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• multithreading in c#

  - by Lalit Dhake

  Hi, I have console application. In that i have some process that fetch the data from database through different layers ( business and Data access). stores the fetched data in respective objects. Like if data is fetched for student then this data will store (assigned ) to Student object. same for school. and them a delegate call the certain method that generates outputs as per requirement. This process will execute many times say 10 times. Ok? I want to run simultaneously this process. not one will start, it will finish and then second will start. I want after starting 1'st process, just 2'nd , 3rd....10'th must be start. Means it should be multithreading. how can i achieve this ? is that will give me error while connection with data base open and close ? I have tried this concept . but when thread 1'st is starting then data will fetched for thread 1 will stored in its respective (student , school) objects. ok? when simultaneous 2'nd thread starts , but the data is changing of 1'st object ,while control flowing in program. What have to do?

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• Recommended (remote) backup technique for SQL Compact?

  - by Cool Jon

  Hello. Is there a generally recommended approach to backing up an SQL CE/SQLite database over the Internet? The client source is .NET/Windows based, the backup destination runs Ubuntu. I am using a small SQL CE database and have been trying to figure out the most reasonable approach to doing this. The file size (in terms of transfer time/bandwidth) isn't a big deal. I had a look around, and so far the things I've given thought are: Online backup services (Dropbox, Mozy) Opening an FTP/SFTP connection Writing a custom protocol with public/private keys Unsure regarding #1 because I doubt they would like it if somebody transferred gigabytes of data using a POST; and they do not seem to offer native (or .NET) APIs. FTP/SFTP seems risky in terms of security and privileges (as the password/key would need to be stored on the client side). With the right user group/user privileges this may work. Custom protocol seems overkill, which is why I am hoping somebody has already defined a reasonable API for language/platform-independent backups over the Internet. Any hints S.O.?

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• accessing $_SESSION when using file_get_contents in PHP

  - by hairdresser-101

  I have a page called send.email.php which sends an email - pretty simple stuff - I pass an order id, it creates job request and sends it out. This works fine when used in the context I developed it (Use javascript to make an AJAX call to the URL and pass the order_id as a query parameter) I am now trying to reuse the exact same page in another application however I am calling it using php file_get_contents($base_url.'admin/send.email.php?order_id='.$order_id). When I call the page this way, the $_SESSION array is empty isempty() = 1. Is this because I am initiating a new session using file_get_contents and the values I stored in the $_SESSION on login are not available to me within there? -- Thanks for the feedback. It makes sense that the new call doesn't have access to the existing session... New problem though: I now get: failed to open stream: HTTP request failed! When trying to execute: $opts = array('http' => array('header'=> 'Cookie: ' . $_SERVER['HTTP_COOKIE']."\r\n")); $context = stream_context_create($opts); $contents = file_get_contents($base_url.'admin/send.sms.php?order_id='.order_id, false, $context); YET, the URL works fine if I call it as: (It just doesn't let me access session) $result file_get_contents($base_url.'admin/send.sms.php?order_id='.$order_id);

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• How to use Object.GetHashCode() on a type that overrides GetHashCode()

  - by Jimmy

  Hi, I have a class A that implements IEquatable<, using its fields (say, A.b and A.c) for implementing/overriding Equals() and overriding GetHashCode(), and everything works fine, 99% of the time. Class A is part of a hierarchy (class B, C) that all inherit from interface D; they can all be stored together in a dictionary Dictionary, thus it's convenient when they all carry their own default Equals()/GetHashCode(). However, while constructing A I sometime need to do some work to get the values for A.b and A.c; while that's happening, I want to store a reference to the instance that's being built. In that case, I don't want to use the default Equals()/GetHashCode() overrides provided by A. Thus, I was thinking of implementing a ReferenceEqualityComparer, that's meant to force the use of Object's Equals()/GetHashCode(): private class ReferenceEqualityComparer<T> : IEqualityComparer<T> { #region IEqualityComparer<T> Members public bool Equals(T x, T y) { return System.Object.ReferenceEquals(x, y); } public int GetHashCode(T obj) { // what goes here? I want to do something like System.Object.GetHashCode(obj); } #endregion } The question is, since A overrides Object.GetHashCode(), how can I (outside of A) call Object.GetHashCode() for an instance of A? One way of course would be for A to not implement IEquatable< and always supply an IEqualityComparer< to any dictionary that I create, but I'm hoping for a different answer. Thanks

