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  • How to minimize total cost of shortest path tree

    - by Michael
    I have a directed acyclic graph with positive edge-weights. It has a single source and a set of targets (vertices furthest from the source). I find the shortest paths from the source to each target. Some of these paths overlap. What I want is a shortest path tree which minimizes the total sum of weights over all edges. For example, consider two of the targets. Given all edge weights equal, if they share a single shortest path for most of their length, then that is preferable to two mostly non-overlapping shortest paths (fewer edges in the tree equals lower overall cost). Another example: two paths are non-overlapping for a small part of their length, with high cost for the non-overlapping paths, but low cost for the long shared path (low combined cost). On the other hand, two paths are non-overlapping for most of their length, with low costs for the non-overlapping paths, but high cost for the short shared path (also, low combined cost). There are many combinations. I want to find solutions with the lowest overall cost, given all the shortest paths from source to target. Does this ring any bells with anyone? Can anyone point me to relevant algorithms or analogous applications? Cheers!

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  • Remove Duplicates from List of HashMap Entries

    - by HonorGod
    I have a List<HashMap<String,Object>> which represents a database where each list record is a database row. I have 10 columns in my database. There are several rows where the values of 2 particular columns are equals. I need to remove the duplicates from the list after the list is updated with all the rows from database. What is the efficient way? FYI - I am not able to do distinct while querying the database, because the GroupName is added at a later stage to the Map after the database is loaded. And since Id column is not primary key, once you add GroupName to the Map. You will have duplicates based on Id + GroupName combination! Hope my question makes sense. Let me know if we need more clarification.

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  • Overloading assignment operator in C++

    - by jasonline
    As I've understand, when overloading operator=, the return value should should be a non-const reference. A& A::operator=( const A& ) { // check for self-assignment, do assignment return *this; } It is non-const to allow non-const member functions to be called in cases like: ( a = b ).f(); But why should it return a reference? In what instance will it give a problem if the return value is not declared a reference, let's say return by value?

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  • sql locking on silverlight app

    - by immuner
    Hi, i am not sure if this is the correct term, but this is what id like to do: I have an application that uses a mssql database. This application can operate in 3 modes. mode 1) user does not alter, but only read the database mode 2) user can add rows (one at a time) onto a table in the database mode 3) user can alter several tables in the database (one person at a time) question 1) how can i ensure that when a user in in mode 3 that the database will "lock" and all logged in users who operate in mode 2 or mode 3 will not be able to change the database until he finishes? question 2) how can i ensure that while there are several users in mode 2, that there will be no conflict while they all update the table? my guess here, is that before adding a new row, you make a server query for the table's current unique keys and add the new entry. will this be safe enough though? Thanks

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  • Use a folder of xml files as data source for nhibernate

    - by Bart Van Eyndhoven
    I'm going to start writing NUnit tests for a few classes in my project. A certain number of these classes use data gathered through nhibernate from a sql server 2008 database. The part of the program I'm about to test is very specific (and complicated). Therefore I have made a folder of xml files. Combined, the xml files could result in the database structure. I mean each xml file corresponds to a table in the database. The data in the xml files is also consistent with the database. Is there a way to use this folder of xml files as data source for nhibernate? I mean: can I use nhibernate to gather my test data (wich I have specifically chosen) instead of data from the database? In this way, I could usefully test this component without corrrupting the (test) database for future tests.

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  • Mocking a concrete class : templates and avoiding conditional compilation

