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• MVVM and avoiding Monolithic God object

  - by bufferz

  I am in the completion stage of a large project that has several large components: image acquisition, image processing, data storage, factory I/O (automation project) and several others. Each of these components is reasonably independent, but for the project to run as a whole I need at least one instance of each component. Each component also has a ViewModel and View (WPF) for monitoring status and changing things. My question is the safest, most efficient, and most maintainable method of instantiating all of these objects, subscribing one class to an Event in another, and having a common ViewModel and View for all of this. Would it best if I have a class called God that has a private instance of all of these objects? I've done this in the past and regretted it. Or would it be better if God relied on Singleton instances of these objects to get the ball rolling. Alternatively, should Program.cs (or wherever Main(...) is) instantiate all of these components, and pass them to God as parameters and then let Him (snicker) and His ViewModel deal with the particulars of running this projects. Any other suggestions I would love to hear. Thank you!

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• Firefox extension js object initialization

  - by Michael

  Note: this is about Firefox extension, not a js general question. In Firefox extension project I need my javascript object to be initialized just once per Firefox window. Otherwise each time I open my window a new timers will be engaged, new properties will be used, so everything will start from scratch. hope example below will demystify my question :) var StupidExtension { statusBarValue: "Not Initialized Yet", startup: function () { ... // Show statusBarValue in Status Bar Panel }, initTimerToRetrieveStatusBarValueFromNetwork: function () { ... } } so each time you hit Ctrl+N a new window you will see "Not Initialized Yet" and then new timer will be fired, so after some time it retrieve data from network you will see value also on second window and so on. Ideally would be to have just a single timer function running and updating all status bar panels in all Firefox windows. Of course I can do some caching, like saving the value in prefs or some other storage, then show it from there. But I feel like this is artificial. So the question will be is there "native" technique of making static some parts of the object among all Firefox window instances?

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• Fastest way to perform subset test operation on a large collection of sets with same domain

  - by niktech

  Assume we have trillions of sets stored somewhere. The domain for each of these sets is the same. It is also finite and discrete. So each set may be stored as a bit field (eg: 0000100111...) of a relatively short length (eg: 1024). That is, bit X in the bitfield indicates whether item X (of 1024 possible items) is included in the given set or not. Now, I want to devise a storage structure and an algorithm to efficiently answer the query: what sets in the data store have set Y as a subset. Set Y itself is not present in the data store and is specified at run time. Now the simplest way to solve this would be to AND the bitfield for set Y with bit fields of every set in the data store one by one, picking the ones whose AND result matches Y's bitfield. How can I speed this up? Is there a tree structure (index) or some smart algorithm that would allow me to perform this query without having to AND every stored set's bitfield? Are there databases that already support such operations on large collections of sets?

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• Heroku: Postgres type operator error after migrating DB from MySQL

  - by sevennineteen

  This is a follow-up to a question I'd asked earlier which phrased this as more of a programming problem than a database problem. http://stackoverflow.com/questions/2935985/postgres-error-with-sinatra-haml-datamapper-on-heroku I believe the problem has been isolated to the storage of the ID column in Heroku's Postgres database after running db:push. In short, my app runs properly on my original MySQL database, but throws Postgres errors on Heroku when executing any query on the ID column, which seems to have been stored in Postgres as TEXT even though it is stored as INT in MySQL. My question is why the ID column is being created as INT in Postgres on the data transfer to Heroku, and whether there's any way for me to prevent this. Here's the output from a heroku console session which demonstrates the issue: Ruby console for myapp.heroku.com >> Post.first.title => "Welcome to First!" >> Post.first.title.class => String >> Post.first.id => 1 >> Post.first.id.class => Fixnum >> Post[1] PostgresError: ERROR: operator does not exist: text = integer LINE 1: ...", "title", "created_at" FROM "posts" WHERE ("id" = 1) ORDER... ^ HINT: No operator matches the given name and argument type(s). You might need to add explicit type casts. Query: SELECT "id", "name", "email", "url", "title", "created_at" FROM "posts" WHERE ("id" = 1) ORDER BY "id" LIMIT 1 Thanks!

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• How to create a new ID for the new added node?

