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  • Sweet and Sour Source Control

    - by Tony Davis
    Most database developers don't use Source Control. A recent anonymous poll on SQL Server Central asked its readers "Which Version Control system do you currently use to store you database scripts?" The winner, with almost 30% of the vote was...none: "We don't use source control for database scripts". In second place with almost 28% of the vote was Microsoft's VSS. VSS? Given its reputation for being buggy, unstable and lacking most of the basic features required of a proper source control system, answering VSS is really just another way of saying "I don't use Source Control". At first glance, it's a surprising thought. You wonder how database developers can work in a team and find out what changed, when the system worked before but is now broken; to work out what happened to their changes that now seem to have vanished; to roll-back a mistake quickly so that the rest of the team have a functioning build; to find instantly whether a suspect change has been deployed to production. Unfortunately, the survey didn't ask about the scale of the database development, and correlate the two questions. If there is only one database developer within a schema, who has an automated approach to regular generation of build scripts, then the need for a formal source control system is questionable. After all, a database stores far more about its metadata than a traditional compiled application. However, what is meat for a small development is poison for a team-based development. Here, we need a form of Source Control that can reconcile simultaneous changes, store the history of changes, derive versions and builds and that can cope with forks and merges. The problem comes when one borrows a solution that was designed for conventional programming. A database is not thought of as a "file", but a vast, interdependent and intricate matrix of tables, indexes, constraints, triggers, enumerations, static data and so on, all subtly interconnected. It is an awkward fit. Subversion with its support for merges and forks, and the tolerance of different work practices, can be made to work well, if used carefully. It has a standards-based architecture that allows it to be used on all platforms such as Windows Mac, and Linux. In the words of Erland Sommerskog, developers should "just do it". What's in a database is akin to a "binary file", and the developer must work only from the file. You check out the file, edit it, and save it to disk to compile it. Dependencies are validated at this point and if you've broken anything (e.g. you renamed a column and broke all the objects that reference the column), you'll find out about it right away, and you'll be forced to fix it. Nevertheless, for many this is an alien way of working with SQL Server. Subversion is the powerhouse, not the GUI. It doesn't work seamlessly with your existing IDE, and that usually means SSMS. So the question then becomes more subtle. Would developers be less reluctant to use a fully-featured source (revision) control system for a team database development if they had a turn-key, reliable system that fitted in with their existing work-practices? I'd love to hear what you think. Cheers, Tony.

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  • Cloud Backup: Getting the Users' Backs Up

    - by Tony Davis
    On Wednesday last week, Microsoft announced that as of July 1, all data transfers into its Microsoft Azure cloud will be free (though you have to pay for transferring data out). On Thursday last week, SQL Azure in Western Europe went down. It was a relatively short outage, but since SQL Azure currently provides no easy way to take a standard backup of a database and store it locally, many people had no recourse but to wait patiently for their cloud-based app to resume. It seems that Microsoft are very keen encourage developers to move their data onto their cloud, but are developers ready to do it, given that such basic backup capabilities are lacking? Recently on Simple-Talk, Mike Mooney described a perfect use case for the Microsoft Cloud. They had a simple web-based application with a SQL Server backend; they could move the application to Windows Azure, and the data into SQL Azure and in the process free themselves from much of the hassle surrounding management and scaling of the hardware, network and so on. It was a great fit and yet it nearly didn't happen; lack of support for the BACKUP command almost proved a show-stopper. Of course, backups of Azure databases are always and have always been taken automatically, for disaster recovery purposes, but these are strictly on-cloud copies and as of now it is not possible to use them to them to restore a database to a particular point in time. It seems that none of those clever Microsoft people managed to predict the need to perform basic backups of Azure databases so that copies could be stored locally, outside the Azure universe. At the very least, as Mike points out, performing a local backup before a new deployment is more or less mandatory. Microsoft did at least note the sound of gnashing teeth and, as a stop-gap measure, offered SQL Azure Database Copy which basically allows you to create an online clone of your database, but this doesn't allow for storing local archives of the data. To that end MS has provided SQL Azure Import/Export, to package up and export a database and its data, using BACPACs. These BACPACs do not guarantee transactional consistency; for example, if a child table is modified after the parent is copied, then the copied database will be in inconsistent state (meaning, to add to the fun, BACPACs need to be created from a database copy). In any event, widespread problems with BACPAC's evil cousin, the DACPAC have been well-documented, and it seems likely that many will also give BACPAC the bum's rush. Finally, in a TechEd 2011 presentation tagged "SQL Azure Advanced Administration", it was announced that "backup and restore" were coming in the next SQL Azure CTP. And yet this still doesn't mean that we'll get simple backups as DBAs know and love them. What it does mean, at least, is the ability to restore any given database to a point in time within a 2-week window. For the time being, if you want a local copy of your data and don't want to brave the BACPAC, one is left with SSIS or BCP, creative use of schema and data comparison tools, or use of SQL Azure Backup (currently in beta) in order to perform this simple but vital task. Cheers, Tony.