    - by AshirusNW
    I'm trying to testing a concrete object with this sort of structure. class Database { public: Database(Server server) : server_(server) {} int Query(const char* expression) { server_.Connect(); return server_.ExecuteQuery(); } private: Server server_; }; i.e. it has no virtual functions, let alone a well-defined interface. I want to a fake database which calls mock services for testing. Even worse, I want the same code to be either built against the real version or the fake so that the same testing code can both: Test the real Database implementation - for integration tests Test the fake implementation, which calls mock services To solve this, I'm using a templated fake, like this: #ifndef INTEGRATION_TESTS class FakeDatabase { public: FakeDatabase() : realDb_(mockServer_) {} int Query(const char* expression) { MOCK_EXPECT_CALL(mockServer_, Query, 3); return realDb_.Query(); } private: // in non-INTEGRATION_TESTS builds, Server is a mock Server with // extra testing methods that allows mocking Server mockServer_; Database realDb_; }; #endif template <class T> class TestDatabaseContainer { public: int Query(const char* expression) { int result = database_.Query(expression); std::cout << "LOG: " << result << endl; return result; } private: T database_; }; Edit: Note the fake Database must call the real Database (but with a mock Server). Now to switch between them I'm planning the following test framework: class DatabaseTests { public: #ifdef INTEGRATION_TESTS typedef TestDatabaseContainer<Database> TestDatabase ; #else typedef TestDatabaseContainer<FakeDatabase> TestDatabase ; #endif TestDatabase& GetDb() { return _testDatabase; } private: TestDatabase _testDatabase; }; class QueryTestCase : public DatabaseTests { public: void TestStep1() { ASSERT(GetDb().Query(static_cast<const char *>("")) == 3); return; } }; I'm not a big fan of that compile-time switching between the real and the fake. So, my question is: Whether there's a better way of switching between Database and FakeDatabase? For instance, is it possible to do it at runtime in a clean fashion? I like to avoid #ifdefs. Also, if anyone has a better way of making a fake class that mimics a concrete class, I'd appreciate it. I don't want to have templated code all over the actual test code (QueryTestCase class). Feel free to critique the code style itself, too. You can see a compiled version of this code on codepad.

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  • Connecting to 3rd party databse in Joomla!?

    - by Michael
    I need to connect to another database in Joomla! that's on another server. This is for a plugin and I need to pull some data from a table. Now what I don't want is to use this database to run Joomla!, I already have Joomla! installed and running on its own database on its server but I want to connect to another database (ON TOP of the current one) to pull some data, then disconnect from that 3rd party database - all while keeping the original Joomla database connection in tact.

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  • Extending mysqli and using multiple classes

    - by Mikk
    Hi, I'm new to PHP oop stuff. I'm trying to create class database and call other classes from it. Am I doing it the right way? class database: class database extends mysqli { private $classes = array(); public function __construct() { parent::__construct('localhost', 'root', 'password', 'database'); if (mysqli_connect_error()) { $this->error(mysqli_connect_errno(), mysqli_connect_error()); } } public function __call($class, $args) { if (!isset($this->classes[$class])) { $class = 'db_'.$class; $this->classes[$class] = new $class(); } return $this->classes[$class]; } private function error($eNo, $eMsg) { die ('MySQL error: ('.$eNo.': '.$eMsg); } } class db_users: class db_users extends database { public function test() { echo 'foo'; } } and how I'm using it $db = new database(); $db->users()->test(); Is it the right way or should it be done another way? Thank you.

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  • How to skip to next iteration in jQuery.each() util?

    - by Josh
    I'm trying to iterate through an array of elements. jQuery's documentation says: jquery.Each() documentation Returning non-false is the same as a continue statement in a for loop, it will skip immediately to the next iteration. I've tried calling 'return non-false;' and 'non-false;' (sans return) neither of which skip to the next iteration. Instead, they break the loop. What am i missing?

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  • In SQL Server merge replication, how does reinitializing work?

    - by Craig Shearer
    I have set up a pull subscription to a merge publication in SQL Server. I use parameterized row filters on some tables. This works fine with the initial synchronization - just the rows using the filter arrive in the replicated (client) database. However, at some later point I'd like to be able to synchronize the replicated database again from the server and have new rows that match the parameterized row filters appear on the client database. The doucmentation seems to indicate that I can call Reinitialize() to do this. However, when I do try this and Synchronize again, I get an error saying that the script 'snapshot.pre' cannot be applied to the database. I've inspected the script and can see why - it's trying to drop some functions are used by the tables in the database. It would appear that for Reinitialize() to work it requires that the database be blank. Am I misunderstanding something here? Is there a way to make this work?

