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  • Data storage advice needed: Best way to store location + time data?

    - by sobedai
    I have a project in mind that will require the majority of queries to be keyed off of lat/long as well as date + time. Initially, I was thinking of a standard RDBMS where lat, long, and the datetime field are properly indexed. Then, I began thinking of a document based system where the document was essentially a timestamp and each document has lat/long with in it. Each document could have n objects associated with it. I'm looking for advice on what would be the best type of storage engine for this sort of thing is - which of the above idea would be better or if there is something else completely that is the ideal solution. Thanks

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  • mysql - check if data exists across multiple tables

    - by Dd Daym
    I am currently running this query inside MySQL to check if the specified values exists within the table associated with them. SELECT COUNT(artist.artist_id), COUNT(album.album_id), COUNT(tracks.track_id) FROM artist, album, tracks WHERE artist.artist_id = 320295 OR album.album_id = 1234 OR tracks.track_id = 809 The result I get from running this query is all 1, meaning that all the statements after the WHERE clause is true. To further check the query's reliability, I changed the tracks.track_ = 809 to 802, which I know does not match. However the results displayed are still all 1, meaning that they were all successfully matched even when I purposefully inserted a value which would not have matched. How do I get it to show 1 for a match and 0 for no matches within the same query? EDIT: I have inserted an image of the query running

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  • Tree data structure gems compared?

    - by huug
    I want to you use a tree structure for my navigation. I was thinking about using Ancestry, but then I found this article about 7 plugins for providing a tree structure to your models. What are the pros/cons for each plugin/gem and above all: which one do you recommend? Tnx!

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  • Structure of Astar (A*) graph search data in C#

    - by Shawn Mclean
    How do you structure you graphs/nodes in a graph search class? I'm basically creating a NavMesh and need to generate the nodes from 1 polygon to the other. The edge that joins both polygons will be the node. I'll then run A* on these Nodes to calculate the shortest path. I just need to know how to structure my classes and their properties? I know for sure I wont need to create a fully blown undirected graph with nodes and edges.

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  • Core Data not-reverse relationship subquery

    - by user561485
    Hi, I have the following entities in CoreData: Village - villageID Bookmark - (relation) village There are multiple villages with each an unique villageID. I have a entity Bookmark which only has a relation to a Village entity; it isn't possible to make a reverse relation. Now I would like to get the village entities where there exists a Bookmark relation. I've red something about subqueries, but I can't get it right for this situation. It must be something like: Village.villageID IN (Bookmark.village.villageID) It isn't possible to get first all the Bookmarks and then loop to get all the Villages, because of the design of the framework. Can this be done in CoreData (I presume the answer is "Yes, of course!") and how?

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  • Replace data in MySQL table with data from another table

    - by Oli
    I am trying to modify an existing MySQL database for use in a new application. I have a table of items (table_items), which has multiple fields, including "ItemID" and "ItemName". I have another table (table_list) which has "ItemName" in it, but no ItemID. I need to either update this table to contain ItemID instead of ItemName, or create a new table which imports ItemIDs from table_items as opposed to the ItemName when table_list.ItemName = table_items.ItemName. I have tried the following: UPDATE table_list A, table_items B SET A.ItemName = B.ItemID WHERE A.ItemName = B.ItemName The current table has over 500,000 rows and every time i try this in PHPMyAdmin i get the error "the MySQl server has gone away". Any help greatly appreciated.

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  • AND NSPedicate on Core Data relationships

    - by jesse001
    I'm having trouble compounding NSPredicate with AND, although using OR works fine. Imagine 2 entities, Doctor and Patient. Doctors can have many patients and patients many doctors. I want to find doctors that, say, have both person1 and person2 as patients. I expected this to work but it returns none. NSPredicate *predicate = [NSPredicate predicateWithFormat:@"ANY patients matches 'person1&&person2'"]; If I change && to ||, I get all doctors that have person1 or person2 as I'd expect. Thanks in advance for your help.

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  • Core Data-Linking one-to-many relationships

    - by Stelmate
    I have a one-to-many relationship where each department has many employees. When I create a new employee object I just link it to the parent department manually by setting the property to the instance of the department I have fetched from my fetch request. However, this seems to be improper because when I try to access the set of employees from the department by simply accessing the .employees property on my department object instance it returns a 0 count. Isn't the fault suppose to fire once I access a property? Am I linking my parent/child objects incorrectly?

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  • What type of data store should I use for my ios app?

    - by mwiederrecht
    I am pretty new to ios and using servers so forgive me. I am building an ios app for research. I need to monitor things that the user does and then push it up to a server for analysis (yes, with user and IRB permission). On the client's side I need to keep quite a bit of data that won't really change except in the case of pulling an updated version from the server, and then a minimal amount of user-specific data. Most of the data I will collect needs to be pushed to a server for analysis and then can be deleted from the client side. I am struggling to figure out what kind of data store I need to use, especially since I am not quite sure how the pushing and pulling from the server process works yet. Does it make sense to use Core Data? XML? SQLite? I like the Core Data idea, but I am not sure what kind of problems I will run into when I need to send large amounts of data to it and from it from the server. I imagine I might need to send data in a different form than it is probably stored in on either end - so what kind of overhead am I likely to run into in the process of converting that data? Is there a good format to save stuff in that would work well for me on both ends AND for sending the data? As you can probably tell, I could use some advice. Thanks!

