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• How do I handle the messages for a simple web-based live chat, on the server side?

  - by Carson Myers

  I'm building a simple live chat into a web application running on Django, but one thing I'm confused about is how I should store the messages between users. The chat will support multiple users, and a chat "session" is composed of users connected to one user that is the "host." The application is a sort of online document collaboration thing, so user X has a document, and users Y and Z would connect to user X to talk about the document, and that would be one chat session. If user Y disconnected for five minutes, and then signed back in and reconnected to user X, he should not get any of the messages shared between users X and Z while he was away. if users X, Y, and Z can have a chat session about user X's document, then users X and Y can connect to a simultaneous, but separate discussion about user Z's document. How should I handle this? Should I keep each message in the database? Each message would have an owner user and a target user (the host), and a separate table would be used to connect users with messages (which messages are visible to what users). Or should I store each session as an HTML file on the server, which messages get appended to? The problem is, I can't just send messages directly between clients. They have to be sent to the server in a POST request, and then each client has to periodically check for the messages in a GET request. Except I can't just have each message cleared after a client fetches it, because there could be multiple clients. How should I set this up? Any suggestions?

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• MySql "comments" parameter as descriptor?

  - by Nick

  So, I'm trying to learn a lot at once, and this place is really helpful! I'm making a little running log website for myself and maybe a few other people, and I have it so that the user can add workouts for each day. With each workout, I have a variety of information the user can fill out for the workout, such as running distance, time, quality of run, course, etc... I store this in a MySql database as a table with fields titled "distance", "time", "runquality", etc... Now, these field titles don't match up with what I want displayed on the running log, so I was thinking of using the "Comments" attribute for a field to store its human-readable title--thus the field "runquality" would have "Quality of run" as its comment, and then I would pull the comment with a SQL query and display it instead of the field name. Is this a good theoretical/practical way of going about it? And what sort of SQL would I use to pull the comment for the field anyway? Secondly, suppose I want to add the ability for the user to create their own workout descriptors. So say a user wants to add a "temperature" descriptor for their workout. Should I create a script that adds fields to my workout table, or should I create a separate table listing only workout descriptors and somehow link the descriptor table with the "contents" table? I haven't learned any theory about database design or anything so any help is appreciated!

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• Request size limitation when using MultipartHttpServletRequest of Spring 3.0

  - by Spiderman

  I'd like to know what is the size limitation if I upload list of files in one client's form submition using HTTP multipart content type. On the server side I am using Spring's MultipartHttpServletRequest to handle the request. mM questions: Is there should be different file size limitation and total request size limitation or file size is the only limitation and the request is capable of uploading 100s of files as lonng as they are not too large. Doest the Spring request wrapper read the complete request and store it in the JAVA heap memory or it store temporaray files of it to be able to use big quota. Is the use of reading the httpservlet request in streaming would change the size limitation than using complete http request read at-once by the application server. What is the bottleneck of this process - Java heap size, the quota of the filesystem on which my web-server runs, the maximum allowed BLOB size that the DataBase in which I am gonna save the file alows? or Spring internal limitations? Related threads that still don't have exact answer to this: does-spring-framework-support-streaming-mode-in-mutlipart-requests is-there-a-way-to-get-raw-http-request-stream-from-java-servlet-handler how-to- drop-body-of-a-request-after-checking-headers-in-servlet apache-commons-fileupload-throws-malformedstreamexception

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• mysql: storing arbitrary data

  - by Hailwood

  Background: I was asking a question on stack overflow regarding creating tables on the fly where this conversation ensued: This smells like a terrible idea! In fact, it smells just like this one. What in the world do you want to use this for? – deceze @deceze: very true, However, How else would you store the contents of these CSV files. They must be stored in mysql for indexing. The only solid fact about them is that they all have a mobile column with a standard format. The CSV can have an arbitrary amount of columns with an arbitrary amount of rows. They can (with no exaggeration) range from a single row, 35 column csv to an 80k row single column CSV. I am open to other ideas. – Hailwood There are many solutions for this, from attribute-value schemas to JSON storage and NoSQL storage. Open a new question about it. Whatever you do though, don't dynamically create tables! – deceze Question: So my question is, What would you say is the best way to store this data? Are you in agreement with deceze about not creating dynamic tables?

