complex networks - Page 230

Convert asp.net application to windows forms app

- by rogdawg

I have written and deployed an ASP.NET application that is pretty complex. It uses XSL transformations to create web forms for a large variety of data objects. The data comes from the database as XML via a web service. Now, I need to create a Windows desktop application that will provide a small subset of the web applications functionality to a user who may not have access to the web (working in remote areas). I will provide the data syncing using the MS Sync Framework. And I will have the desktop use a local data store. I would like to use the same xslt files in the desktop app that I use in the web app for the form creation so that, if changes are made, the desktop app can update itself when it connects and syncs its data. But, I am wondering how to replicate the asp.net codebehind logic of my web app in the windows forms. If I use a browser control to render the XSLTransformation result, then how could I handle click events, etc, in the form? Also, can I launch other windows as "dialog boxes" from my windows forms (I do this in my web app using RadControls functionality)? Thanks for any advice you can give.

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Peoplesoft queries - performance

- by DBa

Hi, I'm facing a problem with PeopleSoft queries (using Oracle backend database): when a rather complex query involving multiple records is set off by a user, PS does an enforced join of security records, thus producing SQL like this: select .... from ps_job a, PS_EMPL_SRCQRY a1, ps_table2 b, ps_sec_rcd2 b1, ps_table3 c, ps_sec_rcd3 c1 where (...security joins a-a1, b-b1, c-c1...) and (...joins of a, b and c...) and a.setid_dept = 'XYZ'; (let's assume the last condition has a high selectivity and there is an index on the column) Obviously, due to the arrangement of the conditions, first a huge join is created, written to the temp segment, and when the last condition is finally applied, only a small subset is selected. A query formulated in this way is very likely to hit the preset timeout of the APPSRV, and even of the QRYSRV. When writing the query manually, I would rather move the most selective condition to the start, thus limiting the amount of the data being handled, to a considerable level. Any ideas on how to make PS behave like this? Actually, already rewriting "Oracle-styled" SQL to ANSI SQL seems to accelerate the queries - however, PS writes Oracle-style queries... Thanks in advance DBa

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rails + paperclip: Is a generic "Attachment" model a good idea?

- by egarcia

On my application I've several things with attachments on them, using paperclip. Clients have one logo. Stores can have one or more pictures. These pictures, in addition, can have other information such as the date in which they were taken. Products can have one or more pictures of them, categorized (from the font, from the back, etc). For now, each one of my Models has its own "paperclip-fields" (Client has_attached_file) or has_many models that have attached files (Store has_many StorePictures, Product has_many ProductPictures) My client has also told me that in the future we might be adding more attachments to the system (i.e. pdf documents for the clients to download). My application has a rather complex authorization system implemented with declarative_authorization. One can not, for example, download pictures from a product he's not allowed to 'see'. I'm considering re-factoring my code so I can have a generic "Attachment" model. So any model can has_many :attachments. With this context, does it sound like a good idea? Or should I continue making Foos and FooPictures?

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PGU HTML Renderer can't render most sites

- by None

I am trying to make a web browser using pygame. I am using PGU for html rendering. It works fine when I visit simple sites, like example.com, but when I try and load anything more complex that uses an html form, like google, I get this error: UnboundLocalError: local variable 'e' referenced before assignment I looked in the PGU html rendering file and found this code segment: def start_input(self,attrs): r = self.attrs_to_map(attrs) params = self.map_to_params(r) #why bother #params = {} type_,name,value = r.get('type','text'),r.get('name',None),r.get('value',None) f = self.form if type_ == 'text': e = gui.Input(**params) self.map_to_connects(e,r) self.item.add(e) elif type_ == 'radio': if name not in f.groups: f.groups[name] = gui.Group(name=name) g = f.groups[name] del params['name'] e = gui.Radio(group=g,**params) self.map_to_connects(e,r) self.item.add(e) if 'checked' in r: g.value = value elif type_ == 'checkbox': if name not in f.groups: f.groups[name] = gui.Group(name=name) g = f.groups[name] del params['name'] e = gui.Checkbox(group=g,**params) self.map_to_connects(e,r) self.item.add(e) if 'checked' in r: g.value = value elif type_ == 'button': e = gui.Button(**params) self.map_to_connects(e,r) self.item.add(e) elif type_ == 'submit': e = gui.Button(**params) self.map_to_connects(e,r) self.item.add(e) elif type_ == 'file': e = gui.Input(**params) self.map_to_connects(e,r) self.item.add(e) b = gui.Button(value='Browse...') self.item.add(b) def _browse(value): d = gui.FileDialog(); d.connect(gui.CHANGE,gui.action_setvalue,(d,e)) d.open(); b.connect(gui.CLICK,_browse,None) self._locals[r.get('id',None)] = e I got the error in the last line, because e wasn't defined. I am guessing the reason for this is that the if statement that checks the type of the input and creates the e variable didn't match anything. I added a line to print the _type variable and I got 'hidden' when i tried google and apple. Is there any way to render form items that have the type 'hidden' with PGU?

