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• SQL Select between two fields depending on the value of one field

  - by Filip

  Hi. I am using a PostgreSQL database, and in a table representing some measurements I've two columns: measurement, and interpolated. In the first I've the observation (measurement), and b is the interpolated value depending on nearby values. Every record with an original value has also an interpolated value. However, there are a lot of records without "original" observations (NULL), hence the values are interpolated and stored in the second column. So basically there are just two cases in the database: Value Value NULL Value Of course, it is preferable to use the value from the first column if available, hence I need to build a query to select the data from the first column, and if not available (NULL), then the database returns the value from the second column for the record in question. I have no idea how to build the SQL query. Please help. Thanks.

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• Optimizing Code

  - by Claudiu

  You are given a heap of code in your favorite language which combines to form a rather complicated application. It runs rather slowly, and your boss has asked you to optimize it. What are the steps you follow to most efficiently optimize the code? What strategies have you found to be unsuccessful when optimizing code? Re-writes: At what point do you decide to stop optimizing and say "This is as fast as it'll get without a complete re-write." In what cases would you advocate a simple complete re-write anyway? How would you go about designing it?

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• boost variant static_visitor problem picking correct function

  - by Steve

  I'm sure I'm having a problem with template resolution here, but I'm not sure why I'm having the problem. I have a static visitor I'm passing to boost variant where i've had to do template specialization for certain cases. The case for everything except for MyClass should throw in the static_visitor below. Unfortunately, when the visitor is applied to pull a MyClass out, it selects the most generic case rather than the exact match. I would type each case explicitly, but that will be rather long. So, why is the compiler resolving the most generic case over the exact match, and is there anyway to fix it template<> class CastVisitor<MyClass>:public boost::static_visitor<MyClass> { public: template<typename U> MyClass operator()(const U & i) const { throw std::exception("Unable to cast"); } MyClass operator()(const MyClass& i) { return i; } };

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• How to know if a PDF contains only images or has been OCR scanned for searching?

  - by Bratch

  I have a bunch of PDF files that came from scanned documents. The files contain a mix of images and text. Some were scanned as images with no OCR, so each PDF page is one large image, even where the whole page is entirely text. Others were scanned with OCR and contain images and searchable text where text is present. In many cases even words in the images were made searchable. I want to make an automated process to recognize the text in all of the scanned documents using OCR, with Acrobat 8 Pro, but I don't want to re-OCR the files that have already been through the OCR process in the past. Does anyone know if there is a way to tell which ones contain only images, and which ones already contain searchable text? I'm planning on doing this in C# or VB.NET but I don't think being able to tell the two kinds of files apart is language dependent.

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• Handle complex options with Boost's program_options

  - by R S

  I have a program that generates graphs using different multi-level models. Each multi-level model consists of a generation of a smaller seed graph (say, 50 nodes) which can be created from several models (for example - for each possible edge, choose to include it with probability p). After the seed graph generation, the graph is expanded into a larger one (say 1000 nodes), using one of another set of models. In each of the two stages, each model require a different number of parameters. I would like to be have program_options parse the different possible parameters, according to the names of the models. For example, say I have two seed graphs models: SA, which has 1 parameters, and SB, which has two. Also for the expansion part, I have two models: A and B, again with 1 and 2 parameters, respectively. I would like to be able do something like: ./graph_generator --seed=SA 0.1 --expansion=A 0.2 ./graph_generator --seed=SB 0.1 3 --expansion=A 0.2 ./graph_generator --seed=SA 0.1 --expansion=B 10 20 ./graph_generator --seed=SB 0.1 3 --expansion=B 10 20 and have the parameters parsed correctly. Is that even possible?

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• Delphi: How to assign dynamically an event handler without overwriting the existing event handler?

  - by user193655

  I need to loop through Components and assign an event handler (for example Dynamically assigning OnClick event for all TButton to ShowMessage('You clicked on ' + (Sender as TButton).Name); The problem is that in some cases I alreasy assigned the TButton OnClick event. Is there a way to solve the problem? Let's imagine I have Button1 for which the harcoded onclick event handler is: ShowMessage('This is Button1'); After my "parsing" I would like that the full event handler for Button1 becomes: ShowMessage('This is Button1'); // design time event handler code ShowMessage('You clicked on ' + (Sender as TButton).Name); // runtime added Note: I am looking for a soliution that allows me to use TButton as it is without inheriting from it.

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• Are these 2 sql queries equivalent in all respects (e.g. estimated and actual execution plan)?

