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  • SQL aggregate query question

    - by Phil
    Hi, Can anyone help me with a SQL query in Apache Derby SQL to get a "simple" count. Given a table ABC that looks like this... id a b c 1 1 1 1 2 1 1 2 3 2 1 3 4 2 1 1 ** 5 2 1 2 ** ** 6 2 2 1 ** 7 3 1 2 8 3 1 3 9 3 1 1 How can I write a query to get a count of how may distinct values of 'a' have both (b=1 and c=2) AND (b=2 and c=1) to get the correct result of 1. (the two rows marked match the criteria and both have a value of a=2, there is only 1 distinct value of a in this table that match the criteria) The tricky bit is that (b=1 and c=2) AND (b=2 and c=1) are obviously mutually exclusive when applied to a single row. .. so how do I apply that expression across multiple rows of distinct values for a? These queries are wrong but to illustrate what I'm trying to do... "SELECT DISTINCT COUNT(a) WHERE b=1 AND c=2 AND b=2 AND c=1 ..." .. (0) no go as mutually exclusive "SELECT DISTINCT COUNT(a) WHERE b=1 AND c=2 OR b=2 AND c=1 ..." .. (3) gets me the wrong result. SELECT COUNT(a) (CASE WHEN b=1 AND c=10 THEN 1 END) FROM ABC WHERE b=2 AND c=1 .. (0) no go as mutually exclusive Cheers, Phil.

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  • Mr Flibble: As Seen Through a Lens, Darkly

    - by Phil Factor
    One of the rewarding things about getting involved with Simple-Talk has been in meeting and working with some pretty daunting talents. I’d like to say that Dom Reed’s talents are at the end of the visible spectrum, but then there is Richard, who pops up on national radio occasionally, presenting intellectual programs, Andrew, master of the ukulele, with his pioneering local history work, and Tony with marathon running and his past as a university lecturer. However, Dom, who is Red Gate’s head of creative design and who did the preliminary design work for Simple-Talk, has taken the art photography to an extreme that was impossible before Photoshop. He’s not the first person to take a photograph of himself every day for two years, but he is definitely the first to weave the results into a frightening narrative that veers from comedy to pathos, using all the arts of Photoshop to create a fictional character, Mr Flibble.   Have a look at some of the Flickr pages. Uncle Spike The B-Men – Woolverine The 2011 BoyZ iN Sink reunion tour turned out to be their last Error 404 – Flibble not found Mr Flibble is not a normal type of alter-ego. We generally prefer to choose bronze age warriors of impossibly magnificent physique and stamina; superheroes who bestride the world, scorning the forces of evil and anarchy in a series noble and righteous quests. Not so Dom, whose Mr Flibble is vulnerable, and laid low by an addiction to toxic substances. His work has gained an international cult following and is used as course material by several courses in photography. Although his work was for a while ignored by the more conventional world of ‘art’ photography they became famous through the internet. His photos have received well over a million views on Flickr. It was definitely time to turn this work into a book, because the whole sequence of images has its maximum effect when seen in sequence. He has a Kickstarter project page, one of the first following the recent UK launch of the crowdfunding platform. The publication of the book should be a major event and the £45 I shall divvy up will be one of the securest investments I shall ever make. The local news in Cambridge picked up on the project and I can quote from the report by the excellent Cabume website , the source of Tech news from the ‘Cambridge cluster’ Put really simply Mr Flibble likes to dress up and take pictures of himself. One of the benefits of a split personality, however is that Mr Flibble is supported in his endeavour by Reed’s top notch photography skills, supreme mastery of Photoshop and unflinching dedication to the cause. The duo have collaborated to take a picture every day for the past 730-plus days. It is not a big surprise that neither Mr Flibble nor Reed watches any TV: In addition to his full-time role at Cambridge software house,Red Gate Software as head of creativity and the two to five hours a day he spends taking the Mr Flibble shots, Reed also helps organise the . And now Reed is using Kickstarter to see if the world is ready for a Mr Flibble coffee table book. Judging by the early response it is. At the time of writing, just a few days after it went live, ‘I Drink Lead Paint: An absurd photography book by Mr Flibble’ had raised £1,545 of the £10,000 target it needs to raise by the Friday 30 November deadline from 37 backers. Following the standard Kickstarter template, Reed is offering a series of rewards based on the amount pledged, ranging from a Mr Flibble desktop wallpaper for pledges of £5 or more to a signed copy of the book for pledges of £45 or more, right up to a starring role in the book for £1,500. Mr Flibble is unquestionably one of the more deranged Kickstarter hopefuls, but don’t think for a second that he doesn’t have a firm grasp on the challenges he faces on the road to immortalisation on 150 gsm stock. Under the section ‘risks and challenges’ on his Kickstarter page his statement begins: “An angry horde of telepathic iguanas discover the world’s last remaining stock of vintage lead paint and hold me to ransom. Gosh how I love to guzzle lead paint. Anyway… faced with such brazen bravado, I cower at the thought of taking on their combined might and die a sad and lonely Flibble deprived of my one and only true liquid love.” At which point, Reed manages to wrestle away the keyboard, giving him the opportunity to present slightly more cogent analysis of the obstacles the project must still overcome. We asked Reed a few questions about Mr Flibble’s Kickstarter adventure and felt that his responses were worth publishing in full: Firstly, how did you manage it – holding down a full time job and also conceiving and executing these ideas on a daily basis? I employed a small team of ferocious gerbils to feed me ideas on a daily basis. Whilst most of their ideas were incomprehensibly rubbish and usually revolved around food, just occasionally they’d give me an idea like my B-Men series. As a backup plan though, I found that the best way to generate ideas was to actually start taking photos. If I were to stand in front of the camera, pull a silly face, place a vegetable on my head or something else equally stupid, the resulting photo of that would typically spark an idea when I came to look at it. Sitting around idly trying to think of an idea was doomed to result in no ideas. I admit that I really struggled with time. I’m proud that I never missed a day, but it was definitely hard when you were late from work, tired or doing something socially on the same day. I don’t watch TV, which I guess really helps, because I’d frequently be spending 2-5 hours taking and processing the photos every day. Are there any overlaps between software development and creative thinking? Software is an inherently creative business and the speed that it moves ensures you always have to find solutions to new things. Everyone in the team needs to be a problem solver. Has it helped me specifically with my photography? Probably. Working within teams that continually need to figure out new stuff keeps the brain feisty I suppose, and I guess I’m continually exposed to a lot of possible sources of inspiration. How specifically will this Kickstarter project allow you to test the commercial appeal of your work and do you plan to get the book into shops? It’s taken a while to be confident saying it, but I know that people like the work that I do. I’ve had well over a million views of my pictures, many humbling comments and I know I’ve garnered some loyal fans out there who anticipate my next photo. For me, this Kickstarter is about seeing if there’s worth to my work beyond just making people smile. In an online world where there’s an abundance of freely available content, can you hope to receive anything from what you do, or would people just move onto the next piece of content if you happen to ask for some support? A book has been the single-most requested thing that people have asked me to produce and it’s something that I feel would showcase my work well. It’s just hard to convince people in the publishing industry just now to take any kind of risk – they’ve been hit hard. If I can show that people would like my work enough to buy a book, then it sends a pretty clear picture that publishers might hear, or it gives me the confidence enough to invest in myself a bit more – hard to do when you’re riddled with self-doubt! I’d love to see my work in the shops, yes. I could see it being the thing that someone flips through idly as they’re Christmas shopping and recognizing that it’d be just the perfect gift for their difficult to buy for friend or relative. That said, working in the software industry means I’m clearly aware of how I could use technology to distribute my work, but I can’t deny that there’s something very appealing to having a physical thing to hold in your hands. If the project is successful is there a chance that it could become a full-time job? At the moment that seems like a distant dream, as should this be successful, there are many more steps I’d need to take to reach any kind of business viability. Kickstarter seems exactly that – a way for people to help kick start me into something that could take off. If people like my work and want me to succeed with it, then taking a look at my Kickstarter page (and hopefully pledging a bit of support) would make my elbows blush considerably. So there is is. An opportunity to open the wallet just a bit to ensure that one of the more unusual talents sees the light in the format it deserves.  

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  • Ada and 'The Book'