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• iPhone SQLite Password Field Encryption

  - by Louis Russell

  Good Afternoon Guys and Girls, Hopefully this will be a quick and easy question. I am building an App that requires the user to input their login details for an online service that it links to. Multiple login details can be added and saved as the user may have several accounts that they would like to switch between. These details will be stored in an SQLite database and will contain their passwords. Now the questions are: 1: Should these passwords be encrypted in the database? My instinct would say yes but then I do not know how secure the device and system is and if this is necessary. 2: If they should be encrypted what should I use? I think encrypting the whole database file sounds a bit over-kill so should I just encrypt the password before saving it to the database? If this is case what could I use to achieve this? I have found reference to a "crypt(3)" but am having trouble finding much about it or how to implement it. I eagerly await your replies!

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• How can I turn a column name into a result value in SQL Server?

  - by Brennan

  I have a table which has essentially boolean values in a legacy database. The column names are stored as string values in another table so I need to match the column names of one table to a string value in another table. I know there has to be a way to do this directly with SQL in SQL Server but it is beyond me. My initial thought was to use PIVOT but it is not enabled by default and enabling it would likely be a difficult process with pushing that change to the Production database. I would prefer to use what is enabled by default. I am considering using COALESCE to translate the boolean value to the string that value that I need. This will be a manual process. I think I will also use a table variable to insert the results of the first query into that variable and use those results to do the second query. I still have the problem that the columns are on a single row so I wish I could easily pivot the values to put the column names in the result set as strings. But if I could easily do that I could easily write the query with a sub-select. Any tips are welcome.

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• Deriving an HTMLElement Object from jQuery Object

  - by Jasconius

  I'm doing a fairly exhaustive series of DOM manipulations where a few elements (specifically form elements) have some events. I am dynamically creating (actually cloning from a source element) several boxes and assigning a change() event to them. The change event executes, and within the context of the event, "this" is the HTML Element Object. What I need to do at this point however is determine a contact for this HTML Element Object. I have these objects stored already as jQuery entities in assorted arrays, but obviously [HTMLElement Object] != [Object Object] And the trick is that I cannot cast $(this) and make a valid comparison since that would create a new object and the pointer would be different. So... I've been banging my head against this for a while. In the past I've been able to circumvent this problem by doing an innerHTML comparison, but in this case the objects I am comparing are 100% identical, just there's lots of them. Therefore I need a solid comparison. This would be easy if I could somehow derive the HTMLElement object from my originating jQuery object. Thoughts, other ideas? Help. :(

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• Automatic Adjusting Range Table