  - by Xerion

  Are query 1) == 2) in terms of estimated query plan AND actual plan? (can statistics affect the actual plan here, ever?) declare @cat int -- input param from prc ... 1) select * from A as a join B as b on b.id = a.id on b.cat = @cat join C as c on c.fid = b.fid on c.cat = @cat where a.cat = @cat 2) select * from A as a join B as b on b.id = a.id on b.cat = a.cat join C as c on c.fid = b.fid on c.cat = b.cat where a.cat = @cat It seems to me that these should logically be equivalent and the execution plan should always be the same regardless of actual difference in tables. And adding more conditions either in join, or where, or add more tables to join shouldn't change this. Are there cases this is not true?

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• Intersection of line and rectangle with maximum segment length

  - by Aarkan

  I have a vector represented by the slope m. Then there is rectangle (assume axis aligned), which is represented by top-left and bottom-right corner. Of course, there may be many lines with slope m and intersecting the given rectangle. The problem is to find out the line whose length of line intercept inside the rectangle is maximum among all such lines. i.e., if the line intersects rectangle at P1 and P2, then the problem is to find the equation of line for which length of P1P2 is maximum. I proceeded like this. Let the line is: y = m*x + c. Then find out the intersection with each side of rectangle and finding out the maxima for distance function between each pair of points. But it will only give me the length of line segment and there seem to be many corner cases to handle. Could anyone please suggest a better way to do this. Thanks in advance.

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• C# - LINQ Including headache...

  - by ebb

  Case can have many Replies and one User, Replies can have one Case and one User, One User can have many Replies and many Cases. ObjectSet <= Case Object (IDbSet) ObjectSet.Include(x => x.User).Include(x => x.Replies).FirstOrDefault(x => x.Id == caseId); But the User Object for each Reply are not included? Only the User object for Case is Included? How would I include the User objects for the Replies too? Thanks in advance!

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• Optimize MySQL database query

  - by rajeeesh

  I had a commenting application in my web site. The comments will store in a MySQL table . table structure as follows id | Comment | user | created_date ------------------------------------------------------ 12 | comment he | 1245 | 2012-03-30 12:15:00 ------------------------------------------------------ I need to run a query for listing all the comments after a specific time. ie .. a query like this SELECT * FROM comments WHERE created_date > "2012-03-29 12:15:00" ORDER BY created_date DESC Its working fine.. My question is if I got a 1-2 lakh entry in this table is this query is sufficient for the purpose ? or this query will take time to execute ? In most cases I have to show last 2 days data + periodically ( interval of 10 mins ) checking for updates with ajax from this table ... Please help Thanks

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• Factory Method Using Is/As Operator

  - by Swim

  I have factory that looks something like the following snippet. Foo is a wrapper class for Bar and in most cases (but not all), there is a 1:1 mapping. As a rule, Bar cannot know anything about Foo, yet Foo takes an instance of Bar. Is there a better/cleaner approach to doing this? public Foo Make( Bar obj ) { if( obj is Bar1 ) return new Foo1( obj as Bar1 ); if( obj is Bar2 ) return new Foo2( obj as Bar2 ); if( obj is Bar3 ) return new Foo3( obj as Bar3 ); if( obj is Bar4 ) return new Foo3( obj as Bar4 ); // same wrapper as Bar3 throw new ArgumentException(); } At first glance, this question might look like a duplicate (maybe it is), but I haven't seen one exactly like it. Here is one that is close, but not quite: http://stackoverflow.com/questions/242097/factory-based-on-typeof-or-is-a

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• Proper mechanism for sending PHP errors to the client

  - by Chris

  Greetings, I was trying to discover a proper way to send captured errors or business logic exceptions to the client in an Ajax-PHP system. In my case, the browser needs to react differently depending on whether a request was successful or not. However in all the examples I've found, only a simple string is reported back to the browser in both cases. Eg: if (something worked) echo "Success!"; else echo "ERROR: that failed"; So when the browser gets back the Ajax response, the only way to know if an error occurred would be to parse the string (looking for 'error' perhaps). This seems clunky. Is there a better/proper way to send back the Ajax response & notify the browser of an error? Thank you.

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• Which one gives you more advantages: Microsoft or SUN/Oracle certification?