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• Reload images in a UIWebView after they have been downloaded by a background thread

  - by dantastic

  I have an application that frequently checks in with a server and downloads a batch of articles to the iphone. The articles are in html and just stored using core data. An article has 0-n images on the page. Downloading all associated images at the same time as the text will be too slow and take too much bandwidth. Users are not likely to open every article. If they open an article once it is likely they will open it several times. So I want to download and store the images locally when they are needed. These articles are listed in a UITableView. When you tap an article you pop open a UIWebView that displays the article. I have a function that checks if I have downloaded the images associated with the article already. If I have I just pop open the the UIWebView - everything works fine. If I don't have the images downloaded I go off and download them and store them to my Documents directory. Although this i working, the app is hanging while the images are downloading. Not very tidy. I want the article to open in a snap and download the images with the article open. So what I've done is I check if the images are downloaded, if they aren't I go ahead and just "touch" the files I need and load the webview. The UIWebView opens up but the images referenced contain no data. Then in a background thread I download the images and overwrite the "dummy" ones. This will save the images and everything but it won't reload the images in my current UIWebView. I have to go back out of the article back back in again to see the images. Are there any ways around this? reloading just an image in a UIWebView?

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• Save Bitmap image in a location in C#

  - by acadia

  Hello, I have this function to store the bmp image in a desired location as shown below My question is, how do I save the image in C:\temp folder by default, instead of opening the filedialog box? I want to specify sd.fileName=picname+".bmp" and store it in c:\temp by default. I tried to specify Thanks for your help in advance. I tried to public static bool SaveDIBAs( string picname, IntPtr bminfo, IntPtr pixdat ) { SaveFileDialog sd = new SaveFileDialog(); sd.FileName = picname; sd.Title = "Save bitmap as..."; sd.Filter = "Bitmap file (*.bmp)|*.bmp|TIFF file (*.tif)|*.tif|JPEG file (*.jpg)|*.jpg|PNG file (*.png)|*.png|GIF file (*.gif)|*.gif|All files (*.*)|*.*"; sd.FilterIndex = 1; if( sd.ShowDialog() != DialogResult.OK ) return false; Guid clsid; if( ! GetCodecClsid( sd.FileName, out clsid ) ) { MessageBox.Show( "Unknown picture format for extension " + Path.GetExtension( sd.FileName ), "Image Codec", MessageBoxButtons.OK, MessageBoxIcon.Information ); return false; } IntPtr img = IntPtr.Zero; int st = GdipCreateBitmapFromGdiDib( bminfo, pixdat, ref img ); if( (st != 0) || (img == IntPtr.Zero) ) return false; st = GdipSaveImageToFile( img, sd.FileName, ref clsid, IntPtr.Zero ); GdipDisposeImage( img ); return st == 0; }

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• Issue with Multiple Text Fields and SharedObject Storing

  - by user1662660

  I'm currently working on an AIR for iOS application in Flash CS6. I'm trying to store multiple pieces of data from various text inputs; i.e "name_txt", "number_txt" etc. I have the following code working for a local save file; import flash.events.Event; import flash.desktop.NativeApplication; import flash.events.Event; var n1:String = so.data.Number1; var so:SharedObject = SharedObject.getLocal("TravelPal"); emerg1.text = n1; emerg1.addEventListener(Event.CHANGE, updateEmerg1); function updateEmerg1 (e:Event):void { so.data.Number1 = emerg1.text; so.flush(); } NativeApplication.nativeApplication.addEventListener(Event.EXITING, onExit); function onExit(e:Event):void { so.flush(); } Now as soon as I create multiple text inputs and attempt to store them in my SharedObject, the whole system just falls apart. None of the text gets saved, even the previously working ones. I'm pretty new to ShardObject usage. What am I missing here? Is this a good way to go about storing multiple text inputs?

