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• Best data-structure to use for two ended sorted list

  - by fmark

  I need a collection data-structure that can do the following: Be sorted Allow me to quickly pop values off the front and back of the list Remain sorted after I insert a new value Allow a user-specified comparison function, as I will be storing tuples and want to sort on a particular value Thread-safety is not required Optionally allow efficient haskey() lookups (I'm happy to maintain a separate hash-table for this though) My thoughts at this stage are that I need a priority queue and a hash table, although I don't know if I can quickly pop values off both ends of a priority queue. I'm interested in performance for a moderate number of items (I would estimate less than 200,000). Another possibility is simply maintaining an OrderedDictionary and doing an insertion sort it every-time I add more data to it. Furthermore, are there any particular implementations in Python. I would really like to avoid writing this code myself.

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• SQL indexing on varchar

  - by alex

  I have a table whose columns are varchar(50) and a float - I need to (very quickly) look get the float associated with a given string. Even with indexing, this is rather slow. I know, however, that each string is associated with an integer, which I know at the time of lookup, so that each string maps to a unique integer, but each integer does not map to a unique string. One might think of it as a tree structure. Is there anything to be gained by adding this integer to the table, indexing on it, and using a query like SELECT floatval FROM mytable WHERE phrase=givenstring AND assoc=givenint? This is Postgres, and if you couldn't tell, I have very little experience with databases.

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• wpf legacy server call

  - by Shah Al

  Hi, We have a legacy application running tomcat that publishes data in a simple html table. I have no control on the remote server publishing the data. I am looking to extract the data into a WPF desktop application and display it as a table. Is there any way a WPF application can make a url call, get the result and parse the data. This would be similar to AJAX from JSP. Any thoughts/ideas? Please advice. Regards,

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• Compressing large text data before storing into db?

  - by Steel Plume

  Hello, I have application which retrieves many large log files from a system LAN. Currently I put all log files on Postgresql, the table has a column type TEXT and I don't plan any search on this text column because I use another external process which nightly retrieves all files and scans for sensitive pattern. So the column value could be also a BLOB or a CLOB, but now my question is the following, the database has already its compression system, but could I improve this compression manually like with common compressor utilities? And above all WHAT IF I manually pre-compress the large file and then I put as binary into the data table, is it unuseful as database system provides its internal compression?

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• How come my South migrations doesn't work for Django?

  - by TIMEX

  First, I create my database. create database mydb; I add "south" to installed Apps. Then, I go to this tutorial: http://south.aeracode.org/docs/tutorial/part1.html The tutorial tells me to do this: $ py manage.py schemamigration wall --initial >>> Created 0001_initial.py. You can now apply this migration with: ./manage.py migrate wall Great, now I migrate. $ py manage.py migrate wall But it gives me this error... django.db.utils.DatabaseError: (1146, "Table 'fable.south_migrationhistory' doesn't exist") So I use Google (which never works. hence my 870 questions asked on Stackoverflow), and I get this page: http://groups.google.com/group/south-users/browse_thread/thread/d4c83f821dd2ca1c Alright, so I follow that instructions >> Drop database mydb; >> Create database mydb; $ rm -rf ./wall/migrations $ py manage.py syncdb But when I run syncdb, Django creates a bunch of tables. Yes, it creates the south_migrationhistory table, but it also creates my app's tables. Synced: > django.contrib.admin > django.contrib.auth > django.contrib.contenttypes > django.contrib.sessions > django.contrib.sites > django.contrib.messages > south > fable.notification > pagination > timezones > fable.wall > mediasync > staticfiles > debug_toolbar Not synced (use migrations): - (use ./manage.py migrate to migrate these) Cool....now it tells me to migrate these. So, I do this: $ py manage.py migrate wall The app 'wall' does not appear to use migrations. Alright, so fine. I'll add wall to initial migrations. $ py manage.py schemamigration wall --initial Then I migrate: $ py manage.py migrate wall You know what? It gives me this BS: _mysql_exceptions.OperationalError: (1050, "Table 'wall_content' already exists") Sorry, this is really pissing me off. Can someone help ? thanks. How do I get South to work and sync correctly with everything?

