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• PASS Summit – looking back on my first time

  - by Fatherjack

    So I was lucky enough to get my first experience of PASS Summit this year and took some time beforehand to read some blogs and reference material to get an idea on what to do and how to get the best out of my visit. Having been to other conferences – technical and non-technical – I had a reasonable idea on the routine and what to expect in general. Here is a list of a few things that I have learned/remembered as the week has gone by. Wear comfortable shoes. This actually needs to be broadened to Take several pairs of comfortable shoes. You will be spending many many hours, for several days one after another. Having comfortable feet that can literally support you for the duration will make the week in general a whole lot better. Not only at the conference but getting to and from you could well be walking. In the evenings you will be walking around town and standing talking in various bars and clubs. Looking back, on some days I was on my feet for over 20 hours. Make friends. This is a given for the long term benefits it brings but there is also an immediate reward in being at a conference with a friend or two. Some events are bigger and more popular than others and some have the type of session that every single attendee will want to be in. This is great for those that get in but if you are in the bathroom or queuing for coffee and you miss out it sucks. Having a friend that can get in to a room and reserve you a seat is a great advantage to make sure you get the content that you want to see and still have the coffee that you need. Don’t go to every session you want to see This might sound counter intuitive and it relies on the sessions being recorded in some way to guarantee you don’t totally miss out. Both PASS Summit and SQL Bits sessions are recorded (summit is audio, SQLBits is video) and this means that if you get into a good conversation with someone over a coffee you don’t have to break it up to go to a session. Obviously there is a trade-off here and you need to decide on the tipping point for yourself but a conversation at a place like this could make a big difference to the next contract or employer you have or it might simply be great catching up with some friends you don’t see so often. Go to at least one session you don’t want to Again, this will seem to be contrary to normal logic but there is no reason why you shouldn’t learn about a part of SQL Server that isn’t part of your daily routine. Not only will you learn something new but you will also pick up on the feelings and attitudes of the people in the session. So, if you are a DBA, head off to a BI session and so on. You’ll hear BI speakers speaking to a BI audience and get to understand their point of view and reasoning for making the decisions they do. You will also appreciate the way that your decisions and instructions affect the way they have to work. This will help you a lot when you are on a project, working with multiple teams and make you all more productive. Socialise While you are at the conference venue, speak to people. Ask questions, be interested in whoever you are speaking to. You get chances to talk to new friends at breakfast, dinner and every break between sessions. The only people that might not talk to you would be speakers that are about to go and give a session, in most cases speakers like peace and quiet before going on stage. Other than that the people around you are just waiting for someone to talk to them so make the first move. There is a whole lot going on outside of the conference hours and you should make an effort to join in with some of this too. At karaoke evenings or just out for a quiet drink with a few of the people you meet at the conference. Either way, don’t be a recluse and hide in your room or be alone out in the town. Don’t talk to people Once again this sounds wrong but stay with me. I have spoken to a number of speakers since Summit 2013 finished and they have all mentioned the time it has taken them to move about the conference venue due to people stopping them for a chat or to ask a question. 45 minutes to walk from a session room to the speaker room in one case. Wow. While none of the speakers were upset about this sort of delay I think delegates should take the situation into account and possibly defer their question to an email or to a time when the person they want is clearly less in demand. Give them a chance to enjoy the conference in the same way that you are, they may actually want to go to a session or just have a rest after giving their session – talking for 75 minutes is hard work, taking an extra 45 minutes right after is unbelievable. I certainly hope that they get good feedback on their sessions and perhaps if you spoke to a speaker outside a session you can give them a mention in the ‘any other comments’ part of the feedback, just to convey your gratitude for them giving up their time and expertise for free. Say thank you I just mentioned giving the speakers a clear, visible ‘thank you’ in the feedback but there are plenty of people that help make any conference the success it is that would really appreciate hearing that their efforts are valued. People on the registration desk, volunteers giving schedule guidance and directions, people on the community zone are all volunteers giving their time to help you have the best experience possible. Send an email to PASS and convey your thoughts about the work that was done. Maybe you want to be a volunteer next time so you could enquire how you get into that position at the same time. This isn’t an exclusive list and you may agree or disagree with the points I have made, please add anything you think is good advice in the comments. I’d like to finish by saying a huge thank you to all the people involved in planning, facilitating and executing the PASS Summit 2013, it was an excellent event and I know many others think it was a totally worthwhile event to attend.

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• Calling all developers building ASP.NET applications

  - by Laila Lotfi

  We know that developers building desktop apps have to contend with memory management issues, and we’d like to learn more about the memory challenges ASP.NET developers are facing. To be more specific, we’re carrying out some exploratory research leading into the next phase of development on ANTS Memory Profiler, and our development team would love to speak to developers building ASP.NET applications. You don’t need to have ever used ANTS profiler – this will be a more general conversation about: - your current site architecture, and how you manage the memory requirements of your applications on your back-end servers and web services. - how you currently diagnose memory leaks and where you do this (production server, or during testing phase, or if you normally manage to get them all during the local development). - what specific memory problems you’ve experienced – if any. Of course, we’ll compensate you for your time with a $50 Amazon voucher (or equivalent in other currencies), and our development team’s undying gratitude. If you’d like to participate, please just drop me a line on [email protected].

