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• Is False == 0 and True == 1 in Python an implementation detail or guaranteed by the language?

  - by EOL

  Is it guaranteed that False == 0 and True == 1, in Python? For instance, is it in any way guaranteed that the following code will always produce the same results, whatever the version of Python (existing and in the foreseeable future)? 0 == False # True 1 == True # True ['zero', 'one'][False] # is 'zero' Any reference to the official documentation would be much appreciated! Other comments would be appreciated too… :) Edit: As noted in many answers, bool inherits from int. The question can therefore be recast as: "Is this an implementation detail that might change in the future, or does the documentation officially say that programmers can rely on booleans inheriting from integers?". This question is relevant for writing robust code that won't fail because of implementation details! Edit 2: The original question is still open, I believe (even though I accepted what I thought was the closest answer): even though Python 3 officially recognizes booleans as integers, I have not yet seen any official integer values for False and True… It therefore looks to me like it is best to stay clear from the assumption that False==0 and True==1.

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• Setting the type of a field in a superclass from a subclass (Java)

  - by Ibolit

  Hi. I am writing a project on Google App Engine, within it I have a number of abstract classes that I hope I will be able to use in my future projects, and a number of concrete classes inheriting from them. Among other abstract classes I have an abstract servlet that does user management, and I hava an abstract user. The AbstractUser has all the necessary fields and methods for storing it in the datastore and telling whether the user is registered with my service or not. It does not implement any project specific functionality. The abstract servlet that manages users, refers only to the methods declared in the AbstractUser class, which allows it to generate links for logging in, logging out and registering (for unregistered users). In order to implement the project-specific user functionality I need to subclass the Abstract user. The servlets I use in my project are all indirect descendants from that abstract user management servlet, and the user is a protected field in it, so the descendant servlets can use it as their own field. However, whenever i want to access any project specific method of the concrete user, i need to cast it to that type. i.e. (abstract user managing servlet) ... AbstractUser user = getUser(); ... abstract protected AbstractUser getUser(); (project-specific abstract servlet) @Override protected AbstractUser getUser() { return MyUserFactory.getUser(); } any other project specific servlet: int a = ((ConcreteUser) user).getA(); Well, what i'd like to do is to somehow make the type of “user” in the superclass depend on something in the project-specific abstract class. Is it at all possible? And i don't want to move all the user-management stuff into a project-specific layer, for i would like to have it for my future projects already written :) Thank you for your help.

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• Built in background-scheduling system in .NET?

  - by Lasse V. Karlsen

  I ask though I doubt there is any such system. Basically I need to schedule tasks to execute at some point in the future (usually no more than a few seconds or possibly minutes from now), and have some way of cancelling that request unless too late. Ie. code that would look like this: var x = Scheduler.Schedule(() => SomethingSomething(), TimeSpan.FromSeconds(5)); ... x.Dispose(); // cancels the request Is there any such system in .NET? Is there anything in TPL that can help me? I need to run such future-actions from various instances in a system here, and would rather avoid each such class instance to have its own thread and deal with this. Also note that I don't want this (or similar, for instance through Tasks): new Thread(new ThreadStart(() => { Thread.Sleep(5000); SomethingSomething(); })).Start(); There will potentially be a few such tasks to execute, they don't need to be executed in any particular order, except for close to their deadline, and it isn't vital that they have anything like a realtime performance concept. I just want to avoid spinning up a separate thread for each such action.

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• 10 Essential Tools for building ASP.NET Websites