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• Unserializing an API return object (PHP/Ebay API)

  - by DavidYell

  I have been working with the Ebay api for a project and have found it great. I have however found a problem now, more PHP related. When I read my items from Ebay, I store a bunch of details in the database. Currently, just for the sake of it really, I serialize the whole return object and store it in the database in a related table. The idea being, that when I display my information, I have all the details to hand should I need them. The problem arises in that the pricing information is always in a sub object. [ConvertedAdjustmentAmount] => __PHP_Incomplete_Class Object ( [__PHP_Incomplete_Class_Name] => eBayAmountType [_] => 0 [currencyID] => USD ) As you can see when I unserialize my object, my cunning plan falls foul of the Incomplete class problem. I have checked the following question, without success. http://stackoverflow.com/questions/965611/forcing-access-to-php-incomplete-class-object-properties The main issue lies, as far as I can see, in that the price class is stored in the Ebay api, so how do I recreate it? I have been reading this page, http://uk3.php.net/manual/en/function.unserialize.php and trying to figure out, unserialize_callback_func which I can't figure out either, so any help would be appreciated!

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• Java HashMap containsKey always false

  - by Dennis

  I have the funny situation, that I store a Coordinate into a HashMap<Coordinate, GUIGameField>. Now, the strange thing about it is, that I have a fragment of code, which should guard, that no coordinate should be used twice. But if I debug this code: if (mapForLevel.containsKey(coord)) { throw new IllegalStateException("This coordinate is already used!"); } else { ...do stuff... } ... the containsKey always returns false, although I stored a coordinate with a hashcode of 9731 into the map and the current coord also has the hashcode 9731. After that, the mapForLevel.entrySet() looks like: (java.util.HashMap$EntrySet) [(270,90)=gui.GUIGameField@29e357, (270,90)=gui.GUIGameField@ca470] What could I have possibly done wrong? I ran out of ideas. Thanks for any help! public class Coordinate { int xCoord; int yCoord; public Coordinate(int x, int y) { ...store params in attributes... } ...getters & setters... @Override public int hashCode() { int hash = 1; hash = hash * 41 + this.xCoord; hash = hash * 31 + this.yCoord; return hash; } }

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• How to map a 0..1 to 1 relationship in Entity Framework 3

  - by sako73

  I have two tables, Users, and Address. A the user table has a field that maps to the primary key of the address table. This field can be null. In plain english, Address exist independent of other objects. A user may be associated with one address. In the database, I have this set up as a foreign key relationship. I am attempting to map this relationship in the Entity Framework. I am getting errors on the following code: <Association Name="fk_UserAddress"> <End Role="User" Type="GenesisEntityModel.Store.User" Multiplicity="1"/> <End Role="Address" Type="GenesisEntityModel.Store.Address" Multiplicity="0..1" /> <ReferentialConstraint> <Principal Role="Address"> <PropertyRef Name="addressId"/> </Principal> <Dependent Role="User"> <PropertyRef Name="addressId"/> </Dependent> </ReferentialConstraint> </Association> It is giving a "The Lower Bound of the multiplicity must be 0" error. I would appreciate it if anyone could explain the error, and the best way to solve it. Thanks for any help.

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• Getting a UIImage from MySQL using PHP and jSON

  - by Daniel

  I'm developing a little news reader that retrieves the info from a website by doing a POST request to a URL. The response is a jSON object with the unread-news. E.g. the last news on the App has a timeStamp of "2013-03-01". When the user refreshes the table, it POSTS "domain.com/api/api.php?newer-than=2013-03-01". The api.php script goes to the MySQL database and fetches all the news posted after 2013-03-01 and prints them json_encoded. This is // do something to get the data in an array echo $array_of_fetched_data; for example the response would be [{"title": "new app is coming to the market", "text": "lorem ipsum dolor sit amet...", image: XXX}] the App then gets the response and parses it, obtaining an NSDictionary and adds it to a Core Data db. NSDictionary* obtainedNews = [NSJSONSerialization JSONObjectWithData:responseData options:kNilOptions error:&error]; My question is: How can I add an image to the MySQL database, store it, pass it using jSON trough a POST HTTP Request and then interpret it as an UIImage. It's clear that to store an UIImage in CoreData, they must be transform into/from NSData. How can I pass the NSData back and forth to a MySQL db using php and jSON? How should I upload the image to the db? (Serialized, as a BLOB, etc)