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  • Going by the eBook

    - by Tony Davis
    The book and magazine publishing world is rapidly going digital, and the industry is faced with making drastic changes to their ways of doing business. The sudden take-up of digital readers by the book-buying public has surprised even the most technological-savvy of the industry. Printed books just aren't selling like they did. In contrast, eBooks are doing well. The ePub file format is the standard around which all publishers are converging. ePub is a standard for formatting book content, so that it can be reflowed for various devices, with their widely differing screen-sizes, and can be read offline. If you unzip an ePub file, you'll find familiar formats such as XML, XHTML and CSS. This is both a blessing and a curse. Whilst it is good to be able to use familiar technologies that have been developed to a level of considerable sophistication, it doesn't get us all the way to producing a viable publication. XHTML is a page-description language, not a book-description language, as we soon found out during our initial experiments, when trying to specify headers, footers, indexes and chaptering. As a result, it is difficult to predict how any particular eBook application will decide to render a book. There isn't even a consensus as to how the cover image is specified. All of this is awkward for the publisher. Each book must be created and revised in a form from which can be generated a whole range of 'printed media', from print books, to Mobi for kindles, ePub for most Tablets and SmartPhones, HTML for excerpted chapters on websites, and a plethora of other formats for other eBook readers, each with its own idiosyncrasies. In theory, if we can get our content into a clean, semantic XML form, such as DOCBOOKS, we can, from there, after every revision, perform a series of relatively simple XSLT transformations to output anything from a HTML article, to an ePub file for reading on an iPad, to an ICML file (an XML-based file format supported by the InDesign tool), ready for print publication. As always, however, the task looks bigger the closer you get to the detail. On the way to the utopian world of an XML-based book format that encompasses all the diverse requirements of the different publication media, ePub looks like a reasonable format to adopt. Its forthcoming support for HTML 5 and CSS 3, with ePub 3.0, means that features, such as widow-and-orphan controls, multi-column flow and multi-media graphics can be incorporated into eBooks. This starts to make it possible to build an "app-like" experience into the eBook and to free publishers to think of putting context before container; to think of what content is required, be it graphical, textual or audio, from the point of view of the user, rather than what's possible in a given, traditional book "Container". In the meantime, there is a gap between what publishers require and what current technology can provide and, of course building this app-like experience is far from plain sailing. Real portability between devices is still a big challenge, and achieving the sort of wizardry seen in the likes of Theodore Grey's "Elements" eBook will require some serious device-specific programming skills. Cheers, Tony.

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  • SQL Server Optimizer Malfunction?

    - by Tony Davis
    There was a sharp intake of breath from the audience when Adam Machanic declared the SQL Server optimizer to be essentially "stuck in 1997". It was during his fascinating "Query Tuning Mastery: Manhandling Parallelism" session at the recent PASS SQL Summit. Paraphrasing somewhat, Adam (blog | @AdamMachanic) offered a convincing argument that the optimizer often delivers flawed plans based on assumptions that are no longer valid with today’s hardware. In 1997, when Microsoft engineers re-designed the database engine for SQL Server 7.0, SQL Server got its initial implementation of a cost-based optimizer. Up to SQL Server 2000, the developer often had to deploy a steady stream of hints in SQL statements to combat the occasionally wilful plan choices made by the optimizer. However, with each successive release, the optimizer has evolved and improved in its decision-making. It is still prone to the occasional stumble when we tackle difficult problems, join large numbers of tables, perform complex aggregations, and so on, but for most of us, most of the time, the optimizer purrs along efficiently in the background. Adam, however, challenged further any assumption that the current optimizer is competent at providing the most efficient plans for our more complex analytical queries, and in particular of offering up correctly parallelized plans. He painted a picture of a present where complex analytical queries have become ever more prevalent; where disk IO is ever faster so that reads from disk come into buffer cache faster than ever; where the improving RAM-to-data ratio means that we have a better chance of finding our data in cache. Most importantly, we have more CPUs at our disposal than ever before. To get these queries to perform, we not only need to have the right indexes, but also to be able to split the data up into subsets and spread its processing evenly across all these available CPUs. Improvements such as support for ColumnStore indexes are taking things in the right direction, but, unfortunately, deficiencies in the current Optimizer mean that SQL Server is yet to be able to exploit properly all those extra CPUs. Adam’s contention was that the current optimizer uses essentially the same costing model for many of its core operations as it did back in the days of SQL Server 7, based on assumptions that are no longer valid. One example he gave was a "slow disk" bias that may have been valid back in 1997 but certainly is not on modern disk systems. Essentially, the optimizer assesses the relative cost of serial versus parallel plans based on the assumption that there is no IO cost benefit from parallelization, only CPU. It assumes that a single request will saturate the IO channel, and so a query would not run any faster if we parallelized IO because the disk system simply wouldn’t be able to handle the extra pressure. As such, the optimizer often decides that a serial plan is lower cost, often in cases where a parallel plan would improve performance dramatically. It was challenging and thought provoking stuff, as were his techniques for driving parallelism through query logic based on subsets of rows that define the "grain" of the query. I highly recommend you catch the session if you missed it. I’m interested to hear though, when and how often people feel the force of the optimizer’s shortcomings. Barring mistakes, such as stale statistics, how often do you feel the Optimizer fails to find the plan you think it should, and what are the most common causes? Is it fighting to induce it toward parallelism? Combating unexpected plans, arising from table partitioning? Something altogether more prosaic? Cheers, Tony.

