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• SQL SERVER – Weekly Series – Memory Lane – #039

  - by Pinal Dave

  Here is the list of selected articles of SQLAuthority.com across all these years. Instead of just listing all the articles I have selected a few of my most favorite articles and have listed them here with additional notes below it. Let me know which one of the following is your favorite article from memory lane. 2007 FQL – Facebook Query Language Facebook list following advantages of FQL: Condensed XML reduces bandwidth and parsing costs. More complex requests can reduce the number of requests necessary. Provides a single consistent, unified interface for all of your data. It’s fun! UDF – Get the Day of the Week Function The day of the week can be retrieved in SQL Server by using the DatePart function. The value returned by the function is between 1 (Sunday) and 7 (Saturday). To convert this to a string representing the day of the week, use a CASE statement. UDF – Function to Get Previous And Next Work Day – Exclude Saturday and Sunday While reading ColdFusion blog of Ben Nadel Getting the Previous Day In ColdFusion, Excluding Saturday And Sunday, I realize that I use similar function on my SQL Server Database. This function excludes the Weekends (Saturday and Sunday), and it gets previous as well as next work day. Complete Series of SQL Server Interview Questions and Answers Data Warehousing Interview Questions and Answers – Introduction Data Warehousing Interview Questions and Answers – Part 1 Data Warehousing Interview Questions and Answers – Part 2 Data Warehousing Interview Questions and Answers – Part 3 Data Warehousing Interview Questions and Answers Complete List Download 2008 Introduction to Log Viewer In SQL Server all the windows event logs can be seen along with SQL Server logs. Interface for all the logs is same and can be launched from the same place. This log can be exported and filtered as well. DBCC SHRINKFILE Takes Long Time to Run If you are DBA who are involved with Database Maintenance and file group maintenance, you must have experience that many times DBCC SHRINKFILE operations takes a long time but any other operations with Database are relatively quicker. mssqlsystemresource – Resource Database The purpose of resource database is to facilitates upgrading to the new version of SQL Server without any hassle. In previous versions whenever version of SQL Server was upgraded all the previous version system objects needs to be dropped and new version system objects to be created. 2009 Puzzle – Write Script to Generate Primary Key and Foreign Key In SQL Server Management Studio (SSMS), there is no option to script all the keys. If one is required to script keys they will have to manually script each key one at a time. If database has many tables, generating one key at a time can be a very intricate task. I want to throw a question to all of you if any of you have scripts for the same purpose. Maximizing View of SQL Server Management Studio – Full Screen – New Screen I had explained the following two different methods: 1) Open Results in Separate Tab - This is a very interesting method as result pan shows up in a different tab instead of the splitting screen horizontally. 2) Open SSMS in Full Screen - This works always and to its best. Not many people are aware of this method; hence, very few people use it to enhance performance. 2010 Find Queries using Parallelism from Cached Plan T-SQL script gets all the queries and their execution plan where parallelism operations are kicked up. Pay attention there is TOP 10 is used, if you have lots of transactional operations, I suggest that you change TOP 10 to TOP 50 This is the list of the all the articles in the series of computed columns. SQL SERVER – Computed Column – PERSISTED and Storage This article talks about how computed columns are created and why they take more storage space than before. SQL SERVER – Computed Column – PERSISTED and Performance This article talks about how PERSISTED columns give better performance than non-persisted columns. SQL SERVER – Computed Column – PERSISTED and Performance – Part 2 This article talks about how non-persisted columns give better performance than PERSISTED columns. SQL SERVER – Computed Column and Performance – Part 3 This article talks about how Index improves the performance of Computed Columns. SQL SERVER – Computed Column – PERSISTED and Storage – Part 2 This article talks about how creating index on computed column does not grow the row length of table. SQL SERVER – Computed Columns – Index and Performance This article summarized all the articles related to computed columns. 2011 SQL SERVER – Interview Questions and Answers – Frequently Asked Questions – Data Warehousing Concepts – Day 21 of 31 What is Data Warehousing? What is Business Intelligence (BI)? What is a Dimension Table? What is Dimensional Modeling? What is a Fact Table? What are the Fundamental Stages of Data Warehousing? What are the Different Methods of Loading Dimension tables? Describes the Foreign Key Columns in Fact Table and Dimension Table? What is Data Mining? What is the Difference between a View and a Materialized View? SQL SERVER – Interview Questions and Answers – Frequently Asked Questions – Data Warehousing Concepts – Day 22 of 31 What is OLTP? What is OLAP? What is the Difference between OLTP and OLAP? What is ODS? What is ER Diagram? SQL SERVER – Interview Questions and Answers – Frequently Asked Questions – Data Warehousing Concepts – Day 23 of 31 What is ETL? What is VLDB? Is OLTP Database is Design Optimal for Data Warehouse? If denormalizing improves Data Warehouse Processes, then why is the Fact Table is in the Normal Form? What are Lookup Tables? What are Aggregate Tables? What is Real-Time Data-Warehousing? What are Conformed Dimensions? What is a Conformed Fact? How do you Load the Time Dimension? What is a Level of Granularity of a Fact Table? What are Non-Additive Facts? What is a Factless Facts Table? What are Slowly Changing Dimensions (SCD)? SQL SERVER – Interview Questions and Answers – Frequently Asked Questions – Data Warehousing Concepts – Day 24 of 31 What is Hybrid Slowly Changing Dimension? What is BUS Schema? What is a Star Schema? What Snow Flake Schema? Differences between the Star and Snowflake Schema? What is Difference between ER Modeling and Dimensional Modeling? What is Degenerate Dimension Table? Why is Data Modeling Important? What is a Surrogate Key? What is Junk Dimension? What is a Data Mart? What is the Difference between OLAP and Data Warehouse? What is a Cube and Linked Cube with Reference to Data Warehouse? What is Snapshot with Reference to Data Warehouse? What is Active Data Warehousing? What is the Difference between Data Warehousing and Business Intelligence? What is MDS? Explain the Paradigm of Bill Inmon and Ralph Kimball. SQL SERVER – Azure Interview Questions and Answers – Guest Post by Paras Doshi – Day 25 of 31 Paras Doshi has submitted 21 interesting question and answers for SQL Azure. 1.What is SQL Azure? 2.What is cloud computing? 3.How is SQL Azure different than SQL server? 4.How many replicas are maintained for each SQL Azure database? 5.How can we migrate from SQL server to SQL Azure? 6.Which tools are available to manage SQL Azure databases and servers? 7.Tell me something about security and SQL Azure. 8.What is SQL Azure Firewall? 9.What is the difference between web edition and business edition? 10.How do we synchronize On Premise SQL server with SQL Azure? 11.How do we Backup SQL Azure Data? 12.What is the current pricing model of SQL Azure? 13.What is the current limitation of the size of SQL Azure DB? 14.How do you handle datasets larger than 50 GB? 15.What happens when the SQL Azure database reaches Max Size? 16.How many databases can we create in a single server? 17.How many servers can we create in a single subscription? 18.How do you improve the performance of a SQL Azure Database? 19.What is code near application topology? 20.What were the latest updates to SQL Azure service? 21.When does a workload on SQL Azure get throttled? SQL SERVER – Interview Questions and Answers – Guest Post by Malathi Mahadevan – Day 26 of 31 Malachi had asked a simple question which has several answers. Each answer makes you think and ponder about the reality of the IT world. Look at the simple question – ‘What is the toughest challenge you have faced in your present job and how did you handle it’? and its various answers. Each answer has its own story. SQL SERVER – Interview Questions and Answers – Guest Post by Rick Morelan – Day 27 of 31 Rick Morelan of Joes2Pros has written an excellent blog post on the subject how to find top N values. Most people are fully aware of how the TOP keyword works with a SELECT statement. After years preparing so many students to pass the SQL Certification I noticed they were pretty well prepared for job interviews too. Yes, they would do well in the interview but not great. There seemed to be a few questions that would come up repeatedly for almost everyone. Rick addresses similar questions in his lucid writing skills. 2012 Observation of Top with Index and Order of Resultset SQL Server has lots of things to learn and share. It is amazing to see how people evaluate and understand different techniques and styles differently when implementing. The real reason may be absolutely different but we may blame something totally different for the incorrect results. Read the blog post to learn more. How do I Record Video and Webcast How to Convert Hex to Decimal or INT Earlier I asked regarding a question about how to convert Hex to Decimal. I promised that I will post an answer with Due Credit to the author but never got around to post a blog post around it. Read the original post over here SQL SERVER – Question – How to Convert Hex to Decimal. Query to Get Unique Distinct Data Based on Condition – Eliminate Duplicate Data from Resultset The natural reaction will be to suggest DISTINCT or GROUP BY. However, not all the questions can be solved by DISTINCT or GROUP BY. Let us see the following example, where a user wanted only latest records to be displayed. Let us see the example to understand further. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: Memory Lane, PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology

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• BizTalk: mapping with Xslt

  - by Leonid Ganeline

  BizTalk Map Editor (Mapper) is a good editor, especially in the last 2010 version of the BizTalk. But still sometimes it cannot do the tasks easily. It is time for the Xslt code, It is time to remember that the maps are executed by the Xslt engine.  Right-click the Mapper Grid (a field between the source and target schemas) and choose Properties /Custom XSLT Path.  Input here a name of the file with Xslt code. Only this code will be executed, forget the picture in the Mapper, all those links and functoids.  Let’s see the real-life example. There are two source Addresses. One is on the top level and the second is inside the Member_Address record with MaxOccurs=* . The target address is placed inside the Locator record with MaxOccurs=*. The requirement is to map all source address to the one target address structure. The source Xml document looks like: The result Xml should be like this: Try to do this mapping with the Mapper and you will spent good amount of time and the result map would be tricky. If we use the Xslt code, the mapping will be simple and unambiguous, like this: Simple, elegant.

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• Issue 15: SVP Focus

  - by rituchhibber

       SVP FOCUS FOCUS -- Chris Baker SVP Oracle Worldwide ISV-OEM-Java Sales Chris Baker is the Global Head of ISV/OEM Sales responsible for working with ISV/OEM partners to maximise Oracle's business through those partners, whilst maximising those partners’ business to their end users. Chris works with partners, customers, innovators, investors and employees to develop innovative business solutions using Oracle products, services and skills. RESOURCES -- Oracle PartnerNetwork (OPN) OPN Solutions Catalog Oracle Exastack Program Oracle Exastack Optimized Oracle Cloud Computing Oracle Engineered Systems Oracle and Java SUBSCRIBE FEEDBACK PREVIOUS ISSUES "By taking part in marketing activities, our partners accelerate their sales cycles." -- Firstly, could you please explain Oracle's current strategy for ISV partners, globally and in EMEA? Oracle customers use independent software vendor (ISV) applications to run their businesses. They use them to generate revenue and to fulfil obligations to their own customers. Our strategy is very straight-forward. We want all of our ISV partners and OEMs to concentrate on the things that they do the best—building applications to meet the unique industry and functional requirements of their customer. We want to ensure that we deliver a best-in-class application platform so ISVs are free to concentrate their effort on their application functionality and user experience We invest over four billion dollars in research and development every year, and we want our ISVs to benefit from all of that investment in operating systems, virtualisation, databases, middleware, engineered systems, and other hardware. By doing this, we help them to reduce their costs, gain more consistency and agility for quicker implementations, and also rapidly differentiate themselves from other application vendors. It's all about simplification because we believe that around 25 to 30 percent of the development costs incurred by many ISVs are caused by customising infrastructure and have nothing to do with their applications. Our strategy is to enable our ISV partners to standardise their application platform using engineered architecture, so they can write once to the Oracle stack and deploy seamlessly in the cloud, on-premise, or in hybrid deployments. It's really important that architecture is the same in order to keep cost and time overheads at a minimum, so we provide standardisation and an environment that enables our ISVs to concentrate on the core business that makes them the most money and brings them success. How do you believe this strategy is helping the ISVs to work hand-in-hand with Oracle to ensure that end customers get the industry-leading solutions that they need? We work with our ISVs not just to help them be successful, but also to help them market themselves. We have something called the 'Oracle Exastack Ready Program', which enables ISVs to publicise themselves as 'Ready' to run the core software platforms that run on Oracle's engineered systems including Exadata and Exalogic. So, for example, they can become 'Database Ready' which means that they use the latest version of Oracle Database and therefore can run their application without modification on Exadata or the Oracle Database Appliance. Alternatively, they can become WebLogic Ready, Oracle Linux Ready and Oracle Solaris Ready which means they run on the latest release and therefore can run their application, with no new porting work, on Oracle Exalogic. Those 'Ready' logos are important in helping ISVs advertise to their customers that they are using the latest technologies which have been fully tested. We now also have Exadata Ready and Exalogic Ready programmes which allow ISVs to promote the certification of their applications on these platforms. This highlights these partners to Oracle customers as having solutions that run fluently on the Oracle Exadata Database Machine, the Oracle Exalogic Elastic Cloud or one of our other engineered systems. This makes it easy for customers to identify solutions and provides ISVs with an avenue to connect with Oracle customers who are rapidly adopting engineered systems. We have also taken this programme to the next level in the shape of 'Oracle Exastack Optimized' for partners whose applications run best on the Oracle stack and have invested the time to fully optimise application performance. We ensure that Exastack Optimized partner status is promoted and supported by press releases, and we help our ISVs go to market and differentiate themselves through the use of our technology and the standardisation it delivers. To date we have had several hundred organisations successfully work through our Exastack Optimized programme. How does Oracle's strategy of offering pre-integrated open platform software and hardware allow ISVs to bring their products to market more quickly? One of the problems for many ISVs is that they have to think very carefully about the technology on which their solutions will be deployed, particularly in the cloud or hosted environments. They have to think hard about how they secure these environments, whether the concern is, for example, middleware, identity management, or securing personal data. If they don't use the technology that we build-in to our products to help them to fulfil these roles, they then have to build it themselves. This takes time, requires testing, and must be maintained. By taking advantage of our technology, partners will now know that they have a standard platform. They will know that they can confidently talk about implementation being the same every time they do it. Very large ISV applications could once take a year or two to be implemented at an on-premise environment. But it wasn't just the configuration of the application that took the time, it was actually the infrastructure - the different hardware configurations, operating systems and configurations of databases and middleware. Now we strongly believe that it's all about standardisation and repeatability. It's about making sure that our partners can do it once and are then able to roll it out many different times using standard componentry. What actions would you recommend for existing ISV partners that are looking to do more business with Oracle and its customer base, not only to maximise benefits, but also to maximise partner relationships? My team, around the world and in the EMEA region, is available and ready to talk to any of our ISVs and to explore the possibilities together. We run programmes like 'Excite' and 'Insight' to help us to understand how we can help ISVs with architecture and widen their environments. But we also want to work with, and look at, new opportunities - for example, the Machine-to-Machine (M2M) market or 'The Internet of Things'. Over the next few years, many millions, indeed billions of devices will be collecting massive amounts of data and communicating it back to the central systems where ISVs will be running their applications. The only way that our partners will be able to provide a single vendor 'end-to-end' solution is to use Oracle integrated systems at the back end and Java on the 'smart' devices collecting the data—a complete solution from device to data centre. So there are huge opportunities to work closely with our ISVs, using Oracle's complete M2M platform, to provide the infrastructure that enables them to extract maximum value from the data collected. If any partners don't know where to start or who to contact, then they can contact me directly at [email protected] or indeed any of our teams across the EMEA region. We want to work with ISVs to help them to be as successful as they possibly can through simplification and speed to market, and we also want all of the top ISVs in the world based on Oracle. What opportunities are immediately opened to new ISV partners joining the OPN? As you know OPN is very, very important. New members will discover a huge amount of content that instantly becomes accessible to them. They can access a wealth of no-cost training and enablement materials to build their expertise in Oracle technology. They can download Oracle software and use it for development projects. They can help themselves become more competent by becoming part of a true community and uncovering new opportunities by working with Oracle and their peers in the Oracle Partner Network. As well as publishing massive amounts of information on OPN, we also hold our global Oracle OpenWorld event, at which partners play a huge role. This takes place at the end of September and the beginning of October in San Francisco. Attending ISV partners have an unrivalled opportunity to contribute to elements such as the OpenWorld / OPN Exchange, at which they can talk to other partners and really begin thinking about how they can move their businesses on and play key roles in a very large ecosystem which revolves around technology and standardisation. Finally, are there any other messages that you would like to share with the Oracle ISV community? The crucial message that I always like to reinforce is architecture, architecture and architecture! The key opportunities that ISVs have today revolve around standardising their architectures so that they can confidently think: "I will I be able to do exactly the same thing whenever a customer is looking to deploy on-premise, hosted or in the cloud". The right architecture is critical to being competitive and to really start changing the game. We want to help our ISV partners to do just that; to establish standard architecture and to seize the opportunities it opens up for them. New market opportunities like M2M are enormous - just look at how many devices are all around you right now. We can help our partners to interface with these devices more effectively while thinking about their entire ecosystem, rather than just the piece that they have traditionally focused upon. With standardised architecture, we can help people dramatically improve their speed, reach, agility and delivery of enhanced customer satisfaction and value all the way from the Java side to their centralised systems. All Oracle ISV partners must take advantage of these opportunities, which is why Oracle will continue to invest in and support them. Oracle OpenWorld 2010 Whether you attended Oracle OpenWorld 2009 or not, don't forget to save the date now for Oracle OpenWorld 2010. The event will be held a little earlier next year, from 19th-23rd September, so please don't miss out. With thousands of sessions and hundreds of exhibits and demos already lined up, there's no better place to learn how to optimise your existing systems, get an inside line on upcoming technology breakthroughs, and meet with your partner peers, Oracle strategists and even the developers responsible for the products and services that help you get better results for your end customers. Register Now for Oracle OpenWorld 2010! Perhaps you are interested in learning more about Oracle OpenWorld 2010, but don't wish to register at this time? Great! Please just enter your contact information here and we will contact you at a later date. How to Exhibit at Oracle OpenWorld 2010 Sponsorship Opportunities at Oracle OpenWorld 2010 Advertising Opportunities at Oracle OpenWorld 2010 -- Back to the welcome page

