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  • Dealing with large number of text strings

    - by Fadrian
    My project when it is running, will collect a large number of string text block (about 20K and largest I have seen is about 200K of them) in short span of time and store them in a relational database. Each of the string text is relatively small and the average would be about 15 short lines (about 300 characters). The current implementation is in C# (VS2008), .NET 3.5 and backend DBMS is Ms. SQL Server 2005 Performance and storage are both important concern of the project, but the priority will be performance first, then storage. I am looking for answers to these: Should I compress the text before storing them in DB? or let SQL Server worry about compacting the storage? Do you know what will be the best compression algorithm/library to use for this context that gives me the best performance? Currently I just use the standard GZip in .NET framework Do you know any best practices to deal with this? I welcome outside the box suggestions as long as it is implementable in .NET framework? (it is a big project and this requirements is only a small part of it) EDITED: I will keep adding to this to clarify points raised I don't need text indexing or searching on these text. I just need to be able to retrieve them in later stage for display as a text block using its primary key. I have a working solution implemented as above and SQL Server has no issue at all handling it. This program will run quite often and need to work with large data context so you can imagine the size will grow very rapidly hence every optimization I can do will help.

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  • How to easily apply a function to a collection in C++

    - by Jesse Beder
    I'm storing images as arrays, templated based on the type of their elements, like Image<unsigned> or Image<float>, etc. Frequently, I need to perform operations on these images; for example, I might need to add two images, or square an image (elementwise), and so on. All of the operations are elementwise. I'd like get as close as possible to writing things like: float Add(float a, float b) { return a+b; } Image<float> result = Add(img1, img2); and even better, things like complex ComplexCombine(float a, float b) { return complex(a, b); } Image<complex> result = ComplexCombine(img1, img2); or struct FindMax { unsigned currentMax; FindMax(): currentMax(0) {} void operator(unsigned a) { if(a > currentMax) currentMax = a; } }; FindMax findMax; findMax(img); findMax.currentMax; // now contains the maximum value of 'img' Now, I obviously can't exactly do that; I've written something so that I can call: Image<float> result = Apply(img1, img2, Add); but I can't seem to figure out a generic way for it to detect the return type of the function/function object passed, so my ComplexCombine example above is out; also, I have to write a new one for each number of arguments I'd like to pass (which seems inevitable). Any thoughts on how to achieve this (with as little boilerplate code as possible)?

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  • [PHP/MySQL] How to create text diff web app

    - by Adam Kiss
    Hello, idea I would like to create a little app for myself to store ideas (the thing is - I want it to do MY WAY) database I'm thinking going simple: id - unique id of revision in database text_id - identification number of text rev_id - number of revision flags - various purposes - expl. later title - self expl. desc - description text - self expl . flags - if I (i.e.) add flag rb;65, instead of storing whole text, I just said, that whenever I ask for latest revision, I go again in DB and check revision 65 Question: Is this setup the best? Is it better to store the diff, or whole text (i know, place is cheap...)? Does that revision flag make sense (wouldn't it be better to just copy text - more disk space, but less db and php processing. php I'm thinking, that I'll go with PEAR here. Although main point is to open-edit-save, possiblity to view revisions can't be that hard to program and can be life-saver in certain situations (good ideas got deleted, saving wrong version, etc...). However, I've never used PEAR in a long-time or full-project relationship, however, brief encounters in my previous experience left rather bad feeling - as I remember, it was too difficult to implement, slow and humongous to play with, so I don't know, if there's anything better. why? Although there are bazillions of various time/project/idea management tools, everything lacks something for me, whether it's sharing with users, syncing on more PCs, time-tracking, project management... And I believe, that this text diff webapp will be for internal use with various different tools later. So if you know any good and nice-UI-having project management app with support for text-heavy usage, just let me know, so I'll save my time for something better than redesigning the weel.

