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• When is the reintegrate option really necessary?

  - by Tor Hovland

  If you always sync a feature branch before you merge it back, why do you really have to use the --reintegrate option? The Subversion book says: When merging your branch back to the trunk, however, the underlying mathematics is quite different. Your feature branch is now a mishmosh of both duplicated trunk changes and private branch changes, so there's no simple contiguous range of revisions to copy over. By specifying the --reintegrate option, you're asking Subversion to carefully replicate only those changes unique to your branch. (And in fact, it does this by comparing the latest trunk tree with the latest branch tree: the resulting difference is exactly your branch changes!) So the --reintegrate option only merges the changes that are unique to the feature branch. But if you always sync before merge (which is a recommended practice, in order to deal with any conflicts on the feature branch), then the only changes between the branches are the changes that are unique to the feature branch, right? And if Subversion tries to merge code that is already on the target branch, it will just do nothing, right? In this blog post, Mark Phippard writes: http://blogs.open.collab.net/svn/2008/07/subversion-merg.html If we include those synched revisions, then we merge back changes that already exist in trunk. This yields unnecessary and confusing conflicts. Can somebody give me an example of when dropping reintegrate gives me unnecessary conflicts?

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• Thread-safety of read-only memory access

  - by Edmund

  I've implemented the Barnes-Hut gravity algorithm in C as follows: Build a tree of clustered stars. For each star, traverse the tree and apply the gravitational forces from each applicable node. Update the star velocities and positions. Stage 2 is the most expensive stage, and so is implemented in parallel by dividing the set of stars. E.g. with 1000 stars and 2 threads, I have one thread processing the first 500 stars and the second thread processing the second 500. In practice this works: it speeds the computation by about 30% with two threads on a two-core machine, compared to the non-threaded version. Additionally, it yields the same numerical results as the original non-threaded version. My concern is that the two threads are accessing the same resource (namely, the tree) simultaneously. I have not added any synchronisation to the thread workers, so it's likely they will attempt to read from the same location at some point. Although access to the tree is strictly read-only I am not 100% sure it's safe. It has worked when I've tested it but I know this is no guarantee of correctness! Questions Do I need to make a private copy of the tree for each thread? Even if it is safe, are there performance problems of accessing the same memory from multiple threads?

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• Groovy htmlunit getFirstByXPath returning null

  - by StartingGroovy

  I have had a few issues with HtmlUnit returning nulls lately and am looking for guidance. each of my results for grabbing the first row of a website have returned null. I am wondering if someone can A) explain why they might be returning null B) explain better ways (if there are some) to go about getting the information Here is my current code (URL is in the source): client = new WebClient(BrowserVersion.FIREFOX_3) client.javaScriptEnabled = false def url = "http://www.hidemyass.com/proxy-list/" page = client.getPage(url) IpAddress = page.getFirstByXPath("//html/body/div/div/form/table/tbody/tr/td[2]").getValue() println "IP Address is: $data" //returns null //Port_Number is an Image Country = page.getFirstByXPath("//html/body/div/div/form/table/tbody/tr/td[4][@class='country']/@rel").getValue() println "Country abbreviation is: $Country" //differentiate speed and connection by name of gif? Type = page.getFirstByXPath("//html/body/div/div/form/table/tbody/tr/td[7]").getValue() println "Proxy type is: $Type" Anonymity = page.getFirstByXPath("//html/body/div/div/form/table/tbody/tr/td[8]").getValue() println "Anonymity Level is: $Anonymity" client.closeAllWindows() Right now all of my XPaths return null and .getValue() obviously doesn't work on null. I also have questions as to what I should do about the PORT since it is an image? Is there a better alternative than downloading it and attempting to solve it by OCR? Side Note There is no significance in this site, I was just looking for a site that I could practice scraping on (the last one I ran into issues of fragment identities and couldn't get an answer to: HtmlUnit getByXpath returns null and HtmlUnit and Fragment Identities )

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• Why do I need to give my options a value attribute in my dropdown? JQuery related.