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• Do i need to insert one fake row in database ?

  - by Ankit Rathod

  Hello, I have few tables like example. Users Books UsersBookPurchase UID BookId UserId UName Name BookId Password Price Email This is fine. I am having my own login system but i am also using some 3rd party to validate like OpenID or facebook Authetication. My question is if the user is able to log in successfully using OpenID or facebook Authentication, what steps do i need to do i.e do i have to insert one fake row in Users table because if i do not insert how will integrity be maintained. I mean what user id should i insert in UsersBookPurchase when the person who has logged in using Facebook Authentication has made a purchase because the UserId is reference key from Users table. Please give me a high level overview of what i need to do because this is fairly common scenario. Thanks in advance :)

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• Can you automatically create a mysqldump file that doesn't enforce foreign key constraints?

  - by Tai Squared

  When I run a mysqldump command on my database and then try to import it, it fails as it attempts to create the tables alphabetically, even though they may have a foreign key that references a table later in the file. There doesn't appear to be anything in the documentation and I've found answers like this that say to update the file after it's created to include: set FOREIGN_KEY_CHECKS = 0; ...original mysqldump file contents... set FOREIGN_KEY_CHECKS = 1; Is there no way to automatically set those lines or export the tables in the necessary order (without having to manually specify all table names as that can be tedious and error prone)? I could wrap those lines in a script, but was wondering if there is an easy way to ensure I can dump a file and then import it without manually updating it.

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• Returning the value of an identity column during/after SQL INSERT command

  - by Adam Kane

  Using VS 2010, with ASP.NET, and .NET 3.0, and C#... When I use a System.Web.UI.WebControls.SqlDataSource and call its Insert() method to insert a new row, and that table has an identity column, I'd like my method to return the value of that column. For example, in my SQL 2005 table, I've got: Customer.Id Customer.FirstName Customer.LastName Where Customer.Id is an identity colum. When I call my method InsertNewCustomerRecord( "John", "Smith" ), I'd like to be able to return the Customer.Id that gets automatically generated in the database. Sorry for such a roughly posed question. Let me know if I can add better detail. Thanks.

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• C# Select clause returns system exception instead of relevant object

  - by Kashif

  I am trying to use the select clause to pick out an object which matches a specified name field from a database query as follows: objectQuery = from obj in objectList where obj.Equals(objectName) select obj; In the results view of my query, I get: base {System.SystemException} = {"Boolean Equals(System.Object)"} Where I should be expecting something like a Car, Make, or Model Would someone please explain what I am doing wrong here? The method in question can be seen here: // this function searches the database's table for a single object that matches the 'Name' property with 'objectName' public static T Read<T>(string objectName) where T : IEquatable<T> { using (ISession session = NHibernateHelper.OpenSession()) { IQueryable<T> objectList = session.Query<T>(); // pull (query) all the objects from the table in the database int count = objectList.Count(); // return the number of objects in the table // alternative: int count = makeList.Count<T>(); IQueryable<T> objectQuery = null; // create a reference for our queryable list of objects T foundObject = default(T); // create an object reference for our found object if (count > 0) { // give me all objects that have a name that matches 'objectName' and store them in 'objectQuery' objectQuery = from obj in objectList where obj.Equals(objectName) select obj; // make sure that 'objectQuery' has only one object in it try { foundObject = (T)objectQuery.Single(); } catch { return default(T); } // output some information to the console (output screen) Console.WriteLine("Read Make: " + foundObject.ToString()); } // pass the reference of the found object on to whoever asked for it return foundObject; } } Note that I am using the interface "IQuatable<T>" in my method descriptor. An example of the classes I am trying to pull from the database is: public class Make: IEquatable<Make> { public virtual int Id { get; set; } public virtual string Name { get; set; } public virtual IList<Model> Models { get; set; } public Make() { // this public no-argument constructor is required for NHibernate } public Make(string makeName) { this.Name = makeName; } public override string ToString() { return Name; } // Implementation of IEquatable<T> interface public virtual bool Equals(Make make) { if (this.Id == make.Id) { return true; } else { return false; } } // Implementation of IEquatable<T> interface public virtual bool Equals(String name) { if (this.Name.Equals(name)) { return true; } else { return false; } } } And the interface is described simply as: public interface IEquatable<T> { bool Equals(T obj); }

