit dependencies are not enough, though. Sometimes explicit dependencies make designs easier – as counterintuitive this might sound. So FD notation needs a ways to denote explicit dependencies: Data flows along wires. But data does not flow along dependency relations. Instead dependency relations represent service calls. Functional unit C is depending on/calling services on functional unit S. If you want to be more specific, name the services next to the dependency relation: Although you should try to stay clear of explicit dependencies, they are fundamentally ok. See them as a way to add another dimension to a flow. Usually the functionality of the independent FU (“Customer repository” above) is orthogonal to the domain of the flow it is referenced by. If you like emphasize this by using different shapes for dependent and independent FUs like above. Such dependencies can be used to link in resources like databases or shared in-memory state. FUs can not only produce output but also can have side effects. A common pattern for using such explizit dependencies is to hook a GUI into a flow as the source and/or the sink of data: Which can be shortened to: Treat FUs others depend on as boards (with a special non-FD API the dependent part is connected to), but do not embed them in a flow in the diagram they are depended upon.   Attributes of Functional Units Creation and usage of functional units can be modified with attributes. So far the following have shown to be helpful: Singleton: FUs are by default multitons. FUs in the same of different flows with the same name refer to the same functionality, but to different instances. Think of functional units as objects that get instanciated anew whereever they appear in a design. Sometimes though it´s helpful to reuse the same instance of a functional unit; this is always due to valuable state it holds. Signify this by annotating the FU with a “(S)”. Multiton: FUs on which others depend are singletons by default. This is, because they usually are introduced where shared state comes into play. If you want to change them to be a singletons mark them with a “(M)”. Configurable: Some parts need to be configured before the can do they work in a flow. Annotate them with a “(C)” to have them initialized before any data items to be processed by them arrive. Do not assume any order in which FUs are configured. How such configuration is happening is an implementation detail. Entry point: In each design there needs to be a single part where “it all starts”. That´s the entry point for all processing. It´s like Program.Main() in C# programs. Mark the entry point part with an “(E)”. Quite often this will be the GUI part. How the entry point is started is an implementation detail. Just consider it the first FU to start do its job.   Patterns / Standard Parts If more than a single wire is attached to an output-pin that´s called a split (or fork). The same data is flowing on all of the wires. Remember: Flow-Designs are synchronous by default. So a split does not mean data is processed in parallel afterwards. Processing still happens synchronously and thus one branch after another. Do not assume any specific order of the processing on the different branches after the split.   It is common to do a split and let only parts of the original data flow on through the branches. This effectively means a map is needed after a split. This map can be implicit or explicit.   Although FUs can have multiple input-pins it is preferrable in most cases to combine input data from different branches using an explicit join: The default output of a join is a tuple of its input values. The default behavior of a join is to output a value whenever a new input is received. However, to produce its first output a join needs an input for all its input-pins. Other join behaviors can be: reset all inputs after an output only produce output if data arrives on certain input-pins