  - by Alex

  So far in my web developing experiences, I've noticed that almost all web developers/designers choose to give their options in a select a value like so: <select name="foo"> <option value="bar">BarCheese</option> // etc. // etc. </select> Is this because it is best practice to do so? I ask this because I have done a lot of work with jQuery and dropdown's lately, and sometimes I get really annoyed when I have to check something like: $('select[name=foo]').val() == "bar"); To me, many times that seems less clear than just being able to check the val() against BarCheese. So why is it that most web developers/designers specify a value paramater instead of just letting the options actual value be its value? And yes, if the option has a value attribute I know I can do something like this: $('select[name=foo] option:contains("BarCheese")').attr('selected', 'selected'); But I would still really like to know why this is done. Thanks!!

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• Returning pointers in a thread-safe way.

  - by Roddy

  Assume I have a thread-safe collection of Things (call it a ThingList), and I want to add the following function. Thing * ThingList::findByName(string name) { return &item[name]; // or something similar.. } But by doing this, I've delegated the responsibility for thread safety to the calling code, which would have to do something like this: try { list.lock(); // NEEDED FOR THREAD SAFETY Thing *foo = list.findByName("wibble"); foo->Bar = 123; list.unlock(); } catch (...) { list.unlock(); throw; } Obviously a RAII lock/unlock object would simplify/remove the try/catch/unlocks, but it's still easy for the caller to forget. There are a few alternatives I've looked at: Return Thing by value, instead of a pointer - fine unless you need to modify the Thing Add function ThingList::setItemBar(string name, int value) - fine, but these tend to proliferate Return a pointerlike object which locks the list on creation and unlocks it again on destruction. Not sure if this is good/bad practice... What's the right approach to dealing with this?

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• Open-sourcing a web site with active users?

  - by Lars Yencken

  I currently run several research-related web-sites with active users, and these sites use some personally identifying information about these users (their email address, IP address, and query history). Ideally I'd release the code to these sites as open source, so that other people could easily run similar sites, and more importantly scrutinise and replicate my work, but I haven't been comfortable doing so, since I'm unsure of the security implications. For example, I wouldn't want my users' details to be accessed or distributed by a third party who found some flaw in my site, something which might be easy to do with full source access. I've tried going half-way by refactoring the (Django) site into more independent modules, and releasing those, but this is very time consuming, and in practice I've never gotten around to releasing enough that a third party can replicate the site(s) easily. I also feel that maybe I'm kidding myself, and that this process is really no different to releasing the full source. What would you recommend in cases like this? Would you open-source the site and take the risk? As an alternative, would you advertise the source as "available upon request" to other researchers, so that you at least know who has the code? Or would you just apologise to them and keep it closed in order to protect users?

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• Simplest way to mix sequences of types with iostreams?

  - by Kylotan

  I have a function void write<typename T>(const T&) which is implemented in terms of writing the T object to an ostream, and a matching function T read<typename T>() that reads a T from an istream. I am basically using iostreams as a plain text serialisation format, which obviously works fine for most built-in types, although I'm not sure how to effectively handle std::strings just yet. I'd like to be able to write out a sequence of objects too, eg void write<typename T>(const std::vector<T>&) or an iterator based equivalent (although in practice, it would always be used with a vector). However, while writing an overload that iterates over the elements and writes them out is easy enough to do, this doesn't add enough information to allow the matching read operation to know how each element is delimited, which is essentially the same problem that I have with a single std::string. Is there a single approach that can work for all basic types and std::string? Or perhaps I can get away with 2 overloads, one for numerical types, and one for strings? (Either using different delimiters or the string using a delimiter escaping mechanism, perhaps.)

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• How to Implement an Interface that Requires Duplicate Member Names?

  - by Will Marcouiller

  I often have to implement some interfaces such as IEnumerable<T> in my code. Each time, when implementing automatically, I encounter the following: public IEnumerator<T> GetEnumerator() { // Code here... } public IEnumerator GetEnumerator1() { // Code here... } Though I have to implement both GetEnumerator() methods, they impossibly can have the same name, even if we understand that they do the same, somehow. The compiler can't treat them as one being the overload of the other, because only the return type differs. When doing so, I manage to set the GetEnumerator1() accessor to private. This way, the compiler doesn't complaint about not implementing the interface member, and I simply throw a NotImplementedException within the method's body. However, I wonder whether it is a good practice, or if I shall proceed differently, as perhaps a method alias or something like so. What is the best approach while implementing an interface such as IEnumerable<T> that requires the implementation of two different methods with the same name? EDIT #1 Does VB.NET reacts differently from C# while implementing interfaces, since in VB.NET it is explicitly implemented, thus forcing the GetEnumerator1(). Here's the code: Public Function GetEnumerator() As System.Collections.Generic.IEnumerator(Of T) Implements System.Collections.Generic.IEnumerable(Of T).GetEnumerator // Code here... End Function Public Function GetEnumerator1() As System.Collections.Generic.IEnumerator Implements System.Collections.Generic.IEnumerable.GetEnumerator // Code here... End Function Both GetEnumerator() methods are explicitly implemented, and the compile will refuse them to have the same name. Why?