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• A Knights Tale

  - by Phil Factor

  There are so many lessons to be learned from the story of Knight Capital losing nearly half a billion dollars as a result of a deployment gone wrong. The Knight Capital Group (KCG N) was an American global financial services firm engaging in market making, electronic execution, and institutional sales and trading. According to the recent order (File No.3.15570) against Knight Capital by U.S. Securities and Exchange Commission?, Knight had, for many years used some software which broke up incoming “parent” orders into smaller “child” orders that were then transmitted to various exchanges or trading venues for execution. A tracking ‘cumulative quantity’ function counted the number of ‘child’ orders and stopped the process once the total of child orders matched the ‘parent’ and so the parent order had been completed. Back in the mists of time, some code had been added to it  which was excuted if a particular flag was set. It was called ‘power peg’ and seems to have had a similar design and purpose, but, one guesses, would have shared the same tracking function. This code had been abandoned in 2003, but never deleted. In 2005, The tracking function was moved to an earlier point in the main process. It would seem from the account that, from that point, had that flag ever been set, the old ‘Power Peg’ would have been executed like Godzilla bursting from the ice, making child orders without limit without any tracking function. It wasn’t, presumably because the software that set the flag was removed. In 2012, nearly a decade after ‘Power Peg’ was abandoned, Knight prepared a new module to their software to cope with the imminent Retail Liquidity Program (RLP) for the New York Stock Exchange. By this time, the flag had remained unused and someone made the fateful decision to reuse it, and replace the old ‘power peg’ code with this new RLP code. Had the two actions been done together in a single automated deployment, and the new deployment tested, all would have been well. It wasn’t. To quote… “Beginning on July 27, 2012, Knight deployed the new RLP code in SMARS in stages by placing it on a limited number of servers in SMARS on successive days. During the deployment of the new code, however, one of Knight’s technicians did not copy the new code to one of the eight SMARS computer servers. Knight did not have a second technician review this deployment and no one at Knight realized that the Power Peg code had not been removed from the eighth server, nor the new RLP code added. Knight had no written procedures that required such a review.” (para 15) “On August 1, Knight received orders from broker-dealers whose customers were eligible to participate in the RLP. The seven servers that received the new code processed these orders correctly. However, orders sent with the repurposed flag to the eighth server triggered the defective Power Peg code still present on that server. As a result, this server began sending child orders to certain trading centers for execution. Because the cumulative quantity function had been moved, this server continuously sent child orders, in rapid sequence, for each incoming parent order without regard to the number of share executions Knight had already received from trading centers. Although one part of Knight’s order handling system recognized that the parent orders had been filled, this information was not communicated to SMARS.” (para 16) SMARS routed millions of orders into the market over a 45-minute period, and obtained over 4 million executions in 154 stocks for more than 397 million shares. By the time that Knight stopped sending the orders, Knight had assumed a net long position in 80 stocks of approximately $3.5 billion and a net short position in 74 stocks of approximately $3.15 billion. Knight’s shares dropped more than 20% after traders saw extreme volume spikes in a number of stocks, including preferred shares of Wells Fargo (JWF) and semiconductor company Spansion (CODE). Both stocks, which see roughly 100,000 trade per day, had changed hands more than 4 million times by late morning. Ultimately, Knight lost over $460 million from this wild 45 minutes of trading. Obviously, I’m interested in all this because, at one time, I used to write trading systems for the City of London. Obviously, the US SEC is in a far better position than any of us to work out the failings of Knight’s IT department, and the report makes for painful reading. I can’t help observing, though, that even with the breathtaking mistakes all along the way, that a robust automated deployment process that was ‘all-or-nothing’, and tested from soup to nuts would have prevented the disaster. The report reads like a Greek Tragedy. All the way along one wants to shout ‘No! not that way!’ and ‘Aargh! Don’t do it!’. As the tragedy unfolds, the audience weeps for the players, trapped by a cruel fate. All application development and deployment requires defense in depth. All IT goes wrong occasionally, but if there is a culture of defensive programming throughout, the consequences are usually containable. For financial systems, these defenses are required by statute, and ignored only by the foolish. Knight’s mistakes weren’t made by just one hapless sysadmin, but were progressive errors by an  IT culture spanning at least ten years.  One can spell these out, but I think they’re obvious. One can only hope that the industry studies what happened in detail, learns from the mistakes, and draws the right conclusions.

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• Inside the DLR – Invoking methods