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  • C++, inject additional data in a method

    - by justik
    I am adding the new modul in some large library. All methods here are implemented as static. Let mi briefly describe the simplified model: typedef std::vector<double> TData; double test ( const TData &arg ) { return arg ( 0 ) * sin ( arg ( 1 ) + ...;} double ( * p_test ) ( const TData> &arg) = &test; class A { public: static T f1 (TData &input) { .... //some computations B::f2 (p_test); } }; Inside f1() some computations are perfomed and a static method B::f2 is called. The f2 method is implemented by another author and represents some simulation algorithm (example here is siplified). class B { public: static double f2 (double ( * p_test ) ( const TData &arg ) ) { //difficult algorithm working p_test many times double res = p_test(arg); } }; The f2 method has a pointer to some weight function (here p_test). But in my case some additional parameters computed in f1 for test() methods are required double test ( const TData &arg, const TData &arg2, char *arg3.... ) { } How to inject these parameters into test() (and so to f2) to avoid changing the source code of the f2 methods (that is not trivial), redesign of the library and without dirty hacks :-) ? The most simple step is to override f2 static double f2 (double ( * p_test ) ( const TData &arg ), const TData &arg2, char *arg3.... ) But what to do later? Consider, that methods are static, so there will be problems with objects. Thanks for your help.

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  • Data Structure / Hash Function to link Sets of Ints to Value

    - by Gaminic
    Given n integer id's, I wish to link all possible sets of up to k id's to a constant value. What I'm looking for is a way to translate sets (e.g. {1, 5}, {1, 3, 5} and {1, 2, 3, 4, 5, 6, 7}) to unique values. Guarantees: n < 100 and k < 10 (again: set sizes will range in [1, k]). The order of id's doesn't matter: {1, 5} == {5, 1}. All combinations are possible, but some may be excluded. All sets and values are constant and made only once. No deletes or inserts, no value updates. Once generated, the only operations taking place will be look-ups. Look-ups will be frequent and one-directional (given set, look up value). There is no need to sort (or otherwise organize) the values. Additionally, it would be nice (but not obligatory) if "neighboring" sets (drop one id, add one id, swap one id, etc) are easy to reach, as well as "all sets that include at least this set". Any ideas?

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  • Getting the data out of the data Formview

    - by QEDDave
    I have an ASP pg with a formview list control on it that hooks up to a sql database customer table I want to access the customer name outside the form. How do I: A) access the bound text box in the form view template? Something like Text1.text=formview1.customername.text (that doesn't work but that's the kinda thing) B) access the database field in the table that the sqlsource connects to to feed the formview Really appreciate the help. I bet it's easy to do but I'm just not getting there.

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  • Validating entered user data

    - by msfanboy
    Hello, this is a general question but I do a desktop application. Should I check for example the firstname exceeding 50 chars or is this a matter of taste? Or should I check for 50 chars because the user could flood my database with 10000000 chars ?

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  • Small questions on data structure

    - by John Graveston
    Hi, I'm trying to search the parent of a node with Kruskal's algorithm. My program works just fine, but I think I have heard of a method to improve the speed of the algorithm by reconstructing the tree while searching for the parent node and connecting it to the parent node. I'm pretty sure that I've heard of this somewhere, maybe in a lecture. Can anyone refresh my memory? And also, given a number of arrays, when searching for the minimum and the maximum value from a certain section of an array, what is the name of the tree that can calculate the minimum/maximum value from the array by making a binary tree that has the minimum/maximum value of each array in O(log N)?

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  • NSManagedObjectID into NSData

    - by papr
    I found this wonderful NSManagedObjectID. This would be very good for referencing an Entity/NSManagedObject/NSEntityDescription, right? Let's get an ID from an entity: NSEntityDescription *entity = [self newEntity]; NSManagedObjectID *objID = [entity objectID]; So... any idea how to get this objID into a string? Or better: NSData. Actually something to be able to save it to the NSUserDefaults. ;-) Btw: NSFetchRequest doesn't want to work in my case. I use an modified version of this example: answer of an old question.

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  • Modify an MP3 slightly to change the data appearence

    - by Léon Pelletier
    I'm thinking about encrypting MP3s in a database, so that when user is downloading them with his software desktop player, only the software can decrypt them. This part is not a problem. The problem is I don't want a user to upload an mp3 to the database, then check which changes have been made to the file so he can reverse-engineer the file or at least see which algorithm is used to encrypt the files. So, user uploads MP3-A, then it becomes MP3-B because it has been modified, and I encrypt it to MP3-C. And when decrypted, it sounds 99.99% like MP3-A. I know MP3 format is lossy, but I wonder if there's a way to convert audio with limited loss, or if I need to forget it right now.