  - by marknt15

  Hi, I can normally get the ID of the default tree nodes but my problem is onCreate then jsTree will add a new node but it doesn't have an ID. My question is how can I add an ID to the newly created tree node? What I'm thinking to do is adding the ID HTML attribute to the newly created tree node but how? I need to get the ID of all of the nodes because it will serve as a reference for the node's respective div storage. HTML code: <div class="demo" id="demo_1"> <ul> <li id="phtml_1" class="file"><a href="#"><ins>&nbsp;</ins>Root node 1</a></li> <li id="phtml_2" class="file"><a href="#"><ins>&nbsp;</ins>Root node 2</a></li> </ul> </div> JS code: $("#demo_1").tree({ ui : { theme_name : "apple" }, callback : { onrename : function (NODE, TREE_OBJ) { alert(TREE_OBJ.get_text(NODE)); alert($(NODE).attr('id')); } } }); Cheers, Mark

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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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• Using Lucene to index private data, should I have a separate index for each user or a single index

  - by Nathan Bayles

  I am developing an Azure based website and I want to provide search capabilities using Lucene. (structured json objects would be indexed and stored in Lucene and other content such as Word documents, etc. would be indexed in lucene but stored in blob storage) I want the search to be secure, such that one user would never see a document belonging to another user. I want to allow ad-hoc searches as typed by the user. Lastly, I want to query programmatically to return predefined sets of data, such as "all notes for user X". I think I understand how to add properties to each document to achieve these 3 objectives. (I am listing them here so if anyone is kind enough to answer, they will have better idea of what I am trying to do) My questions revolve around performance and security. Can I improve document security by having a separate index for each user, or is including the user's ID as a parameter in each search sufficient? Can I improve indexing speed and total throughput of the system by having a separate index for each user? My thinking is that having separate indexes would allow me to scale the system by having multiple index writers (perhaps even on different server instances) working at the same time, each on their own index. Any insight would be greatly appreciated. Regards, Nate

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• Enforcing default time when only date in timestamptz provided

  - by Incognito

  Assume I have the table: postgres=# create table foo (datetimes timestamptz); CREATE TABLE postgres=# \d+ foo Table "public.foo" Column | Type | Modifiers | Storage | Description -----------+--------------------------+-----------+---------+------------- datetimes | timestamp with time zone | | plain | Has OIDs: no So lets insert some values into it... postgres=# insert into foo values ('2012-12-12'), --This is the value I want to catch for. (null), ('2012-12-12 12:12:12'), ('2012-12-12 12:12'); INSERT 0 4 And here's what we have: postgres=# select * from foo ; datetimes ------------------------ 2012-12-12 00:00:00+00 2012-12-12 12:12:12+00 2012-12-12 12:12:00+00 (4 rows) Ideally, I'd like to set up a default time-stamp value when a TIME is not provided with the input, rather than the de-facto time of 2012-12-12 being 00:00:00, I would like to set a default of 15:45:10. Meaning, my results should look like: postgres=# select * from foo ; datetimes ------------------------ 2012-12-12 15:45:10+00 --This one gets the default time. 2012-12-12 12:12:12+00 2012-12-12 12:12:00+00 (4 rows) I'm not really sure how to do this in postgres 8.4, I can't find anything in the datetime section of the manual or the sections regarding column default values.

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• Making two Windows using CreateWindowsEx()

  - by Jamie Keeling

  Hello, I have a windows form that has a simple menu and performs a simple operation, I want to be able to create another windows form with all the functionality of a menu bar, message pump etc.. as a separate thread so I can then share the results of the operation to the second window. I.E. 1) Form A opens Form B opens as a separate thread 2)Form A performs operation 3)Form A passes results via memory to Form B 4)Form B display results I'm confused as to how to go about it, the main app runs fine but i'm not sure how to add a second window if the first one already exists. I think that using CreateWindow will allow me to make another window but again i'm not sure how to access the message pump so I can respond to certain events like WM_CREATE on the second window. I hope it makes sense. Thanks! Edit: I've attempted to make a second window and although this does compile, no windows show atall on build. ////////////////////// // WINDOWS FUNCTION // ////////////////////// LRESULT CALLBACK WindowFunc(HWND hMainWindow, UINT message, WPARAM wParam, LPARAM lParam) { //Fields WCHAR buffer[256]; struct DiceData storage; HWND hwnd; // Act on current message switch(message) { case WM_CREATE: AddMenus(hMainWindow); hwnd = CreateWindowEx( 0, "ChildWClass", (LPCTSTR) NULL, WS_CHILD | WS_BORDER | WS_VISIBLE, 0, 0, 0, 0, hMainWindow, NULL, NULL, NULL); ShowWindow(hwnd, SW_SHOW); break; Any suggestions as to why this happens?

