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

  - by Pinal Dave

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

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• Web API, JavaScript, Chrome &amp; Cross-Origin Resource Sharing

  - by Brian Lanham

  The team spent much of the week working through this issues related to Chrome running on Windows 8 consuming cross-origin resources using Web API.  We thought it was resolved on day 2 but it resurfaced the next day.  We definitely resolved it today though.  I believe I do not fully understand the situation but I am going to explain what I know in an effort to help you avoid and/or resolve a similar issue. References We referenced many sources during our trial-and-error troubleshooting.  These are the links we reference in order of applicability to the solution: Zoiner Tejada JavaScript and other material from -> http://www.devproconnections.com/content1/topic/microsoft-azure-cors-141869/catpath/windows-azure-platform2/page/3 WebDAV Where I learned about “Accept” –>  http://www-jo.se/f.pfleger/cors-and-iis? IT Hit Tells about NOT using ‘*’ –> http://www.webdavsystem.com/ajax/programming/cross_origin_requests Carlos Figueira Sample back-end code (newer) –> http://code.msdn.microsoft.com/windowsdesktop/Implementing-CORS-support-a677ab5d (older version) –> http://code.msdn.microsoft.com/CORS-support-in-ASPNET-Web-01e9980a   Background As a measure of protection, Web designers (W3C) and implementers (Google, Microsoft, Mozilla) made it so that a request, especially a JSON request (but really any URL), sent from one domain to another will only work if the requestee “knows” about the requester and allows requests from it. So, for example, if you write a ASP.NET MVC Web API service and try to consume it from multiple apps, the browsers used may (will?) indicate that you are not allowed by showing an “Access-Control-Allow-Origin” error indicating the requester is not allowed to make requests. Internet Explorer (big surprise) is the odd-hair-colored step-child in this mix. It seems that running locally at least IE allows this for development purposes.  Chrome and Firefox do not.  In fact, Chrome is quite restrictive.  Notice the images below. IE shows data (a tabular view with one row for each day of a week) while Chrome does not (trust me, neither does Firefox).  Further, the Chrome developer console shows an XmlHttpRequest (XHR) error. Screen captures from IE (left) and Chrome (right). Note that Chrome does not display data and the console shows an XHR error. Why does this happen? The Web browser submits these requests and processes the responses and each browser is different. Okay, so, IE is probably the only one that’s truly different.  However, Chrome has a specific process of performing a “pre-flight” check to make sure the service can respond to an “Access-Control-Allow-Origin” or Cross-Origin Resource Sharing (CORS) request.  So basically, the sequence is, if I understand correctly:  1)Page Loads –> 2)JavaScript Request Processed by Browser –> 3)Browsers Prepares to Submit Request –> 4)[Chrome] Browser Submits Pre-Flight Request –> 5)Server Responds with HTTP 200 –> 6)Browser Submits Request –> 7)Server Responds with Data –> 8)Page Shows Data This situation occurs for both GET and POST methods.  Typically, GET methods are called with query string parameters so there is no data posted.  Instead, the requesting domain needs to be permitted to request data but generally nothing more is required.  POSTs on the other hand send form data.  Therefore, more configuration is required (you’ll see the configuration below).  AJAX requests are not friendly with this (POSTs) either because they don’t post in a form. How to fix it. The team went through many iterations of self-hair removal and we think we finally have a working solution.  The trial-and-error approach eventually worked and we referenced many sources for the information.  I indicate those references above.  There are basically three (3) tasks needed to make this work. Assumptions: You are using Visual Studio, Web API, JavaScript, and have Cross-Origin Resource Sharing, and several browsers. 1. Configure the client Joel Cochran centralized our “cors-oriented” JavaScript (from here). There are two calls including one for GET and one for POST function(url, data, callback) {             console.log(data);             $.support.cors = true;             var jqxhr = $.post(url, data, callback, "json")                 .error(function(jqXhHR, status, errorThrown) {                     if ($.browser.msie && window.XDomainRequest) {                         var xdr = new XDomainRequest();                         xdr.open("post", url);                         xdr.onload = function () {                             if (callback) {                                 callback(JSON.parse(this.responseText), 'success');                             }                         };                         xdr.send(data);                     } else {                         console.log(">" + jqXhHR.status);                         alert("corsAjax.post error: " + status + ", " + errorThrown);                     }                 });         }; The GET CORS JavaScript function (credit to Zoiner Tejada) function(url, callback) {             $.support.cors = true;             var jqxhr = $.get(url, null, callback, "json")                 .error(function(jqXhHR, status, errorThrown) {                     if ($.browser.msie && window.XDomainRequest) {                         var xdr = new XDomainRequest();                         xdr.open("get", url);                         xdr.onload = function () {                             if (callback) {                                 callback(JSON.parse(this.responseText), 'success');                             }                         };                         xdr.send();                     } else {                         alert("CORS is not supported in this browser or from this origin.");                     }                 });         }; The POST CORS JavaScript function (credit to Zoiner Tejada) Now you need to call these functions to get and post your data (instead of, say, using $.Ajax). Here is a GET example: corsAjax.get(url, function(data) { if (data !== null && data.length !== undefined) { // do something with data } }); And here is a POST example: corsAjax.post(url, item); Simple…except…you’re not done yet. 2. Change Web API Controllers to Allow CORS There are actually two steps here.  Do you remember above when we mentioned the “pre-flight” check?  Chrome actually asks the server if it is allowed to ask it for cross-origin resource sharing access.  So you need to let the server know it’s okay.  This is a two-part activity.  a) Add the appropriate response header Access-Control-Allow-Origin, and b) permit the API functions to respond to various methods including GET, POST, and OPTIONS.  OPTIONS is the method that Chrome and other browsers use to ask the server if it can ask about permissions.  Here is an example of a Web API controller thus decorated: NOTE: You’ll see a lot of references to using “*” in the header value.  For security reasons, Chrome does NOT recognize this is valid. [HttpHeader("Access-Control-Allow-Origin", "http://localhost:51234")] [HttpHeader("Access-Control-Allow-Credentials", "true")] [HttpHeader("Access-Control-Allow-Methods", "ACCEPT, PROPFIND, PROPPATCH, COPY, MOVE, DELETE, MKCOL, LOCK, UNLOCK, PUT, GETLIB, VERSION-CONTROL, CHECKIN, CHECKOUT, UNCHECKOUT, REPORT, UPDATE, CANCELUPLOAD, HEAD, OPTIONS, GET, POST")] [HttpHeader("Access-Control-Allow-Headers", "Accept, Overwrite, Destination, Content-Type, Depth, User-Agent, X-File-Size, X-Requested-With, If-Modified-Since, X-File-Name, Cache-Control")] [HttpHeader("Access-Control-Max-Age", "3600")] public abstract class BaseApiController : ApiController {     [HttpGet]     [HttpOptions]     public IEnumerable<foo> GetFooItems(int id)     {         return foo.AsEnumerable();     }     [HttpPost]     [HttpOptions]     public void UpdateFooItem(FooItem fooItem)     {         // NOTE: The fooItem object may or may not         // (probably NOT) be set with actual data.         // If not, you need to extract the data from         // the posted form manually.         if (fooItem.Id == 0) // However you check for default...         {             // We use NewtonSoft.Json.             string jsonString = context.Request.Form.GetValues(0)[0].ToString();             Newtonsoft.Json.JsonSerializer js = new Newtonsoft.Json.JsonSerializer();             fooItem = js.Deserialize<FooItem>(new Newtonsoft.Json.JsonTextReader(new System.IO.StringReader(jsonString)));         }         // Update the set fooItem object.     } } Please note a few specific additions here: * The header attributes at the class level are required.  Note all of those methods and headers need to be specified but we find it works this way so we aren’t touching it. * Web API will actually deserialize the posted data into the object parameter of the called method on occasion but so far we don’t know why it does and doesn’t. * [HttpOptions] is, again, required for the pre-flight check. * The “Access-Control-Allow-Origin” response header should NOT NOT NOT contain an ‘*’. 3. Headers and Methods and Such We had most of this code in place but found that Chrome and Firefox still did not render the data.  Interestingly enough, Fiddler showed that the GET calls succeeded and the JSON data is returned properly.  We learned that among the headers set at the class level, we needed to add “ACCEPT”.  Note that I accidentally added it to methods and to headers.  Adding it to methods worked but I don’t know why.  We added it to headers also for good measure. [HttpHeader("Access-Control-Allow-Methods", "ACCEPT, PROPFIND, PROPPA... [HttpHeader("Access-Control-Allow-Headers", "Accept, Overwrite, Destin... Next Steps That should do it.  If it doesn’t let us know.  What to do next?  * Don’t hardcode the allowed domains.  Note that port numbers and other domain name specifics will cause problems and must be specified.  If this changes do you really want to deploy updated software?  Consider Miguel Figueira’s approach in the following link to writing a custom HttpHeaderAttribute class that allows you to specify the domain names and then you can do it dynamically.  There are, of course, other ways to do it dynamically but this is a clean approach. http://code.msdn.microsoft.com/windowsdesktop/Implementing-CORS-support-a677ab5d

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• Spooling in SQL execution plans

  - by Rob Farley

  Sewing has never been my thing. I barely even know the terminology, and when discussing this with American friends, I even found out that half the words that Americans use are different to the words that English and Australian people use. That said – let’s talk about spools! In particular, the Spool operators that you find in some SQL execution plans. This post is for T-SQL Tuesday, hosted this month by me! I’ve chosen to write about spools because they seem to get a bad rap (even in my song I used the line “There’s spooling from a CTE, they’ve got recursion needlessly”). I figured it was worth covering some of what spools are about, and hopefully explain why they are remarkably necessary, and generally very useful. If you have a look at the Books Online page about Plan Operators, at http://msdn.microsoft.com/en-us/library/ms191158.aspx, and do a search for the word ‘spool’, you’ll notice it says there are 46 matches. 46! Yeah, that’s what I thought too... Spooling is mentioned in several operators: Eager Spool, Lazy Spool, Index Spool (sometimes called a Nonclustered Index Spool), Row Count Spool, Spool, Table Spool, and Window Spool (oh, and Cache, which is a special kind of spool for a single row, but as it isn’t used in SQL 2012, I won’t describe it any further here). Spool, Table Spool, Index Spool, Window Spool and Row Count Spool are all physical operators, whereas Eager Spool and Lazy Spool are logical operators, describing the way that the other spools work. For example, you might see a Table Spool which is either Eager or Lazy. A Window Spool can actually act as both, as I’ll mention in a moment. In sewing, cotton is put onto a spool to make it more useful. You might buy it in bulk on a cone, but if you’re going to be using a sewing machine, then you quite probably want to have it on a spool or bobbin, which allows it to be used in a more effective way. This is the picture that I want you to think about in relation to your data. I’m sure you use spools every time you use your sewing machine. I know I do. I can’t think of a time when I’ve got out my sewing machine to do some sewing and haven’t used a spool. However, I often run SQL queries that don’t use spools. You see, the data that is consumed by my query is typically in a useful state without a spool. It’s like I can just sew with my cotton despite it not being on a spool! Many of my favourite features in T-SQL do like to use spools though. This looks like a very similar query to before, but includes an OVER clause to return a column telling me the number of rows in my data set. I’ll describe what’s going on in a few paragraphs’ time. So what does a Spool operator actually do? The spool operator consumes a set of data, and stores it in a temporary structure, in the tempdb database. This structure is typically either a Table (ie, a heap), or an Index (ie, a b-tree). If no data is actually needed from it, then it could also be a Row Count spool, which only stores the number of rows that the spool operator consumes. A Window Spool is another option if the data being consumed is tightly linked to windows of data, such as when the ROWS/RANGE clause of the OVER clause is being used. You could maybe think about the type of spool being like whether the cotton is going onto a small bobbin to fit in the base of the sewing machine, or whether it’s a larger spool for the top. A Table or Index Spool is either Eager or Lazy in nature. Eager and Lazy are Logical operators, which talk more about the behaviour, rather than the physical operation. If I’m sewing, I can either be all enthusiastic and get all my cotton onto the spool before I start, or I can do it as I need it. “Lazy” might not the be the best word to describe a person – in the SQL world it describes the idea of either fetching all the rows to build up the whole spool when the operator is called (Eager), or populating the spool only as it’s needed (Lazy). Window Spools are both physical and logical. They’re eager on a per-window basis, but lazy between windows. And when is it needed? The way I see it, spools are needed for two reasons. 1 – When data is going to be needed AGAIN. 2 – When data needs to be kept away from the original source. If you’re someone that writes long stored procedures, you are probably quite aware of the second scenario. I see plenty of stored procedures being written this way – where the query writer populates a temporary table, so that they can make updates to it without risking the original table. SQL does this too. Imagine I’m updating my contact list, and some of my changes move data to later in the book. If I’m not careful, I might update the same row a second time (or even enter an infinite loop, updating it over and over). A spool can make sure that I don’t, by using a copy of the data. This problem is known as the Halloween Effect (not because it’s spooky, but because it was discovered in late October one year). As I’m sure you can imagine, the kind of spool you’d need to protect against the Halloween Effect would be eager, because if you’re only handling one row at a time, then you’re not providing the protection... An eager spool will block the flow of data, waiting until it has fetched all the data before serving it up to the operator that called it. In the query below I’m forcing the Query Optimizer to use an index which would be upset if the Name column values got changed, and we see that before any data is fetched, a spool is created to load the data into. This doesn’t stop the index being maintained, but it does mean that the index is protected from the changes that are being done. There are plenty of times, though, when you need data repeatedly. Consider the query I put above. A simple join, but then counting the number of rows that came through. The way that this has executed (be it ideal or not), is to ask that a Table Spool be populated. That’s the Table Spool operator on the top row. That spool can produce the same set of rows repeatedly. This is the behaviour that we see in the bottom half of the plan. In the bottom half of the plan, we see that the a join is being done between the rows that are being sourced from the spool – one being aggregated and one not – producing the columns that we need for the query. Table v Index When considering whether to use a Table Spool or an Index Spool, the question that the Query Optimizer needs to answer is whether there is sufficient benefit to storing the data in a b-tree. The idea of having data in indexes is great, but of course there is a cost to maintaining them. Here we’re creating a temporary structure for data, and there is a cost associated with populating each row into its correct position according to a b-tree, as opposed to simply adding it to the end of the list of rows in a heap. Using a b-tree could even result in page-splits as the b-tree is populated, so there had better be a reason to use that kind of structure. That all depends on how the data is going to be used in other parts of the plan. If you’ve ever thought that you could use a temporary index for a particular query, well this is it – and the Query Optimizer can do that if it thinks it’s worthwhile. It’s worth noting that just because a Spool is populated using an Index Spool, it can still be fetched using a Table Spool. The details about whether or not a Spool used as a source shows as a Table Spool or an Index Spool is more about whether a Seek predicate is used, rather than on the underlying structure. Recursive CTE I’ve already shown you an example of spooling when the OVER clause is used. You might see them being used whenever you have data that is needed multiple times, and CTEs are quite common here. With the definition of a set of data described in a CTE, if the query writer is leveraging this by referring to the CTE multiple times, and there’s no simplification to be leveraged, a spool could theoretically be used to avoid reapplying the CTE’s logic. Annoyingly, this doesn’t happen. Consider this query, which really looks like it’s using the same data twice. I’m creating a set of data (which is completely deterministic, by the way), and then joining it back to itself. There seems to be no reason why it shouldn’t use a spool for the set described by the CTE, but it doesn’t. On the other hand, if we don’t pull as many columns back, we might see a very different plan. You see, CTEs, like all sub-queries, are simplified out to figure out the best way of executing the whole query. My example is somewhat contrived, and although there are plenty of cases when it’s nice to give the Query Optimizer hints about how to execute queries, it usually doesn’t do a bad job, even without spooling (and you can always use a temporary table). When recursion is used, though, spooling should be expected. Consider what we’re asking for in a recursive CTE. We’re telling the system to construct a set of data using an initial query, and then use set as a source for another query, piping this back into the same set and back around. It’s very much a spool. The analogy of cotton is long gone here, as the idea of having a continual loop of cotton feeding onto a spool and off again doesn’t quite fit, but that’s what we have here. Data is being fed onto the spool, and getting pulled out a second time when the spool is used as a source. (This query is running on AdventureWorks, which has a ManagerID column in HumanResources.Employee, not AdventureWorks2012) The Index Spool operator is sucking rows into it – lazily. It has to be lazy, because at the start, there’s only one row to be had. However, as rows get populated onto the spool, the Table Spool operator on the right can return rows when asked, ending up with more rows (potentially) getting back onto the spool, ready for the next round. (The Assert operator is merely checking to see if we’ve reached the MAXRECURSION point – it vanishes if you use OPTION (MAXRECURSION 0), which you can try yourself if you like). Spools are useful. Don’t lose sight of that. Every time you use temporary tables or table variables in a stored procedure, you’re essentially doing the same – don’t get upset at the Query Optimizer for doing so, even if you think the spool looks like an expensive part of the query. I hope you’re enjoying this T-SQL Tuesday. Why not head over to my post that is hosting it this month to read about some other plan operators? At some point I’ll write a summary post – once I have you should find a comment below pointing at it. @rob_farley

