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• Where to put data management rules for complex data validation in ASP.NET MVC?

  - by TheRHCP

  Hello, I am currently working on an ASP.NET MVC2 project. This is the first time I am working on a real MVC web application. The ASP.NET MVC website really helped me to get started really fast, but I still have some obscure knowledge concerning datamodel validation. My problem is that I do not really know where to manage my filled datamodel when it comes to complex validation rules. For example, validating a string field with a Regex is quite easy and I know that I just have to decorate my field with a specific attribute, so data management rules are implemented in the model. But if I have multiple fields that I need to validate which each other, for example multiple datetime that need to be correctly set following a specific time rule, where do I need to validate them? I know that I could create my own validation attributes, but sometimes validation ask a specific validation path which is to complex to be validated using attributes. This first question also leads me to a related question which is, is it right to validate a model in the controller? Because for the moment that is the only way I found for complex validation. But I find this a bit dirty and I feel it does not really fit a the controller role and much harder to test (multiple code path). Thanks.

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• Algorithm to see if keywords exist inside a string

  - by rksprst

  Let's say I have a set of keywords in an array {"olympics", "sports tennis best", "tennis", "tennis rules"} I then have a large list (up to 50 at a time) of strings (or actually tweets), so they are a max of 140 characters. I want to look at each string and see what keywords are present there. In the case where a keyword is composed of multiple words like "sports tennis best", the words don't have to be together in the string, but all of them have to show up. I've having trouble figuring out an algorithm that does this efficiently. Do you guys have suggestions on a way to do this? Thanks! Edit: To explain a bit better each keyword has an id associated with it, so {1:"olympics", 2:"sports tennis best", 3:"tennis", 4:"tennis rules"} I want to go through the list of strings/tweets and see which group of keywords match. The output should be, this tweet belongs with keyword #4. (multiple matches may be made, so anything that matches keyword 2, would also match 3 -since they both contain tennis). When there are multiple words in the keyword, e.g. "sports tennis best" they don't have to appear together but have to all appear. e.g. this will correctly match: "i just played tennis, i love sports, its the best"... since this string contains "sports tennis best" it will match and be associated with the keywordID (which is 2 for this example).

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• strange redefined symbols

  - by Chris H

  I included this header into one of my own: http://codepad.org/lgJ6KM6b When I compiled I started getting errors like this: CMakeFiles/bin.dir/SoundProjection.cc.o: In function `Gnuplot::reset_plot()': /usr/lib/gcc/x86_64-pc-linux-gnu/4.3.4/include/g++-v4/new:105: multiple definition of `Gnuplot::reset_plot()' CMakeFiles/bin.dir/main.cc.o:project/gnuplot-cpp/gnuplot_i.hpp:962: first defined here CMakeFiles/bin.dir/SoundProjection.cc.o: In function `Gnuplot::set_smooth(std::basic_string, std::allocator const&)': project/gnuplot-cpp/gnuplot_i.hpp:1041: multiple definition of `Gnuplot::set_smooth(std::basic_string, std::allocator const&)' CMakeFiles/bin.dir/main.cc.o:project/gnuplot-cpp/gnuplot_i.hpp:1041: first defined here CMakeFiles/bin.dir/SoundProjection.cc.o:/usr/include/eigen2/Eigen/src/Core/arch/SSE/PacketMath.h:41: multiple definition of `Gnuplot::m_sGNUPlotFileName' I know it's hard to see in this mess, but look at where the redefinitions are taking place. They take place in files like /usr/lib/gcc/x86_64-pc-linux-gnu/4.3.4/include/g++-v4/new:105. How is the new operator getting information about a gnuplot header? I can't even edit that file. How could that ever even be possible? I'm not even sure how to start debugging this. I hope I've provided enough information. I wasn't able to reproduce this in a small project. I mostly just looking for tips on how to find out why this is happening, and how to track it down. Thanks.

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• Syncing two separate structures to the same master data

  - by Mike Burton

  I've got multiple structures to maintain in my application. All link to the same records, and one of them could be considered the "master" in that it reflects actual relationships held in files on disk. The other structures are used to "call out" elements of the main design for purchase and work orders. I'm struggling to come up with a pattern that deals appropriately with changes to the master data. As an example, the following trees might refer to the same data: A |_ B |_ C |_ D |_ E |_ B |_ C |_ D A |_ B E C |_ D A |_ B C D E These secondary structures follow internal rules, but their overall structure is usually user-determined. In all cases (including the master), any element can be used in multiple locations and in multiple trees. When I add a child to any element in the tree, I want to either automatically build the secondary structure for each instance of the "master" element or at least advertise the situation to the user and allow them to manually generate the data required for the secondary trees. Is there any pattern which might apply to this situation? I've been treating it as a view problem, but it turns out to be more complicated than that when you look at the initial generation of the data.