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• How to optimize a postgreSQL server for a "write once, read many"-type infrastructure ?

  - by mhu

  Greetings, I am working on a piece of software that logs entries (and related tagging) in a PostgreSQL database for storage and retrieval. We never update any data once it has been inserted; we might remove it when the entry gets too old, but this is done at most once a day. Stored entries can be retrieved by users. The insertion of new entries can happen rather fast and regularly, thus the database will commonly hold several millions elements. The tables used are pretty simple : one table for ids, raw content and insertion date; and one table storing tags and their values associated to an id. User search mostly concern tags values, so SELECTs usually consist of JOIN queries on ids on the two tables. To sum it up : 2 tables Lots of INSERT no UPDATE some DELETE, once a day at most some user-generated SELECT with JOIN huge data set What would an optimal server configuration (software and hardware, I assume for example that RAID10 could help) be for my PostgreSQL server, given these requirements ? By optimal, I mean one that allows SELECT queries taking a reasonably little amount of time. I can provide more information about the current setup (like tables, indexes ...) if needed.

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• Database contents setting themselves to 0

  - by Luis Armando

  I have a Database that contains 4 tables, however I'm using 1 of them which is separated from the others. In this table I have 4 fields which are varchar and the rest are ints (11 other fields), when the users fill up the DB everything gets saved correctly, however it has happened 3 times so far that the database values for the int's reset to 0 without any apparent reason. At first, I thought, it was because those fields (where the numbers should go) were varchars not ints. However since I changed it, it happened again. I've already double checked my code and I have nothing that even updates or inserts a 0 value. Also I'm using codeigniter and active records which protect against SQL injections AND have XSS filtering enabled, could anyone point out something I might be missing or a reason for this to be happening? Also, I'm pretty sure about the answer of this but, is there ANY way to recover some data?? Other than having to ask everyone to fill in everything again.. =/ ** EDIT ** The Storage Engine is MyISAM and Collation is latin1_swedish_ci, Pack Keys are default, for all intents and purposes it's a normal DB

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• Multithreaded linked list traversal

  - by Rob Bryce

  Given a (doubly) linked list of objects (C++), I have an operation that I would like multithread, to perform on each object. The cost of the operation is not uniform for each object. The linked list is the preferred storage for this set of objects for a variety of reasons. The 1st element in each object is the pointer to the next object; the 2nd element is the previous object in the list. I have solved the problem by building an array of nodes, and applying OpenMP. This gave decent performance. I then switched to my own threading routines (based off Windows primitives) and by using InterlockedIncrement() (acting on the index into the array), I can achieve higher overall CPU utilization and faster through-put. Essentially, the threads work by "leap-frog'ing" along the elements. My next approach to optimization is to try to eliminate creating/reusing the array of elements in my linked list. However, I'd like to continue with this "leap-frog" approach and somehow use some nonexistent routine that could be called "InterlockedCompareDereference" - to atomically compare against NULL (end of list) and conditionally dereference & store, returning the dereferenced value. I don't think InterlockedCompareExchangePointer() will work since I cannot atomically dereference the pointer and call this Interlocked() method. I've done some reading and others are suggesting critical sections or spin-locks. Critical sections seem heavy-weight here. I'm tempted to try spin-locks but I thought I'd first pose the question here and ask what other people are doing. I'm not convinced that the InterlockedCompareExchangePointer() method itself could be used like a spin-lock. Then one also has to consider acquire/release/fence semantics... Ideas? Thanks!