  - by Simon Cooper

  So, we’ve looked at how a dynamic call is represented in a compiled assembly, and how the dynamic lookup is performed at runtime. The last piece of the puzzle is how the resolved method gets invoked, and that is the subject of this post. Invoking methods As discussed in my previous posts, doing a full lookup and bind at runtime each and every single time the callsite gets invoked would be far too slow to be usable. The results obtained from the callsite binder must to be cached, along with a series of conditions to determine whether the cached result can be reused. So, firstly, how are the conditions represented? These conditions can be anything; they are determined entirely by the semantics of the language the binder is representing. The binder has to be able to return arbitary code that is then executed to determine whether the conditions apply or not. Fortunately, .NET 4 has a neat way of representing arbitary code that can be easily combined with other code – expression trees. All the callsite binder has to return is an expression (called a ‘restriction’) that evaluates to a boolean, returning true when the restriction passes (indicating the corresponding method invocation can be used) and false when it does’t. If the bind result is also represented in an expression tree, these can be combined easily like so: if ([restriction is true]) { [invoke cached method] } Take my example from my previous post: public class ClassA { public static void TestDynamic() { CallDynamic(new ClassA(), 10); CallDynamic(new ClassA(), "foo"); } public static void CallDynamic(dynamic d, object o) { d.Method(o); } public void Method(int i) {} public void Method(string s) {} } When the Method(int) method is first bound, along with an expression representing the result of the bind lookup, the C# binder will return the restrictions under which that bind can be reused. In this case, it can be reused if the types of the parameters are the same: if (thisArg.GetType() == typeof(ClassA) && arg1.GetType() == typeof(int)) { thisClassA.Method(i); } Caching callsite results So, now, it’s up to the callsite to link these expressions returned from the binder together in such a way that it can determine which one from the many it has cached it should use. This caching logic is all located in the System.Dynamic.UpdateDelegates class. It’ll help if you’ve got this type open in a decompiler to have a look yourself. For each callsite, there are 3 layers of caching involved: The last method invoked on the callsite. All methods that have ever been invoked on the callsite. All methods that have ever been invoked on any callsite of the same type. We’ll cover each of these layers in order Level 1 cache: the last method called on the callsite When a CallSite<T> object is first instantiated, the Target delegate field (containing the delegate that is called when the callsite is invoked) is set to one of the UpdateAndExecute generic methods in UpdateDelegates, corresponding to the number of parameters to the callsite, and the existance of any return value. These methods contain most of the caching, invoke, and binding logic for the callsite. The first time this method is invoked, the UpdateAndExecute method finds there aren’t any entries in the caches to reuse, and invokes the binder to resolve a new method. Once the callsite has the result from the binder, along with any restrictions, it stitches some extra expressions in, and replaces the Target field in the callsite with a compiled expression tree similar to this (in this example I’m assuming there’s no return value): if ([restriction is true]) { [invoke cached method] return; } if (callSite._match) { _match = false; return; } else { UpdateAndExecute(callSite, arg0, arg1, ...); } Woah. What’s going on here? Well, this resulting expression tree is actually the first level of caching. The Target field in the callsite, which contains the delegate to call when the callsite is invoked, is set to the above code compiled from the expression tree into IL, and then into native code by the JIT. This code checks whether the restrictions of the last method that was invoked on the callsite (the ‘primary’ method) match, and if so, executes that method straight away. This means that, the next time the callsite is invoked, the first code that executes is the restriction check, executing as native code! This makes this restriction check on the primary cached delegate very fast. But what if the restrictions don’t match? In that case, the second part of the stitched expression tree is executed. What this section should be doing is calling back into the UpdateAndExecute method again to resolve a new method. But it’s slightly more complicated than that. To understand why, we need to understand the second and third level caches. Level 2 cache: all methods that have ever been invoked on the callsite When a binder has returned the result of a lookup, as well as updating the Target field with a compiled expression tree, stitched together as above, the callsite puts the same compiled expression tree in an internal list of delegates, called the rules list. This list acts as the level 2 cache. Why use the same delegate? Stitching together expression trees is an expensive operation. You don’t want to do it every time the callsite is invoked. Ideally, you would create one expression tree from the binder’s result, compile it, and then use the resulting delegate everywhere in the callsite. But, if the same delegate is used to invoke the callsite in the first place, and in the caches, that means each delegate needs two modes of operation. An ‘invoke’ mode, for when the delegate is set as the value of the Target field, and a ‘match’ mode, used when UpdateAndExecute is searching for a method in the callsite’s cache. Only in the invoke mode would the delegate call back into UpdateAndExecute. In match mode, it would simply return without doing anything. This mode is controlled by the _match field in CallSite<T>. The first time the callsite is invoked, _match is false, and so the Target delegate is called in invoke mode. Then, if the initial restriction check fails, the Target delegate calls back into UpdateAndExecute. This method sets _match to true, then calls all the cached delegates in the rules list in match mode to try and find one that passes its restrictions, and invokes it. However, there needs to be some way for each cached delegate to inform UpdateAndExecute whether it passed its restrictions or not. To do this, as you can see above, it simply re-uses _match, and sets it to false if it did not pass the restrictions. This allows the code within each UpdateAndExecute method to check for cache matches like so: foreach (T cachedDelegate in Rules) { callSite._match = true; cachedDelegate(); // sets _match to false if restrictions do not pass if (callSite._match) { // passed restrictions, and the cached method was invoked // set this delegate as the primary target to invoke next time callSite.Target = cachedDelegate; return; } // no luck, try the next one... } Level 3 cache: all methods that have ever been invoked on any callsite with the same signature The reason for this cache should be clear – if a method has been invoked through a callsite in one place, then it is likely to be invoked on other callsites in the codebase with the same signature. Rather than living in the callsite, the ‘global’ cache for callsite delegates lives in the CallSiteBinder class, in the Cache field. This is a dictionary, typed on the callsite delegate signature, providing a RuleCache<T> instance for each delegate signature. This is accessed in the same way as the level 2 callsite cache, by the UpdateAndExecute methods. When a method is matched in the global cache, it is copied into the callsite and Target cache before being executed. Putting it all together So, how does this all fit together? Like so (I’ve omitted some implementation & performance details): That, in essence, is how the DLR performs its dynamic calls nearly as fast as statically compiled IL code. Extensive use of expression trees, compiled to IL and then into native code. Multiple levels of caching, the first of which executes immediately when the dynamic callsite is invoked. And a clever re-use of compiled expression trees that can be used in completely different contexts without being recompiled. All in all, a very fast and very clever reflection caching mechanism.

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• Developing Schema Compare for Oracle (Part 2): Dependencies