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• 64-bit Archives Needed

  - by user9154181

  A little over a year ago, we received a question from someone who was trying to build software on Solaris. He was getting errors from the ar command when creating an archive. At that time, the ar command on Solaris was a 32-bit command. There was more than 2GB of data, and the ar command was hitting the file size limit for a 32-bit process that doesn't use the largefile APIs. Even in 2011, 2GB is a very large amount of code, so we had not heard this one before. Most of our toolchain was extended to handle 64-bit sized data back in the 1990's, but archives were not changed, presumably because there was no perceived need for it. Since then of course, programs have continued to get larger, and in 2010, the time had finally come to investigate the issue and find a way to provide for larger archives. As part of that process, I had to do a deep dive into the archive format, and also do some Unix archeology. I'm going to record what I learned here, to document what Solaris does, and in the hope that it might help someone else trying to solve the same problem for their platform. Archive Format Details Archives are hardly cutting edge technology. They are still used of course, but their basic form hasn't changed in decades. Other than to fix a bug, which is rare, we don't tend to touch that code much. The archive file format is described in /usr/include/ar.h, and I won't repeat the details here. Instead, here is a rough overview of the archive file format, implemented by System V Release 4 (SVR4) Unix systems such as Solaris: Every archive starts with a "magic number". This is a sequence of 8 characters: "!<arch>\n". The magic number is followed by 1 or more members. A member starts with a fixed header, defined by the ar_hdr structure in/usr/include/ar.h. Immediately following the header comes the data for the member. Members must be padded at the end with newline characters so that they have even length. The requirement to pad members to an even length is a dead giveaway as to the age of the archive format. It tells you that this format dates from the 1970's, and more specifically from the era of 16-bit systems such as the PDP-11 that Unix was originally developed on. A 32-bit system would have required 4 bytes, and 64-bit systems such as we use today would probably have required 8 bytes. 2 byte alignment is a poor choice for ELF object archive members. 32-bit objects require 4 byte alignment, and 64-bit objects require 64-bit alignment. The link-editor uses mmap() to process archives, and if the members have the wrong alignment, we have to slide (copy) them to the correct alignment before we can access the ELF data structures inside. The archive format requires 2 byte padding, but it doesn't prohibit more. The Solaris ar command takes advantage of this, and pads ELF object members to 8 byte boundaries. Anything else is padded to 2 as required by the format. The archive header (ar_hdr) represents all numeric values using an ASCII text representation rather than as binary integers. This means that an archive that contains only text members can be viewed using tools such as cat, more, or a text editor. The original designers of this format clearly thought that archives would be used for many file types, and not just for objects. Things didn't turn out that way of course — nearly all archives contain relocatable objects for a single operating system and machine, and are used primarily as input to the link-editor (ld). Archives can have special members that are created by the ar command rather than being supplied by the user. These special members are all distinguished by having a name that starts with the slash (/) character. This is an unambiguous marker that says that the user could not have supplied it. The reason for this is that regular archive members are given the plain name of the file that was inserted to create them, and any path components are stripped off. Slash is the delimiter character used by Unix to separate path components, and as such cannot occur within a plain file name. The ar command hides the special members from you when you list the contents of an archive, so most users don't know that they exist. There are only two possible special members: A symbol table that maps ELF symbols to the object archive member that provides it, and a string table used to hold member names that exceed 15 characters. The '/' convention for tagging special members provides room for adding more such members should the need arise. As I will discuss below, we took advantage of this fact to add an alternate 64-bit symbol table special member which is used in archives that are larger than 4GB. When an archive contains ELF object members, the ar command builds a special archive member known as the symbol table that maps all ELF symbols in the object to the archive member that provides it. The link-editor uses this symbol table to determine which symbols are provided by the objects in that archive. If an archive has a symbol table, it will always be the first member in the archive, immediately following the magic number. Unlike member headers, symbol tables do use binary integers to represent offsets. These integers are always stored in big-endian format, even on a little endian host such as x86. The archive header (ar_hdr) provides 15 characters for representing the member name. If any member has a name that is longer than this, then the real name is written into a special archive member called the string table, and the member's name field instead contains a slash (/) character followed by a decimal representation of the offset of the real name within the string table. The string table is required to precede all normal archive members, so it will be the second member if the archive contains