  - by Bradford

  I have a table with a start date range, an end date range, and a few other additional columns. On input of a new record, I want to automatically adjust any overlapping date ranges (shrinking them to allow for the new input). I also want to ensure that no overlapping records can accidentally be inserted into this table. I'm using Oracle and Java for my application code. How should I enforce the prevention of overlapping date ranges and also allow for automatically adjusting overlapping ranges? Should I create an AFTER INSERT trigger, with a dbms_lock to serialize access, to prevent the overlapping data. Then in Java, apply the logic to auto adjust everything? Or should that part be in PL/SQL in stored procedure call? This is something that we need for a couple other tables so it'd be nice to abstract. If anyone has something like this already written, please share :) I did find this reference: http://asktom.oracle.com/pls/asktom/f?p=100:11:0::::P11_QUESTION_ID:474221407101 Here's an example of how each of the 4 overlapping cases should be handled for adjustment on insert: = Example 1 = In DB (Start, End, Value): (0, 10, 'X') **(30, 100, 'Z') (200, 500, 'Y') Input (20, 50, 'A') Gives (0, 10, 'X') **(20, 50, 'A') **(51, 100, 'Z') (200, 500, 'Y') = Example 2 = In DB (Start, End, Value): (0, 10, 'X') **(30, 100, 'Z') (200, 500, 'Y') Input (40, 80, 'A') Gives (0, 10, 'X') **(30, 39, 'Z') **(40, 80, 'A') **(81, 100, 'Z') (200, 500, 'Y') = Example 3 = In DB (Start, End, Value): (0, 10, 'X') **(30, 100, 'Z') (200, 500, 'Y') Input (50, 120, 'A') Gives (0, 10, 'X') **(30, 49, 'Z') **(50, 120, 'A') (200, 500, 'Y') = Example 4 = In DB (Start, End, Value): (0, 10, 'X') **(30, 100, 'Z') (200, 500, 'Y') Input (20, 120, 'A') Gives (0, 10, 'X') **(20, 120, 'A') (200, 500, 'Y') The algorithm is as follows: given range = g; input range = i; output range set = o if i.start <= g.start if i.end >= g.end o_1 = i else o_1 = i o_2 = (o.end + 1, g.end) else if i.end >= g.end o_1 = (g.start, i.start - 1) o_2 = i else o_1 = (g.start, i.start - 1) o_2 = i o_3 = (i.end + 1, i.end)

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• Programmer Puzzle: Encoding a chess board state throughout a game

  - by Andrew Rollings

  Not strictly a question, more of a puzzle... Over the years, I've been involved in a few technical interviews of new employees. Other than asking the standard "do you know X technology" questions, I've also tried to get a feel for how they approach problems. Typically, I'd send them the question by email the day before the interview, and expect them to come up with a solution by the following day. Often the results would be quite interesting - wrong, but interesting - and the person would still get my recommendation if they could explain why they took a particular approach. So I thought I'd throw one of my questions out there for the Stack Overflow audience. Question: What is the most space-efficient way you can think of to encode the state of a chess game (or subset thereof)? That is, given a chess board with the pieces arranged legally, encode both this initial state and all subsequent legal moves taken by the players in the game. No code required for the answer, just a description of the algorithm you would use. EDIT: As one of the posters has pointed out, I didn't consider the time interval between moves. Feel free to account for that too as an optional extra :) EDIT2: Just for additional clarification... Remember, the encoder/decoder is rule-aware. The only things that really need to be stored are the player's choices - anything else can be assumed to be known by the encoder/decoder. EDIT3: It's going to be difficult to pick a winner here :) Lots of great answers!

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• Compare new Integer Objects in ArrayList Question

  - by thechiman

  I am storing Integer objects representing an index of objects I want to track. Later in my code I want to check to see if a particular object's index corresponds to one of those Integers I stored earlier. I am doing this by creating an ArrayList and creating a new Integer from the index of a for loop: ArrayList<Integer> courseselectItems = new ArrayList(); //Find the course elements that are within a courseselect element and add their indicies to the ArrayList for(int i=0; i<numberElementsInNodeList; i++) { if (nodeList.item(i).getParentNode().getNodeName().equals("courseselect")) { courseselectItems.add(new Integer(i)); } } I then want to check later if the ArrayList contains a particular index: //Cycle through the namedNodeMap array to find each of the course codes for(int i=0; i<numberElementsInNodeList; i++) { if(!courseselectItems.contains(new Integer(i))) { //Do Stuff } } My question is, when I create a new Integer by using new Integer(i) will I be able to compare integers using ArrayList.contains()? That is to say, when I create a new object using new Integer(i), will that be the same as the previously created Integer object if the int value used to create them are the same? I hope I didn't make this too unclear. Thanks for the help!