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• The UIManager Pattern

  - by Duncan Mills

  One of the most common mistakes that I see when reviewing ADF application code, is the sin of storing UI component references, most commonly things like table or tree components in Session or PageFlow scope. The reasons why this is bad are simple; firstly, these UI object references are not serializable so would not survive a session migration between servers and secondly there is no guarantee that the framework will re-use the same component tree from request to request, although in practice it generally does do so. So there danger here is, that at best you end up with an NPE after you session has migrated, and at worse, you end up pinning old generations of the component tree happily eating up your precious memory. So that's clear, we should never. ever, be storing references to components anywhere other than request scope (or maybe backing bean scope). So double check the scope of those binding attributes that map component references into a managed bean in your applications.  Why is it Such a Common Mistake?  At this point I want to examine why there is this urge to hold onto these references anyway? After all, JSF will obligingly populate your backing beans with the fresh and correct reference when needed.   In most cases, it seems that the rational is down to a lack of distinction within the application between what is data and what is presentation. I think perhaps, a cause of this is the logical separation between business data behind the ADF data binding (#{bindings}) façade and the UI components themselves. Developers tend to think, OK this is my data layer behind the bindings object and everything else is just UI.  Of course that's not the case.  The UI layer itself will have state which is intrinsically linked to the UI presentation rather than the business model, but at the same time should not be tighly bound to a specific instance of any single UI component. So here's the problem.  I think developers try and use the UI components as state-holders for this kind of data, rather than using them to represent that state. An example of this might be something like the selection state of a tabset (panelTabbed), you might be interested in knowing what the currently disclosed tab is. The temptation that leads to the component reference sin is to go and ask the tabset what the selection is.  That of course is fine in context - e.g. a handler within the same request scoped bean that's got the binding to the tabset. However, it leads to problems when you subsequently want the same information outside of the immediate scope.  The simple solution seems to be to chuck that component reference into session scope and then you can simply re-check in the same way, leading of course to this mistake. Turn it on its Head  So the correct solution to this is to turn the problem on its head. If you are going to be interested in the value or state of some component outside of the immediate request context then it becomes persistent state (persistent in the sense that it extends beyond the lifespan of a single request). So you need to externalize that state outside of the component and have the component reference and manipulate that state as needed rather than owning it. This is what I call the UIManager pattern.  Defining the Pattern The  UIManager pattern really is very simple. The premise is that every application should define a session scoped managed bean, appropriately named UIManger, which is specifically responsible for holding this persistent UI component related state.  The actual makeup of the UIManger class varies depending on a needs of the application and the amount of state that needs to be stored. Generally I'll start off with a Map in which individual flags can be created as required, although you could opt for a more formal set of typed member variables with getters and setters, or indeed a mix. This UIManager class is defined as a session scoped managed bean (#{uiManager}) in the faces-config.xml.  The pattern is to then inject this instance of the class into any other managed bean (usually request scope) that needs it using a managed property.  So typically you'll have something like this:   <managed-bean>     <managed-bean-name>uiManager</managed-bean-name>     <managed-bean-class>oracle.demo.view.state.UIManager</managed-bean-class>     <managed-bean-scope>session</managed-bean-scope>   </managed-bean>  When is then injected into any backing bean that needs it:    <managed-bean>     <managed-bean-name>mainPageBB</managed-bean-name>     <managed-bean-class>oracle.demo.view.MainBacking</managed-bean-class>     <managed-bean-scope>request</managed-bean-scope>     <managed-property>       <property-name>uiManager</property-name>       <property-class>oracle.demo.view.state.UIManager</property-class>       <value>#{uiManager}</value>     </managed-property>   </managed-bean> In this case the backing bean in question needs a member variable to hold and reference the UIManager: private UIManager _uiManager;  Which should be exposed via a getter and setter pair with names that match the managed property name (e.g. setUiManager(UIManager _uiManager), getUiManager()).  This will then give your code within the backing bean full access to the UI state. UI components in the page can, of course, directly reference the uiManager bean in their properties, for example, going back to the tab-set example you might have something like this: <af:paneltabbed>   <af:showDetailItem text="First"                disclosed="#{uiManager.settings['MAIN_TABSET_STATE'].['FIRST']}"> ...   </af:showDetailItem>   <af:showDetailItem text="Second"                      disclosed="#{uiManager.settings['MAIN_TABSET_STATE'].['SECOND']}">     ...   </af:showDetailItem>   ... </af:panelTabbed> Where in this case the settings member within the UI Manger is a Map which contains a Map of Booleans for each tab under the MAIN_TABSET_STATE key. (Just an example you could choose to store just an identifier for the selected tab or whatever, how you choose to store the state within UI Manger is up to you.) Get into the Habit So we can see that the UIManager pattern is not great strain to implement for an application and can even be retrofitted to an existing application with ease. The point is, however, that you should always take this approach rather than committing the sin of persistent component references which will bite you in the future or shotgun scattered UI flags on the session which are hard to maintain.  If you take the approach of always accessing all UI state via the uiManager, or perhaps a pageScope focused variant of it, you'll find your applications much easier to understand and maintain. Do it today!

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• Day 6 - Game Menuing Woes and Future Screen Sneak Peeks

  - by dapostolov

  So, after my last post on Day 5 I dabbled with my game class design. I took the approach where each game objects is tightly coupled with a graphic. The good news is I got the menu working but not without some hard knocks and game growing pains. I'll explain later, but for now...here is a class diagram of my first stab at my class structure and some code...   Ok, there are few mistakes, however, I'm going to leave it as is for now... As you can see I created an inital abstract base class called GameSprite. This class when inherited will provide a simple virtual default draw method:        public virtual void DrawSprite(SpriteBatch spriteBatch)         {             spriteBatch.Draw(Sprite, Position, Color.White);         } The benefits of coding it this way allows me to inherit the class and utilise the method in the screen draw method...So regardless of what the graphic object type is it will now have the ability to render a static image on the screen. Example: public class MyStaticTreasureChest : GameSprite {} If you remember the window draw method from Day 3's post, we could use the above code as follows...         protected override void Draw(GameTime gameTime)         {             GraphicsDevice.Clear(Color.CornflowerBlue);             spriteBatch.Begin(SpriteBlendMode.AlphaBlend);             foreach(var gameSprite in ListOfGameObjects)            {                 gameSprite.DrawSprite(spriteBatch);            }             spriteBatch.End();             base.Draw(gameTime);         } I have to admit the GameSprite object is pretty plain as with its DrawSprite method... But ... we now have the ability to render 3 static menu items on the screen ... BORING! I want those menu items to do something exciting, which of course involves animation... So, let's have a peek at AnimatedGameSprite in the above game diagram. The idea with the AnimatedGameSprite is that it has an image to animate...such as ... characters, fireballs, and... menus! So after inheriting from GameSprite class, I added a few more options such as UpdateSprite...         public virtual void UpdateSprite(float elapsed)         {             _totalElapsed += elapsed;             if (_totalElapsed > _timePerFrame)             {                 _frame++;                 _frame = _frame % _framecount;                 _totalElapsed -= _timePerFrame;             }         }  And an overidden DrawSprite...         public override void DrawSprite(SpriteBatch spriteBatch)         {             int FrameWidth = Sprite.Width / _framecount;             Rectangle sourcerect = new Rectangle(FrameWidth * _frame, 0, FrameWidth, Sprite.Height);             spriteBatch.Draw(Sprite, Position, sourcerect, Color.White, _rotation, _origin, _scale, SpriteEffects.None, _depth);         } With these two methods...I can animate and image, all I had to do was add a few more lines to the screens Update Method (From Day 3), like such:             float elapsed = (float) gameTime.ElapsedGameTime.TotalSeconds;             foreach (var item in ListOfAnimatedGameObjects)             {                 item.UpdateSprite(elapsed);             } And voila! My images begin to animate in one spot, on the screen... Hmm, but how do I interact with the menu items using a mouse...well the mouse cursor was easy enough... this.IsMouseVisible = true; But, to have it "interact" with an image was a bit more tricky...I had to perform collision detection!             mouseStateCurrent = Mouse.GetState();             var uiEnabledSprites = (from s in menuItems                                    where s.IsEnabled                                    select s).ToList();             foreach (var item in uiEnabledSprites)             {                 var r = new Rectangle((int)item.Position.X, (int)item.Position.Y, item.Sprite.Width, item.Sprite.Height);                 item.MenuState = MenuState.Normal;                 if (r.Intersects(new Rectangle(mouseStateCurrent.X, mouseStateCurrent.Y, 0, 0)))                 {                     item.MenuState = MenuState.Hover;                     if (mouseStatePrevious.LeftButton == ButtonState.Pressed                         && mouseStateCurrent.LeftButton == ButtonState.Released)                     {                         item.MenuState = MenuState.Pressed;                     }                 }             }             mouseStatePrevious = mouseStateCurrent; So, basically, what it is doing above is iterating through all my interactive objects and detecting a rectangle collision and the object , plays the state animation (or static image).  Lessons Learned, Time Burned... So, I think I did well to start, but after I hammered out my prototype...well...things got sloppy and I began to realise some design flaws... At the time: I couldn't seem to figure out how to open another window, such as the character creation screen Input was not event based and it was bugging me My menu design relied heavily on mouse input and I couldn't use keyboard. Mouse input, is tightly bound with graphic rendering / positioning, so its logic will have to be in each scene. Menu animations would stop mid frame, then continue when the action occured again. This is bad, because...what if I had a sword sliding onthe screen? Then it would slide a quarter of the way, then stop due to another action, then render again mid-slide... it just looked sloppy. Menu, Solved!? To solve the above problems I did a little research and I found some great code in the XNA forums. The one worth mentioning was the GameStateManagementSample. With this sample, you can create a basic "text based" menu system which allows you to swap screens, popup screens, play the game, and quit....basic game state management... In my next post I'm going to dwelve a bit more into this code and adapt it with my code from this prototype. Text based menus just won't cut it for me, for now...however, I'm still going to stick with my animated menu item idea. A sneak peek using the Game State Management Sample...with no changes made... Cool Things to Mention: At work ... I tend to break out in random conversations every-so-often and I get talking about some of my challenges with this game (or some stupid observation about something... stupid) During one conversation I was discussing how I should animate my images; I explained that I knew I had to use the Update method provided, but I didn't know how (at the time) to render an image at an appropriate "pace" and how many frames to use, etc.. I also got thinking that if a machine rendered my images faster / slower, that was surely going to f-up my animations. To which a friend, Sheldon,  answered, surely the Draw method is like a camera taking a snapshot of a scene in time. Then it clicked...I understood the big picture of the game engine... After some research I discovered that the Draw method attempts to keep a framerate of 60 fps. From what I understand, the game engine will even leave out a few calls to the draw method if it begins to slow down. This is why we want to put our sprite updates in the update method. Then using a game timer (provided by the engine), we want to render the scene based on real time passed, not framerate. So even the engine renders at 20 fps, the animations will still animate at the same real time speed! Which brings up another point. Why 60 fps? I'm speculating that Microsoft capped it because LCD's dont' refresh faster than 60 fps? On another note, If the game engine knows its falling behind in rendering...then surely we can harness this to speed up our games. Maybe I can find some flag which tell me if the game is lagging, and what the current framerate is, etc...(instead of coding it like I did last time) Sheldon, suggested maybe I can render like WoW does, in prioritised layers...I think he's onto something, however I don't think I'll have that many graphics to worry about such a problem of graphic latency. We'll see. People to Mention: Well,as you are aware I hadn't posted in a couple days and I was surprised to see a few emails and messenger queries about my game progress (and some concern as to why I stopped). I want to thank everyone for their kind words of support and put everyone at ease by stating that I do intend on completing this project. Granted I only have a few hours each night, but, I'll do it. Thank you to Garth for mailing in my next screen! That was a nice surprise! The Sneek Peek you've been waiting for... Garth has also volunteered to render me some wizard images. He was a bit shocked when I asked for them in 2D animated strips. He said I was going backward (and that I have really bad Game Development Lingo). But, I advised Garth that I will use 3D images later...for now...2D images. Garth also had some great game design ideas to add on. I advised him that I will save his ideas and include them in the future design document (for the 3d version?). Lastly, my best friend Alek, is going to join me in developing this game. This was a project we started eons ago but never completed because of our careers. Now, priorities change and we have some spare time on our hands. Let's see what trouble Alek and I can get into! Tonight I'll be uploading my prototypes and base game to a source control for both of us to work off of. D.