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• PDO closeCursor Error

  - by Metropolis

  Hey Everyone, I currently have a database layer that I wrote myself and I have been using it now for over a year without any problems. The database class uses PDO, and there are two different databases that I regularly connect to (MySQL and MS SQL). The MS SQL database is used for Accpac accounting storage, and the MySQL database is used for everything else. In one of the MySQL databases I have all of the dsn's listed which I use to create the string I need to connect to the MS SQL databases. I have a new program I am trying to write which I am taking employee data from one of the MySQL databases, and using the employee ID to get the employee's information from the MS SQL database. For some reason, whenever I run the program it will get through about 1200 records (out of 11k) and then crash with an error like the following, Fatal error: Call to a member function closeCursor() on a non-object I have tried moving the loops around in many different ways, and I have tried manually closing the connections by setting the database handle to null. Nothing I do seems to work. Thanks for any help! Metropolis

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• typedef a functions prototype

  - by bitmask

  I have a series of functions with the same prototype, say int func1(int a, int b) { // ... } int func2(int a, int b) { // ... } // ... Now, I want to simplify their definition and declaration. Of course I could use a macro like that: #define SP_FUNC(name) int name(int a, int b) But I'd like to keep it in C, so I tried to use the storage specifier typedef for this: typedef int SpFunc(int a, int b); This seems to work fine for the declaration: SpFunc func1; // compiles but not for the definition: SpFunc func1 { // ... } which gives me the following error: error: expected '=', ',', ';', 'asm' or '__attribute__' before '{' token Is there a way to do this correctly or is it impossible? To my understanding of C this should work, but it doesn't. Why? Note, gcc understands what I am trying to do, because, if I write SpFunc func1 = { /* ... */ } it tells me error: function 'func1' is initialized like a variable Which means that gcc understands that SpFunc is a function type.

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• Generating authentication header from azure table through objective-c

  - by user923370

  I'm fetching data from iCloud and for that I need to generate a header (azure table storage). I used the code below for that and it is generating the headers. But when I use these headers in my project it is showing "make sure that the value of authorization header is formed correctly including the signature." I googled a lot and tried many codes but in vain. Can anyone kindly please help me with where I'm going wrong in this code. -(id)generat{ NSString *messageToSign = [NSString stringWithFormat:@"%@/%@/%@", dateString,AZURE_ACCOUNT_NAME, tableName]; NSString *key = @"asasasasasasasasasasasasasasasasasasasasas=="; const char *cKey = [key cStringUsingEncoding:NSUTF8StringEncoding]; const char *cData = [messageToSign cStringUsingEncoding:NSUTF8StringEncoding]; unsigned char cHMAC[CC_SHA256_DIGEST_LENGTH]; CCHmac(kCCHmacAlgSHA256, cKey, strlen(cKey), cData, strlen(cData), cHMAC); NSData *HMAC = [[NSData alloc] initWithBytes:cHMAC length:sizeof(cHMAC)]; NSString *hash = [Base64 encode:HMAC]; NSLog(@"Encoded hash: %@", hash); NSURL *url=[NSURL URLWithString: @"http://my url"]; NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url]; [request addValue:[NSString stringWithFormat:@"SharedKeyLite %@:%@",AZURE_ACCOUNT_NAME, hash] forHTTPHeaderField:@"Authorization"]; [request addValue:dateString forHTTPHeaderField:@"x-ms-date"]; [request addValue:@"application/atom+xml, application/xml"forHTTPHeaderField:@"Accept"]; [request addValue:@"UTF-8" forHTTPHeaderField:@"Accept-Charset"]; NSLog(@"Headers: %@", [request allHTTPHeaderFields]); NSLog(@"URL: %@", [[request URL] absoluteString]); return request; } -(NSString*)rfc1123String:(NSDate *)date { static NSDateFormatter *df = nil; if(df == nil) { df = [[NSDateFormatter alloc] init]; df.locale = [[[NSLocale alloc] initWithLocaleIdentifier:@"en_US"] autorelease]; df.timeZone = [NSTimeZone timeZoneWithAbbreviation:@"GMT"]; df.dateFormat = @"EEE',' dd MMM yyyy HH':'mm':'ss 'GMT'"; } return [df stringFromDate:date]; }

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• How much does an InnoDB table benefit from having fixed-length rows?

