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• Best Practices for Handing over Legacy Code

  - by PersonalNexus

  In a couple of months a colleague will be moving on to a new project and I will be inheriting one of his projects. To prepare, I have already ordered Michael Feathers' Working Effectively with Legacy Code. But this books as well as most questions on legacy code I found so far are concerned with the case of inheriting code as-is. But in this case I actually have access to the original developer and we do have some time for an orderly hand-over. Some background on the piece of code I will be inheriting: It's functioning: There are no known bugs, but as performance requirements keep going up, some optimizations will become necessary in the not too distant future. Undocumented: There is pretty much zero documentation at the method and class level. What the code is supposed to do at a higher level, though, is well-understood, because I have been writing against its API (as a black-box) for years. Only higher-level integration tests: There are only integration tests testing proper interaction with other components via the API (again, black-box). Very low-level, optimized for speed: Because this code is central to an entire system of applications, a lot of it has been optimized several times over the years and is extremely low-level (one part has its own memory manager for certain structs/records). Concurrent and lock-free: While I am very familiar with concurrent and lock-free programming and have actually contributed a few pieces to this code, this adds another layer of complexity. Large codebase: This particular project is more than ten thousand lines of code, so there is no way I will be able to have everything explained to me. Written in Delphi: I'm just going to put this out there, although I don't believe the language to be germane to the question, as I believe this type of problem to be language-agnostic. I was wondering how the time until his departure would best be spent. Here are a couple of ideas: Get everything to build on my machine: Even though everything should be checked into source code control, who hasn't forgotten to check in a file once in a while, so this should probably be the first order of business. More tests: While I would like more class-level unit tests so that when I will be making changes, any bugs I introduce can be caught early on, the code as it is now is not testable (huge classes, long methods, too many mutual dependencies). What to document: I think for starters it would be best to focus documentation on those areas in the code that would otherwise be difficult to understand e.g. because of their low-level/highly optimized nature. I am afraid there are a couple of things in there that might look ugly and in need of refactoring/rewriting, but are actually optimizations that have been out in there for a good reason that I might miss (cf. Joel Spolsky, Things You Should Never Do, Part I) How to document: I think some class diagrams of the architecture and sequence diagrams of critical functions accompanied by some prose would be best. Who to document: I was wondering what would be better, to have him write the documentation or have him explain it to me, so I can write the documentation. I am afraid, that things that are obvious to him but not me would otherwise not be covered properly. Refactoring using pair-programming: This might not be possible to do due to time constraints, but maybe I could refactor some of his code to make it more maintainable while he was still around to provide input on why things are the way they are. Please comment on and add to this. Since there isn't enough time to do all of this, I am particularly interested in how you would prioritize.

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• How to convert my backup.cmd into something I can run in Linux?

  - by blade19899

  Back in the day when i was using windows(and a noob at everything IT) i liked batch scripting so much that i wrote a lot of them and one i am pretty proud of that is my backup.cmd(see below). I am pretty basic with the linux bash sudo/apt-get/sl/ls/locate/updatedb/etc... I don't really know the full power of the terminal. If you see the code below can i get it to work under (Ubuntu)linux :) by rewriting some of the windows code with the linux equivalent (btw:this works under xp/vista/7 | dutch/english) @echo off title back it up :home cls echo ÉÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍ» echo º º echo º typ A/B for the options º echo º º echo ÌÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍ͹ echo º º echo º "A"=backup options º echo º º echo º "B"=HARDDISK Options º echo º º echo º º echo ÈÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍŒ set /p selection=Choose: Goto %selection% :A cls echo ÉÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍ» echo º º echo º typ 1 to start that backup º echo º º echo ÌÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍ͹ echo º º echo º "A"=backup options º echo º È1=Documents,Pictures,Music,Videos,Downloads º echo º º echo º "B"=HARDDISK Options º echo º º echo ÈÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍŒ set /p selection=Choose: Goto %selection% :B cls echo ÉÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍ» echo º º echo º typ HD to start the disk check º echo º º echo ÌÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍ͹ echo º º echo º "A"=backup options º echo º º echo º "B"=HARDDISK Options º echo º ÈHD=find and repair bad sectors º echo º º echo ÈÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍŒ set /p selection=Choose: Goto %selection% :1 cls if exist "%userprofile%\desktop" (set desk=desktop) else (set desk=Bureaublad) if exist "%userprofile%\documents" (set docs=documents) else (set docs=mijn documenten) if exist "%userprofile%\pictures" (set pics=pictures) else (echo cant find %userprofile%\pictures) if exist "%userprofile%\music" (set mus=music) else (echo cant find %userprofile%\music) if exist "%userprofile%\Videos" (set vids=videos) else (echo cant find %userprofile%\videos) if exist "%userprofile%\Downloads" (set down=downloads) else (echo cant find %userprofile%\Downloads) cls echo. examples (D:\) (D:\Backup) (D:\Backup\18-4-2011) echo. echo. if there is no "D:\backup" folder then the folder will be created echo. set drive= set /p drive=storage: echo start>>backup.log echo Name:%username%>>backup.log echo Date:%date%>>backup.log echo Time:%time%>>backup.log echo ========================================%docs%===========================================>>backup.log echo %docs% echo Source:"%userprofile%\%docs%" echo Destination:"%drive%\%username%\%docs%" echo %time%>>backup.log xcopy "%userprofile%\%docs%" "%drive%\%username%\%docs%" /E /I>>Backup.log echo 20%% cls echo ========================================"%pics%"=========================================>>backup.log echo "%pics%" echo Source:"%userprofile%\%pics%" echo Destination:"%drive%\%username%\%pics%" echo %time%>>backup.log xcopy "%userprofile%\%pics%" "%drive%\%username%\%pics%" /E /I>>Backup.log echo 40%% cls echo ========================================"%mus%"=========================================>>backup.log echo "%mus%" echo Source:"%userprofile%\%mus%" echo Destination:"%drive%\%username%\%mus%" echo %time%>>backup.log xcopy "%userprofile%\%mus%" "%drive%\%username%\%mus%" /E /I>>Backup.log echo 60%% cls echo ========================================"%vids%"========================================>>backup.log echo %vids% echo Source:"%userprofile%\%vids%" echo Destination:"%drive%\%username%\%vids%" echo %time%>>backup.log xcopy "%userprofile%\%vids%" "%drive%\%username%\%vids%" /E /I>>Backup.log echo 80%% cls echo ========================================"%down%"========================================>>backup.log echo "%down%" echo Source:"%userprofile%\%down%" echo Destination:"%drive%\%username%\%down%" echo %time%>>backup.log xcopy "%userprofile%\%down%" "%drive%\%username%\%down%" /E /I>>Backup.log echo end>>backup.log echo %username% %date% %time%>>backup.log echo 100%% cls echo backup Compleet copy "backup.log" "%drive%\%username%" del "backup.log" pushd "%drive%\%username%" echo close backup.log to continue with backup script "backup.log" echo press any key to retun to the main menu pause>nul goto :home :HD echo finds and repairs bad sectors echo typ in harddisk letter (C: D: E:) set HD= set /p HD=Hard Disk: chkdsk %HD% /F /R /X pause goto :home

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• Thoughts on Thoughts on TDD

  Brian Harry wrote a post entitled Thoughts on TDD that I thought I was going to let lie, but I find that I need to write a response. I find myself in agreement with Brian on many points in the post, but I disagree with his conclusion. Not surprisingly, I agree with the things that he likes about TDD. Focusing on the usage rather than the implementation is really important, and this is important whether you use TDD or not. And YAGNI was a big theme in my Seven Deadly Sins of Programming series. Now, on to what he doesnt like. He says that he finds it inefficient to have tests that he has to change every time he refactors. Here is where we part company. If you are having to do a lot of test rewriting (say, more than a couple of minutes work to get back to green) *often* when you are refactoring your code, I submit that either you are testing things that you dont need to test (internal details rather than external implementation), your code perhaps isnt as decoupled as it could be, or maybe you need a visit to refactorers anonymous. I also like to refactor like crazy, but as we all know, the huge downside of refactoring is that we often break things. Important things. Subtle things. Which makes refactoring risky. *Unless* we have a set of tests that have great coverage. And TDD (or Example-based Design, which I prefer as a term) gives those to us. Now, I dont know what sort of coverage Brian gets with the unit tests that he writes, but I do know that for the majority of the developers Ive worked with and I count myself in that bucket the coverage of unit tests written afterwards is considerably inferior to the coverage of unit tests that come from TDD. For me, it all comes down to the answer to the following question: How do you ensure that your code works now and will continue to work in the future? Im willing to put up with a little efficiency on the front side to get that benefit later. Its not the writing of the code thats the expensive part, its everything else that comes after. I dont think that stepping through test cases in the debugger gets you what you want. You can verify what the current behavior is, sure, and do it fairly cheaply, but you dont help the guy in the future who doesnt know what conditions were important if he has to change your code. His second part that he doesnt like backing into an architecture (go read to see what he means). Ive certainly had to work with code that was like this before, and its a nightmare the code that nobody wants to touch. But thats not at all the kind of code that you get with TDD, because if youre doing it right youre doing the write a failing tests, make it pass, refactor approach. Now, you may miss some useful refactorings and generalizations for this, but if you do, you can refactor later because you have the tests that make it safe to do so, and your code tends to be easy to refactor because the same things that make code easy to write unit tests for make it easy to refactor. I also think Brian is missing an important point. We arent all as smart as he is. Im reminded a bit of the lesson of Intentional Programming, Charles Simonyis paradigm for making programming easier. I played around with Intentional Programming when it was young, and came to the conclusion that it was a pretty good thing if you were as smart as Simonyi is, but it was pretty much a disaster if you were an average developer. In this case, TDD gives you a way to work your way into a good, flexible, and functional architecture when you dont have somebody of Brians talents to help you out. And thats a good thing.Did you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.