  - by Simon Cooper

  In developing Schema Compare for Oracle, one of the issues we came across was the size of the databases. As detailed in my last blog post, we had to allow schema pre-filtering due to the number of objects in a standard Oracle database. Unfortunately, this leads to some quite tricky situations regarding object dependencies. This post explains how we deal with these dependencies. 1. Cross-schema dependencies Say, in the following database, you're populating SchemaA, and synchronizing SchemaA.Table1: SOURCE   TARGET CREATE TABLE SchemaA.Table1 ( Col1 NUMBER REFERENCES SchemaB.Table1(Col1));   CREATE TABLE SchemaA.Table1 ( Col1 VARCHAR2(100) REFERENCES SchemaB.Table1(Col1)); CREATE TABLE SchemaB.Table1 ( Col1 NUMBER PRIMARY KEY);   CREATE TABLE SchemaB.Table1 ( Col1 VARCHAR2(100) PRIMARY KEY); We need to do a rebuild of SchemaA.Table1 to change Col1 from a VARCHAR2(100) to a NUMBER. This consists of: Creating a table with the new schema Inserting data from the old table to the new table, with appropriate conversion functions (in this case, TO_NUMBER) Dropping the old table Rename new table to same name as old table Unfortunately, in this situation, the rebuild will fail at step 1, as we're trying to create a NUMBER column with a foreign key reference to a VARCHAR2(100) column. As we're only populating SchemaA, the naive implementation of the object population prefiltering (sticking a WHERE owner = 'SCHEMAA' on all the data dictionary queries) will generate an incorrect sync script. What we actually have to do is: Drop foreign key constraint on SchemaA.Table1 Rebuild SchemaB.Table1 Rebuild SchemaA.Table1, adding the foreign key constraint to the new table This means that in order to generate a correct synchronization script for SchemaA.Table1 we have to know what SchemaB.Table1 is, and that it also needs to be rebuilt to successfully rebuild SchemaA.Table1. SchemaB isn't the schema that the user wants to synchronize, but we still have to load the table and column information for SchemaB.Table1 the same way as any table in SchemaA. Fortunately, Oracle provides (mostly) complete dependency information in the dictionary views. Before we actually read the information on all the tables and columns in the database, we can get dependency information on all the objects that are either pointed at by objects in the schemas we’re populating, or point to objects in the schemas we’re populating (think about what would happen if SchemaB was being explicitly populated instead), with a suitable query on all_constraints (for foreign key relationships) and all_dependencies (for most other types of dependencies eg a function using another function). The extra objects found can then be included in the actual object population, and the sync wizard then has enough information to figure out the right thing to do when we get to actually synchronize the objects. Unfortunately, this isn’t enough. 2. Dependency chains The solution above will only get the immediate dependencies of objects in populated schemas. What if there’s a chain of dependencies? A.tbl1 -> B.tbl1 -> C.tbl1 -> D.tbl1 If we’re only populating SchemaA, the implementation above will only include B.tbl1 in the dependent objects list, whereas we might need to know about C.tbl1 and D.tbl1 as well, in order to ensure a modification on A.tbl1 can succeed. What we actually need is a graph traversal on the dependency graph that all_dependencies represents. Fortunately, we don’t have to read all the database dependency information from the server and run the graph traversal on the client computer, as Oracle provides a method of doing this in SQL – CONNECT BY. So, we can put all the dependencies we want to include together in big bag with UNION ALL, then run a SELECT ... CONNECT BY on it, starting with objects in the schema we’re populating. We should end up with all the objects that might be affected by modifications in the initial schema we’re populating. Good solution? Well, no. For one thing, it’s sloooooow. all_dependencies, on my test databases, has got over 110,000 rows in it, and the entire query, for which Oracle was creating a temporary table to hold the big bag of graph edges, was often taking upwards of two minutes. This is too long, and would only get worse for large databases. But it had some more fundamental problems than just performance. 3. Comparison dependencies Consider the following schema: SOURCE   TARGET CREATE TABLE SchemaA.Table1 ( Col1 NUMBER REFERENCES SchemaB.Table1(col1));   CREATE TABLE SchemaA.Table1 ( Col1 VARCHAR2(100)); CREATE TABLE SchemaB.Table1 ( Col1 NUMBER PRIMARY KEY);   CREATE TABLE SchemaB.Table1 ( Col1 VARCHAR2(100)); What will happen if we used the dependency algorithm above on the source & target database? Well, SchemaA.Table1 has a foreign key reference to SchemaB.Table1, so that will be included in the source database population. On the target, SchemaA.Table1 has no such reference. Therefore SchemaB.Table1 will not be included in the target database population. In the resulting comparison of the two objects models, what you will end up with is: SOURCE  TARGET SchemaA.Table1 -> SchemaA.Table1 SchemaB.Table1 -> (no object exists) When this comparison is synchronized, we will see that SchemaB.Table1 does not exist, so we will try the following sequence of actions: Create SchemaB.Table1 Rebuild SchemaA.Table1, with foreign key to SchemaB.Table1 Oops. Because the dependencies are only followed within a single database, we’ve tried to create an object that already exists. To fix this we can include any objects found as dependencies in the source or target databases in the object population of both databases. SchemaB.Table1 will then be included in the target database population, and we won’t try and create objects that already exist. All good? Well, consider the following schema (again, only explicitly populating SchemaA, and synchronizing SchemaA.Table1): SOURCE   TARGET CREATE TABLE SchemaA.Table1 ( Col1 NUMBER REFERENCES SchemaB.Table1(col1));   CREATE TABLE SchemaA.Table1 ( Col1 VARCHAR2(100)); CREATE TABLE SchemaB.Table1 ( Col1 NUMBER PRIMARY KEY);   CREATE TABLE SchemaB.Table1 ( Col1 VARCHAR2(100) PRIMARY KEY); CREATE TABLE SchemaC.Table1 ( Col1 NUMBER);   CREATE TABLE SchemaC.Table1 ( Col1 VARCHAR2(100) REFERENCES SchemaB.Table1); Although we’re now including SchemaB.Table1 on both sides of the comparison, there’s a third table (SchemaC.Table1) that we don’t know about that will cause the rebuild of SchemaB.Table1 to fail if we try and synchronize SchemaA.Table1. That’s because we’re only running the dependency query on the schemas we’re explicitly populating; to solve this issue, we would have to run the dependency query again, but this time starting the graph traversal from the objects found in the other database. Furthermore, this dependency chain could be arbitrarily extended.This leads us to the following algorithm for finding all the dependencies of a comparison: Find initial dependencies of schemas the user has selected to compare on the source and target Include these objects in both the source and target object populations Run the dependency query on the source, starting with the objects found as dependents on the target, and vice versa Repeat 2 & 3 until no more objects are found For the schema above, this will result in the following sequence of actions: Find initial dependenciesSchemaA.Table1 -> SchemaB.Table1 found on sourceNo objects found on target Include objects in both source and targetSchemaB.Table1 included in source and target Run dependency query, starting with found objectsNo objects to start with on sourceSchemaB.Table1 -> SchemaC.Table1 found on target Include objects in both source and targetSchemaC.Table1 included in source and target Run dependency query on found objectsNo objects found in sourceNo objects to start with in target Stop This will ensure that we include all the necessary objects to make any synchronization work. However, there is still the issue of query performance; the CONNECT BY on the entire database dependency graph is still too slow. After much sitting down and drawing complicated diagrams, we decided to move the graph traversal algorithm from the server onto the client (which turned out to run much faster on the client than on the server); and to ensure we don’t read the entire dependency graph onto the client we also pull the graph across in bits – we start off with dependency edges involving schemas selected for explicit population, and whenever the graph traversal comes across a dependency reference to a schema we don’t yet know about a thunk is hit that pulls in the dependency information for that schema from the database. We continue passing more dependent objects back and forth between the source and target until no more dependency references are found. This gives us the list of all the extra objects to populate in the source and target, and object population can then proceed. 4. Object blacklists and fast dependencies When we tested this solution, we were puzzled in that in some of our databases most of the system schemas (WMSYS, ORDSYS, EXFSYS, XDB, etc) were being pulled in, and this was increasing the database registration and comparison time quite significantly. After debugging, we discovered that the culprits were database tables that used one of the Oracle PL/SQL types (eg the SDO_GEOMETRY spatial type). These were creating a dependency chain from the database tables we were populating to the system schemas, and hence pulling in most of the system objects in that schema. To solve this we introduced blacklists of objects we wouldn’t follow any dependency chain through. As well as the Oracle-supplied PL/SQL types (MDSYS.SDO_GEOMETRY, ORDSYS.SI_COLOR, among others) we also decided to blacklist the entire PUBLIC and SYS schemas, as any references to those would likely lead to a blow up in the dependency graph that would massively increase the database registration time, and could result in the client running out of memory. Even with these improvements, each dependency query was taking upwards of a minute. We discovered from Oracle execution plans that there were some columns, with dependency information we required, that were querying system tables with no indexes on them! To cut a long story short, running the following query: SELECT * FROM all_tab_cols WHERE data_type_owner = ‘XDB’; results in a full table scan of the SYS.COL$ system table! This single clause was responsible for over half the execution time of the dependency query. Hence, the ‘Ignore slow dependencies’ option was born – not querying this and a couple of similar clauses to drastically speed up the dependency query execution time, at the expense of producing incorrect sync scripts in rare edge cases. Needless to say, along with the sync script action ordering, the dependency code in the database registration is one of the most complicated and most rewritten parts of the Schema Compare for Oracle engine. The beta of Schema Compare for Oracle is out now; if you find a bug in it, please do tell us so we can get it fixed!