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• Paper Gold Rush

  - by Chris G. Williams

  The last few days at the shop have been reminiscent of a marathon of Pawn Stars. Quite a few people have come in wanting to trade for store credit. Most of them have left disappointed. We did pick up a few things here and there (which hopefully I can sell.) The problem, in a nutshell, is that people get it in their head that a (YuGiOh) card is worth X amount because they looked it up 2-3 years a...go, or someone told them it was valuable... then they play it in their deck for a year without sleeves, and cram it in a binder covered in duct tape. By the time they bring the cards in to me, new sets have come out which often de-value the tournament usefulness of the card from $20 to *maybe* 50 cents, in mint condition. Which means I can offer them about 10-15 cents... only they are almost never in mint condition, which means I usually offer them nothing at all. Most of the time, you can watch their smile fade as I start going through their cards. It's kinda sad, really, since I know they think they've spent the last two years walking around with the keys to their own personal gold mine. I don't really enjoy seeing that look on a child's face. I like kids and I remember those moments when perception and reality crashed headlong into each other. It was seldom pretty. So, when I'm talking to a child, I try to take it easy on them and give them some suggestions on how to better preserve their cards. Sometimes though, it's an adult. Depending on the situation, my response to them varies pretty broadly. Most of the time though, I still feel pretty bad when it doesn't go their way.

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• Coders For Charities

  - by Robz / Fervent Coder

  Last weekend I had the opportunity to give back to the community doing what I love. As geeks we don’t usually have this opportunity. The event is called Coders 4 Charities (C4C) and it’s a grueling weekend of coding for nearly 30 hours over the weekend. When you finish you get to present to the charity and all of the other groups what you have completed. From the site: Coders For Charities is a 3-day charity event that pairs charities and local software developers. Charities often do not have the funds to implement a new website or intranet or database solution. Software developers often do not volunteer for charities because their skills do not apply. This event is the perfect marriage of these two needs; software developers volunteering their time to help charities better serve their community though the latest technology! The actual event was lined with multiple charities and about 50 developers, designers, business analysts, etc, each working with a different charity to come up with a solution that they could implement in less than 3 days. C4C provided a place and food for us so that we wouldn’t have to leave much during the time we had to implement our solution. They also provided games like Rock Band so we could get away and clear our minds for a few moments if necessary. I don’t think we made it down there to play, but the food and drinks were a huge help for us. The charity we we picked was Harvest Home. They had a need for an online intranet site where they could track membership and gardening. Over the next few days we worked on a site we could give them. Below is a screen shot with private data marked out. It was an awesome and humbling experience to be able to give back to a charity and I’m happy I was a part of it. I would definitely do it again. How often do we get to use our abilities to volunteer our time to a charity?