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  • Head in the Clouds

    - by Tony Davis
    We're just past the second anniversary of the launch of Windows Azure. A couple of years' experience with Azure in the industry has provided some obvious success stories, but has deflated some of the initial marketing hyperbole. As a general principle, Azure seems to work well in providing a Service-Oriented Architecture for services in enterprises that suffer wide fluctuations in demand. Instead of being obliged to provide hardware sufficient for the occasional peaks in demand, one can hire capacity only when it is needed, and the cost of hosting an application is no longer a capital cost. It enables companies to avoid having to scale out hardware for peak periods only to see it underused for the rest of the time. A customer-facing application such as a concert ticketing system, which suffers high demand in short, predictable bursts of activity, is a great example of an application that would work well in Azure. However, moving existing applications to Azure isn't something to be done on impulse. Unless your application is .NET-based, and consists of 'stateless' components that communicate via queues, you are probably in for a lot of redevelopment work. It makes most sense for IT departments who are already deep in this .NET mindset, and who also want 'grown-up' methods of staging, testing, and deployment. Azure fits well with this culture and offers, as a bonus, good Visual Studio integration. The most-commonly stated barrier to porting these applications to Azure is the problem of reconciling the use of the cloud with legislation for data privacy and security. Putting databases in the cloud is a sticky issue for many and impossible for some due to compliance and security issues, the need for direct control over data, and so on. In the face of feedback from the early adopters of Azure, Microsoft has broadened the architectural choices to cater for a wide range of requirements. As well as SQL Azure Database (SAD) and Azure storage, the unstructured 'BLOB and Entity-Attribute-Value' NoSQL storage alternative (which equates more closely with folders and files than a database), Windows Azure offers a wide range of storage options including use of services such as oData: developers who are programming for Windows Azure can simply choose the one most appropriate for their needs. Secondly, and crucially, the Windows Azure architecture allows you the freedom to produce hybrid applications, where only those parts that need cloud-based hosting are deployed to Azure, whereas those parts that must unavoidably be hosted in a corporate datacenter can stay there. By using a hybrid architecture, it will seldom, if ever, be necessary to move an entire application to the cloud, along with personal and financial data. For example that we could port to Azure only put those parts of our ticketing application that capture and process tickets orders. Once an order is captured, the financial side can be processed in our own data center. In short, Windows Azure seems to be a very effective way of providing services that are subject to wide but predictable fluctuations in demand. Have you come to the same conclusions, or do you think I've got it wrong? If you've had experience with Azure, would you recommend it? It would be great to hear from you. Cheers, Tony.

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  • The long road to bug-free software

    - by Tony Davis
    The past decade has seen a burgeoning interest in functional programming languages such as Haskell or, in the Microsoft world, F#. Though still on the periphery of mainstream programming, functional programming concepts are gradually seeping into the imperative C# language (for example, Lambda expressions have their root in functional programming). One of the more interesting concepts from functional programming languages is the use of formal methods, the lofty ideal behind which is bug-free software. The idea is that we write a specification that describes exactly how our function (say) should behave. We then prove that our function conforms to it, and in doing so have proved beyond any doubt that it is free from bugs. All programmers already use one form of specification, specifically their programming language's type system. If a value has a specific type then, in a type-safe language, the compiler guarantees that value cannot be an instance of a different type. Many extensions to existing type systems, such as generics in Java and .NET, extend the range of programs that can be type-checked. Unfortunately, type systems can only prevent some bugs. To take a classic problem of retrieving an index value from an array, since the type system doesn't specify the length of the array, the compiler has no way of knowing that a request for the "value of index 4" from an array of only two elements is "unsafe". We restore safety via exception handling, but the ideal type system will prevent us from doing anything that is unsafe in the first place and this is where we start to borrow ideas from a language such as Haskell, with its concept of "dependent types". If the type of an array includes its length, we can ensure that any index accesses into the array are valid. The problem is that we now need to carry around the length of arrays and the values of indices throughout our code so that it can be type-checked. In general, writing the specification to prove a positive property, even for a problem very amenable to specification, such as a simple sorting algorithm, turns out to be very hard and the specification will be different for every program. Extend this to writing a specification for, say, Microsoft Word and we can see that the specification would end up being no simpler, and therefore no less buggy, than the implementation. Fortunately, it is easier to write a specification that proves that a program doesn't have certain, specific and undesirable properties, such as infinite loops or accesses to the wrong bit of memory. If we can write the specifications to prove that a program is immune to such problems, we could reuse them in many places. The problem is the lack of specification "provers" that can do this without a lot of manual intervention (i.e. hints from the programmer). All this might feel a very long way off, but computing power and our understanding of the theory of "provers" advances quickly, and Microsoft is doing some of it already. Via their Terminator research project they have started to prove that their device drivers will always terminate, and in so doing have suddenly eliminated a vast range of possible bugs. This is a huge step forward from saying, "we've tested it lots and it seems fine". What do you think? What might be good targets for specification and verification? SQL could be one: the cost of a bug in SQL Server is quite high given how many important systems rely on it, so there's a good incentive to eliminate bugs, even at high initial cost. [Many thanks to Mike Williamson for guidance and useful conversations during the writing of this piece] Cheers, Tony.

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  • The long road to bug-free software