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• XSL-stylesheet URI using JAX-WS and Glassfish v3.

  - by Tony

  Hi there. I'm trying to use XSL-stylesheets in order to transform some generated XML-data to HTML-output. The architecture that I'm using is as follows: [Client Side] Web-Browser = [Server Side: Glassfish v3] JSP-pages - Web-Services. My web service generates some XML-data, then I want to format it with XSL-stylesheet, pass the result to JSP-page and show to user. I'm using JAXP for XSL-transformations and I want to create a javax.xml.transform.stream.StreamSource object with XSL-file stream for the javax.xml.transform.Transformer object, but I'm having a difficulty with specifying the path/URL for the XSL-file. So the question is: where should I put my XSL-stylesheets in a project and how should I access them from code? I'm using Glassfish v3 and NetBeans 6.8. Thanks.

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• Software Tuned to Humanity

  - by Phil Factor

  I learned a great deal from a cynical old programmer who once told me that the ideal length of time for a compiler to do its work was the same time it took to roll a cigarette. For development work, this is oh so true. After intently looking at the editing window for an hour or so, it was a relief to look up, stretch, focus the eyes on something else, and roll the possibly-metaphorical cigarette. This was software tuned to humanity. Likewise, a user’s perception of the “ideal” time that an application will take to move from frame to frame, to retrieve information, or to process their input has remained remarkably static for about thirty years, at around 200 ms. Anything else appears, and always has, to be either fast or slow. This could explain why commercial applications, unlike games, simulations and communications, aren’t noticeably faster now than they were when I started programming in the Seventies. Sure, they do a great deal more, but the SLAs that I negotiated in the 1980s for application performance are very similar to what they are nowadays. To prove to myself that this wasn’t just some rose-tinted misperception on my part, I cranked up a Z80-based Jonos CP/M machine (1985) in the roof-space. Within 20 seconds from cold, it had loaded Wordstar and I was ready to write. OK, I got it wrong: some things were faster 30 years ago. Sure, I’d now have had all sorts of animations, wizzy graphics, and other comforting features, but it seems a pity that we have used all that extra CPU and memory to increase the scope of what we develop, and the graphical prettiness, but not to speed the processes needed to complete a business procedure. Never mind the weight, the response time’s great! To achieve 200 ms response times on a Z80, or similar, performance considerations influenced everything one did as a developer. If it meant writing an entire application in assembly code, applying every smart algorithm, and shortcut imaginable to get the application to perform to spec, then so be it. As a result, I’m a dyed-in-the-wool performance freak and find it difficult to change my habits. Conversely, many developers now seem to feel quite differently. While all will acknowledge that performance is important, it’s no longer the virtue is once was, and other factors such as user-experience now take precedence. Am I wrong? If not, then perhaps we need a new school of development technique to rival Agile, dedicated once again to producing applications that smoke the rear wheels rather than pootle elegantly to the shops; that forgo skeuomorphism, cute animation, or architectural elegance in favor of the smell of hot rubber. I struggle to name an application I use that is truly notable for its blistering performance, and would dearly love one to do my everyday work – just as long as it doesn’t go faster than my brain.

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• Protect and Improve your Software with SmartAssembly 5

  - by Bart Read

  SmartAssembly 5 has been released. You can download a 14-day fully-functional free trial from: http://www.red-gate.com/products/smartassembly/index.htm This is the first major release since Red Gate acquired the tool last year, and our focus has mainly been on improving the quality of an already great tool. We've also simplified the licensing model so that there are now only three editions: Standard - bullet-proof protection at a bargain price, Pro - includes the SDK & custom web server...(read more)

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• Adding Chart to WordprocessingML

  - by kern

  I would like to generate an Open XML document containing a Chart using the Open Xml SDK 2. I found an SpreadsheetML example, but I can't work out how to add the chart in a .docx... Is there a good source for documentation/examples for the Open Xml SDK 2?