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• Bootloader error Ubuntu 12.04, system goes to Grub-rescue instead of booting

  - by user83508

  I am trying to install ubuntu 12.04 on my system but it is constantly giving me bootloader install fail error. I have tried to lot to solve this issue but reading articles over the internet but still no gain. Firstly since the bootloader was not getting installed I tried to install it on all the alternative paths given in the installer, failing with I selected install ubuntu without bootloader. Then I tried to manually install bootloader via terminal at try ubuntu via grub-install, but I was not able to do that. Then I tried using boot-repair and it was also not able to install the bootloader because after it my system shows grub-rescue. I tried to use boot-repair and install bootloader on a seperate partition mounted to /boot and still my system is booting and it still shows grub-rescue. The error which my system shows during boot is: Error : no such device : 04ac0510-bd4f-43b8-b885-b885-11c4dec21db8 I am not dual booting and ubuntu is the only OS I am installing. I am using Raid 0 with two blue western digital hard drive so I am not sure whether it is right or not. The details given by boot-repair are in the below mentioned link; http://paste.ubuntu.com/1147208/ Afterwards, I made one more change I installed ubuntu again and this time I installed the bootloader at a different partition on /boot. After this the bootloader error has gone but I am still not able to boot to ubuntu as I get the same error I was getting before. I have not installed dmraid, I feel it is neccessary for Raid0, but I thought ubuntu already has Raid drivers. Moreover in the dmraid installation instructions for 12.04, I used the one for 10.04 and selected to install bootloader at the partitions from the dropdown. This time the installation finished normally without an error but still I am not able to boot my system as the same error shows during booting this time also. Now I am stucked and I have no clue on how I can boot my system. Please tell me how can I boot my system.

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• How to install the latest version of google earth on ubuntu 12.10 64-bit?

  - by user114769

  Chris here with a huge problem with the Google earth latest version. Gosh.. whenever I try to lunch the app this comes out. I'v Tried this web site nothing worked: (THANK YOU SO MUCH FOR EVEN READING THIS. MAY YOU GUYS HAVE A NICE DAY. christopher@christopher-E4300:~$ google-earth Google Earth has caught signal 11. We apologize for the inconvenience, but Google Earth has crashed. This is a bug in the program, and should never happen under normal circumstances. A bug report and debugging data have been written to this text file: /home/christopher/.googleearth/crashlogs/crashlog-50cbd67e.txt Please include this file if you submit a bug report to Google. https://help.ubuntu.com/community/GoogleEarth#Installing_the_.deb_file_downloaded_from_the_Google_Earth_Website Here is the content of /home/christopher/.googleearth/crashlogs/crashlog-50cbd67e.txt Major Version 7 Minor Version 0 Build Number 0001 Build Date Oct 29 2012 Build Time 19:13:39 OS Type 3 OS Major Version 3 OS Minor Version 5 OS Build Version 0 OS Patch Version 0 Crash Signal 11 Crash Time 1355535998 Up Time 0.789556 Stacktrace from glibc: ./libgoogleearth_free.so(+0x1e9cfb)[0xf757dcfb] ./libgoogleearth_free.so(+0x1e9f43)[0xf757df43] [0xf7726400]

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• The Cloud is STILL too slow!

  - by harry.foxwell(at)oracle.com

  If you've been in the computing industry sufficiently long enough to remember dialup modems and other "ancient" technologies, you might be tempted to marvel at today's wonderfully powerful multicore PCs, ginormous disks, and blazingly fast networks.  Wow, you're in Internet Nirvana, right!  Well, no, not by a long shot.Considering the exponentially growing expectations of what the Web, that is, "the Cloud", is supposed to provide, today's Web/Cloud services are still way too slow.Already we are seeing cloud-enabled consumer devices that are stressing even the most advanced public network services.  Like the iPad and its competitors, ever more powerful smart-phones, and an imminent hoard of special purpose gadgets such as the proposed "cloud camera" (see http://gdgt.com/discuss/it-time-cloud-camera-found-out-cnr/ ).And at the same time that the number and type of cloud services are growing, user tolerance for even the slightest of download delays is rapidly decreasing.  Ten years ago Web developers followed the "8-Second Rule", (average time a typical Web user would tolerate for a page to download and render).  Not anymore; now it's less than 3 seconds, and only a bit longer for mobile devices (see http://www.technologyreview.com/files/54902/GoogleSpeed_charts.pdf).  How spoiled we've become!Google, among others, recognizes this problem and is working to encourage the development of a faster Web (see http://www.technologyreview.com/web/32338/). They, along with their competitors and ISPs, will have to encourage and support significantly better Web performance in order to provide the types of services envisioned for the Cloud.  How will they do this? Through the development of faster components, better use of caching technologies, and the really tough one - exploiting parallelism. Not that parallel technologies like multicore processors are hard to build...we already have them.  It's just that we're not that good yet at using them effectively.  And if we don't get better, users will abandon cloud-based services...in less than 3 seconds.

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• debugging JBoss 100% CPU usage

  - by NateS

  Originally posted on Server Fault, where it was suggested this question might better asked here. We are using JBoss to run two of our WARs. One is our web app, the other is our web service. The web app accesses a database on another machine and makes requests to the web service. The web service makes JMS requests to other machines, aggregates the data, and returns it. At our biggest client, about once a month the JBoss Java process takes 100% of all CPUs. The machine running JBoss has 8 CPUs. Our web app is still accessible during this time, however pages take about 3 minutes to load. Restarting JBoss restores everything to normal. The database machine and all the other machines are fine, only the machine running JBoss is affected. Memory usage is normal. Network utilization is normal. There are no suspect error messages in the JBoss logs. I have set up a test environment as close as possible to the client's production environment and I've done load testing with as much as 2x the number of concurrent users. I have not gotten my test environment to replicate the problem. Where do we go from here? How can we narrow down the problem? Currently the only plan we have is to wait until the problem occurs in production on its own, then do some debugging to determine the cause. So far people have just restarted JBoss when the problem occurred to minimize down time. Next time it happens they will get a developer to take a look. The question is, next time it happens, what can be done to determine the cause? We could setup a separate JBoss instance on the same box and install the web app separately from the web service. This way when the problem next occurs we will know which WAR has the problem (assuming it is our code). This doesn't narrow it down much though. Should I enable JMX remote? This way the next time the problem occurs I can connect with VisualVM and see which threads are taking the CPU and what the hell they are doing. However, is there a significant down side to enabling JMX remote in a production environment? Is there another way to see what threads are eating the CPU and to get a stacktrace to see what they are doing? Any other ideas? Thanks!

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• The Next RAC, ASM and Linux Forum. May 4, 2010 Beit HP Raanana

  - by alejandro.vargas

  The next RAC, ASM and Linux forum will take place next week, you are still on time to register : Israel Oracle Users Group RAC,ASM and Linux Forum This time we will have a panel formed by Principal Oracle Advanced Customer Services Engineers and RAC experts Galit Elad and Nickita Chernovski and Senior Oracle Advanced Customer Services Engineers and RAC experts Roy Burstein and Dorit Noga. They will address the subject: 5 years of experience with RAC at Israeli Customers, lessons learned. It is a wonderful opportunity to meet with the people that is present at most major implementations and helped to solve all major issues along the last years. In addition we will have 2 most interesting Customer Presentations: Visa Cal DBA Team Leader Harel Safra will tell about their experience with scalability using standard Linux Servers for their mission critical data warehouse. Bank Discount Infrastructure DBA Uril Levin, who is in charge of the Bank Backup and Recovery Project, will speak about their Corporate Backup Solution using RMAN; that includes an end to end solution for VLDBS and mission critical databases. One of the most interesting RMAN implementations in Israel. This time I will not be able to attend myself as I'm abroad on business, Galit Elad will greet you and will lead the meeting. I'm sure you will enjoy a very, very interesting meeting. Best Regards Alejandro