    - by Tony Davis
    The past decade has seen a burgeoning interest in functional programming languages such as Haskell or, in the Microsoft world, F#. Though still on the periphery of mainstream programming, functional programming concepts are gradually seeping into the imperative C# language (for example, Lambda expressions have their root in functional programming). One of the more interesting concepts from functional programming languages is the use of formal methods, the lofty ideal behind which is bug-free software. The idea is that we write a specification that describes exactly how our function (say) should behave. We then prove that our function conforms to it, and in doing so have proved beyond any doubt that it is free from bugs. All programmers already use one form of specification, specifically their programming language's type system. If a value has a specific type then, in a type-safe language, the compiler guarantees that value cannot be an instance of a different type. Many extensions to existing type systems, such as generics in Java and .NET, extend the range of programs that can be type-checked. Unfortunately, type systems can only prevent some bugs. To take a classic problem of retrieving an index value from an array, since the type system doesn't specify the length of the array, the compiler has no way of knowing that a request for the "value of index 4" from an array of only two elements is "unsafe". We restore safety via exception handling, but the ideal type system will prevent us from doing anything that is unsafe in the first place and this is where we start to borrow ideas from a language such as Haskell, with its concept of "dependent types". If the type of an array includes its length, we can ensure that any index accesses into the array are valid. The problem is that we now need to carry around the length of arrays and the values of indices throughout our code so that it can be type-checked. In general, writing the specification to prove a positive property, even for a problem very amenable to specification, such as a simple sorting algorithm, turns out to be very hard and the specification will be different for every program. Extend this to writing a specification for, say, Microsoft Word and we can see that the specification would end up being no simpler, and therefore no less buggy, than the implementation. Fortunately, it is easier to write a specification that proves that a program doesn't have certain, specific and undesirable properties, such as infinite loops or accesses to the wrong bit of memory. If we can write the specifications to prove that a program is immune to such problems, we could reuse them in many places. The problem is the lack of specification "provers" that can do this without a lot of manual intervention (i.e. hints from the programmer). All this might feel a very long way off, but computing power and our understanding of the theory of "provers" advances quickly, and Microsoft is doing some of it already. Via their Terminator research project they have started to prove that their device drivers will always terminate, and in so doing have suddenly eliminated a vast range of possible bugs. This is a huge step forward from saying, "we've tested it lots and it seems fine". What do you think? What might be good targets for specification and verification? SQL could be one: the cost of a bug in SQL Server is quite high given how many important systems rely on it, so there's a good incentive to eliminate bugs, even at high initial cost. [Many thanks to Mike Williamson for guidance and useful conversations during the writing of this piece] Cheers, Tony.

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  • Concurrent Affairs

    - by Tony Davis
    I once wrote an editorial, multi-core mania, on the conundrum of ever-increasing numbers of processor cores, but without the concurrent programming techniques to get anywhere near exploiting their performance potential. I came to the.controversial.conclusion that, while the problem loomed for all procedural languages, it was not a big issue for the vast majority of programmers. Two years later, I still think most programmers don't concern themselves overly with this issue, but I do think that's a bigger problem than I originally implied. Firstly, is the performance boost from writing code that can fully exploit all available cores worth the cost of the additional programming complexity? Right now, with quad-core processors that, at best, can make our programs four times faster, the answer is still no for many applications. But what happens in a few years, as the number of cores grows to 100 or even 1000? At this point, it becomes very hard to ignore the potential gains from exploiting concurrency. Possibly, I was optimistic to assume that, by the time we have 100-core processors, and most applications really needed to exploit them, some technology would be around to allow us to do so with relative ease. The ideal solution would be one that allows programmers to forget about the problem, in much the same way that garbage collection removed the need to worry too much about memory allocation. From all I can find on the topic, though, there is only a remote likelihood that we'll ever have a compiler that takes a program written in a single-threaded style and "auto-magically" converts it into an efficient, correct, multi-threaded program. At the same time, it seems clear that what is currently the most common solution, multi-threaded programming with shared memory, is unsustainable. As soon as a piece of state can be changed by a different thread of execution, the potential number of execution paths through your program grows exponentially with the number of threads. If you have two threads, each executing n instructions, then there are 2^n possible "interleavings" of those instructions. Of course, many of those interleavings will have identical behavior, but several won't. Not only does this make understanding how a program works an order of magnitude harder, but it will also result in irreproducible, non-deterministic, bugs. And of course, the problem will be many times worse when you have a hundred or a thousand threads. So what is the answer? All of the possible alternatives require a change in the way we write programs and, currently, seem to be plagued by performance issues. Software transactional memory (STM) applies the ideas of database transactions, and optimistic concurrency control, to memory. However, working out how to break down your program into sufficiently small transactions, so as to avoid contention issues, isn't easy. Another approach is concurrency with actors, where instead of having threads share memory, each thread runs in complete isolation, and communicates with others by passing messages. It simplifies concurrent programs but still has performance issues, if the threads need to operate on the same large piece of data. There are doubtless other possible solutions that I haven't mentioned, and I would love to know to what extent you, as a developer, are considering the problem of multi-core concurrency, what solution you currently favor, and why. Cheers, Tony.

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  • The clock hands of the buffer cache