  - by Stephen Walther

  I recently put together a simple public website created with ASP.NET for my company at Superexpert.com. I was surprised by the number of free tools that I ended up using to put together the website. Therefore, I thought it would be interesting to create a list of essential tools for building ASP.NET websites. These tools work equally well with both ASP.NET Web Forms and ASP.NET MVC. Performance Tools After reading Steve Souders two (very excellent) books on front-end website performance High Performance Web Sites and Even Faster Web Sites, I have been super sensitive to front-end website performance. According to Souders’ Performance Golden Rule: “Optimize front-end performance first, that's where 80% or more of the end-user response time is spent” You can use the tools below to reduce the size of the images, JavaScript files, and CSS files used by an ASP.NET application. 1. Sprite and Image Optimization Framework CSS sprites were first described in an article written for A List Apart entitled CSS sprites: Image Slicing’s Kiss of Death. When you use sprites, you combine multiple images used by a website into a single image. Next, you use CSS trickery to display particular sub-images from the combined image in a webpage. The primary advantage of sprites is that they reduce the number of requests required to display a webpage. Requesting a single large image is faster than requesting multiple small images. In general, the more resources – images, JavaScript files, CSS files – that must be moved across the wire, the slower your website. However, most people avoid using sprites because they require a lot of work. You need to combine all of the images and write just the right CSS rules to display the sub-images. The Microsoft Sprite and Image Optimization Framework enables you to avoid all of this work. The framework combines the images for you automatically. Furthermore, the framework includes an ASP.NET Web Forms control and an ASP.NET MVC helper that makes it easy to display the sub-images. You can download the Sprite and Image Optimization Framework from CodePlex at http://aspnet.codeplex.com/releases/view/50869. The Sprite and Image Optimization Framework was written by Morgan McClean who worked in the office next to mine at Microsoft. Morgan was a scary smart Intern from Canada and we discussed the Framework while he was building it (I was really excited to learn that he was working on it). Morgan added some great advanced features to this framework. For example, the Sprite and Image Optimization Framework supports something called image inlining. When you use image inlining, the actual image is stored in the CSS file. Here’s an example of what image inlining looks like: .Home_StephenWalther_small-jpg { width:75px; height:100px; background: url(data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAEsAAABkCAIAAABB1lpeAAAAB GdBTUEAALGOfPtRkwAAACBjSFJNAACHDwAAjA8AAP1SAACBQAAAfXkAAOmLAAA85QAAGcxzPIV3AAAKL s+zNfREAAAAASUVORK5CYII=) no-repeat 0% 0%; } The actual image (in this case a picture of me that is displayed on the home page of the Superexpert.com website) is stored in the CSS file. If you visit the Superexpert.com website then very few separate images are downloaded. For example, all of the images with a red border in the screenshot below take advantage of CSS sprites: Unfortunately, there are some significant Gotchas that you need to be aware of when using the Sprite and Image Optimization Framework. There are workarounds for these Gotchas. I plan to write about these Gotchas and workarounds in a future blog entry. 2. Microsoft Ajax Minifier Whenever possible you should combine, minify, compress, and cache with a far future header all of your JavaScript and CSS files. The Microsoft Ajax Minifier makes it easy to minify JavaScript and CSS files. Don’t confuse minification and compression. You need to do both. According to Souders, you can reduce the size of a JavaScript file by an additional 20% (on average) by minifying a JavaScript file after you compress the file. When you minify a JavaScript or CSS file, you use various tricks to reduce the size of the file before you compress the file. For example, you can minify a JavaScript file by replacing long JavaScript variables names with short variables names and removing unnecessary white space and comments. You can minify a CSS file by doing such things as replacing long color names such as #ffffff with shorter equivalents such as #fff. The Microsoft Ajax Minifier was created by Microsoft employee Ron Logan. Internally, this tool was being used by several large Microsoft websites. We also used the tool heavily on the ASP.NET team. I convinced Ron to publish the tool on CodePlex so that everyone in the world could take advantage of it. You can download the tool from the ASP.NET Ajax website and read documentation for the tool here. I created the installer for the Microsoft Ajax Minifier. When creating the installer, I also created a Visual Studio build task to make it easy to minify all of your JavaScript and CSS files whenever you do a build within Visual Studio automatically. Read the Ajax Minifier Quick Start to learn how to configure the build task. 3. ySlow The ySlow tool is a free add-on for Firefox created by Yahoo that enables you to test the front-end of your website. For example, here are the current test results for the Superexpert.com website: The Superexpert.com website has an overall score of B (not perfect but not bad). The ySlow tool is not perfect. For example, the Superexpert.com website received a failing grade of F for not using a Content Delivery Network even though the website using the Microsoft Ajax Content Delivery Network for JavaScript files such as jQuery. Uptime After publishing a website live to the world, you want to ensure that the website does not encounter