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• Exalogic&ndash;The One Day Installation Challenge

  - by james.bayer

  It’s a really exciting time for the extended WebLogic community as we are enjoying seeing the impressive results of Exalogic deployments.  At Oracle Open World, a lot of people I spoke with came away impressed with the raw performance.  However, Exalogic offers a lot more than just raw performance.  I had the pleasure of working with Ram Sivaram during one of the Exalogic training sessions in Santa Clara.  In this video diary, he shows the Exalogic machine arrive on the shipping dock, get unpacked, wired up, powered on, configured, and installed with a WebLogic Server cluster in just about 10 hours.  I’ve worked with customers in the past that have taken several weeks or longer to get an environment ready after the hardware arrives.  This typically involves many different specialized teams in their organization.  Mohamad Afshar just wrote a great explanation of the benefit of Engineered Systems and contrasting that to the status quo.  Being able to streamline deployment of middleware capacity will have a lot of value for customers shortening time to deployment.  Thanks for the video Ram, you’ve set a high bar, we’ll see if anyone can top your time!  

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• How can I uniqely record every new command I use, and possibly timestamp it?

  - by Nirmik

  I've been on Linux for more than 6 months now but never went too much into the CLI (command-line interface or terminal or shell) Now as I ask questions here, get answers, or help from other sites, I learn new commands... How can I can store every new command in a text file? Only new/*unique* commands, not repetitions of the same command. Here's an example: In the terminal, I enter the commands like this- ubuntu@ubuntu:~$ *command1* ubuntu@ubuntu:~$ *command2* ubuntu@ubuntu:~$ *command3* ubuntu@ubuntu:~$ *command4* ubuntu@ubuntu:~$ *command1* Now, these commands should get saved in a text file say commandrec like this- *command1* *command2* *command3* *command4* NOTE:The last command in the terminal which was again command1 is not recorded/saved again in the text file. And the next time I open the terminal, and enter a new command command 5, it should get appended to the list in commandrec (but if the command was used earlier on some other date, it should still be ignored. For example, command 1 entered again along with command 5 on a new day/time but command1 not recorded as already used) The commandrec file looking something like this- 31/05/12 12:00:00 *command1* *command2* *command3* *command4* 01/06/12 13:00:00 *command 5* (the time and date thing would be great if possible, but okay even if that isn't there) This way, I can have a record of all commands used by me to date. How can this be done?

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• Adding dynamic business logic/business process checks to a system

  - by Jordan Reiter

  I'm wondering if there is a good extant pattern (language here is Python/Django but also interested on the more abstract level) for creating a business logic layer that can be created without coding. For example, suppose that a house rental should only be available during a specific time. A coder might create the following class: from bizlogic import rules, LogicRule from orders.models import Order class BeachHouseAvailable(LogicRule): def check(self, reservation): house = reservation.house_reserved if not (house.earliest_available < reservation.starts < house.latest_available ) raise RuleViolationWhen("Beach house is available only between %s and %s" % (house.earliest_available, house.latest_available)) return True rules.add(Order, BeachHouseAvailable, name="BeachHouse Available") This is fine, but I don't want to have to code something like this each time a new rule is needed. I'd like to create something dynamic, ideally something that can be stored in a database. The thing is, it would have to be flexible enough to encompass a wide variety of rules: avoiding duplicates/overlaps (to continue the example "You already have a reservation for this time/location") logic rules ("You can't rent a house to yourself", "This house is in a different place from your chosen destination") sanity tests ("You've set a rental price that's 10x the normal rate. Are you sure this is the right price?" Things like that. Before I recreate the wheel, I'm wondering if there are already methods out there for doing something like this.

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• Problem with WCF-SQL Adapter

  - by Paul Petrov

  When using WCF receive adapter with SQL binding in Polling mode please be aware of the following problem. Problem: At some regular but seemingly random intervals the application stops processing new requests, places a lock on the database and prevent other application from accessing it. Initially it looked like DTC issue, as it was distributed transaction that stalled most of the time. Symptoms: Orchestration instances in Dehydrated state, receive location not picking up new messages, exclusive locks on database tables, errors in DTC trace. Cause: Microsoft has confirmed that there is a bug in the WCF-SQL adapter. In the receive adapter binding configuration there's receiveTimeout property set to 10 minutes by default. If during this period data is not found in the table the adapter would start new thread and allocate more memory without releasing old resources. Thus if there's no new data in the table for a long time a new thread will be created in the host instance every 10 minutes until it reaches threshold (1000) and then there's no threads left for this host instance and it can't start/complete any tasks. Then this host instance won't be able to do anything. If other artifacts are hosted in the instance they will suffer consequences as well. Solution: - Set receiveTimeout to the maximum time 24.20:31:23.6470000. - Place WCF-SQL receive locations in separate host to provide its own thread pool and eliminate impact on other processes - Ensure WCF-SQL dedicated host instances are restarted at interval less or equal to receiveTimeout to flush threads and memory - Monitor performance counters Process/Thread Count/BTSNTSvc{n} for thread count trend and respond to alert if it grows by restarting host instance If you use WCF-SQL Adapter in the Notification mode then make sure to remove sqlAdapterInboundTransactionBehavior otherwise this location will exhibit the same issue. In this case though, setting receiveTimeout doesn't help and new thread will be created at default intervals (10 min) ignoring maximum setting.

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• Instructor Insight: Using the Container Database in Oracle Database 12 c

  - by Breanne Cooley

  The first time I examined the Oracle Database 12c architecture, I wasn’t quite sure what I thought about the Container Database (CDB). In the current release of the Oracle RDBMS, the administrator now has a choice of whether or not to employ a CDB. Bundling Databases Inside One Container In today’s IT industry, consolidation is a common challenge. With potentially hundreds of databases to manage and maintain, an administrator will require a great deal of time and resources to upgrade and patch software. Why not consider deploying a container database to streamline this activity? By “bundling” several databases together inside one container, in the form of a pluggable database, we can save on overhead process resources and CPU time. Furthermore, we can reduce the human effort required for periodically patching and maintaining the software. Minimizing Storage Most IT professionals understand the concept of storage, as in solid state or non-rotating. Let’s take one-to-many databases and “plug” them into ONE designated container database. We can minimize many redundant pieces that would otherwise require separate storage and architecture, as was the case in previous releases of the Oracle RDBMS. The data dictionary can be housed and shared in one CDB, with individual metadata content for each pluggable database. We also won’t need as many background processes either, thus reducing the overhead cost of the CPU resource. Improve Security Levels within Each Pluggable Database  We can now segregate the CDB-administrator role from that of the pluggable-database administrator as well, achieving improved security levels within each pluggable database and within the CDB. And if the administrator chooses to use the non-CDB architecture, everything is backwards compatible, too.  The bottom line: it's a good idea to at least consider using a CDB. -Christopher Andrews, Senior Principal Instructor, Oracle University

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• Partner Webcast - Oracle SOA Suite 12c: Connect 4 Cloud, Mobile, IoT with On-premise

