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• Why isn't UTF-8 allowed as the "ANSI" code page?

  - by dan04

  The Windows _setmbcp function allows any valid code page... (except UTF-7 and UTF-8, which are not supported) OK, not supporting UTF-7 makes sense: Characters have non-unique representations and that introduces complexity and security risks. But why not UTF-8? As I understand it, the "ANSI" versions of the Windows API functions convert their arguments to UTF-16, call the equivalent "W" function, and convert any strings in the output to "ANSI". This is what I've been doing manually. So why can't Windows do it for me?

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• Detecting if a browser is using Private Browsing mode

  - by Steve

  I'm building an extranet for a company paranoid about security. They want to make sure that (among other things) their users are browsing the site with the Private Browsing mode switched on in their web browser so that no cookies or history is kept. I found only this http://jeremiahgrossman.blogspot.com/2009/03/detecting-private-browsing-mode.html and http://serverfault.com/questions/18966/force-safari-to-operate-in-private-mode-and-detect-that-state-from-a-webserver The ideal solution would use no or minimal javascript. Would attempting to set a unique cookie work for all browsers and platforms? Anyone done this before? thanks!

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• Django: Determining if a user has voted or not

  - by TheLizardKing

  I have a long list of links that I spit out using the below code, total votes, submitted by, the usual stuff but I am not 100% on how to determine if the currently logged in user has voted on a link or not. I know how to do this from within my view but do I need to alter my below view code or can I make use of the way templates work to determine it? I have read http://stackoverflow.com/questions/1528583/django-vote-up-down-method but I don't quite understand what's going on ( and don't need any ofjavascriptery). Models (snippet): class Link(models.Model): category = models.ForeignKey(Category, blank=False, default=1) user = models.ForeignKey(User) created = models.DateTimeField(auto_now_add=True) modified = models.DateTimeField(auto_now=True) url = models.URLField(max_length=1024, unique=True, verify_exists=True) name = models.CharField(max_length=512) def __unicode__(self): return u'%s (%s)' % (self.name, self.url) class Vote(models.Model): link = models.ForeignKey(Link) user = models.ForeignKey(User) created = models.DateTimeField(auto_now_add=True) def __unicode__(self): return u'%s vote for %s' % (self.user, self.link) Views (snippet): links = Link.objects.select_related().annotate(votes=Count('vote')).order_by('-created')

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• Are concurrency issues possible when using the WCF Service Behavoir attribute set to ConcurrencyMode

  - by Brandon Linton

  We have a WCF service that makes a good deal of transactional NHibernate calls. Occasionally we were seeing SQL timeouts, even though the calls were updating different rows and the tables were set to row level locking. After digging into the logs, it looks like different threads were entering the same point in the code (our transaction using block), and an update was hanging on commit. It didn't make sense, though, because we believed that the following service class attribute was forcing a unique execution thread per service call: [ServiceBehavior(ConcurrencyMode = ConcurrencyMode.Multiple, InstanceContextMode = InstanceContextMode.PerCall)] We recently changed the concurrency mode to ConcurrencyMode.Single and haven't yet run into any issues, but the bug was very difficult to reproduce (if anyone has any thoughts on flushing a bug like that out, let me know!). Anyway, that all brings me to my question: shouldn't an InstanceContextMode of PerCall enforce thread-safety within the service, even if the ConcurrencyMode is set to multiple? How would it be possible for two calls to be serviced by the same service instance? Thanks!

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• How to generate a good random seed to pass to srand()?

  - by zr

  Hi, I am writing a C++ program which needs to create a temporary file for its internal usage. I would like to allow concurrent executions of the program by running multiple proccesses, so the temporary file name needs to be randomized, that way each spawned process will generate a unique temporary file name for its own use. I am using rand() to generate random characters for part of the file name, so i need to initialize the random number generator's seed using srand(). What options are there for passing a good argument to srand() such that two processes will not be initialized with the same seed value? My code needs to work both on Windows and pn Linux TIA.

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• Selecting an element based on class and id in jquery - similar to an SQL query

  - by Ankur

  I want to select an element based on it's class and id, I have seen many similar questions on SO. Most of the users ask why would you ever want to do this - which is not very helpful, trust me, this is the simplest way of solving my UI problem, and it's a very unique and intereting UI related to making generic triple stores easily browsable. At the moment the jQUery looks like this: $(document).ready( function() { $(".predicates").hide(); $(".objects").hide(); $("#subject").click( function() { $("#predId, .predicates").toggle(); // this line } ); $("#predId").click( function() { $("#objId, .objects").toggle(); } ); }); The line I am really interested in is this $("#predId, .predicates").toggle(); how do I get the select to ensure that both #predId and .predicates are true, at the moment it seems that only one or the other has to be true. Is there something like an && operator?