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• Can I include a NSUserDefault password test in AppDelegate to load a loginView?

  - by Michael Robinson

  I have a name and password in NSUserDefaults for login. I want to place a test in my AppDelegate.m class to test for presence and load a login/signup loginView.xib modally if there is no password or name stored in the app. Here is the pulling of the defaults: -(void)refreshFields { NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults]; usernameLabel.text = [defaults objectForKey:kUsernameKey]; passwordLabel.text = [defaults objectForKey:kPasswordKey]; Here is the tabcontroller loading part: - (void)applicationDidFinishLaunching:(UIApplication *)application { firstTab = [[FirstTab alloc] initWithStyle:UITableViewStylePlain]; UINavigationController *firstNavigationController = [[UINavigationController alloc] initWithRootViewController:firstTab]; [firstTab release]; secondTab = // EDITED FOR SPACE thirdTab = // EDITED FOR SPACE tabBarController = [[UITabBarController alloc] init]; tabBarController.viewControllers = [NSArray arrayWithObjects:firstNavigationController, secondNavigationController, thirdNavigationController, nil]; [window addSubview:tabBarController.view]; [firstNavigationController release]; [secondNavigationController release]; [thirdNavigationController release]; [self logout]; [window makeKeyAndVisible]; Here is where the loginView.xib loads automatically: - (void)logout { loginViewController = [[LoginViewController alloc] initWithNibName:@"LoginView" bundle:nil]; UINavigationController *loginNavigationController = [[UINavigationController alloc] initWithRootViewController:loginViewController]; [loginViewController release]; [tabBarController presentModalViewController:loginNavigationController animated:YES]; [loginNavigationController release]; } I want to replace the above autoload with a test similar to below (that works) using IF-ELSE - (void)logout { if ([usernameLabel.text length] == 0 || [passwordLabel.text length] == 0) { loginViewController = [[LoginViewController alloc] initWithNibName:@"LoginView" bundle:nil]; UINavigationController *loginNavigationController = [[UINavigationController alloc] initWithRootViewController:loginViewController]; [loginViewController release]; [tabBarController presentModalViewController:loginNavigationController animated:YES]; [loginNavigationController release]; }else { [window addSubview:tabBarController.view];} Thanks in advance, I'm totally lost on this.

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• VB.NET invalid cast exception

  - by user127147

  Hi there, I have a simple application to store address details and edit them. I have been away from VB for a few years now and need to refreash my knowledge while working to a tight deadline. I have a general Sub responsible for displaying a form where user can add contact details (by pressing button add) and edit them (by pressing button edit). This sub is stored in a class Contact. The way it is supposed to work is that there is a list with all the contacts and when new contact is added a new entry is displayed. If user wants to edit given entry he or she selects it and presses edit button Public Sub Display() Dim C As New Contact C.Cont = InputBox("Enter a title for this contact.") C.Fname = frmAddCont.txtFName.Text C.Surname = frmAddCont.txtSName.Text C.Address = frmAddCont.txtAddress.Text frmStart.lstContact.Items.Add(C.Cont.ToString) End Sub I call it from the form responsible for adding new contacts by Dim C As New Contact C.Display() and it works just fine. However when I try to do something similar using the edit button I get errors - "Unable to cast object of type 'System.String' to type 'AddressBook.Contact'." Dim C As Contact If lstContact.SelectedItem IsNot Nothing Then C = lstContact.SelectedItem() C.Display() End If I think it may be something simple however I wasn't able to fix it and given short time I have I decided to ask for help here. Thank you

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• What Is The Proper Location For One-Offs In VCS Repos?