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  • How can I pull multiple rows from a MySQL table and use all of them automatically for the same thing

    - by Rob
    Basically, I have multiple URL's stored in a MySQL table. I want to pull those URLs from the table and have cURL connect to all of them. Currently I've been storing the URL's in the local script, but I've added a new page that I can add and remove them from the database, and I'd like the page to reflect it appropriately. Here is what I currently have: $sites[0]['url'] = "http://example0.com "; $sites[1]['url'] = "http://example1.com"; $sites[2]['url'] = "http://example2.com"; $sites[3]['url'] = "http://example3.com"; foreach($sites as $s) { // Now for some cURL to run it. $ch = curl_init($s['url']); //load the urls and send GET data curl_setopt($ch, CURLOPT_TIMEOUT, 2); //No need to wait for it to load. Execute it and go. curl_exec($ch); //Execute curl_close($ch); //Close it off } Now I assume it can't be too amazingly difficult to do, I just don't know how. So if you could point me in the right direction, I'd be grateful. But if you supply me with some code, please comment it appropriately so that I can understand what each line is doing.

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  • Framework/service for hosting and managing files

    - by Peteris Caune
    Hi, in a webapp I'm building there is a planned side feature of supporting product illustrations and manuals (so pictures and PDFs), possibly arranged in galleries. As I'd rather not implement from scratch all of the uploading, managing and serving of this content, I'm looking for existing solutions which I could integrate. For example, I'm considering Flickr--users of webapp specify their Flickr username and then use some naming convention to link objects in my webapp with pictures uploaded in their Flickr account. Very little code to write from my side, maybe just some API calls that proxy Flickr APIs, since Flickr would handle picture uploading, organizing them in sets, storing them in cloud and serving them in various sizes etc. One drawback here is that either all of the the pictures are public or I have to deal with interactive Flickr authorization. Also not sure if Flickr would be happy being used in such manner. What other online services or libraries/frameworks I should look at? My webapp is written in Python/Pylons, so Python libraries would be preferred. I'm already using some of Amazon infrastructure, so frontends to Amazon S3 would be cool. For online services, RESTful API would be nice.

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  • How to handle product ratings in a database

    - by Mel
    Hello, I would like to know what is the best approach to storing product ratings in a database. I have in mind the following two (simplified, and assuming a MySQL db) scenarios: Scenario 1: Create two columns in the product table to store number of votes and the sum of all votes. Use columns to get an average on the product display page: products(productedID, productName, voteCount, voteSum) Pros: I will only need to access one table, and thus execute one query to display product data and ratings. Cons: Write operations will be executed in a table whose original purpose is only to furnish product data. Scenario 2: Create an additional table to store ratings. products(productID, productName) ratings(productID, voteCount, voteSum) Pros: Isolate ratings into a separate table, leaving the products table to furnish data on available products. Cons: I will have to execute two separate queries on product page requests (one for data and another for ratings). In terms of performance, which of the following two approaches is best: Allow users to execute an occasional write query to a table that will handle hundreds of read requests? Execute two queries at every product page, but isolate the write query into a separate table. I'm a novice to database development, and often find myself struggling with simple questions such as these. Many thanks,

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  • Boost shared_ptr use_count function

    - by photo_tom
    My application problem is the following - I have a large structure foo. Because these are large and for memory management reasons, we do not wish to delete them when processing on the data is complete. We are storing them in std::vector<boost::shared_ptr<foo>>. My question is related to knowing when all processing is complete. First decision is that we do not want any of the other application code to mark a complete flag in the structure because there are multiple execution paths in the program and we cannot predict which one is the last. So in our implementation, once processing is complete, we delete all copies of boost::shared_ptr<foo>> except for the one in the vector. This will drop the reference counter in the shared_ptr to 1. Is it practical to use shared_ptr.use_count() to see if it is equal to 1 to know when all other parts of my app are done with the data. One additional reason I'm asking the question is that the boost documentation on the shared pointer shared_ptr recommends not using "use_count" for production code.

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  • Pointers into elements in a container

    - by Pillsy
    Say I have an object: struct Foo { int bar_; Foo(int bar) bar_(bar) {} }; and I have an STL container that contains Foos, perhaps a vector, and I take // Elsewhere... vector<Foo> vec; vec.push_back(Foo(4)); int *p = &(vec[0].bar_) This is a terrible idea, right? The reason is that vector is going to be storing its elements in a dynamically allocated array somewhere, and eventually, if you add enough elements, it will have to allocate another array, copy over all the elements of the original array, and delete the old array. After that happens, p points to garbage. This is why many operations on a vector will invalidate iterators. It seems like it would be reasonable to assume that an operation that would invalidate iterators from a container will also invalidate pointers to data members of container elements, and that if an operation doesn't invalidate iterators, those pointers will still be safe. However, many reasonable assumptions are false. Is this one of them?