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• Code Reuse is (Damn) Hard

  - by James Michael Hare

  Being a development team lead, the task of interviewing new candidates was part of my job.  Like any typical interview, we started with some easy questions to get them warmed up and help calm their nerves before hitting the hard stuff. One of those easier questions was almost always: “Name some benefits of object-oriented development.”  Nearly every time, the candidate would chime in with a plethora of canned answers which typically included: “it helps ease code reuse.”  Of course, this is a gross oversimplification.  Tools only ease reuse, its developers that ultimately can cause code to be reusable or not, regardless of the language or methodology. But it did get me thinking…  we always used to say that as part of our mantra as to why Object-Oriented Programming was so great.  With polymorphism, inheritance, encapsulation, etc. we in essence set up the concepts to help facilitate reuse as much as possible.  And yes, as a developer now of many years, I unquestionably held that belief for ages before it really struck me how my views on reuse have jaded over the years.  In fact, in many ways Agile rightly eschews reuse as taking a backseat to developing what's needed for the here and now.  It used to be I was in complete opposition to that view, but more and more I've come to see the logic in it.  Too many times I've seen developers (myself included) get lost in design paralysis trying to come up with the perfect abstraction that would stand all time.  Nearly without fail, all of these pieces of code become obsolete in a matter of months or years. It’s not that I don’t like reuse – it’s just that reuse is hard.  In fact, reuse is DAMN hard.  Many times it is just a distraction that eats up architect and developer time, and worse yet can be counter-productive and force wrong decisions.  Now don’t get me wrong, I love the idea of reusable code when it makes sense.  These are in the few cases where you are designing something that is inherently reusable.  The problem is, most business-class code is inherently unfit for reuse! Furthermore, the code that is reusable will often fail to be reused if you don’t have the proper framework in place for effective reuse that includes standardized versioning, building, releasing, and documenting the components.  That should always be standard across the board when promoting reusable code.  All of this is hard, and it should only be done when you have code that is truly reusable or you will be exerting a large amount of development effort for very little bang for your buck. But my goal here is not to get into how to reuse (that is a topic unto itself) but what should be reused.  First, let’s look at an extension method.  There’s many times where I want to kick off a thread to handle a task, then when I want to reign that thread in of course I want to do a Join on it.  But what if I only want to wait a limited amount of time and then Abort?  Well, I could of course write that logic out by hand each time, but it seemed like a great extension method: 1: public static class ThreadExtensions 2: { 3: public static bool JoinOrAbort(this Thread thread, TimeSpan timeToWait) 4: { 5: bool isJoined = false; 6:  7: if (thread != null) 8: { 9: isJoined = thread.Join(timeToWait); 10:  11: if (!isJoined) 12: { 13: thread.Abort(); 14: } 15: } 16: return isJoined; 17: } 18: } 19:  When I look at this code, I can immediately see things that jump out at me as reasons why this code is very reusable.  Some of them are standard OO principles, and some are kind-of home grown litmus tests: Single Responsibility Principle (SRP) – The only reason this extension method need change is if the Thread class itself changes (one responsibility). Stable Dependencies Principle (SDP) – This method only depends on classes that are more stable than it is (System.Threading.Thread), and in itself is very stable, hence other classes may safely depend on it. It is also not dependent on any business domain, and thus isn't subject to changes as the business itself changes. Open-Closed Principle (OCP) – This class is inherently closed to change. Small and Stable Problem Domain – This method only cares about System.Threading.Thread. All-or-None Usage – A user of a reusable class should want the functionality of that class, not parts of that functionality.  That’s not to say they most use every method, but they shouldn’t be using a method just to get half of its result. Cost of Reuse vs. Cost to Recreate – since this class is highly stable and minimally complex, we can offer it up for reuse very cheaply by promoting it as “ready-to-go” and already unit tested (important!) and available through a standard release cycle (very important!). Okay, all seems good there, now lets look at an entity and DAO.  I don’t know about you all, but there have been times I’ve been in organizations that get the grand idea that all DAOs and entities should be standardized and shared.  While this may work for small or static organizations, it’s near ludicrous for anything large or volatile. 1: namespace Shared.Entities 2: { 3: public class Account 4: { 5: public int Id { get; set; } 6:  7: public string Name { get; set; } 8:  9: public Address HomeAddress { get; set; } 10:  11: public int Age { get; set;} 12:  13: public DateTime LastUsed { get; set; } 14:  15: // etc, etc, etc... 16: } 17: } 18:  19: ... 20:  21: namespace Shared.DataAccess 22: { 23: public class AccountDao 24: { 25: public Account FindAccount(int id) 26: { 27: // dao logic to query and return account 28: } 29:  30: ... 31:  32: } 33: } Now to be fair, I’m not saying there doesn’t exist an organization where some entites may be extremely static and unchanging.  But at best such entities and DAOs will be problematic cases of reuse.  Let’s examine those same tests: Single Responsibility Principle (SRP) – The reasons to change for these classes will be strongly dependent on what the definition of the account is which can change over time and may have multiple influences depending on the number of systems an account can cover. Stable Dependencies Principle (SDP) – This method depends on the data model beneath itself which also is largely dependent on the business definition of an account which can be very inherently unstable. Open-Closed Principle (OCP) – This class is not really closed for modification.  Every time the account definition may change, you’d need to modify this class. Small and Stable Problem Domain – The definition of an account is inherently unstable and in fact may be very large.  What if you are designing a system that aggregates account information from several sources? All-or-None Usage – What if your view of the account encompasses data from 3 different sources but you only care about one of those sources or one piece of data?  Should you have to take the hit of looking up all the other data?  On the other hand, should you have ten different methods returning portions of data in chunks people tend to ask for?  Neither is really a great solution. Cost of Reuse vs. Cost to Recreate – DAOs are really trivial to rewrite, and unless your definition of an account is EXTREMELY stable, the cost to promote, support, and release a reusable account entity and DAO are usually far higher than the cost to recreate as needed. It’s no accident that my case for reuse was a utility class and my case for non-reuse was an entity/DAO.  In general, the smaller and more stable an abstraction is, the higher its level of reuse.  When I became the lead of the Shared Components Committee at my workplace, one of the original goals we looked at satisfying was to find (or create), version, release, and promote a shared library of common utility classes, frameworks, and data access objects.  Now, of course, many of you will point to nHibernate and Entity for the latter, but we were looking at larger, macro collections of data that span multiple data sources of varying types (databases, web services, etc). As we got deeper and deeper in the details of how to manage and release these items, it quickly became apparent that while the case for reuse was typically a slam dunk for utilities and frameworks, the data access objects just didn’t “smell” right.  We ended up having session after session of design meetings to try and find the right way to share these data access components. When someone asked me why it was taking so long to iron out the shared entities, my response was quite simple, “Reuse is hard...”  And that’s when I realized, that while reuse is an awesome goal and we should strive to make code maintainable, often times you end up creating far more work for yourself than necessary by trying to force code to be reusable that inherently isn’t. Think about classes the times you’ve worked in a company where in the design session people fight over the best way to implement a class to make it maximally reusable, extensible, and any other buzzwordable.  Then think about how quickly that design became obsolete.  Many times I set out to do a project and think, “yes, this is the best design, I can extend it easily!” only to find out the business requirements change COMPLETELY in such a way that the design is rendered invalid.  Code, in general, tends to rust and age over time.  As such, writing reusable code can often be difficult and many times ends up being a futile exercise and worse yet, sometimes makes the code harder to maintain because it obfuscates the design in the name of extensibility or reusability. So what do I think are reusable components? Generic Utility classes – these tend to be small classes that assist in a task and have no business context whatsoever. Implementation Abstraction Frameworks – home-grown frameworks that try to isolate changes to third party products you may be depending on (like writing a messaging abstraction layer for publishing/subscribing that is independent of whether you use JMS, MSMQ, etc). Simplification and Uniformity Frameworks – To some extent this is similar to an abstraction framework, but there may be one chosen provider but a development shop mandate to perform certain complex items in a certain way.  Or, perhaps to simplify and dumb-down a complex task for the average developer (such as implementing a particular development-shop’s method of encryption). And what are less reusable? Application and Business Layers – tend to fluctuate a lot as requirements change and new features are added, so tend to be an unstable dependency.  May be reused across applications but also very volatile. Entities and Data Access Layers – these tend to be tuned to the scope of the application, so reusing them can be hard unless the abstract is very stable. So what’s the big lesson?  Reuse is hard.  In fact it’s damn hard.  And much of the time I’m not convinced we should focus too hard on it. If you’re designing a utility or framework, then by all means design it for reuse.  But you most also really set down a good versioning, release, and documentation process to maximize your chances.  For anything else, design it to be maintainable and extendable, but don’t waste the effort on reusability for something that most likely will be obsolete in a year or two anyway.