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• Cocoa - calling a VIEW method from the CONTROLLER

  - by eemerge

  Hello everyone, Got a little problem i asked about it before but maybe i didnt ask properly. I have a cocoa application, which amongst other things, must do the following task: - load some images from the disk, store them in an array and display them in a custom view. In the Interface Builder i have a CustomView and an OBJECT that points to TexturesController.h The custom view is a custom class, TextureBrowser. Below is the code for the controller and view: TexturesController #import <Cocoa/Cocoa.h> @class TextureBrowser; @interface TexturesController : NSObject { IBOutlet NSTextField *logWindow; IBOutlet TextureBrowser *textureView; NSMutableArray *textureList; } @property textureView; -(IBAction)loadTextures:(id)sender; -(IBAction)showTexturesInfo:(id)sender; @end TextureBrowser @interface TextureBrowser : NSView { NSMutableArray *textures; } @property NSMutableArray *textures; -(void)loadTextureList:(NSMutableArray *)source; @end These are just the headers. Now , what i need to do is: when loadTextures from the TexturesController is called, after i load the images i want to send this data to the view (TextureBrowser), for example, store it in the NSMutableArray *textures. I tried using the -(void)loadTextureList:(NSMutableArray*)source method from the view, but in the TextureController.m i get a warning : No -loadTextureList method found This is how i call the method : [textureView loadTextureList: textureList]; And even if i run it with the warning left there, the array in the view class doesnt get initialised. Maybe im missing something...maybe someone can give a simple example of what i need to do and how to do it (code). Thanks in advance.

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• php how to serialize array of objects?

  - by hequ

  Hello, I have small class called 'Call' and I need to store these calls into a flat file. I've made another class called 'CallStorage' which contains an array where I put these calls into. My problem is that I would like to store this array to disk so I could later read it back and get the calls from that array. I've tried to achieve this using serialize() and unserialize() but these seems to act somehow strange and part of the information gets lost. This is what I'm doing: //write array to disk $filename = $path . 'calls-' . $today; $serialized = serialize($this->array); $fp = fopen($filename, 'a'); fwrite($fp, $serialized); fclose($fp); //read array from serialized file $filename = $path . 'calls-' . $today; if (file_exists($filename)) { $handle = fopen($filename, 'r'); $contents = fread($handle, filesize($filename)); fclose($handle); $unserialized = unserialize($contents); $this->setArray($unserialized); } Can someone see what I'm doing wrong, or what. I've also tried to serialize and write arrays that contains plain strings. I didn't manage to get that working either.. I have a Java background so I just can't see why I couldn't just write an array to disk if it's serialized. :)

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• PostgreSQL storing paths for reference in scripts

  - by Brian D.

  I'm trying to find the appropriate place to store a system path in PostgreSQL. What I'm trying to do is load values into a table using the COPY command. However, since I will be referring to the same file path regularly I want to store that path in one place. I've tried creating a function to return the appropriate path, but I get a syntax error when I call the function in the COPY command. I'm not sure if this is the right way to go about it, but I'll post my code anyway. COPY command: COPY employee_scheduler.countries (code, name) FROM get_csv_path('countries.csv') WITH CSV; Function Definition: CREATE OR REPLACE FUNCTION employee_scheduler.get_csv_path(IN file_name VARCHAR(50)) RETURNS VARCHAR(250) AS $$ DECLARE path VARCHAR(200) := E'C:\\Brian\\Work\\employee_scheduler\\database\\csv\\'; file_path VARCHAR(250) := ''; BEGIN file_path := path || file_name; RETURN file_path; END; $$ LANGUAGE plpgsql; If anyone has a different idea on how to accomplish this I'm open to suggestions. Thanks for any help!