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  • Python: Sorting array with custom pattern

    - by Binka
    In my little project here I have sorted a list in decending order, however, my goal is to sort it in this custom pattern. (largest - smallest - next largest - next smallest -)etc. In java I was able to do this like this... My goal is to do the same thing but in python, except backwards. Any ideas on how to convert that last for loop that does the wackysort into python and make it go backwards? public static void wackySort(int[] nums){ //first, this simply sorts the array by ascending order. int sign = 0; int temp = 0; int temp2 = 0; for (int i = 0; i < nums.length; i++){ for (int j = 0; j < nums.length -1; j++){ if (nums[j] > nums[j+1]){ temp = nums[j]; nums[j] = nums[j+1]; nums[j+1] = temp; } } } //prepare for new array to actually do the wacky sort. System.out.println(); int firstPointer = 0; int secondPointer = nums.length -1; int[] newarray = new int[nums.length]; int size = nums.length; //for loop that increments by two taking second slot replacing the last (n-1) term for (int i = 0; i < nums.length -1; i+=2){ newarray[i] = nums[firstPointer++]; newarray[i+1] = nums[secondPointer--]; } //storing those values back in the nums array for (int i = 0; i < nums.length; i++){ nums[i] = newarray[i]; } }

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  • Difficulty Inserting from HTML form into MySQL (created in Workbench)

    - by Chaya Cooper
    I created a MySQL database in Workbench 5.2.35 for purposes of storing and using information submitted in html forms but I'm having difficulty inserting records from the html form. The relevant SQL script was saved as Demo2.sql, the schema is C2F, and the table is customer_info. I wasn't sure if that was the problem, so I tried replacing the database name (Demo2) with the schema name, but that didn't work either. My html file includes: form action="insert.php" method="post" The insert.php file states: ?php $con = mysql_connect("localhost","root","****"); if (!$con) { die('Could not connect: ' . mysql_error()); } mysql_select_db("Demo2", $con); $sql="INSERT INTO customer_info(fname, lname, user, password, reminder, answer) VALUES ('$_POST[fname]','$_POST[lname]','$_POST[user]','$_POST[password]','$_POST[reminder]','$_POST[answer]')"; if (!mysql_query($sql,$con)) { die('Error: ' . mysql_error()); } echo "1 record added"; mysql_close($con) ? I've also tried INSERT INTO c2f.customer_info(fname, lname, etc. and INSERT INTO 'c2f'.'customer_info'

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  • Simple Oracle File repository with folder hierarchy

    - by Ope
    I have an application that stores large amount of files (XML and binary) in folder hierarchies. Currently the main method is storing them in file system or using a legacy CMS, which we want to get rid of. The CMS supports Oracle and a customer wants to keep the files in Oracle because of enterprise policies (backup etc.) The question is: Is there a simple implementation of file repository with folder hierarchy for Oracle? What I am looking for is a small .Net component or example code (PL/SQL and/or .Net) that would have the following methods: Create, Delete, Exists Folder CRUD file Move and potentially Copy file or directory Access to files and folders with paths like "/root/folder1/folder2/file.xml" Ability to get all the files and folders in a folder and potentially also the entire directory tree Tree traversal, getting the parent, all children etc. needs to be fast. I need the implementation in .Net, but if it was just the stored procedures, I could create the .Net calling code. I have pointers to generic articles for creating hierarchies in DB, so if I need to do it from scratch, I know where to start. What I am asking here, is there already an implementation that I could take without doing this from scratch? It seems like such a generic requirement... If the answer is a CMS, Document management system or such it should be Open Source or at least quite cheap (some hundreds / server) and it should be possible to deploy it XCopy - hopefully only couple of DLL:s. I do not need - or want - a full featured big CMS with dozens of dlls and especially not an msi-installation. I have tried to google this, but the words "repository", "CMS", "file hierarchy" etc. give so many answers, the searches are pretty much useless. Thanks, OPe

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  • How to debug properly and find causes for crashes?

