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• A Big Data korszakban, túl az 1000. eladott Oracle Exadata Database Machine adatbázisgépen

  - by user645740

  Mint azt már egy ideje a szél is fújja, beköszöntött a BIG DATA korszak, azaz egyre több adat gyulik, egyre több adattal gazdálkodunk. A hatalmas mennyiségu adat jó részét Oracle adatbázisokban tárolják. Mi is futtathatná jobban, gyorsabban és hetékonyabban ezeket az Oracle adatbázisokat, mint az Oracle stratégiai high-end megoldása az Oracle Exadata Database Machine? Rengeteg forrása van a sok adatnak, néhány példa, ahol a növekedés óriási: kommunikációs adatok, CDR-ek banki és kormányzati tranzakciók hely információk spatial, location, GPS,..., mint ahogyan a közelmúltban az egyes telefonokkal ésoperációs rendszerekkel kapcsolatos "ügyekben" is olvashattuk, e-mail-ek, közösségi site-ok, intelligens méromuszerek, háztartási berendezések, .... Milyen ütemben no az Exadata értékesítés? Nos az Exadata 2008 oszén lett bejelentve. Az Oracle pénzügyi év végén a jelentésben azt olvashatjuk, hogy az Exadata páratlanul sikeres megoldás, már több mint 1000 Exadatát vásároltak meg az Oracle ügyfelek, mondta Mark Hurd, az Oracle alelnöke:   “In addition to record setting software sales, our Exadata and Exalogic systems also made a strong contribution to our growth in Q4,” said Oracle President, Mark Hurd. “Today there are more than 1,000 Exadata machines installed worldwide. Our goal is to triple that number in FY12.” Larry Ellison, az Oracle elso embere, azt nyilatkozta, hogy mind a felho - cloud computing, mind a memória-adatbázisok területén egyre gyorsabban növekszik az Oracle:   “In FY11 Oracle’s database business experienced its fastest growth in a decade,” said Oracle CEO, Larry Ellison. “Over the past few years we added features to the Oracle database for both cloud computing and in-memory databases that led to increased database sales this past year. Lately we’ve been focused on the big business opportunity presented by Big Data.” A Big Data korszakban  megtakarításokat érhetünk el az Exadatával, tekintse meg a következo videót, de óvatosan, mert gondolkodásra késztet:    -   Oracle Exadata: Are You Ready?.

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• How to avoid big and clumsy UITableViewController on iOS?

  - by Johan Karlsson

  I have a problem when implementing the MVC-pattern on iOS. I have searched the Internet but seems not to find any nice solution to this problem. Many UITableViewController implementations seems to be rather big. Most examples I have seen lets the UITableViewController implement <UITableViewDelegate> and <UITableViewDataSource>. These implementations are a big reason why UITableViewControlleris getting big. One solution would be to create separate classes that implements <UITableViewDelegate> and <UITableViewDataSource>. Of course these classes would have to have a reference to the UITableViewController. Are there any drawbacks using this solution? In general I think you should delegate the functionality to other "Helper" classes or similar, using the delegate pattern. Are there any well established ways of solving this problem? I do not want the model to contain too much functionality, nor the view. I believe that the logic should really be in the controller class, since this is one of the cornerstones of the MVC-pattern. But the big question is: How should you divide the controller of a MVC-implementation into smaller manageable pieces? (Applies to MVC in iOS in this case) There might be a general pattern for solving this, although I am specifically looking for a solution for iOS. Please give an example of a good pattern for solving this issue. Please provide an argument why your solution is awesome.

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• How do I use Sketchflow sample data for a ListBoxItem Template at design time?

