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  • Implementing User-Defined Hierarchies in SQL Server Analysis Services

    To be able to drill into multidimensional cube data at several levels, you must implement all of the hierarchies on the database dimensions. Then you'll create the attribute relationships necessary to optimize performance. Analysis Services hierarchies offer plenty of possibilities for displaying the data that your business requires. Rob Sheldon continues his series on SQL Server Analysis Services 2008.

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  • New Wine in New Bottles

    - by Tony Davis
    How many people, when their car shows signs of wear and tear, would consider upgrading the engine and keeping the shell? Even if you're cash-strapped, you'll soon work out the subtlety of the economics, the cost of sudden breakdowns, the precious time lost coping with the hassle, and the low 'book value'. You'll generally buy a new car. The same philosophy should apply to database systems. Mainstream support for SQL Server 2005 ends on April 12; many DBAS, if they haven't done so already, will be considering the migration to SQL Server 2008 R2. Hopefully, that upgrade plan will include a fresh install of the operating system on brand new hardware. SQL Server 2008 R2 and Windows Server 2008 R2 are designed to work together. The improved architecture, processing power, and hyper-threading capabilities of modern processors will dramatically improve the performance of many SQL Server workloads, and allow consolidation opportunities. Of course, there will be many DBAs smiling ruefully at the suggestion of such indulgence. This is nothing like the real world, this halcyon place where hardware and software budgets are limitless, development and testing resources are plentiful, and third party vendors immediately certify their applications for the latest-and-greatest platform! As with cars, or any other technology, the justification for a complete upgrade is complex. With Servers, the extra cost at time of upgrade will generally pay you back in terms of the increased performance of your business applications, reduced maintenance costs, training costs and downtime. Also, if you plan and design carefully, it's possible to offset hardware costs with reduced SQL Server licence costs. In his forthcoming SQL Server Hardware book, Glenn Berry describes a recent case where he was able to replace 4 single-socket database servers with one two-socket server, saving about $90K in hardware costs and $350K in SQL Server license costs. Of course, there are exceptions. If you do have a stable, reliable, secure SQL Server 6.5 system that still admirably meets the needs of a specific business requirement, and has no security vulnerabilities, then by all means leave it alone. Why upgrade just for the sake of it? However, as soon as a system shows sign of being unfit for purpose, or is moving out of mainstream support, the ruthless DBA will make the strongest possible case for a belts-and-braces upgrade. We'd love to hear what you think. What does your typical upgrade path look like? What are the major obstacles? Cheers, Tony.

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  • Finance: Friends, not foes!

    - by red@work
    After reading Phil's blog post about his experiences of working on reception, I thought I would let everyone in on one of the other customer facing roles at Red Gate... When you think of a Credit Control team, most might imagine money-hungry (and often impolite) people, who will do nothing short of hunting people down until they pay up. Well, as with so many things, not at Red Gate! Here we do things a little bit differently.   Since joining the Licensing, Invoicing and Credit Control team at Red Gate (affectionately nicknamed LICC!), I have found it fantastic to work with people who know that often the best way to get what you want is by being friendly, reasonable and as helpful as possible. The best bit about this is that, because everyone is in a good mood, we have a great working atmosphere! We are definitely a very happy team. We laugh a lot, even when dealing with the serious matter of playing table football after lunch. The most obvious part of my job is bringing in money. There are few things quite as satisfying as receiving a big payment or one that you've been chasing for a long time. That being said, it's just as nice to encounter the companies that surprise you with a payment bang on time after little or no chasing. It's always a pleasure to find these people who are generous and easy to work with, and so they always make me smile, too. As I'm in one of the few customer facing roles here, I get to experience firsthand just how much Red Gate customers love our software and are equally impressed with our customer service. We regularly get replies from people thanking us for our help in resolving a problem or just to simply say that they think we're great. Or, as is often the case, that we 'rock and are awesome'! When those are the kinds of emails you have to deal with for most of the day, I would challenge anyone to be unhappy! The best thing about my work is that, much like Phil and his counterparts on reception, I get to talk to people from all over the world, and experience their unique (and occasionally unusual) personality traits. I deal predominantly with customers in the US, so I'll be speaking to someone from a high flying multi-national in New York one minute, and then the next phone call will be to a small office on the outskirts of Alabama. This level of customer involvement has led to a lot of interesting anecdotes and plenty of in-jokes to keep us amused! Obviously there are customers who are infuriating, like those who simply tell us that they will pay "one day", and that we should stop chasing them. Then there are the people who say that they ordered the tools because they really like them, but they just can't afford to actually pay for them at the moment. Thankfully these situations are relatively few and far between, and for every one customer that makes you want to scream, there are far, far more that make you smile!

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  • .NET Reflector Pro to the rescue

    Almost all applications have to interface with components or modules written by somebody else, for which you don't have the source code. This is fine until things go wrong, but when you need to refactor your code and you keep getting strange exceptions, you'll start to wish you could place breakpoints in someone else's code and step through it. Now, of course, you can, as Geoffrey Braaf discovered.

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  • Why you shouldn't add methods to interfaces in APIs

    - by Simon Cooper
    It is an oft-repeated maxim that you shouldn't add methods to a publically-released interface in an API. Recently, I was hit hard when this wasn't followed. As part of the work on ApplicationMetrics, I've been implementing auto-reporting of MVC action methods; whenever an action was called on a controller, ApplicationMetrics would automatically report it without the developer needing to add manual ReportEvent calls. Fortunately, MVC provides easy hook when a controller is created, letting me log when it happens - the IControllerFactory interface. Now, the dll we provide to instrument an MVC webapp has to be compiled against .NET 3.5 and MVC 1, as the lowest common denominator. This MVC 1 dll will still work when used in an MVC 2, 3 or 4 webapp because all MVC 2+ webapps have a binding redirect redirecting all references to previous versions of System.Web.Mvc to the correct version, and type forwards taking care of any moved types in the new assemblies. Or at least, it should. IControllerFactory In MVC 1 and 2, IControllerFactory was defined as follows: public interface IControllerFactory { IController CreateController(RequestContext requestContext, string controllerName); void ReleaseController(IController controller); } So, to implement the logging controller factory, we simply wrap the existing controller factory: internal sealed class LoggingControllerFactory : IControllerFactory { private readonly IControllerFactory m_CurrentController; public LoggingControllerFactory(IControllerFactory currentController) { m_CurrentController = currentController; } public IController CreateController( RequestContext requestContext, string controllerName) { // log the controller being used FeatureSessionData.ReportEvent("Controller used:", controllerName); return m_CurrentController.CreateController(requestContext, controllerName); } public void ReleaseController(IController controller) { m_CurrentController.ReleaseController(controller); } } Easy. This works as expected in MVC 1 and 2. However, in MVC 3 this type was throwing a TypeLoadException, saying a method wasn't implemented. It turns out that, in MVC 3, the definition of IControllerFactory was changed to this: public interface IControllerFactory { IController CreateController(RequestContext requestContext, string controllerName); SessionStateBehavior GetControllerSessionBehavior( RequestContext requestContext, string controllerName); void ReleaseController(IController controller); } There's a new method in the interface. So when our MVC 1 dll was redirected to reference System.Web.Mvc v3, LoggingControllerFactory tried to implement version 3 of IControllerFactory, was missing the GetControllerSessionBehaviour method, and so couldn't be loaded by the CLR. Implementing the new method Fortunately, there was a workaround. Because interface methods are normally implemented implicitly in the CLR, if we simply declare a virtual method matching the signature of the new method in MVC 3, then it will be ignored in MVC 1 and 2 and implement the extra method in MVC 3: internal sealed class LoggingControllerFactory : IControllerFactory { ... public virtual SessionStateBehaviour GetControllerSessionBehaviour( RequestContext requestContext, string controllerName) {} ... } However, this also has problems - the SessionStateBehaviour type only exists in .NET 4, and we're limited to .NET 3.5 by support for MVC 1 and 2. This means that the only solutions to support all MVC versions are: Construct the LoggingControllerFactory type at runtime using reflection Produce entirely separate dlls for MVC 1&2 and MVC 3. Ugh. And all because of that blasted extra method! Another solution? Fortunately, in this case, there is a third option - System.Web.Mvc also provides a DefaultControllerFactory type that can provide the implementation of GetControllerSessionBehaviour for us in MVC 3, while still allowing us to override CreateController and ReleaseController. However, this does mean that LoggingControllerFactory won't be able to wrap any calls to GetControllerSessionBehaviour. This is an acceptable bug, given the other options, as very few developers will be overriding GetControllerSessionBehaviour in their own custom controller factory. So, if you're providing an interface as part of an API, then please please please don't add methods to it. Especially if you don't provide a 'default' implementing type. Any code compiled against the previous version that can't be updated will have some very tough decisions to make to support both versions.