    - by Newbie
    I dont know what to do anymore... its hopeless. I'm getting tired of guessing whats causing the crashes. Recently i noticed some opengl calls crashes programs randomly on some gfx cards. so i am getting really paranoid what can cause crashes now. The bad thing on this crash is that it crashes only after a long time of using the program, so i can only guess what is the problem. I cant remember what changes i made to the program that may cause the crashes, its been so long time. But luckily the previous version doesnt crash, so i could just copypaste some code and waste 10 hours to see at which point it starts crashing... i dont think i want to do that yet. The program crashes after i make it to process the same files about 5 times in a row, each time it uses about 200 megabytes of memory in the process. It crashes at random times while and after the reading process. I have createn a "safe" free() function, it checks the pointer if its not NULL, and then frees the memory, and then sets the pointer to NULL. Isn't this how it should be done? I watched the task manager memory usage, and just before it crashed it started to eat 2 times more memory than usual. Also the program loading became exponentially slower every time i loaded the files; first few loads didnt seem much slower from each other, but then it started rapidly doubling the load speeds. What should this tell me about the crash? Also, do i have to manually free the c++ vectors by using clear() ? Or are they freed after usage automatically, for example if i allocate vector inside a function, will it be freed every time the function has ended ? I am not storing pointers in the vector. -- Shortly: i want to learn to catch the damn bugs as fast as possible, how do i do that? Using Visual Studio 2008.

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  • Could git do not store history of specific folders when working with git-svn?

    - by Timofey Basanov
    In short: Is there a way to disable storing full history for specific folders in git-svn repo? We have pretty large SVN repo with big checkout. I would like to migrate it to Git for my local development, because Git speeds up update and status commands orders of magnitude. When I simply do git svn clone it creates very big repo. Big enough to be bigger then my whole HDD. The problem lies in binary directories for which history is too large. Latest binaries are required for proper local build, but history is not required at all for my development process. I will never change them myself. I would like to store only latest versions for specific folders, or may be a history, but for no more than a week. I could only found filter for git svn fetch, which excludes specific folders at all. This is not exactly what I need. It's OK with me to have Cron task which deletes history from specific folders, but I do not know how to make one. Also Cron does not solve problem of first git svn clone. P.S. SVN repository structure could not be changed by any means.

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  • Setting the type of a field in a superclass from a subclass (Java)

    - by Ibolit
    Hi. I am writing a project on Google App Engine, within it I have a number of abstract classes that I hope I will be able to use in my future projects, and a number of concrete classes inheriting from them. Among other abstract classes I have an abstract servlet that does user management, and I hava an abstract user. The AbstractUser has all the necessary fields and methods for storing it in the datastore and telling whether the user is registered with my service or not. It does not implement any project specific functionality. The abstract servlet that manages users, refers only to the methods declared in the AbstractUser class, which allows it to generate links for logging in, logging out and registering (for unregistered users). In order to implement the project-specific user functionality I need to subclass the Abstract user. The servlets I use in my project are all indirect descendants from that abstract user management servlet, and the user is a protected field in it, so the descendant servlets can use it as their own field. However, whenever i want to access any project specific method of the concrete user, i need to cast it to that type. i.e. (abstract user managing servlet) ... AbstractUser user = getUser(); ... abstract protected AbstractUser getUser(); (project-specific abstract servlet) @Override protected AbstractUser getUser() { return MyUserFactory.getUser(); } any other project specific servlet: int a = ((ConcreteUser) user).getA(); Well, what i'd like to do is to somehow make the type of “user” in the superclass depend on something in the project-specific abstract class. Is it at all possible? And i don't want to move all the user-management stuff into a project-specific layer, for i would like to have it for my future projects already written :) Thank you for your help.