  - by Boris Nikolaevich

  I am using Expression Blend 4 and Visual Studio 2010 to create a Sketchflow prototype. I have a Sample Data collection and a ListBox that is bound to it. This displays as I would expect both at design time and at run time. However, the ListBoxItem template it just complex enough that I wanted to pull it out into its own XAML file. Even though the items still render as expected in the main ListBox where the template is used, when I open the template itself, all of the databound controls are empty. If I add a DataContext to the template, I can see and work with the populated objects while in the template, but then that local DataContext overrides the DataContext set on the listbox. A bit of code will illustrate. Start by creating a Sketchflow project (I am using Silverlight, but it should work the same for WPF), then add a project data source called SampleDataSource. Add a collection called ListData, with a single String property called Title. Here is the (scaled down) code for the main Sketchflow screen, which we'll call Main.xaml: <UserControl xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" xmlns:d="http://schemas.microsoft.com/expression/blend/2008" xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" xmlns:local="clr-namespace:DemoScreens" mc:Ignorable="d" x:Class="DemoScreens.Main" Width="800" Height="600"> <UserControl.Resources> <ResourceDictionary> <ResourceDictionary.MergedDictionaries> <ResourceDictionary Source="ProjectDataSources.xaml"/> </ResourceDictionary.MergedDictionaries> <DataTemplate x:Key="ListBoxItemTemplate"> <local:DemoListBoxItemTemplate d:IsPrototypingComposition="True" Margin="0,0,5,0" Width="748"/> </DataTemplate> </ResourceDictionary> </UserControl.Resources> <Grid x:Name="LayoutRoot" Background="#5c87b2" DataContext="{Binding Source={StaticResource SampleDataSource}}"> <ListBox Background="White" x:Name="DemoList" Style="{StaticResource ListBox-Sketch}" Margin="20,100,20,20" ItemTemplate="{StaticResource ListBoxItemTemplate}" ItemsSource="{Binding ListData}" ScrollViewer.HorizontalScrollBarVisibility="Disabled"/> </Grid> </UserControl> You can see that it references the DemoListBoxItemTemplate, which is defined in its own DemoListBoxItemTemplate.xaml: <UserControl xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" xmlns:d="http://schemas.microsoft.com/expression/blend/2008" xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" xmlns:local="clr-namespace:DemoScreens" mc:Ignorable="d" x:Class="DemoScreens.DemoListBoxItemTemplate"> <Grid x:Name="LayoutRoot"> <TextBlock Text="{Binding Title}" Style="{StaticResource BasicTextBlock-Sketch}" Width="150"/> </Grid> </UserControl> Obviously, this is way simpler than my actual listbox, but it should be enough to illustrate my problem. When you open Main.xaml in the Expression designer, the list box is populated with sample data. But when you open DemoListBoxItemTemplate.xaml, there is no data context and therefore no data to display—which makes it more difficult to identify controls visually. How can I have sample data displayed when I am working with the template, while still allowing the larger set of sample data to be used for the ListBox itself?

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• c# write big files to blob sqlite

  - by brizjin-gmail-com

  I have c# application which write files to sqlite database. It uses entity fraemwork for modeling data. Write file to blob (entity byte[] varible) with this line: row.file = System.IO.File.ReadAllBytes(file_to_load.FileName); //row.file is type byte[] //row is entity class table All work correctly when files size is less. When size more 300Mb app throw exception: Exception of type 'System.OutOfMemoryException' was thrown. How I can write to blob direct, without memory varibles?

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• Are there any decent free JAVA data plotting libraries out there?

  - by Kurt W. Leucht

  On a recent JAVA project, we needed a free JAVA based real-time data plotting utility. After much searching, we found this tool called the Scientific Graphics Toolkit or SGT from NOAA. It seemed pretty robust, but we found out that it wasn't terribly configurable. Or at least not configurable enough to meet our needs. We ended up digging very deeply into the JAVA code and reverse engineering the code and changing it all around to make the plot tool look and act the way we wanted it to look and act. Of course, this killed any chance for future upgrades from NOAA. So what free or cheap JAVA based data plotting tools or libraries do you use? Followup: Thanks for the JFreeChart suggestions. I checked out their website and it looks like a very nice data charting and plotting utility. I should have made it clear in my original question that I was looking specifically to plot real-time data. I corrected my question above to make that point clear. It appears that JFreeChart support for live data is marginal at best, though. Any other suggestions out there?

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• Google Federated Login vs Hybrid Protocol vs Google Data Authentication. Whats's the Difference?