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• Do we still have a case against the goto statement? [closed]

  - by FredOverflow

  Possible Duplicate: Is it ever worthwhile using goto? In a recent article, Andrew Koenig writes: When asked why goto statements are harmful, most programmers will say something like "because they make programs hard to understand." Press harder, and you may well hear something like "I don't really know, but that's what I was taught." For that reason, I'd like to summarize Dijkstra's arguments. He then shows two program fragments, one without a goto and and one with a goto: if (n < 0) n = 0; Assuming that n is a variable of a built-in numeric type, we know that after this code, n is nonnegative. Suppose we rewrite this fragment: if (n >= 0) goto nonneg; n = 0; nonneg: ; In theory, this rewrite should have the same effect as the original. However, rewriting has changed something important: It has opened the possibility of transferring control to nonneg from anywhere else in the program. I emphasized the part that I don't agree with. Modern languages like C++ do not allow goto to transfer control arbitrarily. Here are two examples: You cannot jump to a label that is defined in a different function. You cannot jump over a variable initialization. Now consider composing your code of tiny functions that adhere to the single responsibility principle: int clamp_to_zero(int n) { if (n >= 0) goto n_is_not_negative: n = 0; n_is_not_negative: return n; } The classic argument against the goto statement is that control could have transferred from anywhere inside your program to the label n_is_not_negative, but this simply is not (and was never) true in C++. If you try it, you will get a compiler error, because labels are scoped. The rest of the program doesn't even see the name n_is_not_negative, so it's just not possible to jump there. This is a static guarantee! Now, I'm not saying that this version is better then the one without the goto, but to make the latter as expressive as the first one, we would at least have to insert a comment, or even better yet, an assertion: int clamp_to_zero(int n) { if (n < 0) n = 0; // n is not negative at this point assert(n >= 0); return n; } Note that you basically get the assertion for free in the goto version, because the condition n >= 0 is already written in line 1, and n = 0; satisfies the condition trivially. But that's just a random observation. It seems to me that "don't use gotos!" is one of those dogmas like "don't use multiple returns!" that stem from a time where the real problem were functions of hundreds or even thousand of lines of code. So, do we still have a case against the goto statement, other than that it is not particularly useful? I haven't written a goto in at least a decade, but it's not like I was running away in terror whenever I encountered one. 1 Ideally, I would like to see a strong and valid argument against gotos that still holds when you adhere to established programming principles for clean code like the SRP. "You can jump anywhere" is not (and has never been) a valid argument in C++, and somehow I don't like teaching stuff that is not true. 1: Also, I have never been able to resurrect even a single velociraptor, no matter how many gotos I tried :(

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• Access Denied

  - by Tony Davis

  When Microsoft executives wake up in the night screaming, I suspect they are having a nightmare about their own version of Frankenstein's monster. Created with the best of intentions, without thinking too hard of the long-term strategy, and having long outlived its usefulness, the monster still lives on, occasionally wreaking vengeance on the innocent. Its name is Access; a living synthesis of disparate body parts that is resistant to all attempts at a mercy-killing. In 1986, Microsoft had no database products, and needed one for their new OS/2 operating system, the successor to MSDOS. In 1986, they bought exclusive rights to Sybase DataServer, and were also intent on developing a desktop database to capture Ashton-Tate's dominance of that market, with dbase. This project, first called 'Omega' and later 'Cirrus', eventually spawned two products: Visual Basic in 1991 and Access in late 1992. Whereas Visual Basic battled with PowerBuilder for dominance in the client-server market, Access easily won the desktop database battle, with Dbase III and DataEase falling away. Access did an excellent job of abstracting and simplifying the task of building small database applications in a short amount of time, for a small number of departmental users, and often for a transient requirement. There is an excellent front end and forms generator. We not only see it in Access but parts of it also reappear in SSMS. It's good. A business user can pull together useful reports, without relying on extensive technical support. A skilled Access programmer can deliver a fairly sophisticated application, whilst the traditional client-server programmer is still sharpening his pencil. Even for the SQL Server programmer, the forms generator of Access is useful for sketching out application designs. So far, so good, but here's where the problems start; Access ties together two different products and the backend of Access is the bugbear. The limitations of Jet/ACE are well-known and documented. They range from MDB files that are prone to corruption, especially as they grow in size, pathetic security, and "copy and paste" Backups. The biggest problem though, was an infamous lack of scalability. Because Microsoft never realized how long the product would last, they put little energy into improving the beast. Microsoft 'ate their own dog food' by using Access for Microsoft Exchange and Outlook. They choked on it. For years, scalability and performance problems with Exchange Server have been laid at the door of the Jet Blue engine on which it relies. Substantial development work in Exchange 2010 was required, just in order to improve the engine and storage schema so that it more efficiently handled the reading and writing of mails. The alternative of using SQL Server just never panned out. The Jet engine was designed to limit concurrent users to a small number (10-20). When Access applications outgrew this, bitter experience proved that there really is no easy upgrade path from Access to SQL Server, beyond rewriting the whole lot from scratch. The various initiatives to do this never quite bridged the cultural gulf between Access and a true relational database So, what are the obvious alternatives for small, strategic database applications? I know many users who, for simple 'list maintenance' requirements are very happy using Excel databases. Surely, now that PowerPivot has led the way, it is time for Microsoft to offer a new RAD package for database application development; namely an Excel-based front end for SQL Server Express. In that way, we'll have a powerful and familiar front end, to a scalable database, and a clear upgrade path when an app takes off and needs to go enterprise. Cheers, Tony.

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• Best Practices - Core allocation

  - by jsavit

  This post is one of a series of "best practices" notes for Oracle VM Server for SPARC (also called Logical Domains) Introduction SPARC T-series servers currently have up to 4 CPU sockets, each of which has up to 8 or (on SPARC T3) 16 CPU cores, while each CPU core has 8 threads, for a maximum of 512 dispatchable CPUs. The defining feature of Oracle VM Server for SPARC is that each domain is assigned CPU threads or cores for its exclusive use. This avoids the overhead of software-based time-slicing and emulation (or binary rewriting) of system state-changing privileged instructions used in traditional hypervisors. To create a domain, administrators specify either the number of CPU threads or cores that the domain will own, as well as its memory and I/O resources. When CPU resources are assigned at the individual thread level, the logical domains constraint manager attempts to assign threads from the same cores to a domain, and avoid "split core" situations where the same CPU core is used by multiple domains. Sometimes this is unavoidable, especially when domains are allocated and deallocated CPUs in small increments. Why split cores can matter Split core allocations can silenty reduce performance because multiple domains with different address spaces and memory contents are sharing the core's Level 1 cache (L1$). This is called false cache sharing since even identical memory addresses from different domains must point to different locations in RAM. The effect of this is increased contention for the cache, and higher memory latency for each domain using that core. The degree of performance impact can be widely variable. For applications with very small memory working sets, and with I/O bound or low-CPU utilization workloads, it may not matter at all: all machines wait for work at the same speed. If the domains have substantial workloads, or are critical to performance then this can have an important impact: This blog entry was inspired by a customer issue in which one CPU core was split among 3 domains, one of which was the control and service domain. The reported problem was increased I/O latency in guest domains, but the root cause might be higher latency servicing the I/O requests due to the control domain being slowed down. What to do about it Split core situations are easily avoided. In most cases the logical domain constraint manager will avoid it without any administrative action, but it can be entirely prevented by doing one of the several actions: Assign virtual CPUs in multiples of 8 - the number of threads per core. For example: ldm set-vcpu 8 mydomain or ldm add-vcpu 24 mydomain. Each domain will then be allocated on a core boundary. Use the whole core constraint when assigning CPU resources. This allocates CPUs in increments of entire cores instead of virtual CPU threads. The equivalent of the above commands would be ldm set-core 1 mydomain or ldm add-core 3 mydomain. Older syntax does the same thing by adding the -c flag to the add-vcpu, rm-vcpu and set-vcpu commands, but the new syntax is recommended. When whole core allocation is used an attempt to add cores to a domain fails if there aren't enough completely empty cores to satisfy the request. See https://blogs.oracle.com/sharakan/entry/oracle_vm_server_for_sparc4 for an excellent article on this topic by Eric Sharakan. Don't obsess: - if the workloads have minimal CPU requirements and don't need anywhere near a full CPU core, then don't worry about it. If you have low utilization workloads being consolidated from older machines onto a current T-series, then there's no need to worry about this or to assign an entire core to domains that will never use that much capacity. In any case, make sure the most important domains have their own CPU cores, in particular the control domain and any I/O or service domain, and of course any important guests. Summary Split core CPU allocation to domains can potentially have an impact on performance, but the logical domains manager tends to prevent this situation, and it can be completely and simply avoided by allocating virtual CPUs on core boundaries.