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• Html.RadioButton group defaulting to 0

  - by awrigley

  Hi A default value of 0 is creeping into a Surveys app I am developing, for no reason that I can see. The problem is as follows: I have a group of Html.RadioButtons that represent the possible values a user can choose to answer a survey question (1 == Not at all, 2 == A little, 3 == A lot). I have used a tinyint datatype, that does not allow null, to store the answer to each question. The view code looks like this: <ol class="SurveyQuestions"> <% foreach (SurveyQuestion question in Model.Questions) { string col = question.QuestionColumn; %> <li><%=question.QuestionText%> <ul style="float:right;" class="MultiChoice"> <li><%= Html.RadioButton(col, "1")%></li> <li><%= Html.RadioButton(col, "2")%></li> <li><%= Html.RadioButton(col, "3")%></li> </ul> <%= Html.ValidationMessage(col, "*") %> </li> <% } %> </ol> [Note on the above code:] Each survey has about 70 questions, so I have put the questions text in one table, and store the results in a different table. I have put the Questions into my form view model (hence Model.Questions); the questions table has a field called QuestionColumn that allows me to link up the answer table column to the question, as shown above (<%= Html.RadioButton(col, "1")%, etc) [/Note] However, when the user DOESN'T answer the question, the value 0 is getting inserted into the database column. As a result, I don't get what I expect, ie, a validation error. In no place have I stipulated a default value of 0 for the fields in the answers table. So what is happening? Any ideas?

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• Managing Many to Many relationships in asp.net Wizard Control

  - by Luis

  Say I have this entity with a lot of attributes. In the input form I have decided to implement a wizard control so I can collect information about this entity in several steps. The problem is that I need to collect information that has been modeled has many to many relationships. I am planning to use a telerik gridview to manage this (add/edit/delete), the problem is where do I store that data since the entity in a insert form is not created on the database yet. OK so I can store all that info in temporary lists residing in the viewstate, waiting for the final submit where I dump all that in the DB, but one of the steps I am collecting files...now storing files in the viewstate is out of the question, same as as storing them in the session... I have been thinking of implementing in a way that the user has to submit some info first (say first 3 steps), commit the data to the database creating the parent entity and then start inserting all the childs entities...but this will get weird as it's confusing since on the first steps you not saving the data to the DB and on the next ones you are commiting directly... Anyone has any thoughts on this? Thanks

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• Distributed Cache with Serialized File as DataStore in Oracle Coherence

  - by user226295

  Weired but I am investigating the Oracle Coherence as a substitue for distribute cache. My primarr problem is that we dont have distribituted cache as such as of now in our app. Thats my major concern. And thats what I want to implement. So, lets say if I take up a machine and start a new (3rd) reading process, it will be able to connect to the cache and listen to the cache and will have a full set of cache triplicated (as of now its duplicated) Now thats waste from a common person stanpoint too. The size of the cache is 2 GB and without going distibuted its limiting us. Thats bring me to Coheremce. But now, we dont have database as persistent store too. we have the archival processes as our persistent store. (90 days worth of data) Ok now multiply that with soem where around 2 GB * 90 (thats the bare minimum we want to keep). Preliminary/Intermediate analysis of Coherence as a solution. And a (supposedly) brilliant thought crossed my mind. Why not have this as persistant storage with my distributed cache. Does Oracle Coherence support that. I will get rid of archiving infrastructure too (i hate daemon archiving processes). For some starnge reasons, I dont wanna go to the DB to replace those flat files. What say?, can Coherence be my savior? Any other stable alternate too. (Coherence is imposed on me by big guys, FYI)

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• MySQL query against pseudo-key-value pair data in WordPress custom query