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  • Using Zend_Db and multiple tables

    - by Yacoby
    I have a normalized database that stores locations of files on the internet. A file may have multiple locations spread across different sites. I am storing the urls in two parts (Site.UrlStart, FileLocation.UrlEnd). The UrlEnd is the part unique to that file (for the site). Simplified Db structure: I am using Zend_Db as my ORM (If it is that), with classes for the tables inheriting from Zend_Db_Table_Abstract. The issue is that retrieving the location data (e.g. the url) requires the use of multiple tables and as far as I can make out and I would either have to use both table classes (thereby exposing my table structure) or scatter sql all over my application, neither of which sound appealing. The only solution I can see is to create a façade that acts like Zend_Db_Table_Abstract (Maybe inherits from it?) and hides the fact that the data is actually on two tables. My questions are as follows: Am I going in the right direction in creating a façade class (Are there other alternatives)? Should the facade class inherit from Zend_Db_Table_Abstract?

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  • Can I make a derived class inherit a derived member from its base class in Java?

    - by Eric
    I have code that looks like this: public class A { public void doStuff() { System.out.print("Stuff successfully done"); } } public class B extends A { public void doStuff() { System.out.print("Stuff successfully done, but in a different way"); } public void doMoreStuff() { System.out.print("More advanced stuff successully done"); } } public class AWrapper { public A member; public AWrapper(A member) { this.member = member; } public void doStuffWithMember() { a.doStuff(); } } public class BWrapper extends AWrapper { public B member; public BWrapper(B member) { super(member); //Pointer to member stored in two places: this.member = member; //Not great if one changes, but the other does not } public void doStuffWithMember() { member.doMoreStuff(); } } However, there is a problem with this code. I'm storing a reference to the member in two places, but if one changes and the other does not, there could be trouble. I know that in Java, an inherited method can narrow down its return type (and perhaps arguments, but I'm not certain) to a derived class. Is the same true of fields?

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  • How to current snapshot of MySQL Table and store it into CSV file(after creating it) ?

    - by Rachel
    I have large database table, approximately 5GB, now I wan to getCurrentSnapshot of Database using "Select * from MyTableName", am using PDO in PHP to interact with Database. So preparing a query and then executing it // Execute the prepared query $result->execute(); $resultCollection = $result->fetchAll(PDO::FETCH_ASSOC); is not an efficient way as lots of memory is being user for storing into the associative array data which is approximately, 5GB. My final goal is to collect data returned by Select query into an CSV file and put CSV file at an FTP Location from where Client can get it. Other Option I thought was to do: SELECT * INTO OUTFILE "c:/mydata.csv" FIELDS TERMINATED BY ',' OPTIONALLY ENCLOSED BY '"' LINES TERMINATED BY "\n" FROM my_table; But I am not sure if this would work as I have cron that initiates the complete process and we do not have an csv file, so basically for this approach, PHP Scripts will have to create an CSV file. Do a Select query on the database. Store the select query result into the CSV file. What would be the best or efficient way to do this kind of task ? Any Suggestions !!!

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  • How to check whether data is stored in core data ?

    - by Warrior
    i am new to iphone development. I am trying to save a static values in to core data database.I want to check whether the data is stored to the database, i am not able to retrieve the data from the database, so i want to check myself whether i made mistake in retrieving the data or in storing the data itself. NSManagedObjectContext *context = [self managedObjectContext]; NSManagedObject *event = [NSEntityDescription insertNewObjectForEntityForName:@"Event" inManagedObjectContext:context]; [event setValue:fname forKey:@"firstname"]; [event setValue:lname forKey:@"lastname"]; i put the above code in the submit button of my formclass. when i restart the app i fetch the data in main view class using this code NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init]; NSEntityDescription *entity = [NSEntityDescription entityForName:@"Event" inManagedObjectContext:self.managedObjectContext]; [fetchRequest setEntity:entity]; NSError *error; NSArray *items = [self.managedObjectContext executeFetchRequest:fetchRequest error:&error]; for (Event *info in items) { NSLog(@"the selected value is : %@", [info valueForKey:@"firstname"]); } [fetchRequest release]; i dont know where i am going wrong.Please help me out.Thanks.

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  • Retrieving values from a table in HTML using jQuery?