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• Too complex/too many objects?

  - by Mike Fairhurst

  I know that this will be a difficult question to answer without context, but hopefully there are at least some good guidelines to share on this. The questions are at the bottom if you want to skip the details. Most are about OOP in general. Begin context. I am a jr dev on a PHP application, and in general the devs I work with consider themselves to use many more OO concepts than most PHP devs. Still, in my research on clean code I have read about so many ways of using OO features to make code flexible, powerful, expressive, testable, etc. that is just plain not in use here. The current strongly OO API that I've proposed is being called too complex, even though it is trivial to implement. The problem I'm solving is that our permission checks are done via a message object (my API, they wanted to use arrays of constants) and the message object does not hold the validation object accountable for checking all provided data. Metaphorically, if your perm containing 'allowable' and 'rare but disallowed' is sent into a validator, the validator may not know to look for 'rare but disallowed', but approve 'allowable', which will actually approve the whole perm check. We have like 11 validators, too many to easily track at such minute detail. So I proposed an AtomicPermission class. To fix the previous example, the perm would instead contain two atomic permissions, one wrapping 'allowable' and the other wrapping 'rare but disallowed'. Where previously the validator would say 'the check is OK because it contains allowable,' now it would instead say '"allowable" is ok', at which point the check ends...and the check fails, because 'rare but disallowed' was not specifically okay-ed. The implementation is just 4 trivial objects, and rewriting a 10 line function into a 15 line function. abstract class PermissionAtom { public function allow(); // maybe deny() as well public function wasAllowed(); } class PermissionField extends PermissionAtom { public function getName(); public function getValue(); } class PermissionIdentifier extends PermissionAtom { public function getIdentifier(); } class PermissionAction extends PermissionAtom { public function getType(); } They say that this is 'not going to get us anything important' and it is 'too complex' and 'will be difficult for new developers to pick up.' I respectfully disagree, and there I end my context to begin the broader questions. So the question is about my OOP, are there any guidelines I should know: is this too complicated/too much OOP? Not that I expect to get more than 'it depends, I'd have to see if...' when is OO abstraction too much? when is OO abstraction too little? how can I determine when I am overthinking a problem vs fixing one? how can I determine when I am adding bad code to a bad project? how can I pitch these APIs? I feel the other devs would just rather say 'its too complicated' than ask 'can you explain it?' whenever I suggest a new class.

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• How can I centralise MySQL data between 3 or more geographically separate servers?

  - by Andy Castles

  To explain the background to the question: We have a home-grown PHP application (for running online language-learning courses) running on a Linux server and using MySQL on localhost for saving user data (e.g. results of tests taken, marks of submitted work, time spent on different pages in the courses, etc). As we have students from different geographic locations we currently have 3 virtual servers hosted close to those locations (Spain, UK and Hong Kong) and users are added to the server closest to them (they access via different URLs, e.g. europe.domain.com, uk.domain.com and asia.domain.com). This works but is an administrative nightmare as we have to remember which server a particular user is on, and users can only connect to one server. We would like to somehow centralise the information so that all users are visible on any of the servers and users could connect to any of the 3 servers. The question is, what method should we use to implement this. It must be an issue that that lots of people have encountered but I haven't found anything conclusive after a fair bit of Googling around. The closest I have seen to solutions are: something like master-master replication, but I have read so many posts suggesting that this is not a good idea as things like auto_increment fields can break. circular replication, this sounded perfect but to quote from O'Reilly's High Performance MySQL, "In general, rings are brittle and best avoided" We're not against rewriting code in the application to make it work with whatever solution is required but I am not sure if replication is the correct thing to use. Thanks, Andy P.S. I should add that we experimented with writes to a central database and then using reads from a local database but the response time between the different servers for writing was pretty bad and it's also important that written data is available immediately for reading so if replication is too slow this could cause out-of-date data to be returned. Edit: I have been thinking about writing my own rudimentary replication script which would involve something like having each user given a server ID to say which is his "home server", e.g. users in asia would be marked as having the Hong Kong server as their own server. Then the replication scripts (which would be a PHP script set to run as a cron job reasonably frequently, e.g. every 15 minutes or so) would run independently on each of the servers in the system. They would go through the database and distribute any information about users with the "home server" set to the server that the script is running on to all of the other databases in the system. They would also need to suck new information which has been added to any of the other databases on the system where the "home server" flag is the server where the script is running. I would need to work out the details and build in the logic to deal with conflicts but I think it would be possible, however I wanted to make sure that there is not a correct solution for this already out there as it seems like it must be a problem that many people have already come across.

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• Fix/Bypass "Cannot connect to the real website-blocked" error in Google Chrome with OpenDNS blocking

  - by George H

  I have a large problem with Chrome in my organisation. I use DNS to manage web site blocking, for sites which are not appropriate and are potentially a risk to the organisation where I do this. I only want to use Chrome over the network, as Internet Explorer has compatibility problems with some sites that we use (We cannot change this either or use different sites). Therefore using internet explorer is not a solution. I do not want to install a different browser, for multiple reasons. Mainly because of the difficulty of rewriting the customised add-ons that we use. However, recently, I have had lots of problems with Chrome SSL Errors. I cannot use my custom OpenDNS block pages, which uses the contact form to request an unblocking. Chrome often blocks OpenDNS for sites (a good example is Facebook) that request HTTPS. Some sites like https://internetbadguys.com (OpenDNS example) This means that chrome refuses to load the blocking page, explaining that the site is blocked. Instead they often call IT support, but they want a solution, as they are sick of getting lots of SSL errors. I have tried looking into ways to turning this off. I have tried: Typing "proceed". That didn't work. Typing "proceed", pressing enter. Didn't work I cannot find phishing and anti-malware any more in Chrome, from the internet guides. Not using HTTPS. However there is an automatic redirect to HTTPS on most sites. Therefore the error keeps coming up. Checking my clocks. They were correct. Does anyone have an idea on how to disabling, bypassing or working around this "feature"? EDIT: This is an example what I am talking about - I found that on google images. I do not block google. EDIT 2: My clocks are correct. I cannot stop using OpenDNS either. EDIT 3: My question is: How do I stop chrome from refusing to load pages that are blocked by OpenDNS, where the server has explicitly requested HTTPS.

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• Postfix: How to apply header_checks only for specific Domains?

  - by Lukas

  Basically what I want to do is rewriting the From: Header, using header_checks, but only if the mail goes to a certain domain. The problem with header_check is, that I can't check for a combination of To: and From: Headers. Now I was wondering if it was possible to use the header_checks in combination with smtpd_restriction_classes or something similar. I've found a lot information about header_checks and multiple header fields, when searching the net. All of them basically telling me, that one can't combine two header for checking. But I didn't find any information if it was possible to only do a header check if a condition (eg. mail goes to example.com) was met. Edit: While doing some more Research I've found the following article which suggests to add a Service in postfix master.cf, use a transportmap to pass mails for the Domain to that service and have a separate header_check defined with -o. The thing is that I can't get it to work... What I did so far is adding the Service to the master.cf: example unix - - n - - smtpd -o header_checks=regexp:/etc/postfix/check_headers_example Adding the followin Line to the transportmap: example.com example: Last but not least I have two regexp-files for header checks, one for the newly added service, and one to redirect answers to the rewritten domain. check_headers_example: /From:(.*)@mydomain.ain>(.*)/ REPLACE From:[email protected]>$2 Obviously if someone answers, the mail would go to nirvana, so I have the following check_headers defined in the main postfix process: /To:(.*)<(.*)@mydomain.example.com>(.*)/ REDIRECT [email protected]$2 Somehow the Transport is ignored. Any help is appreciated. Edit 2: I'm still stuck... I did try the following: smtpd_restriction_classes = header_rewrite header_rewrite = regexp:/etc/postfix/rewrite_headers_domain smtpd_recipient_restrictions = (some checks) check_recipient_access hash:/etc/postfix/rewrite_table, (more checks) In the rewrite_table the following entries exist: /From:(.*)@mydomain.ain>(.*)/ REPLACE From:[email protected]>$2 All it gets me is a NOQUEUE: reject: 451 4.3.5 Server configuration error. I couldn't find any resources on how you would do that but some people saying it wasn't possible. Edit 3: The reason I asked this question was, that we have a customer (lets say customer.com) who uses some aliases that will forward mail to a domain, let's say example.com. The mailserver at example.com does not accept any mail from an external server that come from a sender @example.com. So all mails that are written from example.com to [email protected] will be rejected in the end. An exception on example.com's mailserver is not possible. We didn't really solve this problem, but will try to work around it by using lists (mailman) instead of aliases. This is not really nice though, nor a real solution. I'd appreciate all suggestions how this could be done in a proper way.