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• Rails Model multiple column uniqueness

  - by Jty.tan

  I am making a Viewer model with belongs_to :users belongs_to :orders that joins the models Users and Orders with a :has_many :through => :viewers. And the Viewer model has the attributes of user_id and order_id. How would I set it up so that new viewers are only accepted if both user_id and order_id are unique in the same row? I remember in MySQL being able to do so with a flag (although I can't for the life of me remember what it was), but I'm not sure how to do it with Rails. Can I do something like (for Viewer.rb) validates_uniqueness_of :user_id, :scope => :order_id?

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• Why won't this SQL CAST work?

  - by Kev

  I have a nvarchar(50) column in a SQL Server 2000 table defined as follows: TaskID nvarchar(50) NULL I need to fill this column with some random SQL Unique Identifiers (I am unable to change the column type to uniqueidentifier). I tried this: UPDATE TaskData SET TaskID = CAST(NEWID() AS nvarchar) but I got the following error: Msg 8115, Level 16, State 2, Line 1 Arithmetic overflow error converting expression to data type nvarchar. I also tried: UPDATE TaskData SET TaskID = CAST(NEWID() AS nvarchar(50)) but then got this error: Msg 8152, Level 16, State 6, Line 1 String or binary data would be truncated. I don't understand why this doesn't work but this does: DECLARE @TaskID nvarchar(50) SET @TaskID = CAST(NEW() AS nvarchar(50)) I also tried CONVERT(nvarchar, NEWID()) and CONVERT(nvarchar(50), NEWID()) but got the same errors.

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• Storing uploaded content on a website

  - by Matt

  For the past 5 years, my typical solution for storing uploaded files (images, videos, documents, etc) was to throw everything into an "upload" folder and give it a unique name. I'm looking to refine my methods for storing uploaded content and I'm just wondering what other methods are used / preferred. I've considered storing each item in their own folder (folder name is the Id in the db) so I can preserve the uploaded file name. I've also considered uploading all media to a locked folder, then using a file handler, which you pass the Id of the file you want to download in the querystring, it would then read the file and send the bytes to the user. This is handy for checking access, and restricting bandwidth for users.

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• Oracle - Is there any effects of not having a primary key on a table ?

  - by Sathya

  We use sequence numbers for primary keys on the tables. There are some tables where we dont really use the primary key for any querying purpose. But, we have Indexes on other columns. These are non-unique indexes. The queries use these non-primary key columns in the WHERE conditions. So, I dont really see any benefit of having a primary key on such tables. My experience with SQL 2000 was that, it used to replicate tables which had some primary key. Otherwise it would not. I am using Oracle 10gR2. I would like to know if there are any such side-effects of having tables that dont have primary key.

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• Advice on e-commerce logging strategy

  - by yalestar

  I recently inherited an e-commerce app (Java/Struts) that I'm porting to Rails. The thing is, we frequently have to do forensics on orders by poring through the log files, and with the old app's logs (log4j wall of text) it's pretty hard to make sense of the individual orders when several people are placing orders simultaneously. So I'm soliciting advice on a good strategy for logging of these orders, like maybe logging each individual order to its own MongoDB collection based on unique cart ID? Or maybe group them by IP address? Something different entirely? Essentially, what is the best approach for logging of an online store so that it's easy to backtrace each user's interaction with the site?

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• Pageview implementation

  - by The Elite Gentleman

  Hi everyone I want to add a pageview feature on my current web application. This page view is based on the count of user viewing the page. It must be unique, i.e. I must not view a person's page 10000 times and record it as 10000 views, just record 1 view instead. My question is, should I base my pageview count on IP address? If not, what is/are the best approach in doing this? I know that if the person has logged in to my system, I can simply use the user id stored in the session and check on the record if the user has/hasn't viewed the page and update accordingly. But for "anonymous" viewers, what is the best approach? Thanks. PS How does Youtube does it?

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• InvalidOperationException When XML Serializing Inherited Class

  - by Nick

  I am having an issue serializing a c# class to an XML file that has a base class... here is a simple example: namespace Domain { [Serializable] public class ClassA { public virtual int MyProperty { get; set; } } } namespace Derived { public class ClassA : Domain.ClassA { public override int MyProperty { get { return 1; } set { /* Do Nothing */ } } } } When I attempt to serialize an instance of Derived.ClassA, I receive the following exception: InvalidOperationException(Types 'Domain.ClassA' and 'Derived.ClassA' both use the XML type name 'ClassA', from the namespace ". Use XML attributes to specify a unique XML name and/or namespace for the type.) The problem is that I want to create a single base class that simply defines the structure of the XML file, and then allow anyone else to derive from that class to insert business rules, but that the formatting will come through from the base. Is this possible, and if so, how do I attribute the base class to allow this?