    - by Mo
    Hi i was just wondering whats the best way to retrieve the following labels and values from this HTMl code using jquery and storing them in to a array or hash map of some sort where i have for e.g "DataSet:" : "prod" or ["Dataset", "Prod"]? <table id="metric_summary"> <tbody> <tr class="editable_metrics"> <td><label>DataSet:</label></td> <td><input name="DataSet" value="prod"></td> </tr> <tr class="editable_metrics"> <td><label>HostGroup:</label></td> <td><input name="HostGroup" value="MONITOR-PORTAL-IAD"></td> </tr> <tr class="editable_metrics"> <td><label>Host:</label></td> <td><input name="Host" value="ALL"></td> </tr> <tr class="editable_metrics"> <td><label>Class:</label></td> <td><input name="Class" value="CPU"></td> </tr> <tr class="editable_metrics"> <td><label>Object:</label></td> <td><input name="Object" value="cpu"></td> </tr> <tr class="editable_metrics"> <td><label>Metric:</label></td> <td><input name="Metric" value="CapacityCPUUtilization"></td> </tr> thanks

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  • Store data in tableview to NSUserDefaults

    - by Jozef Vrana
    Tricks.h file #import "Tricks.h" @implementation Tricks static NSMutableArray *trickList = nil; +(NSMutableArray *)trickList { if(!trickList){ trickList = [[NSMutableArray alloc]init]; } return trickList; } @end Tricks.m file @interface Tricks : NSObject @property(strong, nonatomic) NSString *trickName; Method for adding objects to array -(IBAction)saveAction:(id)sender { Tricks *trick = [[Tricks alloc]init]; trick.trickName = self.trickLabel.text; [[Tricks trickList]insertObject:trick atIndex:0]; [self.navigationController popViewControllerAnimated:YES]; } In .h file of UITabelview class I am making a reference to tricks class, but I am sure there is error on this line. @property (strong, nonatomic) Tricks *tricks; In cellForRow method I am storing data _trick = [[NSMutableDictionary alloc]initWithObjectsAndKeys:trick,nil]; NSUserDefaults *defaults=[NSUserDefaults standardUserDefaults]; [defaults setObject:_trick forKey:@"numberArray"]; [defaults synchronize]; NSLog(@"%@",_trick); In .m class of UITableview in viewDidLoad I want to retrieve data if([[NSUserDefaults standardUserDefaults] objectForKey:@"numberArray"] != nil) { _tricks = [[NSUserDefaults standardUserDefaults] objectForKey:@"numberArray"]; } Thanks for advices

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  • float** allocation limit + serialized struct problem. Need advice!

    - by jmgunn
    basically im getting an allocation limit error/warning when i create a float** array. the function i am calling to fill the float** retrieves data from a struct loaded from a file. The function works fine when i use one object but when i load 2 objects into memory i get the limit error. I am pretty sure this is to do with byte alignment or a similar thing because my struct is saved with a float** member which i am sure you are not susposed to do !?! Please confirm this! The next question i have now is how to save/serialize the float** member of this struct? I cant really afford to put an upper bound on the array ie "float [10000][3]" because i need/want to use this structure as a base for many other types of objects that may have well under the upper bound. Stroking my chin here! Any help/advice will recieve my highest gratitude. BTW these said struct objects will be used in a game/graphics package, the float** is a float[3] array for storing vertices in a model. Much thanks in advance

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  • Best way to store data in database when you don't know the type

    - by stiank81
    I have a table in my database that represents datafields in a custom form. The DataField gives some representation of what kind of control it should be represented with, and what value type it should take. Simplified you can say that I have 2 entities in this table - Textbox taking any string and Textbox only taking numbers. Now I have the different values stored in a separate table, referencing the datafield definition. What is the best way to store the data value here, when the type differs? One possible solution is to have the FieldValue table hold one field per possible value type. Now this would certainly be redundant, but at least I would get the value stored in its correct form - simplifying queries later. FieldValue ---------- Id DataFieldId IntValue DoubleValue BoolValue DataValue .. Another possibility is just storing everything as String, and casting this in the queries. I am using .Net with NHibernate, and I see that at least here there is a Projections.Cast that can be used to cast e.g. string to int in the query. Either way in these two solutions I need to know which type to use when doing the query, but I will know that from the DataField, so that won't be a problem. Anyway; I don't think any of these solutions sounds good. Are they? Or is there a better way?