    - by Phil Factor
    The long friendship between Charles Babbage and Ada Lovelace created one of the most exciting and mysterious of collaborations ever to have resulted in a technological breakthrough. The fireworks that created by the collision of two prodigious mathematical and creative talents resulted in an invention, the Analytical Engine, which went on to change society fundamentally. However, beyond that, we just don't know what the bulk of their collaborative work was about:;  it was done in strictest secrecy. Even the known outcome of their friendship, the first programmable computer, was shrouded in mystery. At the time, nobody, except close friends and family, had any idea of Ada Byron's contribution to the invention of the ‘Engine’, and how to program it. Her great insight was published in August 1843, under the initials AAL, standing for Ada Augusta Lovelace, her title then being the Countess of Lovelace. It was contained in a lengthy ‘note’ to her translation of a publication that remains the best description of Babbage's amazing Analytical Engine. The secret identity of the person behind those enigmatic initials was finally revealed by Prince de Polignac who, seventy years later, wrote to Ada's daughter to seek confirmation that her mother had, indeed, been the author of the brilliant sentences that described so accurately how Babbage's mechanical computer could be programmed with punch-cards. L.F. Menabrea's paper on the Analytical Engine first appeared in the 'Bibliotheque Universelle de Geneve' in October 1842, and Ada translated it anonymously for Taylor's 'Scientific Memoirs'. Charles Babbage was surprised that she had not written an original paper as she already knew a surprising amount about the way the machine worked. He persuaded her to at least write some explanatory notes. These notes ended up extending to four times the length of the original article and represented the first published account of how a machine could be programmed to perform any calculation. Her example of programming the Bernoulli sequence would have worked on the Analytical engine had the device’s construction been completed, and gave Ada an unassailable claim to have invented the art of programming. What was the reason for Ada's secrecy? She was the only legitimate child of Lord Byron, who was probably the best known celebrity of the age, so she was already famous. She was a senior aristocrat, with titles, a fortune in money and vast estates in the Midlands. She had political influence, and was the cousin of Lord Melbourne, who was the Prime Minister at that time. She was friendly with the young Queen Victoria. Her mathematical activities were a pastime, and not one that would be considered by others to be in keeping with her roles and responsibilities. You wouldn't dare to dream up a fictional heroine like Ada. She was dazzlingly beautiful and talented. She could speak several languages fluently, and play some musical instruments with professional skill. Contemporary accounts refer to her being 'accomplished in science, art and literature'. On top of that, she was a brilliant mathematician, a talent inherited from her mother, Annabella Milbanke. In her mother's circle of literary and scientific friends was Charles Babbage, and Ada's friendship with him dates from her teenage zest for Mathematics. She was one of the first people he'd ever met who understood what he had attempted to achieve with the 'Difference Engine', and with whom he could converse as intellectual equals. He arranged for her to have an education from the most talented academics in the country. Ada melted the heart of the cantankerous genius to the point that he became a faithful and loyal father-figure to her. She was one of the very few who could grasp the principles of the later, and very different, ‘Analytical Engine’ which was designed from the start to tackle a variety of tasks. Sadly, Ada Byron's life ended less than a decade after completing the work that assured her long-term fame, in November 1852. She was dying of cancer, her gambling habits had caused her to run up huge debts, she'd had more than one affairs, and she was being blackmailed. Her brilliant but unempathic mother was nursing her in her final illness, destroying her personal letters and records, and repaying her debts. Her husband was distraught but helpless. Charles Babbage, however, maintained his steadfast paternalistic friendship to the end. She appointed her loyal friend to be her executor. For years, she and Babbage had been working together on a secret project, known only as 'The Book'. We have a clue to what it was in a letter written by her nine years earlier, on 11th August 1843. It was a joint project by herself and Lord Lovelace, her husband, and was intended to involve Babbage's 'undivided energies'. It involved 'consulting your Engine' (it required Babbage’s computer). The letter gives no hint about the project except for the high-minded nature of its purpose, and its highly mathematical nature.  From then on, the surviving correspondence between the two gives only veiled references to 'The Book'. There isn't much, since Babbage later destroyed any letters that could have damaged her reputation within the Establishment. 'I cannot spare the book today, which I am very sorry for. At the moment I want it for constant reference, but I think you can have it tomorrow' (Oct 1844)  And 'I will send you the book directly, and you can say, when you receive it, how long you will want to keep it'. (Nov 1844)  The two of them were obviously intent on the work: She writes, four years later, 'I have an engagement for Wednesday which will prevent me from attending to your wishes about the book' (Dec 1848). This was something that they both needed to work on, but could not do in parallel: 'I will send the book on Tuesday, and it can be left with you till Friday' (11 Feb 1849). After six years work, it had been so well-handled that it was beginning to fall apart: 'Don't forget the new cover you promised for the book. The poor book is very shabby and wants one' (20 Sept 1849). So what was going on? The word 'book' was not a code-word: it was a real book, probably a 'printer's blank', plain paper, but properly bound so printers and publishers could show off how the published work might look. The hints from the correspondence are of advanced mathematics. It is obvious that the book was travelling between them, back and forth, each one working on it for less than a week before passing it back. Ada and her husband were certainly involved in gambling large sums of money on the horses, and so most biographers have concluded that the three of them were trying to calculate the mathematical odds on the horses. This theory has three large problems. Firstly, Ada's original letter proposing the project refers to its high-minded nature. Babbage was temperamentally opposed to gambling and would scarcely have given so much time to the project, even though he was devoted to Ada. Secondly, Babbage would have very soon have realized the hopelessness of trying to beat the bookies. This sort of betting never attracts his type of intellectual background. The third problem is that any work on calculating the odds on horses would not need a well-thumbed book to pass back and forth between them; they would have not had to work in series. The original project was instigated by Ada, along with her husband, William King-Noel, 1st Earl of Lovelace. Charles Babbage was invited to join the project after the couple had come up with the idea. What could William have contributed? One might assume that William was a Bertie Wooster character, addicted only to the joys of the turf, but this was far from the truth. He was a scientist, a Cambridge graduate who was later elected to be a Fellow of the Royal Society. After Eton, he went to Trinity College, Cambridge. On graduation, he entered the diplomatic service and acted as secretary under Lord Nugent, who was Lord Commissioner of the Ionian Islands. William was very friendly with Babbage too, able to discuss scientific matters on equal terms. He was a capable engineer who invented a process for bending large timbers by the application of steam heat. He delivered a paper to the Institution of Civil Engineers in 1849, and received praise from the great engineer, Isambard Kingdom Brunel. As well as being Lord Lieutenant of the County of Surrey for most of Victoria's reign, he had time for a string of scientific and engineering achievements. Whatever the project was, it is unlikely that William was a junior partner. After Ada's death, the project disappeared. Then, two years later, Babbage, through one of his occasional outbursts of temper, demonstrated that he was able to decrypt one of the most powerful of secret codes, Vigenère's autokey cipher.  All contemporary diplomatic and military messages used a variant of this cipher. Babbage had made three important discoveries, namely, the mathematical law of this cipher, the principle of the key periodicity, and the technique of the symmetry of position. The technique is now known as the Kasiski examination, also called the Kasiski test, but Babbage got there first. At one time, he listed amongst his future projects, the writing of a book 'The Philosophy of Decyphering', but it never came to anything. This discovery was going to change the course of history, since it was used to decipher the Russians’ military dispatches in the Crimean war. Babbage himself played a role during the Crimean War as a cryptographical adviser to his friend, Rear-Admiral Sir Francis Beaufort of the Admiralty. This is as much as we can be certain about in trying to make sense of the bulk of the time that Charles Babbage and Ada Lovelace worked together. Nine years of intensive work, involving the 'Engine' and a great deal of mathematics and research seems to have been lost: or has it? I've argued in the past http://www.simple-talk.com/community/blogs/philfactor/archive/2008/06/13/59614.aspx that the cracking of the Vigenère autokey cipher, was a fundamental motive behind the British Government's support and funding of the 'Difference Engine'. The Duke of Wellington, whose understanding of the military significance of being able to read enemy dispatches, was the most steadfast advocate of the project. If the three friends were actually doing the work of cracking codes by mathematical techniques that used the techniques of key periodicity, and symmetry of position (the use of a book being passed quickly to and fro is very suggestive), intending to then use the 'Engine' to do the routine cracking of each dispatch, then this is a rather different story. The project was Ada and William's idea. (William had served in the diplomatic service and would be familiar with the use of codes). This makes Ada Lovelace the initiator of a project which, by giving both Britain, and probably the USA, a diplomatic and military advantage in the second part of the Nineteenth century, changed world history. Ada would never have wanted any credit for cracking the cipher, and developing the method that rendered all contemporary military and diplomatic ciphering techniques nugatory; quite the reverse. And it is clear from the gaps in the record of the letters between the collaborators that the evidence was destroyed, probably on her request by her irascible but intensely honorable executor, Charles Babbage. Charles Babbage toyed with the idea of going public, but the Crimean war put an end to that. The British Government had a valuable secret, and intended to keep it that way. Ada and Charles had quite often discussed possible moneymaking projects that would fund the development of the Analytic Engine, the first programmable computer, but their secret work was never in the running as a potential cash cow. I suspect that the British Government was, even then, working on the concealment of a discovery whose value to the nation depended on it remaining so. The success of code-breaking in the Crimean war, and the American Civil war, led to the British and Americans  subsequently giving much more weight and funding to the science of decryption. Paradoxically, this makes Ada's contribution even closer to the creation of Colossus, the first digital computer, at Bletchley Park, specifically to crack the Nazi’s secret codes.

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  • How to get SQL Railroad Diagrams from MSDN BNF syntax notation.

    - by Phil Factor
    pre {margin-bottom:.0001pt; font-size:8.0pt; font-family:"Courier New"; margin-left: 0cm; margin-right: 0cm; margin-top: 0cm; } On SQL Server Books-On-Line, in the Transact-SQL Reference (database Engine), every SQL Statement has its syntax represented in  ‘Backus–Naur Form’ notation (BNF)  syntax. For a programmer in a hurry, this should be ideal because It is the only quick way to understand and appreciate all the permutations of the syntax. It is a great feature once you get your eye in. It isn’t the only way to get the information;  You can, of course, reverse-engineer an understanding of the syntax from the examples, but your understanding won’t be complete, and you’ll have wasted time doing it. BNF is a good start in representing the syntax:  Oracle and SQLite go one step further, and have proper railroad diagrams for their syntax, which is a far more accessible way of doing it. There are three problems with the BNF on MSDN. Firstly, it is isn’t a standard version of  BNF, but an ancient fork from EBNF, inherited from Sybase. Secondly, it is excruciatingly difficult to understand, and thirdly it has a number of syntactic and semantic errors. The page describing DML triggers, for example, currently has the absurd BNF error that makes it state that all statements in the body of the trigger must be separated by commas.  There are a few other detail problems too. Here is the offending syntax for a DML trigger, pasted from MSDN. Trigger on an INSERT, UPDATE, or DELETE statement to a table or view (DML Trigger) CREATE TRIGGER [ schema_name . ]trigger_name ON { table | view } [ WITH <dml_trigger_option> [ ,...n ] ] { FOR | AFTER | INSTEAD OF } { [ INSERT ] [ , ] [ UPDATE ] [ , ] [ DELETE ] } [ NOT FOR REPLICATION ] AS { sql_statement [ ; ] [ ,...n ] | EXTERNAL NAME <method specifier [ ; ] > }   <dml_trigger_option> ::=     [ ENCRYPTION ]     [ EXECUTE AS Clause ]   <method_specifier> ::=  This should, of course, be /* Trigger on an INSERT, UPDATE, or DELETE statement to a table or view (DML Trigger) */ CREATE TRIGGER [ schema_name . ]trigger_name ON { table | view } [ WITH <dml_trigger_option> [ ,...n ] ] { FOR | AFTER | INSTEAD OF } { [ INSERT ] [ , ] [ UPDATE ] [ , ] [ DELETE ] } [ NOT FOR REPLICATION ] AS { {sql_statement [ ; ]} [ ...n ] | EXTERNAL NAME <method_specifier> [ ; ] }   <dml_trigger_option> ::=     [ ENCRYPTION ]     [ EXECUTE AS CLAUSE ]   <method_specifier> ::=     assembly_name.class_name.method_name I’d love to tell Microsoft when I spot errors like this so they can correct them but I can’t. Obviously, there is a mechanism on MSDN to get errors corrected by using comments, but that doesn’t work for me (*Error occurred while saving your data.”), and when I report that the comment system doesn’t work to MSDN, I get no reply. I’ve been trying to create railroad diagrams for all the important SQL Server SQL statements, as good as you’d find for Oracle, and have so far published the CREATE TABLE and ALTER TABLE railroad diagrams based on the BNF. Although I’ve been aware of them, I’ve never realised until recently how many errors there are. Then, Colin Daley created a translator for the SQL Server dialect of  BNF which outputs standard EBNF notation used by the W3C. The example MSDN BNF for the trigger would be rendered as … /* Trigger on an INSERT, UPDATE, or DELETE statement to a table or view (DML Trigger) */ create_trigger ::= 'CREATE TRIGGER' ( schema_name '.' ) ? trigger_name 'ON' ( table | view ) ( 'WITH' dml_trigger_option ( ',' dml_trigger_option ) * ) ? ( 'FOR' | 'AFTER' | 'INSTEAD OF' ) ( ( 'INSERT' ) ? ( ',' ) ? ( 'UPDATE' ) ? ( ',' ) ? ( 'DELETE' ) ? ) ( 'NOT FOR REPLICATION' ) ? 'AS' ( ( sql_statement ( ';' ) ? ) + | 'EXTERNAL NAME' method_specifier ( ';' ) ? )   dml_trigger_option ::= ( 'ENCRYPTION' ) ? ( 'EXECUTE AS CLAUSE' ) ?   method_specifier ::= assembly_name '.' class_name '.' method_name Colin’s intention was to allow anyone to paste SQL Server’s BNF notation into his website-based parser, and from this generate classic railroad diagrams via Gunther Rademacher's Railroad Diagram Generator.  Colin's application does this for you: you're not aware that you are moving to a different site.  Because Colin's 'translator' it is a parser, it will pick up syntax errors. Once you’ve fixed the syntax errors, you will get the syntax in the form of a human-readable railroad diagram and, in this form, the semantic mistakes become flamingly obvious. Gunter’s Railroad Diagram Generator is brilliant. To be able, after correcting the MSDN dialect of BNF, to generate a standard EBNF, and from thence to create railroad diagrams for SQL Server’s syntax that are as good as Oracle’s, is a great boon, and many thanks to Colin for the idea. Here is the result of the W3C EBNF from Colin’s application then being run through the Railroad diagram generator. create_trigger: dml_trigger_option: method_specifier:   Now that’s much better, you’ll agree. This is pretty easy to understand, and at this point any error is immediately obvious. This should be seriously useful, and it is to me. However  there is that snag. The BNF is generally incorrect, and you can’t expect the average visitor to mess about with it. The answer is, of course, to correct the BNF on MSDN and maybe even add railroad diagrams for the syntax. Stop giggling! I agree it won’t happen. In the meantime, we need to collaboratively store and publish these corrected syntaxes ourselves as we do them. How? GitHub?  SQL Server Central?  Simple-Talk? What should those of us who use the system  do with our corrected EBNF so that anyone can use them without hassle?

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  • Listing common SQL Code Smells.