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  • Data Access from single table in sql server 2005 is too slow

    - by Muhammad Kashif Nadeem
    Following is the script of table. Accessing data from this table is too slow. SET ANSI_NULLS ON GO SET QUOTED_IDENTIFIER ON GO CREATE TABLE [dbo].[Emails]( [id] [int] IDENTITY(1,1) NOT NULL, [datecreated] [datetime] NULL CONSTRAINT [DF_Emails_datecreated] DEFAULT (getdate()), [UID] [nvarchar](250) COLLATE Latin1_General_CI_AS NULL, [From] [nvarchar](100) COLLATE Latin1_General_CI_AS NULL, [To] [nvarchar](100) COLLATE Latin1_General_CI_AS NULL, [Subject] [nvarchar](max) COLLATE Latin1_General_CI_AS NULL, [Body] [nvarchar](max) COLLATE Latin1_General_CI_AS NULL, [HTML] [nvarchar](max) COLLATE Latin1_General_CI_AS NULL, [AttachmentCount] [int] NULL, [Dated] [datetime] NULL ) ON [PRIMARY] Following query takes 50 seconds to fetch data. select id, datecreated, UID, [From], [To], Subject, AttachmentCount, Dated from emails If I include Body and Html in select then time is event worse. indexes are on: id unique clustered From Non unique non clustered To Non unique non clustered Tabls has currently 180000+ records. There might be 100,000 records each month so this will become more slow as time will pass. Does splitting data into two table will solve the problem? What other indexes should be there?

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  • Deployment of a .NET application making use of SQL Server 2008

    - by Victor John Saliba
    I have searched the internet thoroughly for this type of issue, there were responses but hasn't really found a concrete solution yet. I have an application which makes use of SQL Server 2008 R2 and thus it makes connections with a database file which I have set up. The application executes successfully, makes connections with the database and retrieves/inserts/updates data to and fro the database. However when I come to create a deployment project i.e. a setup project, I fail to transfer my database files to other computers and make database connections. I have checked the SQL Server 2008 prerequisite in the publish settings of the application and has also included the database files. Can anyone suggest the best way to this type of setup? Thanks

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  • Problem with testing a Windows service

    - by prateeksaluja20
    I want to make a Windows service that will access my database. My database is SQL Server 2005. Actually I am working on a website and my database is inside our server. I need to access my database every second and update the records. For that purpose I need to make a Windows service that will install into our server and perform the task. I have been accessing the database from my local machine and then running the service, but problem is I'm not sure how I can test this service. I tried to install into my local machine. It installed and then I ran the service but it did not perform the task and I think service is not able to connect with the database. There is no problem in the service nor its installer. The only issue is how to test my Windows service.

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  • MySql / Odbc connection problem

    - by Ingvald
    I'm accessing a MySql database via ODBC. It normally works fine, but if the database is stopped and restarted I have to restart my application in order to reconnect to the database. The code for accessing the database is like this: OdbcConnection connection = new OdbcConnection(connectString); OdbcCommand command = connection.CreateCommand(); command.CommandType = CommandType.Text; command.CommandText = "select * from cds"; OdbcDataAdapter dataAdapter = new OdbcDataAdapter(command); DataSet dataSet = new DataSet(); connection.Open(); dataAdapter.Fill(dataSet); connection.Close(); After a restart of the database, I get a 'MySql server has gone away' exception in dataAdapter.Fill method. Is there any way I can reconnect to the database when I detect that the connection has broken? I use VS2008 and MySql 5.1.30.