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  • Generate a merge statement from table structure

    - by Nigel Rivett
    This code generates a merge statement joining on he natural key and checking all other columns to see if they have changed. The full version deals with type 2 processing and an audit trail but this version is useful. Just the insert or update part is handy too. Change the table at the top (spt_values in master in the version) and the join columns for the merge in @nk. The output generated is at the top and the code to run to generate it below. Output merge spt_values a using spt_values b on a.name = b.name and a.number = b.number and a.type = b.type when matched and (1=0 or (a.low b.low) or (a.low is null and b.low is not null) or (a.low is not null and b.low is null) or (a.high b.high) or (a.high is null and b.high is not null) or (a.high is not null and b.high is null) or (a.status b.status) or (a.status is null and b.status is not null) or (a.status is not null and b.status is null) ) then update set low = b.low , high = b.high , status = b.status when not matched by target then insert ( name , number , type , low , high , status ) values ( b.name , b.number , b.type , b.low , b.high , b.status ); Generator set nocount on declare @t varchar(128) = 'spt_values' declare @i int = 0 -- this is the natural key on the table used for the merge statement join declare @nk table (ColName varchar(128)) insert @nk select 'Number' insert @nk select 'Name' insert @nk select 'Type' declare @cols table (seq int, nkseq int, type int, colname varchar(128)) ;with cte as ( select ordinal_position, type = case when columnproperty(object_id(@t), COLUMN_NAME,'IsIdentity') = 1 then 3 when nk.ColName is not null then 1 else 0 end, COLUMN_NAME from information_schema.columns c left join @nk nk on c.column_name = nk.ColName where table_name = @t ) insert @cols (seq, nkseq, type, colname) select ordinal_position, row_number() over (partition by type order by ordinal_position) , type, COLUMN_NAME from cte declare @result table (i int, j int, k int, data varchar(500)) select @i = @i + 1 insert @result (i, data) select @i, 'merge ' + @t + ' a' select @i = @i + 1 insert @result (i, data) select @i, ' using cte b' select @i = @i + 1 insert @result (i, j, data) select @i, nkseq, ' ' + case when nkseq = 1 then 'on' else 'and' end + ' a.' + ColName + ' = b.' + ColName from @cols where type = 1 select @i = @i + 1 insert @result (i, data) select @i, ' when matched and (1=0' select @i = @i + 1 insert @result (i, j, k, data) select @i, seq, 1, ' or (a.' + ColName + ' b.' + ColName + ')' + ' or (a.' + ColName + ' is null and b.' + ColName + ' is not null)' + ' or (a.' + ColName + ' is not null and b.' + ColName + ' is null)' from @cols where type 1 select @i = @i + 1 insert @result (i, data) select @i, ' )' select @i = @i + 1 insert @result (i, data) select @i, ' then update set' select @i = @i + 1 insert @result (i, j, data) select @i, nkseq, ' ' + case when nkseq = 1 then ' ' else ', ' end + colname + ' = b.' + colname from @cols where type = 0 select @i = @i + 1 insert @result (i, data) select @i, ' when not matched by target then insert' select @i = @i + 1 insert @result (i, data) select @i, ' (' select @i = @i + 1 insert @result (i, j, data) select @i, seq, ' ' + case when seq = 1 then ' ' else ', ' end + colname from @cols where type 3 select @i = @i + 1 insert @result (i, data) select @i, ' )' select @i = @i + 1 insert @result (i, data) select @i, ' values' select @i = @i + 1 insert @result (i, data) select @i, ' (' select @i = @i + 1 insert @result (i, j, data) select @i, seq, ' ' + case when seq = 1 then ' ' else ', ' end + 'b.' + colname from @cols where type 3 select @i = @i + 1 insert @result (i, data) select @i, ' );' select data from @result order by i,j,k,data

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  • Overload Avoidance

    - by mikef
    A little under a year ago, Matt Simmons wrote a rather reflective article about his terrifying brush with stress-induced ill health. SysAdmins and DBAs have always been prime victims of work-related stress, but I wonder if that predilection is perhaps getting worse, despite the best efforts of Matt and his trusty side-kick, HR. The constant pressure from share-holders and CFOs to 'streamline' the workforce is partially to blame, but the more recent culprit is technology itself. I can't deny that the rise of technologies like virtualization, PowerCLI, PowerShell, and a host of others has been a tremendous boon. As a result, individual IT professionals are now able to handle more and more tasks and manage increasingly large and complex environments. But, without a doubt, this is a two-edged sword; The reward for competence is invariably more work. Unfortunately, SysAdmins play such a pivotal role in modern business that it's easy to see how they can very quickly become swamped in conflicting demands coming from different directions. However, that doesn't justify the ridiculous hours many are asked (or volunteer) to devote to their work. Admirably though their commitment is, it isn't healthy for them, it sets a dangerous expectation, and eventually something will snap. There are times when everyone needs to step up to the plate outside of 'normal' work hours, but that time isn't all the time. Naturally, with all that lovely technology, you can automate more and more of those tricky tasks to keep on top of the workload, but you are still only human. Clever though you may be, there is a very real limit to how far technology can take you. I'm not suggesting that you avoid these technologies, or deliberately aim for mediocrity; I'm just saying that you need to be more than just technically skilled (and Wesley Nonapeptide riffs on and around this topic in his excellent 'Telepathic Robot Drones' blog post). You need to be able to manage expectations, not just Exchange. Specifically, that means your own expectations of what you are capable of, because those come before everyone else's. After all, how can you keep your work-life balance under control, if you're the one setting the bar way too high? Talking to your manager, or discussing issues with your users, is only going to be productive if you have some facts to work with. "Know Thyself" is the first law of managing work overload, and this is obviously a skill which people develop over time; the fact that veteran Sysadmins exist at all is testament to this. I'd just love to know how you get to that point. Personally, I'm using RescueTime to keep myself honest, but I'm open to recommendations for better methods. Do you track your own time, do you have an intuitive sense of what is possible, or do you just rely on someone else to handle that all for you? Cheers, Michael