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• SQL SERVER – Weekly Series – Memory Lane – #037

  - by Pinal Dave

  Here is the list of selected articles of SQLAuthority.com across all these years. Instead of just listing all the articles I have selected a few of my most favorite articles and have listed them here with additional notes below it. Let me know which one of the following is your favorite article from memory lane. 2007 Convert Text to Numbers (Integer) – CAST and CONVERT If table column is VARCHAR and has all the numeric values in it, it can be retrieved as Integer using CAST or CONVERT function. List All Stored Procedure Modified in Last N Days If SQL Server suddenly start behaving in un-expectable behavior and if stored procedure were changed recently, following script can be used to check recently modified stored procedure. If a stored procedure was created but never modified afterwards modified date and create a date for that stored procedure are same. Count Duplicate Records – Rows Validate Field For DATE datatype using function ISDATE() We always checked DATETIME field for incorrect data type. One of the user input date as 30/2/2007. The date was sucessfully inserted in the temp table but while inserting from temp table to final table it crashed with error. We had now task to validate incorrect date value before we insert in final table. Jr. Developer asked me how can he do that? We check for incorrect data type (varchar, int, NULL) but this is incorrect date value. Regular expression works fine with them because of mm/dd/yyyy format. 2008 Find Space Used For Any Particular Table It is very simple to find out the space used by any table in the database. Two Convenient Features Inline Assignment – Inline Operations Here is the script which does both – Inline Assignment and Inline Operation DECLARE @idx INT = 0 SET @idx+=1 SELECT @idx Introduction to SPARSE Columns SPARSE column are better at managing NULL and ZERO values in SQL Server. It does not take any space in database at all. If column is created with SPARSE clause with it and it contains ZERO or NULL it will be take lesser space then regular column (without SPARSE clause). SP_CONFIGURE – Displays or Changes Global Configuration Settings If advanced settings are not enabled at configuration level SQL Server will not let user change the advanced features on server. Authorized user can turn on or turn off advance settings. 2009 Standby Servers and Types of Standby Servers Standby Server is a type of server that can be brought online in a situation when Primary Server goes offline and application needs continuous (high) availability of the server. There is always a need to set up a mechanism where data and objects from primary server are moved to secondary (standby) server. BLOB – Pointer to Image, Image in Database, FILESTREAM Storage When it comes to storing images in database there are two common methods. I had previously blogged about the same subject on my visit to Toronto. With SQL Server 2008, we have a new method of FILESTREAM storage. However, the answer on when to use FILESTREAM and when to use other methods is still vague in community. 2010 Upper Case Shortcut SQL Server Management Studio I select the word and hit CTRL+SHIFT+U and it SSMS immediately changes the case of the selected word. Similar way if one want to convert cases to lower case, another short cut CTRL+SHIFT+L is also available. The Self Join – Inner Join and Outer Join Self Join has always been a noteworthy case. It is interesting to ask questions about self join in a room full of developers. I often ask – if there are three kinds of joins, i.e.- Inner Join, Outer Join and Cross Join; what type of join is Self Join? The usual answer is that it is an Inner Join. However, the reality is very different. Parallelism – Row per Processor – Row per Thread – Thread 0  If you look carefully in the Properties window or XML Plan, there is “Thread 0?. What does this “Thread 0” indicate? Well find out from the blog post. How do I Learn and How do I Teach The blog post has raised three very interesting questions. How do you learn? How do you teach? What are you learning or teaching? Let me try to answer the same. 2011 SQL SERVER – Interview Questions and Answers – Frequently Asked Questions – Day 7 of 31 What are Different Types of Locks? What are Pessimistic Lock and Optimistic Lock? When is the use of UPDATE_STATISTICS command? What is the Difference between a HAVING clause and a WHERE clause? What is Connection Pooling and why it is Used? What are the Properties and Different Types of Sub-Queries? What are the Authentication Modes in SQL Server? How can it be Changed? SQL SERVER – Interview Questions and Answers – Frequently Asked Questions – Day 8 of 31 Which Command using Query Analyzer will give you the Version of SQL Server and Operating System? What is an SQL Server Agent? Can a Stored Procedure call itself or a Recursive Stored Procedure? How many levels of SP nesting is possible? What is Log Shipping? Name 3 ways to get an Accurate Count of the Number of Records in a Table? What does it mean to have QUOTED_IDENTIFIER ON? What are the Implications of having it OFF? What is the Difference between a Local and a Global Temporary Table? What is the STUFF Function and How Does it Differ from the REPLACE Function? What is PRIMARY KEY? What is UNIQUE KEY Constraint? What is FOREIGN KEY? SQL SERVER – Interview Questions and Answers – Frequently Asked Questions – Day 9 of 31 What is CHECK Constraint? What is NOT NULL Constraint? What is the difference between UNION and UNION ALL? What is B-Tree? How to get @@ERROR and @@ROWCOUNT at the Same Time? What is a Scheduled Job or What is a Scheduled Task? What are the Advantages of Using Stored Procedures? What is a Table Called, if it has neither Cluster nor Non-cluster Index? What is it Used for? Can SQL Servers Linked to other Servers like Oracle? What is BCP? When is it Used? SQL SERVER – Interview Questions and Answers – Frequently Asked Questions – Day 10 of 31 What Command do we Use to Rename a db, a Table and a Column? What are sp_configure Commands and SET Commands? How to Implement One-to-One, One-to-Many and Many-to-Many Relationships while Designing Tables? What is Difference between Commit and Rollback when Used in Transactions? What is an Execution Plan? When would you Use it? How would you View the Execution Plan? SQL SERVER – Interview Questions and Answers – Frequently Asked Questions – Day 11 of 31 What is Difference between Table Aliases and Column Aliases? Do they Affect Performance? What is the difference between CHAR and VARCHAR Datatypes? What is the Difference between VARCHAR and VARCHAR(MAX) Datatypes? What is the Difference between VARCHAR and NVARCHAR datatypes? Which are the Important Points to Note when Multilanguage Data is Stored in a Table? How to Optimize Stored Procedure Optimization? What is SQL Injection? How to Protect Against SQL Injection Attack? How to Find Out the List Schema Name and Table Name for the Database? What is CHECKPOINT Process in the SQL Server? SQL SERVER – Interview Questions and Answers – Frequently Asked Questions – Day 12 of 31 How does Using a Separate Hard Drive for Several Database Objects Improves Performance Right Away? How to Find the List of Fixed Hard Drive and Free Space on Server? Why can there be only one Clustered Index and not more than one? What is Difference between Line Feed (\n) and Carriage Return (\r)? Is It Possible to have Clustered Index on Separate Drive From Original Table Location? What is a Hint? How to Delete Duplicate Rows? Why the Trigger Fires Multiple Times in Single Login? 2012 CTRL+SHIFT+] Shortcut to Select Code Between Two Parenthesis Shortcut key is CTRL+SHIFT+]. This key can be very useful when dealing with multiple subqueries, CTE or query with multiple parentheses. When exercised this shortcut key it selects T-SQL code between two parentheses. Monday Morning Puzzle – Query Returns Results Sometimes but Not Always I am beginner with SQL Server. I have one query, it sometime returns a result and sometime it does not return me the result. Where should I start looking for a solution and what kind of information I should send to you so you can help me with solving. I have no clue, please guide me. Remove Debug Button in SSMS – SQL in Sixty Seconds #020 – Video Effect of Case Sensitive Collation on Resultset Collation is a very interesting concept but I quite often see it is heavily neglected. I have seen developer and DBA looking for a workaround to fix collation error rather than understanding if the side effect of the workaround. Switch Between Two Parenthesis using Shortcut CTRL+] Earlier this week I wrote a blog post about CTRL+SHIFT+] Shortcut to Select Code Between Two Parenthesis, I received quite a lot of positive feedback from readers. If you are a regular reader of the blog post, you must be aware that I appreciate the learning shared by readers. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: Memory Lane, PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology

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• Working with Timelines with LINQ to Twitter

  - by Joe Mayo

  When first working with the Twitter API, I thought that using SinceID would be an effective way to page through timelines. In practice it doesn’t work well for various reasons. To explain why, Twitter published an excellent document that is a must-read for anyone working with timelines: Twitter Documentation: Working with Timelines This post shows how to implement the recommended strategies in that document by using LINQ to Twitter. You should read the document in it’s entirety before moving on because my explanation will start at the bottom and work back up to the top in relation to the Twitter document. What follows is an explanation of SinceID, MaxID, and how they come together to help you efficiently work with Twitter timelines. The Role of SinceID Specifying SinceID says to Twitter, “Don’t return tweets earlier than this”. What you want to do is store this value after every timeline query set so that it can be reused on the next set of queries.  The next section will explain what I mean by query set, but a quick explanation is that it’s a loop that gets all new tweets. The SinceID is a backstop to avoid retrieving tweets that you already have. Here’s some initialization code that includes a variable named sinceID that will be used to populate the SinceID property in subsequent queries: // last tweet processed on previous query set ulong sinceID = 210024053698867204; ulong maxID; const int Count = 10; var statusList = new List<status>(); Here, I’ve hard-coded the sinceID variable, but this is where you would initialize sinceID from whatever storage you choose (i.e. a database). The first time you ever run this code, you won’t have a value from a previous query set. Initially setting it to 0 might sound like a good idea, but what if you’re querying a timeline with lots of tweets? Because of the number of tweets and rate limits, your query set might take a very long time to run. A caveat might be that Twitter won’t return an entire timeline back to Tweet #0, but rather only go back a certain period of time, the limits of which are documented for individual Twitter timeline API resources. So, to initialize SinceID at too low of a number can result in a lot of initial tweets, yet there is a limit to how far you can go back. What you’re trying to accomplish in your application should guide you in how to initially set SinceID. I have more to say about SinceID later in this post. The other variables initialized above include the declaration for MaxID, Count, and statusList. The statusList variable is a holder for all the timeline tweets collected during this query set. You can set Count to any value you want as the largest number of tweets to retrieve, as defined by individual Twitter timeline API resources. To effectively page results, you’ll use the maxID variable to set the MaxID property in queries, which I’ll discuss next. Initializing MaxID On your first query of a query set, MaxID will be whatever the most recent tweet is that you get back. Further, you don’t know what MaxID is until after the initial query. The technique used in this post is to do an initial query and then use the results to figure out what the next MaxID will be.  Here’s the code for the initial query: var userStatusResponse = (from tweet in twitterCtx.Status where tweet.Type == StatusType.User && tweet.ScreenName == "JoeMayo" && tweet.SinceID == sinceID && tweet.Count == Count select tweet) .ToList(); statusList.AddRange(userStatusResponse); // first tweet processed on current query maxID = userStatusResponse.Min( status => ulong.Parse(status.StatusID)) - 1; The query above sets both SinceID and Count properties. As explained earlier, Count is the largest number of tweets to return, but the number can be less. A couple reasons why the number of tweets that are returned could be less than Count include the fact that the user, specified by ScreenName, might not have tweeted Count times yet or might not have tweeted at least Count times within the maximum number of tweets that can be returned by the Twitter timeline API resource. Another reason could be because there aren’t Count tweets between now and the tweet ID specified by sinceID. Setting SinceID constrains the results to only those tweets that occurred after the specified Tweet ID, assigned via the sinceID variable in the query above. The statusList is an accumulator of all tweets receive during this query set. To simplify the code, I left out some logic to check whether there were no tweets returned. If  the query above doesn’t return any tweets, you’ll receive an exception when trying to perform operations on an empty list. Yeah, I cheated again. Besides querying initial tweets, what’s important about this code is the final line that sets maxID. It retrieves the lowest numbered status ID in the results. Since the lowest numbered status ID is for a tweet we already have, the code decrements the result by one to keep from asking for that tweet again. Remember, SinceID is not inclusive, but MaxID is. The maxID variable is now set to the highest possible tweet ID that can be returned in the next query. The next section explains how to use MaxID to help get the remaining tweets in the query set. Retrieving Remaining Tweets Earlier in this post, I defined a term that I called a query set. Essentially, this is a group of requests to Twitter that you perform to get all new tweets. A single query might not be enough to get all new tweets, so you’ll have to start at the top of the list that Twitter returns and keep making requests until you have all new tweets. The previous section showed the first query of the query set. The code below is a loop that completes the query set: do { // now add sinceID and maxID userStatusResponse = (from tweet in twitterCtx.Status where tweet.Type == StatusType.User && tweet.ScreenName == "JoeMayo" && tweet.Count == Count && tweet.SinceID == sinceID && tweet.MaxID == maxID select tweet) .ToList(); if (userStatusResponse.Count > 0) { // first tweet processed on current query maxID = userStatusResponse.Min( status => ulong.Parse(status.StatusID)) - 1; statusList.AddRange(userStatusResponse); } } while (userStatusResponse.Count != 0 && statusList.Count < 30); Here we have another query, but this time it includes the MaxID property. The SinceID property prevents reading tweets that we’ve already read and Count specifies the largest number of tweets to return. Earlier, I mentioned how it was important to check how many tweets were returned because failing to do so will result in an exception when subsequent code runs on an empty list. The code above protects against this problem by only working with the results if Twitter actually returns tweets. Reasons why there wouldn’t be results include: if the first query got all the new tweets there wouldn’t be more to get and there might not have been any new tweets between the SinceID and MaxID settings of the most recent query. The code for loading the returned tweets into statusList and getting the maxID are the same as previously explained. The important point here is that MaxID is being reset, not SinceID. As explained in the Twitter documentation, paging occurs from the newest tweets to oldest, so setting MaxID lets us move from the most recent tweets down to the oldest as specified by SinceID. The two loop conditions cause the loop to continue as long as tweets are being read or a max number of tweets have been read.  Logically, you want to stop reading when you’ve read all the tweets and that’s indicated by the fact that the most recent query did not return results. I put the check to stop after 30 tweets are reached to keep the demo from running too long – in the console the response scrolls past available buffer and I wanted you to be able to see the complete output. Yet, there’s another point to be made about constraining the number of items you return at one time. The Twitter API has rate limits and making too many queries per minute will result in an error from twitter that LINQ to Twitter raises as an exception. To use the API properly, you’ll have to ensure you don’t exceed this threshold. Looking at the statusList.Count as done above is rather primitive, but you can implement your own logic to properly manage your rate limit. Yeah, I cheated again. Summary Now you know how to use LINQ to Twitter to work with Twitter timelines. After reading this post, you have a better idea of the role of SinceID - the oldest tweet already received. You also know that MaxID is the largest tweet ID to retrieve in a query. Together, these settings allow you to page through results via one or more queries. You also understand what factors affect the number of tweets returned and considerations for potential error handling logic. The full example of the code for this post is included in the downloadable source code for LINQ to Twitter.   @JoeMayo

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• Push Trunk or Push Branch to Production

  - by coffeeaddict

  I'd like to get an idea of some processes on build process with Tortoise SVN. Primarily I'm wondering do you push: The Mainline Trunk A branch after QA has grabbed it into a working copy locally and tested the branch and then some build pushes that branch The problem I have is I work at a craphole (hey, it is what it is and I'm venting on stackoverflow, you better believe it..good way to relieve stress due to complete utter chaos) and we have no formal process for pushing anything. In fact even worse my boss directly codes against production. When I have changes, he pushes the mainline trunk. The problem becomes when I make database changes on our Dev database for lets say Branch A. Well...that breaks Branch B and C. I have like 4 projects going on at once! Why? Well, I will not get into that (chaos). So consequently I rename a table field, or add a field or whatever in SQL Server and walla, now my other branches have stale code pointing to previous field names. So what happens? I have to merge certain changes to this branch, to that branch, etc. It feels like a war zone. Finally, what happens is I try to only merge the minimum. Lets say I made DB changes for Branch A's code but now I had to jump back on Branch B's project. Well I need to merge "some" of A's changes over for those database changes so that B's code is not going to bomb out and is able to work with the new table changes. Finally boss pushes the mainline trunk to production. Now I get an email "you forgot to remove the hyperlink for this". That hyperlink was actually a feature I added in Branch A. But what he's talking about here is he just pushed the mainline trunk to production which now has my merged changes from Branch B and any database scripts for Branch A because remember I had some DB changes and if he pushes code, it's got to reflect those changes thus some partial database changes must also be pushed even if it's not related to this project. Well...I missed the hyperlink, so kill me. Maybe that's why we need a build process boss? (sorry, it's been a nightmare working here which is why this thread is getting so detailed). Anyway, obviously this is a nightmare. And he dictates almost everything. The only reason we have source control is because I've worked on hard core teams and that's the first thing you setup. Well there was none here. Problem is I can't dictate the structure..he does but he's never really used source control!! My God. So we have no QA. This is an e-commerce website. That's another huge issue. So consequently I'm expected to be perfect. That means mainline trunk needs to be perfect for whatever we're pushing, whatever branch feature. Is this luda? wtf do I do? I could go off on him after tying so many times tactfully to explain that we need a freakin build process (not just copy local mainline trunk to production!) but I've tried to push before and got yelled at. So I gave up on that. So it will help me tremendously to know how others are pushing their source from Tortoise to production. I was not the person pushing when I was on previous teams so really I'm not too versed in build processes. We are a fairly good size e-commerce site and get a couple millions hits a month.