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• Why isn't this rewrite rule (nginx) applied? (trying to setup Wordpress multisite)

  - by Brian Park

  Hi, I'm trying to setup Wordpress multisite (subfolder structure) with nginx, but having a problem with this rewrite rule. Below is the Apache's .htaccess, which I have to translate into nginx configuration. RewriteEngine On RewriteBase /blogs/ RewriteRule ^index\.php$ - [L] # uploaded files RewriteRule ^([_0-9a-zA-Z-]+/)?files/(.+) wp-includes/ms-files.php?file=$2 [L] # add a trailing slash to /wp-admin RewriteRule ^([_0-9a-zA-Z-]+/)?wp-admin$ $1wp-admin/ [R=301,L] RewriteCond %{REQUEST_FILENAME} -f [OR] RewriteCond %{REQUEST_FILENAME} -d RewriteRule ^ - [L] RewriteRule ^([_0-9a-zA-Z-]+/)?(wp-(content|admin|includes).*) $2 [L] RewriteRule ^([_0-9a-zA-Z-]+/)?(.*\.php)$ $2 [L] RewriteRule . index.php [L] Below is what I came up with: server { listen 80; server_name example.com; server_name_in_redirect off; expires 1d; access_log /srv/www/example.com/logs/access.log; error_log /srv/www/example.com/logs/error.log; root /srv/www/example.com/public; index index.html; try_files $uri $uri/ /index.html; # rewriting uploaded files rewrite ^/blogs/(.+/)?files/(.+) /blogs/wp-includes/ms-files.php?file=$2 last; # add a trailing slash to /wp-admin rewrite ^/blogs/(.+/)?wp-admin$ /blogs/$1wp-admin/ permanent; if (!-e $request_filename) { rewrite ^/blogs/(.+/)?(wp-(content|admin|includes).*) /blogs/$2 last; rewrite ^/blogs/(.+/)?(.*\.php)$ /blogs/$2 last; } location /blogs/ { index index.php; #try_files $uri $uri/ /blogs/index.php?q=$uri&$args; } location ~ \.php$ { include /etc/nginx/fastcgi_params; fastcgi_pass 127.0.0.1:9000; fastcgi_index index.php; fastcgi_param SCRIPT_FILENAME /srv/www/example.com/public$fastcgi_script_name; } # static assets location ~* ^.+\.(manifest)$ { access_log /srv/www/example.com/logs/static.log; } location ~* ^.+\.(ico|ogg|ogv|svg|svgz|eot|otf|woff|mp4|ttf|css|rss|atom|js|jpg|jpeg|gif|png|ico|zip|tgz|gz|rar|bz2|doc|xls|exe|ppt|tar|mid|midi|wav|bmp|rtf)$ { # only set expires max IFF the file is a static file and exists if (-f $request_filename) { expires max; access_log /srv/www/example.com/logs/static.log; } } } In the above code, I believe rewrite ^/blogs/(.+/)?(.*\.php)$ /blogs/$2 last; has no effect because when I look at the access_log file, I see the following line: 2010/09/15 01:14:55 [error] 10166#0: *8 "/srv/www/example.com/public/blogs/test/index.php" is not found (2: No such file or directory), request: "GET /blogs/test/ HTTP/1.1" (Here, 'test' is the second blog created using multisite feature) What I'm expecting is that /blogs/test/index.php gets rewritten to /blogs/index.php, but it doesn't seem to do that... Am I overlooking something obvious? Thanks!

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• Operative systems on SD cards

  - by HisDudeness

  I was getting some wild ideas the last days, like putting some operative systems into SD cards rather than on my hard drive. I'll go further into details now and explain what lead me to consider this probably abominable decision. I am on a laptop (that means I have a native SD-card reader) which is currently running a cross-distro setup, with a bunch of Linux systems (placed in dedicated ext4 logical partitions into a huge extended one) regulated by an unique GRUB. Since today, my laptop haven't even seen any Windows system with binoculars. I was thinking about placing all the os part of my setup into a Secure Digital to save all my 500 Gb Hard Drive for documents, music, videos and so on, and being able to just remove the SD and boot my system into another computer too, as well as having the possibility of booting other systems into mine by just plugging in another SD, without having to keep it constantly placed in my PC. Also, in the remote case in the near future I just wanted to boot Windows 8 in it, I read it causes major boot incompatibility issues with other systems by needing a digital signature in order for them to start. By having it in a removable drive, I could just get rid of it when I'm needing him and switch its card with Linux one, and so not having any obstacles to their boot. Now, my questions are: I know unlikely traditional rotating disk drives, integrated circuits ones have a limited lifespan in terms of cluster rewriting. Is it an obstacle to that kind of usage? I mean, some Ultrabooks are using SSD now, is it the same issue, or there are some differences between Solid State Drives and Secure Digitals in that sense? Maybe having them to store system files which are in fixed positions (making the even-usage of cluster technology useless) constantly being re-read and updated and similar things just gets them soon unserviceable, do it? Second question: are all motherboards and BIOSes able to boot from SDs just like they are from USB pen drives (I mean, provided card reader is USB-connected, isn't it)? Or can't bootloaders like GRUB be installed on SDs working? If they can't, is it a solution installing GRUB to MBR and making boot option pointing to SD? Will it work? Are there any other problems to installing OSs on a Secure Digital?

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• Squid on windows loadbalancing only to one server

  - by Martin L.

  After thousands of googles and trying days i cant get the load balancer/failover in squid on windows to work. Iam using squid 2.7. My webservers are 2 single NIC lighttpd and one dual nic lighttpd. server1 in this example is running squid on port 80 and lighttpd on port 8080 (just to test) Requirements: All 3 webservers running lighttpd should be balanced two option for load balancing: Best would be if server1 is busy server2 takes over, if server2 is busy server3 takes over, etc.. Round robin style evenly distributed load. Eg server1 takes first call, server2 second etc.. All requests should be treated the same way (no url rewriting or so on) Sent host headers have to be redirected to every server as http host header, speaking of "server1", "server1.company.internal" and "10.211.1.1". My approach: acl all src all acl manager proto cache_object http_port 80 accel defaultsite=server1.company.internal vhost #reverse proxy entries cache_peer 10.211.2.1 parent 8080 0 no-query originserver round-robin login=PASS name=server1_nic1 cache_peer 10.211.1.2 parent 80 0 no-query originserver round-robin login=PASS name=server2_nic1 cache_peer 10.211.2.3 parent 8080 0 no-query originserver round-robin login=PASS name=server3_nic1 cache_peer 10.211.2.4 parent 8080 0 no-query originserver round-robin login=PASS name=server3_nic2 #decl of names of squid host acl registered_name_hostdomain dstdomain server1.company.internal acl registered_name_host dstdomain server1 #ip of squid host acl registered_name_ip dstdomain 10.211.2.1 # access: redirects the correct squid hostname http_access allow registered_name_hostdomain http_access allow registered_name_host http_access allow registered_name_ip http_access deny all cache_peer_access server1_nic1 allow registered_name_hostdomain cache_peer_access server1_nic1 allow registered_name_host cache_peer_access server1_nic1 allow registered_name_ip cache_peer_access server2_nic1 allow registered_name_hostdomain cache_peer_access server2_nic1 allow registered_name_host cache_peer_access server2_nic1 allow registered_name_ip cache_peer_access server3_nic1 allow registered_name_hostdomain cache_peer_access server3_nic1 allow registered_name_host cache_peer_access server3_nic1 allow registered_name_ip cache_peer_access server3_nic2 allow registered_name_hostdomain cache_peer_access server3_nic2 allow registered_name_host cache_peer_access server3_nic2 allow registered_name_ip cache_peer_access server1_nic1 deny all cache_peer_access server2_nic1 deny all cache_peer_access server3_nic1 deny all cache_peer_access server3_nic2 deny all never_direct allow all Problems: Load balancer does not load balance other than to first server. Only if the first server is killed in any way the second will take over. I have seen the others working at some point, but definitely not as the intended load balancing described above. If the cache_peer_access is not defined sometimes the wrong hostname is sent to the backend webserver and this always depends on the defaultsite= parameter. Probably because the host header on the request to squid is not set and its replaced by defaultsite. Leaving out defaultsite didnt solve the problem. The only workaround i found for this is the current approach with cache_peer_access. Questions: Does the cache_peer_access influence the round-robin? Is there a better workaround to pass the host header to the backed webservers? Which parameters do increase the speed of load balancing or does anyone have a better approach? -Martin

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• only removing index.php rule works on my NginX and CodeIgniter as rewrite. Why?