  - by johnfelix

  Hi, I am trying to implement Google Authentication in my website, in which I would also be pulling some Google Data using the Google Data API and I am using Google App Engine with Jinja2. My question is, so many ways are mentioned to do it. I am confused between Google Federated Login,Google Data Protocol, Hybrid Protocol. Are these things the same or different ways to do the same thing. From what I read and understood, which might be incorrect, Google Federated Login uses the hybrid protocol to authenticate and fetch the google data. Is there a proper guide to implement any one of these in python. Examples which I found at the google link are kind of different. From what I understood,correct me if i am wrong, I have to implement only the OpenID Consumer part. In order to implement Google Federated Login in Python, I saw that we need to download a separate library from the openid-enabled.com but I found a different library for the google data implementation at http://code.google.com/p/gdata-python-client/ As you can see, I am confused a lot :D. Please help me :) Thanks

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• How to efficiently save changes made in UI/main thread with Core Data?

  - by Jaanus

  So, there have been several posts here about importing and saving data from an external data source into Core Data. Apple documents a reasonable pattern for this: "import and save on background thread, merge saved objects to main thread." All fine and good. I have a related but different problem: the user is modifying data in the UI and main thread, and thus modifies state of some objects in the managed object context (MOC). I would like to save these changes from time to time. What is a good way to do that? Now, you could say that I could do the same: create a background thread with its own MOC and pass the changed objectID-s there. The catch-22 for me with this is that an object's ID changes when it is saved, and I cannot guarantee the order of things happening. I may end up passing a different objectID into the background thread for the same object, based on whether the object has been previously saved or not, and I don't know if Core Data can resolve this and see that different objectID-s are pointing to the same object and not create duplicates for me. (I could test this, but I'm lazywebbing with this question first.) One thought I had: I could always do MOC saves on a background thread, and queue them up with operationqueue, so that there is always only one save in progress. I would not create a new MOC, I would just use the same MOC as in main thread. Now, this is not thread safe and when someone modifies the MOC in main thread while it is being saved in background thread, the results will probably be catastrophic. But, minus the thread safety, you can see what kind of solution I'd wish for. To be clear, the problem I need to fix is that if I just do the save in main thread, it blocks the UI for an unacceptably long period of time, I want to move the save to background thread. So, questions: what about the reasoning of an object ID changing during saving, and Core Data being able to resolve them to the same object? Would this be the right way of addressing this problem? any other good ways of doing this?

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• Binary Search Tree Implementation