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• Display gridview in new window

  - by Ricardo Deano

  Hello all. Just a bit of advice needed really in terms of how I should handle my current scenario: I have a web page that searches for products/category information the results of which are at present displayed in a gridview on the same page. However, said gridview is a bit of a beast and as such, I would like to have a page that the user searches for, a button is pressed and the subsequent gridview is displayed in a new window. Ultimately, I would like the user to be able to make multiple searches so that new windows can have multiple gridviews containing different data sets. My current thinking is to create session variables that can be pulled through onto 'the gridview page'. Having said that, I'm not sure that would work if multiple searches are created? I am also thinking I might be able to create said 'gridview window' using javascript but my concern here is the potential loss of functionality of the gridview i.e. paging, sorting, editing, etc. Does anyone have any thoughts or theories on this? What would be "best practise"? Any thoughts greatly appreciated and taken on board. PS: This is being developed in .net, using c# and LINQ. PPS: I'm a noob so be gentle!!

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• Pattern for limiting number of simultaneous asynchronous calls

  - by hitch

  I need to retrieve multiple objects from an external system. The external system supports multiple simultaneous requests (i.e. threads), but it is possible to flood the external system - therefore I want to be able to retrieve multiple objects asynchronously, but I want to be able to throttle the number of simultaneous async requests. i.e. I need to retrieve 100 items, but don't want to be retrieving more than 25 of them at once. When each request of the 25 completes, I want to trigger another retrieval, and once they are all complete I want to return all of the results in the order they were requested (i.e. there is no point returning the results until the entire call is returned). Are there any recommended patterns for this sort of thing? Would something like this be appropriate (pseudocode, obviously)? private List<externalSystemObjects> returnedObjects = new List<externalSystemObjects>; public List<externalSystemObjects> GetObjects(List<string> ids) { int callCount = 0; int maxCallCount = 25; WaitHandle[] handles; foreach(id in itemIds to get) { if(callCount < maxCallCount) { WaitHandle handle = executeCall(id, callback); addWaitHandleToWaitArray(handle) } else { int returnedCallId = WaitHandle.WaitAny(handles); removeReturnedCallFromWaitHandles(handles); } } WaitHandle.WaitAll(handles); return returnedObjects; } public void callback(object result) { returnedObjects.Add(result); }

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• Images in database vs file system

  - by Jesse

  We have a project coming up where we will be building a whole backend CMS system that will power our entire extranet and intranet with one package. The question I have been trying to find an answer to is which is better: storing images in the database (SQL Server 2005) so we may have integrity, single replication plan, etc OR storing on the file system? One issue we have is that we have multiple servers load balanced that require to have the same data at all times. As of now we have SQL replication taking care of that but file replication seems to be a little tougher. Another concern we have is that we would like to have multiple resolutions of the same image, we are not sure if creating and storing each version on the file system would be best or maybe dynamically pulling and creating the resolution image we would like upon request. Our concerns are the with the following: Data integrity Data replication Multiple resolutions Speed of database vs file system Overhead load of database vs file system Data management and backup Does anyone have a similar situation or have any input on what would be recommended? Thanks in advance for the help!

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• If attacker has original data and encrypted data, can they determine the passphrase?

  - by Brad Cupit

  If an attacker has several distinct items (for example: e-mail addresses) and knows the encrypted value of each item, can the attacker more easily determine the secret passphrase used to encrypt those items? Meaning, can they determine the passphrase without resorting to brute force? This question may sound strange, so let me provide a use-case: User signs up to a site with their e-mail address Server sends that e-mail address a confirmation URL (for example: https://my.app.com/confirmEmailAddress/bill%40yahoo.com) Attacker can guess the confirmation URL and therefore can sign up with someone else's e-mail address, and 'confirm' it without ever having to sign in to that person's e-mail account and see the confirmation URL. This is a problem. Instead of sending the e-mail address plain text in the URL, we'll send it encrypted by a secret passphrase. (I know the attacker could still intercept the e-mail sent by the server, since e-mail are plain text, but bear with me here.) If an attacker then signs up with multiple free e-mail accounts and sees multiple URLs, each with the corresponding encrypted e-mail address, could the attacker more easily determine the passphrase used for encryption? Alternative Solution I could instead send a random number or one-way hash of their e-mail address (plus random salt). This eliminates storing the secret passphrase, but it means I need to store that random number/hash in the database. The original approach above does not require storage in the database. I'm leaning towards the the one-way-hash-stored-in-the-db, but I still would like to know the answer: does having multiple unencrypted e-mail addresses and their encrypted counterparts make it easier to determine the passphrase used?