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  • Creating a dictionary with list of lists in Python

    - by ghbhatt
    I have a huge file (with around 200k inputs). The inputs are in the form: A B C D B E F C A B D D I am reading this file and storing it in a list as follows: text = f.read().split('\n') This splits the file whenever it sees a new line. Hence text is like follows: [[A B C D] [B E F] [C A B D] [D]] I have to now store these values in a dictionary where the key values are the first element from each list. i.e the keys will be A, B, C, D. I am finding it difficult to enter the values as the remaining elements of the list. i.e the dictionary should look like: {A: B C D; B: E F; C: A B D; D: 0} I have done the following: inlinkDict = {} for doc in text: adoc= doc.split(' ') docid = adoc[0] inlinkDict[docid] = inlinkDict.get(docid,0) + {I do not understand what to put in here} Please help as to how should i add the values to my dictionary. It should be 0 if there are no elements in the list except for the one which will be the key value. Like in example for 0.

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  • SQL Server: Why use shorter VARCHAR(n) fields?

    - by chryss
    It is frequently advised to choose database field sizes to be as narrow as possible. I am wondering to what degree this applies to SQL Server 2005 VARCHAR columns: Storing 10-letter English words in a VARCHAR(255) field will not take up more storage than in a VARCHAR(10) field. Are there other reasons to restrict the size of VARCHAR fields to stick as closely as possible to the size of the data? I'm thinking of Performance: Is there an advantage to using a smaller n when selecting, filtering and sorting on the data? Memory, including on the application side (C++)? Style/validation: How important do you consider restricting colunm size to force non-sensical data imports to fail (such as 200-character surnames)? Anything else? Background: I help data integrators with the design of data flows into a database-backed system. They have to use an API that restricts their choice of data types. For character data, only VARCHAR(n) with n <= 255 is available; CHAR, NCHAR, NVARCHAR and TEXT are not. We're trying to lay down some "good practices" rules, and the question has come up if there is a real detriment to using VARCHAR(255) even for data where real maximum sizes will never exceed 30 bytes or so. Typical data volumes for one table are 1-10 Mio records with up to 150 attributes. Query performance (SELECT, with frequently extensive WHERE clauses) and application-side retrieval performance are paramount.

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  • Determining difference in timestamps for two values in the same MySQL table

    - by JayRizzo03
    I am relatively new to programming in PHP, so I apologize if this is a rather simple question. I have a MySQL database table called MachineReports that contains the following values: ReportNum(primary key, auto increment), MachineID and Timestamp Here is some example data: |ReportNum | MachineID | Timestamp | |1 | AD3203 | 2012-11-18 06:32:28| |2 | AD3203 | 2012-11-19 04:00:15| |3 | BC4300 | 2012-11-19 04:00:15| What I am attempting to do is find the difference in timestamps in seconds for each machine ID by iterating over each row set. I am getting stuck on the best way to do this, however. Here is the code I've written so far: <?php include '../dbconnect/dbconnect.php'; $machineID=[]; //Get a list of all MachineIDs in the database foreach($dbh->query('SELECT DISTINCT(MachineID) FROM MachineReports') as $row) { array_push($machineID, $row[0]); } for($i=0;$i<count($machineID);$i++){ foreach($dbh->query("SELECT MachineID FROM MachineReports WHERE MachineID='$machineID[$i]' ORDER BY MachineID") as $row) { //code to associate each machineID with two time stamps goes here } } ? This code just lists out the contents of the table row by row. My ultimate goal is to find the difference in timestamps for a certain MachineID. One of the things I've considered is using a multidimensional array in php - using the $machineID as the key and then storing the timestamp inside the array the key points to. However, I'm uncertain how to do that since my query parses row by row. I have quite a few questions. 1) Is this the most efficient way to be doing this? I suspect my database table design may not be the best. 2)What would be the best way to determine the difference in timestamps for a certain machineID? Even just a pointer to a topic that would prompt me to think about this in a different way would be helpful - I'm not afraid to do research. Thanks!

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