    - by Phil Factor
    Once you’ve done a number of SQL Code-reviews, you’ll know those signs in the code that all might not be well. These ’Code Smells’ are coding styles that don’t directly cause a bug, but are indicators that all is not well with the code. . Kent Beck and Massimo Arnoldi seem to have coined the phrase in the "OnceAndOnlyOnce" page of www.C2.com, where Kent also said that code "wants to be simple". Bad Smells in Code was an essay by Kent Beck and Martin Fowler, published as Chapter 3 of the book ‘Refactoring: Improving the Design of Existing Code’ (ISBN 978-0201485677) Although there are generic code-smells, SQL has its own particular coding habits that will alert the programmer to the need to re-factor what has been written. See Exploring Smelly Code   and Code Deodorants for Code Smells by Nick Harrison for a grounding in Code Smells in C# I’ve always been tempted by the idea of automating a preliminary code-review for SQL. It would be so useful to trawl through code and pick up the various problems, much like the classic ‘Lint’ did for C, and how the Code Metrics plug-in for .NET Reflector by Jonathan 'Peli' de Halleux is used for finding Code Smells in .NET code. The problem is that few of the standard procedural code smells are relevant to SQL, and we need an agreed list of code smells. Merrilll Aldrich made a grand start last year in his blog Top 10 T-SQL Code Smells.However, I'd like to make a start by discovering if there is a general opinion amongst Database developers what the most important SQL Smells are. One can be a bit defensive about code smells. I will cheerfully write very long stored procedures, even though they are frowned on. I’ll use dynamic SQL occasionally. You can only use them as an aid for your own judgment and it is fine to ‘sign them off’ as being appropriate in particular circumstances. Also, whole classes of ‘code smells’ may be irrelevant for a particular database. The use of proprietary SQL, for example, is only a ‘code smell’ if there is a chance that the database will have to be ported to another RDBMS. The use of dynamic SQL is a risk only with certain security models. As the saying goes,  a CodeSmell is a hint of possible bad practice to a pragmatist, but a sure sign of bad practice to a purist. Plamen Ratchev’s wonderful article Ten Common SQL Programming Mistakes lists some of these ‘code smells’ along with out-and-out mistakes, but there are more. The use of nested transactions, for example, isn’t entirely incorrect, even though the database engine ignores all but the outermost: but it does flag up the possibility that the programmer thinks that nested transactions are supported. If anything requires some sort of general agreement, the definition of code smells is one. I’m therefore going to make this Blog ‘dynamic, in that, if anyone twitters a suggestion with a #SQLCodeSmells tag (or sends me a twitter) I’ll update the list here. If you add a comment to the blog with a suggestion of what should be added or removed, I’ll do my best to oblige. In other words, I’ll try to keep this blog up to date. The name against each 'smell' is the name of the person who Twittered me, commented about or who has written about the 'smell'. it does not imply that they were the first ever to think of the smell! Use of deprecated syntax such as *= (Dave Howard) Denormalisation that requires the shredding of the contents of columns. (Merrill Aldrich) Contrived interfaces Use of deprecated datatypes such as TEXT/NTEXT (Dave Howard) Datatype mis-matches in predicates that rely on implicit conversion.(Plamen Ratchev) Using Correlated subqueries instead of a join   (Dave_Levy/ Plamen Ratchev) The use of Hints in queries, especially NOLOCK (Dave Howard /Mike Reigler) Few or No comments. Use of functions in a WHERE clause. (Anil Das) Overuse of scalar UDFs (Dave Howard, Plamen Ratchev) Excessive ‘overloading’ of routines. The use of Exec xp_cmdShell (Merrill Aldrich) Excessive use of brackets. (Dave Levy) Lack of the use of a semicolon to terminate statements Use of non-SARGable functions on indexed columns in predicates (Plamen Ratchev) Duplicated code, or strikingly similar code. Misuse of SELECT * (Plamen Ratchev) Overuse of Cursors (Everyone. Special mention to Dave Levy & Adrian Hills) Overuse of CLR routines when not necessary (Sam Stange) Same column name in different tables with different datatypes. (Ian Stirk) Use of ‘broken’ functions such as ‘ISNUMERIC’ without additional checks. Excessive use of the WHILE loop (Merrill Aldrich) INSERT ... EXEC (Merrill Aldrich) The use of stored procedures where a view is sufficient (Merrill Aldrich) Not using two-part object names (Merrill Aldrich) Using INSERT INTO without specifying the columns and their order (Merrill Aldrich) Full outer joins even when they are not needed. (Plamen Ratchev) Huge stored procedures (hundreds/thousands of lines). Stored procedures that can produce different columns, or order of columns in their results, depending on the inputs. Code that is never used. Complex and nested conditionals WHILE (not done) loops without an error exit. Variable name same as the Datatype Vague identifiers. Storing complex data  or list in a character map, bitmap or XML field User procedures with sp_ prefix (Aaron Bertrand)Views that reference views that reference views that reference views (Aaron Bertrand) Inappropriate use of sql_variant (Neil Hambly) Errors with identity scope using SCOPE_IDENTITY @@IDENTITY or IDENT_CURRENT (Neil Hambly, Aaron Bertrand) Schemas that involve multiple dated copies of the same table instead of partitions (Matt Whitfield-Atlantis UK) Scalar UDFs that do data lookups (poor man's join) (Matt Whitfield-Atlantis UK) Code that allows SQL Injection (Mladen Prajdic) Tables without clustered indexes (Matt Whitfield-Atlantis UK) Use of "SELECT DISTINCT" to mask a join problem (Nick Harrison) Multiple stored procedures with nearly identical implementation. (Nick Harrison) Excessive column aliasing may point to a problem or it could be a mapping implementation. (Nick Harrison) Joining "too many" tables in a query. (Nick Harrison) Stored procedure returning more than one record set. (Nick Harrison) A NOT LIKE condition (Nick Harrison) excessive "OR" conditions. (Nick Harrison) User procedures with sp_ prefix (Aaron Bertrand) Views that reference views that reference views that reference views (Aaron Bertrand) sp_OACreate or anything related to it (Bill Fellows) Prefixing names with tbl_, vw_, fn_, and usp_ ('tibbling') (Jeremiah Peschka) Aliases that go a,b,c,d,e... (Dave Levy/Diane McNurlan) Overweight Queries (e.g. 4 inner joins, 8 left joins, 4 derived tables, 10 subqueries, 8 clustered GUIDs, 2 UDFs, 6 case statements = 1 query) (Robert L Davis) Order by 3,2 (Dave Levy) MultiStatement Table functions which are then filtered 'Sel * from Udf() where Udf.Col = Something' (Dave Ballantyne) running a SQL 2008 system in SQL 2000 compatibility mode(John Stafford)

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  • Exclusive Expert and Peer-Led Sessions—Only at Oracle OpenWorld

    - by Phil Catalano-Oracle
    With more than 2,500 sessions, dozens of hands-on labs, hundreds of demos, four Exhibition Halls, and countless meet-ups, Oracle OpenWorld is the place to learn, share, and network. Planning ahead is always a smart move and here are some links to help you plan your Oracle OpenWorld schedule. You will hear directly from Oracle Thought leaders, Oracle Support experts and their peers about how to succeed across the Oracle stack—from Oracle Consulting Thought Leader sessions dedicated to the cloud to hands on demos showing the value of My Oracle Support—Oracle Open World is your one stop shop for everything Oracle. Featured sessions include: Is Your Organization Trying to Focus on an ERP Cloud Strategy? Modernize Your Analytics Solutions Is Your Organization Trying to Focus on a CX Cloud Strategy? Best Practices for Deploying a DBaaS in a Private Cloud Model Visit the Support & Services Oracle OpenWorld website to discover how you can take advantage of all Oracle OpenWorld has to offer. With 500 Services experts, 50+ sessions, networking events and demos of powerful new support tools, customers will find relevant, useful information about how Oracle Services enables the success of their Oracle hardware and software investments.

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  • When Your Boss Doesn't Want you to Succeed

    - by Phil Factor
    You're working hard to get an application finished. You are programming long into the evenings sometimes, and eating sandwiches at your desk instead of taking a lunch break. Then one day you glance up at the IT manager, serene in his mysterious round of meetings, and think 'Does he actually care whether this project succeeds or not?'. The question may seem absurd. Of course the project must succeed. The truth, as always, is often far more complex. Your manager may even be doing his best to make sure you don't succeed. Why? There have always been rich pickings for the unscrupulous in IT.  In extreme cases, where administrators struggle with scarcely-comprehended technical issues, huge sums of money can be lost and gained without any perceptible results. In a very few cases can fraud be proven: most of the time, the intricacies of the 'game' are such that one can do little more than harbor suspicion.  Where does over-enthusiastic salesmanship end and fraud begin? The Business of Information Technology provides rich opportunities for White-collar crime. The poor developer has his, or her, hands full with the task of wrestling with the sheer complexity of building an application. He, or she, has no time for following the complexities of the chicanery of the management that is directing affairs.  Most likely, the developers wouldn't even suspect that their company management had ulterior motives. I'll illustrate what I mean with an entirely fictional, hypothetical, example. The Opportunist and the Aged Charities often do good, unexciting work that is funded by the income from a bequest that dates back maybe hundreds of years.  In our example, it isn't exciting work, for it involves the welfare of elderly people who have fallen on hard times.  Volunteers visit, giving a smile and a chat, and check that they are all right, but are able to spend a little money on their discretion to ameliorate any pressing needs for these old folk.  The money is made to work very hard and the charity averts a great deal of suffering and eases the burden on the state. Daisy hears the garden gate creak as Mrs Rainer comes up the path. She looks forward to her twice-weekly visit from the nice lady from the trust. She always asked ‘is everything all right, Love’. Cheeky but nice. She likes her cheery manner. She seems interested in hearing her memories, and talking about her far-away family. She helps her with those chores in the house that she couldn’t manage and once even paid to fill the back-shed with coke, the other year. Nice, Mrs. Rainer is, she thought as she goes to open the door. The trustees are getting on in years themselves, and worry about the long-term future of the charity: is it relevant to modern society? Is it likely to attract a new generation of workers to take it on. They are instantly attracted by the arrival to the board of a smartly dressed University lecturer with the ear of the present Government. Alain 'Stalin' Jones is earnest, persuasive and energetic. The trustees welcome him to the board and quickly forgive his humorless political-correctness. He talks of 'diversity', 'relevance', 'social change', 'equality' and 'communities', but his eye is on that huge bequest. Alain first came to notice as a Trotskyite union official, who insinuated himself into one of the duller Trades Unions and turned it, through his passionate leadership, into a radical, headline-grabbing organization.  Middle age, and the rise of European federal socialism, had brought him quiet prosperity and charcoal suits, an ear in the current government, and a wide influence as a member of various Quangos (government bodies staffed by well-paid unelected courtiers).  He was employed as a 'consultant' by several organizations that relied on government contracts. After gaining the confidence of the trustees, and showing a surprising knowledge of mundane processes and the regulatory framework of charities, Alain launches his plan.  The trust will expand their work by means of a bold IT initiative that will coordinate the interventions of several 'caring agencies', and provide  emergency cover, a special Website so anxious relatives can see how their elderly charges are doing, and a vastly more efficient way of coordinating the work of the volunteer carers. It will also provide a special-purpose site that gives 'social networking' facilities, rather like Facebook, to the few elderly folk on the lists with access to the internet. The trustees perk up. Their own experience of the internet is restricted to the occasional scanning of railway timetables, but they can see that it is 'relevant'. In his next report to the other trustees, Alain proudly announces that all this glamorous and exciting technology can be paid for by a grant from the government. He admits darkly that he has influence. True to his word, the government promises a grant of a size that is an order of magnitude greater than any budget that the trustees had ever handled. There was the understandable proviso that the company that would actually do the IT work would have to be one of the government's preferred suppliers and the work would need to be tendered under EU competition rules. The only company that tenders, a multinational IT company with a long track record of government work, quotes ten million pounds for the work. A trustee questions the figure as it seems enormous for the reasonably trivial internet facilities being built, but the IT Salesmen dazzle them with presentations and three-letter acronyms until they subside into quiescent acceptance. After all, they can’t stay locked in the Twentieth century practices can they? The work is put in hand with a large project team, in a splendid glass building near west London. The trustees see rooms of programmers working diligently at screens, and who talk with enthusiasm of the project. Paul, the project manager, looked through his resource schedule with growing unease. His initial excitement at being given his first major project hadn’t lasted. He’d been allocated a lackluster team of developers whose skills didn’t seem right, and he was allowed only a couple of contractors to make good the deficit. Strangely, the presentation he’d given to his management, where he’d saved time and resources with a OTS solution to a great deal of the development work, and a sound conservative architecture, hadn’t gone down nearly as big as he’d hoped. He almost got the feeling they wanted a more radical and ambitious solution. The project starts slipping its dates. The costs build rapidly. There are certain uncomfortable extra charges that appear, such as the £600-a-day charge by the 'Business Manager' appointed to act as a point of liaison between the charity and the IT Company.  When he appeared, his face permanently split by a 'Mr Sincerity' smile, they'd thought he was provided at the cost of the IT Company. Derek, the DBA, didn’t have to go to the server room quite some much as he did: but It got him away from the poisonous despair of the development group. Wave after wave of events had conspired to delay the project.  Why the management had imposed hideous extra bureaucracy to cover ISO 9000 and 9001:2008 accreditation just as the project was struggling to get back on-schedule was  beyond belief.  Then  the Business manager was coming back with endless changes in scope, sorrowing saying that the Trustees were very insistent, though hopelessly out in touch with the reality of technical challenges. Suddenly, the costs mount to the point of consuming the government grant in its entirety. The project remains tantalizingly just out of reach. Alain Jones gives an emotional rallying speech at the trustees review meeting, urging them not to lose their nerve. Sadly, the trustees dip into the accumulated capital of the trust, the seed-corn of all their revenues, in order to save the IT project. A few months later it is all over. The IT project is never delivered, even though it had seemed so incredibly close.  With the trust's capital all gone, the activities it funded have to be terminated and the trust becomes just a shell. There aren't even the funds to mount a legal challenge against the IT company, even had the trust's solicitor advised such a foolish thing. Alain leaves as suddenly as he had arrived, only to pop up a few months later, bronzed and rested, at another charity. The IT workers who were permanent employees are dispersed to other projects, and the contractors leave to other contracts. Within months the entire project is but a vague memory. One or two developers remain  puzzled that their managers had been so obstructive when they should have welcomed progress toward completion of the project, but they put it down to incompetence and testosterone. Few suspected that they were actively preventing the project from getting finished. The relationships between the IT consultancy, and the government of the day are intricate, and made more complex by the Private Finance initiatives and political patronage.  The losers in this case were the taxpayers, and the beneficiaries of the trust, and, perhaps the soul of the original benefactor of the trust, whose bid to give his name some immortality had been scuppered by smooth-talking white-collar political apparatniks.  Even now, nobody is certain whether a crime was ever committed. The perfect heist, I guess. Where’s the victim? "I hear that Daisy’s cottage is up for sale. She’s had to go into a care home.  She didn’t want to at all, but then there is nobody to keep an eye on her since she had that minor stroke a while back.  A charity used to help out. The ‘social’ don’t have the funding, evidently for community care. Yes, her old cat was put down. There was a good clearout, and now the house is all scrubbed and cleared ready for sale. The skip was full of old photos and letters, memories. No room in her new ‘home’."