  - by edwin.nathaniel

  Which one gives you more advantages: Microsoft or SUN/Oracle certification? If you don't mind, please relate your answer to your career (dev, sys-admin, dba), industry (finance, general consulting, business apps, software house), and location (where you live, does it influence your decision?) as well. One reason I asked this because I heard that having MCP (in C#, MCSAD or whatever the cert is called these days) could give you extra point from the employer perspective if they're a Microsoft Partner. I don't quite understand why and am also wondering if SUN/Oracle certificate holder have similar edge/benefit. I'm also interested to know if Certification plays role where you live. For example: certification could be a big negative sign in Silicon Valley, but might be helpful if you're in other US/Canada cities or outside USA/Canada. If you are an independent software consultant, do these certification helps you win bids? I totally understand that this question might be subjective and could be "closed". But it doesn't hurt to ask I suppose. I also understand that there are people who dislike/disagree (or have negative perspective on technology certification). While there are people who have the opinion that "these are not the kind of employers you would want to work with", I respect you guys, but sometime a pure software product company might not exist in certain cities in the world. And if certification can help one's career somewhere else, I guess that means more opportunities right? I've had experienced in both platforms: (short) .NET and (not too long) Java (minus Oracle DB stuff), but I think it's about time I have to pick one of them and be good at. Where I live right now might also dictates my career albeit insignificant. Anyhow, this last paragraph is just tiny blurb. Thanks!

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• ASP.Net website makes browser load unwanted (non-referenced) plugins

  - by alec0001

  I've found that some of my ASP.Net web apps prompt the browser to load plugins that I'm not explicitely using and certainly haven't deliberately referenced in the project settings. Two that come to mind are for MS MediaPlayer and the "SVG Viewer for Netscape". The only commonality I've determined so far is that the two sites/apps affected both use Master pages (nested in some cases). We don't use SVG file types (just the normal mix of jpg/gif/png) and no video/audio (not yet anyway). Can anyone provide a hint as to where the references for these might be creeping in? e.g. Is it a server-level include? Or a .Net runtime default when using master pages? Does anyone else even experience this, or is it just me? No urgency, I'd just like to remove it if possible. Thanks. Al

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• How to limit a request execution time of WCF service?

  - by Kamarey

  Is there something in WCF configuration that defines a timeout for executing a request at service side? E.g. WCF service will stop executing request after some time period. I have a service which make some work depending on client input. In some cases a such call may take too much time. I want to limit the execution time of such requests on service side, not client one using SendTimeout. I know about OperationTimeout property, but it doesn't abort the service request, it just tells a client that the request is timed out.

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• regular expression for validation not working

  - by Camran

  I have a "description textarea" inside a form where user may enter a description for an item. This is validated with javascript before the form beeing submitted. One of the validation-steps is this: else if (!fld.value.match(desExp)){ And desExp: var desExp = /^\s*(\w[^\w]*){3}.*$/gm; Now my problem, this works fine on all cases except for descriptions where the description BEGINS with a special character of the swedish language (å, ä, ö). This wont work: åäö hello world But this will: hello world åäö Any fixes? Thanks

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• Using ANTLR with Left-Recursive Rules

  - by CNevin561

  Basically Ive written a Parse for a language with just basic arithmetic operators ( +, -, * / ) etc, but for the minus and plus cases, the Abstract Syntax Tree which is generated has parsed them as right associative when they need to be left associative. Having a googled for a solution, i found a tutorial that suggests rewriting the rule from: Expression ::= Expression <operator> Term | Term as Expression ::= Term <operator> Expression*. However in my head this seems to generate the tree the wrong way round. Any pointers on a way to resolve this issue?

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• Using new (this) to reuse constructors

  - by Brandon Bodnar

  This came up recently in a class for which I am a teaching assistant. We were teaching the students how to do copy constructors in c++, and the students who were originally taught java asked if you can call one constructor from another. I know the answer to this is no, as they are using the pedantic flag for their code in class, and the old standards do not have support for this. I found on Stackoverflow and other sites a suggestion to fake this using new (this) such as follows class MyClass { private: int * storedValue; public: MyClass(int initialValue = 0) { storedValue = new int(initialValue); } ~ MyClass() { delete storedValue; } MyClass(const MyClass &b) { new (this) MyClass(*(b.storedValue)); } int value() { return *storedValue; } }; This is really simple code, and obviously does not save any code by reusing the constructor, but it is just for example. My question is if this is even standard compliant, and if there are any edge cases that should be considered that would prevent this from being sound code?

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• The return value should be a list but doesn't return as expected?! - Python newbie

  - by user1432941

  Hi this must be a very simple solution that has eluded me this last hour. I've tried to build this test function where the return value of the test_cases list should match the values in the test_case_answers list but for some reason, test case 1 and test case 2 fail. When i print the return values for the test cases they return the correct answers, but for some reason test case 1 and test case 2 return False. Thanks for your help! import math test_cases = [1, 9, -3] test_case_answers = [1, 3, 0] def custom_sqrt(num): for i in range(len(test_cases)): if test_cases[i] >= 0: return math.sqrt(test_cases[i]) else: return 0 for i in range(len(test_cases)): if custom_sqrt(test_cases[i]) != test_case_answers[i]: print "Test Case #", i, "failed!" custom_sqrt(test_cases)

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• How do browser cookie domains work?