any issues and that it stays live. I use the following tools to monitor the Superexpert.com website now that it is live. 4. ELMAH ELMAH stands for Error Logging Modules and Handlers for ASP.NET. ELMAH enables you to record any errors that happen at your website so you can review them in the future. You can download ELMAH for free from the ELMAH project website. ELMAH works great with both ASP.NET Web Forms and ASP.NET MVC. You can configure ELMAH to store errors in a number of different stores including XML files, the Event Log, an Access database, a SQL database, an Oracle database, or in computer RAM. You also can configure ELMAH to email error messages to you when they happen. By default, you can access ELMAH by requesting the elmah.axd page from a website with ELMAH installed. Here’s what the elmah page looks like from the Superexpert.com website (this page is password-protected because secret information can be revealed in an error message): If you click on a particular error message, you can view the original Yellow Screen ASP.NET error message (even when the error message was never displayed to the actual user). I installed ELMAH by taking advantage of the new package manager for ASP.NET named NuGet (originally named NuPack). You can read the details about NuGet in the following blog entry by Scott Guthrie. You can download NuGet from CodePlex. 5. Pingdom I use Pingdom to verify that the Superexpert.com website is always up. You can sign up for Pingdom by visiting Pingdom.com. You can use Pingdom to monitor a single website for free. At the Pingdom website, you configure the frequency that your website gets pinged. I verify that the Superexpert.com website is up every 5 minutes. I have the Pingdom service verify that it can retrieve the string “Contact Us” from the website homepage. If your website goes down, you can configure Pingdom so that it sends an email, Twitter, SMS, or iPhone alert. I use the Pingdom iPhone app which looks like this: 6. Host Tracker If your website does go down then you need some way of determining whether it is a problem with your local network or if your website is down for everyone. I use a website named Host-Tracker.com to check how badly a website is down. Here’s what the Host-Tracker website displays for the Superexpert.com website when the website can be successfully pinged from everywhere in the world: Notice that Host-Tracker pinged the Superexpert.com website from 68 locations including Roubaix, France and Scranton, PA. Debugging I mean debugging in the broadest possible sense. I use the following tools when building a website to verify that I have not made a mistake. 7. HTML Spell Checker Why doesn’t Visual Studio have a built-in spell checker? Don’t know – I’ve always found this mysterious. Fortunately, however, a former member of the ASP.NET team wrote a free spell checker that you can use with your ASP.NET pages. I find a spell checker indispensible. It is easy to delude yourself that you are capable of perfect spelling. I’m always super embarrassed when I actually run the spell checking tool and discover all of my spelling mistakes. The fastest way to add the HTML Spell Checker extension to Visual Studio is to select the menu option Tools, Extension Manager within Visual Studio. Click on Online Gallery and search for HTML Spell Checker: 8. IIS SEO Toolkit If people cannot find your website through Google then you should not even bother to create it. Microsoft has a great extension for IIS named the IIS Search Engine Optimization Toolkit that you can use to identify issue with your website that would hurt its page rank. You also can use this tool to quickly create a sitemap for your website that you can submit to Google or Bing. You can even generate the sitemap for an ASP.NET MVC website. Here’s what the report overview for the Superexpert.com website looks like: Notice that the Sueprexpert.com website had plenty of violations. For example, there are 65 cases in which a page has a broken hyperlink. You can drill into these violations to identity the exact page and location where these violations occur. 9. LinqPad If your ASP.NET website accesses a database then you should be using LINQ to Entities with the Entity Framework. Using LINQ involves some magic. LINQ queries written in C# get converted into SQL queries for you. If you are not careful about how you write your LINQ queries, you could unintentionally build a really badly performing website. LinqPad is a free tool that enables you to experiment with your LINQ queries. It even works with Microsoft SQL CE 4 and Azure. You can use LinqPad to execute a LINQ to Entities query and see the results. You also can use it to see the resulting SQL that gets executed against the database: 10. .NET Reflector I use .NET Reflector daily. The .NET Reflector tool enables you to take any assembly and disassemble the assembly into C# or VB.NET code. You can use .NET Reflector to see the “Source Code” of an assembly even when you do not have the actual source code. You can download a free version of .NET Reflector from the Redgate website. I use .NET Reflector primarily to help me understand what code is doing internally. For example, I used .NET Reflector with the Sprite and Image Optimization Framework to better understand how the MVC Image helper works. Here’s part of the disassembled code from the Image helper class: Summary In this blog entry, I’ve discussed several of the tools that I used to create the Superexpert.com website. These are tools that I use to improve the performance, improve the SEO, verify the uptime, or debug the Superexpert.com website. All of the tools discussed in this blog entry are free. Furthermore, all of these tools work with both ASP.NET Web Forms and ASP.NET MVC. Let me know if there are any tools that you use daily when building ASP.NET websites.

