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  • What's the most efficient way to load data from a file to a collection on-demand?

    - by Dan
    I'm working on a java project that will allows users to parse multiple files with potentially thousands of lines. The information parsed will be stored in different objects, which then will be added to a collection. Since the GUI won't require to load ALL these objects at once and keep them in memory, I'm looking for an efficient way to load/unload data from files, so that data is only loaded into the collection when a user requests it. I'm just evaluation options right now. I've also thought of the case where, after loading a subset of the data into the collection, and presenting it on the GUI, the best way to reload the previously observed data. Re-run the parser/Populate collection/Populate GUI? or probably find a way to keep the collection into memory, or serialize/deserialize the collection itself? I know that loading/unloading subsets of data can get tricky if some sort of data filtering is performed. Let's say that I filter on ID, so my new subset will contain data from two previous analyzed subsets. This would be no problem is I keep a master copy of the whole data in memory. I've read that google-collections are good and efficient when handling big amounts of data, and offer methods that simplify lots of things so this might offer an alternative to allow me to keep the collection in memory. This is just general talking. The question on what collection to use is a separate and complex thing. Do you know what's the general recommendation on this type of task? I'd like to hear what you've done with similar scenarios. I can provide more specifics if needed.

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  • Best way to store chat messages and files

    - by Stnaire
    I would like to know what do you think about storing chat messages in a database? I need to be able to bind other stuff to them (like files, or contacts) and using a database is the best way I see for now. The same question comes for files, because they can be bound to chat messages, I have to store them in the database too.. With thousands of messages and files I wonder about performance drops and database size. What do you think considering I'm using PHP with MySQL/Doctrine?

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  • Having trouble storing a CRTP based class in a vector

    - by user366834
    Hi, Im not sure if this can be done, im just delving into templates so perhaps my understanding is a bit wrong. I have a Platoon of soldiers, the platoon inherits from a formation to pick up the formations properties, but because i could have as many formations as i can think of I chose to use the CRTP to create the formations, hoping that i could make a vector or array of Platoon to store the platoons in. but, of course, when i make a Platoon, it wont store it in the vector, "types are unrelated" Is there any way around this ? i read about "Veneers" which are similar and that they work with arrays but i cant get it to work, perhaps im missing something. here's some code: (sorry about the formatting, the code is here in my post but its not showing up for some reason ) template < class TBase > class IFormation { public : ~IFormation(){} bool IsFull() { return m_uiMaxMembers == m_uiCurrentMemCount; } protected: unsigned int m_uiCurrentMemCount; unsigned int m_uiMaxMembers; IFormation( unsigned int _uiMaxMembers ): m_uiMaxMembers( _uiMaxMembers ), m_uiCurrentMemCount( 0 ){} // only allow use as a base class. void SetupFormation( std::vector<MySoldier*>& _soldierList ){}; // must be implemented in derived class }; ///////////////////////////////////////////////////////////////////////////////// // PHALANX FORMATION class Phalanx : public IFormation<Phalanx> { public: Phalanx( ): IFormation( 12 ), m_fDistance( 4.0f ) {} ~Phalanx(){} protected: float m_fDistance; // the distance between soldiers void SetupFormation( std::vector<MySoldier*>& _soldierList ); }; /////////////////////////////////////////////////////////////////////////////////// // COLUMN FORMATINO class Column : public IFormation< Column > { public : Column( int _numOfMembers ): IFormation( _numOfMembers ) {} ~Column(); protected: void SetupFormation( std::vector<MySoldier*>& _soldierList ); }; I then use these formations in the platoon class to derive, so that platoon gets the relevant SetupFormation() function: template < class Formation > class Platoon : public Formation { public: **** platoon code here }; everything works great and as expected up until this point. now, as my general can have multiple platoons, I need to store the platoons. typedef Platoon< IFormation<> > TPlatoon; // FAIL typedef std::vector<TPlatoon*> TPlatoons; TPlatoon m_pPlatoons m_pPlatoons.push_back( new Platoon<Phalanx> ); // FAIL, types unrelated. typedef Platoon< IFormation< TPlatoon; fails because i need to specify a template parameter, yet specifying this will only allow me to store platoons created with the same template parameter. so i then created FormationBase class FormationBase { public: virtual bool IsFull() = 0; virtual void SetupFormation( std::vector<MySoldier*>& _soldierList ) = 0; }; and made IFormation publicly inherit from that, and then changed the typedef to typedef Platoon< IFormation< FormationBase > > TPlatoon; but still no love. now in my searches i have not found info that says this is possible - or not possible.