  - by Thanos Terentes Printzios

  The pace of new business projects continues to grow from increasing customer self-service to seamlessly connecting all your back office and in-the-field applications. At the same time increased integration complexity may seem inevitable as organizations are suddenly faced with the requirement to support three new integration challenges:  » Cloud Integration - integrate with the cloud, rapidly integrate a growing list of cloud applications with existing applications » Mobile Integration - the urgency to mobile-enable existing applications » IoT Integration - begin development on the latest trend of connecting Internet of Things (IoT) devices to your existing infrastructure. Oracle SOA Suite 12c, the latest version of the industry’s most complete and unified application integration and SOA solution, aims to simplify, accelerate and optimize integrations. Oracle SOA Suite 12c and its associated products, Oracle Managed File Transfer, Oracle Cloud and Application Adapters, B2B and healthcare integration, offer the industry’s most highly integrated platform for solving the increased integration challenges. Oracle SOA Suite 12c is a complete, integrated and best-of-breed platform. It enables next generation integration capabilities through: · A unified toolset for the development of services and composite applications.· A standards-based platform that is service enabled and easily consumable by modern web applications, allowing enterprises to quickly and easily adapt to changes in their business and IT environments.· Greater visibility, controls and analytics to govern how services and processes are deployed, reused and changed across their entire lifecycle. Join us to find out more about the new features of Oracle SOA Suite 12c and how it enables you to reduce time to market for new project integration and to reduce integration cost and complexity. Oracle SOA Suite is the ability to simplify by integrating the disparate requirements of cloud, mobile, and IoT devices with existing on-premise applications. Agenda: Oracle SOA Suite 12c new Features Cloud Integration Mobile Enablement Internet of Things (IoT) Summary - Q&A Delivery Format This FREE online LIVE eSeminar will be delivered over the Web. Registrations received less than 24hours prior to start time may not receive confirmation to attend. Presenter: Heba Fouad – FMW Specialist, Technology Adoption, ECEMEA Partner Business Development Date: Thursday, August 28th, 10pm CEST (8am UTC/11am EEST)Duration: 1 hour Register Here For any questions please contact us at partner.imc-AT-beehiveonline.oracle-DOT-com

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• high performance with xen, vmware or virtualbox

  - by Marchosius

  I was wondering which is the best method to go about if I want to play win based games. I do not want to go with the dual boot method as this will cost me time to restart, login and run a os to do my work or pass the time, and some of my apps rely on win and my graphics to run. for example Daz3d, Photoshop, Flash etc. Now I read about HVM(hardware virtual machines) and then I know about the 3D virtualisation of VMware and VirtualBox. How ever the 2 later virtualise the 3D not using the full power of the GPU. So this option wont perform perfect for latest games like D3. I was wondering if anyone have experience in HVM(like xen if i am not mistaken) and tried something similar to access the full power of the GPU and successfully run newer games and other products relying on the GPU? Will be the first time setting up a HVM, no experience in this so don't know what to expect. This will help a lot as I do not want to revert back to win or as mentioned do dual boot.

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• Integrating different branches from external sources into a single Mercurial repository

  - by dukeofgaming

  I'm currently working in a company using Perforce and am making way for distributed version control with Mercurial. I've had success importing Perforce history using the perfarce (quite a suitable name, I laugh every time I see/say it) however, this only works with a single branch at a time. Here's how my P4 integration setup works: In perforce, create a "client", which is kind of a description of what you will be constantly updating/checking-out. This can only address one branch at a time (trunk or other). Once you do this, run hg clone p4://<server>/<client_name> Go to .hg/hgrc and put the perforce path line: perforce = p4://<server>/<client_name> Work normally with the code under mercurial, do hg pull perforce to sync up, hg push to export a changelist What I'd like to be able to do is have a perforce path per branch and have everything work in the same repository. Now, pushing is not a problem, however, if I pull the history from another branch it would end up at the default branch. I'd like to be able to do something like hg pull perforce-R5 and have it land in mercurial's R5 branch. Even if I have no merging history, it would be sweet enough to be able to preserve it. There are also other plugins for CVCSs that let you integrate mercurial, but AFAIK the subversion one has the same problem. I don't think there is a straight-through way of doing this, but as long as I could automate the process with some hooks and scripts in a single Mercurial machine, that would be good enough.

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• Questioning pythonic type checking

  - by Pace

  I've seen countless times the following approach suggested for "taking in a collection of objects and doing X if X is a Y and ignoring the object otherwise" def quackAllDucks(ducks): for duck in ducks: try: duck.quack("QUACK") except AttributeError: #Not a duck, can't quack, don't worry about it pass The alternative implementation below always gets flak for the performance hit caused by type checking def quackAllDucks(ducks): for duck in ducks: if hasattr(duck,"quack"): duck.quack("QUACK") However, it seems to me that in 99% of scenarios you would want to use the second solution because of the following: If the user gets the parameters wrong then they will not be treated like a duck and there will be no indication. A lot of time will be wasted debugging why there is no quacking going on until the user finally realizes his silly mistake. The second solution would throw a stack trace as soon the user tried to quack. If the user has any bugs in their quack() method which cause an AttributeError then those bugs will be silently swallowed. Once again time will be wasted digging for the bug when the second solution would simply give a stack trace showing the immediate issue. In fact, it seems to me that the only time you would ever want to use the first method is when: The block of code in question is in an extremely performance critical section of your application. Following the principal of "avoid premature optimization" you would only realize this of course, after you had implemented the safer approach and found it to be a bottleneck. There are many types of quacking objects out there and you are only interested in quacking objects that quack with a very specific set of arguments (this seems to be a very rare case to me). Given this, why is it that so many people prefer the first approach over the second approach? What is it that I am missing? Also, I realize there are other solutions (such as using abcs) but these are the two solutions I seem to see most often for the basic case.

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• Windows being placed on wrong monitor

  - by osarusan

  I'm running a fresh install of Ubuntu 12.04x64 (ATI Radeon HD4770 with open source drivers) and I am having trouble getting windows to appear on the right screen. Yesterday I plugged in my secondary monitor and it worked perfectly out of the box, except that for some reason, compiz wants to place windows on the secondary monitor rather than the first. This is a problem because I don't use the secondary monitor 100% of the time, and I don't want windows being placed on it when it is off. Also, it's only some windows that are getting placed there. For example, the "Edit Connections" window from the networking menu is always placed off my primary screen. There are a number of other windows that do the same. While some, like nautilus, always appear on the proper monitor. I played around with Compiz Config Settings Manager and found that if I disable the "Place Windows" plugin, all of the windows appear on the proper monitor -- except that they are placed underneath the Unity Panel, so I have to alt-drag them out each time in order to use them. With out without that plugin, I can't seem to get a sensible setup. The windows are supposed to appear only on the active display, but for some reason Compiz doesn't want to do that with some windows. Does anyone know a fix for this? I'd rather not have to disable and re-enable my monitor every single time I use it...

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• Am I wrong to disagree with A Gentle Introduction to symfony's template best practices?

