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• large amount of data in many text files - how to process?

  - by Stephen

  Hi, I have large amounts of data (a few terabytes) and accumulating... They are contained in many tab-delimited flat text files (each about 30MB). Most of the task involves reading the data and aggregating (summing/averaging + additional transformations) over observations/rows based on a series of predicate statements, and then saving the output as text, HDF5, or SQLite files, etc. I normally use R for such tasks but I fear this may be a bit large. Some candidate solutions are to 1) write the whole thing in C (or Fortran) 2) import the files (tables) into a relational database directly and then pull off chunks in R or Python (some of the transformations are not amenable for pure SQL solutions) 3) write the whole thing in Python Would (3) be a bad idea? I know you can wrap C routines in Python but in this case since there isn't anything computationally prohibitive (e.g., optimization routines that require many iterative calculations), I think I/O may be as much of a bottleneck as the computation itself. Do you have any recommendations on further considerations or suggestions? Thanks

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• error with io stream

  - by Alexander

  What is the problem with the last two statements in the code? #include <iostream> using namespace std; int main() { cout << "2 + 4 = " << 2 + 4 << endl; cout << "2 * 4 = " << 2 * 4 << endl; cout << "2 | 4 = " << 2 | 4 << endl; cout << "2 & 4 = " << 2 & 4 << endl; What should I do to fix this?

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• [MYSQL] Select users who own both a dog and a cat

  - by matte

  Hi, I have this sample table: CREATE TABLE `dummy` ( `id` int(11) NOT NULL AUTO_INCREMENT, `userId` int(11) NOT NULL, `pet` varchar(50) NOT NULL, PRIMARY KEY (`id`) ) ENGINE=MyISAM DEFAULT CHARSET=latin1 AUTO_INCREMENT=7 ; INSERT INTO `dummy` (`id`, `userId`, `pet`) VALUES(1, 1, 'dog'); INSERT INTO `dummy` (`id`, `userId`, `pet`) VALUES(2, 1, 'cat'); INSERT INTO `dummy` (`id`, `userId`, `pet`) VALUES(3, 2, 'dog'); INSERT INTO `dummy` (`id`, `userId`, `pet`) VALUES(4, 2, 'cat'); INSERT INTO `dummy` (`id`, `userId`, `pet`) VALUES(5, 3, 'cat'); INSERT INTO `dummy` (`id`, `userId`, `pet`) VALUES(6, 4, 'dog'); How can I write the statements below in mysql: Retrieve all users who own both a dog and a cat Retrieve all users who own a dog or a cat Retrieve all users who own only a cat Retrieve all users who doesn't own a cat Thanks!

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• copying a jar file in Apache Ant

  - by synchronicity

  I need to copy a jar file from one directory to another when my project is built. Placing the statement: <copy file="${test.dir}/MyFirstTest.jar" todir="${share.path}"/> works fine when the project is built alone, but if I clean and build the project I get a warning informing me that the ${test.dir}/ directory hasn't been created yet. If I'm understanding properly I should be able to create a 'target' and specify a dependency for this operation but I'm unsure of what dependency to specify. What series of statements do I need to use to ensure this copy will occur whether I clean and build or just build the project? Please let me know if any further clarification is needed. FYI I am using Netbeans 6.8 to build my project.

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• Prevent SQL injection from form-generated SQL.

  - by Markos Fragkakis

  Hi all, I have a search table where user will be able to filter results with a filter of the type: Field [Name], Value [John], Remove Rule Field [Surname], Value [Blake], Remove Rule Field [Has Children], Value [Yes], Remove Rule Add Rule So the user will be able to set an arbitrary set of filters, which will result essentially in a completely dynamic WHERE clause. In the future I will also have to implement more complicated logical expressions, like Where (name=John OR name=Nick) AND (surname=Blake OR surname=Bourne), Of all 10 fields the user may or may not filter by, I don't know how many and which filters the user will set. So, I cannot use a prepared statement (which assumes that at least we know the fields in the WHERE clause). This is why prepared statements are unfortunately out of the question, I have to do it with plain old, generated SQL. What measures can I take to protect the application from SQL Injection (REGEX-wise or any other way)?