  - by Gabe

  I've searched the forum, and tried to implement the code in the threads I found. But I've been working on this real simple program since about 10am, and can't solve the seg. faults for the life of me. Any ideas on what I'm doing wrong would be greatly appreciated. BST.h (All the implementation problems should be in here.) #ifndef BST_H_ #define BST_H_ #include <stdexcept> #include <iostream> #include "btnode.h" using namespace std; /* A class to represent a templated binary search tree. */ template <typename T> class BST { private: //pointer to the root node in the tree BTNode<T>* root; public: //default constructor to make an empty tree BST(); /* You have to document these 4 functions */ void insert(T value); bool search(const T& value) const; bool search(BTNode<T>* node, const T& value) const; void printInOrder() const; void remove(const T& value); //function to print out a visual representation //of the tree (not just print the tree's values //on a single line) void print() const; private: //recursive helper function for "print()" void print(BTNode<T>* node,int depth) const; }; /* Default constructor to make an empty tree */ template <typename T> BST<T>::BST() { root = NULL; } template <typename T> void BST<T>::insert(T value) { BTNode<T>* newNode = new BTNode<T>(value); cout << newNode->data; if(root == NULL) { root = newNode; return; } BTNode<T>* current = new BTNode<T>(NULL); current = root; current->data = root->data; while(true) { if(current->left == NULL && current->right == NULL) break; if(current->right != NULL && current->left != NULL) { if(newNode->data > current->data) current = current->right; else if(newNode->data < current->data) current = current->left; } else if(current->right != NULL && current->left == NULL) { if(newNode->data < current->data) break; else if(newNode->data > current->data) current = current->right; } else if(current->right == NULL && current->left != NULL) { if(newNode->data > current->data) break; else if(newNode->data < current->data) current = current->left; } } if(current->data > newNode->data) current->left = newNode; else current->right = newNode; return; } //public helper function template <typename T> bool BST<T>::search(const T& value) const { return(search(root,value)); //start at the root } //recursive function template <typename T> bool BST<T>::search(BTNode<T>* node, const T& value) const { if(node == NULL || node->data == value) return(node != NULL); //found or couldn't find value else if(value < node->data) return search(node->left,value); //search left subtree else return search(node->right,value); //search right subtree } template <typename T> void BST<T>::printInOrder() const { //print out the value's in the tree in order // //You may need to use this function as a helper //and create a second recursive function //(see "print()" for an example) } template <typename T> void BST<T>::remove(const T& value) { if(root == NULL) { cout << "Tree is empty. No removal. "<<endl; return; } if(!search(value)) { cout << "Value is not in the tree. No removal." << endl; return; } BTNode<T>* current; BTNode<T>* parent; current = root; parent->left = NULL; parent->right = NULL; cout << root->left << "LEFT " << root->right << "RIGHT " << endl; cout << root->data << " ROOT" << endl; cout << current->data << "CURRENT BEFORE" << endl; while(current != NULL) { cout << "INTkhkjhbljkhblkjhlk " << endl; if(current->data == value) break; else if(value > current->data) { parent = current; current = current->right; } else { parent = current; current = current->left; } } cout << current->data << "CURRENT AFTER" << endl; // 3 cases : //We're looking at a leaf node if(current->left == NULL && current->right == NULL) // It's a leaf { if(parent->left == current) parent->left = NULL; else parent->right = NULL; delete current; cout << "The value " << value << " was removed." << endl; return; } // Node with single child if((current->left == NULL && current->right != NULL) || (current->left != NULL && current->right == NULL)) { if(current->left == NULL && current->right != NULL) { if(parent->left == current) { parent->left = current->right; cout << "The value " << value << " was removed." << endl; delete current; } else { parent->right = current->right; cout << "The value " << value << " was removed." << endl; delete current; } } else // left child present, no right child { if(parent->left == current) { parent->left = current->left; cout << "The value " << value << " was removed." << endl; delete current; } else { parent->right = current->left; cout << "The value " << value << " was removed." << endl; delete current; } } return; } //Node with 2 children - Replace node with smallest value in right subtree. if (current->left != NULL && current->right != NULL) { BTNode<T>* check; check = current->right; if((check->left == NULL) && (check->right == NULL)) { current = check; delete check; current->right = NULL; cout << "The value " << value << " was removed." << endl; } else // right child has children { //if the node's right child has a left child; Move all the way down left to locate smallest element if((current->right)->left != NULL) { BTNode<T>* leftCurrent; BTNode<T>* leftParent; leftParent = current->right; leftCurrent = (current->right)->left; while(leftCurrent->left != NULL) { leftParent = leftCurrent; leftCurrent = leftCurrent->left; } current->data = leftCurrent->data; delete leftCurrent; leftParent->left = NULL; cout << "The value " << value << " was removed." << endl; } else { BTNode<T>* temp; temp = current->right; current->data = temp->data; current->right = temp->right; delete temp; cout << "The value " << value << " was removed." << endl; } } return; } } /* Print out the values in the tree and their relationships visually. Sample output: 22 18 15 10 9 5 3 1 */ template <typename T> void BST<T>::print() const { print(root,0); } template <typename T> void BST<T>::print(BTNode<T>* node,int depth) const { if(node == NULL) { std::cout << std::endl; return; } print(node->right,depth+1); for(int i=0; i < depth; i++) { std::cout << "\t"; } std::cout << node->data << std::endl; print(node->left,depth+1); } #endif main.cpp #include "bst.h" #include <iostream> using namespace std; int main() { BST<int> tree; cout << endl << "LAB #13 - BINARY SEARCH TREE PROGRAM" << endl; cout << "----------------------------------------------------------" << endl; // Insert. cout << endl << "INSERT TESTS" << endl; // No duplicates allowed. tree.insert(0); tree.insert(5); tree.insert(15); tree.insert(25); tree.insert(20); // Search. cout << endl << "SEARCH TESTS" << endl; int x = 0; int y = 1; if(tree.search(x)) cout << "The value " << x << " is on the tree." << endl; else cout << "The value " << x << " is NOT on the tree." << endl; if(tree.search(y)) cout << "The value " << y << " is on the tree." << endl; else cout << "The value " << y << " is NOT on the tree." << endl; // Removal. cout << endl << "REMOVAL TESTS" << endl; tree.remove(0); tree.remove(1); tree.remove(20); // Print. cout << endl << "PRINTED DIAGRAM OF BINARY SEARCH TREE" << endl; cout << "----------------------------------------------------------" << endl; tree.print(); cout << endl << "Program terminated. Goodbye." << endl << endl; } BTNode.h #ifndef BTNODE_H_ #define BTNODE_H_ #include <iostream> /* A class to represent a node in a binary search tree. */ template <typename T> class BTNode { public: //constructor BTNode(T d); //the node's data value T data; //pointer to the node's left child BTNode<T>* left; //pointer to the node's right child BTNode<T>* right; }; /* Simple constructor. Sets the data value of the BTNode to "d" and defaults its left and right child pointers to NULL. */ template <typename T> BTNode<T>::BTNode(T d) : left(NULL), right(NULL) { data = d; } #endif Thanks.