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• SQLITE basic syntax

  - by Doori Bar

  I seem to misunderstand a basic syntax, why this sample works: sqlite3_prepare_v2(db, "insert into test values('boo','boo',0);", strlen(querystring)+1 , &stmt, NULL); if ((rc = sqlite3_step(stmt)) != SQLITE_DONE) fprintf(stderr, "Error: sqlite3_step() %d. Error Message %s;\n",rc,sqlite3_errmsg(db)); But when I try this query: "insert into test(strtest) values('boo');" I get an error: Error: sqlite3_step() 19. Error Message constraint failed; What am I missing? table test is: "create table test (blobtest BLOB(4) NOT NULL, strtest VARCHAR NOT NULL, inttest INTEGER NOT NULL );" Thanks, Doori Bar

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• Save in Sessions to reduce database load

  - by Kovu

  at the moment I try to reduce the load on my database extremly, so I had a look in my website and think about - what database calls can I try to avoid. So is there a rule for that? Sould I save every information in a Session that is nearly never changed? e.g.: The User-Table is a 35-coloumn-table which I need so often in so different ways, that in the moment I got this user-object at nearly every PageLoad AND in the master-site-page-load (Settings, display the username for a welcome message, colors etc etc.). So is that good to avoid the database query here, save the User-Object in a Session and call it from the session - and of course destroy the session whereever the User-Object get changed (e.g. User change his settings)?

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• ideas for algorithm? sorting a list randomly with emphasis on variety

  - by Steve Eisner

  I have a table of items with [ID,ATTR1,ATTR2,ATTR3]. I'd like to select about half of the items, but try to get a random result set that is NOT clustered. In other words, there's a fairly even spread of ATTR1 values, ATTR2 values, and ATTR3 values. This does NOT necessarily represent the data as a whole, in other words, the total table may be generally concentrated on certain attribute values, but I'd like to select a subset with more variety. The attributes are not inter-related, so there's not really a correlation between ATTR1 and ATTR2. Any ideas for an efficient algorithm? Thanks! I don't really even know how to search for this :)

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• How to get rid of blank pages in PDF exported from SSRS

  - by brijit

  Hi, I have a SSRS report. When i tried to export to PDF it was taking 4 pages due to its width., where the 2nd and 4th pages were displaying one of my field from the table. So i tried to set the layout size in report properties as width=18in and height =8.5in. It gave me the whole table in a single page of PDF. But I am getting 2nd and 4th page blank. Is the way I am doing is incorrect or else how to get rid of that blank pages. Please give some ideas. Thanks in advance. Brijit

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• Using Entity Framework, how do I specify a sort on a navagation property?

  - by Jared

  I have two tables: [Category], [Item]. They are connected by a join table: [CategoryAndItem]. It has two primary key fields: [CategoryKey], [ItemKey]. Foreign keys exist appropriately and Entity has no problem pulling this in and creating the correct navigation properties that connect the entity objects. Basically each category can have multiple items, and items can be in multiple categories. The problem is that the order of items is specified per category, so that a particular item might be third in one category but fifth in another. In the past, I have added a [Sequence] field to the join table and modified the stored procedure to handle it. But since Entity is replacing my stored procedures, I need to figure out how to make Entity handle the sequence. Any suggestions?