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• MSCC: Global Windows Azure Bootcamp

  Mauritius participated and contributed to the Global Windows Azure Bootcamp 2014 (GWAB). Again! And this time stronger than ever, and together with 137 other locations in 56 countries world-wide. We had 62 named registrations, 7 guest additions and approximately 10 offline participants prior to the event day. Most interestingly the organisation of the GWAB through the MSCC helped to increased the number of craftsmen. The Mauritius Software Craftsmanship Community has currently 138 registered members - in less than one year! Only with those numbers we can proudly say that all the preparations and hard work towards this event already paid off. Personally, I'm really grateful that we had this kind of response and the feedback from some attendees confirmed that the MSCC is on the right track here on Cyber Island Mauritius. Inspired and motivated by the success of this event, rest assured that there will be more public events like the GWAB. This time it took some time to reflect on our meetup, following my first impression right on spot: "Wow, what an experience to organise and participate in this global event. Overall, I've been very pleased with the preparations and the event itself. Surely, there have been some nicks that we have to address and to improve for future activities like this. Quite frankly, we are not professional event organisers (not yet) but we learned a lot over the past couple of days. A big Thank You to our event sponsors, namely Microsoft Indian Ocean Islands & French Pacific, Ceridian Mauritius and Emtel. Without them this event wouldn't have happened - Thank You! And to the cool team members of Microsoft Student Partners (MSPs). You geeks did a great job! Thanks!" So, how many attendees did we actually have? 61! - Awesome - 61 cloud computing instances to help on the research of diabetes. During Saturday afternoon there was even an online publication on L'Express: Les développeurs mauriciens se joignent au combat contre le diabète Reactions of other attendees Don't take my word for granted... Here are some impressions and feedback from our participants: "Awesome event, really appreciated the presentations :-)" -- Kevin on event comments "very interesting and enriching." -- Diana on event comments "#gwab #gwabmru 2014 great success. Looking forward for gwab 2015" -- Wasiim on Twitter "Was there till the end. Awesome Event. I'll surely join upcoming meetup sessions :)" -- Luchmun on event comments "#gwabmru was not that cool. left early" -- Mohammad on Twitter The overall feedback is positive but we are absolutely aware that there quite a number of problems we had to face. We are already looking into that and ideas / action plans on how we will be able to improve it for future events. The sessions We started the day with welcoming speeches by Thierry Coret, Sr. Marketing Manager of Microsoft Indian Ocean Islands & French Pacific and Vidia Mooneegan, Managing Director and Sr. Vice President of Ceridian Mauritius. The clear emphasis was on the endless possibilities of cloud computing and how it can enable any kind of sectors here in the country. Then it was about time to set up the cloud computing services in order to contribute each attendees cloud computing resources to the global research of diabetes, a step by step guide presented by Arnaud Meslier, Technical Evangelist at Microsoft. Given a rendering package and a configuration file it was very interesting to follow the single steps in Windows Azure. Also, during the day we were not sure whether the set up had been correctly, as Mauritius didn't show up on the results board - which should have been the case after approximately 20 to 30 minutes. Anyways, let the minions work... Next, Arnaud gave a brief overview of the variety of services Windows Azure has to offer. Whether you need a development environment for your websites or mobiles app, running a virtual machine with your existing applications or simply putting a SQL database online. No worries, Windows Azure has the right packages available and the online management portal is really easy t handle. After this, we got a little bit more business oriented while Wasiim Hosenbocus, employee at Ceridian, took the attendees through the inerts of a real-life application, and demoed a couple of the existing features. He did a great job by showing how the different services of Windows Azure can be created and pulled together. After the lunch break it is always tough to keep the audience awake... And it was my turn. I gave a brief overview on operating and managing a SQL database on Windows Azure. Well, there are actually two options available and depending on your individual requirements you should be aware of both. The simpler version is called SQL Database and while provisioning only takes a couple of seconds, you should take into consideration that SQL Database has a number of constraints, like limitations on the actual database size - up to 5 GB as web edition and up to 150 GB maximum as business edition -, among others. Next, it was Chervine Bhiwoo's session on Windows Azure Mobile Services. It was absolutely amazing to see that the mobiles services directly offers you various project templates, like Windows 8 Store App, Android app, iOS app, and even Xamarin cross-platform app development. So, within a couple of minutes you can have your first mobile app active and running on Windows Azure. Furthermore, Chervine showed the attendees that adding another user interface, like Web Sites running on ASP.NET MVC 4 only takes a couple of minutes, too. And last but not least, we rounded up the day with Windows Azure Websites and hosting of Virtual Machines presented by some members of the local Microsoft Students Partners programme. Surely, one of the big advantages using Windows Azure is the availability of pre-defined installation packages of known web applications, like WordPress, Joomla!, or Ghost. Compared to running your own web site with a traditional web hoster it is surely en par, and depending on your personal level of expertise, Windows Azure provides you more liberty in terms of configuration than