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  • 2d movement solution

    - by Phil
    Hi! I'm making a simple top-down tank game on the ipad where the user controls the movement of the tank with the left "joystick" and the rotation of the turret with the right one. I've spent several hours just trying to get it to work decently but now I turn to the pros :) I have two referencial objects, one for the movement and one for the rotation. The referencial objects always stay max two units away from the tank and I use them to tell the tank in what direction to move. I chose this approach to decouple movement and rotational behaviour from the raw input of the joysticks, I believe this will make it simpler to implement whatever behaviour I want for the tank. My problem is 1; the turret rotates the long way to the target. With this I mean that the target can be -5 degrees away in rotation and still it rotates 355 degrees instead of -5 degrees. I can't figure out why. The other problem is with the movement. It just doesn't feel right to have the tank turn while moving. I'd like to have a solution that would work as well for the AI as for the player. A blackbox function for the movement where the player only specifies in what direction it should move and it moves there under the constraints that are imposed on it. I am using the standard joystick class found in the Unity iPhone package. This is the code I'm using for the movement: public class TankFollow : MonoBehaviour { //Check angle difference and turn accordingly public GameObject followPoint; public float speed; public float turningSpeed; void Update() { transform.position = Vector3.Slerp(transform.position, followPoint.transform.position, speed * Time.deltaTime); //Calculate angle var forwardA = transform.forward; var forwardB = (followPoint.transform.position - transform.position); var angleA = Mathf.Atan2(forwardA.x, forwardA.z) * Mathf.Rad2Deg; var angleB = Mathf.Atan2(forwardB.x, forwardB.z) * Mathf.Rad2Deg; var angleDiff = Mathf.DeltaAngle(angleA, angleB); //print(angleDiff.ToString()); if (angleDiff > 5) { //Rotate to transform.Rotate(new Vector3(0, (-turningSpeed * Time.deltaTime),0)); //transform.rotation = new Quaternion(transform.rotation.x, transform.rotation.y + adjustment, transform.rotation.z, transform.rotation.w); } else if (angleDiff < 5) { transform.Rotate(new Vector3(0, (turningSpeed * Time.deltaTime),0)); //transform.rotation = new Quaternion(transform.rotation.x, transform.rotation.y + adjustment, transform.rotation.z, transform.rotation.w); } else { } transform.position = new Vector3(transform.position.x, 0, transform.position.z); } } And this is the code I'm using to rotate the turret: void LookAt() { var forwardA = -transform.right; var forwardB = (toLookAt.transform.position - transform.position); var angleA = Mathf.Atan2(forwardA.x, forwardA.z) * Mathf.Rad2Deg; var angleB = Mathf.Atan2(forwardB.x, forwardB.z) * Mathf.Rad2Deg; var angleDiff = Mathf.DeltaAngle(angleA, angleB); //print(angleDiff.ToString()); if (angleDiff - 180 > 1) { //Rotate to transform.Rotate(new Vector3(0, (turretSpeed * Time.deltaTime),0)); //transform.rotation = new Quaternion(transform.rotation.x, transform.rotation.y + adjustment, transform.rotation.z, transform.rotation.w); } else if (angleDiff - 180 < -1) { transform.Rotate(new Vector3(0, (-turretSpeed * Time.deltaTime),0)); //transform.rotation = new Quaternion(transform.rotation.x, transform.rotation.y + adjustment, transform.rotation.z, transform.rotation.w); print((angleDiff - 180).ToString()); } else { } } Since I want the turret reference point to turn in relation to the tank (when you rotate the body, the turret should follow and not stay locked on since it makes it impossible to control when you've got two thumbs to work with), I've made the TurretFollowPoint a child of the Turret object, which in turn is a child of the body. I'm thinking that I'm making it too difficult for myself with the reference points but I'm imagining that it's a good idea. Please be honest about this point. So I'll be grateful for any help I can get! I'm using Unity3d iPhone. Thanks!

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  • Spolskism or Twitterism: A Doctor writes...

    - by Phil Factor
    "I never realized I had a problem. I just 'twittered' because it was a social thing to do. All my mates were doing it. It made me feel good to have 'followers'; it bolstered my self-esteem. Of course, you don't think of the long-term effects on your work and on the way you think. There's no denying that it impairs your judgment…" Yes, this story is typical. Hundreds of people are waking up to the long term effects of twittering, and seeking help. Dave, who wishes to remain anonymous, told our reporter… "I started using Twitter at work. Just a few minutes now and then, throughout the day. A lot of my colleagues were doing it and I thought 'Well, that's cool; it must be part of what I should be doing at work'. Soon, I was avidly reading every twitter that came my way, and counting the minutes between my own twitters. I tried to kid myself that it was all about professional development and getting other people to help you with work-related problems, but in truth I had become addicted to the buzz of the social network. The worse thing was that it made me seem busy even when I was really just frittering my time away. Inevitably, I started to get behind with my real work." Experts have identified the syndrome and given it a name: 'Twitterism', sometimes referred to as 'Spolskism', after the person who first drew attention to the pernicious damage to well-being that the practice caused, and who had the courage to take the pledge of rejecting it. According to one expert… "The occasional Twitter does little harm to the participant, and can be an adaptive way of dealing with stress. Unfortunately, it rarely stops there. The addictive qualities of the practice have put a strain on the caring professions who are faced with a flood of people making that first bold step to seeking help". Dave is one of those now seeking help for his addiction… "I had lost touch with reality. Even though I twittered my work colleagues constantly, I found I actually spoke to them less and less. Even when out socializing, I would frequently disengage from the conversation, in order to twitter. I stopped blogging. I stopped responding to emails; the only way to reach me was through the world of Twitter. Unfortunately, my denial about the harm that twittering was doing to me, my friends, and my work-colleagues was so strong that I truly couldn't see that I had a problem." Like other addictions, the help and support of others who are 'taking the cure' is important. There is a common bond between those who have 'been through hell and back' and are once more able to experience the joys of actually conversing and socializing, rather than the false comfort of solitary 'twittering'. Complete abstinence is essential to the cure. Most of those who risk even an occasional twitter face a headlong slide back into 'binge' twittering. Tom, another twitterer who has managed to kick the habit explains… "My twittering addiction now seems more like a bad dream. You get to work, and switch on the PC. You say to yourself, just open up the browser, just for a minute, just to see what people are saying on Twitter. The next thing you know, half the day has gone by. The worst thing is that when you're addicted, you get good at covering up the habit; I spent so much time looking at the screen and typing on the keyboard, people just assumed I was working hard.I know that I must never forget what it was like then, and what it's like now that I've kicked the habit. I now have more time for productive work and a real social life." Like many addictions, Spolskism has its most detrimental effects on family, friends and workmates, rather than the addict. So often nowadays, we hear the sad stories of Twitter-Widows; tales of long lonely evenings spent whilst their partners are engrossed in their twittering into their 'mobiles' or indulging in their solitary spolskistic habits in privacy, under cover of 'having to do work at home'. Workmates suffer too, when the addicts even take their laptops or mobiles into meetings in order to 'twitter' with their fellow obsessives, even stooping to complain to their followers how boring the meeting is. No; The best advice is to leave twittering to the birds. You know it makes sense.

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  • Exitus Acta Probat: The Post-Processing Module

    - by Phil Factor
    Sometimes, one has to make certain ethical compromises to ensure the success of a corporate IT project. Exitus Acta Probat (literally 'the result validates the deeds' meaning that the ends justify the means)It was a while back, whilst working as a Technical Architect for a well-known international company, that I was given the task of designing the architecture of a rather specialized accounting system. We'd tried an off-the-shelf (OTS) Windows-based solution which crashed with dispiriting regularity, and didn't quite do what the business required. After a great deal of research and planning, we commissioned a Unux-based system that used X-terminals for the desktops of  the participating staff. X terminals are now obsolete, but were then hot stuff; stripped-down Unix workstations that provided client GUIs for networked applications long before the days of AJAX, Flash, Air and DHTML. I've never known a project go so smoothly: I'd been initially rather nervous about going the Unix route, believing then that  Unix programmers were excitable creatures who were prone to  indulge in role-play enactments of elves and wizards at the weekend, but the programmers I met from the company that did the work seemed to be rather donnish, earnest, people who quickly grasped our requirements and were faultlessly professional in their work.After thinking lofty thoughts for a while, there was considerable pummeling of keyboards by our suppliers, and a beautiful robust application was delivered to us ahead of dates.Soon, the department who had commissioned the work received shiny new X Terminals to replace their rather depressing lavatory-beige PCs. I modestly hung around as the application was commissioned and deployed to the department in order to receive the plaudits. They didn't come. Something was very wrong with the project. I couldn't put my finger on the problem, and the users weren't doing any more than desperately and futilely searching the application to find a fault with it.Many times in my life, I've come up against a predicament like this: The roll-out of an application goes wrong and you are hearing nothing that helps you to discern the cause but nit-*** noise. There is a limit to the emotional heat you can pack into a complaint about text being in the wrong font, or an input form being slightly cramped, but they tried their best. The answer is, of course, one that every IT executive should have tattooed prominently where they can read it in emergencies: In Vino Veritas (literally, 'in wine the truth', alcohol loosens the tongue. A roman proverb) It was time to slap the wallet and get the department down the pub with the tab in my name. It was an eye-watering investment, but hedged with an over-confident IT director who relished my discomfort. To cut a long story short, The real reason gushed out with the third round. We had deprived them of their PCs, which had been good for very little from the pure business perspective, but had provided them with many hours of happiness playing computer-based minesweeper and solitaire. There is no more agreeable way of passing away the interminable hours of wage-slavery than minesweeper or solitaire, and the employees had applauded the munificence of their employer who had provided them with the means to play it. I had, unthinkingly, deprived them of it.I held an emergency meeting with our suppliers the following day. I came over big with the notion that it was in their interests to provide a solution. They played it cool, probably knowing that it was my head on the block, not theirs. In the end, they came up with a compromise. they would temporarily descend from their lofty, cerebral stamping grounds  in order to write a server-based Minesweeper and Solitaire game for X Terminals, and install it in a concealed place within the system. We'd have to pay for it, though. I groaned. How could we do that? "Could we call it a 'post-processing module?" suggested their account executive.And so it came to pass. The application was a resounding success. Every now and then, the staff were able to indulge in some 'post-processing', with what turned out to be a very fine implementation of both minesweeper and solitaire. There were several refinements: A single click in a 'boss' button turned the games into what looked just like a financial spreadsheet.  They even threw in a multi-user version of Battleships. The extra payment for the post-processing module went through the change-control process without anyone untoward noticing, and peace once more descended. Only one thing niggles. Those games were good. Do they still survive, somewhere in a Linux library? If so, I'd like to claim a small part in their production.