  - by Joe Clark

  I have recently started using Mercurial as our VCS. Over the years, I have used RCS, CVS, and - for the last 5 years - SVN. Back 13 years ago, when I primarily used CVS and RCS, large projects went into CVS and one-offs were edited in place on the specific server and stored in RCS. This worked well as the one-offs were usually specific to the server and the servers were backed up nightly. Jump forward a decade and a lot of the one-off scripts became less centralized - they might be needed on any server at some random time. This was also OK, because now I was a begrudging SVN user. Everything (except for docs) got dumped into one repo. Jump to 2010. Now I am using Mercurial and am putting large projects in their own repo again. But what to do with the one-offs? The options as I see them: A repo for each script. It seems a bit cluttered to create a repo for every one page script that might get ran once a year. RCS Not an option. There are many possible servers that might need a specific script. Continuing to use SVN just for one-offs. No. There no advantage I see over the next option. Create a repo in Mercurial named "one-offs". This seems the most workable. The last option seems the best to me - however; is there a best practice regarding this? You also might be wondering if these scripts are truly one-offs if they will be reused. Some of them may be reused 6 months or a year from now - some, never. However, nearly all of them involve several man-hours of work due to either complex logic or extensive error checking. Simply discarding them is not efficient.

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• Multiple undo managers for a text view

  - by Rui Pacheco

  Hi, I've a text view that gets its content from an attributed string stored in a model object. I list several of these model objects in a drawer and when the user clicks on one the text view swaps its content. I now need to also swap the undo manager for the text view. I initialise an undo manager on my model object and use undoManagerForTextView to return it to the text view, but something's not quite right. Strategically placed logging statements show me that everything's working as planned: on startup a new model object is initialised correctly and a non-null undo manager is always pulled by the text view. But when it comes to actually doing undo, I just can't get the behaviour I want. I open a window, type something and press cmd+z, and undo works. I open a window, type something, select a new model on the table, type something, go back to the first model and try to undo and all I get is a beep. Something on the documentation made me raise an eyebrow, as it would mean that I can't have undo with several model objects: The default undo and redo behavior applies to text fields and text in cells as long as the field or cell is the first responder (that is, the focus of keyboard actions). Once the insertion point leaves the field or cell, prior operations cannot be undone.

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• Reading from serial port with Boost Asio?

  - by trikri

  Hi! I'm going to check for incoming messages (data packages) on the serial port, using Boost Asio. Each message will start with a header that is one byte long, and will specify which type of the message has been sent. Each different type of message has an own length. The function I'm about to write should check for new incoming messages continually, and when it finds one it should read it, and then some other function should parse it. I thought that the code might look something like this: void check_for_incoming_messages() { boost::asio::streambuf response; boost::system::error_code error; std::string s1, s2; if (boost::asio::read(port, response, boost::asio::transfer_at_least(0), error)) { s1 = streambuf_to_string(response); int msg_code = s1[0]; if (msg_code < 0 || msg_code >= NUM_MESSAGES) { // Handle error, invalid message header } if (boost::asio::read(port, response, boost::asio::transfer_at_least(message_lengths[msg_code]-s1.length()), error)) { s2 = streambuf_to_string(response); // Handle the content of s1 and s2 } else if (error != boost::asio::error::eof) { throw boost::system::system_error(error); } } else if (error != boost::asio::error::eof) { throw boost::system::system_error(error); } } Is boost::asio::streambuf is the right thing to use? And how do I extract the data from it so I can parse the message? I also want to know if I need to have a separate thread which only calls this function, so that it get called more often? Isn't there a risk for loosing data in between two calls to the function otherwise, because so much data comes in that it can't be stored in the serial ports memory? I'm using Qt as a widget toolkit and I don't really know how long time it needs to process all it's events.

