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• Service Broker, not ETL

  - by jamiet

  I have been very quiet on this blog of late and one reason for that is I have been very busy on a client project that I would like to talk about a little here. The client that I have been working for has a website that runs on a distributed architecture utilising a messaging infrastructure for communication between different endpoints. My brief was to build a system that could consume these messages and produce analytical information in near-real-time. More specifically I basically had to deliver a data warehouse however it was the real-time aspect of the project that really intrigued me. This real-time requirement meant that using an Extract transformation, Load (ETL) tool was out of the question and so I had no choice but to write T-SQL code (i.e. stored-procedures) to process the incoming messages and load the data into the data warehouse. This concerned me though – I had no way to control the rate at which data would arrive into the system yet we were going to have end-users querying the system at the same time that those messages were arriving; the potential for contention in such a scenario was pretty high and and was something I wanted to minimise as much as possible. Moreover I did not want the processing of data inside the data warehouse to have any impact on the customer-facing website. As you have probably guessed from the title of this blog post this is where Service Broker stepped in! For those that have not heard of it Service Broker is a queuing technology that has been built into SQL Server since SQL Server 2005. It provides a number of features however the one that was of interest to me was the fact that it facilitates asynchronous data processing which, in layman’s terms, means the ability to process some data without requiring the system that supplied the data having to wait for the response. That was a crucial feature because on this project the customer-facing website (in effect an OLTP system) would be calling one of our stored procedures with each message – we did not want to cause the OLTP system to wait on us every time we processed one of those messages. This asynchronous nature also helps to alleviate the contention problem because the asynchronous processing activity is handled just like any other task in the database engine and hence can wait on another task (such as an end-user query). Service Broker it was then! The stored procedure called by the OLTP system would simply put the message onto a queue and we would use a feature called activation to pick each message off the queue in turn and process it into the warehouse. At the time of writing the system is not yet up to full capacity but so far everything seems to be working OK (touch wood) and crucially our users are seeing data in near-real-time. By near-real-time I am talking about latencies of a few minutes at most and to someone like me who is used to building systems that have overnight latencies that is a huge step forward! So then, am I advocating that you all go out and dump your ETL tools? Of course not, no! What this project has taught me though is that in certain scenarios there may be better ways to implement a data warehouse system then the traditional “load data in overnight” approach that we are all used to. Moreover I have really enjoyed getting to grips with a new technology and even if you don’t want to use Service Broker you might want to consider asynchronous messaging architectures for your BI/data warehousing solutions in the future. This has been a very high level overview of my use of Service Broker and I have deliberately left out much of the minutiae of what has been a very challenging implementation. Nonetheless I hope I have caused you to reflect upon your own approaches to BI and question whether other approaches may be more tenable. All comments and questions gratefully received! Lastly, if you have never used Service Broker before and want to kick the tyres I have provided below a very simple “Service Broker Hello World” script that will create all of the objects required to facilitate Service Broker communications and then send the message “Hello World” from one place to anther! This doesn’t represent a “proper” implementation per se because it doesn’t close down down conversation objects (which you should always do in a real-world scenario) but its enough to demonstrate the capabilities! @Jamiet ----------------------------------------------------------------------------------------------- /*This is a basic Service Broker Hello World app. Have fun! -Jamie */ USE MASTER GO CREATE DATABASE SBTest GO --Turn Service Broker on! ALTER DATABASE SBTest SET ENABLE_BROKER GO USE SBTest GO -- 1) we need to create a message type. Note that our message type is -- very simple and allowed any type of content CREATE MESSAGE TYPE HelloMessage VALIDATION = NONE GO -- 2) Once the message type has been created, we need to create a contract -- that specifies who can send what types of messages CREATE CONTRACT HelloContract (HelloMessage SENT BY INITIATOR) GO --We can query the metadata of the objects we just created SELECT * FROM   sys.service_message_types WHERE name = 'HelloMessage'; SELECT * FROM   sys.service_contracts WHERE name = 'HelloContract'; SELECT * FROM   sys.service_contract_message_usages WHERE  service_contract_id IN (SELECT service_contract_id FROM sys.service_contracts WHERE name = 'HelloContract') AND        message_type_id IN (SELECT message_type_id FROM sys.service_message_types WHERE name = 'HelloMessage'); -- 3) The communication is between two endpoints. Thus, we need two queues to -- hold messages CREATE QUEUE SenderQueue CREATE QUEUE ReceiverQueue GO --more querying metatda SELECT * FROM sys.service_queues WHERE name IN ('SenderQueue','ReceiverQueue'); --we can also select from the queues as if they were tables SELECT * FROM SenderQueue   SELECT * FROM ReceiverQueue   -- 4) Create the required services and bind them to be above created queues CREATE SERVICE Sender   ON QUEUE SenderQueue CREATE SERVICE Receiver   ON QUEUE ReceiverQueue (HelloContract) GO --more querying metadata SELECT * FROM sys.services WHERE name IN ('Receiver','Sender'); -- 5) At this point, we can begin the conversation between the two services by -- sending messages DECLARE @conversationHandle UNIQUEIDENTIFIER DECLARE @message NVARCHAR(100) BEGIN   BEGIN TRANSACTION;   BEGIN DIALOG @conversationHandle         FROM SERVICE Sender         TO SERVICE 'Receiver'         ON CONTRACT HelloContract WITH ENCRYPTION=OFF   -- Send a message on the conversation   SET @message = N'Hello, World';   SEND  ON CONVERSATION @conversationHandle         MESSAGE TYPE HelloMessage (@message)   COMMIT TRANSACTION END GO --check contents of queues SELECT * FROM SenderQueue   SELECT * FROM ReceiverQueue   GO -- Receive a message from the queue RECEIVE CONVERT(NVARCHAR(MAX), message_body) AS MESSAGE FROM ReceiverQueue GO --If no messages were received and/or you can't see anything on the queues you may wish to check the following for clues: SELECT * FROM sys.transmission_queue -- Cleanup DROP SERVICE Sender DROP SERVICE Receiver DROP QUEUE SenderQueue DROP QUEUE ReceiverQueue DROP CONTRACT HelloContract DROP MESSAGE TYPE HelloMessage GO USE MASTER GO DROP DATABASE SBTest GO