  - by Vilx-

  Due to weird domain/subdomain cookie issues that I'm getting, I'd like to know how browsers handle cookies. If they do it in different ways, it would also be nice to know the differences. In other words - when a browser receives a cookie, that cookie MAY have a domain and a path attached to it. Or not, in which case the browser probably substitutes some defaults for them. Question 1: what are they? Later, when the browser is about to make a request, it checks its cookies and filters out the ones it should send for that request. It does so by matching them against the requests path and domain. Question 2: what are the matching rules? Added: The reason I'm asking this is because I'm interested in some edge cases. Like: Will a cookie for .example.com be available for www.example.com? Will a cookie for .example.com be available for example.com? Will a cookie for example.com be available for www.example.com? Will a cookie for example.com be available for anotherexample.com? Will www.example.com be able to set cookie for example.com? Will www.example.com be able to set cookie for www2.example.com? Will www.example.com be able to set cookie for .com? Etc. Added 2: Also, could someone suggest how I should set a cookie so that: It can be set by either www.example.com or example.com; It is accessible by both www.example.com and example.com.

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• Aside from performance concerns, is Java still chosen over Groovy/JRuby etc.?

  - by yar

  [This is an empirical question about the state-of-the-art: I am NOT asking if Java is cooler or less cool than the dynamic languages that work in the JVM.] Aside from cases where performance is a main decision factor, do companies/developers still willingly chose Java over Groovy, JRuby or JPython? Personal Note: The reason I am asking is that, while I do some subset of my professional work in Ruby (not JRuby, for now), in my personal projects I use Java. While I have written non-trivial apps in Groovy, I prefer Java, but I wonder if I should just get over it and do everything in Groovy. I like Java because I feel that static typing saves me time and aids refactoring. (No, I am not familiar with Scala.) However, I feel that this very empirical, on-topic programming question may inform my decision.

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• A company that had a successful product but went bust for not innovating?

  - by Dan

  At the company that I work we have a successful software product that did well but is now obsolete and unmaintainable. I am trying to explain that you need to innovate and replace this product with new offering in order to survive. I am looking for some good examples of companies that made the mistake that we are close to making - relying on one successful product way over it's normal lifetime, so I could use it as illustration when making an argument. These products need not be software, emblematic cases that illustrate well this situation but where product was not software are also appreciated.

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• Is pthread_spin_trylock safe inside of sigsegv handler of multithreaded application?

  - by TWMouton

  I am trying to implement a handler that on SIGSEGV will collect some information such as process-id, thread-id and a backtrace and write this information to a file/pipe/socket. The problem lies in that there is the (probably pretty high) possibility that if one thread experienced a SIGSEGV that the others will shortly follow. If two threads happen to make it to the bit of code where they're writing their report out at the same time then they'll interleave their writing (to the same file). I know that I should only be using async-signal-safe functions as detailed in signal(7) I also have seen at least two cases here and video linked in top answer here where others have used pthread_spin_trylock to get around this problem. Is this a safe way to prevent the above problem?

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• What's the right way to show a non-modal child dialog in MFC (VS2005)?

  - by John

  Rather than have everything in one big dialog, I'm looking at being able to display child dialogs for separate groups of controls. The idea is these are not free-floating child dialogs like floating toolbars, but would be shown with no title-bar, their position locked to the parent dialog... so as you drag the parent dialog any open child is dragged too. NOTE: these child windows are not inside the parent dialog, they would typically be 'glued' to the edge of it. In MFC/VC++ 2005, what's the best way to do this? For testing, I currently have a standard MFC Dialog-based app setup with CMainDlg, and I've then created a 'widget dialog' CWidgetDlg. So far I've got a member variable CWidgetDlg MainDlg::m_Widget and a button on CMainDlg with a handler like CMainDlg::OnDisplayWidgetBtn() { m_Widget.ShowWindow(TRUE); } But of course m_Widget hasn't got a HWND setup, and I am trying to remember the right way to do this? For dialog controls I can use DDX but what about child dialogs? And is this a reasonable approach, or is there a nicer, more automated way?

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• How to display a pic selected from phone to a local html in the Webview

  - by Kavin

  Hi all, I am developing a small application in Android. I come across a problem, and not sure whether it is possible in Android platform. I have some local html files. There is an Activity contains a webview, which is used to display these local html files. In some cases, I want to display a picture selected from phone into one of these local html files. Is it possible? Has anyone resolved such problem? I appreciate any of your replies. Best

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