    - by Tony Davis
    Over a leisurely beer at our local pub, the Waggon and Horses, Phil Factor was holding forth on the esoteric, but strangely poetic, language of SQL Server internals, riddled as it is with 'sleeping threads', 'stolen pages', and 'memory sweeps'. Generally, I remain immune to any twinge of interest in the bowels of SQL Server, reasoning that there are certain things that I don't and shouldn't need to know about SQL Server in order to use it successfully. Suddenly, however, my attention was grabbed by his mention of the 'clock hands of the buffer cache'. Back at the office, I succumbed to a moment of weakness and opened up Google. He wasn't lying. SQL Server maintains various memory buffers, or caches. For example, the plan cache stores recently-used execution plans. The data cache in the buffer pool stores frequently-used pages, ensuring that they may be read from memory rather than via expensive physical disk reads. These memory stores are classic LRU (Least Recently Updated) buffers, meaning that, for example, the least frequently used pages in the data cache become candidates for eviction (after first writing the page to disk if it has changed since being read into the cache). SQL Server clearly needs some mechanism to track which pages are candidates for being cleared out of a given cache, when it is getting too large, and it is this mechanism that is somewhat more labyrinthine than I previously imagined. Each page that is loaded into the cache has a counter, a miniature "wristwatch", which records how recently it was last used. This wristwatch gets reset to "present time", each time a page gets updated and then as the page 'ages' it clicks down towards zero, at which point the page can be removed from the cache. But what is SQL Server is suffering memory pressure and urgently needs to free up more space than is represented by zero-counter pages (or plans etc.)? This is where our 'clock hands' come in. Each cache has associated with it a "memory clock". Like most conventional clocks, it has two hands; one "external" clock hand, and one "internal". Slava Oks is very particular in stressing that these names have "nothing to do with the equivalent types of memory pressure". He's right, but the names do, in that peculiar Microsoft tradition, seem designed to confuse. The hands do relate to memory pressure; the cache "eviction policy" is determined by both global and local memory pressures on SQL Server. The "external" clock hand responds to global memory pressure, in other words pressure on SQL Server to reduce the size of its memory caches as a whole. Global memory pressure – which just to confuse things further seems sometimes to be referred to as physical memory pressure – can be either external (from the OS) or internal (from the process itself, e.g. due to limited virtual address space). The internal clock hand responds to local memory pressure, in other words the need to reduce the size of a single, specific cache. So, for example, if a particular cache, such as the plan cache, reaches a defined "pressure limit" the internal clock hand will start to turn and a memory sweep will be performed on that cache in order to remove plans from the memory store. During each sweep of the hands, the usage counter on the cache entry is reduced in value, effectively moving its "last used" time to further in the past (in effect, setting back the wrist watch on the page a couple of hours) and increasing the likelihood that it can be aged out of the cache. There is even a special Dynamic Management View, sys.dm_os_memory_cache_clock_hands, which allows you to interrogate the passage of the clock hands. Frequently turning hands equates to excessive memory pressure, which will lead to performance problems. Two hours later, I emerged from this rather frightening journey into the heart of SQL Server memory management, fascinated but still unsure if I'd learned anything that I'd put to any practical use. However, I certainly began to agree that there is something almost Tolkeinian in the language of the deep recesses of SQL Server. Cheers, Tony.

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  • What is the best option for reading Java property files?

    - by Mr Morgan
    Hello I have an application which uses a servlet to read an intialization parameter from web.xml for the location of a property file. The serlvet then creates an instance of a class which stores the location of the file for other programs to read as required. This class has appropriate get and set methods. But my question concerns access to the properties: should the physical property file be read by each program as at runtime or should the properties be stored in memory instead? The properties are not currently altered at runtime but this could change? I've seen various alternative approaches but am not sure which is best. Thanks Mr Morgan

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  • Getting the count of rows in a Java resultset

    - by Mr Morgan
    Hello Does anyone know a better way of getting the number of rows in a Java resultset returned from a MySQL database? I'm currently using this: public static int getResultSetRowCount(ResultSet resultSet) { int size = 0; try { resultSet.last(); size = resultSet.getRow(); resultSet.beforeFirst(); } catch(Exception ex) { return 0; } return size; } But am open to alternatives. The resultset returned is not going to be the total number of rows read from the database so I don;t think I can use SQL COUNT. Thanks Mr Morgan.

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  • Use of Java constructors in persistent entities

    - by Mr Morgan
    Hello I'm new to JPA and using persistence in Java anyway and I have two questions I can't quite work out: I have generated tags as: @JoinColumn(name = "UserName", referencedColumnName = "UserName") @ManyToOne(optional = false) private User userName; @JoinColumn(name = "DatasetNo", referencedColumnName = "DatasetNo") @ManyToOne(optional = false) private Dataset datasetNo; But in one of the constructors for the class, no reference is made to columns UserName or DatasetNo whereas all other columns in the class are referenced in the constructor. Can anyone tell me why this is? Both columns UserName and DatasetNo are 'foreign keys' on the entity Visualisation which corresponds to a database table of the same name. I can't quite work out the ORM. And when using entity classes, or POJO, is it better to have class variables like: private User userName; Where an instance of a class is specified or simply the key of that class instance like: private String userName; Thanks Mr Morgan.

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  • Dell Inspirion 1525 64bit driver compatibility

    - by Tony
    Hello, Can anyone tell me what the compatibility of drivers on 64bit vista are like on the Dell Inspiron 1525. Mine is just a year old now and I want to upgrade to 64bit vista. I wondered if there's known issues with drivers that I should be aware of before upgrading? Tony PS: is the upgrade worth it? My machine has 3GB of RAM and runs a T5800 2.0GHz DuoCore Processor. I use Visual Studio often and have loads of things open at the same time a lot. That's why I'm considering an upgrade.

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  • Problem installing a w2k DC on Hyper-V?

    - by Tony
    Hi, We have a cluster with four node windows 2008 r2 and hyper-v installed. We would like to install 2 VM with role domain controller w2k (the domain is different from the domain of the hyper-v cluster). Do you know if there are any restriction on doing it? Some collegues say that we risk data corruption if we do live migrations. Others speak about the fact that Microsoft don't support w2k any more. And others have doubts because the global catalog server installed on these DC could have loss of performance. Any idea? Thanks Tony

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  • Solution to: Hotmail Senders receiving NDR : “550-Please turn on SMTP Authentication in your mail client…”

    - by Tony Yustein
    Original question is here original question I can not answer to that question because the system requires me to have 10 credits, very nice.... This error is based mostly on mobile devices, mostly on iPhones and mostly on mobile networks. This is how much I have narrowed it to. I believe: Hotmail checks where your are connecting from If it is a mobile network it requires additional security for sending messages but the default iPhone config does not have this option for hotmail if the user creates the hotmail account on the iPhone with SMTP AUTH enabled manually it might solve the situation Cheers, Tony

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  • Where do all the old programmers go?