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  • Rails: Modeling an optional relation in ActiveRecord

    - by Hassinus
    I would like to map a relation between two Rails models, where one side can be optionnal. Let's me be more precise... I have two models: Profile that stores user profile information (name, age,...) and User model that stores user access to the application (email, password,...). To give you more information, User model is handled by Devise gem for signup/signin. Here is the scenario of my app: 1/ When a user register, a new row is created in User table and there is an equivalent in Profile table. This leads to the following script: class User < ActiveRecord::Base belongs_to :profile end 2/ A user can create it's profile without registering (kind of public profile with public information), so a row in Profile doesn't have necessarily a User row equivalent (here is the optional relation, the 0..1 relation in UML). Question: What is the corresponding script to put in class Profile < AR::Base to map optionally with User? Thanks in advance.

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  • dictionary/map/key-value pairs data structure in C

    - by morgancodes
    How does one construct and access a set of key-value pairs in C? To use a silly simple example, let's say I want to create a table which translates between an integer and its square root. If I were writing javascript, I could just do this: var squareRoots = { 4: 2, 9: 3, 16: 4, 25: 5 } and then access them like: var squareRootOf25 = squareRoots[5] What's the prettiest way to do this in C? What if I want to use one type of enum as the key and another type of enum as the value?

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  • Data Structure Brushup (Java)

    - by Daddy Warbox
    This should be easy for many of you, but for me it's just another bit of rust needing to be chipped away as I get back into basic Java coding. Using bloody associative arrays for so long in other languages have turned me nice and spoiled. :P My problem is simple: I'm storing a set of objects, each containing a string and a number, in a list. I would like each object inserted into this list to be sorted alphabetically by its string. I would also like to be able to retrieve objects from the list by their string as well. I would like to do this as formally and/or efficiently as possible. Is there something already available in the Java standard libraries for this?

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  • Sesame Data Browser: filtering, sorting, selecting and linking

    - by Fabrice Marguerie
    I have deferred the post about how Sesame is built in favor of publishing a new update.This new release offers major features such as the ability to quickly filter and sort data, select columns, and create hyperlinks to OData. Filtering, sorting, selecting In order to filter data, you just have to use the filter row, which becomes available when you click on the funnel button: You can then type some text and select an operator: The data grid will be refreshed immediately after you apply a filter. It works in the same way for sorting. Clicking on a column will immediately update the query and refresh the grid.Note that multi-column sorting is possible by using SHIFT-click: Viewing data is not enough. You can also view and copy the query string that returns that data: One more thing you can to shape data is to select which columns are displayed. Simply use the Column Chooser and you'll be done: Again, this will update the data and query string in real time: Linking to Sesame, linking to OData The other main feature of this release is the ability to create hyperlinks to Sesame. That's right, you can ask Sesame to give you a link you can display on a webpage, send in an email, or type in a chat session. You can get a link to a connection: or to a query: You'll note that you can also decide to embed Sesame in a webpage... Here are some sample links created via Sesame: Netflix movies with high ratings, sorted by release year Netflix horror movies from the 21st century Northwind discontinued products with remaining stock Netflix empty connection I'll give more examples in a post to follow. There are many more minor improvements in this release, but I'll let you find out about them by yourself :-)Please try Sesame Data Browser now and let me know what you think! PS: if you use Sesame from the desktop, please use the "Remove this application" command in the context menu of the destkop app and then "Install on desktop" again in your web browser. I'll activate automatic updates with the next release.

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  • Webinar: NoSQL - Data Center Centric Application Enablement

    - by Charles Lamb
    NoSQL - Data Center Centric Application Enablement AUGUST 6 WEBINAR About the Webinar The growth of Datacenter infrastructure is trending out of bounds, along with the pace in user activity and data generation in this digital era. However, the nature of the typical application deployment within the data center is changing to accommodate new business needs. Those changes introduce complexities in application deployment architecture and design, which cascade into requirements for a new generation of database technology (NoSQL) destined to ease that complexity. This webcast will discuss the modern data centers data centric application, the complexities that must be dealt with and common architectures found to describe and prescribe new data center aware services. Well look at the practical issues in implementation and overview current state of art in NoSQL database technology solving the problems of data center awareness in application development. REGISTER NOW>> MORE INFORMATION >> NOTE! All attendees will be entered to win a guest pass to the NoSQL Now! 2013 Conference & Expo. About the Speaker Robert Greene, Oracle NoSQL Product Management Robert GreeneRobert Greene is a principle product manager / strategist for Oracle’s NoSQL Database technology. Prior to Oracle he was the V.P. Technology for a NoSQL Database company, Versant Corporation, where he set the strategy for alignment with Big Data technology trends resulting in the acquisition of the company by Actian Corp in 2012. Robert has been an active member of both commercial and open source initiatives in the NoSQL and Object Relational Mapping spaces for the past 18 years, developing software, leading project teams, authoring articles and presenting at major conferences on these topics. In his previous life, Robert was an electronic engineer developing first generation wireless, spread spectrum based security systems.

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