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  • .NET Demon 1.0 Released

    - by theo.spears
    Today we're officially releasing version 1.0 of .NET Demon, the Visual Studio Extension Alex Davies and I have been working on for the last 6 months. There have been beta versions available for a while, but we have now released the first "official" version and made it available to purchase. If you haven't yet tried the tool, it's all about reducing the time between when you write a line of code and when you are able to try it out so you don't have to wait: Continuous compilation We use spare CPU cycles on your machine to compile your code in the background when you make changes, so assemblies are up to date whenever you want to run them. Some clever logic means we only recompile code which may have been affected by your changes. Continuous save .NET Demon can perform background saving, so you don't lose any work in case of crashes or power failures, and are less likely to forget to commit changed files. Continuous testing (Experimental) The testing tool in .NET Demon watches which code you change in your solution, and automatically reruns tests which are impacted, so you learn about any breaking changes as quickly as possible. It also gives you inline test coverage information inside Visual Studio. Continuous testing is still experimental - it will work fine in many cases, but we know it's not yet perfect. Releasing version 1.0 doesn't mean we're pausing development or pushing out improvements. We will still be regularly providing new versions with improved functionality and fixes for any bugs people come across. Visit the .NET Demon product page to download

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  • Custom EntityNotFoundDelegate

    - by Felix
    Hi all, I get a org.hibernate.ObjectNotFoundException when I want to delete an object which doesn't exist anymore via hibernate. I just want this exception to be ignored. I could catch the exception and ignore, this would be a solution maybe. But, since there is a hibernate support for ignoring this exception through org.hibernate.cfg.Configuration#entityNotFoundDelegate, I would like to use its advantage and control it using configuration. The question is then, how can I introduce my own/custom implementation of EntityNotFoundDelegate to the org.hibernate.cfg.Configuration? Does anybody have a sample code for me? Just an additional tip, I use Spring Framework as well in my project. Here is the exception that I get: Caused by: org.springframework.orm.hibernate3.HibernateObjectRetrievalFailureException: No row with the given identifier exists: [de.mycompany.domain.ResultObject#810b1334-32d3-02b0-e044-769e0ab48e48]; nested exception is org.hibernate.ObjectNotFoundException: No row with the given identifier exists: [de.mycompany.domain.ResultObject#810b1334-32d3-02b0-e044-769e0ab48e48] at org.springframework.orm.hibernate3.SessionFactoryUtils.convertHibernateAccessException(SessionFactoryUtils.java:660) at org.springframework.orm.hibernate3.HibernateAccessor.convertHibernateAccessException(HibernateAccessor.java:412) at org.springframework.orm.hibernate3.HibernateTemplate.doExecute(HibernateTemplate.java:424) at org.springframework.orm.hibernate3.HibernateTemplate.executeWithNativeSession(HibernateTemplate.java:374) at org.springframework.orm.hibernate3.HibernateTemplate.delete(HibernateTemplate.java:865) at org.springframework.orm.hibernate3.HibernateTemplate.delete(HibernateTemplate.java:859) at de.mycompany.utils.dao.impl.PersistentDaoImpl.delete(PersistentDaoImpl.java:50) at de.mycompany.utils.service.ServiceImpl.delete(ServiceImpl.java:68) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source) at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) at java.lang.reflect.Method.invoke(Unknown Source) at org.springframework.aop.support.AopUtils.invokeJoinpointUsingReflection(AopUtils.java:307) at org.springframework.aop.framework.ReflectiveMethodInvocation.invokeJoinpoint(ReflectiveMethodInvocation.java:182) at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:149) at de.mycompany.utils.service.ServiceInterceptor.invoke(ServiceInterceptor.java:43) at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:171) at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:204) at $Proxy3.delete(Unknown Source) ... 14 more Caused by: org.hibernate.ObjectNotFoundException: No row with the given identifier exists: [de.mycompany.domain.ResultObject#810b1334-32d3-02b0-e044-769e0ab48e48] at org.hibernate.impl.SessionFactoryImpl$2.handleEntityNotFound(SessionFactoryImpl.java:409) at org.hibernate.proxy.AbstractLazyInitializer.checkTargetState(AbstractLazyInitializer.java:108) at org.hibernate.proxy.AbstractLazyInitializer.initialize(AbstractLazyInitializer.java:97) at org.hibernate.proxy.AbstractLazyInitializer.getImplementation(AbstractLazyInitializer.java:140) at org.hibernate.engine.StatefulPersistenceContext.unproxyAndReassociate(StatefulPersistenceContext.java:594) at org.hibernate.event.def.DefaultDeleteEventListener.onDelete(DefaultDeleteEventListener.java:90) at org.hibernate.event.def.DefaultDeleteEventListener.onDelete(DefaultDeleteEventListener.java:74) at org.hibernate.impl.SessionImpl.fireDelete(SessionImpl.java:793) at org.hibernate.impl.SessionImpl.delete(SessionImpl.java:778) at org.springframework.orm.hibernate3.HibernateTemplate$26.doInHibernate(HibernateTemplate.java:871) at org.springframework.orm.hibernate3.HibernateTemplate.doExecute(HibernateTemplate.java:419) ... 30 more And my versions: Hibernate: 3.3.1 Spring: 2.5.6 Thanks in advance! Felix

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  • To Serve Man?

    - by Dave Convery
    Since the announcement of Windows 8 and its 'Metro' interface, the .NET community has wondered if the skills they've spent so long developing might be swept aside,in favour of HTML5 and JavaScript. Mercifully, that only seems to be true of SilverLight (as Simon Cooper points out), but it did leave me thinking how easy it is to impose a technology upon people without directly serving their needs. Case in point: QR codes. Once, probably, benign in purpose, they seem to have become a marketer's tool for determining when someone has engaged with an advert in the real world, with the same certainty as is possible online. Nobody really wants to use QR codes - it's far too much hassle. But advertisers want that data - they want to know that someone actually read their billboard / poster / cereal box, and so this flawed technology is suddenly everywhere, providing little to no value to the people who are actually meant to use it. What about 3D cinema? Profits from the film industry have been steadily increasing throughout the period that digital piracy and mass sharing has been possible, yet the industry cinema chains have forced 3D films upon a broadly uninterested audience, as a way of providing more purpose to going to a cinema, rather than watching it at home. Despite advances in digital projection, 3D cinema is scarcely more immersive to us than were William Castle's hoary old tricks of skeletons on wires and buzzing chairs were to our grandparents. iTunes - originally just a piece of software that catalogued and ripped music for you, but which is now multi-purpose bloatware; a massive, system-hogging behemoth. If it was being built for the people that used it, it would have been split into three or more separate pieces of software long ago. But as bloatware, it serves Apple primarily rather than us, stuffed with Music, Video, Various stores and phone / iPad management all bolted into one. Why? It's because, that way, you're more likely to bump into something you want to buy. You can't even buy a new laptop without finding that a significant chunk of your hard drive has been sold to 'select partners' - advertisers, suppliers of virus-busting software, and endless bloatware-flogging pop-ups that make using a new laptop without reformatting the hard drive like stepping back in time. The product you want is not the one you paid for. This is without even looking at services like Facebook and Klout, who provide a notional service with the intention of slurping up as much data about you as possible (in Klout's case, whether you create an account with them or not). What technologies do you find annoying or intrusive, and who benefits from keeping them around?

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  • Taking our Friendships to the next level.