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• Stored proc running 30% slower through Java versus running directly on database

  - by James B

  Hi All, I'm using Java 1.6, JTDS 1.2.2 (also just tried 1.2.4 to no avail) and SQL Server 2005 to create a CallableStatement to run a stored procedure (with no parameters). I am seeing the Java wrapper running the same stored procedure 30% slower than using SQL Server Management Studio. I've run the MS SQL profiler and there is little difference in I/O between the two processes, so I don't think it's related to query plan caching. The stored proc takes no arguments and returns no data. It uses a server-side cursor to calculate the values that are needed to populate a table. I can't see how the calling a stored proc from Java should add a 30% overhead, surely it's just a pipe to the database that SQL is sent down and then the database executes it....Could the database be giving the Java app a different query plan?? I've posted to both the MSDN forums, and the sourceforge JTDS forums (topic: "stored proc slower in JTDS than direct in DB") I was wondering if anyone has any suggestions as to why this might be happening? Thanks in advance, -James (N.B. Fear not, I will collate any answers I get in other forums together here once I find the solution) Java code snippet: sLogger.info("Preparing call..."); stmt = mCon.prepareCall("SP_WB200_POPULATE_TABLE_limited_rows"); sLogger.info("Call prepared. Executing procedure..."); stmt.executeQuery(); sLogger.info("Procedure complete."); I have run sql profiler, and found the following: Java app : CPU: 466,514 Reads: 142,478,387 Writes: 284,078 Duration: 983,796 SSMS : CPU: 466,973 Reads: 142,440,401 Writes: 280,244 Duration: 769,851 (Both with DBCC DROPCLEANBUFFERS run prior to profiling, and both produce the correct number of rows) So my conclusion is that they both execute the same reads and writes, it's just that the way they are doing it is different, what do you guys think? It turns out that the query plans are significantly different for the different clients (the Java client is updating an index during an insert that isn't in the faster SQL client, also, the way it is executing joins is different (nested loops Vs. gather streams, nested loops Vs index scans, argh!)). Quite why this is, I don't know yet (I'll re-post when I do get to the bottom of it) Epilogue I couldn't get this to work properly. I tried homogenising the connection properties (arithabort, ansi_nulls etc) between the Java and Mgmt studio clients. It ended up the two different clients had very similar query/execution plans (but still with different actual plan_ids). I posted a summary of what I found to the MSDN SQL Server forums as I found differing performance not just between a JDBC client and management studio, but also between Microsoft's own command line client, SQLCMD, I also checked some more radical things like network traffic too, or wrapping the stored proc inside another stored proc, just for grins. I have a feeling the problem lies somewhere in the way the cursor was being executed, and it was somehow giving rise to the Java process being suspended, but why a different client should give rise to this different locking/waiting behaviour when nothing else is running and the same execution plan is in operation is a little beyond my skills (I'm no DBA!). As a result, I have decided that 4 days is enough of anyone's time to waste on something like this, so I will grudgingly code around it (if I'm honest, the stored procedure needed re-coding to be more incremental instead of re-calculating all data each week anyway), and chalk this one down to experience. I'll leave the question open, big thanks to everyone who put their hat in the ring, it was all useful, and if anyone comes up with anything further, I'd love to hear some more options...and if anyone finds this post as a result of seeing this behaviour in their own environments, then hopefully there's some pointers here that you can try yourself, and hope fully see further than we did. I'm ready for my weekend now! -James

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• ASP.NET: Button in user control not posting back

  - by Ronnie Overby

  I have a simple user control with this code: <%@ Control Language="C#" AutoEventWireup="true" CodeFile="Pager.ascx.cs" Inherits="Pager" %> <table style="width: 100%;"> <tr> <td runat="server" id="PageControls"> <!-- This button has the problem: --> <asp:Button ID="btnPrevPage" runat="server" Text="&larr;" OnClick="btnPrevPage_Click" /> Page <asp:DropDownList runat="server" ID="ddlPage" AutoPostBack="true" OnSelectedIndexChanged="ddlPage_SelectedIndexChanged" /> of <asp:Label ID="lblTotalPages" runat="server" /> <!-- This button has the problem: --> <asp:Button ID="btnNextPage" runat="server" Text="&rarr;" OnClick="btnNextPage_Click" /> </td> <td align="right" runat="server" id="itemsPerPageControls"> <asp:Literal ID="perPageText1" runat="server" /> <asp:DropDownList ID="ddlItemsPerPage" runat="server" AutoPostBack="true" OnSelectedIndexChanged="ddlItemsPerPage_SelectedIndexChanged" /> <asp:Literal ID="perPageText2" runat="server" /> </td> </tr> </table> As you can see, the 2 buttons are wired to click events, which are defined correctly in the code-behind. Now, here is how I include an instance of the control on my page: <uc:Pager ID="Pager1" runat="server" TotalRecords="100" DisplayItemsPerPage="true" ItemsPerPageChoices="10,25,50,100" ItemsPerPageFormatString="Sessions/Page: {0}" PageSize="25" OnPageChanged="PageChanged" OnPageSizeChanged="PageChanged" /> I noticed though, that the 2 buttons in my user control weren't causing a post back when clicked. The drop down list does cause postback, though. Here is the rendered HTML: <table style="width: 100%;"> <tr> <td id="ctl00_MainContent_Pager1_PageControls" align="left"> <!-- No onclick event! Why? --> <input type="submit" name="ctl00$MainContent$Pager1$btnPrevPage" value="?" id="ctl00_MainContent_Pager1_btnPrevPage" /> Page <select name="ctl00$MainContent$Pager1$ddlPage" onchange="javascript:setTimeout('__doPostBack(\'ctl00$MainContent$Pager1$ddlPage\',\'\')', 0)" id="ctl00_MainContent_Pager1_ddlPage"> <option value="1">1</option> <option selected="selected" value="2">2</option> <option value="3">3</option> <option value="4">4</option> <option value="5">5</option> <option value="6">6</option> </select> of <span id="ctl00_MainContent_Pager1_lblTotalPages">6</span> <!-- No onclick event! Why? --> <input type="submit" name="ctl00$MainContent$Pager1$btnNextPage" value="?" id="ctl00_MainContent_Pager1_btnNextPage" /> </td> <td id="ctl00_MainContent_Pager1_itemsPerPageControls" align="right"> Sessions/Page: <select name="ctl00$MainContent$Pager1$ddlItemsPerPage" onchange="javascript:setTimeout('__doPostBack(\'ctl00$MainContent$Pager1$ddlItemsPerPage\',\'\')', 0)" id="ctl00_MainContent_Pager1_ddlItemsPerPage"> <option value="10">10</option> <option selected="selected" value="25">25</option> <option value="50">50</option> <option value="100">100</option> </select> </td> </tr> </table> And, as you can see, there is no onclick attribute being rendered in the button's input elements. Why not?

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• Running 32 bit assembly code on a 64 bit Linux & 64 bit Processor : Explain the anomaly.

  - by claws

  Hello, I'm in an interesting problem.I forgot I'm using 64bit machine & OS and wrote a 32 bit assembly code. I don't know how to write 64 bit code. This is the x86 32-bit assembly code for Gnu Assembler (AT&T syntax) on Linux. //hello.S #include <asm/unistd.h> #include <syscall.h> #define STDOUT 1 .data hellostr: .ascii "hello wolrd\n"; helloend: .text .globl _start _start: movl $(SYS_write) , %eax //ssize_t write(int fd, const void *buf, size_t count); movl $(STDOUT) , %ebx movl $hellostr , %ecx movl $(helloend-hellostr) , %edx int $0x80 movl $(SYS_exit), %eax //void _exit(int status); xorl %ebx, %ebx int $0x80 ret Now, This code should run fine on a 32bit processor & 32 bit OS right? As we know 64 bit processors are backward compatible with 32 bit processors. So, that also wouldn't be a problem. The problem arises because of differences in system calls & call mechanism in 64-bit OS & 32-bit OS. I don't know why but they changed the system call numbers between 32-bit linux & 64-bit linux. asm/unistd_32.h defines: #define __NR_write 4 #define __NR_exit 1 asm/unistd_64.h defines: #define __NR_write 1 #define __NR_exit 60 Anyway using Macros instead of direct numbers is paid off. Its ensuring correct system call numbers. when I assemble & link & run the program. $cpp hello.S hello.s //pre-processor $as hello.s -o hello.o //assemble $ld hello.o // linker : converting relocatable to executable Its not printing helloworld. In gdb its showing: Program exited with code 01. I don't know how to debug in gdb. using tutorial I tried to debug it and execute instruction by instruction checking registers at each step. its always showing me "program exited with 01". It would be great if some on could show me how to debug this. (gdb) break _start Note: breakpoint -10 also set at pc 0x4000b0. Breakpoint 8 at 0x4000b0 (gdb) start Function "main" not defined. Make breakpoint pending on future shared library load? (y or [n]) y Temporary breakpoint 9 (main) pending. Starting program: /home/claws/helloworld Program exited with code 01. (gdb) info breakpoints Num Type Disp Enb Address What 8 breakpoint keep y 0x00000000004000b0 <_start> 9 breakpoint del y <PENDING> main I tried running strace. This is its output: execve("./helloworld", ["./helloworld"], [/* 39 vars */]) = 0 write(0, NULL, 12 <unfinished ... exit status 1> Explain the parameters of write(0, NULL, 12) system call in the output of strace? What exactly is happening? I want to know the reason why exactly its exiting with exitstatus=1? Can some one please show me how to debug this program using gdb? Why did they change the system call numbers? Kindly change this program appropriately so that it can run correctly on this machine. EDIT: After reading Paul R's answer. I checked my files claws@claws-desktop:~$ file ./hello.o ./hello.o: ELF 64-bit LSB relocatable, x86-64, version 1 (SYSV), not stripped claws@claws-desktop:~$ file ./hello ./hello: ELF 64-bit LSB executable, x86-64, version 1 (SYSV), statically linked, not stripped All of my questions still hold true. What exactly is happening in this case? Can someone please answer my questions and provide an x86-64 version of this code?

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• Running 32 bit assembly code on a 64 bit Linux & 64 bit Processor : Expalin the anomaly.

  - by claws

  Hello, I'm in an interesting problem.I forgot I'm using 64bit machine & OS and wrote a 32 bit assembly code. I don't know how to write 64 bit code. This is the x86 32-bit assembly code for Gnu Assembler (AT&T syntax) on Linux. #include <asm/unistd.h> #include <syscall.h> #define STDOUT 1 .data hellostr: .ascii "hello wolrd\n"; helloend: .text .globl _start _start: movl $(SYS_write) , %eax //ssize_t write(int fd, const void *buf, size_t count); movl $(STDOUT) , %ebx movl $hellostr , %ecx movl $(helloend-hellostr) , %edx int $0x80 movl $(SYS_exit), %eax //void _exit(int status); xorl %ebx, %ebx int $0x80 ret Now, This code should run fine on a 32bit processor & 32 bit OS right? As we know 64 bit processors are backward compatible with 32 bit processors. So, that also wouldn't be a problem. The problem arises because of differences in system calls & call mechanism in 64-bit OS & 32-bit OS. I don't know why but they changed the system call numbers between 32-bit linux & 64-bit linux. asm/unistd_32.h defines: #define __NR_write 4 #define __NR_exit 1 asm/unistd_64.h defines: #define __NR_write 1 #define __NR_exit 60 Anyway using Macros instead of direct numbers is paid off. Its ensuring correct system call numbers. when I assemble & link & run the program. Its not printing helloworld. In gdb its showing: Program exited with code 01. I don't know how to debug in gdb. using tutorial I tried to debug it and execute instruction by instruction checking registers at each step. its always showing me "program exited with 01". It would be great if some on could show me how to debug this. (gdb) break _start Note: breakpoint -10 also set at pc 0x4000b0. Breakpoint 8 at 0x4000b0 (gdb) start Function "main" not defined. Make breakpoint pending on future shared library load? (y or [n]) y Temporary breakpoint 9 (main) pending. Starting program: /home/claws/helloworld Program exited with code 01. (gdb) info breakpoints Num Type Disp Enb Address What 8 breakpoint keep y 0x00000000004000b0 <_start> 9 breakpoint del y <PENDING> main I tried running strace. This is its output: execve("./helloworld", ["./helloworld"], [/* 39 vars */]) = 0 write(0, NULL, 12 <unfinished ... exit status 1> Explain the parameters of write(0, NULL, 12) system call in the output of strace? What exactly is happening? I want to know the reason why exactly its exiting with exitstatus=1? Can some one please show me how to debug this program using gdb? Why did they change the system call numbers? Change this program appropriately so that it can run correctly on this machine.