    - by Tony Lambert
    I know some people move over to management and some die... but where do the rest go and why? One reason people change to management is that in some companies the "Programmer" career path is very short - you can get to be a senior programmer within a few years. Leaving no way to get more money but to become a manager. In other companies project managers and programmers are parallel career paths so your project manager can be your junior. Tony

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  • 2 Parent BLOGs in DNN 5.x?

    - by Tony
    Hi there, I have created 2 parent BLOGs in DNN. BLOG x has 3 children BLOGs and BLOG y has 5 children. When I click Add BLOG entry, only BLOG x & is children come up in the dropdown list, BLOG y is missing. Anyone know why? Even if I go to the BLOG y and click Add BLOG entry, its missing. Many thanks, Tony.

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  • How to implment SSO with Joomla!?

    - by Tony Woo
    Hi Friends, I would like to use the Jommla! as our applications' portal, when one user logined joomla!, he/she don't need to enter password in our another application? anyone has any idear on how to implement this? or you have any web site which I can reference. Thanks in advance. Tony

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  • iphone doesn't refresh the localized icon after you change language setting !

    - by tony
    Hi, I manage to localized app icon and app name for different languages.I found the icon changes depending on the language setting on the iphone only when the first time when you install the app from xcode. after that, if i change the language setting, the app icon stay the same but only the app name changes to the localized one. Anyone has an idea is there is way of solving the problem? it seems iphone doens't refresh the icon after you change the language setting. Tony

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  • Updating version of multiple components using 1 file in c#

    - by tony
    Hello, I have a solution with many components and each component has its own version file (AssemblyInfo.cs). Currently each file as the standard structure: [assembly: AssemblyVersion("1.0.0.0")] [assembly: AssemblyFileVersion("1.0.0.0")] I would like to use the file version as the component version and keep that independent but I would like to have the "Product Version" be the same for all the components. I would like to do that by having a file at the solution level that is used by all the projects to get that version embedded. Any suggestions Thanks Tony

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  • Linux Kernel not upgraded (from Ubuntu 12.04 to 12.10) - can't remove old kernels and can't install new apps