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  • 2d tank movement and turret solution

    - by Phil
    Hi! I'm making a simple top-down tank game on the ipad where the user controls the movement of the tank with the left "joystick" and the rotation of the turret with the right one. I've spent several hours just trying to get it to work decently but now I turn to the pros :) I have two referencial objects, one for the movement and one for the rotation. The referencial objects always stay max two units away from the tank and I use them to tell the tank in what direction to move. I chose this approach to decouple movement and rotational behaviour from the raw input of the joysticks, I believe this will make it simpler to implement whatever behaviour I want for the tank. My problem is 1; the turret rotates the long way to the target. With this I mean that the target can be -5 degrees away in rotation and still it rotates 355 degrees instead of -5 degrees. I can't figure out why. The other problem is with the movement. It just doesn't feel right to have the tank turn while moving. I'd like to have a solution that would work as well for the AI as for the player. A blackbox function for the movement where the player only specifies in what direction it should move and it moves there under the constraints that are imposed on it. I am using the standard joystick class found in the Unity iPhone package. This is the code I'm using for the movement: public class TankFollow : MonoBehaviour { //Check angle difference and turn accordingly public GameObject followPoint; public float speed; public float turningSpeed; void Update() { transform.position = Vector3.Slerp(transform.position, followPoint.transform.position, speed * Time.deltaTime); //Calculate angle var forwardA = transform.forward; var forwardB = (followPoint.transform.position - transform.position); var angleA = Mathf.Atan2(forwardA.x, forwardA.z) * Mathf.Rad2Deg; var angleB = Mathf.Atan2(forwardB.x, forwardB.z) * Mathf.Rad2Deg; var angleDiff = Mathf.DeltaAngle(angleA, angleB); //print(angleDiff.ToString()); if (angleDiff > 5) { //Rotate to transform.Rotate(new Vector3(0, (-turningSpeed * Time.deltaTime),0)); //transform.rotation = new Quaternion(transform.rotation.x, transform.rotation.y + adjustment, transform.rotation.z, transform.rotation.w); } else if (angleDiff < 5) { transform.Rotate(new Vector3(0, (turningSpeed * Time.deltaTime),0)); //transform.rotation = new Quaternion(transform.rotation.x, transform.rotation.y + adjustment, transform.rotation.z, transform.rotation.w); } else { } transform.position = new Vector3(transform.position.x, 0, transform.position.z); } } And this is the code I'm using to rotate the turret: void LookAt() { var forwardA = -transform.right; var forwardB = (toLookAt.transform.position - transform.position); var angleA = Mathf.Atan2(forwardA.x, forwardA.z) * Mathf.Rad2Deg; var angleB = Mathf.Atan2(forwardB.x, forwardB.z) * Mathf.Rad2Deg; var angleDiff = Mathf.DeltaAngle(angleA, angleB); //print(angleDiff.ToString()); if (angleDiff - 180 > 1) { //Rotate to transform.Rotate(new Vector3(0, (turretSpeed * Time.deltaTime),0)); //transform.rotation = new Quaternion(transform.rotation.x, transform.rotation.y + adjustment, transform.rotation.z, transform.rotation.w); } else if (angleDiff - 180 < -1) { transform.Rotate(new Vector3(0, (-turretSpeed * Time.deltaTime),0)); //transform.rotation = new Quaternion(transform.rotation.x, transform.rotation.y + adjustment, transform.rotation.z, transform.rotation.w); print((angleDiff - 180).ToString()); } else { } } Since I want the turret reference point to turn in relation to the tank (when you rotate the body, the turret should follow and not stay locked on since it makes it impossible to control when you've got two thumbs to work with), I've made the TurretFollowPoint a child of the Turret object, which in turn is a child of the body. I'm thinking that I'm making it too difficult for myself with the reference points but I'm imagining that it's a good idea. Please be honest about this point. So I'll be grateful for any help I can get! I'm using Unity3d iPhone. Thanks!

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  • Best approach for unit enemy "awareness" in RTS?

    - by Phil
    I'm using Unity3d to develop an RTS/TD hybrid prototype game. What is the best approach to have "awareness" between units and their enemies? Is it sane to have every unit check the distance to every enemy and engage if within range? The approach I'm going for right now is to have a trigger sphere on every unit. If an enemy enters the trigger, the unit becomes aware of the enemy and starts distance checking. I'm imagining that this would save some unnecessary checks? What's the best practice here (if there's such a thing)? Thanks for reading.

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  • How to code Umbraco XSLT to retrieve Nodes from unrelated tree

    - by Phil.Wheeler
    I have an Umbraco site for personal use that I want to also use as a blog. I'm trying to put together the XSLT to grab the top three posts from the nodes in the Blog tree (node id = 1063) and display these on a tab page that is incorporated into the front page. The following image illustrates the node hierarchy: With my extremely limited appreciation of XSLT, I'm unable to grab the node ID of the "Blog" id and take the 3 pages below that to display in the "Top Posts" part of my site which is found under the "Frontpage Tabs" node. All the examples I find work with the "current page", which is typically the top-level node, "Personal Site". How should I accomplish this?

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  • How do I stop XNA/Visual Studio from rebuilding my content project every time I build?

    - by Phil Quinn
    My group and I are working on a game in XNA 4.0 with Visual Studio 2010/2012. The main solution has 6 projects: 2 XNA game projects (1 executable/ 1 class library), 1 WPF executable for the level editor, 2 standard class libraries, and a content project. Originally, the editor and engine XNA game projects had a content reference to separate content projects. Recently, I consolidated the content projects into one to simplify asset additions. Since pushing these changes to our git repo, certain members of my group have been experiencing weird build issues. Every time they run the project, they have to re-build all of the assets. This happens regardless of whether any changes were made, even if they just run the project directly after building. I've taken a few steps to figure out why this is happening. Below is the MSBuild output set on Normal verbosity. The seemingly important part is at 4, with the line 4> Rebuilding all content because build settings have changed 1>------ Build started: Project: Engine.Core, Configuration: Debug x86 ------ 1>Build started 11/29/2012 3:24:24 AM. 1>ResolveAssemblyReferences: 1> A TargetFramework profile exclusion list will be generated. 1>EmbedXnaFrameworkRuntimeProfile: 1>Skipping target "EmbedXnaFrameworkRuntimeProfile" because all output files are up-to-date with respect to the input files. 1>GenerateTargetFrameworkMonikerAttribute: 1>Skipping target "GenerateTargetFrameworkMonikerAttribute" because all output files are up-to-date with respect to the input files. 1>CoreCompile: 1>Skipping target "CoreCompile" because all output files are up-to-date with respect to the input files. 1>XnaWriteCacheFile: 1>Skipping target "XnaWriteCacheFile" because all output files are up-to-date with respect to the input files. 1>_CopyOutOfDateSourceItemsToOutputDirectoryAlways: 1> Copying file from "<solution-dir>\src\Engine.Core\DialoguePrototypeTestDB.s3db" to "bin\x86\Debug\DialoguePrototypeTestDB.s3db". 1>_CopyAppConfigFile: 1>Skipping target "_CopyAppConfigFile" because all output files are up-to-date with respect to the input files. 1>CopyFilesToOutputDirectory: 1> Engine.Core -> <solution-dir>\src\Engine.Core\bin\x86\Debug\TimeSink.Engine.Core.dll 1> 1>Build succeeded. 1> 1>Time Elapsed 00:00:00.13 2>------ Build started: Project: TimeSink.Entities, Configuration: Debug x86 ------ 2>Build started 11/29/2012 3:24:25 AM. 2>ResolveAssemblyReferences: 2> A TargetFramework profile exclusion list will be generated. 2>EmbedXnaFrameworkRuntimeProfile: 2>Skipping target "EmbedXnaFrameworkRuntimeProfile" because all output files are up-to-date with respect to the input files. 2>GenerateTargetFrameworkMonikerAttribute: 2>Skipping target "GenerateTargetFrameworkMonikerAttribute" because all output files are up-to-date with respect to the input files. 2>CoreCompile: 2>Skipping target "CoreCompile" because all output files are up-to-date with respect to the input files. 2>XnaWriteCacheFile: 2>Skipping target "XnaWriteCacheFile" because all output files are up-to-date with respect to the input files. 2>_CopyOutOfDateSourceItemsToOutputDirectoryAlways: 2> Copying file from "<solution-dir>\src\Engine.Core\DialoguePrototypeTestDB.s3db" to "bin\x86\Debug\DialoguePrototypeTestDB.s3db". 2>CopyFilesToOutputDirectory: 2> TimeSink.Entities -> <solution-dir>\src\TimeSink.Entities\bin\x86\Debug\TimeSink.Entities.dll 2> 2>Build succeeded. 2> 2>Time Elapsed 00:00:00.11 3>------ Build started: Project: Editor (Editor\Editor), Configuration: Debug x86 ------ 4>------ Build started: Project: Engine.Game, Configuration: Debug x86 ------ 3>Build started 11/29/2012 3:24:25 AM. 3>CoreCompile: 3> All content is already up to date 3>ResolveAssemblyReferences: 3> A TargetFramework profile exclusion list will be generated. 3>EmbedXnaFrameworkRuntimeProfile: 3>Skipping target "EmbedXnaFrameworkRuntimeProfile" because all output files are up-to-date with respect to the input files. 3>GenerateTargetFrameworkMonikerAttribute: 3>Skipping target "GenerateTargetFrameworkMonikerAttribute" because all output files are up-to-date with respect to the input files. 3>CoreCompile: 3>Skipping target "CoreCompile" because all output files are up-to-date with respect to the input files. 3>XnaWriteCacheFile: 3>Skipping target "XnaWriteCacheFile" because all output files are up-to-date with respect to the input files. 3>_CopyOutOfDateSourceItemsToOutputDirectoryAlways: 3> Copying file from "<solution-dir>\src\Engine.Core\DialoguePrototypeTestDB.s3db" to "bin\x86\Debug\DialoguePrototypeTestDB.s3db". 3>_CopyOutOfDateNestedContentItemsToOutputDirectory: 3>Skipping target "_CopyOutOfDateNestedContentItemsToOutputDirectory" because all output files are up-to-date with respect to the input files. 3>CopyFilesToOutputDirectory: 3> Editor -> <solution-dir>\src\Editor\Editor\bin\x86\Debug\Editor.dll 3> 3>Build succeeded. 3> 3>Time Elapsed 00:00:00.39 4>Build started 11/29/2012 3:24:25 AM. 4>CoreCompile: 4> Rebuilding all content because build settings have changed 4> Building Textures\circle.png -> <solution-dir>\src\Engine.Game\Engine.Game\bin\x86\Debug\Content\Textures\circle.xnb 4> Importing Textures\circle.png with Microsoft.Xna.Framework.Content.Pipeline.TextureImporter 4> Processing Textures\circle.png with Microsoft.Xna.Framework.Content.Pipeline.Processors.TextureProcessor 4> Compiling <solution-dir>\src\Engine.Game\Engine.Game\bin\x86\Debug\Content\Textures\circle.xnb 4> Building Textures\giroux.png -> <solution-dir>\src\Engine.Game\Engine.Game\bin\x86\Debug\Content\Textures\giroux.xnb 4> Importing Textures\giroux.png with Microsoft.Xna.Framework.Content.Pipeline.TextureImporter 4> Processing Textures\giroux.png with Microsoft.Xna.Framework.Content.Pipeline.Processors.TextureProcessor 4> Compiling <solution-dir>\src\Engine.Game\Engine.Game\bin\x86\Debug\Content\Textures\giroux.xnb 4> Building Textures\Body_Neutral.png -> <solution-dir>\src\Engine.Game\Engine.Game\bin\x86\Debug\Content\Textures\Body_Neutral.xnb 4> Importing Textures\Body_Neutral.png with Microsoft.Xna.Framework.Content.Pipeline.TextureImporter 4> Processing Textures\Body_Neutral.png with Microsoft.Xna.Framework.Content.Pipeline.Processors.TextureProcessor 4> Compiling <solution-dir>\src\Engine.Game\Engine.Game\bin\x86\Debug\Content\Textures\Body_Neutral.xnb 4> Building font.spritefont -> <solution-dir>\src\Engine.Game\Engine.Game\bin\x86\Debug\Content\font.xnb 4> Importing font.spritefont with Microsoft.Xna.Framework.Content.Pipeline.FontDescriptionImporter 4> Processing font.spritefont with Microsoft.Xna.Framework.Content.Pipeline.Processors.FontDescriptionProcessor 4> Compiling <solution-dir>\src\Engine.Game\Engine.Game\bin\x86\Debug\Content\font.xnb 4>ResolveAssemblyReferences: 4> A TargetFramework profile exclusion list will be generated. 4>EmbedXnaFrameworkRuntimeProfile: 4>Skipping target "EmbedXnaFrameworkRuntimeProfile" because all output files are up-to-date with respect to the input files. 4>GenerateTargetFrameworkMonikerAttribute: 4>Skipping target "GenerateTargetFrameworkMonikerAttribute" because all output files are up-to-date with respect to the input files. 4>CoreCompile: 4>Skipping target "CoreCompile" because all output files are up-to-date with respect to the input files. 4>_CopyOutOfDateSourceItemsToOutputDirectoryAlways: 4> Copying file from "<solution-dir>\src\Engine.Core\DialoguePrototypeTestDB.s3db" to "bin\x86\Debug\DialoguePrototypeTestDB.s3db". 4>_CopyOutOfDateNestedContentItemsToOutputDirectory: 4>Skipping target "_CopyOutOfDateNestedContentItemsToOutputDirectory" because all output files are up-to-date with respect to the input files. 4>_CopyAppConfigFile: 4>Skipping target "_CopyAppConfigFile" because all output files are up-to-date with respect to the input files. 4>CopyFilesToOutputDirectory: 4> Engine.Game -> <solution-dir>\src\Engine.Game\Engine.Game\bin\x86\Debug\Engine.Game.exe 4>IncrementalClean: 4> Deleting file "<solution-dir>\src\Engine.Game\Engine.Game\bin\x86\Debug\circle.xnb". 4> Deleting file "<solution-dir>\src\Engine.Game\Engine.Game\bin\x86\Debug\giroux.xnb". 4> Deleting file "<solution-dir>\src\Engine.Game\Engine.Game\bin\x86\Debug\Body_Neutral.xnb". 4> Deleting file "<solution-dir>\src\Engine.Game\Engine.Game\bin\x86\Debug\font.xnb". 4> 4>Build succeeded. 4> 4>Time Elapsed 00:00:01.72 ========== Build: 4 succeeded, 0 failed, 1 up-to-date, 0 skipped ========== I can't think of how build settings could change between consecutive executions. Like I said, this only happens for half our group. One member is on a 32-bit Windows 7 Prof bootcamp partition on a Mac. Everyone else, including those who don't have the issue, are running straight 64-bit Windows 7 Prof. Both have tried using VS 2010 and VS 2012. Any insight would be greatly appreciated. Also, I can post more details upon request if this isn't thorough enough.