  - by AndrewKS

  I am currently learning symfony and going through the book A Gentle Introduction to symfony and came across this section in "Chapter 4: The Basics of Page Creation" on creating templates (or views): "If you need to execute some PHP code in the template, you should avoid using the usual PHP syntax, as shown in Listing 4-4. Instead, write your templates using the PHP alternative syntax, as shown in Listing 4-5, to keep the code understandable for non-PHP programmers." Listing 4-4 - The Usual PHP Syntax, Good for Actions, But Bad for Templates <p>Hello, world!</p> <?php if ($test) { echo "<p>".time()."</p>"; } ?> (The ironic thing about this is that echo statement would look even better if time was variable declared in the controller, because then you could just embed the variable in the string instead of concatenating) Listing 4-5 - The Alternative PHP Syntax, Good for Templates <p>Hello, world!</p> <?php if ($test): ?> <p><?php echo time(); ?> </p><?php endif; ?> I fail to see how listing 4-5 makes the code "understandable for non-PHP programmers", and its readability is shaky at best. 4-4 looks much more readable to me. Are there any programmers who are using symfony that write their templates like those in 4-4 rather than 4-5? Are there reasons I should use one over the other? There is the very slim chance that somewhere down the road someone less technical could be editing it the template, but how does 4-5 actually make it more understandable to them?

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• Code Generation and IDE vs writing per Hand

  - by sytycs

  I have been programming for about a year now. Pretty soon I realized that I need a great Tool for writing code and learned Vim. I was happy with C and Ruby and never liked the idea of an IDE. Which was encouraged by a lot of reading about programming.[1] However I started with (my first) Java Project. In a CS Course we were using Visual Paradigm and encouraged to let the program generate our code from a class diagram. I did not like that Idea because: Our class diagram was buggy. Students more experienced in Java said they would write the code per hand. I had never written any Java before and would not understand a lot of the generated code. So I took a different approach and wrote all methods per Hand (getter and Setter included). My Team-members have written their parts (partly generated by VP) in an IDE and I was "forced" to use it too. I realized they had generated equal amounts of code in a shorter amount of time and did not spend a lot of time setting their CLASSPATH and writing scripts for compiling that son of a b***. Additionally we had to implement a GUI and I dont see how we could have done that in a sane matter in Vim. So here is my Problem: I fell in love with Vim and the Unix way. But it looks like for getting this job done (on time) the IDE/Code generation approach is superior. Do you have equal experiences? Is Java by the nature of the language just more suitable for an IDE/Code generated approach? Or am I lacking the knowledge to produce equal amounts of code "per Hand"? [1] http://heather.cs.ucdavis.edu/~matloff/eclipse.html

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• Problem with signal handlers being called too many times [closed]

  - by Hristo

  how can something print 3 times when it only goes the printing code twice? I'm coding in C and the code is in a SIGCHLD signal handler I created. void chld_signalHandler() { int pidadf = (int) getpid(); printf("pidafdfaddf: %d\n", pidadf); while (1) { int termChildPID = waitpid(-1, NULL, WNOHANG); if (termChildPID == 0 || termChildPID == -1) { break; } dll_node_t *temp = head; while (temp != NULL) { printf("stuff\n"); if (temp->pid == termChildPID && temp->type == WORK) { printf("inside if\n"); // read memory mapped file b/w WORKER and MAIN // get statistics and write results to pipe char resultString[256]; // printing TIME int i; for (i = 0; i < 24; i++) { sprintf(resultString, "TIME; %d ; %d ; %d ; %s\n",i,1,2,temp->stats->mboxFileName); fwrite(resultString, strlen(resultString), 1, pipeFD); } remove_node(temp); break; } temp = temp->next; } printf("done printing from sigchld \n"); } return; } the output for my MAIN process is this: MAIN PROCESS 16214 created WORKER PROCESS 16220 for file class.sp10.cs241.mbox pidafdfaddf: 16214 stuff stuff inside if done printing from sigchld MAIN PROCESS 16214 created WORKER PROCESS 16221 for file class.sp10.cs225.mbox pidafdfaddf: 16214 stuff stuff inside if done printing from sigchld and the output for the MONITOR process is this: MONITOR: pipe is open for reading MONITOR PIPE: TIME; 0 ; 1 ; 2 ; class.sp10.cs225.mbox MONITOR PIPE: TIME; 0 ; 1 ; 2 ; class.sp10.cs225.mbox MONITOR PIPE: TIME; 0 ; 1 ; 2 ; class.sp10.cs241.mbox MONITOR: end of readpipe ( I've taken out repeating lines so I don't take up so much space ) Thanks, Hristo

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• Devoxx UK JCP & Adopt-a-JSR activities

  - by Heather VanCura

  Devoxx UK starts this week!  The JCP Program is organizing many activities throughout the conference, including some tables in the Hackergarten area on 12-13 June.  Topics include Java EE, Data Grids, Java SE 8 (Lambdas and Date & Time API), Money & Currency API and OpenJDK.  We will have two book signings by Richard Warburton and Peter Pilgrim during the Hackergarten - free signed copy of their books at these times - first come, first served (limited quantities available).  Thursday night is the party and the Birds of a Feather (BoF) sessions - come with your favorite questions and topics related to the JCP, Adopt-a-JSR and Adopt OpenJDK Programs!  See below for the schedule of activities; I will fill in details for each session tomorrow.    Thursday 12 June 10:20 - 12:50 Java EE -- Arun Gupta 13:30-17:00 Lambdas/Date & Time API --Richard Warburton & Raoul-Gabriel Urma (also a book signing with Richard Warburon during the afternoon break) 14:30-17:30 Data Grids - Peter Lawrey 14:30-18:00 Money & Currency -- Anatole Tresch 18:45 Adopt OpenJDK BoF session (Java EE BoF runs concurrently) 19:45 JCP & Adopt-a-JSR BoF session Friday 13 June 10:20-13:00 OpenJDK -- Mani Sarkar  10:20- 14:30 Money & Currency -- Anatole Tresch 10:20 - 13:00 Java EE -- Peter Pilgrim 13:00-13:30 Peter Pilgrim Java EE 7 Book signing sponsored by JCP @ lunch time 13:30 - 15:30 JCP.Next/JSR 364 -- Heather VanCura

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• Table Variables: an empirical approach.