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• iPhone dev - viewDidUnload subviews

  - by Mk12

  I'm having a hard time undestand a couple of the methods in UIViewController, but first I'll say what I think they are meant for (ignoring interface builder because I'm not using it): -init: initialize non view-related stuff that won't need to be released in low memory situations (i.e. not objects or objects that can't be recreated easily). -loadView: create the view set the [self view] property. -viewDidLoad: Create all the other view elements -viewDidUnload: Release objects created in -viewDidLoad. didReceiveMemoryWarning: Low-memory situation, release unnecessary things such as cached data, if this view doesn't have a superview then the [super didReceiveMemoryWarning] will go on to release (unload) the view and call -viewDidUnload. -dealloc: release everything -viewWillAppear:, -viewDidAppear:, -viewWillDisappear:, -viewDidDisappear: self-explanatory, not necessary unless you want to respond (do something) to those events. I'm not sure about a couple of things. First, the Apple docs say that when -viewDidUnload is called, the view has already been released and set to nil. Will -loadView get called again to recreate the view later on? There's a few things I created in -viewDidLoad that I didn't make a ivar/property for because there is no need and it will be retained by the view (because they are subviews of it). So when the view is released, it will release those too, right? When the view is released, will it release all its subviews? Because all the objects I created in -viewDidLoad are subviews of [self view]. So if they already get released why release them again in -viewDidUnload? I can understand data that is necessary when the view is visible being loaded and unloaded in these methods, but like I asked, why release the subviews if they already get released? EDIT: After reading other questions, I think I might have got it (my 2nd question). In the situation where I just use a local variable, alloc it, make it a subview and release, it will have a retain count of 1 (from adding it as a subview), so when the view is released it is too. Now for the view elements with ivars pointing to them, I wasn't using properties because no outside class would need to access them. But now I think that that's wrong, because in this situation: // MyViewController.h @interface MyViewController : UIViewController { UILabel *myLabel; } // MyViewController.m . . . - (void)viewDidLoad { myLabel = [[UILabel alloc] initWithFrame:CGRectMake(0, 0, 40, 10)]; [myLabel setText:@"Foobar"]; [[self view] addSubview:myLabel]; } - (void)viewDidUnload [ // equivalent of [self setMyLabel:nil]; without properties [myLabel release]; myLabel = nil; } In that situation, the label will be sent the -release message after it was deallocated because the ivar didn't retain it (because it wasn't a property). But with a property the retain count would be two: the view retaining it and the property. So then in -viewDidUnload it will get deallocated. So its best to just always use properties for these things, am I right? Or not? EDIT: I read somewhere that -viewDidLoad and -viewDidUnload are only for use with Interface Builder, that if you are doing everything programmatically you shouldn't use them. Is that right? Why?

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• Chatbot client and class modification

  - by blake

  ChatBot Class Modification: Modify the reply() method of the ChatBot class to recognize additional words and phrases. Part 1: Everyone must complete this section. When the userInput parameter value is: The reply method should return: how do I quit enter quit how do I exit enter quit how do I stop enter quit how do I ____ do you really want to do that how are you I'm fine how ______ I don't know Add two additional words or phrases to recognize and respond to. ChatBot Client Modification: Modify the ChatBot client application to loop until the end-user enters "quit". Here is my service class / ** * Java Chatbot Service class * @author Blake * 3/5/2012 */ /** * Default constructor. */ public class Chatbot { private String name; /** Users name */ private String introbot; /** Name of the Chatbot */ private String reply; /** Replies to the input of the string name and string introbot */ /** * Constructs mutebot object * @param mutebow - returns name of mutebot */ public Chatbot() { name = "MuteBot"; } /** * Changes Name * @param name - new name */ public void setName (String n) { name = n; } /** * Accesses name * @return a brand new name */ public String getName() { return name; } /** * Accesses introbot * @return name of mutebot */ public String introbot() { String intro = "Hello! My name is " + name; return intro; } /** * Accesses replay(String newuserinput) * @return introbot reply to user input */ public String getreply(String newuserinput) { String reply = "I'm just learning to talk"; if (newuserinput.equalsIgnoreCase("What")) reply = "Why do you ask?"; else if (newuserinput.equalsIgnoreCase("Why") ) reply = "Why Not"; else if (newuserinput.equalsIgnoreCase("How")) reply = "I don't know!"; else if (newuserinput.equalsIgnoreCase("Where") ) reply = "Anne Arundel Community College"; else if (newuserinput.equalsIgnoreCase("When")) reply = "Tomorrow"; else if (newuserinput.equalsIgnoreCase("how do I quit")) reply = "enter quit"; else if (newuserinput.equalsIgnoreCase("how do I exit")) reply = "enter quit"; else if (newuserinput.equalsIgnoreCase("how do I stop")) reply = "enter quit"; else if (newuserinput.equalsIgnoreCase("how are you")) reply = "I'm fine"; else if (newuserinput.equalsIgnoreCase("how do you do")) reply = "I am doing well"; else if (newuserinput.equalsIgnoreCase("how do I get out")) reply = "By going through the door"; else if (newuserinput.indexOf("how do I" ) ==0) { String substring = newuserinput.substring(8); reply = "do you really want to do that" + substring; } else if (newuserinput.indexOf("how" ) ==0) { String substring = newuserinput.substring(10); reply = "I don't know" + substring ; } return reply; } } Here is my client/application class /** * Java Chatbot Client class * @author Blake * 3/5/2012 */ import java.util.Scanner; public class ChatbotClient { public static void main(String[] args) { Scanner input = new Scanner(System.in); Chatbot t = new Chatbot(); System.out.print("What is your name? "); String name = input.nextLine(); System.out.println(t.introbot()); System.out.print(name + "> "); String reply = input.nextLine(); System.out.println(t.getName() + "> " + t.getreply(reply)); //while (reply < quit) /*{ quit++ i = i + 1 }*/ } } I don't know what I am doing wrong with this part right here Modify the ChatBot client application to loop until the end-user enters "quit". I am trying to create a while loop which will continue until user says quit.

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• Link Error : xxx is already defined in *****.LIB :: What exactly is wrong?

  - by claws

  Problem: I'm trying to use a library named DCMTK which used some other external libraries ( zlib, libtiff, libpng, libxml2, libiconv ). I've downloaded these external libraries (*.LIB & *.h files ) from the same website. Now, when I compile the DCMTK library I'm getting link errors (793 errors) like this: Error 2 error LNK2005: __encode_pointer already defined in MSVCRTD.lib(MSVCR90D.dll) LIBCMTD.lib dcmmkdir Error 3 error LNK2005: __decode_pointer already defined in MSVCRTD.lib(MSVCR90D.dll) LIBCMTD.lib dcmmkdir Error 4 error LNK2005: __CrtSetCheckCount already defined in MSVCRTD.lib(MSVCR90D.dll) LIBCMTD.lib dcmmkdir Error 5 error LNK2005: __invoke_watson already defined in MSVCRTD.lib(MSVCR90D.dll) LIBCMTD.lib dcmmkdir Error 6 error LNK2005: __errno already defined in MSVCRTD.lib(MSVCR90D.dll) LIBCMTD.lib dcmmkdir Error 7 error LNK2005: __configthreadlocale already defined in MSVCRTD.lib(MSVCR90D.dll) LIBCMTD.lib dcmmkdir Error 8 error LNK2005: _exit already defined in MSVCRTD.lib(MSVCR90D.dll) LIBCMTD.lib dcmmkdir Documentation: This seems to be a popular error for this library so, they do have a FAQ entry addressing this issue which ( http://forum.dcmtk.org/viewtopic.php?t=35 ) says: The problem is that the linker tries to combine different, incompatible versions of the Visual C++ runtime library into a single binary. This happens when not all parts of your project and the libraries you link against are generated with the same code generation options in Visual C++. Do not use the /NODEFAULTLIB workaround, because strange software crashes may follow. Fix the problem! DCMTK is by default compiled with the "Multithreaded" or "Multithreaded Debug" code generation option (the latter for Debug mode). Either change the project settings of all of your code to use these code generation options, or change the code generation for all DCMTK modules and re-compile. MFC users beware: DCMTK should be compiled with "Multithreaded DLL" or "Multithreaded DLL Debug" settings if you want to link the libraries into an MFC application. Solution to same problem for others: http://stackoverflow.com/questions/2259697/vscopengl-huge-amount-of-linker-issues-with-release-build-only says: It seems that your release build is trying to link to something that was built debug. You probably have a broken dependency in your build, (or you missed rebuilding something to release by hand if your project is normally built in pieces). More technically, you seem to be linking projects built with different C Run Time library settings, one with "Multi-Threaded", another one with "Multi-Threaded Debug". Adjust the settings for all the projects to use the very same flavour of the library and the issue should go away Questions: Till now I used to think that Name mangling is the only problem that may cause linking failures if its not been standardized. Just now I knew there are other things also which can cause same effect. Whats up with the "Debug Mode" (Multi-Threaded Debug) and "Release Mode" (Multi-Threaded)? What exactly is happening under the hood? Why exactly this thing is causing linking error? I wonder if there is something called "Single-Threaded Debug" and "Single-Threaded" which again causes the same thing. Documentation talks something about "Code Generation Options". What Code Generation Options? WTH are they? Documentation specifically warns us not to use /NODEFAULTLIB workaround. (example /NODEFAULTLIB :msvcrt ). Why? How would I cause troubles? what exactly is it? Please explain the last point in the documentation for MFC users. Because I'm going to use MFC later in this project. Explain Why should we do it? What troubles would it cause if I don't. Anything more you'd like to mention? I mean regarding similar errors. I'm very interested in Linker & its problems. So, if there are any similar things you can mentions them or some keywords atleast.

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• Checkboxes will not check in IE7 using Javascript, and yet no errors

  - by leeand00

  Okay I'm totally confused on this one. I have a script that receives a bunch of values from a JSON object and creates a bunch of checkboxes and either checks or unchecks a these checkboxes based on their values. This script treats me like a woman treats me... "If you don't know what's wrong, then I'm not going to tell you..." The script works correctly in IE8, Firefox3, etc... etc... However... In IE7 the script fails to check off the checkboxes. It displays no errors and from what I can tell, the script runs just fine. I just doesn't check any of the checkboxes, and I don't know why... shoppingCart['Update_Stock_Item_0_NRD%5FHAT2'] = { 'propeller': { 'label' : 'propeller', 'optionValues' : { 'on' : { 'selected': 'selected' }, 'off' : { 'selected': '' }, '' : new String() } }, 'sunLogo': { 'label' : 'sunLogo', 'optionValues' : { 'on' : { 'selected': 'selected' }, 'off' : { 'selected': '' }, '' : new String() } }, 'MSLogo': { 'label' : 'sunLogo', 'optionValues' : { 'on' : { 'selected': 'selected' }, 'off' : { 'selected': '' }, '' : new String() } } }; function stockInit() { alert("BEGIN: stockInit()"); // TODO: You will recieve an "on" and an "off" option, // One will have a "selected" attribute of "selected", // and the other will have a "selected" attribute of "" // // The option that has the "selected" attribute of "" // will generate a checkbox that is not checked. // // The option that has the "selected attribute of "selected" // will generate a checkbox that is checked. // // Why? You ask...because that's just the way the thing is // setup. for(var item in shoppingCart) { // // console.log("processing item: " + item); var optionContainer = document.getElementById(item + "_optionContainer"); for(var option in shoppingCart[item]) { if(option != "blank") { // // console.log("option: " + option); var currentOption = shoppingCart[item][option]['optionValues']; // // console.log("currentOption['on']['selected']: " + currentOption['on']['selected']); // // console.log("currentOption['off']['selected']: " + currentOption['off']['selected']); // Really you only have to check the one, but just to be through-o var selected = (currentOption['on']['selected'] == 'selected') ? true : false; selected = (currentOption['off']['selected'] == 'selected') ? false : true; var label = document.createElement("LABEL"); var labelText = document.createTextNode(shoppingCart[item][option]['label']); var optionInput = document.createElement("INPUT"); var hiddenInput = document.createElement("INPUT"); optionInput.setAttribute("type", "checkbox"); optionInput.checked = selected; optionInput.setAttribute("id", option); alert(optionInput.id); alert(optionInput.checked); hiddenInput.setAttribute("type", "hidden"); hiddenInput.setAttribute("name", option); hiddenInput.setAttribute("id", option + "_hiddenValue"); hiddenInput.setAttribute("value", (optionInput.checked) ? "on" : "off"); label.appendChild(optionInput); label.appendChild(labelText); label.appendChild(hiddenInput); (function(id) { optionInput.onclick = function() { var hiddenInput = document.getElementById(id + "_hiddenValue"); hiddenInput.setAttribute("value", (this.checked == true) ? "on" : "off"); alert("this.id: " + this.id); alert("this.checked: " + this.checked); } })(optionInput.id); optionContainer.appendChild(label); } } // // console.log("processing item of " + item + " complete"); } alert("END: stockInit()"); } And please don't ask why I'm doing things this way...all I can really tell you is that I don't have access to the backend code...so I get what I get...