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  • How to manage a multiplayer asynchronous environment in a game

    - by Phil
    I'm working on a game where players can setup villages, which can contain defending units. Any of these units (each on their own tiles) can be set to "campaign" which means they are no longer defending but can now be used to attack other villages. And each unit on a tile can have up to a 100 health. So far so good. Oh and it's all asynchronous so even though the server will be aware that your village is being attacked, you won't be until the attack is over. The issue I'm struggling with, is the following situation. Let's say a unit on a tile is being attacked by a player from another village. The other player see's your village and is attacking your units. You don't know this is happening though, so you set your unit to campaign and off you go to attack another village, with the unit which itself is actually being attacked by this other player. The other player stops attacking your village and leaves your unit with say a health of 1, which is then saved to the server. You however have this same unit are attacking another village with it, but now you discover that even though it started off with a 100 health, now mysteriously it only has 1... Solutions? Ideas? Edit The simplest solutions are often the best. I referred to Clash of clans below, well after a bit more digging it seems that in CoC you can only attack players that are offline! ha, that almost solves the problem. I say almost because there's still the situation where a players village could be in the process of being attacked when they come back online, still need to address that. Edit 2 A solution to the "What happens when a player is attacking your village and you come online" issue, could be the attacking player just get's kicked out of the village at that point and just get's whatever they had won up to that point, it's a bit of a fudge but it might work.

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  • Table Variables: an empirical approach.

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

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  • Curing the Database-Application mismatch

    - by Phil Factor
    If an application requires access to a database, then you have to be able to deploy it so as to be version-compatible with the database, in phase. If you can deploy both together, then the application and database must normally be deployed at the same version in which they, together, passed integration and functional testing.  When a single database supports more than one application, then the problem gets more interesting. I’ll need to be more precise here. It is actually the application-interface definition of the database that needs to be in a compatible ‘version’.  Most databases that get into production have no separate application-interface; in other words they are ‘close-coupled’.  For this vast majority, the whole database is the application-interface, and applications are free to wander through the bowels of the database scot-free.  If you’ve spurned the perceived wisdom of application architects to have a defined application-interface within the database that is based on views and stored procedures, any version-mismatch will be as sensitive as a kitten.  A team that creates an application that makes direct access to base tables in a database will have to put a lot of energy into keeping Database and Application in sync, to say nothing of having to tackle issues such as security and audit. It is not the obvious route to development nirvana. I’ve been in countless tense meetings with application developers who initially bridle instinctively at the apparent restrictions of being ‘banned’ from the base tables or routines of a database.  There is no good technical reason for needing that sort of access that I’ve ever come across.  Everything that the application wants can be delivered via a set of views and procedures, and with far less pain for all concerned: This is the application-interface.  If more than zero developers are creating a database-driven application, then the project will benefit from the loose-coupling that an application interface brings. What is important here is that the database development role is separated from the application development role, even if it is the same developer performing both roles. The idea of an application-interface with a database is as old as I can remember. The big corporate or government databases generally supported several applications, and there was little option. When a new application wanted access to an existing corporate database, the developers, and myself as technical architect, would have to meet with hatchet-faced DBAs and production staff to work out an interface. Sure, they would talk up the effort involved for budgetary reasons, but it was routine work, because it decoupled the database from its supporting applications. We’d be given our own stored procedures. One of them, I still remember, had ninety-two parameters. All database access was encapsulated in one application-module. If you have a stable defined application-interface with the database (Yes, one for each application usually) you need to keep the external definitions of the components of this interface in version control, linked with the application source,  and carefully track and negotiate any changes between database developers and application developers.  Essentially, the application development team owns the interface definition, and the onus is on the Database developers to implement it and maintain it, in conformance.  Internally, the database can then make all sorts of changes and refactoring, as long as source control is maintained.  If the application interface passes all the comprehensive integration and functional tests for the particular version they were designed for, nothing is broken. Your performance-testing can ‘hang’ on the same interface, since databases are judged on the performance of the application, not an ‘internal’ database process. The database developers have responsibility for maintaining the application-interface, but not its definition,  as they refactor the database. This is easily tested on a daily basis since the tests are normally automated. In this setting, the deployment can proceed if the more stable application-interface, rather than the continuously-changing database, passes all tests for the version of the application. Normally, if all goes well, a database with a well-designed application interface can evolve gracefully without changing the external appearance of the interface, and this is confirmed by integration tests that check the interface, and which hopefully don’t need to be altered at all often.  If the application is rapidly changing its ‘domain model’  in the light of an increased understanding of the application domain, then it can change the interface definitions and the database developers need only implement the interface rather than refactor the underlying database.  The test team will also have to redo the functional and integration tests which are, of course ‘written to’ the definition.  The Database developers will find it easier if these tests are done before their re-wiring  job to implement the new interface. If, at the other extreme, an application receives no further development work but survives unchanged, the database can continue to change and develop to keep pace with the requirements of the other applications it supports, and needs only to take care that the application interface is never broken. Testing is easy since your automated scripts to test the interface do not need to change. The database developers will, of course, maintain their own source control for the database, and will be likely to maintain versions for all major releases. However, this will not need to be shared with the applications that the database servers. On the other hand, the definition of the application interfaces should be within the application source. Changes in it have to be subject to change-control procedures, as they will require a chain of tests. Once you allow, instead of an application-interface, an intimate relationship between application and database, we are in the realms of impedance mismatch, over and above the obvious security problems.  Part of this impedance problem is a difference in development practices. Whereas the application has to be regularly built and integrated, this isn’t necessarily the case with the database.  An RDBMS is inherently multi-user and self-integrating. If the developers work together on the database, then a subsequent integration of the database on a staging server doesn’t often bring nasty surprises. A separate database-integration process is only needed if the database is deliberately built in a way that mimics the application development process, but which hampers the normal database-development techniques.  This process is like demanding a official walking with a red flag in front of a motor car.  In order to closely coordinate databases with applications, entire databases have to be ‘versioned’, so that an application version can be matched with a database version to produce a working build without errors.  There is no natural process to ‘version’ databases.  Each development project will have to define a system for maintaining the version level. A curious paradox occurs in development when there is no formal application-interface. When the strains and cracks happen, the extra meetings, bureaucracy, and activity required to maintain accurate deployments looks to IT management like work. They see activity, and it looks good. Work means progress.  Management then smile on the design choices made. In IT, good design work doesn’t necessarily look good, and vice versa.

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  • Sniffing out SQL Code Smells: Inconsistent use of Symbolic names and Datatypes