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• Omit return type in C++0x

  - by Clinton

  I've recently found myself using the following macro with gcc 4.5 in C++0x mode: #define RETURN(x) -> decltype(x) { return x; } And writing functions like this: template <class T> auto f(T&& x) RETURN (( g(h(std::forward<T>(x))) )) I've been doing this to avoid the inconvenience having to effectively write the function body twice, and having keep changes in the body and the return type in sync (which in my opinion is a disaster waiting to happen). The problem is that this technique only works on one line functions. So when I have something like this (convoluted example): template <class T> auto f(T&& x) -> ... { auto y1 = f(x); auto y2 = h(y1, g1(x)); auto y3 = h(y1, g2(x)); if (y1) { ++y3; } return h2(y2, y3); } Then I have to put something horrible in the return type. Furthermore, whenever I update the function, I'll need to change the return type, and if I don't change it correctly, I'll get a compile error if I'm lucky, or a runtime bug in the worse case. Having to copy and paste changes to two locations and keep them in sync I feel is not good practice. And I can't think of a situation where I'd want an implicit cast on return instead of an explicit cast. Surely there is a way to ask the compiler to deduce this information. What is the point of the compiler keeping it a secret? I thought C++0x was designed so such duplication would not be required.

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• Should I use a binary or a text file for storing protobuf messages?

  - by nbolton

  Using Google protobuf, I am saving my serialized messaged data to a file - in each file there are several messages. We have both C++ and Python versions of the code, so I need to use protobuf functions that are available in both languages. I have experimented with using SerializeToArray and SerializeAsString and there seems to be the following unfortunate conditions: SerializeToArray: As suggested in one answer, the best way to use this is to prefix each message with it's data size. This would work great for C++, but in Python it doesn't look like this is possible - am I wrong? SerializeAsString: This generates a serialized string equivalent to it's binary counterpart - which I can save to a file, but what happens if one of the characters in the serialization result is \n - how do we find line endings, or the ending of messages for that matter? Update: Please allow me to rephrase slightly. As I understand it, I cannot write binary data in C++ because then our Python application cannot read the data, since it can only parse string serialized messages. Should I then instead use SerializeAsString in both C++ and Python? If yes, then is it best practice to store such data in a text file rather than a binary file? My gut feeling is binary, but as you can see this doesn't look like an option.

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• What should I do with an over-bloated select-box/drop-down

  - by Tristan Havelick

  All web developers run into this problem when the amount of data in their project grows, and I have yet to see a definitive, intuitive best practice for solving it. When you start a project, you often create forms with tags to help pick related objects for one-to-many relationships. For instance, I might have a system with Neighbors and each Neighbor belongs to a Neighborhood. In version 1 of the application I create an edit user form that has a drop down for selecting users, that simply lists the 5 possible neighborhoods in my geographically limited application. In the beginning, this works great. So long as I have maybe 100 records or less, my select box will load quickly, and be fairly easy to use. However, lets say my application takes off and goes national. Instead of 5 neighborhoods I have 10,000. Suddenly my little drop-down takes forever to load, and once it loads, its hard to find your neighborhood in the massive alphabetically sorted list. Now, in this particular situation, having hierarchical data, and letting users drill down using several dynamically generated drop downs would probably work okay. However, what is the best solution when the objects/records being selected are not hierarchical in nature? In the past, of done this with a popup with a search box, and a list, but this seems clunky and dated. In today's web 2.0 world, what is a good way to find one object amongst many for ones forms? I've considered using an Ajaxifed search box, but this seems to work best for free text, and falls apart a little when the data to be saved is just a reference to another object or record. Feel free to cite specific libraries with generic solutions to this problem, or simply share what you have done in your projects in a more general way