    - by RedAndTheCommunity
    Red Gate have been running the Friends of Red Gate program for years now, and over that time we've built some great relationships with some truly awesome members of the SQL and .NET communities. When I took over the running of the program from Annabel in 2011, I was overwhelmed by the enthusiasm and commitment of our Friends. There were just so many of them, however, that it was hard to make the most of the relationships we had with people, and I wanted to fix that. I decided to survey all our Friends, to find out what they wanted to get out of, and put into, being in the Friends of Red Gate (FoRG) program. From the results of that survey, I identified 30 FoRGs that were really willing and able to go that step further to help Red Gate improve their tools, improve their relationship with the community, and improve the Friends of Red Gate program. Those 30 Friends of Red Gate have been awarded 'FoRG+' status. That means they'll: Have a closer relationship with the product teams, by getting involved in projects Have even more access to the inside track about the tools they're interested in Get the opportunity to come visit us at the Red Gate office and really influence the development of the tools. Plus more, depending on how the individual FoRG+ wants to work with us. This doesn't mean I've forgotten our other Friends; I'm working on ways to improve their experience of the Friends of Red Gate program. I'll write about them in another post. If you're an existing Friend of Red Gate, and you're interested in finding out how to get involved in the FoRG+ program, then I'd love to chat to you. For anyone that's interested in joining the Friend of Red Gate program, take a look at the web page dedicated to the program, and get in touch at [email protected] to be put on the waiting list for our 2013 program.

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  • Operator of the Week - Spools, Eager Spool

    For the fifth part of Fabiano's mission to describe the major Showplan Operators used by SQL Server's Query Optimiser, he introduces the spool operators and particularly the Eager Spool, explains blocking and non-blocking and then describes how the Halloween Problem is avoided.

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  • Regional Office Virtualization - Less Can Be More

    The dream of an 'office in a box' has been around for years, but the increasing sophistication of virtualization software has turned the dream into reality. Ben Lye explains the problems and benefits of reducing the amount of physical hardware that were deployed in his organisation's regional offices.

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  • Source-control 'wet-work'?

    - by Phil Factor
    When a design or creative work is flawed beyond remedy, it is often best to destroy it and start again. The other day, I lost the code to a long and intricate SQL batch I was working on. I’d thought it was impossible, but it happened. With all the technology around that is designed to prevent this occurring, this sort of accident has become a rare event.  If it weren’t for a deranged laptop, and my distraction, the code wouldn’t have been lost this time.  As always, I sighed, had a soothing cup of tea, and typed it all in again.  The new code I hastily tapped in  was much better: I’d held in my head the essence of how the code should work rather than the details: I now knew for certain  the start point, the end, and how it should be achieved. Instantly the detritus of half-baked thoughts fell away and I was able to write logical code that performed better.  Because I could work so quickly, I was able to hold the details of all the columns and variables in my head, and the dynamics of the flow of data. It was, in fact, easier and quicker to start from scratch rather than tidy up and refactor the existing code with its inevitable fumbling and half-baked ideas. What a shame that technology is now so good that developers rarely experience the cleansing shock of losing one’s code and having to rewrite it from scratch.  If you’ve never accidentally lost  your code, then it is worth doing it deliberately once for the experience. Creative people have, until Technology mistakenly prevented it, torn up their drafts or sketches, threw them in the bin, and started again from scratch.  Leonardo’s obsessive reworking of the Mona Lisa was renowned because it was so unusual:  Most artists have been utterly ruthless in destroying work that didn’t quite make it. Authors are particularly keen on writing afresh, and the results are generally positive. Lawrence of Arabia actually lost the entire 250,000 word manuscript of ‘The Seven Pillars of Wisdom’ by accidentally leaving it on a train at Reading station, before rewriting a much better version.  Now, any writer or artist is seduced by technology into altering or refining their work rather than casting it dramatically in the bin or setting a light to it on a bonfire, and rewriting it from the blank page.  It is easy to pick away at a flawed work, but the real creative process is far more brutal. Once, many years ago whilst running a software house that supplied commercial software to local businesses, I’d been supervising an accounting system for a farming cooperative. No packaged system met their needs, and it was all hand-cut code.  For us, it represented a breakthrough as it was for a government organisation, and success would guarantee more contracts. As you’ve probably guessed, the code got mangled in a disk crash just a week before the deadline for delivery, and the many backups all proved to be entirely corrupted by a faulty tape drive.  There were some fragments left on individual machines, but they were all of different versions.  The developers were in despair.  Strangely, I managed to re-write the bulk of a three-month project in a manic and caffeine-soaked weekend.  Sure, that elegant universally-applicable input-form routine was‘nt quite so elegant, but it didn’t really need to be as we knew what forms it needed to support.  Yes, the code lacked architectural elegance and reusability. By dawn on Monday, the application passed its integration tests. The developers rose to the occasion after I’d collapsed, and tidied up what I’d done, though they were reproachful that some of the style and elegance had gone out of the application. By the delivery date, we were able to install it. It was a smaller, faster application than the beta they’d seen and the user-interface had a new, rather Spartan, appearance that we swore was done to conform to the latest in user-interface guidelines. (we switched to Helvetica font to look more ‘Bauhaus’ ). The client was so delighted that he forgave the new bugs that had crept in. I still have the disk that crashed, up in the attic. In IT, we have had mixed experiences from complete re-writes. Lotus 123 never really recovered from a complete rewrite from assembler into C, Borland made the mistake with Arago and Quattro Pro  and Netscape’s complete rewrite of their Navigator 4 browser was a white-knuckle ride. In all cases, the decision to rewrite was a result of extreme circumstances where no other course of action seemed possible.   The rewrite didn’t come out of the blue. I prefer to remember the rewrite of Minix by young Linus Torvalds, or the rewrite of Bitkeeper by a slightly older Linus.  The rewrite of CP/M didn’t do too badly either, did it? Come to think of it, the guy who decided to rewrite the windowing system of the Xerox Star never regretted the decision. I’ll agree that one should often resist calls for a rewrite. One of the worst habits of the more inexperienced programmer is to denigrate whatever code he or she inherits, and then call loudly for a complete rewrite. They are buoyed up by the mistaken belief that they can do better. This, however, is a different psychological phenomenon, more related to the idea of some motorcyclists that they are operating on infinite lives, or the occasional squaddies that if they charge the machine-guns determinedly enough all will be well. Grim experience brings out the humility in any experienced programmer.  I’m referring to quite different circumstances here. Where a team knows the requirements perfectly, are of one mind on methodology and coding standards, and they already have a solution, then what is wrong with considering  a complete rewrite? Rewrites are so painful in the early stages, until that point where one realises the payoff, that even I quail at the thought. One needs a natural disaster to push one over the edge. The trouble is that source-control systems, and disaster recovery systems, are just too good nowadays.   If I were to lose this draft of this very blog post, I know I’d rewrite it much better. However, if you read this, you’ll know I didn’t have the nerve to delete it and start again.  There was a time that one prayed that unreliable hardware would deliver you from an unmaintainable mess of a codebase, but now technology has made us almost entirely immune to such a merciful act of God. An old friend of mine with long experience in the software industry has long had the idea of the ‘source-control wet-work’,  where one hires a malicious hacker in some wild eastern country to hack into one’s own  source control system to destroy all trace of the source to an application. Alas, backup systems are just too good to make this any more than a pipedream. Somehow, it would be difficult to promote the idea. As an alternative, could one construct a source control system that, on doing all the code-quality metrics, would systematically destroy all trace of source code that failed the quality test? Alas, I can’t see many managers buying into the idea. In reading the full story of the near-loss of Toy Story 2, it set me thinking. It turned out that the lucky restoration of the code wasn’t the happy ending one first imagined it to be, because they eventually came to the conclusion that the plot was fundamentally flawed and it all had to be rewritten anyway.  Was this an early  case of the ‘source-control wet-job’?’ It is very hard nowadays to do a rapid U-turn in a development project because we are far too prone to cling to our existing source-code.