    - by Phil Factor
    It is an awkward feeling. You’ve just delivered a database application that seems to be working fine in production, and you just run a few checks on it. You discover that there is a potential bug that, out of sheer good chance, hasn’t kicked in to produce an error; but it lurks, like a smoking bomb. Worse, maybe you find that the bug has started its evil work of corrupting the data, but in ways that nobody has, so far detected. You investigate, and find the damage. You are somehow going to have to repair it. Yes, it still very occasionally happens to me. It is not a nice feeling, and I do anything I can to prevent it happening. That’s why I’m interested in SQL code smells. SQL Code Smells aren’t necessarily bad practices, but just show you where to focus your attention when checking an application. Sometimes with databases the bugs can be subtle. SQL is rather like HTML: the language does its best to try to carry out your wishes, rather than to be picky about your bugs. Most of the time, this is a great benefit, but not always. One particular place where this can be detrimental is where you have implicit conversion between different data types. Most of the time it is completely harmless but we’re  concerned about the occasional time it isn’t. Let’s give an example: String truncation. Let’s give another even more frightening one, rounding errors on assignment to a number of different precision. Each requires a blog-post to explain in detail and I’m not now going to try. Just remember that it is not always a good idea to assign data to variables, parameters or even columns when they aren’t the same datatype, especially if you are relying on implicit conversion to work its magic.For details of the problem and the consequences, see here:  SR0014: Data loss might occur when casting from {Type1} to {Type2} . For any experienced Database Developer, this is a more frightening read than a Vampire Story. This is why one of the SQL Code Smells that makes me edgy, in my own or other peoples’ code, is to see parameters, variables and columns that have the same names and different datatypes. Whereas quite a lot of this is perfectly normal and natural, you need to check in case one of two things have gone wrong. Either sloppy naming, or mixed datatypes. Sure it is hard to remember whether you decided that the length of a log entry was 80 or 100 characters long, or the precision of a number. That is why a little check like this I’m going to show you is excellent for tidying up your code before you check it back into source Control! 1/ Checking Parameters only If you were just going to check parameters, you might just do this. It simply groups all the parameters, either input or output, of all the routines (e.g. stored procedures or functions) by their name and checks to see, in the HAVING clause, whether their data types are all the same. If not, it lists all the examples and their origin (the routine) Even this little check can occasionally be scarily revealing. ;WITH userParameter AS  ( SELECT   c.NAME AS ParameterName,  OBJECT_SCHEMA_NAME(c.object_ID) + '.' + OBJECT_NAME(c.object_ID) AS ObjectName,  t.name + ' '     + CASE     --we may have to put in the length            WHEN t.name IN ('char', 'varchar', 'nchar', 'nvarchar')             THEN '('               + CASE WHEN c.max_length = -1 THEN 'MAX'                ELSE CONVERT(VARCHAR(4),                    CASE WHEN t.name IN ('nchar', 'nvarchar')                      THEN c.max_length / 2 ELSE c.max_length                    END)                END + ')'         WHEN t.name IN ('decimal', 'numeric')             THEN '(' + CONVERT(VARCHAR(4), c.precision)                   + ',' + CONVERT(VARCHAR(4), c.Scale) + ')'         ELSE ''      END  --we've done with putting in the length      + CASE WHEN XML_collection_ID <> 0         THEN --deal with object schema names             '(' + CASE WHEN is_XML_Document = 1                    THEN 'DOCUMENT '                    ELSE 'CONTENT '                   END              + COALESCE(               (SELECT QUOTENAME(ss.name) + '.' + QUOTENAME(sc.name)                FROM sys.xml_schema_collections sc                INNER JOIN Sys.Schemas ss ON sc.schema_ID = ss.schema_ID                WHERE sc.xml_collection_ID = c.XML_collection_ID),'NULL') + ')'          ELSE ''         END        AS [DataType]  FROM sys.parameters c  INNER JOIN sys.types t ON c.user_Type_ID = t.user_Type_ID  WHERE OBJECT_SCHEMA_NAME(c.object_ID) <> 'sys'   AND parameter_id>0)SELECT CONVERT(CHAR(80),objectName+'.'+ParameterName),DataType FROM UserParameterWHERE ParameterName IN   (SELECT ParameterName FROM UserParameter    GROUP BY ParameterName    HAVING MIN(Datatype)<>MAX(DataType))ORDER BY ParameterName   so, in a very small example here, we have a @ClosingDelimiter variable that is only CHAR(1) when, by the looks of it, it should be up to ten characters long, or even worse, a function that should be a char(1) and seems to let in a string of ten characters. Worth investigating. Then we have a @Comment variable that can't decide whether it is a VARCHAR(2000) or a VARCHAR(MAX) 2/ Columns and Parameters Actually, once we’ve cleared up the mess we’ve made of our parameter-naming in the database we’re inspecting, we’re going to be more interested in listing both columns and parameters. We can do this by modifying the routine to list columns as well as parameters. Because of the slight complexity of creating the string version of the datatypes, we will create a fake table of both columns and parameters so that they can both be processed the same way. After all, we want the datatypes to match Unfortunately, parameters do not expose all the attributes we are interested in, such as whether they are nullable (oh yes, subtle bugs happen if this isn’t consistent for a datatype). We’ll have to leave them out for this check. Voila! A slight modification of the first routine ;WITH userObject AS  ( SELECT   Name AS DataName,--the actual name of the parameter or column ('@' removed)  --and the qualified object name of the routine  OBJECT_SCHEMA_NAME(ObjectID) + '.' + OBJECT_NAME(ObjectID) AS ObjectName,  --now the harder bit: the definition of the datatype.  TypeName + ' '     + CASE     --we may have to put in the length. e.g. CHAR (10)           WHEN TypeName IN ('char', 'varchar', 'nchar', 'nvarchar')             THEN '('               + CASE WHEN MaxLength = -1 THEN 'MAX'                ELSE CONVERT(VARCHAR(4),                    CASE WHEN TypeName IN ('nchar', 'nvarchar')                      THEN MaxLength / 2 ELSE MaxLength                    END)                END + ')'         WHEN TypeName IN ('decimal', 'numeric')--a BCD number!             THEN '(' + CONVERT(VARCHAR(4), Precision)                   + ',' + CONVERT(VARCHAR(4), Scale) + ')'         ELSE ''      END  --we've done with putting in the length      + CASE WHEN XML_collection_ID <> 0 --tush tush. XML         THEN --deal with object schema names             '(' + CASE WHEN is_XML_Document = 1                    THEN 'DOCUMENT '                    ELSE 'CONTENT '                   END              + COALESCE(               (SELECT TOP 1 QUOTENAME(ss.name) + '.' + QUOTENAME(sc.Name)                FROM sys.xml_schema_collections sc                INNER JOIN Sys.Schemas ss ON sc.schema_ID = ss.schema_ID                WHERE sc.xml_collection_ID = XML_collection_ID),'NULL') + ')'          ELSE ''         END        AS [DataType],       DataObjectType  FROM   (Select t.name AS TypeName, REPLACE(c.name,'@','') AS Name,          c.max_length AS MaxLength, c.precision AS [Precision],           c.scale AS [Scale], c.[Object_id] AS ObjectID, XML_collection_ID,          is_XML_Document,'P' AS DataobjectType  FROM sys.parameters c  INNER JOIN sys.types t ON c.user_Type_ID = t.user_Type_ID  AND parameter_id>0  UNION all  Select t.name AS TypeName, c.name AS Name, c.max_length AS MaxLength,          c.precision AS [Precision], c.scale AS [Scale],          c.[Object_id] AS ObjectID, XML_collection_ID,is_XML_Document,          'C' AS DataobjectType            FROM sys.columns c  INNER JOIN sys.types t ON c.user_Type_ID = t.user_Type_ID   WHERE OBJECT_SCHEMA_NAME(c.object_ID) <> 'sys'  )f)SELECT CONVERT(CHAR(80),objectName+'.'   + CASE WHEN DataobjectType ='P' THEN '@' ELSE '' END + DataName),DataType FROM UserObjectWHERE DataName IN   (SELECT DataName FROM UserObject   GROUP BY DataName    HAVING MIN(Datatype)<>MAX(DataType))ORDER BY DataName     Hmm. I can tell you I found quite a few minor issues with the various tabases I tested this on, and found some potential bugs that really leap out at you from the results. Here is the start of the result for AdventureWorks. Yes, AccountNumber is, for some reason, a Varchar(10) in the Customer table. Hmm. odd. Why is a city fifty characters long in that view?  The idea of the description of a colour being 256 characters long seems over-ambitious. Go down the list and you'll spot other mistakes. There are no bugs, but just mess. We started out with a listing to examine parameters, then we mixed parameters and columns. Our last listing is for a slightly more in-depth look at table columns. You’ll notice that we’ve delibarately removed the indication of whether a column is persisted, or is an identity column because that gives us false positives for our code smells. If you just want to browse your metadata for other reasons (and it can quite help in some circumstances) then uncomment them! ;WITH userColumns AS  ( SELECT   c.NAME AS columnName,  OBJECT_SCHEMA_NAME(c.object_ID) + '.' + OBJECT_NAME(c.object_ID) AS ObjectName,  REPLACE(t.name + ' '   + CASE WHEN is_computed = 1 THEN ' AS ' + --do DDL for a computed column          (SELECT definition FROM sys.computed_columns cc           WHERE cc.object_id = c.object_id AND cc.column_ID = c.column_ID)     --we may have to put in the length            WHEN t.Name IN ('char', 'varchar', 'nchar', 'nvarchar')             THEN '('               + CASE WHEN c.Max_Length = -1 THEN 'MAX'                ELSE CONVERT(VARCHAR(4),                    CASE WHEN t.Name IN ('nchar', 'nvarchar')                      THEN c.Max_Length / 2 ELSE c.Max_Length                    END)                END + ')'       WHEN t.name IN ('decimal', 'numeric')       THEN '(' + CONVERT(VARCHAR(4), c.precision) + ',' + CONVERT(VARCHAR(4), c.Scale) + ')'       ELSE ''      END + CASE WHEN c.is_rowguidcol = 1          THEN ' ROWGUIDCOL'          ELSE ''         END + CASE WHEN XML_collection_ID <> 0            THEN --deal with object schema names             '(' + CASE WHEN is_XML_Document = 1                THEN 'DOCUMENT '                ELSE 'CONTENT '               END + COALESCE((SELECT                QUOTENAME(ss.name) + '.' + QUOTENAME(sc.name)                FROM                sys.xml_schema_collections sc                INNER JOIN Sys.Schemas ss ON sc.schema_ID = ss.schema_ID                WHERE                sc.xml_collection_ID = c.XML_collection_ID),                'NULL') + ')'            ELSE ''           END + CASE WHEN is_identity = 1             THEN CASE WHEN OBJECTPROPERTY(object_id,                'IsUserTable') = 1 AND COLUMNPROPERTY(object_id,                c.name,                'IsIDNotForRepl') = 0 AND OBJECTPROPERTY(object_id,                'IsMSShipped') = 0                THEN ''                ELSE ' NOT FOR REPLICATION '               END             ELSE ''            END + CASE WHEN c.is_nullable = 0               THEN ' NOT NULL'               ELSE ' NULL'              END + CASE                WHEN c.default_object_id <> 0                THEN ' DEFAULT ' + object_Definition(c.default_object_id)                ELSE ''               END + CASE                WHEN c.collation_name IS NULL                THEN ''                WHEN c.collation_name <> (SELECT                collation_name                FROM                sys.databases                WHERE                name = DB_NAME()) COLLATE Latin1_General_CI_AS                THEN COALESCE(' COLLATE ' + c.collation_name,                '')                ELSE ''                END,'  ',' ') AS [DataType]FROM sys.columns c  INNER JOIN sys.types t ON c.user_Type_ID = t.user_Type_ID  WHERE OBJECT_SCHEMA_NAME(c.object_ID) <> 'sys')SELECT CONVERT(CHAR(80),objectName+'.'+columnName),DataType FROM UserColumnsWHERE columnName IN (SELECT columnName FROM UserColumns  GROUP BY columnName  HAVING MIN(Datatype)<>MAX(DataType))ORDER BY columnName If you take a look down the results against Adventureworks, you'll see once again that there are things to investigate, mostly, in the illustration, discrepancies between null and non-null datatypes So I here you ask, what about temporary variables within routines? If ever there was a source of elusive bugs, you'll find it there. Sadly, these temporary variables are not stored in the metadata so we'll have to find a more subtle way of flushing these out, and that will, I'm afraid, have to wait!

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  • Microsoft Dev Centre accounts

    - by Phil Murray
    Looks like Microsoft is offering a special offer of 95% of the yearly subscription for the Phone Dev Centre (I didn't say anything about desperate). What I was wondering is do you need a seperate account to publish to the Windows Phone app centre and the Windows App Centre? Also I heard some horror stories about the time it takes to get application published on the Windows phone marketplace, does anyone have any experience with this? Windows Phone Dev Centre Windows App Dev Centre

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  • Evolution of an Application: how to manage and improve core engine?

    - by Phil Carter
    The web application I work on has been live for a year now, but it's time for it to evolve and one of the ways in which it is evolving is into a multi-brand application - in this case several different companies using the application, different templates/content and some slight business logic changes between them. The problem I'm facing is implementing a best practice across the site where there are differences in business logic for each brand. These will mostly be very superficial, using a an alternative mailing list provider or capturing some extra data in a form. I don't want to have if(brand === x) { ... } else { ... } all over the site especially as most of what needs to be changed can be handled with extending the existing class. I've thought of several methods that could be used to instantiate the correct class, but I'm just not sure which is going to be best especially as some seem to lead to duplication of more code than should be necessary. Here's what I've considered: 1) Use a Static Loader similar to Zend_Loader which can take the class being requested, and has knowledge of the Brand and can then return the correct object. $class = App_Loader::getObject('User', $brand); 2) Factory classes. We use these in the application already for Products but we could utilise them here also to provide a transparent interface to the class. 3) Routing the page request to a specific brand controller. This however seems like it would duplicate a lot of code/logic. Is there a pattern or something else I should be considering to solve this problem? 4) How to manage a growing project that has multiple custom instances in production? Update This is a PHP application so the decisions on which class to load are made per request. There could be upwards of 100+ different 'brands' running.