  - by andrevr

  I'm writing a custom WordPress query to use some of the data which the Woothemes Diarise theme creates. Diarise is an event planner theme with calendar blah, blah... and uses custom fields to store the event start and end dates in WP custom fields in the *wp_postmeta* table, which implements a key-value store. So for each post in the "event" category, there are 2 records in *wp_postmeta*, named *event_start_date* and *event_end_date* that I'm interested in. The task is to compare a tourist's arrival and departure dates with the start and end dates of events, yielding a what's on list of events available. We thought we'd killed it with a grand flash of logic, that goes like this: Disregard any event that ends before the tourist arrives, and any that begin after the departure date. I wrote this query: SELECT wposts.* FROM wp_posts wposts LEFT JOIN wp_postmeta wpostmeta ON wposts.ID = wpostmeta.post_id LEFT JOIN wp_term_relationships ON (wposts.ID = wp_term_relationships.object_id) LEFT JOIN wp_term_taxonomy ON (wp_term_relationships.term_taxonomy_id = wp_term_taxonomy.term_taxonomy_id) WHERE wp_term_taxonomy.taxonomy = 'category' AND wp_term_taxonomy.term_id IN(3,4) AND ( wpostmeta.meta_key = 'event_start_date' AND NOT ( concat(subst(wpostmeta.meta_value,7,4),'-',subst(wpostmeta.meta_value,4,2),'-',subst(wpostmeta.meta_value,1,2) > '2010-07-31' ) ) AND ( wpostmeta.meta_key = 'event_end_date' AND NOT ( concat(subst(wpostmeta.meta_value,7,4),'-',subst(wpostmeta.meta_value,4,2),'-',subst(wpostmeta.meta_value,1,2) < '2010-05-01' ) ) ) ORDER BY wpostmeta.meta_value ASC And, of course it returns no records. The problem I believe is in the dual reference to wpostmeta.meta_key, but how to get around that?

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• MySQL help, counting information on last records

  - by ee12csvt

  I need some advice I have two tables, one holds unique serial numbers of items (items) and the other holds status changes and other information for these items (details) The Tables are set up as follows Item itemID itemName itemDate details detID itemID modlvl status detDate All items have at least one record in the details table, but over time the status has changed or the modification level has changed (Both of these are identified by numbers which are held in other appropriate tables) and a new record is created each time the status/modlvl changes I want to display a table on my webpage using php that identifies the different mod levels of the items and shows a count of each of the current status of the items EDIT Hi Ronnis, This is an example of the data in the tables and what I want to achieve The current Mod Levels range from 1 to 3 Status representations are 1 In Use 2 In Store 3 Being repaired 4 In Transit 5 For Disposal 6 Disposed 7 Lost Item itemID OrigMod created 1000 1 2009-10-01 22:12:12 1001 1 2009-10-01 22:12:12 1002 1 2009-10-01 22:12:12 1003 1 2009-10-01 22:12:12 1004 1 2009-10-01 22:12:12 1005 1 2009-10-01 22:12:12 1006 1 2009-10-01 22:12:12 1007 1 2009-10-01 22:12:12 1008 1 2009-10-01 22:12:12 1009 1 2009-10-01 22:12:12 1010 1 2009-10-01 22:12:12 Details detID itemID modlvl detDate status 1 1000 1 2009-10-01 1 2 1001 1 2009-10-01 1 3 1002 1 2009-10-01 1 4 1003 1 2009-10-01 1 5 1004 1 2009-10-01 1 6 1005 1 2009-10-01 1 7 1006 1 2009-10-01 1 8 1007 1 2009-10-01 1 9 1008 1 2009-10-01 1 10 1009 1 2009-10-01 1 11 1010 1 2009-10-01 1 12 1001 1 2010-02-01 2 13 1001 1 2010-02-03 4 14 1001 1 2010-03-01 3 15 1000 1 2010-03-14 2 16 1001 2 2010-04-01 4 17 1006 1 2010-04-01 2 18 1001 2 2010-04-03 2 19 1006 1 2010-04-14 4 20 1006 1 2010-05-01 5 21 1002 1 2010-05-02 2 22 1003 1 2010-05-10 2 23 1010 1 2010-06-01 2 24 1006 1 2010-06-18 6 25 1010 1 2010-07-01 7 26 1007 1 2010-07-02 2 27 1007 1 2010-07-04 4 28 1003 1 2010-07-10 2 29 1007 1 2010-07-11 3 30 1007 2 2010-07-12 4 31 1007 2 2010-07-15 2 32 1001 2 2010-08-31 1 33 1001 2 2010-09-10 2 34 1001 2 2010-10-01 4 35 1008 1 2010-10-01 2 36 1001 2 2010-10-05 3 37 1008 1 2010-10-05 4 38 1008 1 2010-10-10 3 39 1001 3 2010-10-20 4 40 1001 3 2010-10-25 2 Using the tables above I want to get this result MoLvl Use Store Repd Transit Displ Dispd Lost Total 1 3 3 1 0 0 1 1 9 2 0 1 0 0 0 0 0 1 3 0 1 0 0 0 0 0 1 Total 3 5 1 0 0 1 1 11