maybe a shared hosting environment. Running a pre-defined web application is one thing but in case that you would like to have more control over your hosting environment it is highly advised to opt for a virtual machine. Provisioning of an Ubuntu 12.04 LTS system was very simple to do but it takes some more minutes than you might expect. So, please be patient and take your time while Windows Azure gets everything in place for you. Afterwards, you can use a SecureShell (ssh) client like Putty in case of a Linux-based machine, or Remote Desktop Services when operating a Windows Server system to log in into your virtual machine. At the end of the day we had a great Q&A session and we finalised the event with our raffle of goodies. Participation in the raffle was bound to submission of the session survey and most gratefully we had a give-away for everyone. What a nice coincidence to finish of the day. Note: All session slides (and demo codes) will be made available on the MSCC event page. Please, check the Files section over there. (Some) Visual impressions from the event Just to give you an idea about what has happened during the GWAB 2014 at Ebene... Speakers and Microsoft Student Partners are getting ready for the Global Windows Azure Bootcamp 2014 GWAB 2014 attendees are fully integrated into the hands-on-labs and setting up their individuals cloud computing services 60 attendees at the GWAB 2014. Despite some technical difficulties we had a great time running the event GWAB 2014: Using the lunch break for networking and exchange of ideas - Great conversations and topics amongst attendees There are more pictures on the original event page: Questions & Answers Following are a couple of questions which have been asked and didn't get an answer during the event: Q: Is it possible to upload static pages via FTP? A: Yes, you can. Have a look at the right side column on the dashboard of your website. There you'll find information about the FTP and SFTP host names. You can use any FTP client, like ie. FileZilla to log in. FTP also gives you access to your log files. Q: What are the size limitations on SQL Database? A: 5 GB on the Web Edition, and 150 GB on the business edition. A maximum 150 databases (inclusing 'master') per SQL Database server. More details here: General Guidelines and Limitations (Azure SQL Database) Q: What's the maximum size of a SQL Server running in a Virtual Machine? A: The maximum Windows Azure VM has currently 8 CPU cores, 14 or 56 GB of RAM and 16x 1 TB hard drives. More details here: Virtual Machine and Cloud Service Sizes for Azure Q: How can we register for Windows Azure? A: Mauritius is currently not listed for phone verification. Please get in touch with Arnaud Meslier at Microsoft IOI & FP Q: Can I use my own domain name for Windows Azure websites? A: Yes, you can. But this might require to upscale your account to Standard. In case that I missed a question and answer, please use the comment section at the end of the article. Thanks! Final results Every participant was instructed during the hands-on-lab session on how to set up a cloud computing service in their account. Of course, I won't keep the results from you... Global Azure Lab GWAB 2014: Our cloud computing contribution to the research of diabetes And I would say Mauritius did a good job! Upcoming Events What are the upcoming events here in Mauritius? So far, we have the following ones (incomplete list as usual) in chronological order: Launch of Microsoft SQL Server 2014 (15.4.2014) Corsair Hackers Reboot (19.4.2014) WebCup (TBA ~ June 2014) Developers Conference (TBA ~ July 2014) Linuxfest 2014 (TBA ~ November 2014) Hopefully, there will be more announcements during the next couple of weeks and months. If you know about any other event, like a bootcamp, a code challenge or hackathon here in Mauritius, please drop me a note in the comment section below this article. Thanks! Networking and job/project opportunities Despite having technical presentations on Windows Azure an event like this always offers a great bunch of possibilities and opportunities to get in touch with new people in IT, have an exchange of experience with other like-minded people. As I already wrote about Communities - The importance of exchange and discussion - I had a great conversation with representatives of the University des Mascareignes which are currently embracing cloud infrastructure and cloud computing for their various campuses in the Indian Ocean. As for the MSCC it would be a great experience to stay in touch with them, and to work on upcoming, common activities. Furthermore, I had a very good conversation with Thierry and Ludovic of Microsoft IOI & FP on the necessity of user groups and IT communities here on the island. It's great to see that the MSCC is currently on a run and that local companies are sharing our thoughts on promoting IT careers and exchange of IT knowledge in such an open way. I'm also looking forward to be able to participate and to contribute on more events in the near future. My resume of the day We learned a lot today and there is always room for improvement! It was an awesome event and quite frankly it was a pleasure to spend the day with so many enthuastic IT people in the same room. It was a great experience to organise such event locally and participate on a global scale to support the GlyQ-IQ Technology in their research on diabetes. I was so pleased to see the involvement of new MSCC members in taking the opportunity to share and learn about the power of cloud computing. The Mauritius Software Craftsmanship Community is on the right way and this year's bootcamp on Windows Azure only marked the beginning of our journey. Thank you to our sponsors and my kudos to the MSPs! Update: Media coverage The event has been reported in local media, too. Following are some resources: Orange - Local - Business: Le cloud, pour des recherches approfondies sur le diabète Maurice Info.mu: Le cloud, pour des recherches approfondies sur le diabète Le Quotidien Pg 2: Global Windows Azure Bootcamp 2014 - Le cloud pour des recherches approfondies sur le diabète The Observer Pg 12: Le cloud, pour des recherches approfondies sur le diabète