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  • Best practice how to store HTML in a database column

    - by tbrandao
    I have an application that modifies a table dynamically, think spreadsheet), then upon saving the form (which the table is part of) ,I store that changed table (with user modifications) in a database column named html_Spreadhseet,along with the rest of the form data. right now I'm just storing the html in a plain text format with basic escaping of characters... I'm aware that this could be stored as a separate file, the source table (html_workseeet) already is. But from a data handling perspective its easier to save the changed html table to and from a column so as to avoid having to come up with a file management strategy (which folder will this live in, now must include folder in backups, security issues now need to apply to files, how to sync db security with file system etc.), so to minimize these issues I'm only storing the ... part in the database column. My question is should I gzip the HTML , maybe use JSON, or some other format to easily store and retrieve the HTML from the database column, what is the best practice to store HTML content in a datbase? Or just store it as I currently am as an escaped text column?

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  • Can Parallel.ForEach be used safely with CloudTableQuery

    - by knightpfhor
    I have a reasonable number of records in an Azure Table that I'm attempting to do some one time data encryption on. I thought that I could speed things up by using a Parallel.ForEach. Also because there are more than 1K records and I don't want to mess around with continuation tokens myself I'm using a CloudTableQuery to get my enumerator. My problem is that some of my records have been double encrypted and I realised that I'm not sure how thread safe the enumerator returned by CloudTableQuery.Execute() is. Has anyone else out there had any experience with this combination?

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  • How to write a custom predicate for multi_index_containder with composite_key?

    - by Titan
    I googled and searched in the boost's man, but didn't find any examples. May be it's a stupid question...anyway. So we have the famous phonebook from the man: typedef multi_index_container< phonebook_entry, indexed_by< ordered_non_unique< composite_key< phonebook_entry, member<phonebook_entry,std::string,&phonebook_entry::family_name>, member<phonebook_entry,std::string,&phonebook_entry::given_name> >, composite_key_compare< std::less<std::string>, // family names sorted as by default std::greater<std::string> // given names reversed > >, ordered_unique< member<phonebook_entry,std::string,&phonebook_entry::phone_number> > > > phonebook; phonebook pb; ... // look for all Whites std::pair<phonebook::iterator,phonebook::iterator> p= pb.equal_range(boost::make_tuple("White"), my_custom_comp()); How should my_custom_comp() look like? I mean it's clear for me then it takes boost::multi_index::composite_key_result<CompositeKey> as an argumen (due to compilation errors :) ), but what is CompositeKey in that particular case? struct my_custom_comp { bool operator()( ?? boost::multi_index::composite_key_result<CompositeKey> ?? ) const { return blah_blah_blah; } }; Thanks in advance.

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  • I Can't update 12.04 to 12.10 ERROR:"gpg: WARNING: This key is not certified with a trusted signature!"

    - by jason328
    I'm trying to update to 12.10 from a 12.04 machine. When I ran the code sudo do-release-upgrade -d in my terminal and verified my password it checked for a new upgrade. I was then returned with this: gpg: Good signature from "Ubuntu Archive Automatic Signing Key <[email protected]>" gpg: WARNING: This key is not certified with a trusted signature! gpg: There is no indication that the signature belongs to the owner.` There of course is more but it looks like it may or may not be showing private information with it. What's causing this and how do I fix this.

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  • How to 'insert if not exists' in MySQL?

    - by warren
    I started by googling, and found this article which talks about mutex tables. I have a table with ~14 million records. If I want to add more data in the same format, is there a way to ensure the record I want to insert does not already exist without using a pair of queries (ie, one query to check and one to insert is the result set is empty)? Does a unique constraint on a field guarantee the insert will fail if it's already there? It seems that with merely a constraint, when I issue the insert via php, the script croaks.

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  • How do I specify a null relation in SQLAlchemy?