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• Finding vectors with two points

  - by Christian Careaga

  We're are trying to get the direction of a projectile but we can't find out how For example: [1,1] will go SE [1,-1] will go NE [-1,-1] will go NW and [-1,1] will go SW we need an equation of some sort that will take the player pos and the mouse pos and find which direction the projectile needs to go. Here is where we are plugging in the vectors: def update(self): self.rect.x += self.vector[0] self.rect.y += self.vector[1] Then we are blitting the projectile at the rects coords.

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• SQL SERVER – Fundamentals of Columnstore Index

  - by pinaldave

  There are two kind of storage in database. Row Store and Column Store. Row store does exactly as the name suggests – stores rows of data on a page – and column store stores all the data in a column on the same page. These columns are much easier to search – instead of a query searching all the data in an entire row whether the data is relevant or not, column store queries need only to search much lesser number of the columns. This means major increases in search speed and hard drive use. Additionally, the column store indexes are heavily compressed, which translates to even greater memory and faster searches. I am sure this looks very exciting and it does not mean that you convert every single index from row store to column store index. One has to understand the proper places where to use row store or column store indexes. Let us understand in this article what is the difference in Columnstore type of index. Column store indexes are run by Microsoft’s VertiPaq technology. However, all you really need to know is that this method of storing data is columns on a single page is much faster and more efficient. Creating a column store index is very easy, and you don’t have to learn new syntax to create them. You just need to specify the keyword “COLUMNSTORE” and enter the data as you normally would. Keep in mind that once you add a column store to a table, though, you cannot delete, insert or update the data – it is READ ONLY. However, since column store will be mainly used for data warehousing, this should not be a big problem. You can always use partitioning to avoid rebuilding the index. A columnstore index stores each column in a separate set of disk pages, rather than storing multiple rows per page as data traditionally has been stored. The difference between column store and row store approaches is illustrated below: In case of the row store indexes multiple pages will contain multiple rows of the columns spanning across multiple pages. In case of column store indexes multiple pages will contain multiple single columns. This will lead only the columns needed to solve a query will be fetched from disk. Additionally there is good chance that there will be redundant data in a single column which will further help to compress the data, this will have positive effect on buffer hit rate as most of the data will be in memory and due to same it will not need to be retrieved. Let us see small example of how columnstore index improves the performance of the query on a large table. As a first step let us create databaseset which is large enough to show performance impact of columnstore index. The time taken to create sample database may vary on different computer based on the resources. USE AdventureWorks GO -- Create New Table CREATE TABLE [dbo].[MySalesOrderDetail]( [SalesOrderID] [int] NOT NULL, [SalesOrderDetailID] [int] NOT NULL, [CarrierTrackingNumber] [nvarchar](25) NULL, [OrderQty] [smallint] NOT NULL, [ProductID] [int] NOT NULL, [SpecialOfferID] [int] NOT NULL, [UnitPrice] [money] NOT NULL, [UnitPriceDiscount] [money] NOT NULL, [LineTotal] [numeric](38, 6) NOT NULL, [rowguid] [uniqueidentifier] NOT NULL, [ModifiedDate] [datetime] NOT NULL ) ON [PRIMARY] GO -- Create clustered index CREATE CLUSTERED INDEX [CL_MySalesOrderDetail] ON [dbo].[MySalesOrderDetail] ( [SalesOrderDetailID]) GO -- Create Sample Data Table -- WARNING: This Query may run upto 2-10 minutes based on your systems resources INSERT INTO [dbo].[MySalesOrderDetail] SELECT S1.* FROM Sales.SalesOrderDetail S1 GO 100 Now let us do quick performance test. I have kept STATISTICS IO ON for measuring how much IO following queries take. In my test first I will run query which will use regular index. We will note the IO usage of the query. After that we will create columnstore index and will measure the IO of the same. -- Performance Test -- Comparing Regular Index with ColumnStore Index USE AdventureWorks GO SET STATISTICS IO ON GO -- Select Table with regular Index SELECT ProductID, SUM(UnitPrice) SumUnitPrice, AVG(UnitPrice) AvgUnitPrice, SUM(OrderQty) SumOrderQty, AVG(OrderQty) AvgOrderQty FROM [dbo].[MySalesOrderDetail] GROUP BY ProductID ORDER BY ProductID GO -- Table 'MySalesOrderDetail'. Scan count 1, logical reads 342261, physical reads 0, read-ahead reads 0. -- Create ColumnStore Index CREATE NONCLUSTERED COLUMNSTORE INDEX [IX_MySalesOrderDetail_ColumnStore] ON [MySalesOrderDetail] (UnitPrice, OrderQty, ProductID) GO -- Select Table with Columnstore Index SELECT ProductID, SUM(UnitPrice) SumUnitPrice, AVG(UnitPrice) AvgUnitPrice, SUM(OrderQty) SumOrderQty, AVG(OrderQty) AvgOrderQty FROM [dbo].[MySalesOrderDetail] GROUP BY ProductID ORDER BY ProductID GO It is very clear from the results that query is performance extremely fast after creating ColumnStore Index. The amount of the pages it has to read to run query is drastically reduced as the column which are needed in the query are stored in the same page and query does not have to go through every single page to read those columns. If we enable execution plan and compare we can see that column store index performance way better than regular index in this case. Let us clean up the database. -- Cleanup DROP INDEX [IX_MySalesOrderDetail_ColumnStore] ON [dbo].[MySalesOrderDetail] GO TRUNCATE TABLE dbo.MySalesOrderDetail GO DROP TABLE dbo.MySalesOrderDetail GO In future posts we will see cases where Columnstore index is not appropriate solution as well few other tricks and tips of the columnstore index. Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: Pinal Dave, PostADay, SQL, SQL Authority, SQL Index, SQL Optimization, SQL Performance, SQL Query, SQL Scripts, SQL Server, SQL Tips and Tricks, T SQL, Technology