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• "Attach or Add an entity that is not new...loaded from another DataContext. This is not supported."

  - by sah302

  Similar error as other questions, but not quite the same, I am not trying to attach anything. What I am trying to do is insert a new row into a linking table, specifically UserAccomplishment. Relations are set in LINQ to User and Accomplishment Tables. I have a generic insert function: Public Function insertRow(ByVal entity As ImplementationType) As Boolean If entity IsNot Nothing Then Dim lcfdatacontext As New LCFDataContext() Try lcfdatacontext.GetTable(Of ImplementationType)().InsertOnSubmit(entity) lcfdatacontext.SubmitChanges() lcfdatacontext.Dispose() Return True Catch ex As Exception Return False End Try Else Return False End If End Function If you try and give UserAccomplishment the two appropriate objects this will naturally crap out if either the User or Accomplishment already exist. It only works when both user and accomplishment don't exist. I expected this behavior. What does work is simply giving the userAccomplishment object a user.id and accomplishment.id and populating the rest of the fields. This works but is kind of awkward to use in my app, it would be much easier to simply pass in both objects and have it work out what already exists and what doesn't. Okay so I made the following (please ignore the fact that this is horribly inefficient because I know it is): Public Class UserAccomplishmentDao Inherits EntityDao(Of UserAccomplishment) Public Function insertLinkerObjectRow(ByVal userAccomplishment As UserAccomplishment) Dim insertSuccess As Boolean = False If Not userAccomplishment Is Nothing Then Dim userDao As New UserDao() Dim accomplishmentDao As New AccomplishmentDao() Dim user As New User() Dim accomplishment As New Accomplishment() 'see if either object already exists in db' user = userDao.getOneByValueOfProperty("Id", userAccomplishment.User.Id) accomplishment = accomplishmentDao.getOneByValueOfProperty("Id", userAccomplishment.Accomplishment.Id) If user Is Nothing And accomplishment Is Nothing Then 'neither the user or the accomplishment exist, both are new so insert them both, typical insert' insertSuccess = Me.insertRow(userAccomplishment) ElseIf user Is Nothing And Not accomplishment Is Nothing Then 'user is new, accomplishment is not new, so just insert the user, and the relation in userAccomplishment' Dim userWithExistingAccomplishment As New UserAccomplishment(userAccomplishment.User, userAccomplishment.Accomplishment.Id, userAccomplishment.LastUpdatedBy) insertSuccess = Me.insertRow(userWithExistingAccomplishment) ElseIf Not user Is Nothing And accomplishment Is Nothing Then 'user is not new, accomplishment is new, so just insert the accomplishment, and the relation in userAccomplishment' Dim existingUserWithAccomplishment As New UserAccomplishment(userAccomplishment.UserId, userAccomplishment.Accomplishment, userAccomplishment.LastUpdatedBy) insertSuccess = Me.insertRow(existingUserWithAccomplishment) Else 'both are not new, just add the relation' Dim userAccomplishmentBothExist As New UserAccomplishment(userAccomplishment.User.Id, userAccomplishment.Accomplishment.Id, userAccomplishment.LastUpdatedBy) insertSuccess = Me.insertRow(userAccomplishmentBothExist) End If End If Return insertSuccess End Function End Class Alright, here I basically check if the supplied user and accomplishment already exists in the db, and if so call an appropriate constructor that will leave whatever already exists empty, but supply the rest of the information so the insert can succeed. However, upon trying an insert: Dim result As Boolean = Me.userAccomplishmentDao.insertLinkerObjectRow(userAccomplishment) In which the user already exists, but the accomplishment does not (the 99% typical scenario) I get the error: "An attempt has been made to Attach or Add an entity that is not new, perhaps having been loaded from another DataContext. This is not supported." I have debugged this multiple times now and am not sure why this is occuring, if either User or Accomplishment exist, I am not including it in the final object to try to insert. So nothing appears to be attempted to be added. Even in debug, upon insert, the object was set to empty. So the accomplishment is new and the user is empty. 1) Why is it still saying that and how can I fix it ..using my current structure 2) Pre-emptive 'use repository pattern answers' - I know this way kind of sucks in general and I should be using the repository pattern. However, I can't use that in the current project because I don't have time to refactor that due to my non existence knowledge of it and time constraints. The usage of the app is going to so small that the inefficient use of datacontext's and what have you won't matter so much. I can refactor it once it's up and running, but for now I just need to 'push through' with my current structure. Edit: I also just tested this when having both already exists, and only insert each object's IDs into the table, that works. So I guess I could manually insert whichever object doesn't exist as a single insert, then put the ids only into the linking table, but I still don't know why when one object exists, and I make it empty, it doens't work.

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• javax.naming.NameNotFoundException: Name [comp/env] is not bound in this Context. Unable to find [comp] error with java scheduler

  - by Morgan Azhari

  What I'm trying to do is to update my database after a period of time. So I'm using java scheduler and connection pooling. I don't know why but my code only working once. It will print: init success success javax.naming.NameNotFoundException: Name [comp/env] is not bound in this Context. Unable to find [comp]. at org.apache.naming.NamingContext.lookup(NamingContext.java:820) at org.apache.naming.NamingContext.lookup(NamingContext.java:168) at org.apache.naming.SelectorContext.lookup(SelectorContext.java:158) at javax.naming.InitialContext.lookup(InitialContext.java:411) at test.Pool.main(Pool.java:25) ---> line 25 is Context envContext = (Context)initialContext.lookup("java:/comp/env"); I don't know why it only works once. I already test it if I didn't running it without java scheduler and it works fine. No error whatsoerver. Don't know why i get this error if I running it using scheduler. Hope someone can help me. My connection pooling code: public class Pool { public DataSource main() { try { InitialContext initialContext = new InitialContext(); Context envContext = (Context)initialContext.lookup("java:/comp/env"); DataSource datasource = new DataSource(); datasource = (DataSource)envContext.lookup("jdbc/test"); return datasource; } catch (Exception ex) { ex.printStackTrace(); } return null; } } my web.xml: <web-app version="3.0" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd"> <listener> <listener-class> package.test.Pool</listener-class> </listener> <resource-ref> <description>DB Connection Pooling</description> <res-ref-name>jdbc/test</res-ref-name> <res-type>javax.sql.DataSource</res-type> <res-auth>Container</res-auth> </resource-ref> Context.xml: <?xml version="1.0" encoding="UTF-8"?> <Context path="/project" reloadable="true"> <Resource auth="Container" defaultReadOnly="false" driverClassName="com.mysql.jdbc.Driver" factory="org.apache.tomcat.jdbc.pool.DataSourceFactory" initialSize="0" jdbcInterceptors="org.apache.tomcat.jdbc.pool.interceptor.ConnectionState;org.apache.tomcat.jdbc.pool.interceptor.StatementFinalizer" jmxEnabled="true" logAbandoned="true" maxActive="300" maxIdle="50" maxWait="10000" minEvictableIdleTimeMillis="300000" minIdle="30" name="jdbc/test" password="test" removeAbandoned="true" removeAbandonedTimeout="60" testOnBorrow="true" testOnReturn="false" testWhileIdle="true" timeBetweenEvictionRunsMillis="30000" type="javax.sql.DataSource" url="jdbc:mysql://localhost:3306/database?noAccessToProcedureBodies=true" username="root" validationInterval="30000" validationQuery="SELECT 1"/> </Context> my java scheduler public class Scheduler extends HttpServlet{ public void init() throws ServletException { System.out.println("init success"); try{ Scheduling_test test = new Scheduling_test(); ScheduledExecutorService executor = Executors.newScheduledThreadPool(100); ScheduledFuture future = executor.scheduleWithFixedDelay(test, 1, 60 ,TimeUnit.SECONDS); }catch(Exception e){ e.printStackTrace(); } } } Schedule_test public class Scheduling_test extends Thread implements Runnable{ public void run(){ Updating updating = new Updating(); updating.run(); } } updating public class Updating{ public void run(){ ResultSet rs = null; PreparedStatement p = null; StringBuilder sb = new StringBuilder(); Pool pool = new Pool(); Connection con = null; DataSource datasource = null; try{ datasource = pool.main(); con=datasource.getConnection(); sb.append("SELECT * FROM database"); p = con.prepareStatement(sb.toString()); rs = p.executeQuery(); rs.close(); con.close(); p.close(); datasource.close(); System.out.println("success"); }catch (Exception e){ e.printStackTrace(); } }

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• trie reg exp parse step over char and continue

  - by forest.peterson

  Setup: 1) a string trie database formed from linked nodes and a vector array linking to the next node terminating in a leaf, 2) a recursive regular expression function that if A) char '*' continues down all paths until string length limit is reached, then continues down remaining string paths if valid, and B) char '?' continues down all paths for 1 char and then continues down remaining string paths if valid. 3) after reg expression the candidate strings are measured for edit distance against the 'try' string. Problem: the reg expression works fine for adding chars or swapping ? for a char but if the remaining string has an error then there is not a valid path to a terminating leaf; making the matching function redundant. I tried adding a 'step-over' ? char if the end of the node vector was reached and then followed every path of that node - allowing this step-over only once; resulted in a memory exception; I cannot find logically why it is accessing the vector out of range - bactracking? Questions: 1) how can the regular expression step over an invalid char and continue with the path? 2) why is swapping the 'sticking' char for '?' resulting in an overflow? Function: void Ontology::matchRegExpHelper(nodeT *w, string inWild, Set<string> &matchSet, string out, int level, int pos, int stepover) { if (inWild=="") { matchSet.add(out); } else { if (w->alpha.size() == pos) { int testLength = out.length() + inWild.length(); if (stepover == 0 && matchSet.size() == 0 && out.length() > 8 && testLength == tokenLength) {//candidate generator inWild[0] = '?'; matchRegExpHelper(w, inWild, matchSet, out, level, 0, stepover+1); } else return; //giveup on this path } if (inWild[0] == '?' || (inWild[0] == '*' && (out.length() + inWild.length() ) == level ) ) { //wild matchRegExpHelper(w->alpha[pos].next, inWild.substr(1), matchSet, out+w->alpha[pos].letter, level, 0, stepover);//follow path -> if ontology is full, treat '*' like a '?' } else if (inWild[0] == '*') matchRegExpHelper(w->alpha[pos].next, '*'+inWild.substr(1), matchSet, out+w->alpha[pos].letter, level, 0, stepover); //keep adding chars if (inWild[0] == w->alpha[pos].letter) //follow self matchRegExpHelper(w->alpha[pos].next, inWild.substr(1), matchSet, out+w->alpha[pos].letter, level, 0, stepover); //follow char matchRegExpHelper(w, inWild, matchSet, out, level, pos+1, stepover);//check next path } } Error Message: +str "Attempt to access index 1 in a vector of size 1." std::basic_string<char,std::char_traits<char>,std::allocator<char> > +err {msg="Attempt to access index 1 in a vector of size 1." } ErrorException Note: this function works fine for hundreds of test strings with '*' wilds if the extra stepover gate is not used Semi-Solved: I place a pos < w->alpha.size() condition on each path that calls w->alpha[pos]... - this prevented the backtrack calls from attempting to access the vector with an out of bounds index value. Still have other issues to work out - it loops infinitely adding the ? and backtracking to remove it, then repeat. But, moving forward now. Revised question: why during backtracking is the position index accumulating and/or not deincrementing - so at somepoint it calls w->alpha[pos]... with an invalid position that is either remaining from the next node or somehow incremented pos+1 when passing upward?