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• 12c - flashforward, flashback or see it as of now...

  - by noreply(at)blogger.com (Thomas Kyte)

  Oracle 9i exposed flashback query to developers for the first time.  The ability to flashback query dates back to version 4 however (it just wasn't exposed).  Every time you run a query in Oracle it is in fact a flashback query - it is what multi-versioning is all about.However, there was never a flashforward query (well, ok, the workspace manager has this capability - but with lots of extra baggage).  We've never been able to ask a table "what will you look like tomorrow" - but now we do.The capability is called Temporal Validity.  If you have a table with data that is effective dated - has a "start date" and "end date" column in it - we can now query it using flashback query like syntax.  The twist is - the date we "flashback" to can be in the future.  It works by rewriting the query to transparently the necessary where clause and filter out the right rows for the right period of time - and since you can have records whose start date is in the future - you can query a table and see what it would look like at some future time.Here is a quick example, we'll start with a table:ops$tkyte%ORA12CR1> create table addresses  2  ( empno       number,  3    addr_data   varchar2(30),  4    start_date  date,  5    end_date    date,  6    period for valid(start_date,end_date)  7  )  8  /Table created.the new bit is on line 6 (it can be altered into an existing table - so any table  you have with a start/end date column will be a candidate).  The keyword is PERIOD, valid is an identifier I chose - it could have been foobar, valid just sounds nice in the query later.  You identify the columns in your table - or we can create them for you if they don't exist.  Then you just create some data:ops$tkyte%ORA12CR1> insert into addresses (empno, addr_data, start_date, end_date )  2  values ( 1234, '123 Main Street', trunc(sysdate-5), trunc(sysdate-2) );1 row created.ops$tkyte%ORA12CR1>ops$tkyte%ORA12CR1> insert into addresses (empno, addr_data, start_date, end_date )  2  values ( 1234, '456 Fleet Street', trunc(sysdate-1), trunc(sysdate+1) );1 row created.ops$tkyte%ORA12CR1>ops$tkyte%ORA12CR1> insert into addresses (empno, addr_data, start_date, end_date )  2  values ( 1234, '789 1st Ave', trunc(sysdate+2), null );1 row created.and you can either see all of the data:ops$tkyte%ORA12CR1> select * from addresses;     EMPNO ADDR_DATA                      START_DAT END_DATE---------- ------------------------------ --------- ---------      1234 123 Main Street                27-JUN-13 30-JUN-13      1234 456 Fleet Street               01-JUL-13 03-JUL-13      1234 789 1st Ave                    04-JUL-13or query "as of" some point in time - as  you can see in the predicate section - it is just doing a query rewrite to automate the "where" filters:ops$tkyte%ORA12CR1> select * from addresses as of period for valid sysdate-3;     EMPNO ADDR_DATA                      START_DAT END_DATE---------- ------------------------------ --------- ---------      1234 123 Main Street                27-JUN-13 30-JUN-13ops$tkyte%ORA12CR1> @planops$tkyte%ORA12CR1> select * from table(dbms_xplan.display_cursor);PLAN_TABLE_OUTPUT-------------------------------------------------------------------------------SQL_ID  cthtvvm0dxvva, child number 0-------------------------------------select * from addresses as of period for valid sysdate-3Plan hash value: 3184888728-------------------------------------------------------------------------------| Id  | Operation         | Name      | Rows  | Bytes | Cost (%CPU)| Time     |-------------------------------------------------------------------------------|   0 | SELECT STATEMENT  |           |       |       |     3 (100)|          ||*  1 |  TABLE ACCESS FULL| ADDRESSES |     1 |    48 |     3   (0)| 00:00:01 |-------------------------------------------------------------------------------Predicate Information (identified by operation id):---------------------------------------------------   1 - filter((("T"."START_DATE" IS NULL OR              "T"."START_DATE"<=SYSDATE@!-3) AND ("T"."END_DATE" IS NULL OR              "T"."END_DATE">SYSDATE@!-3)))Note-----   - dynamic statistics used: dynamic sampling (level=2)24 rows selected.ops$tkyte%ORA12CR1> select * from addresses as of period for valid sysdate;     EMPNO ADDR_DATA                      START_DAT END_DATE---------- ------------------------------ --------- ---------      1234 456 Fleet Street               01-JUL-13 03-JUL-13ops$tkyte%ORA12CR1> @planops$tkyte%ORA12CR1> select * from table(dbms_xplan.display_cursor);PLAN_TABLE_OUTPUT-------------------------------------------------------------------------------SQL_ID  26ubyhw9hgk7z, child number 0-------------------------------------select * from addresses as of period for valid sysdatePlan hash value: 3184888728-------------------------------------------------------------------------------| Id  | Operation         | Name      | Rows  | Bytes | Cost (%CPU)| Time     |-------------------------------------------------------------------------------|   0 | SELECT STATEMENT  |           |       |       |     3 (100)|          ||*  1 |  TABLE ACCESS FULL| ADDRESSES |     1 |    48 |     3   (0)| 00:00:01 |-------------------------------------------------------------------------------Predicate Information (identified by operation id):---------------------------------------------------   1 - filter((("T"."START_DATE" IS NULL OR              "T"."START_DATE"<=SYSDATE@!) AND ("T"."END_DATE" IS NULL OR              "T"."END_DATE">SYSDATE@!)))Note-----   - dynamic statistics used: dynamic sampling (level=2)24 rows selected.ops$tkyte%ORA12CR1> select * from addresses as of period for valid sysdate+3;     EMPNO ADDR_DATA                      START_DAT END_DATE---------- ------------------------------ --------- ---------      1234 789 1st Ave                    04-JUL-13ops$tkyte%ORA12CR1> @planops$tkyte%ORA12CR1> select * from table(dbms_xplan.display_cursor);PLAN_TABLE_OUTPUT-------------------------------------------------------------------------------SQL_ID  36bq7shnhc888, child number 0-------------------------------------select * from addresses as of period for valid sysdate+3Plan hash value: 3184888728-------------------------------------------------------------------------------| Id  | Operation         | Name      | Rows  | Bytes | Cost (%CPU)| Time     |-------------------------------------------------------------------------------|   0 | SELECT STATEMENT  |           |       |       |     3 (100)|          ||*  1 |  TABLE ACCESS FULL| ADDRESSES |     1 |    48 |     3   (0)| 00:00:01 |-------------------------------------------------------------------------------Predicate Information (identified by operation id):---------------------------------------------------   1 - filter((("T"."START_DATE" IS NULL OR              "T"."START_DATE"<=SYSDATE@!+3) AND ("T"."END_DATE" IS NULL OR              "T"."END_DATE">SYSDATE@!+3)))Note-----   - dynamic statistics used: dynamic sampling (level=2)24 rows selected.All in all a nice, easy way to query effective dated information as of a point in time without a complex where clause.  You need to maintain the data - it isn't that a delete will turn into an update the end dates a record or anything - but if you have tables with start/end dates, this will make it much easier to query them.