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• Cassandra instead of MySQL for social networking app

  - by Christopher McCann

  I am in the middle of building a new app which will have very similar features to Facebook and although obviously it wont ever have to deal with the likes of 400,000,000 million users it will still be used by a substantial user base and most of them will demand it run very very quickly. I have extensive experience with MySQL but a social app offers complexities which MySQL is not well suited too. I know Facebook, Twitter etc have moved towards Cassandra for a lot of their data but I am not sure how far to go with it. For example would you store such things as user data - username, passwords, addresses etc in Cassandra? Would you store e-mails, comments, status updates etc in Cassandra? I have also read alot that something like neo4j is much better for representing the friend relationships used by social apps as it is a graph database. I am only just starting down the NoSQL route so any guidance is greatly appreciated. Would anyone be able to advise me on this? I hope I am not being too general!

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• MySql Check if NOW() falls within a weekday/time range

  - by Niall

  I have a table as follows: CREATE TABLE `zonetimes` ( `id` int(11) unsigned NOT NULL AUTO_INCREMENT, `zone_id` int(10) unsigned NOT NULL, `active_from_day` tinyint(1) unsigned NOT NULL DEFAULT '2', `active_to_day` tinyint(1) unsigned NOT NULL DEFAULT '2', `active_from` time NOT NULL, `active_to` time NOT NULL PRIMARY KEY (`id`) ) ENGINE=MyISAM ; So, a user could add a time entry starting on a particular day and time and ending on a particular day and time, eg: Between Monday 08:00 and Friday 18:00 or Between Thursday 15:00 and Tuesday 15:00 (Note the crossover at the end of the week). I need to query this data and determine if a zone is currently active (NOW(), DAYOFWEEK() etc)... This is turning out to be quite tricky. If I didn't have overlaps, eg: from 'Wednesday 8pm to Tuesday 4am' or from 'Thursday 4pm to Tuesday 4pm' this would be easy with BETWEEN. Also, need to allow a user to add for the entire week, eg: Monday 8am - Monday 8am (This should be easy enough, eg: where (active_from_day=active_to_day AND active_from=active_to) OR .. Any ideas? Note: I found a similar question here Timespan - Check for weekday and time of day in mysql but it didn't get an answer. One of the suggestions was to store each day as a separate row. I would much rather store one time span for multiple days though.

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• How to sum up a fetched result's number property based on the object's category?

  - by mr_kurrupt

  I have a NSFetchRequest that is returning all my saved objects (call them Items) and storing them in an NSMutableArray. Each of these Items have a category, an amount, and some other properties. My goal is to check the category of each Item and store the sum of the amounts for objects of the same category. So if I had these Items: Red; 10.00 Blue; 20.00 Green; 5.00 Red; 5.00 Green; 15.00 then I would have an array or other type of container than has: Red; 15.00 Blue; 20.00 Green; 20.00 What would be the best way to organize the data in such a manner? I was going to create a object class (call it Totals) that just has the category and amount. As I traverse through the fetch results in a for-loop, add Items with the same category in a Totals object an store them in a NSMutableArray. The problem I ran into with that is that I'm not sure how to check if an array contains a Totals object with a specific property. Specifically, a category that already exists. So if 'Red' exists, add the amount to it, otherwise create a new Totals object with category 'Red' and a the first Item's amount. Thanks.