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• Partial Classes - are they bad design?

  - by dferraro

  Hello, I'm wondering why the 'partial class' concept even exists in .NET. I'm working on an application and we are reading a (actually very good) book relavant to the development platform we are implementing at work. In the book he provides a large code base /wrapper around the platform API and explains how he developed it as he teaches different topics about the platform development. Anyway, long story short - he uses partial classes, all over the place, as a way to fake multiple inheritence in C# (IMO). Why he didnt just split the classes up into multiple ones and use composition is beyond me. He will have 3 'partial class' files to make up his base class, each w/ 3-500 lines of code... And does this several times in his API. Do you find this justifiable? If it were me, I'd have followed the S.R.P. and created multiple classes to handle different required behaviors, then create a base class that has instances of these classes as members (e.g. composition). Why did MS even put partial class into the framework?? They removed the ability to expand/collapse all code at each scope level in C# (this was allowed in C++) because it was obviously just allowing bad habits - partial class is IMO the same thing. I guess my quetion is: Can you explain to me when there would be a legitimate reason to ever use a partial class? I do not mean this to be a rant / war thread. I'm honeslty looking to learn something here. Thanks

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• Naming multi-instance performance counters in .NET

  - by Roger Lipscombe

  Most multiple instance performance counters in Windows seem to automatically(?) have a #n on the end if there's more than one instance with the same name. For example: if, in Perfmon, you look under the Process category, you'll see: ... dwm explorer explorer#1 ... I have two explorer.exe processes, so the second counter has #1 appended to its name. When I attempt to do this in a .NET application: I can create the category, and register the instance (using the PerformanceCounterCategory.Create that takes a CounterCreationDataCollection). I can open the counter for write and write to it. When I open the counter a second time, it opens the same counter. This means that I have two applications fighting over the counters. The documentation for PerformanceCounter.InstanceName states that # is not allowed in the name. So: how do I have multiple-instance performance counters that are actually multiple instance? And where the second (and subsequent) instances get #n appended to the name? That is: I know that I can put the process ID (e.g.) on the instance name. This works, but has the unfortunate side effect that restarting the process results in a new PID, and Perfmon continues monitoring the old counter.

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• Merge Multple Worksheets From Multple Workbooks

  - by Droter

  Hi, I have found multiple posts on merging data but I am still running into some problems. I have multiple files with multiple sheets. Example 2007-01.xls...2007-12.xls in each of these files are daily data on sheets labeled 01, 02, 03 ..... There are other sheets in the file so I can't just loop through all worksheets. I need to combine the daily data into monthly data, then all of the monthly data points into yearly. On the monthly data I need it to be added to the bottom of the page. I have added the file open changes for Excel 2007 Here is what I have so far: Sub RunCodeOnAllXLSFiles() Dim lCount As Long Dim wbResults As Workbook Dim wbMaster As Workbook Application. ScreenUpdating = False Application.DisplayAlerts = False Application.EnableEvents = False On Error Resume Next Set wbMaster = ThisWorkbook Dim oWbk As Workbook Dim sFil As String Dim sPath As String sPath = "C:\Users\test\" 'location of files ChDir sPath sFil = Dir("*.xls") 'change or add formats Do While sFil <> "" 'will start LOOP until all files in folder sPath have been looped through Set oWbk = Workbooks.Open(sPath & "\" & sFil) 'opens the file Set oWbk = Workbooks.Open(sPath & "\" & sFil) Sheets("01").Select ' HARD CODED FIRST DAY Range("B6:F101").Select 'AREA I NEED TO COPY Range("B6:F101").Copy wbMaster.Activate Workbooks("wbMaster").ActiveSheet.Range("B65536").End(xlUp)(2).PasteSpecial Paste:=xlValues Application.CutCopyMode = False oWbk.Close True 'close the workbook, saving changes sFil = Dir Loop ' End of LOOP On Error Goto 0 Application.ScreenUpdating = True Application.DisplayAlerts = True Application.EnableEvents = True End Sub Right now it can find the files and open them up and get to the right worksheet but when it tries to copy the data nothing is copied over. Thanks for your help, Matt

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• How to migrate primary key generation from "increment" to "hi-lo"?