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• Database design for invoices, invoice lines & revisions

  - by FreshCode

  I'm designing the 2nd major iteration of a relational database for a franchise's CRM (with lots of refactoring) and I need help on the best database design practices for storing job invoices and invoice lines with a strong audit trail of any changes made to each invoice. Current schema Invoices Table InvoiceId (int) // Primary key JobId (int) StatusId (tinyint) // Pending, Paid or Deleted UserId (int) // auditing user Reference (nvarchar(256)) // unique natural string key with invoice number Date (datetime) Comments (nvarchar(MAX)) InvoiceLines Table LineId (int) // Primary key InvoiceId (int) // related to Invoices above Quantity (decimal(9,4)) Title (nvarchar(512)) Comment (nvarchar(512)) UnitPrice (smallmoney) Revision schema InvoiceRevisions Table RevisionId (int) // Primary key InvoiceId (int) JobId (int) StatusId (tinyint) // Pending, Paid or Deleted UserId (int) // auditing user Reference (nvarchar(256)) // unique natural string key with invoice number Date (datetime) Total (smallmoney) Schema design considerations 1. Is it sensible to store an invoice's Paid or Pending status? All payments received for an invoice are stored in a Payments table (eg. Cash, Credit Card, Cheque, Bank Deposit). Is it meaningful to store a "Paid" status in the Invoices table if all the income related to a given job's invoices can be inferred from the Payments table? 2. How to keep track of invoice line item revisions? I can track revisions to an invoice by storing status changes along with the invoice total and the auditing user in an invoice revision table (see InvoiceRevisions above), but keeping track of an invoice line revision table feels hard to maintain. Thoughts? 3. Tax How should I incorporate sales tax (or 14% VAT in SA) when storing invoice data?

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• Asp.net Login Status Question: It Aint Working

  - by contactmatt

  I'm starting to use Role Management in my website, and I'm current following along on the tutorial from http://www.asp.net/Learn/Security/tutorial-02-vb.aspx . I'm having a problem with the asp:LoginStatus control. It is not telling me that I am currently logged in after a successful login. This can't be true because after successfully logging in, my LoggedInTemplate is shown. The username and passwords are simply stored in a array. Heres the Login.aspx page code. Protected Sub btnLogin_Click(ByVal sender As Object, ByVal e As System.EventArgs) _ Handles btnLogin.Click ' Three valid username/password pairs: Scott/password, Jisun/password, and Sam/password. Dim users() As String = {"Scott", "Jisun", "Sam"} Dim passwords() As String = {"password", "password", "password"} For i As Integer = 0 To users.Length - 1 Dim validUsername As Boolean = (String.Compare(txtUserName.Text, users(i), True) = 0) Dim validPassword As Boolean = (String.Compare(txtPassword.Text, passwords(i), False) = 0) If validUsername AndAlso validPassword Then FormsAuthentication.RedirectFromLoginPage(txtUserName.Text, chkRemember.Checked) End If Next ' If we reach here, the user's credentials were invalid lblInvalid.Visible = True End Sub Here is the content place holder on the master page specifically designed to hold Login Information. On successfull login, the page is redirected to '/Default.aspx', and the LoggedIn Template below is shown...but the status says Log In. <asp:ContentPlaceHolder Id="LoginContent" runat="server"> <asp:LoginView ID="LoginView1" runat="server"> <LoggedInTemplate> Welcome back, <asp:LoginName ID="LoginName1" runat="server" />. </LoggedInTemplate> <AnonymousTemplate> Hello, stranger. </AnonymousTemplate> </asp:LoginView> <br /> <asp:LoginStatus ID="LoginStatus1" runat="server" LogoutAction="Redirect" LogoutPageUrl="~/Logout.aspx" /> </asp:ContentPlaceHolder> Forms authentication is enabled. I'm not sure what to do about this :o.

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• rails search nested set (categories and sub categories)

  - by bob

  Hello, I am using the http://github.com/collectiveidea/awesome_nested_set awesome nested set plugin and currently, if I choose a sub category as my category_id for an item, I can not search by its parent. Category.parent Category.Child I choose Category.child as the category that my item is in. So now my item has category_id of 4 stored in it. If I go to a page in my rails application, lets say teh Category page and I am on the Category.parent's page, I want to show products that have category_id's of all the descendants as well. So ideally i want to have a find method that can take into account the descendants. You can get the descendants of a root by calling root.descendants (a built in plugin method). How would I go about making it so I can query a find that gets the descendants of a root instead of what its doing now which is binging up nothing unless the product had a specific category_id of the Category.parent. I hope I am being clear here. I either need to figure out a way to create a find method or named_scope that can query and return an array of objects that have id's corresponding tot he descendants of a root OR if I have any other options, what are they? I thought about creating a field in my products table like parent_id which can keep track of the parent so i can then create two named scopes one finding the parent stuff and one finding the child stuff and chaining them. I know I can create a named scope for each child and chain them together for multiple children but this seems a very tedious process and also, if you add more children, you would need to specify more named scopes.