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• Keeping Linq to SQL alive when using ViewModels (ASP.NET MVC)

  - by Kohan

  I have recently started using custom ViewModels (For example, CustomerViewModel) public class CustomerViewModel { public IList<Customer> Customers{ get; set; } public int ProductId{ get; set; } public CustomerViewModel(IList<Customer> customers, int productId) { this.Customers= customers; this.ProductId= productId; } public CustomerViewModel() { } } ... and am now passing them to my view instead of the Entities themselves (for example, var Custs = repository.getAllCusts(id) ) as it seems good practice to do so. The problem i have encountered is that when using ViewModels; by the time it has got to the the view i have lost the ability to lazy load on customers. I do not believe this was the case before using them. Is it possible to retain the ability of Lazy Loading while still using ViewModels? Or do i have to eager load using this method? Thanks, Kohan.

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• Does everything after my try statement have to be encompassed in that try statement to access variab

  - by Mithrax

  I'm learning java and one thing I've found that I don't like, is generally when I have code like this: import java.util.*; import java.io.*; public class GraphProblem { public static void main(String[] args) { if (args.length < 2) { System.out.println("Error: Please specify a graph file!"); return; } FileReader in = new FileReader(args[1]); Scanner input = new Scanner(in); int size = input.nextInt(); WeightedGraph graph = new WeightedGraph(size); for(int i = 0; i < size; i++) { graph.setLabel(i,Character.toString((char)('A' + i))); } for(int i = 0; i < size; i++) { for(int j = 0; j < size; j++) { graph.addEdge(i, j, input.nextInt()); } } // .. lots more code } } I have an uncaught exception around my FileReader. So, I have to wrap it in a try-catch to catch that specific exception. My question is does that try { } have to encompass everything after that in my method that wants to use either my FileReader (in) or my Scanner (input)? If I don't wrap the whole remainder of the program in that try statement, then anything outside of it can't access the in/input because it may of not been initialized or has been initialized outside of its scope. So I can't isolate the try-catch to just say the portion that intializes the FileReader and close the try statement immediately after that. So, is it the "best practice" to have the try statement wrapping all portions of the code that are going to access variables initialized in it? Thanks!

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• C# performance methods of receiving data from a socket?

  - by Daniel

  Lets assume we have a simple internet socket, and its going to send 10 megabytes (because i want to ignore memory issues) of random data through. Is there any performance difference or a best practice method that one should use for receiving data? The final output data should be represented by a byte[]. Yes i know writing an arbitrary amount of data to memory is bad, and if I was downloading a large file i wouldn't be doing it like this. But for argument sake lets ignore that and assume its a smallish amount of data. I also realise that the bottleneck here is probably not the memory management but rather the socket receiving. I just want to know what would be the most efficient method of receiving data. A few dodgy ways can think of is: Have a List and a buffer, after the buffer is full, add it to the list and at the end list.ToArray() to get the byte[] Write the buffer to a memory stream, after its complete construct a byte[] of the stream.Length and read it all into it in order to get the byte[] output. Is there a more efficient/better way of doing this?

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• how do I best create a set of list classes to match my business objects

  - by ken-forslund

  I'm a bit fuzzy on the best way to solve the problem of needing a list for each of my business objects that implements some overridden functions. Here's the setup: I have a baseObject that sets up database, and has its proper Dispose() method All my other business objects inherit from it, and if necessary, override Dispose() Some of these classes also contain arrays (lists) of other objects. So I create a class that holds a List of these. I'm aware I could just use the generic List, but that doesn't let me add extra features like Dispose() so it will loop through and clean up. So if I had objects called User, Project and Schedule, I would create UserList, ProjectList, ScheduleList. In the past, I have simply had these inherit from List< with the appropriate class named and then written the pile of common functions I wanted it to have, like Dispose(). this meant I would verify by hand, that each of these List classes had the same set of methods. Some of these classes had pretty simple versions of these methods that could have been inherited from a base list class. I could write an interface, to force me to ensure that each of my List classes has the same functions, but interfaces don't let me write common base functions that SOME of the lists might override. I had tried to write a baseObjectList that inherited from List, and then make my other Lists inherit from that, but there are issues with that (which is really why I came here). One of which was trying to use the Find() method with a predicate. I've simplified the problem down to just a discussion of Dispose() method on the list that loops through and disposes its contents, but in reality, I have several other common functions that I want all my lists to have. What's the best practice to solve this organizational matter?