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• rails: date type and GetDate

  - by cbrulak

  This is a follow up to this question: http://stackoverflow.com/questions/2930256/unique-responses-rails-gem I'm going to create an index based on the user id, url and a date type. I want date type (not datetime type) because I want the day, the 24 hour day to be part of the index to avoid duplication of page views counts on the same day. In other words: A view only counts once in a day by a visitor. I also want the default value of that column (viewdate) to be the function GETDATE(). This is what I have in my migration: execute "ALTER TABLEpage_viewsADD COLUMN viewdate datetime DEFAULTGETDATE()`" But the value viewdate is always empty. What am I missing? (as an aside, any other suggestions for accomplishing this goal?)

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• Why is this postgres function failing only on one specifc database?

  - by Ollie Edwards

  I'm trying to fix an issue with a legacy database. The quote_literal function is not working for a specific database on an 8.4 install of postgres. Here's my results on a fresh test database: select quote_literal(42); quote_literal --------------- '42' (1 row) And now the same on the target db select quote_literal(42); ERROR: function quote_literal(integer) is not unique LINE 1: select quote_literal(42); ^ HINT: Could not choose a best candidate function. You might need to add explicit type casts. AIUI, the quote_literal(anyvalue) function should handle integer values ok, and this seems to be upheld by the first test. So I figured the quote_literal function must have been overridden in this db but no this doesn't seem to be the case. I could override it with a specific quote_literal(integer) function but I don't see why I should have to. The question is what is could be causing the failure of this function in this specific database whilst not affecting the fresh db?

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• Identifying CDs

  - by Chris

  I'd like to be able to determine what music album CD is in a CD drive. For example, if someone claims that the CD in their drive is Eminem - The Eminem Show, I would like to be able to verify that the CD is indeed The Eminem Show. Any ideas? I've applied for a Gracenote developer license, but they won't get back to me for five days. Also, how does this work? Is there some GUID or other unique identifier that music discs are encoded with? Lastly, might this be possible with data CDs, like, say, the Diablo II install Disc 1? If so, any directions you can point me in, for accomplishing this?

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• CouchDB Map/Reduce raises execption in reduce function?

  - by fuzzy lollipop

  my view generates keys in this format ["job_id:1234567890", 1271430291000] where the first key element is a unique key and the second is a timestamp in milliseconds. I run my view with this elapsed_time?startkey=["123"]&endkey=["123",{}]&group=true&group_level=1 and here is my reduce function, the intention is to reduce the output to get the earliest and latest timestamps and return the difference between them and now function(keys,values,rereduce) { var now = new Date().valueOf(); var first = Number.MIN_VALUE; var last = Number.MAX_VALUE; if (rereduce) { first = Math.max(first,values[0].first); last = Math.min(last,values[0].last); } else { first = keys[0][0][1]; last = keys[keys.length-1][0][1]; } return {first:now - first, last:now - last}; } and when processing a query it constantly raises the following execption: function raised exception (new TypeError("keys has no properties", "", 1)) I am making sure not to reference keys inside my rereduce block. Why does this function constantly raise this exception?

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• How do people manage changes to common library files stored across mutiple (Mercurial) repositories?

  - by mckoss

  This is perhaps not a question unique to Mercurial, but that's the SCM that I've been using most lately. I work on multiple projects and tend to copy source code for libraries or utilities from a previous project to get a leg up on starting a new project. The problem comes in when I want to merge all the changes I made in my latest project, back into a "master" copy of those shared library files. Since the files stored in disjoint repositories will have distinct version histories, Mercurial won't be able to perform an intelligent merge if I just copy the files back to the master repo (or even between two independent projects). I'm looking for an easy way to preserve the change history so I can merge library files back to the master with a minimum of external record keeping (which is one of the reasons I'm using SVN less as merges require remembering when copies were made across branches). Perhaps I need to do a bit more up-front organization of my repository to prepare for a future merge back to a common master.

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• mod,prime -> inverse possible

  - by Piet

  Hi all. I was wondering if one can do the following: We have: X is a product of N-primes, thus I assume unique. C is a constant. We can assure that C is a number that is part of the N-primes or not. Whichever will work best. Thus: X mod C = Z We have Z and C and we know that X was a product of N-primes, where N is restricted lets say first 100 primes. Is there anyway we can get back X?