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• Assert parameters in a table-valued UDF

  - by Clay Lenhart

  Is there a way to create "asserts" on the parameters of a table-valued UDF. I'd like to use a table-valued UDF for performance reasons, however I know that certain parameter combinations (like start and end dates that are more than a month apart) will cause performance issues on the server for all users. End users query the database via Excel using UDFs. UDFs (and table-valued UDFs in particular) are useful when the data is too large for Excel. Users write simple SQL queries that categorizes the data into groups to reduce the number of rows. For example, the user may be interested in weekly aggregates rather than hourly ones. Users write a group by SELECT statement to reduce the rows by 24x7=168 times. I know I can write RAISERROR statements in multistatement UDFs, but table-valued UDFs are integrated in the query optimizer so these queries are more efficient with table-valued UDFs. So, can I define assertions on the parameters passed to a table-valued UDF?

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• Good error flagging

  - by Wayne

  For everyone that was thinking of the error_reporting() function, then it isn't, what I need is whenever a MySQL query has been done, and the statement has like if($result) { echo "Yes, it was fine... bla bla"; } else { echo "Obviously, the echo'ing will show in a white page with the text ONLY..."; } Whenever statements have been true or false, I want the error to be appeared when redirected with the header() function and echo the error reporting in a div somewhere on the page. Basically something like this: $error = ''; This part appears inside the div tags <div><?php echo $error; ?></div> So the error part will be echoed when redirected with the header() if($result) { $error = "Yes, it was fine... bla bla"; header("Location: url"); } else { $error = "Something wrong happened..."; header("Location: url"); } But that just doesn't work :(

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• C# console application

  - by Andy

  I have sample exe say console.exe on "programfiles\myAppFolder" .It serves the purpose of logging the message to eventviewer EventLog.WriteEntry(sSource, sEvent, EventLogEntryType.Warning, 234); But whenever I click on the exe I need to call this exe on un-install of appcn from NSIS script .However it gives me an error always that "thisappConsole has encountered a problem and needs to close. We are sorry for the inconvenience." Can anyone help me with this. If I put any other sample consoleapp without any additional "using statements". it works ..

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• T-SQL Where statement - OR

  - by Zyphrax

  Sorry for the vague title but I really didn't know what title to give to this problem: I have the following result set: ID Data Culture 1 A nl-NL 2 B nl-NL 3 C nl-NL 4 A en-GB 5 B en-GB 6 A en 7 B en 8 C en 9 D en 10 A nl I would like to mimic the ASP.Net way of resource selection, user Culture (nl-NL) SELECT Data FROM Tbl WHERE Culture = 'nl-NL' Or when there are no results for the specific culture, try the parent Culture (nl) SELECT Data FROM Tbl WHERE Culture = 'nl' Or when there are no results for the parent culture, try the default Culture (en) SELECT Data FROM Tbl WHERE Culture = 'en' How can I combine these SELECT-statements in one T-SQL statement? I'm using LINQ so a LINQ expression would be even greater. The OR-statement won't work, because I don't want a mix of cultures. The ORDER BY-statement won't help, because it returns multiple records per culture.

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• Strategy for Offline/Online data synchronization

  - by Adi

  My requirement is I have server J2EE web application and client J2EE web application. Sometimes client can go offline. When client comes online he should be able to synchronize changes to and fro. Also I should be able to control which rows/tables need to be synchronized based on some filters/rules. Is there any existing Java frameworks for doing it? If I need to implement on my own, what are the different strategies that you can suggest? One solution in my mind is maintaining sql logs and executing same statements at other side during synchronization. Do you see any problems with this strategy?

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• How do I do this Database Model in Django?

  - by alex

  Django currently does not support the "Point" datatype in MySQL. That's why I created my own. class PointField(models.Field): def db_type(self): return 'Point' class Tag(models.Model): user = models.ForeignKey(User) utm = PointField() As you can see, this works, and syncdb creates the model fine. However, my current code calculates a length between two Points using raw SQL. cursor.execute("SELECT user_id FROM life_tag WHERE\ (GLength(LineStringFromWKB(LineString(asbinary(utm), asbinary(PointFromWKB(point(%s, %s)))))) < 55)... This says: Select where the length between the given point and the table point is less than 55. How can I do this with Django instead of RAW SQL? I don't want to do cursors and SELECT statements anymore. How can I modify the models.py in order to do this?

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• Expression Tree

  - by nettguy

  My understanding of expression tree is : Expression trees are in-memory representation of expression like arithmetic or boolean expression.The expressions are stored into the parsed tree.so we can easily transalate into any other language. Linq to SQL uses expression tree.Normally in LINQ to SQL query the compiler translates it into parsed expression trees.These are passed to Sql Server as T-SQL Statements.The Sql server executes the T-SQL query and sends down the result back.That is why when you execute LINQ to SQL you gets IQueryable<T> not IEnumetrable<T>.Because IQuerybale contains public IQueryable:IEnumerable { Type Element {get;} Expression Expression {get;} IQueryaleProvider Provider {get;} } Questions : Microsoft uses Expression trees to play with LINQ-to-Sql.What are the different ways can i use expression trees to boost my code. Apart from LINQ to SQL,Linq to amazon ,who used expression trees in their applications? Linq to Object return IEnumerable,Linq to SQL return IQueryable ,What does LINQ to XML return?