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• Is there anything inherently wrong with long variable/method names in Java?

  - by Doug Smith

  I know this is probably is a question of personal opinion, but I want to know what's standard practice and what would be frowned upon. One of my profs in university always seems to make his variable and method names as short as possible (getAmt() instead of getAmount) for instance. I have no objection to this, but personally, I prefer to have mine a little longer if it adds descriptiveness so the person reading it won't have to check or refer to documentation. For instance, we made a method that given a list of players, returns the player who scored the most goals. I made the method getPlayerWithMostGoals(), is this wrong? I toiled over choosing a way to make it shorter for awhile, but then I thought "why?". It gets the point across clearly and Eclipse makes it easy to autocomplete it when I type. I'm just wondering if the short variable names are a piece of the past due to needing everything to be as small as possible to be efficient. Is this still a requirement?

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• mysql get table based on common column between two tables

  - by Zentdayn

  while trying to learn sql i came across "Learn SQL The Hard Way" and i started reading it. Everything was going fine then i thought ,as a way to practice, to make something like given example in the book (example consists in 3 tables pet,person,person_pet and the person_pet table 'links' pets to their owners). I made this: report table +----+-------------+ | id | content | +----+-------------+ | 1 | bank robbery| | 2 | invalid | | 3 | cat on tree | +----+-------------+ notes table +-----------+--------------------+ | report_id | content | +-----------+--------------------+ | 1 | they had guns | | 3 | cat was saved | +-----------+--------------------+ wanted result +-----------+--------------------+---------------+ | report_id | report_content | report_notes | +-----------+--------------------+---------------+ | 1 | bank robbery | they had guns | | 2 | invalid | null or '' | | 3 | cat on tree | cat was saved | +-----------+--------------------+---------------+ I tried a few combinations but no success. My first thought was SELECT report.id,report.content AS report_content,note.content AS note_content FROM report,note WHERE report.id = note.report_id but this only returns the ones that have a match (would not return the invalid report). after this i tried adding IF conditions but i just made it worse. My question is, is this something i will figure out after getting past basic sql or can this be done in simple way? Anyway i would appreciate any help, i pretty much lost with this. Thank you. EDIT: i have looked into related questions but havent yet found one that solves my problem. I probably need to look into other statements such as join or something to sort this out.

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• WSDL first for existing service layer

  - by Jurgen H

  I am working on an existing Java project with a typical services - dao setup for which only a webapplication was available. My job is to add webservices on top of the services layer, but the webservices have their own functional analysis and datamodel. The functional analyses ofcource focuses on what is possible in the different service methods. As good practice demands, we used the WSDL first strategy and generated JAXB bound Java classes and a SEI for the webservices. After having implemented the webservices partially, we noticed a 70% match between the datamodel. This resulted in writing converters which take the webservice JAXB classes and map them with the service layer classes. Customer customer = new Customer(); customer.setName(wsCustomer.getName()); customer.setFirstName(wsCustomer.getFirstName(); .. This is a very obvious example, some other mappings where little more complicated. Can anyone give his best practices, experiences, solutions to this kind of situations? Are any of these frameworks usefull? http://transmorph.sourceforge.net/wiki/index.php/Main_Page http://ezmorph.sourceforge.net/ Please don't start a discussion about WSDL first vs code first.

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• Swing modal dialog refuses to close - sometimes!

  - by Zarkonnen

  // This is supposed to show a modal dialog and then hide it again. In practice, // this works about 75% of the time, and the other 25% of the time, the dialog // stays visible. // This is on Ubuntu 10.10, running: // OpenJDK Runtime Environment (IcedTea6 1.9) (6b20-1.9-0ubuntu1) // This always prints // setVisible(true) about to happen // setVisible(false) about to happen // setVisible(false) has just happened // even when the dialog stays visible. package modalproblemdemo; import java.awt.Frame; import javax.swing.JDialog; import javax.swing.SwingUtilities; public class Main { public static void main(String[] args) { final Dialogs d = new Dialogs(); new Thread() { @Override public void run() { d.show(); d.hide(); } }.start(); } static class Dialogs { final JDialog dialog; public Dialogs() { dialog = new JDialog((Frame) null, "Hello World", /*modal*/ true); dialog.setSize(400, 200); } public void show() { SwingUtilities.invokeLater(new Runnable() { public void run() { dialog.setLocationRelativeTo(null); System.out.println("setVisible(true) about to happen"); dialog.setVisible(true); }}); } public void hide() { SwingUtilities.invokeLater(new Runnable() { public void run() { System.out.println("setVisible(false) about to happen"); dialog.setVisible(false); System.out.println("setVisible(false) has just happened"); }}); } } }