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  • Showplan Operator of the Week - Compute Scalar

    The third part of Fabiano's mission to describe the major Showplan Operators used by SQL Server's Query Optimiser continues with the 'Compute Scalar' operator. Fabiano shows how a tweak to SQL to avoid a 'Compute Scalar' step can improve its performance.

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  • SQL Server CTE Basics

    The CTE was introduced into standard SQL in order to simplify various classes of SQL Queries for which a derived table just wasn't suitable. For some reason, it can be difficult to grasp the techniques of using it. Well, that's before Rob Sheldon explained it all so clearly for us.

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  • What Counts For A DBA: ESP

    - by Louis Davidson
    Now I don’t want to get religious here, and I’m not going to, but what I’m going to describe in this ‘What Counts for a DBA’ installment sometimes feels like magic. Often  I will spend hours thinking about the solution to a design issue or coding problem, working diligently to try to come up with a solution and then finally just give up with the feeling that I’m not even qualified to be a data entry clerk, much less a data architect.  At this point I often take a walk (or sometimes a nap), and then it hits me. I realize that I have the answer just sitting in my brain, ready to implement.  This phenomenon is not limited to walks either; it can happen almost any time after I stop my obsession about a problem. I call this phenomena ESP (or Extra-Sensory Programming.)  Another term for this could be ‘sleeping on it’, and while the idiom tends to mean to let time pass to actively think about a problem, sleeping on a problem also lets you relax and let your brain do the work. I first noticed this back in my college days when I would play video games for hours on end. We would get stuck deep in some dungeon unable to find a way out, playing for days on end until we were beaten down tired. Once we gave up and walked away, the solution would usually be there waiting for one of us before we came back to play the next day.  Sometimes it would be in the form of a dream, and sometimes it would just be that the problem was now easy to solve when we started to play again.  While it worked great for video games, it never occurred when I studied English Literature for hours on end, or even when I worked for the same sort of frustrating hours attempting to solve a homework problem in Calculus.  I believe that the difference was that I was passionate about the video game, and certainly far less so about homework where people used the word “thou” instead of “you” or x to represent a number. This phenomenon occurs somewhat more often in my current work as a professional data programmer, because I am very passionate about SQL and love those aspects of my career choice.  Every day that I get to draw a new data model to solve a customer issue, or write a complex SELECT statement to ferret out the answer to a complex data question, is a great day. I hope it is the same for any reader of this blog.  But, unfortunately, while the day on a whole is great, a heck of a lot of noise is generated in work life. There are the typical project deadlines, along with the requisite project manager sitting on your shoulders shouting slogans to try to make you to go faster: Add in office politics, and the occasional family issues that permeate the mind, and you lose the ability to think deeply about any problem, not to mention occasionally forgetting your own name.  These office realities coupled with a difficult SQL problem staring at you from your widescreen monitor will slowly suck the life force out of your body, making it seem impossible to solve the problem This is when the walk starts; or a nap. Maybe you hide from the madness under your desk like George Costanza hides from Steinbrenner on Seinfeld.  Forget about the problem. Free your mind from the insanity of the problem and your surroundings. Then let your training and education deep in your brain take over and see if it will passively do the rest for you. If you don’t end up with a solution, the worst case scenario is that you have a bit of exercise or rest, and you won’t have heard the phrase “better is the enemy of good enough” even once…which certainly will do your brain some good. Once you stop expecting whipping your brain for information, inspiration may just strike and instead of a humdrum solution you find a solution you hadn’t even considered, almost magically. So, my beloved manager, next time you have an urgent deadline and you come across me taking a nap, creep away quietly because I’m working, doing some extra-sensory programming.

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  • Automated Error Reporting in .NET Reflector - harnessing the most powerful test rig in existence

    - by Alex.Davies
    I know a testing system that will find more bugs than all the unit testing, integration testing, and QA you could possibly do. And the chances are you're not using it. It's called your users. It's a cliché that you should test so that you find your bugs rather than your users. Of course you should. But it's also a cliché that no software is ever shipped bug-free. Lost cause? No, opportunity! I think .NET Reflector 6 is pretty stable. In fact I know exactly how stable it is, because some (surprisingly high) proportion of its users tell me every time it crashes: If they press "Send Error Report", I get: And then I fix it. As a rough guess, while a standard stack trace is enough to fix a problem 30% of the time, having all those local variables in the stack trace means I can fix it about 80% of the time. How does this all happen? Did it take ages to code this swish system? Nope, it was one checkbox in SmartAssembly. It adds some clever code to your assembly to capture local variables every time an exception is thrown, and to ask your user to report it to you, with a variety of other useful information. Of course not all bugs show up as exceptions. But if you get used to knowing that SmartAssembly will tell you when an exception happens, you begin to change your coding style. Now, as long as an exception gets thrown in any situation you don't expect, you'll fix it if it ever happens. You'll start throwing exceptions liberally, and stop having to think about whether tiny edge cases are possible, as long as they throw an exception if they happen.

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  • Modernizr Rocks HTML5

    - by Laila
    HTML5 is a moving target.  At the moment, we don't know what will be in future versions.  In most circumstances, this really matters to the developer. When you're using Adobe Air, you can be reasonably sure what works, what is there, and what isn't, since you have a version of the browser built-in. With Metro, you can assume that you're going to be using at least IE 10.   If, however,  you are using HTML5 in a web application, then you are going to rely heavily on Feature Detection.  Feature-Detection is a collection of techniques that tell you, via JavaScript, whether the current browser has this feature natively implemented or not Feature Detection isn't just there for the esoteric stuff such as  Geo-location,  progress bars,  <canvas> support,  the new <input> types, Audio, Video, web workers or storage, but is required even for semantic markup, since old browsers make a pigs ear out of rendering this.  Feature detection can't rely just on reading the browser version and inferring from that what works. Instead, you must use JavaScript to check that an HTML5 feature is there before using it.  The problem with relying on the user-agent is that it takes a lot of historical data  to work out what version does what, and, anyway, the user-agent can be, and sometimes is, spoofed. The open-source library Modernizr  is just about the most essential  JavaScript library for anyone using HTML5, because it provides APIs to test for most of the CSS3 and HTML5 features before you use them, and is intelligent enough to alter semantic markup into 'legacy' 'markup  using shims  on page-load  for old browsers. It also allows you to check what video Codecs are installed for playing video. It also provides media queries  and conditional resource-loading (formerly YepNope.js.).  Generally, Modernizr gives you the choice of what you do about browsers that don't support the feature that you want. Often, the best choice is graceful degradation, but the resource-loading feature allows you to dynamically load JavaScript Shims to replace the standard API for missing or defective HTML5 functionality, called 'PolyFills'.  As the Modernizr site says 'Yes, not only can you use HTML5 today, but you can use it in the past, too!' The evolutionary progress of HTML5  requires a more defensive style of JavaScript programming where the programmer adopts a mindset of fearing the worst ( IE 6)  rather than assuming the best, whilst exploiting as many of the new HTML features as possible for the requirements of the site or HTML application.  Why would anyone want the distraction of developing their own techniques to do this when  Modernizr exists to do this for you? Laila