    - by Jesse
    Not sure what the correct title for this question should be. I have the following schema: Matters have a one-many relationship to WorkItems. WorkItems have a one-one (or one-zero) relationship to LineItems. I am trying to create the following relation between Matters and WorkItems Matter.unbilled_work_items = orm.relation(WorkItem, primaryjoin = (Matter.id == WorkItem.matter_id) and (WorkItem.line_item_id == None), foreign_keys = [WorkItem.matter_id, WorkItem.line_item_id], viewonly=True ) This throws: AttributeError: '_Null' object has no attribute 'table' That seems to be saying that the second clause in the primaryjoin returns an object of type _Null, but it seems to be expecting something with a "table" attribute. This seems like it should be pretty straightforward to me, am I missing something obvious?

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  • Cannot access NSDictionary

    - by michael blaize
    I created a JSON using a PHP script. I am reading the JSON and can see that the data has been correctly read. However, when it comes to access the objects I get unrecognized selector sent to instance... Cannot seem to find why that is after too many hours !!!! Any help would be great ! My code looks like that: `NSDictionary *json = [[NSDictionary alloc] init]; json = [NSJSONSerialization JSONObjectWithData:receivedData options:kNilOptions error:&error]; NSLog(@"raw json = %@,%@",json,error); NSMutableArray *name = [[NSMutableArray alloc] init]; [name addObjectsFromArray: [json objectForKey:@"name"]];` The code crashes when reaching the last line above. The output like this: raw json = ( { category = vacancies; link = "http://blablabla.com"; name = "name 111111"; tagline = "tagline 111111"; }, { category = vacancies; link = "http://blobloblo.com"; name = "name 222222222"; tagline = "tagline 222222222"; } ),(null) 2012-06-23 21:46:57.539 Wind expert[4302:15203] -[__NSCFArray objectForKey:]: unrecognized selector sent to instance 0xdcfb970 HELP !!!

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  • best practices question: How to save a collection of images and a java object in a single file? File

    - by Richard
    Hi all, I am making a java program that has a collection of flash-card like objects. I store the objects in a jtree composed of defaultmutabletreenodes. Each node has a user object attached to it with has a few string/native data type parameters. However, i also want each of these objects to have an image (typical formats, jpg, png etc). I would like to be able to store all of this information, including the images and the tree data to the disk in a single file so the file can be transferred between users and the entire tree, including the images and parameters for each object, can be reconstructed. I had not approached a problem like this before so I was not sure what the best practices were. I found XLMEncoder (http://java.sun.com/j2se/1.4.2/docs/api/java/beans/XMLEncoder.html) to be a very effective way of storing my tree and the native data type information. However I couldn't figure out how to save the image data itself inside of the XML file, and I'm not sure it is possible since the data is binary (so restricted characters would be invalid). My next thought was to associate a hash string instead of an image within each user object, and then gzip together all of the images, with the hash strings as the names and the XMLencoded tree in the same compmressed file. That seemed really contrived though. Does anyone know a good approach for this type of issue? THanks! Thanks!

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  • Insert Registration Data in MySQL using PHP

    - by J M 4
    I may not be asking this in the best way possible but i will try my hardest. Thank you ahead of time for your help: I am creating an enrollment website which allows an individual OR manager to enroll for medical testing services for professional athletes. I will NOT be using the site as a query DB which anybody can view information stored within the database. The information is instead simply stored, and passed along in a CSV format to our network provider so they can use as needed after the fact. There are two possible scenarios: Scenario 1 - Individual Enrollment If an individual athlete chooses to enroll him/herself, they enter their personal information, submit their payment information (credit/bank account) for processing, and their information is stored in an online database as Athlete1. Scenario 2 - Manager Enrollment If a manager chooses to enroll several athletes he manages/ promotes for, he enters his personal information, then enters the personal information for each athlete he wishes to pay for (name, address, ssn, dob, etc), then submits payment information for ALL athletes he is enrolling. This number can range from 1 single athlete, up to 20 athletes per single enrollment (he can return and complete a follow up enrollment for additional athletes). Initially, I was building the database to house ALL information regardless of enrollment type in a single table which housed over 400 columns (think 20 athletes with over 10 fields per athlete such as name, dob, ssn, etc). Now that I think about it more, I believe create multiple tables (manager(s), athlete(s)) may be a better idea here but still not quite sure how to go about it for the following very important reasons: Issue 1 If I list the manager as the parent table, I am afraid the individual enrolling athlete will not show up in the primary table and will not be included in the overall registration file which needs to be sent on to the network providers. Issue 2 All athletes being enrolled by a manager are being stored in SESSION as F1FirstName, F2FirstName where F1 and F2 relate to the id of the fighter. I am not sure technically speaking how to store multiple pieces of information within the same table under separate rows using PHP. For example, all athleteswill have a first name. The very basic theory of what i am trying to do is: If number_of_athletes 1, store F1FirstName in row 1, column 1 of Table "Athletes"; store F1LastName in row 1, column 2 of Table "Athletes"; store F2FirstName in row 2, column 1 of Table "Athletes"; store F2LastName in row 2, column 2 of table "Athletes"; Does this make sense? I know this question is very long and probably difficult so i appreciate the guidance.