  - by Bevan

  I'm working with a moderate sized SQL Server 2008 database (around 120 tables, backups are around 4GB compressed) where all the table primary keys are declared as simple int columns. At present, primary key values are generated by NHibernate with the increment identity generator, which has worked well thus far, but precludes moving to a multiprocessing environment. Load on the system is growing, so I'm evaluating the work required to allow the use of multiple servers accessing a common database backend. Transitioning to the hi-lo generator seems to be the best way forward, but I can't find a lot of detail about how such a migration would work. Will NHibernate automatically create rows in the hi-lo table for me, or do I need to script these manually? If NHibernate does insert rows automatically, does it properly take account of existing key values? If NHibernate does take care of thing automatically, that's great. If not, are there any tools to help? Update NHibernate's increment identifier generator works entirely in-memory. It's seeded by selecting the maximum value of used identifiers from the table, but from that point on allocates new values by a simple increment, without reference back to the underlying database table. If any other process adds rows to the table, you end up with primary key collisions. You can run multiple threads within the one process just fine, but you can't run multiple processes. For comparison, the NHibernate identity generator works by configuring the database tables with identity columns, putting control over primary key generation in the hands of the database. This works well, but compromises the unit of work pattern. The hi-lo algorithm sits inbetween these - generation of primary keys is coordinated through the database, allowing for multiprocessing, but actual allocation can occur entirely in memory, avoiding problems with the unit of work pattern.

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• Many to many table design question

  - by user169867

  Originally I had 2 tables in my DB, [Property] and [Employee]. Each employee can have 1 "Home Property" so the employee table has a HomePropertyID FK field to Property. Later I needed to model the situation where despite having only 1 "Home Property" the employee did work at or cover for multiple properties. So I created an [Employee2Property] table that has EmployeeID and PropertyID FK fields to model this many 2 many relationship. Now I find that I need to create other many-to-many relationships between employees and properties. For example if there are multiple employees that are managers for a property or multiple employees that perform maintenance work at a property, etc. My questions are: 1) Should I create seperate many-to-many tables for each of these situations or should I just create 1 more table like [PropertyAssociatonType] that lists the types of associations an emploee can have with a property and just add a FK field to [Employee2Property] such a PropertyAssociationTypeID that explains what the association is? I'm curious about the pros/cons or if there's another better way. 2) Am I stupid and going about this all worng? Thanks for any suggestions :)

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• What is better in WPF for UI layout, using one Grid, or nested Grids.

  - by Matthijs Wessels

  I am making a UI in WPF, I have a bunch of functional areas and I use a Grid to organize it. Now the Grid that I want is not uniform, as in, some functional area will span multiple cells in the Grid. I was wondering what the best practise is in solving this. Should I create one grid and then for each functional area set it to span multiple cells, or should I split it up into multiple nested Grids. In this image, the leftmost panel (panels separated by the gray bar) is what I want. The middle panel shows one grid where the blue lines are overlapped by a functional area. The rightmost panel shows how I could do it with nested grids. You can see the green grid has one horizontal split. In the bottom cell is the yellow Grid with a vertical split. In side the left cell is the red Grid with again a horizontal split. I was just wondering what is best practise, the middle or the right panel.

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• Iterating Over <select> Using jQuery + Multi Select

  - by Kezzer

  This isn't quite as straight forward as one may think. I'm using a plugin called jQuery MultiSelect and multiple <select options using XSLT as follows: <xsl:for-each select="RootField"> <select id="{RootField}" multiple="multiple" size="3"> <option value=""></option> <xsl:for-each select="ChildField"> <option value="{ChildField}"><xsl:value-of select="ChildField"/></option> </xsl:for-each> </select> </xsl:for-each> The accompanying JavaScript is as follows: var selects = document.getElementsByTagName("select"); $.each(selects, function() { $(this).multiSelect(); }); This allows me to apply the multiSelect(); function to every single <select on the page. The behaviour is quite strange, every other <select is being changed into the dropdown list (all the even ones anyway). I can't see anything wrong in my JavaScript to cause this issue as it would iterate over every single one. To make it more clear, the only lists that have that JavaScript applied to it are ones in position 2, 4, 6 and 8 (out of the 9 which are on the page). Any ideas?