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  • Interview with Geoff Bones, developer on SQL Storage Compress

    - by red(at)work
    How did you come to be working at Red Gate? I've been working at Red Gate for nine months; before that I had been at a multinational engineering company. A number of my colleagues had left to work at Red Gate and spoke very highly of it, but I was happy in my role and thought, 'It can't be that great there, surely? They'll be back!' Then one day I visited to catch up them over lunch in the Red Gate canteen. I was so impressed with what I found there, that, three days later, I'd applied for a role as a developer. And how did you get into software development? My first job out of university was working as a systems programmer on IBM mainframes. This was quite a while ago: there was a lot of assembler and loading programs from tape drives and that kind of stuff. I learned a lot about how computers work, and this stood me in good stead when I moved over the development in the 90s. What's the best thing about working as a developer at Red Gate? Where should I start? One of the great things as a developer at Red Gate is the useful feedback and close contact we have with the people who use our products, either directly at trade shows and other events or through information coming through the product managers. The company's whole ethos is built around assisting the user, and this is in big contrast to my previous development roles. We aim to produce tools that people really want to use, that they enjoy using, and, as a developer, this is a great thing to aim for and a great feeling when we get it right. At Red Gate we also try to cut out the things that distract and stop us doing our jobs. As a developer, this means that I can focus on the code and the product I'm working on, knowing that others are doing a first-class job of making sure that the builds are running smoothly and that I'm getting great feedback from the testers. We keep our process light and effective, as we want to produce great software more than we want to produce great audit trails. Tell us a bit about the products you are currently working on. You mean HyperBac? First let me explain a bit about what HyperBac is. At heart it's a compression and encryption technology, but with a few added features that open up a wealth of really exciting possibilities. Right now we have the HyperBac technology in just three products: SQL HyperBac, SQL Virtual Restore and SQL Storage Compress, but we're only starting to develop what it can do. My personal favourite is SQL Virtual Restore; for example, I love the way you can use it to run independent test databases that are all backed by a single compressed backup. I don't think the market yet realises the kind of things you do once you are using these products. On the other hand, the benefits of SQL Storage Compress are straightforward: run your databases but use only 20% of the disk space. Databases are getting larger and larger, and, as they do, so does your ROI. What's a typical day for you? My days are pretty varied. We have our daily team stand-up meeting and then sometimes I will work alone on a current issue, or I'll be pair programming with one of my colleagues. From time to time we give half a day up to future planning with the team, when we look at the long and short term aims for the product and working out the development priorities. I also get to go to conferences and events, which is unusual for a development role and gives me the chance to meet and talk to our customers directly. Have you noticed anything different about developing tools for DBAs rather than other IT kinds of user? It seems to me that DBAs are quite independent minded; they know exactly what the problem they are facing is, and often have a solution in mind before they begin to look for what's on the market. This means that they're likely to cherry-pick tools from a range of vendors, picking the ones that are the best fit for them and that disrupt their environments the least. When I've met with DBAs, I've often been very impressed at their ability to summarise their set up, the issues, the obstacles they face when implementing a tool and their plans for their environment. It's easier to develop products for this audience as they give such a detailed overview of their needs, and I feel I understand their problems.

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  • Developing a SQL Server Function in a Test-Harness.