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  • SQLite/iPhone read copyright symbol

    - by Marco A
    Hi All, I am having problems reading the copyright symbol from a sqlite db that I have for my App that I am developing. I import the information manually, ie, from an excel sheet. I have tried two ways of doing it and failed with both: 1) Tried replacing the copyright symbol with "\u00ae" (unicode combination) within excel and then importing the modified file. - Result: I get the combination of \u00ae as a part of the string, it doesnt detect the unicode combination. 2) Tried leaving as it is. Importing the excel with the copyright symbol. - Result: I get a symbol that is different from the copyright, its something like an AE put together.looks like this: Æ Heres my code how I read from DB: -(void) readCategoriesFromDatabase:(NSString *) rest_input { // Init the products Array categories = [[NSMutableArray alloc] init]; // Open the database from the users filessytem rest_input = [rest_input stringByAppendingString:@"'"]; NSString *newString; newString = [@"select distinct category from food where restaurant='" stringByAppendingString:rest_input]; const char *cat_sqlStatement = [newString UTF8String]; sqlite3_stmt *cat_compiledStatement; if(sqlite3_prepare_v2(database, cat_sqlStatement, -1, &cat_compiledStatement, NULL) == SQLITE_OK) { // Loop through the results and add them to the feeds array while(sqlite3_step(cat_compiledStatement) == SQLITE_ROW) { NSString *catName = [NSString stringWithUTF8String:(char *)sqlite3_column_text(cat_compiledStatement,0)]; // Create a new product object with the data from the database Product *category = [[Product alloc] initWithName:catName]; // Add the product object to the respective Array [categories addObject:category]; [category release]; } sqlite3_finalize(cat_compiledStatement); } NSLog(@"Finished Accessing Database to gather Categories...."); } I open the DB with this function: -(void) checkAndCreateDatabase{ NSLog(@"Checking/Creating Database...."); NSFileManager *fileManager = [NSFileManager defaultManager]; success = [fileManager fileExistsAtPath:databasePath]; [fileManager removeFileAtPath:databasePath handler:nil]; NSString *databasePathFromApp = [[[NSBundle mainBundle] resourcePath] stringByAppendingPathComponent:databaseName]; [fileManager copyItemAtPath:databasePathFromApp toPath:databasePath error:nil]; [fileManager release]; if (sqlite3_open([databasePath UTF8String], &database) != SQLITE_OK) { sqlite3_close(database); database = nil; } NSLog(@"Finished Checking/Creating Database...."); } Thanks to anything that can help me out.

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  • From xcode not able to execute DISTINCT keyword for sqlite

    - by mac
    -(void) readProductsFromDatabase { // Setup the database object sqlite3 *database; // Init the animals Array products = [[NSMutableArray alloc] init]; // Open the database from the users filessytem if(sqlite3_open([databasePath UTF8String], &database) == SQLITE_OK) { NSLog(@"db opened"); // Setup the SQL Statement and compile it for faster access const char *sqlStatement = "SELECT DISTINCT productname FROM iphone "; sqlite3_stmt *compiledStatement; if(sqlite3_prepare_v2(database, sqlStatement, -1, &compiledStatement, NULL) == SQLITE_OK) { // Loop through the results and add them to the feeds array while(sqlite3_step(compiledStatement) == SQLITE_ROW) { NSLog(@"inside sqlite3 prepare"); // Read the data from the result row NSString *aName = [NSString stringWithUTF8String:(char *)sqlite3_column_text(compiledStatement, 2)]; } } // Release the compiled statement from memory sqlite3_finalize(compiledStatement); } sqlite3_close(database); } My problem is const char *sqlStatement = "SELECT DISTINCT productname FROM iphone "; This line not executing ,i am using sqlite3, thanks in advance,

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  • Is SQL Server Compact *ever* OK to use on a web server?

    - by Troy
    I'd like to host a personal database for about 500 people (1 database per person) on my web server. A person could possibly share their database with a friend or two. On my web server, I'd have some web services, perhaps for doing synchronization, and maybe even an ASP.NET Web Forms front end to the database. If I restart my IIS web server, would this likely cause database corruptions? Would this be expected to perform ok? If not Compact, should I instead use SQL Express and create a database in SQL Server for each of my 500 people?

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  • Can we use union of two sqlite databases with same tables for Core Data?