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  • JavaScript Keycode 46 is DEL Function key or (.) period sign?

    - by Omar
    Im writing some logic in JavaScript using jquery, where i must check the input content against a REGEX pattern ex: "^[a-zA-Z0-9_]*$" //Alpha-numeric and _ The logic is almost done, i just have a little problem filtering the function key DEL, my logic goes like this: var FunctionsKey = new Array(8, 9, 13, 16, 35, 36, 37, 39, 46); function keypressValidation(key) { if (config.regexExp != null) { if ($.inArray(key, FunctionsKey) != -1) { return true; } else { var keyChar = String.fromCharCode(key); return RegexCheck(keyChar); } } return true; } If the KeyCode is one of those in the array, i let it pass, if not i get the char and compare it against the REGEX. The problem is: in some Browsers the DEL and '.' (period sign) have the same key Code 46. So is there a better logic to filter the function keys or must i write a condition for that case, maybe removing the 46 from the array and try to convert it to char and if is (.) let it go to the Regex function if not let it pass? The other question will be are there more shared Key Codes in some browsers? EDIT: My suggested solution wont work because it doesn't matter which key the user pressed (DEL or period) i always get (.) as CHAR at least on OPERA and FF =(.

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  • General question: Filesystem or database?

    - by poeschlorn
    Hey guys, i want to create a small document management system. there are several users who store their files. each file which is uploaded contains an info which user uploaded it and the document content itself. In a view there are displayed all files of ONE specific user, ordered by date. What would be better: 1) giving the documents a name or metadata(XML) which contain the date and user (and iterate through them to get the metadata) or 2) giving the files a random/unique name and store metadata in a DB? something like this: date | user | filename What would you say and why? The used programming language is java and the DB is MySQL.

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  • Storing HTML in MySQL using Java

    - by mpcabd
    Hello there again, So, I'm working on a project now where I should store webpages inside a database, I'm using crawler4j to crawl and Proxool along with MySQL Java Connector to connect to my database. When I tested the application I got: com.mysql.jdbc.MysqlDataTruncation: Data truncation: Data too long for column 'HTMLData'. The HTMLData column wasTEXT. When I changed the HTMLData column to LONGTEXT the error was gone, but I'm afraid it might get back in the future. Any idea on how to do that perfectly so I don't worry about that error (or any other similar error) in the future? Thanks :)