  - by Philip Eve

  I know that dependent on the database storage engine in use, a performance benefit can be found if all of the rows in the table can be guaranteed to be the same length (by avoiding nullable columns and not using any VARCHAR, TEXT or BLOB columns). I'm not clear on how far this applies to InnoDB, with its funny table arrangements. Let's give an example: I have the following table CREATE TABLE `PlayerGameRcd` ( `User` SMALLINT UNSIGNED NOT NULL, `Game` MEDIUMINT UNSIGNED NOT NULL, `GameResult` ENUM('Quit', 'Kicked by Vote', 'Kicked by Admin', 'Kicked by System', 'Finished 5th', 'Finished 4th', 'Finished 3rd', 'Finished 2nd', 'Finished 1st', 'Game Aborted', 'Playing', 'Hide' ) NOT NULL DEFAULT 'Playing', `Inherited` TINYINT NOT NULL, `GameCounts` TINYINT NOT NULL, `Colour` TINYINT UNSIGNED NOT NULL, `Score` SMALLINT UNSIGNED NOT NULL DEFAULT 0, `NumLongTurns` TINYINT UNSIGNED NOT NULL DEFAULT 0, `Notes` MEDIUMTEXT, `CurrentOccupant` TINYINT UNSIGNED NOT NULL DEFAULT 0, PRIMARY KEY (`Game`, `User`), UNIQUE KEY `PGR_multi_uk` (`Game`, `CurrentOccupant`, `Colour`), INDEX `Stats_ind_PGR` (`GameCounts`, `GameResult`, `Score`, `User`), INDEX `GameList_ind_PGR` (`User`, `CurrentOccupant`, `Game`, `Colour`), CONSTRAINT `Constr_PlayerGameRcd_User_fk` FOREIGN KEY `User_fk` (`User`) REFERENCES `User` (`UserID`) ON DELETE CASCADE ON UPDATE CASCADE, CONSTRAINT `Constr_PlayerGameRcd_Game_fk` FOREIGN KEY `Game_fk` (`Game`) REFERENCES `Game` (`GameID`) ON DELETE CASCADE ON UPDATE CASCADE ) ENGINE=INNODB CHARACTER SET utf8 COLLATE utf8_general_ci The only column that is nullable is Notes, which is MEDIUMTEXT. This table presently has 33097 rows (which I appreciate is small as yet). Of these rows, only 61 have values in Notes. How much of an improvement might I see from, say, adding a new table to store the Notes column in and performing LEFT JOINs when necessary?

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• XUL: Printing value from SQL query without using value attribute

  - by Grip

  I want to print the results of an SQL query in XUL with word-wrapping using the description tag. I have the following code: <grid> <columns> <column flex="2" /> <column flex="1" /> </columns> <rows datasources="chrome://glossary/content/db/development.sqlite3" ref="?" querytype="storage" > <template> <query>select distinct * from Terms</query> <action> <row uri="?"> <description value="?name" /> <description value="?desc" /> </row> </action> </template> </rows> This works for printing the data, but since I'm using the value attribute of description, there's no word-wrapping. I don't understand entirely what I'm doing with the value attribute, but I don't seem to be able to get the values of my SQL query in any other way. So, how could I get those values without the value tag? Thanks.

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• Catch a PHP Object Instantiation Error

  - by Rob Wilkerson

  It's really irking me that PHP considers the failure to instantiate an object a Fatal Error (which can't be caught) for the application as a whole. I have set of classes that aren't strictly necessary for my application to function--they're really a convenience. I have a factory object that attempts to instantiate the class variant that's indicated in a config file. This mechanism is being deployed for message storage and will support multiple store types: DatabaseMessageStore FileMessageStore MemcachedMessageStore etc. A MessageStoreFactory class will read the application's preference from a config file, instantiate and return an instance of the appropriate class. It might be easy enough to slap a conditional around the instantiation to ensure that class_exists(), but MemcachedMessageStore extends PHP's Memcached class. As a result, the class_exists() test will succeed--though instantiation will fail--if the memcached bindings for PHP aren't installed. Is there any other way to test whether a class can be instantiated properly? If it can't, all I need to do is tell the user which features won't be available to them, but let them continue one with the application. Thanks.