    - by Tony Breyal
    Question: How do I remove old kernel images which refuse to be removed? Context: Yesterday I upgraded Ubuntu from 12.04 to 12.10. However, the linux kernel has not upgraded from 3.2 to 3.5 as I would have expected. $ uname -r 3.2.0-32-generic $ uname -a Linux tony-b 3.2.0-32-generic #51-Ubuntu SMP Wed Sep 26 21:33:09 UTC 2012 x86_64 x86_64 x86_64 GNU/Linux $ cat /proc/version Linux version 3.2.0-32-generic (buildd@batsu) (gcc version 4.6.3 (Ubuntu/Linaro 4.6.3-1ubuntu5) ) #51-Ubuntu SMP Wed Sep 26 21:33:09 UTC 2012 Not sure why that happened there. I wanted to install Audacity (v2.0.1-1_amd64) to edit a lecture audio file. When trying this operation through Ubuntu Software Center, it says that to install audacity, four items will need to be removed: linux-image-3.2.0-27-generic linux-image-3.2.0-29-generic linux-image-3.2.0-30-generic linux-image-3.2.0-31-generic So I click "Install Anyway" but it fails with the following output: installArchives() failed: (Reading database ... (Reading database ... 5% (Reading database ... 10% (Reading database ... 15% (Reading database ... 20% (Reading database ... 25% (Reading database ... 30% (Reading database ... 35% (Reading database ... 40% (Reading database ... 45% (Reading database ... 50% (Reading database ... 55% (Reading database ... 60% (Reading database ... 65% (Reading database ... 70% (Reading database ... 75% (Reading database ... 80% (Reading database ... 85% (Reading database ... 90% (Reading database ... 95% (Reading database ... 100% (Reading database ... 259675 files and directories currently installed.) Removing linux-image-3.2.0-27-generic ... Examining /etc/kernel/postrm.d . run-parts: executing /etc/kernel/postrm.d/initramfs-tools 3.2.0-27-generic /boot/vmlinuz-3.2.0-27-generic update-initramfs: Deleting /boot/initrd.img-3.2.0-27-generic run-parts: executing /etc/kernel/postrm.d/zz-update-grub 3.2.0-27-generic /boot/vmlinuz-3.2.0-27-generic Generating grub.cfg ... run-parts: /etc/kernel/postrm.d/zz-update-grub exited with return code 1 Failed to process /etc/kernel/postrm.d at /var/lib/dpkg/info/linux-image-3.2.0-27-generic.postrm line 328. dpkg: error processing linux-image-3.2.0-27-generic (--remove): subprocess installed post-removal script returned error exit status 1 No apport report written because MaxReports is reached already Removing linux-image-3.2.0-29-generic ... Examining /etc/kernel/postrm.d . run-parts: executing /etc/kernel/postrm.d/initramfs-tools 3.2.0-29-generic /boot/vmlinuz-3.2.0-29-generic update-initramfs: Deleting /boot/initrd.img-3.2.0-29-generic run-parts: executing /etc/kernel/postrm.d/zz-update-grub 3.2.0-29-generic /boot/vmlinuz-3.2.0-29-generic Generating grub.cfg ... run-parts: /etc/kernel/postrm.d/zz-update-grub exited with return code 1 Failed to process /etc/kernel/postrm.d at /var/lib/dpkg/info/linux-image-3.2.0-29-generic.postrm line 328. dpkg: error processing linux-image-3.2.0-29-generic (--remove): subprocess installed post-removal script returned error exit status 1 No apport report written because MaxReports is reached already Removing linux-image-3.2.0-30-generic ... Examining /etc/kernel/postrm.d . run-parts: executing /etc/kernel/postrm.d/initramfs-tools 3.2.0-30-generic /boot/vmlinuz-3.2.0-30-generic update-initramfs: Deleting /boot/initrd.img-3.2.0-30-generic run-parts: executing /etc/kernel/postrm.d/zz-update-grub 3.2.0-30-generic /boot/vmlinuz-3.2.0-30-generic Generating grub.cfg ... run-parts: /etc/kernel/postrm.d/zz-update-grub exited with return code 1 Failed to process /etc/kernel/postrm.d at /var/lib/dpkg/info/linux-image-3.2.0-30-generic.postrm line 328. dpkg: error processing linux-image-3.2.0-30-generic (--remove): subprocess installed post-removal script returned error exit status 1 No apport report written because MaxReports is reached already Removing linux-image-3.2.0-31-generic ... Examining /etc/kernel/postrm.d . run-parts: executing /etc/kernel/postrm.d/initramfs-tools 3.2.0-31-generic /boot/vmlinuz-3.2.0-31-generic update-initramfs: Deleting /boot/initrd.img-3.2.0-31-generic run-parts: executing /etc/kernel/postrm.d/zz-update-grub 3.2.0-31-generic /boot/vmlinuz-3.2.0-31-generic Generating grub.cfg ... run-parts: /etc/kernel/postrm.d/zz-update-grub exited with return code 1 Failed to process /etc/kernel/postrm.d at /var/lib/dpkg/info/linux-image-3.2.0-31-generic.postrm line 328. dpkg: error processing linux-image-3.2.0-31-generic (--remove): subprocess installed post-removal script returned error exit status 1 No apport report written because MaxReports is reached already Errors were encountered while processing: linux-image-3.2.0-27-generic linux-image-3.2.0-29-generic linux-image-3.2.0-30-generic linux-image-3.2.0-31-generic Error in function: Setting up grub-pc (2.00-7ubuntu11) ... /usr/sbin/grub-bios-setup: warning: Sector 32 is already in use by the program `FlexNet'; avoiding it. This software may cause boot or other problems in future. Please ask its authors not to store data in the boot track. Installation finished. No error reported. Generating grub.cfg ... dpkg: error processing grub-pc (--configure): subprocess installed post-installation script returned error exit status 1 It seems I need to remove the old linux images somehow. I have tried this through (1) Synaptic, (2) Ubuntu Tweak, and (3) Computer Janitor. The first two fail, whilst Computer Janitor won't even open. The output from Synaptic is: E: linux-image-3.2.0-27-generic: subprocess installed post-removal script returned error exit status 1 E: linux-image-3.2.0-29-generic: subprocess installed post-removal script returned error exit status 1 E: linux-image-3.2.0-30-generic: subprocess installed post-removal script returned error exit status 1 E: linux-image-3.2.0-31-generic: subprocess installed post-removal script returned error exit status 1 How do I remove these old images? Thank you kindly in advance for any help on this matter. P.S. Further information: $ dpkg --list | grep linux-image rH linux-image-3.2.0-27-generic 3.2.0-27.43 amd64 Linux kernel image for version 3.2.0 on 64 bit x86 SMP rH linux-image-3.2.0-29-generic 3.2.0-29.46 amd64 Linux kernel image for version 3.2.0 on 64 bit x86 SMP rH linux-image-3.2.0-30-generic 3.2.0-30.48 amd64 Linux kernel image for version 3.2.0 on 64 bit x86 SMP rH linux-image-3.2.0-31-generic 3.2.0-31.50 amd64 Linux kernel image for version 3.2.0 on 64 bit x86 SMP ii linux-image-3.2.0-32-generic 3.2.0-32.51 amd64 Linux kernel image for version 3.2.0 on 64 bit x86 SMP ii linux-image-3.5.0-17-generic 3.5.0-17.28 amd64 Linux kernel image for version 3.5.0 on 64 bit x86 SMP ii linux-image-extra-3.5.0-17-generic 3.5.0-17.28 amd64 Linux kernel image for version 3.5.0 on 64 bit x86 SMP ii linux-image-generic 3.5.0.17.19 amd64 Generic Linux kernel image But trying to remove using the command line fails too e.g.: $ sudo apt-get purge linux-image-3.2.0-27-generic Reading package lists... Done Building dependency tree Reading state information... Done The following packages will be REMOVED linux-image-3.2.0-27-generic linux-image-3.2.0-29-generic linux-image-3.2.0-30-generic linux-image-3.2.0-31-generic 0 upgraded, 0 newly installed, 4 to remove and 1 not upgraded. 5 not fully installed or removed. After this operation, 597 MB disk space will be freed. Do you want to continue [Y/n]? Y (Reading database ... 259675 files and directories currently installed.) Removing linux-image-3.2.0-27-generic ... Examining /etc/kernel/postrm.d . run-parts: executing /etc/kernel/postrm.d/initramfs-tools 3.2.0-27-generic /boot/vmlinuz-3.2.0-27-generic update-initramfs: Deleting /boot/initrd.img-3.2.0-27-generic run-parts: executing /etc/kernel/postrm.d/zz-update-grub 3.2.0-27-generic /boot/vmlinuz-3.2.0-27-generic Generating grub.cfg ... run-parts: /etc/kernel/postrm.d/zz-update-grub exited with return code 1 Failed to process /etc/kernel/postrm.d at /var/lib/dpkg/info/linux-image-3.2.0-27-generic.postrm line 328. dpkg: error processing linux-image-3.2.0-27-generic (--remove): subprocess installed post-removal script returned error exit status 1 No apport report written because MaxReports has already been reached Removing linux-image-3.2.0-29-generic ... Examining /etc/kernel/postrm.d . run-parts: executing /etc/kernel/postrm.d/initramfs-tools 3.2.0-29-generic /boot/vmlinuz-3.2.0-29-generic update-initramfs: Deleting /boot/initrd.img-3.2.0-29-generic run-parts: executing /etc/kernel/postrm.d/zz-update-grub 3.2.0-29-generic /boot/vmlinuz-3.2.0-29-generic Generating grub.cfg ... run-parts: /etc/kernel/postrm.d/zz-update-grub exited with return code 1 Failed to process /etc/kernel/postrm.d at /var/lib/dpkg/info/linux-image-3.2.0-29-generic.postrm line 328. dpkg: error processing linux-image-3.2.0-29-generic (--remove): subprocess installed post-removal script returned error exit status 1 No apport report written because MaxReports has already been reached Removing linux-image-3.2.0-30-generic ... Examining /etc/kernel/postrm.d . run-parts: executing /etc/kernel/postrm.d/initramfs-tools 3.2.0-30-generic /boot/vmlinuz-3.2.0-30-generic update-initramfs: Deleting /boot/initrd.img-3.2.0-30-generic run-parts: executing /etc/kernel/postrm.d/zz-update-grub 3.2.0-30-generic /boot/vmlinuz-3.2.0-30-generic Generating grub.cfg ... run-parts: /etc/kernel/postrm.d/zz-update-grub exited with return code 1 Failed to process /etc/kernel/postrm.d at /var/lib/dpkg/info/linux-image-3.2.0-30-generic.postrm line 328. dpkg: error processing linux-image-3.2.0-30-generic (--remove): subprocess installed post-removal script returned error exit status 1 No apport report written because MaxReports has already been reached Removing linux-image-3.2.0-31-generic ... Examining /etc/kernel/postrm.d . run-parts: executing /etc/kernel/postrm.d/initramfs-tools 3.2.0-31-generic /boot/vmlinuz-3.2.0-31-generic update-initramfs: Deleting /boot/initrd.img-3.2.0-31-generic run-parts: executing /etc/kernel/postrm.d/zz-update-grub 3.2.0-31-generic /boot/vmlinuz-3.2.0-31-generic Generating grub.cfg ... run-parts: /etc/kernel/postrm.d/zz-update-grub exited with return code 1 Failed to process /etc/kernel/postrm.d at /var/lib/dpkg/info/linux-image-3.2.0-31-generic.postrm line 328. dpkg: error processing linux-image-3.2.0-31-generic (--remove): subprocess installed post-removal script returned error exit status 1 No apport report written because MaxReports has already been reached Errors were encountered while processing: linux-image-3.2.0-27-generic linux-image-3.2.0-29-generic linux-image-3.2.0-30-generic linux-image-3.2.0-31-generic E: Sub-process /usr/bin/dpkg returned an error code (1)