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• Concatenating databases with Squeryl

  - by Pengin

  I'm trying to use Squeryl to take the contents of a table from one database, and append it to the equivalent table in another database. The primary key will have to be reassigned in the process, but I'm getting the error NULL not allowed for column "SIMID". Why is this? object Concatenator { def main(args: Array[String]) { Class.forName("org.h2.Driver"); val seshA = Session.create( java.sql.DriverManager.getConnection("jdbc:h2:file:data/resultsA", "sa", "password"), new H2Adapter ) val seshB = Session.create( java.sql.DriverManager.getConnection("jdbc:h2:file:data/resultsB", "sa", "password"), new H2Adapter ) using(seshA){ import Library._ from(sims){s => select(s)}.foreach{item => using(seshB){ sims.insert(item); } } } } case class Simulation( @Column("SIMID") var id: Long, val date: Date ) extends KeyedEntity[Long] object Library extends Schema { val sims = table[Simulation] on(sims)(s => declare( s.id is(unique, indexed, autoIncremented) )) } }

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• Using javascript to call controller methond in mvc

  - by Christian Thoresson Dahl

  Im trying to make a table row work as a link to another view in my mvc website. Instead of using the standard "Details" link provided by the auto generated table list, I would like to use the table row as a link to the "Details" view instead. So somehow I need to make the row work as a link. Each rom has a unique id that I need to pass on to the controller method. I have tried different solutions but noting happens when I press on the table row... So far this is what I have: <script type="text/javascript"> $(document).ready(function(){ $('#customers tr').click(function () { var id = $(this).attr('id'); $.ajax({ url: "Customer/Details" + id, succes: function () { } }); }) }) </script> My controller method: public ActionResult Details(int id) { Customer model = new Customer(); model = this.dbEntities.Customers.Where(c => c.Customer_ID == id).Single(); return View(model); }

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• Why does MySQL autoincrement increase on failed inserts?

  - by Sorcy

  A co-worker just made me aware of a very strange MySQL behavior. Assuming you have a table with an auto_increment field and another field that is set to unique (e.g. a username-field). When trying to insert a row with a username thats already in the table the insert fails, as expected. Yet the auto_increment value is increased as can be seen when you insert a valid new entry after several failed attempts. For example, when our last entry looks like this... ID: 10 Username: myname ...and we try five new entries with the same username value on our next insert we will have created a new row like so: ID: 16 Username: mynewname While this is not a big problem in itself it seems like a very silly attack vector to kill a table by flooding it with failed insert requests, as the MySQL Reference Manual states: "The behavior of the auto-increment mechanism is not defined if [...] the value becomes bigger than the maximum integer that can be stored in the specified integer type." Is this expected behavior?

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• "partial views" best practices for 'container' divs?

  - by ropstah

  What is the 'best' way to handle the html markup for partial views? (which are also refreshed using AJAX) The biggest issue I run into is where to place the 'container' div... Consider having a masterpage and a partial view. (class="" could be interchanged with id="" depending if the partial is guaranteed to be unique, however this isn't really important to the issue i think) Masterpage: <div id="place1" class="placeholder"> <!-- render partial --> </div> Partial: <div id="partial1" class="partial"> <!-- content --> </div> I feel that something isn't being done right. However I cannot remove the div in the masterpage, because I need that to 'encapsulate' the response from AJAX partial updates. And also I cannot move the div in the partial to the masterpage, because that would require to move 'partial' info to the masterpage... How do you handle this?

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• Maximizing the number of threads to fully utilize all available resources without hindering overall

  - by Matt

  Let's say I have to generate a bunch of result files, and I want to make it as fast as possible. Each result file is generated independently of any other result file; in fact, one could say that each result file is agnostic to every other result file. The resources used to generate each result file is also unique to each. How can I dynamically decide the optimal number of threads to run simultaneously in order to minimize the overall run time? Is my only option to write my own thread manager that watches performance counters and adjust accordingly or does there exists some solid classes that already accomplish this?

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• What's the coolest machine you've ever worked on?

  - by mxg

  What's the most exotic, coolest, unique, or interesting machine you've worked on? Most of us work on machines with x86 architectures using some Windows or Linux variant. I'm sure there are those of you out there who are working on or have worked on machines with experimental architecures, or operating systems. Maybe you worked on a machine that has some sigificance in the history of computing. I'd be interested to hear about it. I'm sure others reading SO will as well. EDIT: I appreciate all of you who took some time to talk about their experiences with interesting or unusual machines. I enjoyed reading your answers. Although it wasn't my intent to get nostalgic, I see that theme amongst the responses.

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