  - by Atomei Cosmin

  I am very new in rewriting in nginx but although I've spent 2 days reading on forums, I still can't get some Codeigniter rewrites working ... server { listen *:80; server_name artademy.com www.artademy.com; root /var/www/artademy.com/web; index index.html index.htm index.php index.cgi index.pl index.xhtml; if (!-e $request_filename) { rewrite ^/(.*)$ /index.php?/$1; } if (!-e $request_filename) { rewrite ^/(index.php\?)/(.*)$ /$1/mobile_app last; break; } error_log /var/log/ispconfig/httpd/artademy.com/error.log; access_log /var/log/ispconfig/httpd/artademy.com/access.log combined; ## Disable .htaccess and other hidden files location ~ /\. { deny all; access_log off; log_not_found off; } location = /favicon.ico { log_not_found off; access_log off; } location = /robots.txt { allow all; log_not_found off; access_log off; } location /stats { index index.html index.php; auth_basic "Members Only"; auth_basic_user_file /var/www/clients/client0/web3/.htpasswd_stats; } location ^~ /awstats-icon { alias /usr/share/awstats/icon; } location ~ \.php$ { try_files $uri =404; include /etc/nginx/fastcgi_params; fastcgi_pass 127.0.0.1:9012; fastcgi_index index.php; fastcgi_param SCRIPT_FILENAME $document_root$fastcgi_script_name; fastcgi_param PATH_INFO $fastcgi_script_name; fastcgi_intercept_errors on; } } Codeigniter settings are: well for uri_protocol: REQUEST_URI; What i noticed is that from this rule: rewrite ^/(.)$ /index.php?/$1; it works ever if i write it like this: rewrite ^/(.)$ /index.php?; It might be a wild guess but it stops at the question mark... Anyhow what I need are rules as these from .htaccess: RewriteCond %{REQUEST_FILENAME} !-f RewriteCond %{QUERY_STRING} ^lang=([a-z]{2})$ RewriteRule ^([a-z]{2})$ index.php?/home_page?lang=$1 [L,QSA] RewriteRule ^([a-z]{2})$ index.php?/home_page?lang=$1 [L,QSA] #how_it_works RewriteCond %{REQUEST_FILENAME} !-f RewriteRule ^how-it-works/(en)$ index.php?/how_it_works?lang=en [L,QSA] #order_status RewriteCond %{REQUEST_FILENAME} !-f RewriteRule ^order-status/(en)$ index.php?/order_status?lang=en [L,QSA] Can anyone tell me what i'm doing wrong and show me a proper way for at least one rule? It would be more than helpful. Thank you in advance! ^^ PS: I made it work on apache by using Path_info for uri_protocol.. if this info is of any help, and i remember having kind of the same problem there too but switching to path_info made it all good.

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• Your thoughts on Best Practices for Scientific Computing?

  - by John Smith

  A recent paper by Wilson et al (2014) pointed out 24 Best Practices for scientific programming. It's worth to have a look. I would like to hear opinions about these points from experienced programmers in scientific data analysis. Do you think these advices are helpful and practical? Or are they good only in an ideal world? Wilson G, Aruliah DA, Brown CT, Chue Hong NP, Davis M, Guy RT, Haddock SHD, Huff KD, Mitchell IM, Plumbley MD, Waugh B, White EP, Wilson P (2014) Best Practices for Scientific Computing. PLoS Biol 12:e1001745. http://www.plosbiology.org/article/info%3Adoi%2F10.1371%2Fjournal.pbio.1001745 Box 1. Summary of Best Practices Write programs for people, not computers. (a) A program should not require its readers to hold more than a handful of facts in memory at once. (b) Make names consistent, distinctive, and meaningful. (c) Make code style and formatting consistent. Let the computer do the work. (a) Make the computer repeat tasks. (b) Save recent commands in a file for re-use. (c) Use a build tool to automate workflows. Make incremental changes. (a) Work in small steps with frequent feedback and course correction. (b) Use a version control system. (c) Put everything that has been created manually in version control. Don’t repeat yourself (or others). (a) Every piece of data must have a single authoritative representation in the system. (b) Modularize code rather than copying and pasting. (c) Re-use code instead of rewriting it. Plan for mistakes. (a) Add assertions to programs to check their operation. (b) Use an off-the-shelf unit testing library. (c) Turn bugs into test cases. (d) Use a symbolic debugger. Optimize software only after it works correctly. (a) Use a profiler to identify bottlenecks. (b) Write code in the highest-level language possible. Document design and purpose, not mechanics. (a) Document interfaces and reasons, not implementations. (b) Refactor code in preference to explaining how it works. (c) Embed the documentation for a piece of software in that software. Collaborate. (a) Use pre-merge code reviews. (b) Use pair programming when bringing someone new up to speed and when tackling particularly tricky problems. (c) Use an issue tracking tool. I'm relatively new to serious programming for scientific data analysis. When I tried to write code for pilot analyses of some of my data last year, I encountered tremendous amount of bugs both in my code and data. Bugs and errors had been around me all the time, but this time it was somewhat overwhelming. I managed to crunch the numbers at last, but I thought I couldn't put up with this mess any longer. Some actions must be taken. Without a sophisticated guide like the article above, I started to adopt "defensive style" of programming since then. A book titled "The Art of Readable Code" helped me a lot. I deployed meticulous input validations or assertions for every function, renamed a lot of variables and functions for better readability, and extracted many subroutines as reusable functions. Recently, I introduced Git and SourceTree for version control. At the moment, because my co-workers are much more reluctant about these issues, the collaboration practices (8a,b,c) have not been introduced. Actually, as the authors admitted, because all of these practices take some amount of time and effort to introduce, it may be generally hard to persuade your reluctant collaborators to comply them. I think I'm asking your opinions because I still suffer from many bugs despite all my effort on many of these practices. Bug fix may be, or should be, faster than before, but I couldn't really measure the improvement. Moreover, much of my time has been invested on defence, meaning that I haven't actually done much data analysis (offence) these days. Where is the point I should stop at in terms of productivity? I've already deployed: 1a,b,c, 2a, 3a,b,c, 4b,c, 5a,d, 6a,b, 7a,7b I'm about to have a go at: 5b,c Not yet: 2b,c, 4a, 7c, 8a,b,c (I could not really see the advantage of using GNU make (2c) for my purpose. Could anyone tell me how it helps my work with MATLAB?)

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• Troubleshooting Application Timeouts in SQL Server

  - by Tara Kizer

  I recently received the following email from a blog reader: "We are having an OLTP database instance, using SQL Server 2005 with little to moderate traffic (10-20 requests/min). There are also bulk imports that occur at regular intervals in this DB and the import duration ranges between 10secs to 1 min, depending on the data size. Intermittently (2-3 times in a week), we face an issue, where queries get timed out (default of 30 secs set in application). On analyzing, we found two stored procedures, having queries with multiple table joins inside them of taking a long time (5-10 mins) in getting executed, when ideally the execution duration ranges between 5-10 secs. Execution plan of the same displayed Clustered Index Scan happening instead of Clustered Index Seek. All required Indexes are found to be present and Index fragmentation is also minimal as we Rebuild Indexes regularly alongwith Updating Statistics. With no other alternate options occuring to us, we restarted SQL server and thereafter the performance was back on track. But sometimes it was still giving timeout errors for some hits and so we also restarted IIS and that stopped the problem as of now." Rather than respond directly to the blog reader, I thought it would be more interesting to share my thoughts on this issue in a blog. There are a few things that I can think of that could cause abnormal timeouts: Blocking Bad plan in cache Outdated statistics Hardware bottleneck To determine if blocking is the issue, we can easily run sp_who/sp_who2 or a query directly on sysprocesses (select * from master..sysprocesses where blocking <> 0).  If blocking is present and consistent, then you'll need to determine whether or not to kill the parent blocking process.  Killing a process will cause the transaction to rollback, so you need to proceed with caution.  Killing the parent blocking process is only a temporary solution, so you'll need to do more thorough analysis to figure out why the blocking was present.  You should look into missing indexes and perhaps consider changing the database's isolation level to READ_COMMITTED_SNAPSHOT. The blog reader mentions that the execution plan shows a clustered index scan when a clustered index seek is normal for the stored procedure.  A clustered index scan might have been chosen either because that is what is in cache already or because of out of date statistics.  The blog reader mentions that bulk imports occur at regular intervals, so outdated statistics is definitely something that could cause this issue.  The blog reader may need to update statistics after imports are done if the imports are changing a lot of data (greater than 10%).  If the statistics are good, then the query optimizer might have chosen to scan rather than seek in a previous execution because the scan was determined to be less costly due to the value of an input parameter.  If this parameter value is rare, then its execution plan in cache is what we call a bad plan.  You want the best plan in cache for the most frequent parameter values.  If a bad plan is a recurring problem on your system, then you should consider rewriting the stored procedure.  You might want to break up the code into multiple stored procedures so that each can have a different execution plan in cache. To remove a bad plan from cache, you can recompile the stored procedure.  An alternative method is to run DBCC FREEPROCACHE which drops the procedure cache.  It is better to recompile stored procedures rather than dropping the procedure cache as dropping the procedure cache affects all plans in cache rather than just the ones that were bad, so there will be a temporary performance penalty until the plans are loaded into cache again. To determine if there is a hardware bottleneck occurring such as slow I/O or high CPU utilization, you will need to run Performance Monitor on the database server.  Hopefully you already have a baseline of the server so you know what is normal and what is not.  Be on the lookout for I/O requests taking longer than 12 milliseconds and CPU utilization over 90%.  The servers that I support typically are under 30% CPU utilization, but your baseline could be higher and be within a normal range. If restarting the SQL Server service fixes the problem, then the problem was most likely due to blocking or a bad plan in the procedure cache.  Rather than restarting the SQL Server service, which causes downtime, the blog reader should instead analyze the above mentioned things.  Proceed with caution when restarting the SQL Server service as all transactions that have not completed will be rolled back at startup.  This crash recovery process could take longer than normal if there was a long-running transaction running when the service was stopped.  Until the crash recovery process is completed on the database, it is unavailable to your applications. If restarting IIS fixes the problem, then the problem might not have been inside SQL Server.  Prior to taking this step, you should do analysis of the above mentioned things. If you can think of other reasons why the blog reader is facing this issue a few times a week, I'd love to hear your thoughts via a blog comment.