    - by Phil Factor
    /* Many times, it is a lot quicker to take some pain up-front and make a proper development/test harness for a routine (function or procedure) rather than think ‘I’m feeling lucky today!’. Then, you keep code and harness together from then on. Every time you run the build script, it runs the test harness too.  The advantage is that, if the test harness persists, then it is much less likely that someone, probably ‘you-in-the-future’  unintentionally breaks the code. If you store the actual code for the procedure as well as the test harness, then it is likely that any bugs in functionality will break the build rather than to introduce subtle bugs later on that could even slip through testing and get into production.   This is just an example of what I mean.   Imagine we had a database that was storing addresses with embedded UK postcodes. We really wouldn’t want that. Instead, we might want the postcode in one column and the address in another. In effect, we’d want to extract the entire postcode string and place it in another column. This might be part of a table refactoring or int could easily be part of a process of importing addresses from another system. We could easily decide to do this with a function that takes in a table as its parameter, and produces a table as its output. This is all very well, but we’d need to work on it, and test it when you make an alteration. By its very nature, a routine like this either works very well or horribly, but there is every chance that you might introduce subtle errors by fidding with it, and if young Thomas, the rather cocky developer who has just joined touches it, it is bound to break.     right, we drop the function we’re developing and re-create it. This is so we avoid the problem of having to change CREATE to ALTER when working on it. */ IF EXISTS(SELECT * FROM sys.objects WHERE name LIKE ‘ExtractPostcode’                                      and schema_name(schema_ID)=‘Dbo’)     DROP FUNCTION dbo.ExtractPostcode GO   /* we drop the user-defined table type and recreate it */ IF EXISTS(SELECT * FROM sys.types WHERE name LIKE ‘AddressesWithPostCodes’                                    and schema_name(schema_ID)=‘Dbo’)   DROP TYPE dbo.AddressesWithPostCodes GO /* we drop the user defined table type and recreate it */ IF EXISTS(SELECT * FROM sys.types WHERE name LIKE ‘OutputFormat’                                    and schema_name(schema_ID)=‘Dbo’)   DROP TYPE dbo.OutputFormat GO   /* and now create the table type that we can use to pass the addresses to the function */ CREATE TYPE AddressesWithPostCodes AS TABLE ( AddressWithPostcode_ID INT IDENTITY PRIMARY KEY, –because they work better that way! Address_ID INT NOT NULL, –the address we are fixing TheAddress VARCHAR(100) NOT NULL –The actual address ) GO CREATE TYPE OutputFormat AS TABLE (   Address_ID INT PRIMARY KEY, –the address we are fixing   TheAddress VARCHAR(1000) NULL, –The actual address   ThePostCode VARCHAR(105) NOT NULL – The Postcode )   GO CREATE FUNCTION ExtractPostcode(@AddressesWithPostCodes AddressesWithPostCodes READONLY)  /** summary:   > This Table-valued function takes a table type as a parameter, containing a table of addresses along with their integer IDs. Each address has an embedded postcode somewhere in it but not consistently in a particular place. The routine takes out the postcode and puts it in its own column, passing back a table where theinteger key is accompanied by the address without the (first) postcode and the postcode. If no postcode, then the address is returned unchanged and the postcode will be a blank string Author: Phil Factor Revision: 1.3 date: 20 May 2014 example:      – code: returns:   > Table of  Address_ID, TheAddress and ThePostCode. **/     RETURNS @FixedAddresses TABLE   (   Address_ID INT, –the address we are fixing   TheAddress VARCHAR(1000) NULL, –The actual address   ThePostCode VARCHAR(105) NOT NULL – The Postcode   ) AS – body of the function BEGIN DECLARE @BlankRange VARCHAR(10) SELECT  @BlankRange = CHAR(0)+‘- ‘+CHAR(160) INSERT INTO @FixedAddresses(Address_ID, TheAddress, ThePostCode) SELECT Address_ID,          CASE WHEN start>0 THEN REPLACE(STUFF([Theaddress],start,matchlength,”),‘  ‘,‘ ‘)             ELSE TheAddress END            AS TheAddress,        CASE WHEN Start>0 THEN SUBSTRING([Theaddress],start,matchlength-1) ELSE ” END AS ThePostCode FROM (–we have a derived table with the results we need for the chopping SELECT MAX(PATINDEX([matched],‘ ‘+[Theaddress] collate SQL_Latin1_General_CP850_Bin)) AS start,         MAX( CASE WHEN PATINDEX([matched],‘ ‘+[Theaddress] collate SQL_Latin1_General_CP850_Bin)>0 THEN TheLength ELSE 0 END) AS matchlength,        MAX(TheAddress) AS TheAddress,        Address_ID FROM (SELECT –first the match, then the length. There are three possible valid matches         ‘%['+@BlankRange+'][A-Z][0-9] [0-9][A-Z][A-Z]%’, 7 –seven character postcode       UNION ALL SELECT ‘%['+@BlankRange+'][A-Z][A-Z0-9][A-Z0-9] [0-9][A-Z][A-Z]%’, 8       UNION ALL SELECT ‘%['+@BlankRange+'][A-Z][A-Z][A-Z0-9][A-Z0-9] [0-9][A-Z][A-Z]%’, 9)      AS f(Matched,TheLength) CROSS JOIN  @AddressesWithPostCodes GROUP BY [address_ID] ) WORK; RETURN END GO ——————————-end of the function————————   IF NOT EXISTS (SELECT * FROM sys.objects WHERE name LIKE ‘ExtractPostcode’)   BEGIN   RAISERROR (‘There was an error creating the function.’,16,1)   RETURN   END   /* now the job is only half done because we need to make sure that it works. So we now load our sample data, making sure that for each Sample, we have what we actually think the output should be. */ DECLARE @InputTable AddressesWithPostCodes INSERT INTO  @InputTable(Address_ID,TheAddress) VALUES(1,’14 Mason mews, Awkward Hill, Bibury, Cirencester, GL7 5NH’), (2,’5 Binney St      Abbey Ward    Buckinghamshire      HP11 2AX UK’), (3,‘BH6 3BE 8 Moor street, East Southbourne and Tuckton W     Bournemouth UK’), (4,’505 Exeter Rd,   DN36 5RP Hawerby cum BeesbyLincolnshire UK’), (5,”), (6,’9472 Lind St,    Desborough    Northamptonshire NN14 2GH  NN14 3GH UK’), (7,’7457 Cowl St, #70      Bargate Ward  Southampton   SO14 3TY UK’), (8,”’The Pippins”, 20 Gloucester Pl, Chirton Ward,   Tyne & Wear   NE29 7AD UK’), (9,’929 Augustine lane,    Staple Hill Ward     South Gloucestershire      BS16 4LL UK’), (10,’45 Bradfield road, Parwich   Derbyshire    DE6 1QN UK’), (11,’63A Northampton St,   Wilmington    Kent   DA2 7PP UK’), (12,’5 Hygeia avenue,      Loundsley Green WardDerbyshire    S40 4LY UK’), (13,’2150 Morley St,Dee Ward      Dumfries and Galloway      DG8 7DE UK’), (14,’24 Bolton St,   Broxburn, Uphall and Winchburg    West Lothian  EH52 5TL UK’), (15,’4 Forrest St,   Weston-Super-Mare    North Somerset       BS23 3HG UK’), (16,’89 Noon St,     Carbrooke     Norfolk       IP25 6JQ UK’), (17,’99 Guthrie St,  New Milton    Hampshire     BH25 5DF UK’), (18,’7 Richmond St,  Parkham       Devon  EX39 5DJ UK’), (19,’9165 laburnum St,     Darnall Ward  Yorkshire, South     S4 7WN UK’)   Declare @OutputTable  OutputFormat  –the table of what we think the correct results should be Declare @IncorrectRows OutputFormat –done for error reporting   –here is the table of what we think the output should be, along with a few edge cases. INSERT INTO  @OutputTable(Address_ID,TheAddress, ThePostcode)     VALUES         (1, ’14 Mason mews, Awkward Hill, Bibury, Cirencester, ‘,‘GL7 5NH’),         (2, ’5 Binney St   Abbey Ward    Buckinghamshire      UK’,‘HP11 2AX’),         (3, ’8 Moor street, East Southbourne and Tuckton W    Bournemouth UK’,‘BH6 3BE’),         (4, ’505 Exeter Rd,Hawerby cum Beesby   Lincolnshire UK’,‘DN36 5RP’),         (5, ”,”),         (6, ’9472 Lind St,Desborough    Northamptonshire NN14 3GH UK’,‘NN14 2GH’),         (7, ’7457 Cowl St, #70    Bargate Ward  Southampton   UK’,‘SO14 3TY’),         (8, ”’The Pippins”, 20 Gloucester Pl, Chirton Ward,Tyne & Wear   UK’,‘NE29 7AD’),         (9, ’929 Augustine lane,  Staple Hill Ward     South Gloucestershire      UK’,‘BS16 4LL’),         (10, ’45 Bradfield road, ParwichDerbyshire    UK’,‘DE6 1QN’),         (11, ’63A Northampton St,Wilmington    Kent   UK’,‘DA2 7PP’),         (12, ’5 Hygeia avenue,    Loundsley Green WardDerbyshire    UK’,‘S40 4LY’),         (13, ’2150 Morley St,     Dee Ward      Dumfries and Galloway      UK’,‘DG8 7DE’),         (14, ’24 Bolton St,Broxburn, Uphall and Winchburg    West Lothian  UK’,‘EH52 5TL’),         (15, ’4 Forrest St,Weston-Super-Mare    North Somerset       UK’,‘BS23 3HG’),         (16, ’89 Noon St,  Carbrooke     Norfolk       UK’,‘IP25 6JQ’),         (17, ’99 Guthrie St,      New Milton    Hampshire     UK’,‘BH25 5DF’),         (18, ’7 Richmond St,      Parkham       Devon  UK’,‘EX39 5DJ’),         (19, ’9165 laburnum St,   Darnall Ward  Yorkshire, South     UK’,‘S4 7WN’)       insert into @IncorrectRows(Address_ID,TheAddress, ThePostcode)        SELECT Address_ID,TheAddress,ThePostCode FROM dbo.ExtractPostcode(@InputTable)       EXCEPT     SELECT Address_ID,TheAddress,ThePostCode FROM @outputTable; If @@RowCount>0        Begin        PRINT ‘The following rows gave ‘;     SELECT Address_ID,TheAddress,ThePostCode FROM @IncorrectRows        RAISERROR (‘These rows gave unexpected results.’,16,1);     end   /* For tear-down, we drop the user defined table type */ IF EXISTS(SELECT * FROM sys.types WHERE name LIKE ‘OutputFormat’                                    and schema_name(schema_ID)=‘Dbo’)   DROP TYPE dbo.OutputFormat GO /* once this is working, the development work turns from a chore into a delight and one ends up hitting execute so much more often to catch mistakes as soon as possible. It also prevents a wildly-broken routine getting into a build! */

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  • Tuning Red Gate: #1 of Many