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• Index on column with only 2 distinct values

  - by Will

  I am wondering about the performance of this index: I have an "Invalid" varchar(1) column that has 2 values: NULL or 'Y' I have an index on (invalid), as well as (invalid, last_validated) Last_validated is a datetime (this is used for a unrelated SELECT query) I am flagging a small amount of items (1-5%) of rows in the table with this as 'to be deleted'. This is so when i DELETE FROM items WHERE invalid='Y' it does not perform a full table scan for the invalid items. A problem seems to be, the actual DELETE is quite slow now, possibly because all the indexes are being removed as they are deleted. Would a bitmap index provide better performance for this? or perhaps no index at all?

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• mysql left outer join

  - by tirso

  hi to all I have two tables employee and timecard, employee table has fields employee_id,firstname,middlename,lastname and timecard table has fields employee_id,time-in,time-out,tc_date_transaction. I want to select all employee records which have the same employee_id with timecard and date is equal with the current date. If there are no records equal with the current date then return also the records of employee even without time-in,timeout and tc_date_transaction. I have query like this SELECT * FROM employee LEFT OUTER JOIN timecard ON employee.employee_id = timecard.employee_id WHERE tc_date_transaction = "17/06/2010"; result should like this: employee_id,firstname, middlename, lastname,time-in,time-out,tc_date_transaction 1,john,t,cruz,08:00,05:00,17/06/2010 2,mary,j,von,null,null,null any help would greatly appreciated Thanks in advance

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• A column insert or update conflicts with a rule imposed by a previous CREATE RULE statement.

  - by Ronnie Chester Lynwood

  hello. im working on a online game. i got some problems with inserting new data to table. im getting 2010-4-8 2:14, *** 37000, 513, [Microsoft][ODBC SQL Server Driver][SQL Server]A column insert or update conflicts with a rule imposed by a previous CREATE RULE statement. The statement was terminated. The conflict occurred in database 'KN_online', table 'ACCOUNT_CHAR', column 'strAccountID'., 261 NationSelect*** this error in logs. what does this means? how can i fix this? i've tried to delete RULE for my DB but I'm unable to delete RULE. im getting the rule 'dbo.unallowedchars' cannot be dropped because it is bounded to one or more clumn. I set all permissions right but its still not working.. thanks..

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• Is it possible to have a tableless select with multiple rows?

  - by outis

  A SELECT without a FROM clause gets us a multiple columns without querying a table: SELECT 17+23, REPLACE('bannanna', 'nn', 'n'), RAND(), CURRENT_TIMESTAMP; How can we write a query that results in multiple rows without referring to a table? Basically, abuse SELECT to turn it into a data definition statement. The result could have a single column or multiple columns. I'm most interested in a DBMS neutral answer, but others (e.g. based on UNPIVOT) are welcome. There's no technique application behind this question; it's more theoretical than practical.

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• Is Django's manage.py syncdb or South used to create the test database?

  - by Thierry Lam

  With Django 1.1.1 and South 0.62, running a test from the CLI usually have the following output: Creating table some_model Installing index for my_app.SomeModel model . ----- Ran 1 test in 1s OK After upgrading to South 0.7, the output is invoking South's migration: Creating table some_model Installing index for my_app.SomeModel model Migrating... Running migrations for my_app: - Migrating forwards to 0001_initial > my_app:0001_initial - Loading initial data for my_app Migrated: - my_app . ----- Ran 1 test in 1s OK To create the test DB, has the test always used South migration in the past(before South 0.7) even if the output is not explicitly being shown?

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• Many to Many DataSet Insert to Database using Stored Procedures

  - by Jonn

  I'm trying to do a many-to-many bulk insert to the database using a list of three different types of models. The only tools I can use are stored procedures and datasets. (But I can't use DataSet fills or DataAdapters, just plain ol' Stored Procedures). Is there an easy way to pass multiple values, let alone, pass three different lists and bulk insert them to a table in the database using stored procedures? (As specified in the title, the three tables are actually two tables and a third table to establish the many-to-many relationship between the two.)