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• Adapter for circle page indicator in android

  - by Charles LAU

  I am currently working on an android application which have multiple pages. I am trying to use Circle page indicator to allow users view multiple pages by flipping over the screen. Each page has seperate XML file for the view and each page has a button which is bind to a java method in the Activity. I would like to know how to initalise all the buttons in the Activity for multiple pages. Because at the moment, I can only initalise the button for the first page of the views. I cannot initalise the button for second and third page. Does anyone know how to achieve this. I have placed all the jobs to be done for all the buttons in a single activity. I am currently using this indicator : http://viewpagerindicator.com/ Here is my adapter for the circle page indicator: @Override public Object instantiateItem(View collection, int position) { inflater = (LayoutInflater) collection.getContext().getSystemService(Context.LAYOUT_INFLATER_SERVICE); int resid = 0; //View v = null;// inflater.inflate( R.layout.gaugescreen, (ViewPager)collection, false ); switch( position ) { case 0: resid = R.layout.gaugescreen; break; case 1: resid= R.layout.liveworkoutstatisticsscreen; break; case 2: resid = R.layout.mapscreen; break; default: resid = R.layout.gaugescreen; break; } View view = inflater.inflate(resid, null); ((ViewPager) collection).addView(view,0); return view; } Does anyone know how to achieve this? Thanks for any help in advance

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• Named previously unnamed branch

  - by Jab

  It seems naming a previously unnamed branch doesn't really work out. It creates a nasty multiple heads problem that I can't find a solution for. Here is the workflow... UserA starts working on feature that they expect to be small, so they just start working(off the default branch). The change turns out to be a large project and will need multiple contributors. So UserA issues... hg branch "Feature1" and continues working, committing locally s needed. UserA then pulls down the changes from the central repo so he can push. At this point, why does hg heads return 3 heads? It shows 2 for default and 1 for Feature1. The first head for default is the latest change by another user on the branch(irrelevant). The second default head is the commit prior to the hg branch "Feature1" commit. The central repository has rules enforced so that only 1 head per branch is allowed, so forcing a push isn't an option. The repo doesn't want multiple heads on the default branch. UserA should be able to push these changes so that other users can see the Feature1 branch and help out. I can't seem to find a way to "correct" this. I don't think I can re-write the branch of the initial commits for the feature, before it was a named branch. I know the initial changes before the named branch are technically on the default branch, but does that mean they will be heads until that Feature1 branch is merged?

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• Thread Safety of C# List<T> for readers

  - by ILIA BROUDNO

  I am planning to create the list once in a static constructor and then have multiple instances of that class read it (and enumerate through it) concurrently without doing any locking. In this article http://msdn.microsoft.com/en-us/library/6sh2ey19.aspx MS describes the issue of thread safety as follows: Public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe. A List can support multiple readers concurrently, as long as the collection is not modified. Enumerating through a collection is intrinsically not a thread-safe procedure. In the rare case where an enumeration contends with one or more write accesses, the only way to ensure thread safety is to lock the collection during the entire enumeration. To allow the collection to be accessed by multiple threads for reading and writing, you must implement your own synchronization. The "Enumerating through a collection is intrinsically not a thread-safe procedure." Statement is what worries me. Does this mean that it is thread safe for readers only scenario, but as long as you do not use enumeration? Or is it safe for my scenario?

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• Django repeating vars/cache issue?