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• Core Data - How to check if a managed object's properties have been deallocated?

  - by georryan

  I've created a program that uses core data and it works beautifully. I've since attempted to move all my core data methods calls and fetch routines into a class that is self contained. My main program then instantiates that class and makes some basic method calls into that class, and the class then does all the core data stuff behind the scenes. What I'm running into, is that sometimes I'll find that when I grab a managed object from the context, I'll have a valid object, but its properties have been deallocated, and I'll cause a crash. I've played with the zombies and looked for memory leaks, and what I have gathered is it seems that the run loop is probably responsible for deallocating the memory, but I'm not sure. Is there a way to determine if that memory has been deallocated and force the core data to get it back if I need to access it? My managedObjectContext never gets deallocated, and the fetchedResultsController never does, either. I thought maybe I needed to use the [managedObjectContext refreshObject:mergeData:] method, or the [managedObjectContext setRetainsRegisteredObjects:] method. Although, I'm under the impression that last one may not be the best bet since it will be more memory intensive (from what I understand). These errors only popped up when I moved the core data calls into another class file, and they are random when they show up. Any insight would be appreciated. -Ryan

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• Any chance to get Core Data using Tokyo Cabinet as the persistent store?

  - by dontWatchMyProfile

  I watched a free high quality video with Aaron Hillegass about Core Data vs Tokyo Cabinet. Besides that this guy is amazingly funny (really, if you want to laugh now, watch it!), he shows off Tokyo Cabinet beeing about 40x faster than Core Data. I wonder if it's worth thinking about how to attach this to Core Data? Does that make any sense? Maybe as a custom atomic store or something like this?

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• Is there a good Core Data browsing tool out there?

  - by Greg Martin

  One of the things I miss from moving from SQLite to Core Data is the ability to query directly against my database to analyze data. Is anyone out there aware of a tool that allows for the browsing of a Core Data store in a similar fashion?

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• Performance in SQL Mobile with one big column that's not being selected

  - by Anthony Mastrean

  I have a SQL Mobile database with one table. It has several columns with useful, often queried data and one column that stores a relatively large string per record (1000+ characters) that is not queried often. Imagine this fake schema, the "lifeStory" field is the large one. table1 String firstName String lastName String address String lifeStory A representative query would be SELECT firstName, lastName, address FROM table1 WHERE firstName = :p1 Does anyone know of any performance concerns leaving that large, infrequently queried column in this table?

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• AES decryption in Java - IvParameterSpec to big