a symbol table, and the first member otherwise. The archive format is not designed to make finding a given member easy. Such operations move through the archive from front to back examining each member in turn, and run in O(n) time. This would be bad if archives were commonly used in that manner, but in general, they are not. Typically, the ar command is used to build an new archive from scratch, inserting all the objects in one operation, and then the link-editor accesses the members in the archive in constant time by using the offsets provided by the symbol table. Both of these operations are reasonably efficient. However, listing the contents of a large archive with the ar command can be rather slow. Factors That Limit Solaris Archive Size As is often the case, there was more than one limiting factor preventing Solaris archives from growing beyond the 32-bit limits of 2GB (32-bit signed) and 4GB (32-bit unsigned). These limits are listed in the order they are hit as archive size grows, so the earlier ones mask those that follow. The original Solaris archive file format can handle sizes up to 4GB without issue. However, the ar command was delivered as a 32-bit executable that did not use the largefile APIs. As such, the ar command itself could not create a file larger than 2GB. One can solve this by building ar with the largefile APIs which would allow it to reach 4GB, but a simpler and better answer is to deliver a 64-bit ar, which has the ability to scale well past 4GB. Symbol table offsets are stored as 32-bit big-endian binary integers, which limits the maximum archive size to 4GB. To get around this limit requires a different symbol table format, or an extension mechanism to the current one, similar in nature to the way member names longer than 15 characters are handled in member headers. The size field in the archive member header (ar_hdr) is an ASCII string capable of representing a 32-bit unsigned value. This places a 4GB size limit on the size of any individual member in an archive. In considering format extensions to get past these limits, it is important to remember that very few archives will require the ability to scale past 4GB for many years. The old format, while no beauty, continues to be sufficient for its purpose. This argues for a backward compatible fix that allows newer versions of Solaris to produce archives that are compatible with older versions of the system unless the size of the archive exceeds 4GB. Archive Format Differences Among Unix Variants While considering how to extend Solaris archives to scale to 64-bits, I wanted to know how similar archives from other Unix systems are to those produced by Solaris, and whether they had already solved the 64-bit issue. I've successfully moved archives between different Unix systems before with good luck, so I knew that there was some commonality. If it turned out that there was already a viable defacto standard for 64-bit archives, it would obviously be better to adopt that rather than invent something new. The archive file format is not formally standardized. However, the ar command and archive format were part of the original Unix from Bell Labs. Other systems started with that format, extending it in various often incompatible ways, but usually with the same common shared core. Most of these systems use the same magic number to identify their archives, despite the fact that their archives are not always fully compatible with each other. It is often true that archives can be copied between different Unix variants, and if the member names are short enough, the ar command from one system can often read archives produced on another. In practice, it is rare to find an archive containing anything other than objects for a single operating system and machine type. Such an archive is only of use on the type of system that created it, and is only used on that system. This is probably why cross platform compatibility of archives between Unix variants has never been an issue. Otherwise, the use of the same magic number in archives with incompatible formats would be a problem. I was able to find information for a number of Unix variants, described below. These can be divided roughly into three tribes, SVR4 Unix, BSD Unix, and IBM AIX. Solaris is a SVR4 Unix, and its archives are completely compatible with those from the other members of that group (GNU/Linux, HP-UX, and SGI IRIX). AIX AIX is an exception to rule that Unix archive formats are all based on the original Bell labs Unix format. It appears that AIX supports 2 formats (small and big), both of which differ in fundamental ways from other Unix systems: These formats use a different magic number than the standard one used by Solaris and other Unix variants. They include support for removing archive members from a file without reallocating the file, marking dead areas as unused, and reusing them when new archive items are inserted. They have a special table of contents member (File Member Header) which lets you find out everything that's in the archive without having to actually traverse the entire file. Their symbol table members are quite similar to those from other systems though. Their member headers are doubly linked, containing offsets to both the previous and next members. Of the Unix systems described here, AIX has the only format I saw that will have reasonable insert/delete performance for really large archives. Everyone else has O(n) performance, and are going to be slow to use with large archives. BSD BSD has gone through 4 versions of archive format, which are described in their manpage. They use the same member header as SVR4, but their symbol table format is different, and their scheme for long member names puts the name directly after the member header rather than into a string table. GNU/Linux The GNU toolchain uses the SVR4 format, and is