  - by Mark

  I'm trying to build a better/more powerful form class for Django. It's working well, except for these sub-forms. Actually, it works perfectly right after I re-start apache, but after I refresh the page a few times, my HTML output starts to look like this: <input class="text" type="text" id="pickup_addr-pickup_addr-pickup_addr-id-pickup_addr-venue" value="" name="pickup_addr-pickup_addr-pickup_addr-pickup_addr-venue" /> The pickup_addr- part starts repeating many times. I was looking for loops around the prefix code that might have cause this to happen, but the output isn't even consistent when I refresh the page, so I think something is getting cached somewhere, but I can't even imagine how that's possible. The prefix car should be reset when the class is initialized, no? Unless it's somehow not initializing something? class Form(object): count = 0 def __init__(self, data={}, prefix='', action='', id=None, multiple=False): self.fields = {} self.subforms = {} self.data = {} self.action = action self.id = fnn(id, 'form%d' % Form.count) self.errors = [] self.valid = True if not empty(prefix) and prefix[-1:] not in ('-','_'): prefix += '-' for name, field in inspect.getmembers(self, lambda m: isinstance(m, Field)): if name[:2] == '__': continue field_name = fnn(field.name, name) field.label = fnn(field.label, humanize(field_name)) field.name = field.widget.name = prefix + field_name + ife(multiple, '[]') field.id = field.auto_id = field.widget.id = ife(field.id==None, 'id-') + prefix + fnn(field.id, field_name) + ife(multiple, Form.count) field.errors = [] val = fnn(field.widget.get_value(data), field.default) if isinstance(val, basestring): try: val = field.coerce(field.format(val)) except Exception, err: self.valid = False field.errors.append(escape_html(err)) field.val = self.data[name] = field.widget.val = val for rule in field.rules: rule.fields = self.fields rule.val = field.val rule.name = field.name self.fields[name] = field for name, form in inspect.getmembers(self, lambda m: ispropersubclass(m, Form)): if name[:2] == '__': continue self.subforms[name] = self.__dict__[name] = form(data=data, prefix='%s%s-' % (prefix, name)) Form.count += 1 Let me know if you need more code... I know it's a lot, but I just can't figure out what's causing this!

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• Database design - table relationship question

  - by iama

  I am designing schema for a simple quiz application. It has 2 tables - "Question" and "Answer Choices". Question table has 'question ID', 'question text' and 'answer id' columns. "Answer Choices" table has 'question ID', 'answer ID' and 'answer text' columns. With this simple schema it is obvious that a question can have multiple answer choices & hence the need for the answer choices table. However, a question can have only one correct answer and hence the need for the 'answer ID' in the question table. However, this 'answer ID' column in the question table provides a illusion as though there can be multiple questions for a single answer which is not correct. The other alternative to eliminate this illusion is to have another table just for correct answer that will have just 2 columns namely the question ID and the answer ID with a 1-1 relationship between the two tables. However, I think this is redundant. Any recommendation on how best to design this thereby enforcing the rules that a question can have multiple answer choices but only one correct answer? Many Thanks.

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• Is something along the lines of nested memoization needed here?

  - by Daniel

  System.Transactions notoriously escalates transactions involving multiple connections to the same database to the DTC. The module and helper class, ConnectionContext, below are meant to prevent this by ensuring multiple connection requests for the same database return the same connection object. This is, in some sense, memoization, although there are multiple things being memoized and the second is dependent on the first. Is there some way to hide the synchronization and/or mutable state (perhaps using memoization) in this module, or perhaps rewrite it in a more functional style? (It may be worth nothing that there's no locking when getting the connection by connection string because Transaction.Current is ThreadStatic.) type ConnectionContext(connection:IDbConnection, ownsConnection) = member x.Connection = connection member x.OwnsConnection = ownsConnection interface IDisposable with member x.Dispose() = if ownsConnection then connection.Dispose() module ConnectionManager = let private _connections = new Dictionary<string, Dictionary<string, IDbConnection>>() let private getTid (t:Transaction) = t.TransactionInformation.LocalIdentifier let private removeConnection tid = let cl = _connections.[tid] for (KeyValue(_, con)) in cl do con.Close() lock _connections (fun () -> _connections.Remove(tid) |> ignore) let getConnection connectionString (openConnection:(unit -> IDbConnection)) = match Transaction.Current with | null -> new ConnectionContext(openConnection(), true) | current -> let tid = getTid current // get connections for the current transaction let connections = match _connections.TryGetValue(tid) with | true, cl -> cl | false, _ -> let cl = Dictionary<_,_>() lock _connections (fun () -> _connections.Add(tid, cl)) cl // find connection for this connection string let connection = match connections.TryGetValue(connectionString) with | true, con -> con | false, _ -> let initial = (connections.Count = 0) let con = openConnection() connections.Add(connectionString, con) // if this is the first connection for this transaction, register connections for cleanup if initial then current.TransactionCompleted.Add (fun args -> let id = getTid args.Transaction removeConnection id) con new ConnectionContext(connection, false)

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• Codeigniter Inserting Multidimensional Array as rows in MySQL