  - by user1277269

  Im going to decrypt a plaintext with two keys. As you see in the picture were have one encrypted file wich contains KEY1(128 bytes),KEYIV(128 bytes),key2(128bytes) wich is not used in this case then we have the ciphertext. The error I get here is "Exception in thread "main" java.security.InvalidAlgorithmParameterException: Wrong IV length: must be 16 bytes long. but it is 64 bytes." Picture: http://i264.photobucket.com/albums/ii200/XeniuM05/bg_zps0a523659.png public class AES { public static void main(String[] args) throws Exception { byte[] encKey1 = new byte[128]; byte[] EncIV = new byte[256]; byte[] UnEncIV = new byte[128]; byte[] unCrypKey = new byte[128]; byte[] unCrypText = new byte[1424]; File f = new File("C://ftp//ciphertext.enc"); FileInputStream fis = new FileInputStream(F); byte[] EncText = new byte[(int) f.length()]; fis.read(encKey1); fis.read(EncIV); fis.read(EncText); EncIV = Arrays.copyOfRange(EncIV, 128, 256); EncText = Arrays.copyOfRange(EncText, 384, EncText.length); System.out.println(EncText.length); KeyStore ks = KeyStore.getInstance(KeyStore.getDefaultType()); char[] password = "lab1StorePass".toCharArray(); java.io.FileInputStream fos = new java.io.FileInputStream( "C://ftp//lab1Store"); ks.load(fos, password); char[] passwordkey1 = "lab1KeyPass".toCharArray(); PrivateKey Lab1EncKey = (PrivateKey) ks.getKey("lab1EncKeys", passwordkey1); Cipher rsaDec = Cipher.getInstance("RSA"); // set cipher to RSA decryption rsaDec.init(Cipher.DECRYPT_MODE, Lab1EncKey); // initalize cipher ti lab1key unCrypKey = rsaDec.doFinal(encKey1); // Decryps first key UnEncIV = rsaDec.doFinal(EncIV); //decryps encive byte array to undecrypted bytearray---- OBS! Error this is 64 BYTES big, we want 16? System.out.println("lab1key "+ unCrypKey +" IV " + UnEncIV); //-------CIPHERTEXT decryption--------- Cipher AESDec = Cipher.getInstance("AES/CBC/PKCS5Padding"); //---------convert decrypted bytearrays to acctual keys SecretKeySpec unCrypKey1 = new SecretKeySpec(unCrypKey, "AES"); IvParameterSpec ivSpec = new IvParameterSpec(UnEncIV); AESDec.init(Cipher.DECRYPT_MODE, unCrypKey1, ivSpec ); unCrypText = AESDec.doFinal(EncText); // Convert decrypted cipher bytearray to string String deCryptedString = new String(unCrypKey); System.out.println(deCryptedString); }

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• Adding line with text between pattern and next occurence of the same pattern in bash

  - by kasper

  I am writing a bash script that modifies a file that looks like this: --- usr1 --- data data data data data data data data data data data data --- usr2 --- data data data data data data data data --- usr3 --- data data data data --- endline --- One question is: How to add next user line --- usrn --- after last user data lines? Second one is: How to delete specific user data lines (data lines and --- userx ---) i.e. I would like to delete usr2 with all his data set. It must work on bash 2.05 :) and I think it will use awk or sed, but I'm not sure.

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• How to Load Data from Text File in MySQL?

  - by Taz

  I have this file availableHere Fields are separated by space and newline starts at new line. I am using this command to load data mysql> LOAD DATA LOCAL INFILE 'C:\\Documents and Settings\\Scan\\My Documents\\Downloads\\images_en.nt\\Sample4.txt' INTO TABLE NER.Images FIELDS TERMINATED BY' ' LINES TERMINATED BY '\n';' Only one row is loaded and if I execute again No row is loaded. Where is the problem? Data can be modified to reformat if required.

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• Designing DAL in .NET to be "data-source independent" and not just "database independent" ?

  - by Munish Goyal

  How to design such flexible DAL (specifically in .NET) ? What interfaces .NET provides and what should be done on my own ? Its a greenfield project starting with SQL Server as data source but in future, parts of it will move to different NoSQL type of datastores. Also, we may need to experiment with lot of different datastores (like some data may have to go with Cassandra, some with RDBMS, some to other DHT etc.) Therefore easily switchable access layer will be needed. All i know right now is the 'data' and 'operations needed on that data'.

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• Resources to learn about engineering aspects of data analytics (OLAP, warehousing, ETL, etc.)

  - by JT

  I'm a math/stats guy, interested in learning more about the engineering aspects of "data analytics" (this may be an overly broad term, this is a case of "I don't know what I don't know", so I'm not sure how to be more specific). I'm fine with manipulating and analyzing the data once it's already stored somewhere and I can access it, and I'm fine with writing scripts and SQL queries (and have a general knowledge of things like normalization). What I don't know is the whole engineering process of capturing and storing the data. For example, terms I've heard thrown about that I only vaguely understand the meaning of include: - OLAP, OLTP - Data warehousing - ETL - ??? What's a good book (or any other resource) to learn about these kinds of things? What are things I should know about database design (normalization seems kinda "obvious" to me, something I would have done even before I knew the term -- is there anything else?)? In other words, for jobs falling under the umbrella term of "analytics engineer", what kinds of things should I know?