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• Plan Caching and Query Memory Part II (Hash Match) – When not to use stored procedure - Most common performance mistake SQL Server developers make.

  - by sqlworkshops

  SQL Server estimates Memory requirement at compile time, when stored procedure or other plan caching mechanisms like sp_executesql or prepared statement are used, the memory requirement is estimated based on first set of execution parameters. This is a common reason for spill over tempdb and hence poor performance. Common memory allocating queries are that perform Sort and do Hash Match operations like Hash Join or Hash Aggregation or Hash Union. This article covers Hash Match operations with examples. It is recommended to read Plan Caching and Query Memory Part I before this article which covers an introduction and Query memory for Sort. In most cases it is cheaper to pay for the compilation cost of dynamic queries than huge cost for spill over tempdb, unless memory requirement for a query does not change significantly based on predicates.   This article covers underestimation / overestimation of memory for Hash Match operation. Plan Caching and Query Memory Part I covers underestimation / overestimation for Sort. It is important to note that underestimation of memory for Sort and Hash Match operations lead to spill over tempdb and hence negatively impact performance. Overestimation of memory affects the memory needs of other concurrently executing queries. In addition, it is important to note, with Hash Match operations, overestimation of memory can actually lead to poor performance.   To read additional articles I wrote click here.   The best way to learn is to practice. To create the below tables and reproduce the behavior, join the mailing list by using this link: www.sqlworkshops.com/ml and I will send you the table creation script. Most of these concepts are also covered in our webcasts: www.sqlworkshops.com/webcasts  Let’s create a Customer’s State table that has 99% of customers in NY and the rest 1% in WA.Customers table used in Part I of this article is also used here.To observe Hash Warning, enable 'Hash Warning' in SQL Profiler under Events 'Errors and Warnings'. --Example provided by www.sqlworkshops.com drop table CustomersState go create table CustomersState (CustomerID int primary key, Address char(200), State char(2)) go insert into CustomersState (CustomerID, Address) select CustomerID, 'Address' from Customers update CustomersState set State = 'NY' where CustomerID % 100 != 1 update CustomersState set State = 'WA' where CustomerID % 100 = 1 go update statistics CustomersState with fullscan go   Let’s create a stored procedure that joins customers with CustomersState table with a predicate on State. --Example provided by www.sqlworkshops.com create proc CustomersByState @State char(2) as begin declare @CustomerID int select @CustomerID = e.CustomerID from Customers e inner join CustomersState es on (e.CustomerID = es.CustomerID) where es.State = @State option (maxdop 1) end go  Let’s execute the stored procedure first with parameter value ‘WA’ – which will select 1% of data. set statistics time on go --Example provided by www.sqlworkshops.com exec CustomersByState 'WA' goThe stored procedure took 294 ms to complete.  The stored procedure was granted 6704 KB based on 8000 rows being estimated.  The estimated number of rows, 8000 is similar to actual number of rows 8000 and hence the memory estimation should be ok.  There was no Hash Warning in SQL Profiler. To observe Hash Warning, enable 'Hash Warning' in SQL Profiler under Events 'Errors and Warnings'.   Now let’s execute the stored procedure with parameter value ‘NY’ – which will select 99% of data. -Example provided by www.sqlworkshops.com exec CustomersByState 'NY' go  The stored procedure took 2922 ms to complete.   The stored procedure was granted 6704 KB based on 8000 rows being estimated.    The estimated number of rows, 8000 is way different from the actual number of rows 792000 because the estimation is based on the first set of parameter value supplied to the stored procedure which is ‘WA’ in our case. This underestimation will lead to spill over tempdb, resulting in poor performance.   There was Hash Warning (Recursion) in SQL Profiler. To observe Hash Warning, enable 'Hash Warning' in SQL Profiler under Events 'Errors and Warnings'.   Let’s recompile the stored procedure and then let’s first execute the stored procedure with parameter value ‘NY’.  In a production instance it is not advisable to use sp_recompile instead one should use DBCC FREEPROCCACHE (plan_handle). This is due to locking issues involved with sp_recompile, refer to our webcasts, www.sqlworkshops.com/webcasts for further details.   exec sp_recompile CustomersByState go --Example provided by www.sqlworkshops.com exec CustomersByState 'NY' go  Now the stored procedure took only 1046 ms instead of 2922 ms.   The stored procedure was granted 146752 KB of memory. The estimated number of rows, 792000 is similar to actual number of rows of 792000. Better performance of this stored procedure execution is due to better estimation of memory and avoiding spill over tempdb.   There was no Hash Warning in SQL Profiler.   Now let’s execute the stored procedure with parameter value ‘WA’. --Example provided by www.sqlworkshops.com exec CustomersByState 'WA' go  The stored procedure took 351 ms to complete, higher than the previous execution time of 294 ms.    This stored procedure was granted more memory (146752 KB) than necessary (6704 KB) based on parameter value ‘NY’ for estimation (792000 rows) instead of parameter value ‘WA’ for estimation (8000 rows). This is because the estimation is based on the first set of parameter value supplied to the stored procedure which is ‘NY’ in this case. This overestimation leads to poor performance of this Hash Match operation, it might also affect the performance of other concurrently executing queries requiring memory and hence overestimation is not recommended.     The estimated number of rows, 792000 is much more than the actual number of rows of 8000.  