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• Custom string class (C++)

  - by Sanctus2099

  Hey guys. I'm trying to write my own C++ String class for educational and need purposes. The first thing is that I don't know that much about operators and that's why I want to learn them. I started writing my class but when I run it it blocks the program but does not do any crash. Take a look at the following code please before reading further: class CString { private: char* cstr; public: CString(); CString(char* str); CString(CString& str); ~CString(); operator char*(); operator const char*(); CString operator+(const CString& q)const; CString operator=(const CString& q); }; First of all I'm not so sure I declared everything right. I tried googleing about it but all the tutorials about overloading explain the basic ideea which is very simple but lack to explain how and when each thing is called. For instance in my = operator the program calls CString(CString& str); but I have no ideea why. I have also attached the cpp file below: CString::CString() { cstr=0; } CString::CString(char *str) { cstr=new char[strlen(str)]; strcpy(cstr,str); } CString::CString(CString& q) { if(this==&q) return; cstr = new char[strlen(q.cstr)+1]; strcpy(cstr,q.cstr); } CString::~CString() { if(cstr) delete[] cstr; } CString::operator char*() { return cstr; } CString::operator const char* () { return cstr; } CString CString::operator +(const CString &q) const { CString s; s.cstr = new char[strlen(cstr)+strlen(q.cstr)+1]; strcpy(s.cstr,cstr); strcat(s.cstr,q.cstr); return s; } CString CString::operator =(const CString &q) { if(this!=&q) { if(cstr) delete[] cstr; cstr = new char[strlen(q.cstr)+1]; strcpy(cstr,q.cstr); } return *this; } For testing I used a code just as simple as this CString a = CString("Hello") + CString(" World"); printf(a); I tried debugging it but at a point I get lost. First it calls the constructor 2 times for "hello" and for " world". Then it get's in the + operator which is fine. Then it calls the constructor for the empty string. After that it get's into "CString(CString& str)" and now I'm lost. Why is this happening? After this I noticed my string containing "Hello World" is in the destructor (a few times in a row). Again I'm very puzzeled. After converting again from char* to Cstring and back and forth it stops. It never get's into the = operator but neither does it go further. printf(a) is never reached. I use VisualStudio 2010 for this but it's basically just standard c++ code and thus I don't think it should make that much of a difference

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• Not reaction to pressing button

  - by Orange91

  I have a ring in primefaces: <h:form> <p:ring id="ring" value="#{ringBean.images}" var="image" styleClass="image-ring" easing="easeInOutBack"> <p:graphicImage value="./../../images/#{image.image}" width="150" height="150"/> <p:commandButton value="#{image.name}" action="#{image.action}" /> </p:ring> </h:form> My RingBean: @ManagedBean @RequestScoped public class RingBean implements Serializable{ private List<PersonImage> images; private PersonImage selectedPerson; public RingBean() { images = new ArrayList<PersonImage>(); images.add(new PersonImage("person3.png", "Pacjent", "patientList")); images.add(new PersonImage("person4.png", "Admin", "adminList")); images.add(new PersonImage("person5.png", "Lekarz", "doctorList")); images.add(new PersonImage("person6.png", "Sekretarka", "secretaryList")); images.add(new PersonImage("person7.png", "Nieaktywni", "inactiveList")); } public List<PersonImage> getImages() { return images; } public PersonImage getSelectedPerson() { return selectedPerson; } public void setSelectedPerson(PersonImage selectedPerson) { this.selectedPerson = selectedPerson; } } PersonImage class: public class PersonImage { String image; String name; String action; public PersonImage() { } public PersonImage(String image, String name, String action) { this.image = image; this.name = name; this.action = action; } public String getImage() { return image; } public void setImage(String image) { this.image = image; } public String getName() { return name; } public void setName(String name) { this.name = name; } public String getAction() { return action; } public void setAction(String action) { this.action = action; } } faces-config: <navigation-case> <from-outcome>adminList</from-outcome> <to-view-id>/protected/admin/adminList.xhtml</to-view-id> <redirect/> </navigation-case> <navigation-case> <from-outcome>doctorList</from-outcome> <to-view-id>/protected/admin/doctorList.xhtml</to-view-id> <redirect/> </navigation-case> <navigation-case> <from-outcome>patientList</from-outcome> <to-view-id>/protected/admin/patientList.xhtml</to-view-id> <redirect/> </navigation-case> <navigation-case> <from-outcome>secretaryList</from-outcome> <to-view-id>/protected/admin/secretaryList.xhtml</to-view-id> <redirect/> </navigation-case> When i pressed my button, not reaction. Why? I added the action in button: And in Ring I add: images.add(new PersonImage("person4.png", "Admin", "adminList")); action is adminList. Why this not work? When i changed in button: <p:commandButton value="#{image.name}" action="adminList" /> all work. Why? Both construction returned identical string.

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• The Microsoft Ajax Library and Visual Studio Beta 2

  - by Stephen Walther

  Visual Studio 2010 Beta 2 was released this week and one of the first things that I hope you notice is that it no longer contains the latest version of ASP.NET AJAX. What happened? Where did AJAX go? Just like Sting and The Police, just like Phil Collins and Genesis, just like Greg Page and the Wiggles, AJAX has gone out of band! We are starting a solo career. A Name Change First things first. In previous releases, our Ajax framework was named ASP.NET AJAX. We now have changed the name of the framework to the Microsoft Ajax Library. There are two reasons behind this name change. First, the members of the Ajax team got tired of explaining to everyone that our Ajax framework is not tied to the server-side ASP.NET framework. You can use the Microsoft Ajax Library with ASP.NET Web Forms, ASP.NET MVC, PHP, Ruby on RAILS, and even pure HTML applications. Our framework can be used as a client-only framework and having the word ASP.NET in our name was confusing people. Second, it was time to start spelling the word Ajax like everyone else. Notice that the name is the Microsoft Ajax Library and not the Microsoft AJAX library. Originally, Microsoft used upper case AJAX because AJAX originally was an acronym for Asynchronous JavaScript and XML. And, according to Strunk and Wagnell, acronyms should be all uppercase. However, Ajax is one of those words that have migrated from acronym status to “just a word” status. So whenever you hear one of your co-workers talk about ASP.NET AJAX, gently correct your co-worker and say “It is now called the Microsoft Ajax Library.” Why OOB? But why move out-of-band (OOB)? The short answer is that we have had approximately 6 preview releases of the Microsoft Ajax Library over the last year. That’s a lot. We pride ourselves on being agile. Client-side technology evolves quickly. We want to be able to get a preview version of the Microsoft Ajax Library out to our customers, get feedback, and make changes to the library quickly. Shipping the Microsoft Ajax Library out-of-band keeps us agile and enables us to continue to ship new versions of the library even after ASP.NET 4 ships. Showing Love for JavaScript Developers One area in which we have received a lot of feedback is around making the Microsoft Ajax Library easier to use for developers who are comfortable with JavaScript. We also wanted to make it easy for jQuery developers to take advantage of the innovative features of the Microsoft Ajax Library. To achieve these goals, we’ve added the following features to the Microsoft Ajax Library (these features are included in the latest preview release that you can download right now): A simplified imperative syntax – We wanted to make it brain-dead simple to create client-side Ajax controls when writing JavaScript. A client script loader – We wanted the Microsoft Ajax Library to load all of the scripts required by a component or control automatically. jQuery integration – We love the jQuery selector syntax. We wanted to make it easy for jQuery developers to use the Microsoft Ajax Library without changing their programming style. If you are interested in learning about these new features of the Microsoft Ajax Library, I recommend that you read the following blog post by Scott Guthrie: http://weblogs.asp.net/scottgu/archive/2009/10/15/announcing-microsoft-ajax-library-preview-6-and-the-microsoft-ajax-minifier.aspx Downloading the Latest Version of the Microsoft Ajax Library Currently, the best place to download the latest version of the Microsoft Ajax Library is directly from the ASP.NET CodePlex project: http://aspnet.codeplex.com/ As I write this, the current version is Preview 6. The next version is coming out at the PDC. Summary I’m really excited about the future of the Microsoft Ajax Library. Moving outside of the ASP.NET framework provides us the flexibility to remain agile and continue to innovate aggressively. The latest preview release of the Microsoft Ajax Library includes several major new features including a client script loader, jQuery integration, and a simplified client control creation syntax.

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• SQL SERVER – Video – Beginning Performance Tuning with SQL Server Execution Plan

  - by pinaldave

  Traveling can be most interesting or most exhausting experience. However, traveling is always the most enlightening experience one can have. While going to long journey one has to prepare a lot of things. Pack necessary travel gears, clothes and medicines. However, the most essential part of travel is the journey to the destination. There are many variations one prefer but the ultimate goal is to have a delightful experience during the journey. Here is the video available which explains how to begin with SQL Server Execution plans. Performance Tuning is a Journey Performance tuning is just like a long journey. The goal of performance tuning is efficient and least resources consuming query execution with accurate results. Just as maps are the most essential aspect of performance tuning the same way, execution plans are essentially maps for SQL Server to reach to the resultset. The goal of the execution plan is to find the most efficient path which translates the least usage of the resources (CPU, memory, IO etc). Execution Plans are like Maps When online maps were invented (e.g. Bing, Google, Mapquests etc) initially it was not possible to customize them. They were given a single route to reach to the destination. As time evolved now it is possible to give various hints to the maps, for example ‘via public transport’, ‘walking’, ‘fastest route’, ‘shortest route’, ‘avoid highway’. There are places where we manually drag the route and make it appropriate to our needs. The same situation is with SQL Server Execution Plans, if we want to tune the queries, we need to understand the execution plans and execution plans internals. We need to understand the smallest details which relate to execution plan when we our destination is optimal queries. Understanding Execution Plans The biggest challenge with maps are figuring out the optimal path. The same way the  most common challenge with execution plans is where to start from and which precise route to take. Here is a quick list of the frequently asked questions related to execution plans: Should I read the execution plans from bottoms up or top down? Is execution plans are left to right or right to left? What is the relational between actual execution plan and estimated execution plan? When I mouse over operator I see CPU and IO but not memory, why? Sometime I ran the query multiple times and I get different execution plan, why? How to cache the query execution plan and data? I created an optimal index but the query is not using it. What should I change – query, index or provide hints? What are the tools available which helps quickly to debug performance problems? Etc… Honestly the list is quite a big and humanly impossible to write everything in the words. SQL Server Performance:  Introduction to Query Tuning My friend Vinod Kumar and I have created for the same a video learning course for beginning performance tuning. We have covered plethora of the subject in the course. Here is the quick list of the same: Execution Plan Basics Essential Indexing Techniques Query Design for Performance Performance Tuning Tools Tips and Tricks Checklist: Performance Tuning We believe we have covered a lot in this four hour course and we encourage you to go over the video course if you are interested in Beginning SQL Server Performance Tuning and Query Tuning. Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Optimization, SQL Performance, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology, Video Tagged: Execution Plan

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• List of blogs - year 2010

  - by hajan

  This is the last day of year 2010 and I would like to add links to all blogs I have posted in this year. First, I would like to mention that I started blogging in ASP.NET Community in May / June 2010 and have really enjoyed writing for my favorite technologies, such as: ASP.NET, jQuery/JavaScript, C#, LINQ, Web Services etc. I also had great feedback either through comments on my blogs or in Twitter, Facebook, LinkedIn where I met many new experts just as a result of my blog posts. Thanks to the interesting topics I have in my blog, I became DZone MVB. Here is the list of blogs I made in 2010 in my ASP.NET Community Weblog: (newest to oldest) Great library of ASP.NET videos – Pluralsight! NDepend – Code Query Language (CQL) NDepend tool – Why every developer working with Visual Studio.NET must try it! jQuery Templates in ASP.NET - Blogs Series jQuery Templates - XHTML Validation jQuery Templates with ASP.NET MVC jQuery Templates - {Supported Tags} jQuery Templates – tmpl(), template() and tmplItem() Introduction to jQuery Templates ViewBag dynamic in ASP.NET MVC 3 - RC 2 Today I had a presentation on "Deep Dive into jQuery Templates in ASP.NET" jQuery Data Linking in ASP.NET How do you prefer getting bundles of technologies?? Case-insensitive XPath query search on XML Document in ASP.NET jQuery UI Accordion in ASP.NET MVC - feed with data from database (Part 3) jQuery UI Accordion in ASP.NET WebForms - feed with data from database (Part 2) jQuery UI Accordion in ASP.NET – Client side implementation (Part 1) Using Images embedded in Project’s Assembly Macedonian Code Camp 2010 event has finished successfully Tips and Tricks: Deferred execution using LINQ Using System.Diagnostics.Stopwatch class to measure the elapsed time Speaking at Macedonian Code Camp 2010 URL Routing in ASP.NET 4.0 Web Forms Conflicts between ASP.NET AJAX UpdatePanels & jQuery functions Integration of jQuery DatePicker in ASP.NET Website – Localization (part 3) Why not to use HttpResponse.Close and HttpResponse.End Calculate Business Days using LINQ Get Distinct values of an Array using LINQ Using CodeRun browser-based IDE to create ASP.NET Web Applications Using params keyword – Methods with variable number of parameters Working with Code Snippets in VS.NET  Working with System.IO.Path static class Calculating GridView total using JavaScript/JQuery The new SortedSet<T> Collection in .NET 4.0 JavaScriptSerializer – Dictionary to JSON Serialization and Deserialization Integration of jQuery DatePicker in ASP.NET Website – JS Validation Script (part 2) Integration of jQuery DatePicker in ASP.NET Website (part 1) Transferring large data when using Web Services Forums dedicated to WebMatrix Microsoft WebMatrix – Short overview & installation Working with embedded resources in Project's assembly Debugging ASP.NET Web Services Save and Display YouTube Videos on ASP.NET Website Hello ASP.NET World... In addition, I would like to mention that I have big list of blog posts in CodeASP.NET Community (total 60 blogs) and the local MKDOT.NET Community (total 61 blogs). You may find most of my weblogs.asp.net/hajan blogs posted there too, but there you can find many others. In my blog on MKDOT.NET Community you can find most of my ASP.NET Weblog posts translated in Macedonian language, some of them posted in English and some other blogs that were posted only there. By reading my blogs, I hope you have learnt something new or at least have confirmed your knowledge. And also, if you haven't, I encourage you to start blogging and share your Microsoft Tech. thoughts with all of us... Sharing and spreading knowledge is definitely one of the noblest things which we can do in our life. "Give a man a fish and he will eat for a day. Teach a man to fish and he will eat for a lifetime" HAPPY NEW 2011 YEAR!!! Best Regards, Hajan

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