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Do I need a spatial index in my database?

- by Sanoj

I am designing an application that needs to save geometric shapes in a database. I haven't choosen the database management system yet. In my application, all database queries will have an bounding box as input, and as output I want all shapes within that database. I know that databases with a spatial index is used for this kind of application. But in my application there will not be any queries of type "give me objects nearby x/y" or other more complex queries that are useful in a GIS application. I am planning of having a database without a spatial index and have queries looking like: SELECT * FROM shapes WHERE x < max_x AND x > min_x AND y < max_y AND y > min_y And have an index on the columns x (double) and y (double). As long I can see, I don't really need a database with an spatial index, howsoever my application is close to that kind of applications. And even if I would like to have nearby queries, then I could create a big enough bounding box around that point. Or will this lead to poor performance? Do I really need a spatial database? And when is a spatial index needed?

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Core Data Errors vs Exceptions Part 3

- by John Gallagher

My question is similar to this one. Background I'm creating a large number of objects in a core data store using NSOperations to speed things up. I've followed all the Core Data multithreading rules - I've got a single persistent store coordinator and a managed object context per thread that on save is merging back to the main managed object context. The Problem When the number of threads running at once is more than 1, I get the exception logged on save of my core data store: NSExceptionHandler has recorded the following exception: NSInternalInconsistencyException -- optimistic locking failure What I've Tried My code that creates new entities is quite complex - it makes entities that have relationships with other entities that could be being created in a separate thread. If I replace my object creation routine with some very simple code just making non-related entries, everything works perfectly. Initially, as well as the exceptions, I was getting a save error saying core data couldn't save due to the merge failing. I read the docs and realised I needed a merge policy on the Managed Object Context I was saving to. I set this up and as this question states, the save error goes away, but the exception remains. My Question Do I need to worry about these exceptions? If I do need to get rid of the exceptions, any ideas on how I do it?

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What's the steps for SQL optimization and changes without reflect live system ?

- by Space Cracker

we have a big portal that build using SharePoint 2007 , asp.net 3.5 , SQL Server 2005 .. many developers work in it since 01/2008 and we are now doing huge analysis for current SQL Databases [not share-point DB ] to optimize and enhance it. The main db have about 330 table and 1720 stored procedure (SP) created from 01/2008 till now Many table names / Columns is very long and we want to short it we found SP names is written in 25 format :( , some of them are very complex and also we want to rename many SP parameters need to be renamed one of the biggest table is Registered user table, that will be spitted in more than one table for some optimization, many columns name will be changed I searched for the way that i can rename table names ,columns and i found SQL refactor tool but i still trying it .. my questions : Is SQl Refactor is the best tool for renaming ? or is there any other one ? if i want to make it manually, is there any references or best practice for that ? How can i do such changes in fast and stable way .. i search for recommendations and case studies if exist ?

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R Random Data Sets within loops

- by jugossery

Here is what I want to do: I have a time series data frame with let us say 100 time-series of length 600 - each in one column of the data frame. I want to pick up 4 of the time-series randomly and then assign them random weights that sum up to one (ie 0.1, 0.5, 0.3, 0.1). Using those I want to compute the mean of the sum of the 4 weighted time series variables (e.g. convex combination). I want to do this let us say 100k times and store each result in the form ts1.name, ts2.name, ts3.name, ts4.name, weight1, weight2, weight3, weight4, mean so that I get a 9*100k df. I tried some things already but R is very bad with loops and I know vector oriented solutions are better because of R design. Thanks Here is what I did and I know it is horrible The df is in the form v1,v2,v2.....v100 1,5,6,.......9 2,4,6,.......10 3,5,8,.......6 2,2,8,.......2 etc e=NULL for (x in 1:100000) { s=sample(1:100,4)#pick 4 variables randomly a=sample(seq(0,1,0.01),1) b=sample(seq(0,1-a,0.01),1) c=sample(seq(0,(1-a-b),0.01),1) d=1-a-b-c e=c(a,b,c,d)#4 random weights average=mean(timeseries.df[,s]%*%t(e)) e=rbind(e,s,average)#in the end i get the 9*100k df } The procedure runs way to slow. EDIT: Thanks for the help i had,i am not used to think R and i am not very used to translate every problem into a matrix algebra equation which is what you need in R. Then the problem becomes a little bit complex if i want to calculate the standard deviation. i need the covariance matrix and i am not sure i can if/how i can pick random elements for each sample from the original timeseries.df covariance matrix then compute the sample variance (t(sampleweights)%*%sample_cov.mat%*%sampleweights) to get in the end the ts.weighted_standard_dev matrix Last question what is the best way to proceed if i want to bootstrap the original df x times and then apply the same computations to test the robustness of my datas thanks

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How do I simplify my code?