Intermediate Summary: This issue can be avoided by not caching the plan for memory allocating queries. Other possibility is to use recompile hint or optimize for hint to allocate memory for predefined data range.Let’s recreate the stored procedure with recompile hint. --Example provided by www.sqlworkshops.com drop proc CustomersByState go create proc CustomersByState @State char(2) as begin declare @CustomerID int select @CustomerID = e.CustomerID from Customers e inner join CustomersState es on (e.CustomerID = es.CustomerID) where es.State = @State option (maxdop 1, recompile) end go  Let’s execute the stored procedure initially with parameter value ‘WA’ and then with parameter value ‘NY’. --Example provided by www.sqlworkshops.com exec CustomersByState 'WA' go exec CustomersByState 'NY' go  The stored procedure took 297 ms and 1102 ms in line with previous optimal execution times.   The stored procedure with parameter value ‘WA’ has good estimation like before.   Estimated number of rows of 8000 is similar to actual number of rows of 8000.   The stored procedure with parameter value ‘NY’ also has good estimation and memory grant like before because the stored procedure was recompiled with current set of parameter values.  Estimated number of rows of 792000 is similar to actual number of rows of 792000.    The compilation time and compilation CPU of 1 ms is not expensive in this case compared to the performance benefit.   There was no Hash Warning in SQL Profiler.   Let’s recreate the stored procedure with optimize for hint of ‘NY’. --Example provided by www.sqlworkshops.com drop proc CustomersByState go create proc CustomersByState @State char(2) as begin declare @CustomerID int select @CustomerID = e.CustomerID from Customers e inner join CustomersState es on (e.CustomerID = es.CustomerID) where es.State = @State option (maxdop 1, optimize for (@State = 'NY')) end go  Let’s execute the stored procedure initially with parameter value ‘WA’ and then with parameter value ‘NY’. --Example provided by www.sqlworkshops.com exec CustomersByState 'WA' go exec CustomersByState 'NY' go  The stored procedure took 353 ms with parameter value ‘WA’, this is much slower than the optimal execution time of 294 ms we observed previously. This is because of overestimation of memory. The stored procedure with parameter value ‘NY’ has optimal execution time like before.   The stored procedure with parameter value ‘WA’ has overestimation of rows because of optimize for hint value of ‘NY’.   Unlike before, more memory was estimated to this stored procedure based on optimize for hint value ‘NY’.    The stored procedure with parameter value ‘NY’ has good estimation because of optimize for hint value of ‘NY’. Estimated number of rows of 792000 is similar to actual number of rows of 792000.   Optimal amount memory was estimated to this stored procedure based on optimize for hint value ‘NY’.   There was no Hash Warning in SQL Profiler.   This article covers underestimation / overestimation of memory for Hash Match operation. Plan Caching and Query Memory Part I covers underestimation / overestimation for Sort. It is important to note that underestimation of memory for Sort and Hash Match operations lead to spill over tempdb and hence negatively impact performance. Overestimation of memory affects the memory needs of other concurrently executing queries. In addition, it is important to note, with Hash Match operations, overestimation of memory can actually lead to poor performance.   Summary: Cached plan might lead to underestimation or overestimation of memory because the memory is estimated based on first set of execution parameters. It is recommended not to cache the plan if the amount of memory required to execute the stored procedure has a wide range of possibilities. One can mitigate this by using recompile hint, but that will lead to compilation overhead. However, in most cases it might be ok to pay for compilation rather than spilling sort over tempdb which could be very expensive compared to compilation cost. The other possibility is to use optimize for hint, but in case one sorts more data than hinted by optimize for hint, this will still lead to spill. On the other side there is also the possibility of overestimation leading to unnecessary memory issues for other concurrently executing queries. In case of Hash Match operations, this overestimation of memory might lead to poor performance. When the values used in optimize for hint are archived from the database, the estimation will be wrong leading to worst performance, so one has to exercise caution before using optimize for hint, recompile hint is better in this case.   I explain these concepts with detailed examples in my webcasts (www.sqlworkshops.com/webcasts), I recommend you to watch them. The best way to learn is to practice. To create the above tables and reproduce the behavior, join the mailing list at www.sqlworkshops.com/ml and I will send you the relevant SQL Scripts.  Register for the upcoming 3 Day Level 400 Microsoft SQL Server 2008 and SQL Server 2005 Performance Monitoring & Tuning Hands-on Workshop in London, United Kingdom during March 15-17, 2011, click here to register / Microsoft UK TechNet.These are hands-on workshops with a maximum of 12 participants and not lectures. For consulting engagements click here.   Disclaimer and copyright information:This article refers to organizations and products that may be the trademarks or registered trademarks of their various owners. Copyright of this article belongs to R Meyyappan / www.sqlworkshops.com. You may freely use the ideas and concepts discussed in this article with acknowledgement (www.sqlworkshops.com), but you may not claim any of it as your own work. This article is for informational purposes only; you use any of the suggestions given here entirely at your own risk.   R Meyyappan [email protected] LinkedIn: http://at.linkedin.com/in/rmeyyappan

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• Apache 2: I have multiple domain names I want to point to one Virtual Host. Do I use ServerAlias?