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• SQLAuthority News – 7th Anniversary of Blog – A Personal Note

  - by Pinal Dave

  Special Day Today is a very special day – seven years ago I blogged for the very first time.  Seven years ago, I didn’t know what I was doing, I didn’t know how to blog, or even what a blog was or what to write.  I was working as a DBA, and I was trying to solve a problem – at my job, there were a few issues I had to fix again and again and again.  There were days when I was rewriting the same solution over and over, and there were times when I would get very frustrated because I could not write the same elegant solution that I had written before.  I came up with a solution to this problem – posting these solutions online, where I could access them whenever I needed them.  At that point, I had no idea what a blog was, or even how the internet worked, I had no idea that a blog would be visible to others.  Can you believe it? Google it on Yahoo! After a few posts on this “blog,” there was a surprise for me – an e-mail saying that someone had left me a comment.  I was surprised, because I didn’t even know you could comment on a blog!  I logged on and read my comment.  It said: “I like your script,but there is a small bug.  If you could fix it, it will run on multiple other versions of SQL Server.”  I was like, “wow, someone figured out how to find my blog, and they figured out how to fix my script!”  I found the bug, I fixed the script, and a wrote a thank you note to the guy.  My first question for him was: how did you figure it out – not the script, but how to find my blog?  He said he found it from Yahoo Search (this was in the time before Google, believe it or not). From that day, my life changed.  I wrote a few more posts, I got a few more comments, and I started to watch my traffic.  People were reading, commenting, and giving feedback.  At the end of the day, people enjoyed what I was writing.  This was a fantastic feeling!  I never thought I would be writing for others.  Even today, I don’t feel like I am writing for others, but that I am simply posting what I am learning every day.  From that very first day, I decided that I would not change my intent or my blog’s purpose. 72 Million Views – 2600 Posts – 57000 comments – 10 books – 9 courses Today, this blog is my habit, my addiction, my baby.  Every day I try to learn something new, and that lesson gets posted on the blog.  Lately there have been days where I am traveling for a full 24 hours, but even on those days I try to learn something new, and later when I have free time, I will still post it to the blog.  Because of this habit, this blog has over 72 millions views, I have written more than 2600 posts, and there are 57,000 comments and counting.  I have also written 10 books, 9 courses, and learned so many things.  This blog has given me back so much more than I ever put it into it.  It gave me an education, a reason to learn something new every day, and a way to connect to people.  I like to think of it as a learning chain, a relay where we all pass knowledge from one to another. Never Ending Journey When I started the blog, I thought I would write for a few days and stop, but now after seven years I haven’t stopped and I have no intention of stopping!  However, change happens, and for this blog it will start today.  This blog started as a single resource for SQL Server, but now it has grown beyond, to Sharepoint, Personal Development, Developer Training, MySQL, Big Data, and lots of other things.  Truly speaking, this blog is more than just SQL Server, and that was always my intention.  I named it “SQL Authority,” not “SQL Server Authority”!  Loudly and clearly, I would like to announce that I am going to go back to my roots and start writing more about SQL, more about big data, and more about the other technology like relational databases, MySQL, Oracle, and others.  My goal is not to become a comprehensive resource for every technology, my goal is to learn something new every day – and now it can be so much more than just SQL Server.  I will learn it, and post it here for you. I have written a very long post on this anniversary, but here is the summary: Thank You.  You all have been wonderful.  Seven years is a long journey, and it makes me emotional.  I have been “with” this blog before I met my wife, before we had our daughter.  This blog is like a fourth member of the family.  Keep reading, keep commenting, keep supporting.  Thank you all. Reference: Pinal Dave (http://blog.sqlauthority.com)Filed under: About Me, MySQL, PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, SQLAuthority News, T SQL

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• Optimizing drawing of cubes

  - by Christian Frantz

  After googling for hours I've come to a few conclusions, I need to either rewrite my whole cube class, or figure out how to use hardware instancing. I can draw up to 2500 cubes with little lag, but after that my fps drops. Is there a way I can use my class for hardware instancing? Or would I be better off rewriting my class for optimization? public class Cube { public GraphicsDevice device; public VertexBuffer cubeVertexBuffer; public Cube(GraphicsDevice graphicsDevice) { device = graphicsDevice; var vertices = new List<VertexPositionTexture>(); BuildFace(vertices, new Vector3(0, 0, 0), new Vector3(0, 1, 1)); BuildFace(vertices, new Vector3(0, 0, 1), new Vector3(1, 1, 1)); BuildFace(vertices, new Vector3(1, 0, 1), new Vector3(1, 1, 0)); BuildFace(vertices, new Vector3(1, 0, 0), new Vector3(0, 1, 0)); BuildFaceHorizontal(vertices, new Vector3(0, 1, 0), new Vector3(1, 1, 1)); BuildFaceHorizontal(vertices, new Vector3(0, 0, 1), new Vector3(1, 0, 0)); cubeVertexBuffer = new VertexBuffer(device, VertexPositionTexture.VertexDeclaration, vertices.Count, BufferUsage.WriteOnly); cubeVertexBuffer.SetData<VertexPositionTexture>(vertices.ToArray()); } private void BuildFace(List<VertexPositionTexture> vertices, Vector3 p1, Vector3 p2) { vertices.Add(BuildVertex(p1.X, p1.Y, p1.Z, 1, 0)); vertices.Add(BuildVertex(p1.X, p2.Y, p1.Z, 1, 1)); vertices.Add(BuildVertex(p2.X, p2.Y, p2.Z, 0, 1)); vertices.Add(BuildVertex(p2.X, p2.Y, p2.Z, 0, 1)); vertices.Add(BuildVertex(p2.X, p1.Y, p2.Z, 0, 0)); vertices.Add(BuildVertex(p1.X, p1.Y, p1.Z, 1, 0)); } private void BuildFaceHorizontal(List<VertexPositionTexture> vertices, Vector3 p1, Vector3 p2) { vertices.Add(BuildVertex(p1.X, p1.Y, p1.Z, 0, 1)); vertices.Add(BuildVertex(p2.X, p1.Y, p1.Z, 1, 1)); vertices.Add(BuildVertex(p2.X, p2.Y, p2.Z, 1, 0)); vertices.Add(BuildVertex(p1.X, p1.Y, p1.Z, 0, 1)); vertices.Add(BuildVertex(p2.X, p2.Y, p2.Z, 1, 0)); vertices.Add(BuildVertex(p1.X, p1.Y, p2.Z, 0, 0)); } private VertexPositionTexture BuildVertex(float x, float y, float z, float u, float v) { return new VertexPositionTexture(new Vector3(x, y, z), new Vector2(u, v)); } public void Draw(BasicEffect effect) { foreach (EffectPass pass in effect.CurrentTechnique.Passes) { pass.Apply(); device.SetVertexBuffer(cubeVertexBuffer); device.DrawPrimitives(PrimitiveType.TriangleList, 0, cubeVertexBuffer.VertexCount / 3); } } } The following class is a list that draws the cubes. public class DrawableList<T> : DrawableGameComponent { private BasicEffect effect; private ThirdPersonCam camera; private class Entity { public Vector3 Position { get; set; } public Matrix Orientation { get; set; } public Texture2D Texture { get; set; } } private Cube cube; private List<Entity> entities = new List<Entity>(); public DrawableList(Game game, ThirdPersonCam camera, BasicEffect effect) : base(game) { this.effect = effect; cube = new Cube(game.GraphicsDevice); this.camera = camera; } public void Add(Vector3 position, Matrix orientation, Texture2D texture) { entities.Add(new Entity() { Position = position, Orientation = orientation, Texture = texture }); } public override void Draw(GameTime gameTime) { foreach (var item in entities) { effect.VertexColorEnabled = false; effect.TextureEnabled = true; effect.Texture = item.Texture; Matrix center = Matrix.CreateTranslation(new Vector3(-0.5f, -0.5f, -0.5f)); Matrix scale = Matrix.CreateScale(1f); Matrix translate = Matrix.CreateTranslation(item.Position); effect.World = center * scale * translate; effect.View = camera.view; effect.Projection = camera.proj; effect.FogEnabled = true; effect.FogColor = Color.CornflowerBlue.ToVector3(); effect.FogStart = 1.0f; effect.FogEnd = 50.0f; cube.Draw(effect); } base.Draw(gameTime); } } } There are probably many reasons that my fps is so slow, but I can't seem to figure out how to fix it. I've looked at techcraft as well, but what I have is too specific to what I want the outcome to be to just rewrite everything from scratch