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• Error handling approach on PHP

  - by Industrial

  Hi everybody, We have a web server that we're about to launch a number of applications onto. They will all share database and memcached servers, but each application has it's own mySQL database and all memcached keys per application, is prefixed. Possible scenario: If a memcached server in our cluster goes boom, we want someone (operative system admin) to be automatically contacted by email/iphone push notification or in any other appropriate way. If we we're about to install 150 identical applications for our customers on our servers, and a memcached server dies - all 150 applications will individually find this out and contact our system admin, which most certainly is going to think about getting a new job where he or she isn't about to be woken up by getting 150 messages sent 4:15 in the morning. Possible solution: One idea is to set up an external server for error handling that gets a $_POST or cURL request sent, and handles storage of the error message depending on the seriousness of the actual error message. It would of course check upon receiving the error call, that if the same memcached server have already been reported as offline, there would be no need to spam the system admin with additional reminders... The questions: What's a good approach on how to handle errors? How does the big guys in the industry handle this? Thanks!

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• Omit Properties from WebControl Serialization

  - by Laramie

  I have to serialize several objects inheriting from WebControl for database storage. These include several unecessary (to me) properties that I would prefer to omit from serialization. For example BackColor, BorderColor, etc. Here is an example of an XML serialization of one of my controls inheriting from WebControl. <Control xsi:type="SerializePanel"> <ID>grCont</ID> <Controls /> <BackColor /> <BorderColor /> <BorderWidth /> <CssClass>grActVid bwText</CssClass> <ForeColor /> <Height /> <Width /> ... </Control> I have been trying to create a common base class for my controls that inherits from WebControl and uses the "xxxSpecified" trick to selectively choose not to serialize certain properties. For example to ignore an empty BorderColor property, I'd expect [XmlIgnore] public bool BorderColorSpecified() { return !base.BorderColor.IsEmpty; } to work, but it's never called during serialization. I've also tried it in the class to be serialized as well as the base class. Since the classes themselves might change, I'd prefer not to have to create a custom serializer. Any ideas?

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• "date_part('epoch', now() at time zone 'UTC')" not the same time as "now() at time zone 'UTC'" in po

  - by sirlark

  I'm writing a web based front end to a database (PHP/Postgresql) in which I need to store various dates/times. The times are meant to be always be entered on the client side in the local time, and displayed in the local time too. For storage purposes, I store all dates/times as integers (UNIX timestamps) and normalised to UTC. One particular field has a restriction that the timestamp filled in is not allowed to be in the future, so I tried this with a database constraint... CONSTRAINT not_future CHECK (timestamp-300 <= date_part('epoch', now() at time zone 'UTC')) The -300 is to give 5 minutes leeway in case of slightly desynchronised times between browser and server. The problem is, this constraint always fails when submitting the current time. I've done testing, and found the following. In PostgreSQL client: SELECT now() -- returns correct local time SELECT date_part('epoch', now()) -- returns a unix timestamp at UTC (tested by feeding the value into the date function in PHP correcting for its compensation to my time zone) SELECT date_part('epoch', now() at time zone 'UTC') -- returns a unix timestamp at two time zone offsets west, e.g. I am at GMT+2, I get a GMT-2 timestamp. I've figured out obviously that dropping the "at time zone 'UTC'" will solve my problem, but my question is if 'epoch' is meant to return a unix timestamp which AFAIK is always meant to be in UTC, why would the 'epoch' of a time already in UTC be corrected? Is this a bug, or I am I missing something about the defined/normal behaviour here.

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• Scalability 101: How can I design a scalable web application using PHP?

  - by Legend

  I am building a web-application and have a couple of quick questions. From what I learnt, one should not worry about scalability when initially building the app and should only start worrying when the traffic increases. However, this being my first web-application, I am not quite sure if I should take an approach where I design things in an ad-hoc manner and later "fix" them. I have been reading stories about how people start off with an app that gets millions of users in a week or two. Not that I will face the same situation but I can't help but wonder, how do these people do it? Currently, I bought a shared hosting account on Lunarpages and that got me started in building and testing the application. However, I am interested in learning how to build the same application in a scalable-manner using the cloud, for instance, Amazon's EC2. From my understanding, I can see a couple of components: There is a load balancer that first receives requests and then decides where to route each request This request is then handled by a server replica that then processes the request and updates (if required) the database and sends back the response to the client If a similar request comes in, then a caching mechanism like memcached kicks into picture and returns objects from the cache A blackbox that handles database replication Specifically, I am trying to do the following: Setting up a load balancer (my homework revealed that HAProxy is one such load balancer) Setting up replication so that databases can be synchronized Using memcached Configuring Apache to work with multiple web servers Partitioning application to use Amazon EC2 and Amazon S3 (my application is something that will need great deal of storage) Finally, how can I avoid burning myself when using Amazon services? Because this is just a learning phase, I can probably do with 2-3 servers with a simple load balancer and replication but until I want to avoid paying loads of money accidentally. I am able to find resources on individual topics but am unable to find something that starts off from the big picture. Can someone please help me get started?