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• How do you pass a generic delegate argument to a method in .NET 2.0

  - by Seth Spearman

  Hello, I have a class with a delegate declaration as follows... Public Class MyClass Public Delegate Function Getter(Of TResult)() As TResult 'the following code works. Public Shared Sub MyMethod(ByVal g As Getter(Of Boolean)) 'do stuff End Sub End Class However, I do not want to explicitly type the Getter delegate in the Method call. Why can I not declare the parameter as follows... ... (ByVal g As Getter(Of TResult)) Is there a way to do it? My end goal was to be able to set a delegate for property setters and getters in the called class. But my reading indicates you can't do that. So I put setter and getter methods in that class and then I want the calling class to set the delegate argument and then invoke. Is there a best practice for doing this. I realize in the above example that I can set set the delegate variable from the calling class...but I am trying to create a singleton with tight encapsulation. For the record, I can't use any of the new delegate types declared in .net35. Answers in C# are welcome. Any thoughts? Seth

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• How to catch unintentional function interpositioning?

  - by SiegeX

  Reading through my book Expert C Programming, I came across the chapter on function interpositioning and how it can lead to some serious hard to find bugs if done unintentionally. The example given in the book is the following: my_source.c mktemp() { ... } main() { mktemp(); getwd(); } libc mktemp(){ ... } getwd(){ ...; mktemp(); ... } According to the book, what happens in main() is that mktemp() (a standard C library function) is interposed by the implementation in my_source.c. Although having main() call my implementation of mktemp() is intended behavior, having getwd() (another C library function) also call my implementation of mktemp() is not. Apparently, this example was a real life bug that existed in SunOS 4.0.3's version of lpr. The book goes on to explain the fix was to add the keyword static to the definition of mktemp() in my_source.c; although changing the name altogether should have fixed this problem as well. This chapter leaves me with some unresolved questions that I hope you guys could answer: Does GCC have a way to warn about function interposition? We certainly don't ever intend on this happening and I'd like to know about it if it does. Should our software group adopt the practice of putting the keyword static in front of all functions that we don't want to be exposed? Can interposition happen with functions introduced by static libraries? Thanks for the help. EDIT I should note that my question is not just aimed at interposing over standard C library functions, but also functions contained in other libraries, perhaps 3rd party, perhaps ones created in-house. Essentially, I want to catch any instance of interpositioning regardless of where the interposed function resides.

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• Learning PHP - start out using a framework or no?

  - by Kevin Torrent

  I've noticed a lot of jobs in my area for PHP. I've never used PHP before, and figure if I can get more opportunities if I pick it up then it might be a good idea. The problem is that PHP without any framework is ugly and 99% of the time really bad code. All the tutorials and books I've seen are really lousy - it never shows any kind of good programming practice but always the quick and dirty kind of way of doing things. I'm afraid that trying to learn PHP this way will just imprint these bad practices in my head and make me waste time later trying to unlearn them. I've used C# in the past so I'm familiar with OOP and software design patterns and similar. Should I be trying to learn PHP by using one of the better known frameworks for it? I've looked at CakePHP, Symfony and the Zend Framework so far; Zend seems to be the most flexible without being too constraining like Cake and Symfony (although Symfony seemed less constraining than CakePHP which is trying too hard to be Ruby on Rails), but many tutorials for Zend I've seen assume you already know PHP and want to learn to use the framework. What would be my best opportunity for learning PHP, but learning GOOD PHP that uses real software engineering techniques instead of spaghetti code? It seems all the PHP books and resources either assume you are just using raw PHP and therefore showcase bade practices, or that you already know PHP and therefore don't even touch on parts of the language.