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• Problems with office automation in asp.net. I can use alternatives such as open-office, if I knew ho

  - by Vinicius Melquiades

  I have a ASP.NET 2.0 web application that should upload a ppt file and then extract its slides to images. For that I have imported office.dll and Microsoft.Office.Interop.PowerPoint.dll assemblies and wrote the following code public static int ExtractImages(string ppt, string targetPath, int width, int height) { var pptApplication = new ApplicationClass(); var pptPresentation = pptApplication.Presentations.Open(ppt, MsoTriState.msoTrue, MsoTriState.msoFalse, MsoTriState.msoFalse); var slides = new List<string>(); for (var i = 1; i <= pptPresentation.Slides.Count; i++) { var target = string.Format(targetPath, i); pptPresentation.Slides[i].Export(target, "jpg", width, height); slides.Add(new FileInfo(target).Name); } pptPresentation.Close(); return slides.Count; } If I run this code in my local machine, in asp.net or a executable, it runs perfectly. But If I try running it in the production server, I get the following error: System.Runtime.InteropServices.COMException (0x80004005): PowerPoint could not open the file. at Microsoft.Office.Interop.PowerPoint.Presentations.Open(String FileName, MsoTriState ReadOnly, MsoTriState Untitled, MsoTriState WithWindow) at PPTImageExtractor.PptConversor.ExtractImages(String caminhoPpt, String caminhoDestino, Int32 largura, Int32 altura, String caminhoThumbs, Int32 larguraThumb, Int32 alturaThumb, Boolean geraXml) at Upload.ProcessRequest(HttpContext context) The process is running with the user NT AUTHORITY\NETWORK SERVICE. IIS is configured to use anonymous authentication. The anonymous user is an administrator, I set it like this to allow the application to run without having to worry about permissions. In my development machine I have office 2010 beta1. I have tested with the executable in a pc with office 2007 as well. And if I run the code from the executable in the server, with office 2003 installed, it runs perfectly. To ensure that there wouldn't be any problems with permissions, everyone in the server has full access to the web site. The website is running in IIS7 and Classic Mode. I also heard that Open-office has an API that should be able to do this, but I couldn't find anything about it. I don't mind using DLLImport to do what I have to do and I can install open-office on the web server. Don't worry about rewriting this method, as long as the parameters are the same, everything will work. I appreciate your help. ps: Sorry for bad English.

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• How can I reliably check client identity whilst making DCOM calls to a C# .Net 3.5 Server?

  - by pionium

  Hi, I have an old Win32 C++ DCOM Server that I am rewriting to use C# .Net 3.5. The client applications sit on remote XP machines and are also written in C++. These clients must remain unchanged, hence I must implement the interfaces on new .Net objects. This has been done, and is working successfully regarding the implementation of the interfaces, and all of the calls are correctly being made from the old clients to the new .Net objects. However, I'm having problems obtaining the identity of the calling user from the DCOM Client. In order to try to identify the user who instigated the DCOM call, I have the following code on the server... [DllImport("ole32.dll")] static extern int CoImpersonateClient(); [DllImport("ole32.dll")] static extern int CoRevertToSelf(); private string CallingUser { get { string sCallingUser = null; if (CoImpersonateClient() == 0) { WindowsPrincipal wp = System.Threading.Thread.CurrentPrincipal as WindowsPrincipal; if (wp != null) { WindowsIdentity wi = wp.Identity as WindowsIdentity; if (wi != null && !string.IsNullOrEmpty(wi.Name)) sCallingUser = wi.Name; } if (CoRevertToSelf() != 0) ReportWin32Error("CoRevertToSelf"); } else ReportWin32Error("CoImpersonateClient"); return sCallingUser; } } private static void ReportWin32Error(string sFailingCall) { Win32Exception ex = new Win32Exception(); Logger.Write("Call to " + sFailingCall + " FAILED: " + ex.Message); } When I get the CallingUser property, the value returned the first few times is correct and the correct user name is identified, however, after 3 or 4 different users have successfully made calls (and it varies, so I can't be more specific), further users seem to be identified as users who had made earlier calls. What I have noticed is that the first few users have their DCOM calls handled on their own thread (ie all calls from a particular client are handled by a single unique thread), and then subsequent users are being handled by the same threads as the earlier users, and after the call to CoImpersonateClient(), the CurrentPrincipal matches that of the initial user of that thread. To Illustrate: User Tom makes DCOM calls which are handled by thread 1 (CurrentPrincipal correctly identifies Tom) User Dick makes DCOM calls which are handled by thread 2 (CurrentPrincipal correctly identifies Dick) User Harry makes DCOM calls which are handled by thread 3 (CurrentPrincipal correctly identifies Harry) User Bob makes DCOM calls which are handled by thread 3 (CurrentPrincipal incorrectly identifies him as Harry) As you can see in this illustration, calls from clients Harry and Bob are being handled on thread 3, and the server is identifying the calling client as Harry. Is there something that I am doing wrong? Are there any caveats or restrictions on using Impersonations in this way? Is there a better or different way that I can RELIABLY achieve what I am trying to do? All help would be greatly appreciated. Regards Andrew

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• C# file Decryption - Bad Data

  - by Jon

  Hi all, I am in the process of rewriting an old application. The old app stored data in a scoreboard file that was encrypted with the following code: private const String SSecretKey = @"?B?n?Mj?"; public DataTable GetScoreboardFromFile() { FileInfo f = new FileInfo(scoreBoardLocation); if (!f.Exists) { return setupNewScoreBoard(); } DESCryptoServiceProvider DES = new DESCryptoServiceProvider(); //A 64 bit key and IV is required for this provider. //Set secret key For DES algorithm. DES.Key = ASCIIEncoding.ASCII.GetBytes(SSecretKey); //Set initialization vector. DES.IV = ASCIIEncoding.ASCII.GetBytes(SSecretKey); //Create a file stream to read the encrypted file back. FileStream fsread = new FileStream(scoreBoardLocation, FileMode.Open, FileAccess.Read); //Create a DES decryptor from the DES instance. ICryptoTransform desdecrypt = DES.CreateDecryptor(); //Create crypto stream set to read and do a //DES decryption transform on incoming bytes. CryptoStream cryptostreamDecr = new CryptoStream(fsread, desdecrypt, CryptoStreamMode.Read); DataTable dTable = new DataTable("scoreboard"); dTable.ReadXml(new StreamReader(cryptostreamDecr)); cryptostreamDecr.Close(); fsread.Close(); return dTable; } This works fine. I have copied the code into my new app so that I can create a legacy loader and convert the data into the new format. The problem is I get a "Bad Data" error: System.Security.Cryptography.CryptographicException was unhandled Message="Bad Data.\r\n" Source="mscorlib" The error fires at this line: dTable.ReadXml(new StreamReader(cryptostreamDecr)); The encrypted file was created today on the same machine with the old code. I guess that maybe the encryption / decryption process uses the application name / file or something and therefore means I can not open it. Does anyone have an idea as to: A) Be able explain why this isn't working? B) Offer a solution that would allow me to be able to open files that were created with the legacy application and be able to convert them please? Thank you

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• Asynchronous subprocess on Windows

  - by Stigma

  First of all, the overall problem I am solving is a bit more complicated than I am showing here, so please do not tell me 'use threads with blocking' as it would not solve my actual situation without a fair, FAIR bit of rewriting and refactoring. I have several applications which are not mine to modify, which take data from stdin and poop it out on stdout after doing their magic. My task is to chain several of these programs. Problem is, sometimes they choke, and as such I need to track their progress which is outputted on STDERR. pA = subprocess.Popen(CommandA, shell=False, stdout=subprocess.PIPE, stderr=subprocess.PIPE) # ... some more processes make up the chain, but that is irrelevant to the problem pB = subprocess.Popen(CommandB, shell=False, stdout=subprocess.PIPE, stderr=subprocess.PIPE, stdin=pA.stdout ) Now, reading directly through pA.stdout.readline() and pB.stdout.readline(), or the plain read() functions, is a blocking matter. Since different applications output in different paces and different formats, blocking is not an option. (And as I wrote above, threading is not an option unless at a last, last resort.) pA.communicate() is deadlock safe, but since I need the information live, that is not an option either. Thus google brought me to this asynchronous subprocess snippet on ActiveState. All good at first, until I implement it. Comparing the cmd.exe output of pA.exe | pB.exe, ignoring the fact both output to the same window making for a mess, I see very instantaneous updates. However, I implement the same thing using the above snippet and the read_some() function declared there, and it takes over 10 seconds to notify updates of a single pipe. But when it does, it has updates leading all the way upto 40% progress, for example. Thus I do some more research, and see numerous subjects concerning PeekNamedPipe, anonymous handles, and returning 0 bytes available even though there is information available in the pipe. As the subject has proven quite a bit beyond my expertise to fix or code around, I come to Stack Overflow to look for guidance. :) My platform is W7 64-bit with Python 2.6, the applications are 32-bit in case it matters, and compatibility with Unix is not a concern. I can even deal with a full ctypes or pywin32 solution that subverts subprocess entirely if it is the only solution, as long as I can read from every stderr pipe asynchronously with immediate performance and no deadlocks. :)