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• J2EE and alternatives

  - by Ilya K

  Hello, I am J2SE developer but I have rich web-background (php, perl/cgi and so on) and now I am starting new project. It will have web interface, spaghetti business logic, relational database as storage and connections to other services. I do it from the scratch. My colleagues told me to use spring, spring security and struts. I look briefly at J2EE spec and found that it covers almost all aspects of enterprise application. I asked my colleagues why do they need spring and struts, but looks like they use technologies simply because they are familiar with them and not familiar with classic J2EE stack. So, my question is: what is bad about J2EE? Why do I need spring if there are JNDI lookups? It will take a day or two to create fake InitialContext for unit-tests. And that is all: I stand with out of external tools like spring. Why do I need spring-security if there is a security built in Servlets spec? I can map any request to any servlet using web.xml, no struts.xml is needed. I can use servlet-filters instead of struts interceptors. There is RMI, so I do not need spring-remote. And so on.. Why should I bother my self with all that fancy stuff if there is J2EE? I really want to find situation when J2EE is not enough. Do you have any? Thanks!

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• Need help/suggestions for creating fantasy sports scoring databases and queries

  - by MGumbel

  I'm trying to create a website for my friends and I to keep track of fantasy sports scoring. So far, I've been doing the calculations and storage in Excel, which is very tedious. I'm trying to make it more simplified and automated through a SQL database that I can then wrap a web app around to enter daily stat updates. It's premised on our participation in another commercial site where we trade virtual shares of athletes, and thus acquire an "ownership percentage" in each athlete. For instance, if there are 100 shares of AROD, and I own 10 shares, then I own 10%. It then applies this to traditional baseball rotisserie scoring. So, for instance, if AROD has 1 HR today, then his adjusted HR stat would be 1.10. If he also has 2 RBI's, then his adjusted RBI stat today would be 2.20, based on (2 x 1.10)(1 to normalize the stat, and the .10 to represent the ownership percentage). All the stats for my team would then be summed each day and added to my stat history to come to an aggregated total. After that, points are allocated based on the ranking of each participant in each category at the end of the day. E.g. if there are 10 participants, and I have the highest total aggregate number of Adjusted HR's, then I get 10 pts. The points are then summed across the different stat categories to come up with a total point ranking for that day. An added difficulty is that ownership %'s can change on a daily basis. So far, in playing around with different schema, I don't know that having a separate table for each athlete's stats and each player's ownership %'s is the wisest choice. It seems to me that simply having two tables, one that contains the daily stat information for each athlete, and another that shows the ownership % of each player. My friend suggested using a start and end date for each ownership % to represent the potential daily changes in this category. I'm admittedly new to database development, so any suggestions on query code would be appreciated.

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• Drupal 6 Validation for Form Callback Function

  - by Wade

  I have a simple form with a select menu on the node display page. Is there an easy way to validate the form in my callback function? By validation I don't mean anything advanced, just to check that the values actually existed in the form array. For example, without ajax, if my select menu has 3 items and I add a 4th item and try to submit the form, drupal will give an error saying something similar to "an illegal choice was made, please contact the admin." With ajax this 4th item you created would get saved into the database. So do I have to write validation like if ($select_item > 0 && $select_item <= 3) { //insert into db } Or is there an easier way that will check that the item actually existed in the form array? I'm hoping there is since without ajax, drupal will not submit the form if it was manipulated. Thanks. EDIT: So I basically need this in my callback function? $form_state = array('storage' => NULL, 'submitted' => FALSE); $form_build_id = $_POST['form_build_id']; $form = form_get_cache($form_build_id, $form_state); $args = $form['#parameters']; $form_id = array_shift($args); $form_state['post'] = $form['#post'] = $_POST; $form['#programmed'] = $form['#redirect'] = FALSE; drupal_process_form($form_id, $form, $form_state); To get $_POST['form_build_id'], I sent it as a data param, is that right? Where I use form_get_cache, looks like there is no data. Kind of lost now.

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