  - by Chris Altman

  I have multiple domain names, for example: www.foo.com www.goo.com www.moo.com www.coo.com I want all of these domain names to resolve to one website AND to redirect to www.foo.com What is the best method to achieve this? Multiple entries? Use ServerAlias? Something else? If the best method is ServerAlias, what is the syntax? ServerAlias www.goo.com, www.moo.com, www.coo.com

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• SQL SERVER – Fix: Error: 8117: Operand data type bit is invalid for sum operator

  - by pinaldave

  Here is the very interesting error I received from a reader. He has very interesting question. He attempted to use BIT filed in the SUM aggregation function and he got following error. He went ahead with various different datatype (i.e. INT, TINYINT etc) and he was able to do the SUM but with BIT he faced the problem. Error Received: Msg 8117, Level 16, State 1, Line 1 Operand data type bit is invalid for sum operator. Reproduction of the error: Set up the environment USE tempdb GO -- Preparing Sample Data CREATE TABLE TestTable (ID INT, Flag BIT) GO INSERT INTO TestTable (ID, Flag) SELECT 1, 0 UNION ALL SELECT 2, 1 UNION ALL SELECT 3, 0 UNION ALL SELECT 4, 1 GO SELECT * FROM TestTable GO Following script will work fine: -- This will work fine SELECT SUM(ID) FROM TestTable GO However following generate error: -- This will generate error SELECT SUM(Flag) FROM TestTable GO The workaround is to convert or cast the BIT to INT: -- Workaround of error SELECT SUM(CONVERT(INT, Flag)) FROM TestTable GO Clean up the setup -- Clean up DROP TABLE TestTable GO Workaround: As mentioned in above script the workaround is to covert the bit datatype to another friendly data types like INT, TINYINT etc. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology

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• ASP.NET MVC2 and MemberShipProvider: How well do they go together?

  - by Sparhawk

  I have an existing ASP.NET application with lots of users and a large database. Now I want to have it in MVC 2. I do not want to migrate, I do it more or less from scratch. The database I want to keep and not touch too much. I already have my database tables and I also want to keep my LINQ to SQL-Layer. I didn't use a MembershipProvider in my current implementation (in ASP.NET 1.0 that wasn't strongly supported). So, either I write my own Membershipprovider to meet the needs of my database and app or I don't use the membershipprovider at all. I'd like to understand the consequences if I don't use the membership provider. What is linked to that? I understand that in ASP.NET the Login-Controls are linked to the provider. The AccountModel which is automatically generated with MVC2 could easily be changed to support my existing logic. What happens when a user is identified by a an AuthCookie? Does MVC use the MembershipProvider then? Am I overlooking something? I have the same questions regarding RoleProvider. Input is greatly appreciated.

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• How do I make Visual Studio automatically go to the first error in a build?

  - by Jon

  This is done manually by going to the "Error List" output window and double-clicking on the first error or pressing F8. Is there a way to automate this? (I'm using C++ if that matters.)

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• what type of bug causes a program to slowly use more processor power and all of a sudden go to 100%?

  - by reinier

  Hi, I was hoping to get some good ideas as to what might be causing a really nasty bug. This is a program which is transmitting data over a socket, and also receives messages back. I could explain lots more, but I don't think this will help here. I'm just searching for hypothetical problems which can cause the following behaviour: program runs processor time slowly accumulates (till around 60%) all of a sudden (could be after 30 but also after 60 seconds) the processor time shoots to 100%. the program halts completely In my syslog it always ends on one line with a memory allocation (something similar to: myArray = new byte[16384]) in the same thread. now here is the weird part: if I set the debugger anywhere...it immediately stops on that line. So just the act of setting a breakpoint, made the thread continue (it wasn't running since I saw no log output anymore) I was thinking 'deadlock' but that would not cause 100% processor power. If anything, the opposite. Also, setting a breakpoint would not cause a deadlock to end. anyone else a theoretical suggestion as to what kind of 'construct' might cause this effect? (apart from 'bad programming') ;^) thanks EDIT: I just noticed.... by setting the sendspeed slower, the problem shows itself much later than expected. I would think around the same amount of packets send...but no the amount of packets send is much higher this way before it has the same problem.

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• Django Inline formset for editing multiple related records at once - the right way to go?

  - by Bert

  Hi, When using inline formsets, how does one do paging? I'm using django 1.1. The situation I'm in, is that the user needs to be able to edit the related objects quickly and easily (which is why I think I should be using an inline formset). However, there can be a more than a hundred objects to edit, which makes a pretty large formset, so paging would make sense. Is there a better way to be doing this? Thanks Bert

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• is struts2 Framework dead? if so, which direction to go from here?

  - by Omnipresent

  I've been working in struts2 framework for the past year and a half. As I look around SO it seems like struts2 questions get the least amount of hits. At first I thought it was because the SO community is not much into struts2, but this is the case in other forums as well. Only the struts2 mailing list is pretty active. I think struts2 is slowly becoming a dinosaur framework and I want to move on. I've dabbled a little with other stuff like RoR, Grails, Django, .NET MVC but I've never really committed and made a pact with myself to sit down and learn these. Maybe its the fact that I dont know the languages that these frameworks are built on. Spending a day or two with RoR makes me want to choke some of the JAR files and struts2 html tags and .NET MVC looks promising but not knowing c# ties me back. My question is, have you been on the same path? Did anyone used to do struts2 before and now changed to something new? What would you suggest I learn after Struts2? And lastly, as a developer how do you motivate yourself to learn a new framework, or a language? for me, just typing the code provided in the book is dead boring.

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• My ListView backgrounds go black during scrolling - how to fix?

  - by Eno

  Ive specified white backgrounds for pretty much all widgets and it works, except when scrolling. The background container goes black during scrolling resulting in annoying flickering.