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• Use a subdirectory as root with htaccess in Apache 1.3

  - by Andrew

  I'm trying to deploy a site generated with Jekyll and would like to keep the site in its own subfolder on my server to keep everything more organized. Essentially, I'd like to use the contents of /jekyll as the root unless a file similarly named exists in the actual web root. So something like /jekyll/sample-page/ would show as http://www.example.com/sample-page/, while something like /other-folder/ would display as http://www.example.com/other-folder. My test server runs Apache 2.2 and the following .htaccess (adapted from http://gist.github.com/97822) works flawlessly: RewriteEngine On # Map http://www.example.com to /jekyll. RewriteRule ^$ /jekyll/ [L] # Map http://www.example.com/x to /jekyll/x unless there is a x in the web root. RewriteCond %{REQUEST_FILENAME} !-f RewriteCond %{REQUEST_FILENAME} !-d RewriteCond %{REQUEST_URI} !^/jekyll/ RewriteRule ^(.*)$ /jekyll/$1 # Add trailing slash to directories without them so DirectoryIndex works. # This does not expose the internal URL. RewriteCond %{REQUEST_FILENAME} -d RewriteCond %{REQUEST_FILENAME} !/$ RewriteRule ^(.*)$ $1/ # Disable auto-adding slashes to directories without them, since this happens # after mod_rewrite and exposes the rewritten internal URL, e.g. turning # http://www.example.com/about into http://www.example.com/jekyll/about. DirectorySlash off However, my production server runs Apache 1.3, which doesn't allow DirectorySlash. If I disable it, the server gives a 500 error because of internal redirect overload. If I comment out the last section of ReWriteConds and rules: RewriteCond %{REQUEST_FILENAME} -d RewriteCond %{REQUEST_FILENAME} !/$ RewriteRule ^(.*)$ $1/ …everything mostly works: http://www.example.com/sample-page/ displays the correct content. However, if I omit the trailing slash, the URL in the address bar exposes the real internal URL structure: http://www.example.com/jekyll/sample-page/ What is the best way to account for directory slashes in Apache 1.3, where useful tools like DirectorySlash don't exist? How can I use the /jekyll/ directory as the site root without revealing the actual URL structure? Edit: After a ton of research into Apache 1.3, I've found that this problem is essentially a combination of two different issues listed at the Apache 1.3 URL Rewriting Guide. I have a (partially) moved DocumentRoot, which in theory would be taken care of with something like this: RewriteRule ^/$ /e/www/ [R] I also have the infamous "Trailing Slash Problem," which is solved by setting the RewriteBase (as was suggested in one of the responses below): RewriteBase /~quux/ RewriteRule ^foo$ foo/ [R] The problem is combining the two. Moving the document root doesn't (can't?) use RewriteBase—fixing trailing slashes requires(?) it… Hmm…

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• Suggestions for designing large-scale Java webapp from the group up

  - by Chris Thompson

  Hi all, I'm about to start developing a large-scale system and I'm struggling with which direction to proceed. I've done plenty of Java web apps before and I have plenty of experience with servlet containers and GWT and some experience with Spring. The problem is most of my webapps have been thrown together just to be a proof of concept and what I'm struggling with is what set of frameworks to use. I need to have both a browser based application as well as a web service designed to support access from mobile devices (Android and iPhone for now). Ideally, I'd like to design this system in such a way that I don't end up rewriting all of my servlets for each client (browser and phone) although I don't mind having some small checks in there to properly format the data. In addition, although I'm the only developer now, that won't necessarily be the case down the road and I'd like to design something that scales well both with regards to traffic and number of developers (isn't just a nightmare to maintain). So where I am now is planning on using GWT to design the browser-based interface but I'm struggling with how to reuse that code with to present the interface (most likely xml) for the mobile devices. Using GWT RPC would, I think, make it relatively easy to do all of the AJAX in the browser, but might make generating xml for the mobile phones difficult. In addition, I like the idea of using something like Hibernate for persistence and Spring Security to secure the whole thing. Again, I'm not sure how well those will cooperate with GWT (I think Hibernate should be fine...) There's obviously a lot more to this than I've presented here, but I've tried to give you the 5-minute overview. I'm a bit stumped and was wondering if anybody in the community had any experience starting from this place. Does what I'm trying to do make sense? Is it realistic? I have no doubt I can make all of these frameworks speak the same language, I'm just wondering if it's worth my time to fight with them. Also, am I missing a framework that would be really beneficial? Thanks in advance and sorry for the relatively broad question... Chris

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• wxPython ListCtrl Column Ignores Specific Fields

  - by g.d.d.c

  I'm rewriting this post to clarify some things and provide a full class definition for the Virtual List I'm having trouble with. The class is defined like so: from wx import ListCtrl, LC_REPORT, LC_VIRTUAL, LC_HRULES, LC_VRULES, \ EVT_LIST_COL_CLICK, EVT_LIST_CACHE_HINT, EVT_LIST_COL_RIGHT_CLICK, \ ImageList, IMAGE_LIST_SMALL, Menu, MenuItem, NewId, ITEM_CHECK, Frame, \ EVT_MENU class VirtualList(ListCtrl): def __init__(self, parent, datasource = None, style = LC_REPORT | LC_VIRTUAL | LC_HRULES | LC_VRULES): ListCtrl.__init__(self, parent, style = style) self.columns = [] self.il = ImageList(16, 16) self.Bind(EVT_LIST_CACHE_HINT, self.CheckCache) self.Bind(EVT_LIST_COL_CLICK, self.OnSort) if datasource is not None: self.datasource = datasource self.Bind(EVT_LIST_COL_RIGHT_CLICK, self.ShowAvailableColumns) self.datasource.list = self self.Populate() def SetDatasource(self, datasource): self.datasource = datasource def CheckCache(self, event): self.datasource.UpdateCache(event.GetCacheFrom(), event.GetCacheTo()) def OnGetItemText(self, item, col): return self.datasource.GetItem(item, self.columns[col]) def OnGetItemImage(self, item): return self.datasource.GetImg(item) def OnSort(self, event): self.datasource.SortByColumn(self.columns[event.Column]) self.Refresh() def UpdateCount(self): self.SetItemCount(self.datasource.GetCount()) def Populate(self): self.UpdateCount() self.datasource.MakeImgList(self.il) self.SetImageList(self.il, IMAGE_LIST_SMALL) self.ShowColumns() def ShowColumns(self): for col, (text, visible) in enumerate(self.datasource.GetColumnHeaders()): if visible: self.columns.append(text) self.InsertColumn(col, text, width = -2) def Filter(self, filter): self.datasource.Filter(filter) self.UpdateCount() self.Refresh() def ShowAvailableColumns(self, evt): colMenu = Menu() self.id2item = {} for idx, (text, visible) in enumerate(self.datasource.columns): id = NewId() self.id2item[id] = (idx, visible, text) item = MenuItem(colMenu, id, text, kind = ITEM_CHECK) colMenu.AppendItem(item) EVT_MENU(colMenu, id, self.ColumnToggle) item.Check(visible) Frame(self, -1).PopupMenu(colMenu) colMenu.Destroy() def ColumnToggle(self, evt): toggled = self.id2item[evt.GetId()] if toggled[1]: idx = self.columns.index(toggled[2]) self.datasource.columns[toggled[0]] = (self.datasource.columns[toggled[0]][0], False) self.DeleteColumn(idx) self.columns.pop(idx) else: self.datasource.columns[toggled[0]] = (self.datasource.columns[toggled[0]][0], True) idx = self.datasource.GetColumnHeaders().index((toggled[2], True)) self.columns.insert(idx, toggled[2]) self.InsertColumn(idx, toggled[2], width = -2) self.datasource.SaveColumns() I've added functions that allow for Column Toggling which facilitate my description of the issue I'm encountering. On the 3rd instance of this class in my application the Column at Index 1 will not display String values. Integer values are displayed properly. If I add print statements to my OnGetItemText method the values show up in my console properly. This behavior is not present in the first two instances of this class, and my class does not contain any type checking code with respect to value display. It was suggested by someone on the wxPython users' group that I create a standalone sample that demonstrates this issue if I can. I'm working on that, but have not yet had time to create a sample that does not rely on database access. Any suggestions or advice would be most appreciated. I'm tearing my hair out on this one.

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