    - by Grant Fritchey
    Everyone runs into performance issues at some point. Same thing goes for Red Gate software. Some of our internal systems were running into some serious bottlenecks. It just so happens that we have this nice little SQL Server monitoring tool. What if I were to, oh, I don't know, use the monitoring tool to identify the bottlenecks, figure out the causes and then apply a fix (where possible) and then start the whole thing all over again? Just a crazy thought. OK, I was asked to. This is my first time looking through these servers, so here's how I'd go about using SQL Monitor to get a quick health check, sort of like checking the vitals on a patient. First time opening up our internal SQL Monitor instance and I was greeted with this: Oh my. Maybe I need to get our internal guys to read my blog. Anyway, I know that there are two servers where most of the load is. I'll drill down on the first. I'm selecting the server, not the instance, by clicking on the server name. That opens up the Global Overview page for the server. The information here much more applicable to the "oh my gosh, I have a problem now" type of monitoring. But, looking at this, I am seeing something immediately. There are four(4) drives on the system. The C:\ has an average read time of 16.9ms, more than double the others. Is that a problem? Not sure, but it's something I'll look at. It's write time is higher too. I'll keep drilling down, first, to the unclosed alerts on the server. Now things get interesting. SQL Monitor has a number of different types of alerts, some related to error states, others to service status, and then some related to performance. Guess what I'm seeing a bunch of right here: Long running queries and long job durations. If you check the dates, they're all recent, within the last 24 hours. If they had just been old, uncleared alerts, I wouldn't be that concerned. But with all these, all performance related, and all in the last 24 hours, yeah, I'm concerned. At this point, I could just start responding to the Alerts. If I click on one of the the Long-running query alerts, I'll get all kinds of cool data that can help me determine why the query ran long. But, I'm not in a reactive mode here yet. I'm still gathering data, trying to understand how the server works. I have the information that we're generating a lot of performance alerts, let's sock that away for the moment. Instead, I'm going to back up and look at the Global Overview for the SQL Instance. It shows all the databases on the server and their status. Then it shows a number of basic metrics about the SQL Server instance, again for that "what's happening now" view or things. Then, down at the bottom, there is the Top 10 expensive queries list: This is great stuff. And no, not because I can see the top queries for the last 5 minutes, but because I can adjust that out 3 days. Now I can see where some serious pain is occurring over the last few days. Databases have been blocked out to protect the guilty. That's it for the moment. I have enough knowledge of what's going on in the system that I can start to try to figure out why the system is running slowly. But, I want to look a little more at some historical data, to understand better how this server is behaving. More next time.

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  • Why enumerator structs are a really bad idea

    - by Simon Cooper
    If you've ever poked around the .NET class libraries in Reflector, I'm sure you would have noticed that the generic collection classes all have implementations of their IEnumerator as a struct rather than a class. As you will see, this design decision has some rather unfortunate side effects... As is generally known in the .NET world, mutable structs are a Very Bad Idea; and there are several other blogs around explaining this (Eric Lippert's blog post explains the problem quite well). In the BCL, the generic collection enumerators are all mutable structs, as they need to keep track of where they are in the collection. This bit me quite hard when I was coding a wrapper around a LinkedList<int>.Enumerator. It boils down to this code: sealed class EnumeratorWrapper : IEnumerator<int> { private readonly LinkedList<int>.Enumerator m_Enumerator; public EnumeratorWrapper(LinkedList<int> linkedList) { m_Enumerator = linkedList.GetEnumerator(); } public int Current { get { return m_Enumerator.Current; } } object System.Collections.IEnumerator.Current { get { return Current; } } public bool MoveNext() { return m_Enumerator.MoveNext(); } public void Reset() { ((System.Collections.IEnumerator)m_Enumerator).Reset(); } public void Dispose() { m_Enumerator.Dispose(); } } The key line here is the MoveNext method. When I initially coded this, I thought that the call to m_Enumerator.MoveNext() would alter the enumerator state in the m_Enumerator class variable and so the enumeration would proceed in an orderly fashion through the collection. However, when I ran this code it went into an infinite loop - the m_Enumerator.MoveNext() call wasn't actually changing the state in the m_Enumerator variable at all, and my code was looping forever on the first collection element. It was only after disassembling that method that I found out what was going on The MoveNext method above results in the following IL: .method public hidebysig newslot virtual final instance bool MoveNext() cil managed { .maxstack 1 .locals init ( [0] bool CS$1$0000, [1] valuetype [System]System.Collections.Generic.LinkedList`1/Enumerator CS$0$0001) L_0000: nop L_0001: ldarg.0 L_0002: ldfld valuetype [System]System.Collections.Generic.LinkedList`1/Enumerator EnumeratorWrapper::m_Enumerator L_0007: stloc.1 L_0008: ldloca.s CS$0$0001 L_000a: call instance bool [System]System.Collections.Generic.LinkedList`1/Enumerator::MoveNext() L_000f: stloc.0 L_0010: br.s L_0012 L_0012: ldloc.0 L_0013: ret } Here, the important line is 0002 - m_Enumerator is accessed using the ldfld operator, which does the following: Finds the value of a field in the object whose reference is currently on the evaluation stack. So, what the MoveNext method is doing is the following: public bool MoveNext() { LinkedList<int>.Enumerator CS$0$0001 = this.m_Enumerator; bool CS$1$0000 = CS$0$0001.MoveNext(); return CS$1$0000; } The enumerator instance being modified by the call to MoveNext is the one stored in the CS$0$0001 variable on the stack, and not the one in the EnumeratorWrapper class instance. Hence why the state of m_Enumerator wasn't getting updated. Hmm, ok. Well, why is it doing this? If you have a read of Eric Lippert's blog post about this issue, you'll notice he quotes a few sections of the C# spec. In particular, 7.5.4: ...if the field is readonly and the reference occurs outside an instance constructor of the class in which the field is declared, then the result is a value, namely the value of the field I in the object referenced by E. And my m_Enumerator field is readonly! Indeed, if I remove the readonly from the class variable then the problem goes away, and the code works as expected. The IL confirms this: .method public hidebysig newslot virtual final instance bool MoveNext() cil managed { .maxstack 1 .locals init ( [0] bool CS$1$0000) L_0000: nop L_0001: ldarg.0 L_0002: ldflda valuetype [System]System.Collections.Generic.LinkedList`1/Enumerator EnumeratorWrapper::m_Enumerator L_0007: call instance bool [System]System.Collections.Generic.LinkedList`1/Enumerator::MoveNext() L_000c: stloc.0 L_000d: br.s L_000f L_000f: ldloc.0 L_0010: ret } Notice on line 0002, instead of the ldfld we had before, we've got a ldflda, which does this: Finds the address of a field in the object whose reference is currently on the evaluation stack. Instead of loading the value, we're loading the address of the m_Enumerator field. So now the call to MoveNext modifies the enumerator stored in the class rather than on the stack, and everything works as expected. Previously, I had thought enumerator structs were an odd but interesting feature of the BCL that I had used in the past to do linked list slices. However, effects like this only underline how dangerous mutable structs are, and I'm at a loss to explain why the enumerators were implemented as structs in the first place. (interestingly, the SortedList<TKey, TValue> enumerator is a struct but is private, which makes it even more odd - the only way it can be accessed is as a boxed IEnumerator!). I would love to hear people's theories as to why the enumerators are implemented in such a fashion. And bonus points if you can explain why LinkedList<int>.Enumerator.Reset is an explicit implementation but Dispose is implicit... Note to self: never ever ever code a mutable struct.

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  • Alan Turing Needs Your Help

    - by Chris Massey
    Well. sort of. Clearly, you are using a computer. If you are on this site, you are probably quite familiar with computers as artifacts of our modern society. Hopefully, you are also familiar with the fact that Alan Turing, logician and mathematician extraordinaire, was instrumental in laying down the foundations of modern computer science, and did a little work to help turn the tide of WWII in the Allies' favor. Hold that thought. A phenomenal collection of Turing's papers (including his first ever...(read more)

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