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  • Going for Gold

    - by Simple-Talk Editorial Team
    There was a spring in the step of some members of our development teams here at Red Gate, on hearing that on five gold awards at 2012′s SQL Mag Community and Editors Choice Awards. And why not? It’s a nice recognition that their efforts were appreciated by many in the SQL Server community. The team at Simple-Talk don’t tend to spring, but even we felt a twinge of pride in the fact that SQL Scripts Manager received Gold for Editor’s Choice in the Best Free Tools category. The tool began life as a “Down Tools” project and is one that we’ve supported and championed in various articles on Simple-talk.com. Over a Cambridge Bitter in the Waggon and Horses, we’ve often reflected on how nice it would be to nominate our own awards. Of course, we’d have to avoid nominating Red Gate tools in each category, even the free ones, for fear of seeming biased,  but we could still award other people’s free tools, couldn’t we? So allow us to set the stage for the annual Simple-Talk Community Tool awards… Onto the platform we shuffle, to applause from the audience; Chris in immaculate tuxedo, Alice in stunning evening gown, Dave and Tony looking vaguely uncomfortable, Andrew somehow distracted, as if his mind is elsewhere. Tony strides up to the lectern, and coughs lightly…”In the free-tool category we have the three nominations, and they are…” (rustle of the envelope opening) Ola Hallengren’s SQL Server Maintenance Solution (applause) Adam Machanic’s WhoIsActive (cheers, more applause) Brent Ozar’s sp_Blitz (much clapping) “Before we declare the winner, I’d like to say a few words in recognition of a grand tradition in a SQL Server community that continues to offer its members a steady supply of excellent, free tools. It hammers home the fundamental principle that a tool should solve a single, pressing and frustrating problem, but you should only ever build your own solution to that problem if you are certain that you cannot buy it, or that someone has not already provided it free. We have only three finalists tonight, but I feel compelled to mention a few other tools that we also use and appreciate, such as Microsoft’s Logparser, Open source Curl, Microsoft’s TableDiff.exe, Performance Analysis of Logs (PAL) Tool, SQL Server Cache Manager and SQLPSX.” “And now I’ll hand over to Alice to announce the winner.” Alice strides over to the microphone, tearing open the envelope. “The winner,” she pauses for dramatic effect “… is …Ola Hallengren’s SQL Server Maintenance Solution!” Queue much applause and consumption of champagne. Did we get it wrong? What free tool would you nominate? Let us know! Cheers, Simple-Talk Editorial Team (Andrew, Alice, Chris, Dave, Tony)

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