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• SVN: Release branch headaches, how to merge in website revisions as and when cleared to go live?

  - by Pete Duncanson

  I need a sanity check here if we can, any ideas on correcting/changing the following are very welcome! We've been getting ourselves in knots of late with our SVN and are trying to correct it by putting a Trunk/Release system in place. We have a large website that we develop on and we store it all in SVN. Heres what we had in mind: We have trunk and a release branch All work gets checked into Trunk. When a feature is deemed ready for the next release it is merged into a Release branch. We only have one release branch and just tag "Latest" when we do a push to live We hope to be able to get all the files changed from Latest to Head to give us a zip that we can upload (any ideas on an easy way to do this via scripting?) So we set all this up and where very happy with ourselves. Except its not working and heres why. We work on lots a different features/fixes/problems at once and they don't all get nicely checked in feature complete (but always working at least). Then sometimes you have to wait for Clients to sign off. As a result you end up with revisions which are "ready for live" being scattered with ones which are "still being worked on" in trunk. That means that the completed revisions are not getting merged in sequentially but out of order. I thought SVN could handle this, clever little thing it is, but apparently not. Heres an example: Pete changes some CSS to make a new button look pretty (Revision 1) Dave add some CSS to the bottom of the same CSS file as Pete's for a new feature (Revision 2) Dave's mod gets the nod so he merges it into Release and commits it with a log message mentioning revision number and bug tracking id. Pete adds more buttons to finish this mod, no CSS changes here though (Revision 3) Pete then merges his mods (Revision 1 and 3) into the Head of Release (which has Daves merge in it) but this over-writes Daves CSS additions which now dissapear completely. This leads to the site being broken and the Release branch being pretty much useless. So we tried some other ideas like reverting Release back to "Latest" and then just merging in all the Revisions 1,2 and 3 in order. This worked fine until we had Revision 4 which was not ready for live and Revision 5 which was. Suddenly we are getting ourselves in knots again with exactly the same problem! Ok so take three. Revert to Latest, merge in Revision 5, then do any update back to Head. Tree conflicts galore! So thats a no no. I cracked in the end and built it all up manaually but its not something I want to do regular, ideally I want to script our deployment but can't while Release is in such a mess. HELP! What the heck are we doing wrong? I can't seem to find any solutions to this problem of wanting different none sequential Revisions in Release. If its not possible thats fine but how the heck are we meant to get stuff live easily. We can't branch for every single change, the site takes 30 minutes+ to check out it would take too long. Side note, we are using TortoiseSVN so can we keep command line examples to a minimum in any answers? Latest version of TSVN and SVN Version 1.6 so we have the funky merge tracking etc. EDIT: An excellent blog post which deals with the dev/release cycle (although using GIT but still relivant) thought everyone would like to read it if they found this question interesting. (http://nvie.com/git-model) EDIT 2: I wrote a blog post on how to show which branch you are working on in your website which others have asked me about (http://www.offroadcode.com/2010/5/14/which-svn-branch-are-you-working-on.aspx). Hope that helps. In the meantime we are looking at Kiln and hoping to make the switch next month (gulp!)

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• How do I go about overloading C++ operators to allow for chaining?

  - by fneep

  I, like so many programmers before me, am tearing my hair out writing the right-of-passage-matrix-class-in-C++. I have never done very serious operator overloading and this is causing issues. Essentially, by stepping through This is what I call to cause the problems. cMatrix Kev = CT::cMatrix::GetUnitMatrix(4, true); Kev *= 4.0f; cMatrix Baz = Kev; Kev = Kev+Baz; //HERE! What seems to be happening according to the debugger is that Kev and Baz are added but then the value is lost and when it comes to reassigning to Kev, the memory is just its default dodgy values. How do I overload my operators to allow for this statement? My (stripped down) code is below. //header class cMatrix { private: float* _internal; UInt32 _r; UInt32 _c; bool _zeroindexed; //fast, assumes zero index, no safety checks float cMatrix::_getelement(UInt32 r, UInt32 c) { return _internal[(r*this->_c)+c]; } void cMatrix::_setelement(UInt32 r, UInt32 c, float Value) { _internal[(r*this->_c)+c] = Value; } public: cMatrix(UInt32 r, UInt32 c, bool IsZeroIndexed); cMatrix( cMatrix& m); ~cMatrix(void); //operators cMatrix& operator + (cMatrix m); cMatrix& operator += (cMatrix m); cMatrix& operator = (const cMatrix &m); }; //stripped source file cMatrix::cMatrix(cMatrix& m) { _r = m._r; _c = m._c; _zeroindexed = m._zeroindexed; _internal = new float[_r*_c]; UInt32 size = GetElementCount(); for (UInt32 i = 0; i < size; i++) { _internal[i] = m._internal[i]; } } cMatrix::~cMatrix(void) { delete[] _internal; } cMatrix& cMatrix::operator+(cMatrix m) { return cMatrix(*this) += m; } cMatrix& cMatrix::operator*(float f) { return cMatrix(*this) *= f; } cMatrix& cMatrix::operator*=(float f) { UInt32 size = GetElementCount(); for (UInt32 i = 0; i < size; i++) { _internal[i] *= f; } return *this; } cMatrix& cMatrix::operator+=(cMatrix m) { if (_c != m._c || _r != m._r) { throw new cCTException("Cannot add two matrix classes of different sizes."); } if (!(_zeroindexed && m._zeroindexed)) { throw new cCTException("Zero-Indexed mismatch."); } for (UInt32 row = 0; row < _r; row++) { for (UInt32 column = 0; column < _c; column++) { float Current = _getelement(row, column) + m._getelement(row, column); _setelement(row, column, Current); } } return *this; } cMatrix& cMatrix::operator=(const cMatrix &m) { if (this != &m) { _r = m._r; _c = m._c; _zeroindexed = m._zeroindexed; delete[] _internal; _internal = new float[_r*_c]; UInt32 size = GetElementCount(); for (UInt32 i = 0; i < size; i++) { _internal[i] = m._internal[i]; } } return *this; }

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• Why Does the iPad Main View Refuse to go FullScreen?