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• Antenna Aligner part 2: Finding the right direction

  - by Chris George

  Last time I managed to get "my first app(tm)" built, published and running on my iPhone. This was really cool, a piece of my code running on my very own device. Ok, so I'm easily pleased! The next challenge was actually trying to determine what it was I wanted this app to do, and how to do it. Reverting back to good old paper and pen, I started sketching out designs for the app. I knew I wanted it to get a list of transmitters, then clicking on a transmitter would display a compass type view, with an arrow pointing the right way. I figured there would not be much point in continuing until I know I could do the graphical part of the project, i.e. the rotating compass, so armed with that reasoning (plus the fact I just wanted to get on and code!), I once again dived into visual studio. Using my friend (google) I found some example code for getting the compass data from the phone using the PhoneGap framework. // onSuccess: Get the current heading // function onSuccess(heading) {    alert('Heading: ' + heading); } navigator.compass.getCurrentHeading(onSuccess, onError); Using the ripple mobile emulator this showed that it was successfully getting the compass heading. But it didn't work when uploaded to my phone. It turns out that the examples I had been looking at were for PhoneGap 1.0, and Nomad uses PhoneGap 1.4.1. In 1.4.1, getCurrentHeading provides a compass object to onSuccess, not just a numeric value, so the code now looks like // onSuccess: Get the current magnetic heading // function onSuccess(heading) {    alert('Heading: ' + heading.magneticHeading); }; navigator.compass.getCurrentHeading(onSuccess, onError); So the lesson learnt from this... read the documentation for the version you are actually using! This does, however, lead to compatibility problems with ripple as it only supports 1.0 which is a real pain. I hope that the ripple system is updated sometime soon.

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• Getting baseline and performance stats - the easy way.

  - by fatherjack

  OK, pretty much any DBA worth their salt has read Brent Ozar's (Blog | Twitter) blog about getting a baseline of your server's performance counters and then getting the same counters at regular intervals afterwards so that you can track performance trends and evidence how you are making your servers faster or cope with extra load without costing your boss any money for hardware upgrades. No? well, go read it now. I can wait a while as there is a great video there too...http://www.brentozar.com/archive/2006/12/dba-101-using-perfmon-for-sql-performance-tuning/,...(read more)

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• New features in SQL Prompt 6.4

  - by Tom Crossman

  We’re pleased to announce a new beta version of SQL Prompt. We’ve been trying out a few new core technologies, and used them to add features and bug fixes suggested by users on the SQL Prompt forum and suggestions forum. You can download the SQL Prompt 6.4 beta here (zip file). Let us know what you think! New features Execute current statement In a query window, you can now execute the SQL statement under your cursor by pressing Shift + F5. For example, if you have a query containing two statements and your cursor is placed on the second statement: When you press Shift + F5, only the second statement is executed:   Insert semicolons You can now use SQL Prompt to automatically insert missing semicolons after each statement in a query. To insert semicolons, go to the SQL Prompt menu and click Insert Semicolons. Alternatively, hold Ctrl and press B then C. BEGIN…END block highlighting When you place your cursor over a BEGIN or END keyword, SQL Prompt now automatically highlights the matching keyword: Rename variables and aliases You can now use SQL Prompt to rename all occurrences of a variable or alias in a query. To rename a variable or alias, place your cursor over an instance of the variable or alias you want to rename and press F2: Improved loading dialog box The database loading dialog box now shows actual progress, and you can cancel loading databases:   Single suggestion improvement SQL Prompt no longer suggests keywords if the keyword has been typed and no other suggestions exist. Performance improvement SQL Prompt now has less impact on Management Studio start up time. What do you think? We want to hear your feedback about the beta. If you have any suggestions, or bugs to report, tell us on the SQL Prompt forum or our suggestions forum.

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• XSLT: a variation on the pagination problem

  - by MarcoS

  I must transform some XML data into a paginated list of fields. Here is an example. Input XML: <?xml version="1.0" encoding="UTF-8"?> <data> <books> <book title="t0"/> <book title="t1"/> <book title="t2"/> <book title="t3"/> <book title="t4"/> </books> <library name="my library"/> </data> Desired output: <?xml version="1.0" encoding="UTF-8"?> <pages> <page number="1"> <field name="library_name" value="my library"/> <field name="book_1" value="t0"/> <field name="book_2" value="t1"/> </page> <page number="2"> <field name="book_1" value="t2"/> <field name="book_2" value="t3"/> </page> <page number="3"> <field name="book_1" value="t4"/> </page> </pages> In the above example I assume that I want at most 2 fields named book_n (with n ranging between 1 and 2) per page. Tags <page> must have an attribute number. Finally, the field named library_name must appear only the first <page>. Here is my current solution using XSLT: <?xml version="1.0" encoding="UTF-8"?> <xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform" version="2.0" exclude-result-prefixes="trx xs"> <xsl:output method="xml" indent="yes" omit-xml-declaration="no" /> <xsl:variable name="max" select="2"/> <xsl:template match="//books"> <xsl:for-each-group select="book" group-ending-with="*[position() mod $max = 0]"> <xsl:variable name="pageNum" select="position()"/> <page number="{$pageNum}"> <xsl:for-each select="current-group()"> <xsl:variable name="idx" select="if (position() mod $max = 0) then $max else position() mod $max"/> <field value="{@title}"> <xsl:attribute name="name">book_<xsl:value-of select="$idx"/> </xsl:attribute> </field> </xsl:for-each> <xsl:if test="$pageNum = 1"> <xsl:call-template name="templateFor_library"/> </xsl:if> </page> </xsl:for-each-group> </xsl:template> <xsl:template name="templateFor_library"> <xsl:for-each select="//library"> <field name="library_name" value="{@name}" /> </xsl:for-each> </xsl:template> </xsl:stylesheet> Is there a better/simpler way to perform this transformation?

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• Test-driven Database Development – Why Bother?

  Test-Driven Development is a practice that can bring many benefits, including better design, and less-buggy code, but is it relevant to database development, where the process of development tends to me much more interactive, and the culture more test-oriented? Greg reviews the support for TDD for Databases, and suggests that it is worth giving it a try for the range of advantages it can bring to team-working.

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• Migrating from OCS 2007 R2 to Lync: Part 2

  In the story so far, Johan has described how to check that the migration from your OCS to Lync is supported and how to determine the requirements for the new installation This was followed by a walk-through of the preparation the Active Directory and installation of the first Lync Front End Server with a Mediation Server co-located. Now Johan tackles the merging the OCS configuration, and connection to the outsode world, followed by testing, performing and then validating the migration.