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• osx snow leopard freezes

  - by lydonchandra

  Hi I got this error: Timexxxx In 'CFPasteboardCopyData', file /SourceCache/CF/CF-550.13/AppServices.subproj/CFPasteboard.c, line 1951, during lock, spin lock 0x15457a0c8 has value 0xf0000000, which is neither locked nor unlocked. The memory has been smashed. My Mac freezes except the mouse and keyboard. What is happening and how can I prevent this from happening in the future?

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• SBS 2008 Backup Drive Full - Error Code '2147942512'

  - by HK1

  We are using Windows Backup on SBS 2008 SP2 and backing up to 1TB external hard drives. Recently after switching drives our backup started failing because the backup drive is full and auto-delete isn't automatically deleting older backups/show copies. I'm trying to get more information to help me effectively prevent this problem from reoccurring in the future. How I can tell that the drive is getting full: In the event viewer under Windows Logs Application, I'm seeing Event ID 517 but it fails to show an intelligible description. However, under Applications and Services Logs Microsoft Windows Backup Operational, I'm seeing an event with the ID of 5 and a description like this: Backup started at '10/4/2011 12:30:12 PM' failed with following error code '2147942512'. One of the most informative posts I've found on this error is located on Microsoft's Technet Forums here. In that post, a Microsoft representative gives this hazy explanation: auto-delete feature to ensure that at least some old backup copies are maintained on the disk -- does not automatically delete backups if space utilization by older copies is less than 1/8 of the disk size or in other words, 13% of the disk size. that means if the one full backup copy does not fit in the 7/8 of the disk size, backup may fail with disk full error. auto-delete will not automatically delete older versions to reclaim more older versions of backup. In the above explanation, I do not understand what is meant by "older copies" except that it appears that anything older than the very last shadow copy would be considered "older copies". I'm going to make the assumption that this problem where auto-delete will not work will affect any hard drive that is large enough to make an effective backup drive, or in other words, any hard drive that is large enough to hold more than one backup/shadow copy at once. The same MS representative proposes the solution of using a larger backup drive. I can't understand how this will help. It appears to me it will simply delay the problem until a later date. In order to resolve this problem for now, I did the following: Assign the backup drive a disk letter under disk management. Run the command line with Administrative rights. diskshadow.exe [enter] delete shadows oldest x: [enter] (where X: is the letter you assigned your backup drive) I manually ran the above command some 60 or 80 times to free up about 200 GB of space on my 1 Terrabyte External Hard drive. However, I do not feel this is a satisfactory solution to prevent the problem from happening again in the future. Does anyone have a solution to prevent your Windows Server backup drive from getting full?

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• USB 3 vs. eSATA

  - by Robert Nickens

  Will the full speed advantages of the future USB 3.0 be negated by the fact the most HD being mass produced are SATA 3? If so, what would you suggest a person do? For performance reasons go with eSATA or 1394 for external HDs. Why spend the money on USB 3.0 next year,even if the prices come down quickly. Given that SATA 6 is not here and may be a while.

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• Buying used MacBook, what to look at?

  - by Wojtek

  I'm planning to buy used MacBook, I'm looking for more recent models, but detailed specification is not important. I would like to know what should I especially look at when buying used MacBook? What are common flaws in those models (manufactured 2009/2010)? I don't care about minor damages, like scratches, but would like to know what symptoms of repair/previous damage/possible failures in the future are?

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• Change spelling check language for a Document in Microsoft Word 2010

  - by hvtuananh

  Usually I use Microsoft Word 2010 to write English documents Now I'm editing a document of another language, and want to change the spelling check language of this document This change should not affect other documents (means does not saved by default) so I can work with English documents in the future Any clue? Thanks in advance.

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• Is ext4 ready for a production usage ?

  - by Konstantin

  Hi What do you think about ext4 filesystem in the production enviroment ? We are very close to launching our project that will use tens of millions quite often updated not very big files and we need to decide which FS to use. For a while our considerations about other linux FS are: Ext3 is rock stable, but not very well suited for handling millions small files XFS looks very nice, probably we'll use it ReiserFS ... well...vague future, who will end up fixing bugs ?

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• Windows 7 on laptop hard drive does not boot after installing Windows to Go on external hard drive

  - by user1687031

  Just successfully installed and ran Windows 8's Windows to Go on a USB external hard drive. However, after shutting down and removing the USB hard disk, whey I to start my laptop (with only Windows 7 installed), but it doesn't boot and trying to repair it doesn't work. It seems that Windows 8 had corrupted the partition table on the laptop's hard drive, causing Windows 7 to fail to boot. How do I fix that and avoid future problems of the same type?

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• How do I delete old calendar items in Outlook 2003?

  - by Ramesh

  Hi. I'm trying to delete old calendar items (I have a few years' worth) in Outlook and was wondering if there was a way to delete only non-recurring items as I need the recurring events for the future. I tried View Arrange by Current view Category and figured that I could manually check and delete any calendar items by hand. Is there a more efficient way to do this without having to actually script code? Thanks for your time!