  - by Phil Factor

  It isn’t entirely a pleasant experience to publish an article only to have it described on Twitter as ‘Horrible’, and to have it criticized on the MVP forum. When this happened to me in the aftermath of publishing my article on Temporary tables recently, I was taken aback, because these critics were experts whose views I respect. What was my crime? It was, I think, to suggest that, despite the obvious quirks, it was best to use Table Variables as a first choice, and to use local Temporary Tables if you hit problems due to these quirks, or if you were doing complex joins using a large number of rows. What are these quirks? Well, table variables have advantages if they are used sensibly, but this requires some awareness by the developer about the potential hazards and how to avoid them. You can be hit by a badly-performing join involving a table variable. Table Variables are a compromise, and this compromise doesn’t always work out well. Explicit indexes aren’t allowed on Table Variables, so one cannot use covering indexes or non-unique indexes. The query optimizer has to make assumptions about the data rather than using column distribution statistics when a table variable is involved in a join, because there aren’t any column-based distribution statistics on a table variable. It assumes a reasonably even distribution of data, and is likely to have little idea of the number of rows in the table variables that are involved in queries. However complex the heuristics that are used might be in determining the best way of executing a SQL query, and they most certainly are, the Query Optimizer is likely to fail occasionally with table variables, under certain circumstances, and produce a Query Execution Plan that is frightful. The experienced developer or DBA will be on the lookout for this sort of problem. In this blog, I’ll be expanding on some of the tests I used when writing my article to illustrate the quirks, and include a subsequent example supplied by Kevin Boles. A simplified example. We’ll start out by illustrating a simple example that shows some of these characteristics. We’ll create two tables filled with random numbers and then see how many matches we get between the two tables. We’ll forget indexes altogether for this example, and use heaps. We’ll try the same Join with two table variables, two table variables with OPTION (RECOMPILE) in the JOIN clause, and with two temporary tables. It is all a bit jerky because of the granularity of the timing that isn’t actually happening at the millisecond level (I used DATETIME). However, you’ll see that the table variable is outperforming the local temporary table up to 10,000 rows. Actually, even without a use of the OPTION (RECOMPILE) hint, it is doing well. What happens when your table size increases? The table variable is, from around 30,000 rows, locked into a very bad execution plan unless you use OPTION (RECOMPILE) to provide the Query Analyser with a decent estimation of the size of the table. However, if it has the OPTION (RECOMPILE), then it is smokin’. Well, up to 120,000 rows, at least. It is performing better than a Temporary table, and in a good linear fashion. What about mixed table joins, where you are joining a temporary table to a table variable? You’d probably expect that the query analyzer would throw up its hands and produce a bad execution plan as if it were a table variable. After all, it knows nothing about the statistics in one of the tables so how could it do any better? Well, it behaves as if it were doing a recompile. And an explicit recompile adds no value at all. (we just go up to 45000 rows since we know the bigger picture now)   Now, if you were new to this, you might be tempted to start drawing conclusions. Beware! We’re dealing with a very complex beast: the Query Optimizer. It can come up with surprises What if we change the query very slightly to insert the results into a Table Variable? We change nothing else and just measure the execution time of the statement as before. Suddenly, the table variable isn’t looking so much better, even taking into account the time involved in doing the table insert. OK, if you haven’t used OPTION (RECOMPILE) then you’re toast. Otherwise, there isn’t much in it between the Table variable and the temporary table. The table variable is faster up to 8000 rows and then not much in it up to 100,000 rows. Past the 8000 row mark, we’ve lost the advantage of the table variable’s speed. Any general rule you may be formulating has just gone for a walk. What we can conclude from this experiment is that if you join two table variables, and can’t use constraints, you’re going to need that Option (RECOMPILE) hint. Count Dracula and the Horror Join. These tables of integers provide a rather unreal example, so let’s try a rather different example, and get stuck into some implicit indexing, by using constraints. What unusual words are contained in the book ‘Dracula’ by Bram Stoker? Here we get a table of all the common words in the English language (60,387 of them) and put them in a table. We put them in a Table Variable with the word as a primary key, a Table Variable Heap and a Table Variable with a primary key. We then take all the distinct words used in the book ‘Dracula’ (7,558 of them). We then create a table variable and insert into it all those uncommon words that are in ‘Dracula’. i.e. all the words in Dracula that aren’t matched in the list of common words. To do this we use a left outer join, where the right-hand value is null. The results show a huge variation, between the sublime and the gorblimey. If both tables contain a Primary Key on the columns we join on, and both are Table Variables, it took 33 Ms. If one table contains a Primary Key, and the other is a heap, and both are Table Variables, it took 46 Ms. If both Table Variables use a unique constraint, then the query takes 36 Ms. If neither table contains a Primary Key and both are Table Variables, it took 116383 Ms. Yes, nearly two minutes!! If both tables contain a Primary Key, one is a Table Variables and the other is a temporary table, it took 113 Ms. If one table contains a Primary Key, and both are Temporary Tables, it took 56 Ms.If both tables are temporary tables and both have primary keys, it took 46 Ms. Here we see table variables which are joined on their primary key again enjoying a  slight performance advantage over temporary tables. Where both tables are table variables and both are heaps, the query suddenly takes nearly two minutes! So what if you have two heaps and you use option Recompile? If you take the rogue query and add the hint, then suddenly, the query drops its time down to 76 Ms. If you add unique indexes, then you've done even better, down to half that time. Here are the text execution plans.So where have we got to? Without drilling down into the minutiae of the execution plans we can begin to create a hypothesis. If you are using table variables, and your tables are relatively small, they are faster than temporary tables, but as the number of rows increases you need to do one of two things: either you need to have a primary key on the column you are using to join on, or else you need to use option (RECOMPILE) If you try to execute a query that is a join, and both tables are table variable heaps, you are asking for trouble, well- slow queries, unless you give the table hint once the number of rows has risen past a point (30,000 in our first example, but this varies considerably according to context). Kevin’s Skew In describing the table-size, I used the term ‘relatively small’. Kevin Boles produced an interesting case where a single-row table variable produces a very poor execution plan when joined to a very, very skewed table. In the original, pasted into my article as a comment, a column consisted of 100000 rows in which the key column was one number (1) . To this was added eight rows with sequential numbers up to 9. When this was joined to a single-tow Table Variable with a key of 2 it produced a bad plan. This problem is unlikely to occur in real usage, and the Query Optimiser team probably never set up a test for it. Actually, the skew can be slightly less extreme than Kevin made it. The following test showed that once the table had 54 sequential rows in the table, then it adopted exactly the same execution plan as for the temporary table and then all was well. Undeniably, real data does occasionally cause problems to the performance of joins in Table Variables due to the extreme skew of the distribution. We've all experienced Perfectly Poisonous Table Variables in real live data. As in Kevin’s example, indexes merely make matters worse, and the OPTION (RECOMPILE) trick does nothing to help. In this case, there is no option but to use a temporary table. However, one has to note that once the slight de-skew had taken place, then the plans were identical across a huge range. Conclusions Where you need to hold intermediate results as part of a process, Table Variables offer a good alternative to temporary tables when used wisely. They can perform faster than a temporary table when the number of rows is not great. For some processing with huge tables, they can perform well when only a clustered index is required, and when the nature of the processing makes an index seek very effective. Table Variables are scoped to the batch or procedure and are unlikely to hang about in the TempDB when they are no longer required. They require no explicit cleanup. Where the number of rows in the table is moderate, you can even use them in joins as ‘Heaps’, unindexed. Beware, however, since, as the number of rows increase, joins on Table Variable heaps can easily become saddled by very poor execution plans, and this must be cured either by adding constraints (UNIQUE or PRIMARY KEY) or by adding the OPTION (RECOMPILE) hint if this is impossible. Occasionally, the way that the data is distributed prevents the efficient use of Table Variables, and this will require using a temporary table instead. Tables Variables require some awareness by the developer about the potential hazards and how to avoid them. If you are not prepared to do any performance monitoring of your code or fine-tuning, and just want to pummel out stuff that ‘just runs’ without considering namby-pamby stuff such as indexes, then stick to Temporary tables. If you are likely to slosh about large numbers of rows in temporary tables without considering the niceties of processing just what is required and no more, then temporary tables provide a safer and less fragile means-to-an-end for you.

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