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  • Normalisation and 'Anima notitia copia' (Soul of the Database)

    - by Phil Factor
    (A Guest Editorial for Simple-Talk) The other day, I was staring  at the sys.syslanguages  table in SQL Server with slightly-raised eyebrows . I’d just been reading Chris Date’s  interesting book ‘SQL and Relational Theory’. He’d made the point that you’re not necessarily doing relational database operations by using a SQL Database product.  The same general point was recently made by Dino Esposito about ASP.NET MVC.  The use of ASP.NET MVC doesn’t guarantee you a good application design: It merely makes it possible to test it. The way I’d describe the sentiment in both cases is ‘you can hit someone over the head with a frying-pan but you can’t call it cooking’. SQL enables you to create relational databases. However,  even if it smells bad, it is no crime to do hideously un-relational things with a SQL Database just so long as it’s necessary and you can tell the difference; not only that but also only if you’re aware of the risks and implications. Naturally, I’ve never knowingly created a database that Codd would have frowned at, but around the edges are interfaces and data feeds I’ve written  that have caused hissy fits amongst the Normalisation fundamentalists. Part of the problem for those who agonise about such things  is the misinterpretation of Atomicity.  An atomic value is one for which, in the strange virtual universe you are creating in your database, you don’t have any interest in any of its component parts.  If you aren’t interested in the electrons, neutrinos,  muons,  or  taus, then  an atom is ..er.. atomic. In the same way, if you are passed a JSON string or XML, and required to store it in a database, then all you need to do is to ask yourself, in your role as Anima notitia copia (Soul of the database) ‘have I any interest in the contents of this item of information?’.  If the answer is ‘No!’, or ‘nequequam! Then it is an atomic value, however complex it may be.  After all, you would never have the urge to store the pixels of images individually, under the misguided idea that these are the atomic values would you?  I would, of course,  ask the ‘Anima notitia copia’ rather than the application developers, since there may be more than one application, and the applications developers may be designing the application in the absence of full domain knowledge, (‘or by the seat of the pants’ as the technical term used to be). If, on the other hand, the answer is ‘sure, and we want to index the XML column’, then we may be in for some heavy XML-shredding sessions to get to store the ‘atomic’ values and ensure future harmony as the application develops. I went back to looking at the sys.syslanguages table. It has a months column with the months in a delimited list January,February,March,April,May,June,July,August,September,October,November,December This is an ordered list. Wicked? I seem to remember that this value, like shortmonths and days, is treated as a ‘thing’. It is merely passed off to an external  C++ routine in order to format a date in a particular language, and never accessed directly within the database. As far as the database is concerned, it is an atomic value.  There is more to normalisation than meets the eye.

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  • Restricting joystick within a radius of center

    - by Phil
    I'm using Unity3d iOs and am using the example joysticks that came with one of the packages. It works fine but the area the joystick moves in is a rectangle which is unintuitive for my type of game. I can figure out how to see if the distance between the center and the current point is too far but I can't figure out how to constrain it to a certain distance without interrupting the finger tracking. Here's the relevant code: using UnityEngine; using System.Collections; public class Boundary { public Vector2 min = Vector2.zero; public Vector2 max = Vector2.zero; } public class Joystick : MonoBehaviour{ static private Joystick[] joysticks; // A static collection of all joysticks static private bool enumeratedJoysticks=false; static private float tapTimeDelta = 0.3f; // Time allowed between taps public bool touchPad; // Is this a TouchPad? public Rect touchZone; public Vector2 deadZone = Vector2.zero; // Control when position is output public bool normalize = false; // Normalize output after the dead-zone? public Vector2 position; // [-1, 1] in x,y public int tapCount; // Current tap count private int lastFingerId = -1; // Finger last used for this joystick private float tapTimeWindow; // How much time there is left for a tap to occur private Vector2 fingerDownPos; private float fingerDownTime; private float firstDeltaTime = 0.5f; private GUITexture gui; // Joystick graphic private Rect defaultRect; // Default position / extents of the joystick graphic private Boundary guiBoundary = new Boundary(); // Boundary for joystick graphic public Vector2 guiTouchOffset; // Offset to apply to touch input private Vector2 guiCenter; // Center of joystick private Vector3 tmpv3; private Rect tmprect; private Color tmpclr; public float allowedDistance; public enum JoystickType { movement, rotation } public JoystickType joystickType; public void Start() { // Cache this component at startup instead of looking up every frame gui = (GUITexture) GetComponent( typeof(GUITexture) ); // Store the default rect for the gui, so we can snap back to it defaultRect = gui.pixelInset; if ( touchPad ) { // If a texture has been assigned, then use the rect ferom the gui as our touchZone if ( gui.texture ) touchZone = gui.pixelInset; } else { // This is an offset for touch input to match with the top left // corner of the GUI guiTouchOffset.x = defaultRect.width * 0.5f; guiTouchOffset.y = defaultRect.height * 0.5f; // Cache the center of the GUI, since it doesn't change guiCenter.x = defaultRect.x + guiTouchOffset.x; guiCenter.y = defaultRect.y + guiTouchOffset.y; // Let's build the GUI boundary, so we can clamp joystick movement guiBoundary.min.x = defaultRect.x - guiTouchOffset.x; guiBoundary.max.x = defaultRect.x + guiTouchOffset.x; guiBoundary.min.y = defaultRect.y - guiTouchOffset.y; guiBoundary.max.y = defaultRect.y + guiTouchOffset.y; } } public void Disable() { gameObject.active = false; enumeratedJoysticks = false; } public void ResetJoystick() { if (joystickType != JoystickType.rotation) { //Don't do anything if turret mode // Release the finger control and set the joystick back to the default position gui.pixelInset = defaultRect; lastFingerId = -1; position = Vector2.zero; fingerDownPos = Vector2.zero; if ( touchPad ){ tmpclr = gui.color; tmpclr.a = 0.025f; gui.color = tmpclr; } } else { //gui.pixelInset = defaultRect; lastFingerId = -1; position = position; fingerDownPos = fingerDownPos; if ( touchPad ){ tmpclr = gui.color; tmpclr.a = 0.025f; gui.color = tmpclr; } } } public bool IsFingerDown() { return (lastFingerId != -1); } public void LatchedFinger( int fingerId ) { // If another joystick has latched this finger, then we must release it if ( lastFingerId == fingerId ) ResetJoystick(); } public void Update() { if ( !enumeratedJoysticks ) { // Collect all joysticks in the game, so we can relay finger latching messages joysticks = (Joystick[]) FindObjectsOfType( typeof(Joystick) ); enumeratedJoysticks = true; } //CHeck if distance is over the allowed amount //Get centerPosition //Get current position //Get distance //If over, don't allow int count = iPhoneInput.touchCount; // Adjust the tap time window while it still available if ( tapTimeWindow > 0 ) tapTimeWindow -= Time.deltaTime; else tapCount = 0; if ( count == 0 ) ResetJoystick(); else { for(int i = 0;i < count; i++) { iPhoneTouch touch = iPhoneInput.GetTouch(i); Vector2 guiTouchPos = touch.position - guiTouchOffset; bool shouldLatchFinger = false; if ( touchPad ) { if ( touchZone.Contains( touch.position ) ) shouldLatchFinger = true; } else if ( gui.HitTest( touch.position ) ) { shouldLatchFinger = true; } // Latch the finger if this is a new touch if ( shouldLatchFinger && ( lastFingerId == -1 || lastFingerId != touch.fingerId ) ) { if ( touchPad ) { tmpclr = gui.color; tmpclr.a = 0.15f; gui.color = tmpclr; lastFingerId = touch.fingerId; fingerDownPos = touch.position; fingerDownTime = Time.time; } lastFingerId = touch.fingerId; // Accumulate taps if it is within the time window if ( tapTimeWindow > 0 ) { tapCount++; print("tap" + tapCount.ToString()); } else { tapCount = 1; print("tap" + tapCount.ToString()); //Tell gameobject that player has tapped turret joystick if (joystickType == JoystickType.rotation) { //TODO: Call! } tapTimeWindow = tapTimeDelta; } // Tell other joysticks we've latched this finger foreach ( Joystick j in joysticks ) { if ( j != this ) j.LatchedFinger( touch.fingerId ); } } if ( lastFingerId == touch.fingerId ) { // Override the tap count with what the iPhone SDK reports if it is greater // This is a workaround, since the iPhone SDK does not currently track taps // for multiple touches if ( touch.tapCount > tapCount ) tapCount = touch.tapCount; if ( touchPad ) { // For a touchpad, let's just set the position directly based on distance from initial touchdown position.x = Mathf.Clamp( ( touch.position.x - fingerDownPos.x ) / ( touchZone.width / 2 ), -1, 1 ); position.y = Mathf.Clamp( ( touch.position.y - fingerDownPos.y ) / ( touchZone.height / 2 ), -1, 1 ); } else { // Change the location of the joystick graphic to match where the touch is tmprect = gui.pixelInset; tmprect.x = Mathf.Clamp( guiTouchPos.x, guiBoundary.min.x, guiBoundary.max.x ); tmprect.y = Mathf.Clamp( guiTouchPos.y, guiBoundary.min.y, guiBoundary.max.y ); //Check distance float distance = Vector2.Distance(new Vector2(defaultRect.x, defaultRect.y), new Vector2(tmprect.x, tmprect.y)); float angle = Vector2.Angle(new Vector2(defaultRect.x, defaultRect.y), new Vector2(tmprect.x, tmprect.y)); if (distance < allowedDistance) { //Ok gui.pixelInset = tmprect; } else { //This is where I don't know what to do... } } if ( touch.phase == iPhoneTouchPhase.Ended || touch.phase == iPhoneTouchPhase.Canceled ) ResetJoystick(); } } } if ( !touchPad ) { // Get a value between -1 and 1 based on the joystick graphic location position.x = ( gui.pixelInset.x + guiTouchOffset.x - guiCenter.x ) / guiTouchOffset.x; position.y = ( gui.pixelInset.y + guiTouchOffset.y - guiCenter.y ) / guiTouchOffset.y; } // Adjust for dead zone float absoluteX = Mathf.Abs( position.x ); float absoluteY = Mathf.Abs( position.y ); if ( absoluteX < deadZone.x ) { // Report the joystick as being at the center if it is within the dead zone position.x = 0; } else if ( normalize ) { // Rescale the output after taking the dead zone into account position.x = Mathf.Sign( position.x ) * ( absoluteX - deadZone.x ) / ( 1 - deadZone.x ); } if ( absoluteY < deadZone.y ) { // Report the joystick as being at the center if it is within the dead zone position.y = 0; } else if ( normalize ) { // Rescale the output after taking the dead zone into account position.y = Mathf.Sign( position.y ) * ( absoluteY - deadZone.y ) / ( 1 - deadZone.y ); } } } So the later portion of the code handles the updated position of the joystick thumb. This is where I'd like it to track the finger position in a direction it still is allowed to move (like if the finger is too far up and slightly to the +X I'd like to make sure the joystick is as close in X and Y as allowed within the radius) Thanks for reading!

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  • A Slice of Raspberry Pi

    - by Phil Factor
    Guest editorial for the ITPro/SysAdmin newsletter The Raspberry Pi Foundation has done a superb design job on their new $35 network-enabled Linux computer. This tiny machine, incorporating an ARM processor on a Broadcom BCM2835 multimedia chip, aims to put the fun back into learning computing. The public response has been overwhelmingly positive.Note that aim: "…to put the fun back". Education in Information Technology is in dire straits. It always has been, but seems to have deteriorated further still, even in the face of improved provision of equipment.In many countries, the government controls the curriculum. It predicted a shortage in office-based IT skills, and so geared the ICT curriculum toward mind-numbing training in word-processing and spreadsheet skills. Instead, the shortage has turned out to be in people with an engineering-mindset, who can solve problems with whatever technologies are available and learn new techniques quickly, in a rapidly-changing field.In retrospect, the assumption that specific training was required rather than an education was an idiotic response to the arrival of mainstream information technology. As a result, ICT became a disaster area, which discouraged a generation of youngsters from a career in IT, and thereby led directly to the shortage of people with the skills that are required to exploit the potential of Information Technology..Raspberry Pi aims to reverse the trend. This is a rig that is geared to fast graphics in high resolution. It is no toy. It should be a superb games machine. However, the use of Fedora, Debian, or Arch Linux ARM shows the more serious educational intent behind the Foundation's work. It looks like it will even do some office work too!So, get hold of any power supply that provides a 5VDC source at the required 700mA; an old Blackberry charger will do or, alternatively, it will run off four AA cells. You'll need a USB hub to support the mouse and keyboard, and maybe a hard drive. You'll want a DVI monitor (with audio out) or TV (sound and video). You'll also need to be able to cope with wired Ethernet 10/100, if you want networking.With this lot assembled, stick the paraphernalia on the back of the HDTV with Blu Tack, get a nice keyboard, and you have a classy Linux-based home computer. The major cost is in the T.V and the keyboard. If you're not already writing software for this platform, then maybe, at a time when some countries are talking of orders in the millions, you should consider it.

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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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