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• Generate and merge data with python multiprocessing

  - by Bobby

  I have a list of starting data. I want to apply a function to the starting data that creates a few pieces of new data for each element in the starting data. Some pieces of the new data are the same and I want to remove them. The sequential version is essentially: def create_new_data_for(datum): """make a list of new data from some old datum""" return [datum.modified_copy(k) for k in datum.k_list] data = [some list of data] #some data to start with #generate a list of new data from the old data, we'll reduce it next newdata = [] for d in data: newdata.extend(create_new_data_for(d)) #now reduce the data under ".matches(other)" reduced = [] for d in newdata: for seen in reduced: if d.matches(seen): break #so we haven't seen anything like d yet seen.append(d) #now reduced is finished and is what we want! I want to speed this up with multiprocessing. I was thinking that I could use a multiprocessing.Queue for the generation. Each process would just put the stuff it creates on, and when the processes are reducing the data, they can just get the data from the Queue. But I'm not sure how to have the different process loop over reduced and modify it without any race conditions or other issues. What is the best way to do this safely? or is there a different way to accomplish this goal better?

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• Is there a lightweight multipart/form-data parser in C or C++?

  - by Hongli

  I'm looking at integrating multipart form-data parsing in a web server module so that I can relieve backend web applications (often written in dynamic languages) from parsing the multipart data themselves. The multipart grammar (RFC 2046) looks non-trivial and if I implement it by hand a lot of things can go wrong. Is there already a good, lightweight multipart/form-data parser written in C or C++? I'm looking for one with no external dependencies other than the C or C++ standard library. I don't need email attachment handling or buffered I/O classes or a portability runtime or whatever, just multipart/form-data parsing. Things that I've considered: GMime - depends on glib, so no go. libapreq - too large, depends on APR, badly documented, no unit tests. I've also looked at writing a parser with Ragel, but I can't figure out how to do it because the grammar is not static: the boundary can change arbitrarily.

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• How to read a file with variable multi-row data in Python

  - by dr.bunsen

  I have a file that is about 100Mb that looks like this: #meta data 1 skadjflaskdjfasljdfalskdjfl sdkfjhasdlkgjhsdlkjghlaskdj asdhfk #meta data 2 jflaksdjflaksjdflkjasdlfjas ldaksjflkdsajlkdfj #meta data 3 alsdkjflasdjkfglalaskdjf This file contains one row of meta data that corresponds to several, variable length data containing only alpha-numeric characters. What is the best way to read this data into a simple list like this: data = [[#meta data 1, skadjflaskdjfasljdfalskdjflsdkfjhasdlkgjhsdlkjghlaskdjasdhfk], [#meta data 2, jflaksdjflaksjdflkjasdlfjasldaksjflkdsajlkdfj], [#meta data 3, alsdkjflasdjkfglalaskdjf]] My initial idea was to use the read() method to read the whole file into memory and then use regular expressions to parse the data into the desired format. Is there a better more pythonic way? All metadata lines start with an octothorpe and all data lines are all alpha-numeric. Thanks!

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• How to process large block data visualization with Flex?

  - by hydra1983

  I know that's a big topic. However, it's better to know some general ideas to handle such problems. I have an application which requires Flex to render statistics data calculated instantly on the client side from a downloaded data set. The problems are: the data set is large and needs more than 10 seconds to be downloaded. there are some filters to control the statistics calculation algorithms. If user changes the filters, it would take a long time to recalculate the result and freeze the UI.

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• html5 uploader + jquery drag & drop: how to store file data with FormData?