  - by dugla

  I am doing an imaging app for iPad and it requires use of the entire screen. The approach I have used on iPhone does not appear to work on iPad. In Interface Builder I have set the UIToolbar to translucent.This code echos the dimensions of the main view before and after requesting fullscreen. (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions { [self.window addSubview:self.viewController.view]; NSLog(@"Hello Popover AD - application did Finish Launching With Options - viewSize: %f %f BEFORE", self.viewController.view.bounds.size.width, self.viewController.view.bounds.size.height); [self.viewController setWantsFullScreenLayout:YES]; [self.viewController.view layoutIfNeeded]; NSLog(@"Hello Popover AD - application did Finish Launching With Options - viewSize: %f %f AFTER", self.viewController.view.bounds.size.width, self.viewController.view.bounds.size.height); [self.window makeKeyAndVisible]; return YES; } This is what NSlog has to say: Hello Popover AD - application did Finish Launching With Options - viewSize: 768 1004 BEFORE Hello Popover AD - application did Finish Launching With Options - viewSize: 768 1004 AFTER Can someone please tell me what I am doing incorrectly here? Note, on iPhone I set fullscreen within the init method of the relevant ViewController. Can view resizing only be done in a ViewController? My ultimate goal is a fullscreen view nicely tucked underneath a translucent status bar and tool bar. I will retract the status/tool bars when user interaction begins in the main view. Thanks, Doug

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• How should I go about implementing a points-to analysis in Maude?

  - by reprogrammer

  I'm going to implement a points-to analysis algorithm. I'd like to implement this analysis mainly based on the algorithm by Whaley and Lam. Whaley and Lam use a BDD based implementation of Datalog to represent and compute the points-to analysis relations. The following lists some of the relations that are used in a typical points-to analysis. Note that D(w, z) :- A(w, x),B(x, y), C(y, z) means D(w, z) is true if A(w, x), B(x, y), and C(y, z) are all true. BDD is the data structure used to represent these relations. Relations input vP0 (variable : V, heap : H) input store (base : V, field : F, source : V) input load (base : V, field : F, dest : V) input assign (dest : V, source : V) output vP (variable : V, heap : H) output hP (base : H, field : F, target : H) Rules vP(v, h) :- vP0(v, h) vP(v1, h) :- assign(v1, v2), vP(v2, h) hP(h1, f,h2) :- store(v1, f, v2), vP(v1, h1), vP(v2, h2) vP(v2, h2) :- load(v1, f, v2), vP(v1, h1), hP(h1, f, h2) I need to understand if Maude is a good environment for implementing points-to analysis. I noticed that Maude uses a BDD library called BuDDy. But, it looks like that Maude uses BDDs for a different purpose, i.e. unification. So, I thought I might be able to use Maude instead of a Datalog engine to compute the relations of my points-to analysis. I assume Maude propagates independent information concurrently. And this concurrency could potentially make my points-to analysis faster than sequential processing of rules. But, I don't know the best way to represent my relations in Maude. Should I implement BDD in Maude myself, or Maude's internal unification based on BDD has the same effect?

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• Try Catch - Finally in If statement, how to go on after ?

  - by user313176

  how can I do that ? void x() {.... if (...) {try {} catch (ComException com) { throw com} finally // in any case, executed fine! {...instructions.......} } else // not executed in case of exception because the finally can't embrace the //else too... but this block of code needs to be executed in any case too... {} }

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• VBA: How go I get the total width from all controls in an Access form?

  - by Stefan Åstrand

  Hi, This is probably very basic stuff, but please bear in mind I am completely new to these things. I am working on a procedure for my Access datasheet forms that will: Adjust the width of each column to fit content Sum the total width of all columns and subtract it from the size of the window's width Adjust the width of one of the columns to fit the remaining space This is the code that adjusts the width of each column to fit content (which works fine): Dim Ctrl As Control Dim Path As String Dim ClmWidth As Integer 'Adjust column width to fit content For Each Ctrl In Me.Controls If TypeOf Ctrl Is TextBox Then Path = Ctrl.Name Me(Path).ColumnWidth = -2 End If Next Ctrl How should I write the code so I get the total width of all columns? Thanks a lot! Stefan

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• Why does my Workflow Service (4.0) variable go null in a DoWhile Activity?

  - by jlafay

  I have a WF service that I'm trying to setup receive activities to "Subscribe" and "Unsubscribe". I'm using This WF Durable Duplex Tutorial as a basis because my service performs callbacks to clients. Basically, think of it as a chat service. I can make client calls to the two receive activities just fine. What happens is the callback address of the client is passed in to Subscribe() on the service. The address is stored as a variable in the WF service and everything looks like it would work as to be expected. When a client calls Unsubscribe(), my watch I have set on the address var during debugging shows it as null. So what gives? Here's the basic setup of my WF service layout... Everything is enveloped in a DoWhile activity. Inside of that is a Pick activity and two Pick branches. The first branch is for subscribing activities. It has a receive-sendreply activity that assigns the string passed by the client to the WF address var. The second branch handles unsubscribing. The trigger is the Request activity and the client address is again passed in. From there it goes into a sequence, starting with an If. It checks to see if the unsubscribeAddress equals the address already subscribed. If it does, then it sets the address to String.Empty and sends a success message back to the client. Why would a variable that's scoped to the enveloping DoWhile activity be implicitly assigned to null? I'm trying to get this to work so I can implement multiple client subscribers from there and work on triggers that invoke callbacks to multiple clients. CONCAT EDIT: I set a breakpoint at the DoWhile level and my var is null once Unsubscribe() is called. When Subscribe() is invoked, the watch shows a value in the var all the way through. Until I Unsubscribe() with a client. Should I be using a While Activity instead?