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• Smartassembly 5: it lives! Early Access builds now available

  - by Bart Read

  I'm pleased to announce that, late last week, we put out the first early access build for Smartassembly 5, Red Gate's fantastic code protection and error reporting tool, which we acquired last September. You can download it via: http://www.red-gate.com/messageboard/viewforum.php?f=116 It's obviously pretty early days, so please do not try to use this to protect a production application, but we've already done a lot of work in some key areas: We're simplifying and streamlining the licensing model (you won't see this yet, but a lot of the work on this has already been done). We've improved usability of the product, with a better menu, reordering of project settings, and better defaults. We've also fixed a load of bugs, which I'll let Alex blog about in more detail. On a slightly more trivial level, the curly braces are also no more. Over the coming weeks, we'll be adding more improvements, and starting usability tests. If you're interested in getting involved in the latter, please drop an email to [email protected].

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• Exploring In-memory OLTP Engine (Hekaton) in SQL Server 2014 CTP1

  The continuing drop in the price of memory has made fast in-memory OLTP increasingly viable. SQL Server 2014 allows you to migrate the most-used tables in an existing database to memory-optimised 'Hekaton' technology, but how you balance between disk tables and in-memory tables for optimum performance requires judgement and experiment. What is this technology, and how can you exploit it? Rob Garrison explains.

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• Will HTML5 make Silverlight redundant?

  - by Laila

  One of the great features of Adobe AIR v2 that was launched this month was its support for some of the 2008 draft of HTML5. The HTML5 specification was started in 2004, but the full spec will probably not be approved by W3C until around 2022. One might have thought that it would take years yet from now to reach the point where any browsers were remotely HTML5-compliant, but enough of HTML5 is published and agreed to make a lot of it possible, and Safari and Adobe have got there thanks to Apple's open-source WebKit. The race for HTML 5 has been fuelled by the demand by Apple and Google for advanced graphics, typography, animations and transitions without having to rely on third party browser plug-ins such as Adobe Flash or Silverlight. There is good reason for this haste: Flash doesn't support touch-devices and has been slow in supporting hardware video decoders such as H.264. There is a strong requirement to do all that Flash can do in an open-standards way. Those with proprietary solutions remain sniffy. In AIR 2, Adobe pointedly disables the HTML5 and tags that allow basic playing of media content, saying that the specification is not final and there is still no standard for the supported formats, and adding that Safari implements a 'disjoint set' of codecs. Microsoft also has little interest in HTML 5 as it has so much invested in Silverlight. Google stands to gain by the Adobe AIR for Android as it will allow a lot of applications to be migrated easily to the platform, so sees Apple's war on Flash as a way of gaining market share. Why do we care? It is because HTML5/CSS3 provides facilities much far beyond HTML4, bring the reality of browser-based applications a lot closer. Probably most generally useful is the advanced typography: Safari and AIR already both support a way of reflowing text in a container across an arbitrary number of columns; Page-specific fonts can also be specified. Then there is 2D drawing, video, transitions, local storage, AJAX navigation and mutable DOM prototypes. HTML5 is likely to provide base functionality that is required but it is too early to be certain that it will render Flash, Silverlight or JavaFX obsolete. In the meantime, Adobe Air provides the best vehicle for developing HTML5/CSS3 applications without a twinge of worry about browser incompatibilities. Cheers, Laila

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• The Art of Dealing with People

  Technical people generally don't easily adapt to being good salespeople. When a technical person takes on a customer-facing role as a support engineer, there are a whole lot of new skills required. Dr Petrova relates how the experience of a change in job gave her a new respect for the skills of sales and marketing.

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• Documentation and Test Assertions in Databases

  - by Phil Factor

  When I first worked with Sybase/SQL Server, we thought our databases were impressively large but they were, by today’s standards, pathetically small. We had one script to build the whole database. Every script I ever read was richly annotated; it was more like reading a document. Every table had a comment block, and every line would be commented too. At the end of each routine (e.g. procedure) was a quick integration test, or series of test assertions, to check that nothing in the build was broken. We simply ran the build script, stored in the Version Control System, and it pulled everything together in a logical sequence that not only created the database objects but pulled in the static data. This worked fine at the scale we had. The advantage was that one could, by reading the source code, reach a rapid understanding of how the database worked and how one could interface with it. The problem was that it was a system that meant that only one developer at the time could work on the database. It was very easy for a developer to execute accidentally the entire build script rather than the selected section on which he or she was working, thereby cleansing the database of everyone else’s work-in-progress and data. It soon became the fashion to work at the object level, so that programmers could check out individual views, tables, functions, constraints and rules and work on them independently. It was then that I noticed the trend to generate the source for the VCS retrospectively from the development server. Tables were worst affected. You can, of course, add or delete a table’s columns and constraints retrospectively, which means that the existing source no longer represents the current object. If, after your development work, you generate the source from the live table, then you get no block or line comments, and the source script is sprinkled with silly square-brackets and other confetti, thereby rendering it visually indigestible. Routines, too, were affected. In our system, every routine had a directly attached string of unit-tests. A retro-generated routine has no unit-tests or test assertions. Yes, one can still commit our test code to the VCS but it’s a separate module and teams end up running the whole suite of tests for every individual change, rather than just the tests for that routine, which doesn’t scale for database testing. With Extended properties, one can get the best of both worlds, and even use them to put blame, praise or annotations into your VCS. It requires a lot of work, though, particularly the script to generate the table. The problem is that there are no conventional names beyond ‘MS_Description’ for the special use of extended properties. This makes it difficult to do splendid things such ensuring the integrity of the build by running a suite of tests that are actually stored in extended properties within the database and therefore the VCS. We have lost the readability of database source code over the years, and largely jettisoned the use of test assertions as part of the database build. This is not unexpected in view of the increasing complexity of the structure of databases and number of programmers working on them. There must, surely, be a way of getting them back, but I sometimes wonder if I’m one of very few who miss them.