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• Hijack.StartMenu Malwarebytes Anti-Malware is a false positive?

  - by Senseful

  I just ran the Malwarebytes Anti-Malware quick scan for the first time and it found: Registry Data Items Infected: HKEY_CURRENT_USER\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\Advanced\Start_ShowSearch (Hijack.StartMenu) - Bad: (0) Good: (1) - No action taken. I just wanted to double check (and provide a top Google result for people in the future that might have the same issue) that this was a false positive and can be safely right-click ignored.

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• WOL not working with two NIC's

  - by amazinghorse24

  We have recently moved from a windows 2003 server to an 08 R2. Running the program from the command line says that the magic packet has successfully been sent but it never actually reached the destination computer. We have two NIC's on the server. If I disable the NIC that isn't (currently) in use, WOL will work fine, but in the future we will need to use both NIC's. Also, we use MAC Addresses for WOL.

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• Mac OS Snow Leopard freezes

  - by lydonchandra

  I got this error: Timexxxx In 'CFPasteboardCopyData', file /SourceCache/CF/CF-550.13/AppServices.subproj/CFPasteboard.c, line 1951, during lock, spin lock 0x15457a0c8 has value 0xf0000000, which is neither locked nor unlocked. The memory has been smashed. My Mac freezes except the mouse and keyboard. What is happening and how can I prevent this from happening in the future?

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• LaTeX presentation - which package

  - by Maciej Piechotka

  I need to create a technical presenatation (just a few slides but with formulas etc.). It seems that LaTeX is a natural choice. However - which package should I use and why (the second part is important as probably for the first one there is no right answer)? As far I found Beamer Prosper I know that I can use either but: There may be better one which I'll use in future There may be a kill-features I have no idea about Thank you in advance for answers and lack of flames ;)

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• How does superuser install app to run for normal user?

  - by RPfromPR

  As admin (root) for a group of computers, I have to now install a content filter on a shared Mac, to first catch illegal downloads, and to prevent future peer to peer DL by monitoring. I can install the OSX app for myself (as admin) and have it run for any new users, but I have to have it installed and enabled it for existing users. How can I install an OSX app, to run for normal users, when it requires that it be install as admin (root) for each user?

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• Toast vs Disk Util?

  - by Grishanko

  I have several users that are insisting on the purchase of Toast. They will be using it to make backups of disks at possibly re-burn them if needed. I have used Disk Utility for that function. At this point there is no addition functionality needed. However, that can always change in the future. Is there any advantages or disadvantages to either solution?

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• How can I prevent tmux exiting with Ctrl-d?

  - by Cas

  I use tmux on my server and recently I found to my cost that ctrl-d will exit tmux and lose all the session information, my intention was to simply end the ssh session but failed to notice I was still in tmux until too late. I am aware that I should be careful in future when using ctrl-d but I wondered if there a way to prevent tmux for exiting when hitting ctrl-d by accident? A solution such as a prompt, confirmation or detaching would be fine.

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• PCI-e v2.0 video card in a PCI-e v1.0 slot? [closed]

  - by Kevin

  Possible Duplicate: Will a PCI-E V2.0 Graphics Card work with a PCI-E V1.0 Motherboard? Will a PCI-e 2.0 card work in a PCI-e 1.0 motherboard? Currently I've got an older ASUS M2N-E motherboard, and I would like get a newer video card (GTX 280 or similar) which will last me a while after I upgrade my motherboard at some point in the future. I currently have a 6600 GT which has served me well for a long time, but it's time to upgrade.

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• Is it safe to install dotnet 3.5 on an IIS server running a dotnet 1.1 web application?

  - by MGOwen

  If I recall correctly, this is fine, the different versions coexist peacefully, but I just want to double-check there's no possibility of problems (I'm installing the newer version of the .net framework on an older production server in preparation for upgrading a critical asp.net 1.1 app to 3.5 in the near future).

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• Need a good mp3/internet radio organization system...

  - by Zombies

  So I feel that winamp alone doesn't work well for me. I have this one playlist that all kinds of stuff gets crammed into. I need a system (this can easily be 1 program or several): Need to be able to... play mp3's from my library (just a directory structure with mp3's). Save radio station's, and easily remove/add new stations play random mp3's which are not part of my library and will probably be deleted in the future, yet won't clutter my library index!

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• What PSU would be needed for a mid-range computer?

  - by iconiK

  I am building a mid-range computer primarily for gaming and graphic design. With the following components, what power supply unit would be good, in terms of having ample power for future expansion, with good efficiency and quiet operation, but most important, reliability in the long (5+ years) run? Gigabyt GA-H67MA-UD2H LGA 1155 Intel Core i5 2300 2.8GHz Crucial CT2KIT51264BA1339 2x4GB Kit ASUS HD 6850 DirectCU Intel X25-V 40GB SSD 2xSeagate 7200.12 1TB HDD RAID 1 Antec NSK-3480 µATX Case

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