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• Should you do validation checks that go outside the possiblility of normal user activity?

  - by Scarface

  Hey guys I have been thinking about form security a lot lately. I have been told time and time again to check if form input is a number if you are expecting a number or escape it in case (unless you use proper mysqli formatting) to avoid injection. 1.After the safety checks are done, should I do additional logic checks? For example, if the user is sending a friend request to them-self for example even if my user interface will not show the form if the user is looking at their own page.

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• How should I go about creating a point system for users like SO and yahoo answers?(PHP)

  - by ggfan

  I am creating a voting system for a Q&A site project in which if a user asks a question, he/she losses -5 points; answer a question +5, vote a question +1, etc. (kind of like SO and yahoo answers) --To create the basic arithmetic, I have a "users_points" table that relates the user_id and their total points. +---+---------+ | 1 | 100 | +---+---------+ | 2 | 54 | +---+---------+ --Basically if the users does certain task, it would + or - the points. How do I prevent users from say voting an answer up 100 times. ex: I want a user to be only able to vote once per question, etc.

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• Why would some POST data go missing when using Uploadify?

  - by Chad Johnson

  I have been using Uploadify in my PHP application for the last couple months, and I've been trying to track down an elusive bug. I receive emails when fatal errors occur, and they provide me a good amount of details. I've received dozens of them. I have not, however, been able to reproduce the problem myself. Some users (like myself) experience no problem, while others do. Before I give details of the problem, here is the flow. User visits edit screen for a page in the CMS I am using. Record id for the page is put into a form as a hidden value. User clicks the Uploadify browse button and selects a file (only single file selection is allowed). User clicks Submit button for my form. jQuery intercepts the form submit action, triggers Uploadify to start uploading, and returns false for the submit action (manually cancelling the form submit event so that Uploadify can take over). Uploadify uploads to a custom process script. Uploadify finishes uploading and triggers the Javascript completion callback. The Javascript callback calls $('#myForm').submit() to submit the form. Now that's what SHOULD happen. I've received reports of the upload freezing at 100% and also others where "I/O Error" is displayed. What's happening is, the form is submitting with the completion callback, but some post parameters present in the form are simply not in the post data. The id for the page, which earlier I said is added to the form as a hidden field, is simply not there in the post data ($_POST)--there is no item for 'id' in the $_POST array. The strange thing is, the post data DOES contain values for some fields. For instance, I have an input of type text called "name" which is for the record name, and it does show up in the post data. Here is what I've gathered: This has been happening on Mac OSX 10.5 and 10.6, Windows XP, and Windows 7. I can post exact user agent strings if that helps. Users must use Flash 10.0.12 or later. We've made it so the form reverts to using a normal "file" field if they have < 10.0.12. Does anyone have ANY ideas at all what the cause of this could be?

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• MVVM- How would I go about propagating settings between my main view-model (and other view-models) a

  - by Justin

  I am building a settings dialog for my application and right now all of the settings correspond with settings on the main view-model, but as I add more view's and view-models some may not. I need to know what the best practice is for loading the current settings into the settings dialog and then saving the settings to thier corresponding view-models if the user clicks okay. I will not be using the Properties.Settings.Default system to store settings since I want my application to be as portable as possible and this would store user scoped settings in the directory: C:\Users\ username \Local Settings\Application Data\ ApplicationName Instead of in my application's directory. In case it makes any difference I am using the MVVM Light Toolkit by Laurent Bugnion.

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• Why would some $_POST variables go missing for a form with PHP?

  - by Chad Johnson

  Sometimes, multiple times a day in fact, users of my web application are submitting a certain form which has about a dozen form fields, half of which are hidden fields, and half of the $_POST data is simply not present in the processing script. Note that the fields that are not present are at the very bottom of the form. I know this because this raises a fatal error, and an email is dispatched to me which includes the post data. And of course, neither I nor any of the developers on my team can reproduce the problem. Flash is involved in the process, as I'm using a library called Uploadify to display a progress meter. Here is the flow...does anyone have ANY ideas at all why some of the post data would be getting wiped out? User visits edit screen for a page in the CMS I am using. Record id for the page is put into a form as a hidden value. User clicks the Uploadify browse button and selects a file (only single file selection is allowed). User clicks Submit button for my form. jQuery intercepts the form submit action, triggers Uploadify to start uploading, and returns false for the submit action (manually cancelling the form submit event so that Uploadify can take over). Uploadify uploads to a custom process script. Uploadify finishes uploading and triggers the Javascript completion callback. The Javascript callback calls $('#myForm').submit() to submit the form. This happens on multiple browsers (Firefox 3.5, 3.6, Safari, Internet Explorer 7, 8) and multiple platforms (Mac OS 10.5, 10.6 and Windows XP, 7).

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• My first .net web app - should I go straight to MVC framework (c.f. ASP.net)

  - by Greg

  Hi, I'm done some WinForms work in C# but now moving to have to develop a web application front end in .NET (C#). I have experience developing web apps in Ruby on Rails (& a little with Java with JSP pages & struts mvc). Should I jump straight to MVC framework? (as opposed to going ASP.net) That is from the point of view of future direction for Microsoft & as well ease in ramping up from myself. Or if you like, given my experience to date, what would the pros/cons for me re MVC versus ASP.net? thanks

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