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• Optimizing Transaction Log Throughput

  As a DBA, it is vital to manage transaction log growth explicitly, rather than let SQL Server auto-growth events "manage" it for you. If you undersize the log, and then let SQL Server auto-grow it in small increments, you'll end up with a very fragmented log. Examples in the article, extracted from SQL Server Transaction Log Management by Tony Davis and Gail Shaw, demonstrate how this can have a significant impact on the performance of any SQL Server operations that need to read the log.

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• What Counts For a DBA: Fitness

  - by Louis Davidson

  If you know me, you can probably guess that physical exercise is not really my thing. There was a time in my past when it a larger part of my life, but even then never in the same sort of passionate way as a number of our SQL friends.  For me, I find that mental exercise satisfies what I believe to be the same inner need that drives people to run farther than I like to drive on most Saturday mornings, and it is certainly just as addictive. Mental fitness shares many common traits with physical fitness, especially the need to attain it through repetitive training. I only wish that mental training burned off a bacon cheeseburger in the same manner as does jogging around a dewy park on Saturday morning. In physical training, there are at least two goals, the first of which is to be physically able to do a task. The second is to train the brain to perform the task without thinking too hard about it. No matter how long it has been since you last rode a bike, you will be almost certainly be able to hop on and start riding without thinking about the process of pedaling or balancing. If you’ve never ridden a bike, you could be a physics professor /Olympic athlete and still crash the first few times you try, even though you are as strong as an ox and your knowledge of the physics of bicycle riding makes the concept child’s play. For programming tasks, the process is very similar. As a DBA, you will come to know intuitively how to backup, optimize, and secure database systems. As a data programmer, you will work to instinctively use the clauses of Transact-SQL DML so that, when you need to group data three ways (and not four), you will know to use the GROUP BY clause with GROUPING SETS without resorting to a search engine.  You have the skill. Making it naturally then requires repetition and experience is the primary requirement, not just simply learning about a topic. The hardest part of being really good at something is this difference between knowledge and skill. I have recently taken several informative training classes with Kimball University on data warehousing and ETL. Now I have a lot more knowledge about designing data warehouses than before. I have also done a good bit of data warehouse designing of late and have started to improve to some level of proficiency with the theory. Yet, for all of this head knowledge, it is still a struggle to take what I have learned and apply it to the designs I am working on.  Data warehousing is still a task that is not yet deeply ingrained in my brain muscle memory. On the other hand, relational database design is something that no matter how much or how little I may get to do it, I am comfortable doing it. I have done it as a profession now for well over a decade, I teach classes on it, and I also have done (and continue to do) a lot of mental training beyond the work day. Sometimes the training is just basic education, some reading blogs and attending sessions at PASS events.  My best training comes from spending time working on other people’s design issues in forums (though not nearly as much as I would like to lately). Working through other people’s problems is a great way to exercise your brain on problems with which you’re not immediately familiar. The final bit of exercise I find useful for cultivating mental fitness for a data professional is also probably the nerdiest thing that I will ever suggest you do.  Akin to running in place, the idea is to work through designs in your head. I have designed more than one database system that would revolutionize grocery store operations, sales at my local Target store, the ordering process at Amazon, and ways to improve Disney World operations to get me through a line faster (some of which they are starting to implement without any of my help.) Never are the designs truly fleshed out, but enough to work through structures and processes.  On “paper”, I have designed database systems to catalog things as trivial as my Lego creations, rental car companies and my audio and video collections. Once I get the database designed mentally, sometimes I will create the database, add some data (often using Red-Gate’s Data Generator), and write a few queries to see if a concept was realistic, but I will rarely fully flesh out the database since I have no desire to do any user interface programming anymore.  The mental training allows me to keep in practice for when the time comes to do the work I love the most for real…even if I have been spending most of my work time lately building data warehouses.  If you are really strong of mind and body, perhaps you can mix a mental run with a physical run; though don’t run off of a cliff while contemplating how you might design a database to catalog the trees on a mountain…that would be contradictory to the purpose of both types of exercise.

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• Managing Data Growth in SQL Server

  'Help, my database ate my disk drives!'. Many DBAs spend most of their time dealing with variations of the problem of database processes consuming too much disk space. This happens because of errors such as incorrect configurations for recovery models, data growth for large objects and queries that overtax TempDB resources. Rodney describes, with some feeling, the errors that can lead to this sort of crisis for the working DBA, and their solution.

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• Resolving an App-Relative URL without a Page Object Reference

  - by Damon

  If you've worked with ASP.NET before then you've almost certainly seen an application-relative URL like ~/SomeFolder/SomePage.aspx.  The tilde at the beginning is a stand in for the application path, and it can easily be resolved using the Page object's ResolveUrl method: string url = Page.ResolveUrl("~/SomeFolder/SomePage.aspx"); There are times, however, when you don't have a page object available and you need to resolve an application relative URL.  Assuming you have an HttpContext object available, the following method will accomplish just that: public static string ResolveAppRelativeUrl(string url) {      return url.Replace("~", System.Web.HttpContext.Current.Request.ApplicationPath); } It just replaces the tilde with the application path, which is essentially all the ResolveUrl method does.

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• Got that Friday feeling?

  - by Rebecca Amos

  Saturday is just around the corner, and we’re all starting to wrap up for the weekend. If you’re the DBA that ‘Friday feeling’ might be as much about checking and preparing your SQL Servers for the next two days, as about looking forward to spending time with friends and family. Whether you’re double-checking your disaster recovery strategy, or know that it’s your turn to be on-call this weekend, it’s likely you’re preparing for the worst, just in case. The fact that you’re making these checks, and caring about both your servers and your users, means that you might be an exceptional DBA. You’re already putting in that extra effort to make other people’s lives easier. So why not take some time for your professional development and enter the Exceptional DBA Awards? If you’re looking for some inspiration for your entry, download our Judges’ Top Tips poster for advice on what the judges are looking for from this year’s entrants. Not only will you be boosting your professional development, but you could win full conference registration for the 2011 PASS Summit in Seattle (where the awards ceremony will take place), four nights' hotel accommodation, and a copy of Red Gate’s SQL DBA Bundle. So take some time out for yourself this weekend and get started on your entry: www.exceptionaldba.com

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