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• The woes of (sometimes) storing "date only" in datetimes

  - by Heinzi

  We have two fields from and to (of type datetime), where the user can store the begin time and the end time of a business trip, e.g.: From: 2010-04-14 09:00 To: 2010-04-16 16:30 So, the duration of the trip is 2 days and 7.5 hours. Often, the exact times are not known in advance, so the user enters the dates without a time: From: 2010-04-14 To: 2010-04-16 Internally, this is stored as 2010-04-14 00:00 and 2010-04-16 00:00, since that's what most modern class libraries (e.g. .net) and databases (e.g. SQL Server) do when you store a "date only" in a datetime structure. Usually, this makes perfect sense. However, when entering 2010-04-16 as the to date, the user clearly did not mean 2010-04-16 00:00. Instead, the user meant 2010-04-16 24:00, i.e., calculating the duration of the trip should output 3 days, not 2 days. I can think of a few (more or less ugly) workarounds for this problem (add "23:59" in the UI layer of the to field if the user did not enter a time component; add a special "dates are full days" Boolean field; store "2010-04-17 00:00" in the DB but display "2010-04-16 24:00" to the user if the time component is "00:00"; ...), all having advantages and disadvantages. Since I assume that this is a fairly common problem, I was wondering: Is there a "standard" best-practice way of solving it? If there isn't, have you experienced a similar requirement, how did you solve it and what were the pros/cons of that solution?

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• WCF Double Hop questions about Security and Binding.

  - by Ken Maglio

  Background information: .Net Website which calls a service (aka external service) facade on an app server in the DMZ. This external service then calls the internal service which is on our internal app server. From there that internal service calls a stored procedure (Linq to SQL Classes), and passes the serialized data back though to the external service, and from there back to the website. We've done this so any communication goes through an external layer (our external app server) and allows interoperability; we access our data just like our clients consuming our services. We've gotten to the point in our development where we have completed the system and it all works, the double hop acts as it should. However now we are working on securing the entire process. We are looking at using TransportWithMessageCredentials. We want to have WS2007HttpBinding for the external for interoperability, but then netTCPBinding for the bridge through the firewall for security and speed. Questions: If we choose WS2007HttpBinding as the external services binding, and netTCPBinding for the internal service is this possible? I know WS-* supports this as does netTCP, however do they play nice when passing credential information like user/pass? If we go to Kerberos, will this impact anything? We may want to do impersonation in the future. If you can when you answer post any reference links about why you're answering the way you are, that would be very helpful to us. Thanks!

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• Violating 1st normal form, is it okay for my purpose?

  - by Nick

  So I'm making a running log, and I have the workouts stored as entries in a table. For each workout, the user can add intervals (which consist of a time and a distance), so I have an array like this: [workout] => [description] => [comments] => ... [intervals] => [0] => [distance] => 200m [time] => 32 [1] => [distance] => 400m [time] => 65 ... I'm really tempted to throw the "intervals" array into serialize() or json_encode() and put it in an "intervals" field in my table, however this violates the principles of good database design (which, incidentally, I know hardly anything about). Is there any disadvantage to doing this? I never plan on querying my table based on the contents of "intervals". Creating a separate table just for intervals seems like a lot of unnecessary complexity, so if anyone with more experience has had a situation like this, what route did you take and how did it work out?

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• How to convert an InputStream to a DataHandler?