  - by lauthiamkok

  I am making a html5 drag and drop uploader with jquery, below is my code so far, the problem is that I get an empty array without any data. Is this line incorrect to store the file data - fd.append('file', $thisfile);? $('#div').on( 'dragover', function(e) { e.preventDefault(); e.stopPropagation(); } ); $('#div').on( 'dragenter', function(e) { e.preventDefault(); e.stopPropagation(); } ); $('#div').on( 'drop', function(e){ if(e.originalEvent.dataTransfer){ if(e.originalEvent.dataTransfer.files.length) { e.preventDefault(); e.stopPropagation(); // The file list. var fileList = e.originalEvent.dataTransfer.files; //console.log(fileList); // Loop the ajax post. for (var i = 0; i < fileList.length; i++) { var $thisfile = fileList[i]; console.log($thisfile); // HTML5 form data object. var fd = new FormData(); //console.log(fd); fd.append('file', $thisfile); /* var file = {name: fileList[i].name, type: fileList[i].type, size:fileList[i].size}; $.each(file, function(key, value) { fd.append('file['+key+']', value); }) */ $.ajax({ url: "upload.php", type: "POST", data: fd, processData: false, contentType: false, success: function(response) { // .. do something }, error: function(jqXHR, textStatus, errorMessage) { console.log(errorMessage); // Optional } }); } /*UPLOAD FILES HERE*/ upload(e.originalEvent.dataTransfer.files); } } } ); function upload(files){ console.log('Upload '+files.length+' File(s).'); }; then if I use another method is that to make the file data into an array inside the jquery code, var file = {name: fileList[i].name, type: fileList[i].type, size:fileList[i].size}; $.each(file, function(key, value) { fd.append('file['+key+']', value); }); but where is the tmp_name data inside e.originalEvent.dataTransfer.files[i]? php, print_r($_POST); $uploaddir = './uploads/'; $file = $uploaddir . basename($_POST['file']['name']); if (move_uploaded_file($_POST['file']['tmp_name'], $file)) { echo "success"; } else { echo "error"; } as you can see that tmp_name is needed to upload the file via php... html, <div id="div">Drop here</div>

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• Is there any reason why someone would want to create an Core Data model programmatically?

  - by mystify

  I wonder in which cases it would be good to make an NSManagedObjectModel completely programmatically, with NSEntityDescription instances and all this stuff. I'm that kind of person who prefers to code programmatically, rejecting Interface Builder. But when it comes to Core Data, I have a hard time figuring out why I should kill my time NOT using the nice Xcode Data Modeler tool. And since data models are stuck to a given state (except when you want to do some ugly migration operations where thinks probably go wrong and users get mad, really mad), I see no big sense in a data model that's made programmatically for the purpose of changing it all the time. Did I miss something?

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• MySQL Cluster data nodes - slow SELECTs

  - by Boyan Georgiev

  Hi to all. First off, I'm new to MySQL Cluster. This is my pain: I've managed to setup a MySQL Cluster with two data nodes, two SQL nodes and one management server. Everything works pretty well, except the following: my data nodes are spread across an intranet link which incurs latency into communications between the data nodes. Apparently, due to MySQL Cluster's internal partitioning schemes, when my PHP application pulls data from the cluster via SELECT queries, parts of the data are pulled from both data nodes. This makes the page appear onscreen REALLY slowly. If I bring one data node offline, the data can only be pulled from that single remaining data node, and thus, the final result (HTML output) appears on the screen in a very timely fashion. So, my question is this: can the data nodes/cluster be told to pull data from partitions stored only on a particular data node?

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• How to structure a Visual Studio project for the data access layer

  - by Akk

  I currently have a project that uses various DB access technologies mainly for showcasing or for demos. Currently we have: Namespace App.Data (App.Data.dll) Folder NHibernate Folder EntityFramework Folder LinqToSql The above structure is ok as we only use Sql Server as the DB. But going forward we will be including Oracle, MySql etc. So what would be a better structure with this in mind? I thought about: Namespace App.Data.SqlServer (App.Data.SqlServer.dll) Folder NHibernate Folder EntityFramework Folder LinqToSql Or would it just be better to have separate assemblies for each database and access technology?: Namespace App.Data.SqlServer.NHibernate (App.Data.SqlServer.NHibernate.dll) Namespace App.Data.SqlServer.EntityFramework(App.Data.SqlServer.EntityFramework.dll) Namespace App.Data.Oracle.NHibernate (App.Data.Oracle.NHibernate.dll) Namespace App.Data.MySql.NHibernate (App.Data.MySql.Oracle.dll)

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