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  • How to debug KVO

    - by user8472
    In my program I use KVO manually to observe changes to values of object properties. I receive an EXC_BAD_ACCESS signal at the following line of code inside a custom setter: [self willChangeValueForKey:@"mykey"]; The weird thing is that this happens when a factory method calls the custom setter and there should not be any observers around. I do not know how to debug this situation. Update: The way to list all registered observers is observationInfo. It turned out that there was indeed an object listed that points to an invalid address. However, I have no idea at all how it got there. Update 2: Apparently, the same object and method callback can be registered several times for a given object - resulting in identical entries in the observed object's observationInfo. When removing the registration only one of these entries is removed. This behavior is a little counter-intuitive (and it certainly is a bug in my program to add multiple entries at all), but this does not explain how spurious observers can mysteriously show up in freshly allocated objects (unless there is some caching/reuse going on that I am unaware of). Modified question: How can I figure out WHERE and WHEN an object got registered as an observer? Update 3: Specific sample code. ContentObj is a class that has a dictionary as a property named mykey. It overrides: + (BOOL)automaticallyNotifiesObserversForKey:(NSString *)theKey { BOOL automatic = NO; if ([theKey isEqualToString:@"mykey"]) { automatic = NO; } else { automatic=[super automaticallyNotifiesObserversForKey:theKey]; } return automatic; } A couple of properties have getters and setters as follows: - (CGFloat)value { return [[[self mykey] objectForKey:@"value"] floatValue]; } - (void)setValue:(CGFloat)aValue { [self willChangeValueForKey:@"mykey"]; [[self mykey] setObject:[NSNumber numberWithFloat:aValue] forKey:@"value"]; [self didChangeValueForKey:@"mykey"]; } The container class has a property contents of class NSMutableArray which holds instances of class ContentObj. It has a couple of methods that manually handle registrations: + (BOOL)automaticallyNotifiesObserversForKey:(NSString *)theKey { BOOL automatic = NO; if ([theKey isEqualToString:@"contents"]) { automatic = NO; } else { automatic=[super automaticallyNotifiesObserversForKey:theKey]; } return automatic; } - (void)observeContent:(ContentObj *)cObj { [cObj addObserver:self forKeyPath:@"mykey" options:0 context:NULL]; } - (void)removeObserveContent:(ContentObj *)cObj { [cObj removeObserver:self forKeyPath:@"mykey"]; } - (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context { if (([keyPath isEqualToString:@"mykey"]) && ([object isKindOfClass:[ContentObj class]])) { [self willChangeValueForKey:@"contents"]; [self didChangeValueForKey:@"contents"]; } } There are several methods in the container class that modify contents. They look as follows: - (void)addContent:(ContentObj *)cObj { [self willChangeValueForKey:@"contents"]; [self observeDatum:cObj]; [[self contents] addObject:cObj]; [self didChangeValueForKey:@"contents"]; } And a couple of others that provide similar functionality to the array. They all work by adding/removing themselves as observers. Obviously, anything that results in multiple registrations is a bug and could sit somewhere hidden in these methods. My question targets strategies on how to debug this kind of situation. Alternatively, please feel free to provide an alternative strategy for implementing this kind of notification/observer pattern.

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  • Doctrine: How to traverse from an entity to another 'linked' entity?

    - by ropstah
    I'm loading 3 different tables using a cross-join in Doctrine_RawSql. This brings me back the following object: User -> User class (doctrine base class) Settings -> DoctrineCollection of Setting User_Settings -> DoctrineCollection of User_Setting The object above is the result of a many-to-many relationship between User and Setting where User_Setting acts as a reference table. User_Setting also contains another field named value. This obviously contains the value of the corresponding Setting. All good so far, however the Settings and User_Settings properties of the returned User object are in no way linked to each other (apart from the setting_id field ofcourse). Is there any direct way to traverse directly from the Settings property to the corresponding User_Settings property? This is the corresponding query: $sets = new Doctrine_RawSql(); $sets->select('{us.*}, {s.*}, {uset.*}') ->from('(User us CROSS JOIN Setting s) LEFT JOIN User_Setting uset ON us.user_id = uset.user_id AND s.setting_id = uset.setting_id') ->addComponent('us', 'User us') ->addComponent('uset', 'us.User_Setting uset') ->addComponent('s', 'us.Setting s') ->where('s.category_id = ? AND us.usr_auto_key = ?',array(1, 1)); $sets = $sets->execute();

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  • Allocation Target of std::aligned_storage (stack or heap?)

    - by Zenikoder
    I've been trying to get my head around the TR1 addition known as aligned_storage. Whilst reading the following documents N2165, N3190 and N2140 I can't for the life of me see a statement where it clearly describes stack or heap nature of the memory being used. I've had a look at the implementation provided by msvc2010, boost and gcc they all provide a stack based solution centered around the use of a union. In short: Is the memory type (stack or heap) used by aligned_storage implementation defined or is it always meant to be stack based? and, What the is the specific document that defines/determines that?

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  • MySQL - Find entries that refer to a specified index.

    - by Conor H
    Hi, So I have a booking system where I have a 'lesson_type' table with 'lesson_type_id' as PK. I have a constraint in place here so I can't delete a lesson_type if there are bookings made for that lesson_type. I would like to be able to determine if this lesson_type_id is being referred to by any entries in the bookings table (or any other table for that matter) so I can notify the user gracefully. i.e. not have a mysql error be thrown when they try and delete a record. What kind of query would I use for this? Thanks.

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