compatible with Solaris. HP-UX HP-UX seems to follow the SVR4 model, and is compatible with Solaris. IRIX IRIX has 32 and 64-bit archives. The 32-bit format is the standard SVR4 format, and is compatible with Solaris. The 64-bit format is the same, except that the symbol table uses 64-bit integers. IRIX assumes that an archive contains objects of a single ELFCLASS/MACHINE, and any archive containing ELFCLASS64 objects receives a 64-bit symbol table. Although they only use it for 64-bit objects, nothing in the archive format limits it to ELFCLASS64. It would be perfectly valid to produce a 64-bit symbol table in an archive containing 32-bit objects, text files, or anything else. Tru64 Unix (Digital/Compaq/HP) Tru64 Unix uses a format much like ours, but their symbol table is a hash table, making specific symbol lookup much faster. The Solaris link-editor uses archives by examining the entire symbol table looking for unsatisfied symbols for the link, and not by looking up individual symbols, so there would be no benefit to Solaris from such a hash table. The Tru64 ld must use a different approach in which the hash table pays off for them. Widening the existing SVR4 archive symbol tables rather than inventing something new is the simplest path forward. There is ample precedent for this approach in the ELF world. When ELF was extended to support 64-bit objects, the approach was largely to take the existing data structures, and define 64-bit versions of them. We called the old set ELF32, and the new set ELF64. My guess is that there was no need to widen the archive format at that time, but had there been, it seems obvious that this is how it would have been done. The Implementation of 64-bit Solaris Archives As mentioned earlier, there was no desire to improve the fundamental nature of archives. They have always had O(n) insert/delete behavior, and for the most part it hasn't mattered. AIX made efforts to improve this, but those efforts did not find widespread adoption. For the purposes of link-editing, which is essentially the only thing that archives are used for, the existing format is adequate, and issues of backward compatibility trump the desire to do something technically better. Widening the existing symbol table format to 64-bits is therefore the obvious way to proceed. For Solaris 11, I implemented that, and I also updated the ar command so that a 64-bit version is run by default. This eliminates the 2 most significant limits to archive size, leaving only the limit on an individual archive member. We only generate a 64-bit symbol table if the archive exceeds 4GB, or when the new -S option to the ar command is used. This maximizes backward compatibility, as an archive produced by Solaris 11 is highly likely to be less than 4GB in size, and will therefore employ the same format understood by older versions of the system. The main reason for the existence of the -S option is to allow us to test the 64-bit format without having to construct huge archives to do so. I don't believe it will find much use outside of that. Other than the new ability to create and use extremely large archives, this change is largely invisible to the end user. When reading an archive, the ar command will transparently accept either form of symbol table. Similarly, the ELF library (libelf) has been updated to understand either format. Users of libelf (such as the link-editor ld) do not need to be modified to use the new format, because these changes are encapsulated behind the existing functions provided by libelf. As mentioned above, this work did not lift the limit on the maximum size of an individual archive member. That limit remains fixed at 4GB for now. This is not because we think objects will never get that large, for the history of computing says otherwise. Rather, this is based on an estimation that single relocatable objects of that size will not appear for a decade or two. A lot can change in that time, and it is better not to overengineer things by writing code that will sit and rot for years without being used. It is not too soon however to have a plan for that eventuality. When the time comes when this limit needs to be lifted, I believe that there is a simple solution that is consistent with the existing format. The archive member header size field is an ASCII string, like the name, and as such, the overflow scheme used for long names can also be used to handle the size. The size string would be placed into the archive string table, and its offset in the string table would then be written into the archive header size field using the same format "/ddd" used for overflowed names.

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• Mysql Slave stuck in "System lock"

  - by Greg

  My MySQL slave is spending a lot of time in Slave_SQL_Running_State: System lock. I can see that the system is currently I/O write bound, and that it is processing the log, although slowly. Show processlist doesn't show anything other than "Waiting for master to send event" and "System lock" when it is in this state. All my tables (other than the system tables) are InnoDB, and external locking is disabled. What is the slave doing in this state?

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• how to install mono xsp4 and fastcgi-mono-server4

  - by james lewis

  Quick question - I'm on Debian squeeze, running nginx fine and installed mono fine. Now I want to host a .net4 web application and as I understand it I'll need fastcgi-mono-server4 (and xsp4 when testing it out) - where do I get these packages? I tried apt-get install fastcgi-mono-server4 and same for mono-xsp4-base. When I did apt-get searchpkg mono I couldn't see anything relating to xsp4 or fastcgi server4. Any ideas what I'm doing wrong? (sorry for the rushed question) Regards, James

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