    - by Tofrizer
    Hi All, I have an iPhone Core Data app with a pre-populated sqlite "baseline" database. Can I add a second smaller sqlite database with the same tables as my pre-populated "baseline" database but with additional / complementary data such that Core Data will happily union the data from both databases and, ultimately, present to me as if it was all a single data source? Idea that I had is: 1) the "baseline" database never changes. 2) I can download the smaller "complementary" sqlite database for additional data as and when I need to (I'm assuming downloading sqlite database is allowed, please comment if otherwise). 3) Core Data is then able to union data from 1 & 2. I can then reference this unified data by calling my defined Core Data managed object model. Hope this makes sense. Thanks in advance.

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  • SQL 2008 table locked - can't work out why

    - by Mr. Flibble
    I have two databases on one SQL 2008 server. Database 1 seems to be causing a lock on a table on database 2. There no queries are running on database 1 that should affect database 2. Is this normal behaviour? When I view the running queries with this command SELECT sqltext.TEXT, req.session_id, req.status, req.command, req.cpu_time, req.total_elapsed_time/1000 [seconds] FROM sys.dm_exec_requests req CROSS APPLY sys.dm_exec_sql_text(sql_handle) AS sqltext it tells me as much, and says that the command on database 2 is suspended. I'm at a bit of a loss. What sort of things should I look at to work out why the table in database 2 is locked?

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  • How can I know when SQL Full Text Index Population is finished?

    - by GarethOwen
    We are writing unit tests for our ASP.NET application that run against a test SQL Server database. That is, the ClassInitialize method creates a new database with test data, and the ClassCleanup deletes the database. We do this by running .bat scripts from code. The classes under test are given a connection string that connects to the unit test database rather than a production database. Our problem is, that the database contains a full text index, which needs to be fully populated with the test data in order for our tests to run as expected. As far as I can tell, the fulltext index is always populated in the background. I would like to be able to either: Create the full text index, fully populated, with a synchronous (transact-SQL?) statement, or Find out when the fulltext population is finished, is there a callback option, or can I ask repeatedly? My current solution is to force a delay at the end the class initialize method - 5 seconds seems to work - because I can't find anything in the documentation.

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  • How to build custom sqlite with provider under Android?

    - by dr4cul4
    Hi, I have a really strange problem. I need to build custom sqlite3 database engine under Android OS, but I also want to use database provider implementation. Unfortunately when examining sources of Android 1.6 I noticed that it's not so easy. Many classes including android.database.; packages use original provider, also many other parts of framework use android.database.sqlite.; packages directly, wich ofcourse make this abstraction a bit confusing and unnesesary. But going to my question. If there is any way that I could extend database interfaces to use custom implmentation of sqlite (or any other database)?

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  • What SQL query should I perform to get the result set expected?

    - by texai
    What SQL query should I perform to get the result set expected, giving the first element of the chain (2) as input data, or any of them ? table name: changes +----+---------------+---------------+ | id | new_record_id | old_record_id | +----+---------------+---------------+ | 1| 4| 2| | -- non relevant data -- | | 6| 7| 4| | -- non relevant data -- | | 11| 13| 7| | 12| 14| 13| | -- non relevant data -- | | 31| 20| 14| +----+---------------+---------------+ Result set expected: +--+ | 2| | 4| | 7| |13| |14| |20| +--+ I know I should consider change my data model, but: What if I couldn't? Thank you in advance!

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  • Can't add an object using EF and SQL Compact

    - by kamilo
    Hello, I have some very simple SQL Compact database. I would like to use Entity Framework to access the database but for some reason I can't add an object to this database using EF. Here is the code using (pos_inglotEntities posInglotCtx = new pos_inglotEntities()) { posInglotCtx.Connection.Open(); CT_POS_OITM item = new CT_POS_OITM() { ItemCode = "123", ItemName="abc"}; try { posInglotCtx.AddToCT_POS_OITM(item); posInglotCtx.SaveChanges(); } catch (Exception e) { } posInglotCtx.Connection.Close(); } After running this code my database is still empty although if I run it once again I get "duplicate values" exception. But again database is empty. I created this db using PrimeWorks conversion tool from standard sql server database. What is going on? Thanks in advance

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