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• ALTER TABLE without locking the table?

  - by Daniel

  When doing an ALTER TABLE statement in MySQL, the whole table is read-locked for the duration of the statement. If it's a big table, that means insert or update statements could be locked for a looooong time. Is there a way to do a "hot alter", like adding a column in such a way that the table is still updatable throughout the process? Mostly I'm interested in a solution for MySQL but I'd be interested in other RDBMS if MySQL can't do it. To clarify, my purpose is simply to avoid downtime when a new feature that requires an extra table column is pushed to production. Any database schema will change over time, that's just a fact of life. I don't see why we should accept that these changes must inevitably result in downtime; that's just weak.

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• Convert the ada code to its C .

  - by maddy

  HI All, I have a piece of ada code shown below which is a simple switch case statements.Is there any better way to convert this into C. for I in 1..100 loop case I is when 100 => Dollars := Dollars + 1; when 25|50|75 => Quarters := Quarters + 1; when 10|20|30|40|60|70|80|90 => Dimes := Dimes + 1; when 5|15|35|45|55|65|85|95 => Nickles := Nickles + 1; when others => Pennies := Pennies + 1; end case; end loop; Now by adding the switch and the case for each values in the case,i can do that conversion,But it seems tyo make the code too big.Is there anywa other simple and compact way.Please get back to me if the question is not clear? Regards maddy

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• What could make GetCursorPos return incorrect coordinates of {0,0} ?

  - by Dave Moore

  We are seeing bad behavior in an application when it runs on Server 2008 (not R2). This is a WinForms application, and Control.MousePosition is returning {0,0} no matter where the mouse is on the screen... Control.MousePosition just makes a P/Invoke call to Win32 api GetCursorPos(). There is a control in our library that calls SetWindowsHookEx to hook WH_CALLWNDPROCRET for our entire process. I'm suspicious of this code, but tracing statements show that we're getting in + out of that hook cleanly. What else should I be looking for? Thanks, Dave

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• NHibernate mapping one table on two classes with where selection

  - by Rene Schulte

  We would like to map a single table on two classes with NHibernate. The mapping has to be dynamically depending on the value of a column. Here's a simple example to make it a bit clearer: We have a table called Person with the columns id, Name and Sex. The data from this table should be mapped either on the class Male or on the class Female depending on the value of the column Sex. In Pseudocode: create instance of Male with data from table Person where Person.Sex = 'm'; create instance of Female with data from table Person where Person.Sex = 'f'; The benefit is we have strongly typed domain models and can later avoid switch statements. Is this possible with NHibernate or do we have to map the Person table into a flat Person class first? Then afterwards we would have to use a custom factory method that takes a flat Person instance and returns a Female or Male instance. Would be good if NHibernate (or another library) can handle this.

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• PHP Prepared Statement Returns -1

  - by pws5068

  I've been using prepared statements for a little while now and I've never had any problems. Now I'm trying to: $sql="SELECT PhotoID,Caption FROM Photos WHERE EntityID=? AND TypeID=? LIMIT ?,?"; $iDB = new mysqliDB(); // Extends mysqli $stmt = $iDB->prepare($sql); $stmt->bind_param('iiii',$entityID,$typeID,$minRange,$maxRange); $stmt->execute(); $stmt->bind_result($photoID,$caption); echo("Affected={$stmt->affected_rows}"); This prints -1. I have triple tested that all 4 values in bindParam are set, and that the sql query works when pasted into myAdmin with the respective values. Any idea what may be causing this?

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• Is release without prior retain dangerous?