  - by pcorey

  I'm working on a java web application in which files will be stored in a database. Originally we retrieved files already in the DB by simply calling getBytes on our result set: byte[] bytes = resultSet.getBytes(1); ... This byte array was then converted into a DataHandler using the obvious constructor: dataHandler=new DataHandler(bytes,"application/octet-stream"); This worked great until we started trying to store and retrieve larger files. Dumping the entire file contents into a byte array and then building a DataHandler out of that simply requires too much memory. My immediate idea is to retrieve a stream of the data in the database with getBinaryStream and somehow convert that InputStream into a DataHandler in a memory-efficient way. Unfortunately it doesn't seem like there's a direct way to convert an InputStream into a DataHandler. Another idea I've been playing with is reading chunks of data from the InputStream and writing them to the OutputStream of the DataHandler. But... I can't find a way to create an "empty" DataHandler that returns a non-null OutputStream when I call getOutputStream... Has anyone done this? I'd appreciate any help you can give me or leads in the right direction.

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• PostgreSQL: Auto-partition a table

  - by Adam Matan

  Hi, I have a huge database which holds pairs of numbers (A,B), each ranging from 0 to 10,000 and stored as floats. e.g., (1, 9984.4), (2143.44, 124.243), (0.55, 0), ... Since the PostgreSQL table which stores these pairs grew quite large, I have decided to partition it into inheriting sub-tables. I intend to create 100 such tables, each storing a range of 1000x1000. The problem is that these numbers tend to come in large chunks of nearby numbers. It means that in the future, some tables will be nearly empty and some will hold a very large portion of the database. Unfortunately, the distribution of future pairs is yet unknown. I am looking for a way to automatically repartition my table. That means that if a certain subtable holds more than a specific number of pairs, it will be automatically partitioned into four sub-sub tables, and so on. My questions are: Is recursive partitioning and inheritance possible in PostgreSQL 8.3? Will indexes and query plans understand it? What's the best way to split a subtable once it grew too large? I should point out that this isn't a live database, so a downtime of few hours every week is totally acceptable. Thanks in advance, Adam

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• Why so much stack space used for each recursion?

  - by Harvey

  I have a simple recursive function RCompare() that calls a more complex function Compare() which returns before the recursive call. Each recursion level uses 248 bytes of stack space which seems like way more than it should. Here is the recursive function: void CMList::RCompare(MP n1) // RECURSIVE and Looping compare function { auto MP ne=n1->mf; while(StkAvl() && Compare(n1=ne->mb)) RCompare(n1); // Recursive call ! } StkAvl() is a simple stack space check function that compares the address of an auto variable to the value of an address near the end of the stack stored in a static variable. It seems to me that the only things added to the stack in each recursion are two pointer variables (MP is a pointer to a structure) and the stuff that one function call stores, a few saved registers, base pointer, return address, etc., all 32-bit (4 byte) values. There's no way that is 248 bytes is it? I don't no how to actually look at the stack in a meaningful way in Visual Studio 2008. Thanks

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• Where are tables in Mnesia located?

  - by Sanoj

  I try to compare Mnesia with more traditional databases. As I understand it tables in Mnesia can be located to: ram_copies - tables are stored in RAM only, so no durability as in ACID. disc_copies - tables are located on disc and a copy is located in RAM, so the table can not be bigger than the available memory? disc_only_copies - tables are located to disc only, so no caching in memory and worse performance? And the size of the table are limited to the size of dets or the table has to be fragmented. So if I want the performance of doing reads from RAM and the durability of writes to disc, then the size of the tables are very limited compared to a traditional RDBMS like MySQL or PostgreSQL. I know that Mnesia aren't meant to replace traditional RDBMS:s, but can it be used as a big RDBMS or do I have to look for another database? The server I will use is a VPS with limited amount of memory, around 512MB, but I want good database performance. Are disc_copies and the other types of tables in Mnesia so limited as I have understood?

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