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• error in C++, what to do ?: could not find an match for ostream::write(long *, unsigned int)

  - by Shantanu Gupta

  I am trying to write data stored in a binary file using turbo C++. But it shows me an error could not find an match for ostream::write(long *, unsigned int) I want to write a 4 byte long data into that file. When i tries to write data using char pointer. It runs successfully. But i want to store large value i.e. eg. 2454545454 Which can be stored in long only. I dont know how to convert 1 byte into bit. I have 1 byte of data as a character. Moreover what i m trying to do is to convert 4 chars into long and store data into it. And at the other side i want to reverse this so as to retrieve how many bytes of data i have written. long *lmem; lmem=new long; *lmem=Tsize; fo.write(lmem,sizeof(long));// error occurs here delete lmem; I am implementing steganography and i have successfully stored txt file into image but trying to retrieve that file data now.

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• How to map combinations of things to a relational database?

  - by Space_C0wb0y

  I have a table whose records represent certain objects. For the sake of simplicity I am going to assume that the table only has one row, and that is the unique ObjectId. Now I need a way to store combinations of objects from that table. The combinations have to be unique, but can be of arbitrary length. For example, if I have the ObjectIds 1,2,3,4 I want to store the following combinations: {1,2}, {1,3,4}, {2,4}, {1,2,3,4} The ordering is not necessary. My current implementation is to have a table Combinations that maps ObjectIds to CombinationIds. So every combination receives a unique Id: ObjectId | CombinationId ------------------------ 1 | 1 2 | 1 1 | 2 3 | 2 4 | 2 This is the mapping for the first two combinations of the example above. The problem is, that the query for finding the CombinationId of a specific Combination seems to be very complex. The two main usage scenarios for this table will be to iterate over all combinations, and the retrieve a specific combination. The table will be created once and never be updated. I am using SQLite through JDBC. Is there any simpler way or a best practice to implement such a mapping?

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• [Ruby] Modifying object inside a loop doesn't change object outside of the loop?

  - by Jergason

  I am having problems with modifying objects inside blocks and not getting the expected values outside the blocks. This chunk of code is supposed to transform a bunch of points in 3d space, calculate a score (the rmsd or root mean squared deviation), and store both the score and the set of points that produced that score if it is lower than the current lowest score. At the end, I want to print out the best bunch of points. first = get_transformed_points(ARGV[0]) second = get_transformed_points(ARGV[1]) best_rmsd = first.rmsd(second) best_points = second #transform the points around x, y, and z and get the rmsd. If the new points # have a smaller rmsd, store them. ROTATION = 30 #rotate by ROTATION degrees num_rotations = 360/ROTATION radians = ROTATION * (Math::PI/180) num_rotations.times do |i| second = second * x_rotate num_rotations.times do |j| second = second * y_rotate num_rotations.times do |k| second = second * z_rotate rmsd = first.rmsd(second) if rmsd < best_rmsd then best_points = second best_rmsd = rmsd end end end end File.open("#{ARGV[1]}.out", "w") {|f| f.write(best_points.to_s)} I can print out the points that are getting stored inside the block, and they are getting transformed and stored correctly. However, when I write out the points to a file at the end, they are the same as the initial set of points. Somehow the best_points = second chunk doesn't seem to be doing anything outside of the block. It seems like there are some scoping rules that I don't understand here. I had thought that since I declared and defined best_points above, outside of the blocks, that it would be updated inside the blocks. However, it seems that when the blocks end, it somehow reverts back to the original value. Any ideas how to fix this? Is this a problem with blocks specifically?

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