  - by BankStrong

  I have some code which I think has extra release statements. Is the code incorrect? What is the end result? I don't understand memory management well yet - even after reading lots of articles and stackoverflow answers. Thanks for straightening me out. NSMutableArray *points = [NSMutableArray new]; for (Segment *s in currentWorkout.segments) { [points addObjectsFromArray:[s.track locationPoints]]; } [routeMap update:points]; [points release];

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• C# ProgressBar design pattern

  - by MadSeb

  Hi, I'm working on a database upgrader application. The upgrader updates the schema of a database ( adds new columns, renames columns , adds new tables, new views to an existing database by executing SQL statements ). When a user wants to upgrade from version 1.0 to 2.0 , "Upgrader" objects are taken from an object factory and the "Execute" method of each "Upgrader" is called. The GUI of the application has a progress bar and each time an upgrader object performs a SQL statement the progress bar gets incremented. while (!version.Equal(CurrentVersion)) { IUpgrader myUpgrader = UpgraderFactory.GetUpgrader(version); myUpgrader.Execute(UpgradedFile,progressbar); version.Increment(); } My question is very simple : how should the upgrader object communicate with the progressbar. In the code above, the upgrader object is given direct access to the progressbar but I'm wondering if some better way of doing this or better design pattern exists. Regards, Seb

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• SharePoint Custom Application Page does not recognize tagPrefix defined in custom web.config

  - by Hasan Khan

  I have a custom application page integrated in Centeral Administration. My application pages are placed in a subfolder in Template\Admin folder. I placed my own web.config in my subfolder and added tagPrefixes in the control section. However when I open my application page ASP.NET throws the exception that the tag SharePoint:InputFormTextBox was not recognized. Moving the add tagprefix statements in root web.config solves the problem but thats not acceptable in my case and I can't define them in individual pages either. What am I doing wrong? Or it doesn't work this way? What can i do to achieve this?

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• Object tree navigation language in Java

  - by lewap

  In the system which I'm currently developing I often have to navigate an object tree and based on its state and values take actions. In normal Java this results in tedious for loops, if statements etc... Are there alternative ways to achieve tree navigation, similar to XPath for XML? I know there is JXPath and OGNL, but do you know any other libraries for such purpose? Do you know any libraries which generate bytecodes for specific tree navigation expressions to make the processing as fast as Java native fors and ifs?

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• Regarding BigDecimal

  - by arav

  i do the below java print command for this double variable double test=58.15; When i do a System.out.println(test); and System.out.println(new Double(test).toString()); It prints as 58.15. When i do a System.out.println(new BigDecimal(test)) I get the below value 58.14999999999999857891452847979962825775146484375 I am able to understand "test" double variable value is internally stored as 58.1499999. But when i do the below two System.out.println i am getting the output as 58.15 and not 58.1499999. System.out.println(test); System.out.println(new Double(test).toString()); It prints the output as 58.15 for the above two. Is the above System.out.println statements are doing some rounding of the value 58.1499999 and printing it as 58.15?

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• C# switch: case not falling through to other cases limitation

  - by Mike Fielden

  This question is kind of an add-on to this question In C#, a switch case cannot fall through to other cases, this causes a compilation error. In this case I am just adding some number to the month total for the selected month and each subsequent month thereafter. (simple example, not meant to be real) switch (month) { case 0: add something to month totals case 1: add something to month totals case 2: add something to month totals default: break; } Is there a logical alternative to this in C# without having to write out a ton of if statements? if (month <= 0) add something to month if (month <= 1) add something to month if (month <= 2) add something to month .... etc

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• IE browser doesn't close and file download popup needs focus

  - by jkranthi

  Hii all , I am trying to to click on a link after it is active which again produces a popup ( file download) after clicking. Here i have 2 problems 1) I start the code and leave it .what the code does is -after long process -it waits for the link to be active .Once the link is active it clicks on the link and a download popups opens (if everything goes well) and then it hangs there ( showing yellow flashing in the task bar which mean i have to click on the explorer for it to process whatever is next ).every time i have to click on the IE whenever the download popup appears .Is there a way to handle this or am i doing some wrong ? 2) The next problem is even if i click on the IE .the IE doesn't get close even though i write ie.close . my code is below : ## if the link is active ie.link(:text,a).click_no_wait prompt_message = "Do you want to open or save this file?" window_title = "File Download" save_dialog =WIN32OLE.new("AutoItX3.Control") save_dialog.WinGetText(window_title) save_dialog_obtained =save_dialog.WinWaitActive(window_title) save_dialog.WinKill(window_title) # end #' #some more code -normal puts statements # ie.close ie is hanging up for some strange reason ..?

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• WHERE clause confusion with PDO

  - by Greg

  I'm having some trouble understanding how to use prepared statements, when you need to match one value against several columns at once. In other words what instead of doing this: $stmt = $dbh-prepare("SELECT * FROM REGISTRY where name = ?"); $stmt-bindParam(':name', $name); I wanted to do this: $stmt = $dbh-prepare("SELECT * FROM REGISTRY where firstname = ? or lastname = ?"); with both '?' representing the same string.

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