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• DB Design to store custom fields for a table

  - by Fazal

  Hi All, this question came up based on the responses I got for the question http://stackoverflow.com/questions/2785033/getting-wierd-issue-with-to-number-function-in-oracle As everyone suggested that storing Numeric values in VARCHAR2 columns is not a good practice (which I totally agree with), I am wondering about a basic Design choice our team has made and whether there are better way to design. Problem Statement : We Have many tables where we want to give certain number of custom fields. The number of required custom fields is known, but what kind of attribute is mapped to the column is available to the user E.g. I am putting down a hypothetical scenario below Say you have a laptop which stores 50 attribute values for every laptop record. Each laptop attributes are created by the some admin who creates the laptop. A user created a laptop product lets say lap1 with attributes String, String, numeric, numeric, String Second user created laptop lap2 with attributes String,numeric,String,String,numeric Currently there data in our design gets persisted as following Laptop Table Id Name field1 field2 field3 field4 field5 1 lap1 lappy lappy 12 13 lappy 2 lap2 lappy2 13 lappy2 lapp2 12 This example kind of simulates our requirement and our design Now here if somebody is lookinup records for lap2 table doing a comparison on field2, We need to apply TO_NUMBER. select * from laptop where name='lap2' and TO_NUMBER(field2) < 15 TO_NUMBER fails in some cases when query plan decides to first apply to_number instead of the other filter. QUESTION Is this a valid design? What are the other alternative ways to solve this problem One of our team mates suggested creating tables on the fly for such cases. Is that a good idea How do popular ORM tools give custom fields or flex fields handling? I hope I was able to make sense in the question. Sorry for such a long text.. This causes us to use TO_NUMBER when queryio

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• Does the pointer to free() have to point to beginning of the memory block, or can it point to the interior?

  - by Lambert

  The question is in the title... I searched but couldn't find anything. Edit: I don't really see any need to explain this, but because people think that what I'm saying makes no sense (and that I'm asking the wrong questions), here's the problem: Since people seem to be very interested in the "root" cause of all the problem rather than the actual question asked (since that apparently helps things get solved better, let's see if it does), here's the problem: I'm trying to make a D runtime library based on NTDLL.dll, so that I can use that library for subsystems other than the Win32 subsystem. So that forces me to only link with NTDLL.dll. Yes, I'm aware that the functions are "undocumented" and could change at any time (even though I'd bet a hundred dollars that wcstombs will still do the same exact thing 20 years from now, if it still exists). Yes, I know people (especially Microsoft) don't like developers linking to that library, and that I'll probably get criticized for the right here. And yes, those two points above mean that programs like chkdsk and defragmenters that run before the Win32 subsystem aren't even supposed to be created in the first place, because it's literally impossible to link with anything like kernel32.dll or msvcrt.dll and still have NT-native executables, so we developers should just pretend that those stages are meant to be forever out of our reaches. But no, I doubt that anyone here would like me to paste a few thousand lines of code and help me look through them and try to figure out why memory allocations that aren't failing are being rejected by the source code I'm modifying. So that's why I asked about a different problem than the "root" cause, even though that's supposedly known to be the best practice by the community. If things still don't make sense, feel free to post comments below! :)

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• Code Contracts: Do we have to specify Contract.Requires(...) statements redundantly in delegating me

  - by herzmeister der welten

  I'm intending to use the new .NET 4 Code Contracts feature for future development. This made me wonder if we have to specify equivalent Contract.Requires(...) statements redundantly in a chain of methods. I think a code example is worth a thousand words: public bool CrushGodzilla(string weapon, int velocity) { Contract.Requires(weapon != null); // long code return false; } public bool CrushGodzilla(string weapon) { Contract.Requires(weapon != null); // specify contract requirement here // as well??? return this.CrushGodzilla(weapon, int.MaxValue); } For runtime checking it doesn't matter much, as we will eventually always hit the requirement check, and we will get an error if it fails. However, is it considered bad practice when we don't specify the contract requirement here in the second overload again? Also, there will be the feature of compile time checking, and possibly also design time checking of code contracts. It seems it's not yet available for C# in Visual Studio 2010, but I think there are some languages like Spec# that already do. These engines will probably give us hints when we write code to call such a method and our argument currently can or will be null. So I wonder if these engines will always analyze a call stack until they find a method with a contract that is currently not satisfied? Furthermore, here I learned about the difference between Contract.Requires(...) and Contract.Assume(...). I suppose that difference is also to consider in the context of this question then?

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