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• Linq to sql Incorrect varchar length

  - by scott

  I have a table with a nullable varchar(50) column in it. When I am updating the value through linq to sql and trace the call in profiler it is defining the parameter as varchar(36). This is obviously causing some minor issues when we are trying to insert data that is between 37 and 50 characters long. I have tried removing the table and re-adding it to the design surface but the same thing happens. I also tried removing that property and adding it manually, same issue. When I look at the designer.cs code it shows the attribute properly: [Column(Storage="_Name", DbType="VarChar(50)")] I am out of ideas, anybody seen this before? Every other column is correct.

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• How to find the Mac address of a 'shutdown' system on local lan (is it possible?)

  - by pirates-iiita

  hello everyone, Can anyone please tell the way to find out the mac address of a system which is: Shutdown Power plugged in Connected to Lan Nic card ON. Kindly post the solution as i urgently need it in my project... thank you Update I am asking how to find out the mac address of some other system which is already shutdown.... and which is on lan.. I want to find out its mac from my system.... and to be clear... i want to tell that.. arp table can be populated by using ping .. i.e. if 172.16.3.12 is not in arp table then it can be added by just ping 172.16.3.12 but a system can be pinged only if its on ... a shutdown system can't be pinged...

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• Web-based JSON editor that works like property explorer with AJAXy input form

  - by dreftymac

  Background: This is a request for something that may not exist yet, but I've been meaning to build one for a long time. First I will ask if anyone has seen anything like it yet. Suppose you have an arbitrary JSON structure like the following: { 'str_title':'My Employee List' ,'str_lastmod': '2009-June-15' ,'arr_list':[ {'firstname':'john','lastname':'doe','age':'33',} ,{'firstname':'jane','lastname':'doe','age':'34',} ,{'firstname':'samuel','lastname':'doe','age':'35',} ] } Question: Is there a web-based JSON editor that could take a structure like this, and automatically allow the user to modify this in a user-friendly GUI? Example: Imagine an auto-generated HTML form that displays 2 input-type-text controls for both title and lastmod, and a table of input-type-text controls with three columns and three rows for arr_list ... with the ability to delete or add additional rows by clicking on a [+][X] next to each row in the table. Big Idea: The "big idea" behind this is that the user would be able to specify any arbitrary (non-recursive) JSON structure and then also be able to edit the structure with a GUI-based interaction (this would be similar to the "XML Editor Grid View" in XML Spy).

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• Update tableview instantly as data pushed in core data iphone

  - by user336685

  I need to update the tableview as soon as the content is pushed in core data database. for this AppDelegate.m contains following code NSManagedObjectContext *moc = [self managedObjectContext]; NSFetchRequest *request = [[NSFetchRequest alloc] init]; [request setEntity:[NSEntityDescription entityForName:@"FeedItem" inManagedObjectContext:moc]]; //for loop // push data in code data & then save context [moc save:&error]; ZAssert(error == nil, @"Error saving context: %@", [error localizedDescription]); //for loop ends This code triggers following code from RootviewController.m - (void)controllerWillChangeContent:(NSFetchedResultsController*)controller { [[self tableView] beginUpdates]; } But this updates the tableview only at the end of the for loop ,the table does not get updated after immediate push in db. I tried following code but that didn't work - (void)controllerDidChangeContent:(NSFetchedResultsController *)controller { // In the simplest, most efficient, case, reload the table view. [self.tableView reloadData]; } I have been stuck with this problem for several days.Please help.Thanks in advance for solution.

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• how to run foreach loop with ternary condition

  - by I Like PHP

  i have two foreach loop to display some data, but i want to use a single foreach on basis of database result. means if there is any row returns from database then forach($first as $fk=>$fv) should execute otherwise foreach($other as $ok) should execute. i m unsing below ternary operator which gives parse error $n=$db->numRows($taskData); // databsse results <?php ($n) ? foreach ($first as $fk=>$fv) : foreach ($other as $ok) { ?> <table><tr><td>......some data...</td></tr></table> <?php } ?> please suggest me how to handle such condition via ternary operator or any other idea. Thanks

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