  - by RisingSun

  Please Refer to this question I asked Codeigniter Insert Multiple Rows in SQL To restate <tr> <td><input type="text" name="user[0][name]" value=""></td> <td><input type="text" name="user[0][address]" value=""><br></td> <td><input type="text" name="user[0][age]" value=""></td> <td><input type="text" name="user[0][email]" value=""></td> </tr> <tr> <td><input type="text" name="user[1][name]" value=""></td> <td><input type="text" name="user[1][address]" value=""><br></td> <td><input type="text" name="user[1][age]" value=""></td> <td><input type="text" name="user[1][email]" value=""></td> </tr> .......... Can Be Inserted into MySQL as this foreach($_POST['user'] as $user) { $this->db->insert('mytable', $user); } This results in multiple MySQL queries. Is it possible to optimise it further, so that the insert occurs in one query Something like this insert multiple rows via a php array into mysql but taking advantage of codeigniters simpler syntax. Thanks

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• If attacker has original data, and encrypted data, can they determine the passphrase?

  - by Brad Cupit

  If an attacker has several distinct items (for example: e-mail addresses) and knows the encrypted value of each item, can the attacker more easily determine the secret passphrase used to encrypt those items? Meaning, can they determine the passphrase without resorting to brute force? This question may sound strange, so let me provide a use-case: User signs up to a site with their e-mail address Server sends that e-mail address a confirmation URL (for example: https://my.app.com/confirmEmailAddress/bill%40yahoo.com) Attacker can guess the confirmation URL and therefore can sign up with someone else's e-mail address, and 'confirm' it without ever having to sign in to that person's e-mail account and see the confirmation URL. This is a problem. Instead of sending the e-mail address plain text in the URL, we'll send it encrypted by a secret passphrase. (I know the attacker could still intercept the e-mail sent by the server, since e-mail are plain text, but bear with me here.) If an attacker then signs up with multiple free e-mail accounts and sees multiple URLs, each with the corresponding encrypted e-mail address, could the attacker more easily determine the passphrase used for encryption? Alternative Solution I could instead send a random number or one-way hash of their e-mail address (plus random salt). This eliminates storing the secret passphrase, but it means I need to store that random number/hash in the database. The original approach above does not require this extra table. I'm leaning towards the the one-way hash + extra table solution, but I still would like to know the answer: does having multiple unencrypted e-mail addresses and their encrypted counterparts make it easier to determine the passphrase used?

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• Modeling many-to-one with constraints?

  - by Greg Beech

  I'm attempting to create a database model for movie classifications, where each movie could have a single classification from each of one of multiple rating systems (e.g. BBFC, MPAA). This is the current design, with all implied PKs and FKs: TABLE Movie ( MovieId INT ) TABLE ClassificationSystem ( ClassificationSystemId TINYINT ) TABLE Classification ( ClassificationId INT, ClassificationSystemId TINYINT ) TABLE MovieClassification ( MovieId INT, ClassificationId INT, Advice NVARCHAR(250) -- description of why the classification was given ) The problem is with the MovieClassification table whose constraints would allow multiple classifications from the same system, whereas it should ideally only permit either zero or one classifications from a given system. Is there any reasonable way to restructure this so that a movie having exactly zero or one classifications from any given system is enforced by database constraints, given the following requirements? Do not duplicate information that could be looked up (i.e. duplicating ClassificationSystemId in the MovieClassification table is not a good solution because this could get out of sync with the value in the Classification table) Remain extensible to multiple classification systems (i.e. a new classification system does not require any changes to the table structure)? Note also the Advice column - each mapping of a movie to a classification needs to have a textual description of why that classification was given to that movie. Any design would need to support this.

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• JPA + EJB + JSF: how can design complicated query

  - by Harry Pham

  I am using netbean 6.8 btw. Let say that I have 4 different tables: Company, Facility, Project, and Document. So the relationship is this. A company can have multiple facilities. A facility can have multiple projects, and a project can have multiple documents. Company: +companyNum: PK +facilityNum: FK Facility: +facilityNum: PK +projectNum: FK Project: +projectNum: PK +drawingNum: FK So when I create Entity Class From Database in netbean 6.8, I have 4 entity classes that named after the above 4 tables. So if I want to see all the Document in the database, then it is easy. In my SessionBean, I would do this: @PersistenceContext private EntityManager em; List<Document> documents = em.createNamedQuery("Document.findAll").getResultList(); However, that is not all what I need. Let say that I want to know all the Document from a particular Company, or all the Document from a particular Project from a particular Facility from a particular Company. I am very new to JPA + EJB + JSF as a whole. Please help me out.

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