- by Mitchell Skurnik

I just finished creating my first major application in C#/Silverlight. In the end the total line count came out to over 12,000 lines of code. Considering this was a rewrite of a php/javascript application I created 2 years that was over 28,000 lines I am actually quite proud of my accomplishment. After reading many questions and answers here on stackoverflow and other sites online, I followed many posters advice: I created classes, procedures, and such for things that I would have a year ago copied and pasted; I created logic charts to figure out complex functions; making sure there are no crazy hidden characters (used tabs instead of spaces); and a few others things; place comments where necessary (I have lots of comments). My application consists of 4 tiles laid out horizontally that have user controls loaded into each slice. You can have between one and four slices loaded at anytime. If you have once slice loaded, the slice takes up the entire artboard...if you have 2 loaded, each take up half, 3 a third, 4 a quarter. Each one of these slices represent (for the sake of this example) a light control. Each slice has 3 slider controls in it. Now when I coded the functionality of the sliders, I used a switch/case statement inside of a public function that would run the command on the specified slice/slider. The made for some duplicate code but I saw no way around it as each slice was named differently. So I would do slice1.my.commands(); slice2.my.commands(); etc. My question to you is how do I clean up my code even futher? (Sadly I cannot post any of my code). Is there any way to take this repetion out of my code?

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Accessing both stored procedure output parameters AND the result set in Entity Framework?

- by MS.

Is there any way of accessing both a result set and output parameters from a stored procedure added in as a function import in an Entity Framework model? I am finding that if I set the return type to "None" such that the designer generated code ends up calling base.ExecuteFunction(...) that I can access the output parameters fine after calling the function (but of course not the result set). Conversely if I set the return type in the designer to a collection of complex types then the designer generated code calls base.ExecuteFunction<T>(...) and the result set is returned as ObjectResult<T> but then the value property for the ObjectParameter instances is NULL rather than containing the proper value that I can see being passed back in Profiler. I speculate the second method is perhaps calling a DataReader and not closing it. Is this a known issue? Any work arounds or alternative approaches? Edit My code currently looks like public IEnumerable<FooBar> GetFooBars( int? param1, string param2, DateTime from, DateTime to, out DateTime? createdDate, out DateTime? deletedDate) { var createdDateParam = new ObjectParameter("CreatedDate", typeof(DateTime)); var deletedDateParam = new ObjectParameter("DeletedDate", typeof(DateTime)); var fooBars = MyContext.GetFooBars(param1, param2, from, to, createdDateParam, deletedDateParam); createdDate = (DateTime?)(createdDateParam.Value == DBNull.Value ? null : createdDateParam.Value); deletedDate = (DateTime?)(deletedDateParam.Value == DBNull.Value ? null : deletedDateParam.Value); return fooBars; }

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Visual Basic: Newbie questions.

- by Omega

Hello there. I am starting to learn visual basic. So far, it is quite simple and easy to use. I am liking it! Anyway, I want to make applications a little bit more complex. So far I have done very silly things. I would appreciate if you could help me with these: How do I open a new window (form)? Maybe I click a button on my main form and another form pops up. How do I "deactivate" the main form while the new form is running? (if I try to click the main form, an error sound plays) So my second form has a text field and a "OK" button. If I click it, the second form closes activating the main form again. I want to "pass" the text in the text field from the second form to the first one. How do I do that? Thank you, I am enjoying this new programming environment (didn't use Visual Studio much before)

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Multi-user job/task tracking/queue software

- by Bmsgaffer86

Background: I test and repair electronic products with a team. There are many 'jobs' going through my lab at any point in time. It is getting difficult to track whats coming in and going out because I don't do every test or repair myself. Target: User can enter a job when they drop it off in my lab, and it will appear on the master list or queue. Needs to have priorities and due dates that can be adjusted by users. Ideally this would be web based and open-source, but I am flexible. Dream: A large monitor displaying a list of jobs in the master queue with details. This is very optional though, and would be in the best case scenario. I have done MANY hours of Google-ing and I am not sure if I have been using the right terminology, but I have not found anything that is simple enough to stand alone yet complex enough to be multi-user based. I am mildly proficient in VB, and have the drive to piece anything together that I have to. I am open to ANY help or suggestions.

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Is there a free tool which can help visualize the logic of a stored procedure in SQL Server 2008 R2?

- by Hamish Grubijan

I would like to be able to plot a call graph of a stored procedure. I am not interested in every detail, and I am not concerned with dynamic SQL (although it would be cool to detect it and skip it maybe or mark it as such.) I would like the tool to generate a tree for me, given the server name, db name, stored proc name, a "call tree", which includes: Parent stored procedure. Every other stored procedure that is being called as a child of the caller. Every table that is being modified (updated or deleted from) as a child of the stored proc which does it. Hopefully it is clear what I am after; if not - please do ask. If there is not a tool that can do this, then I would like to try to write one myself. Python 2.6 is my language of choice, and I would like to use standard libraries as much as possible. Any suggestions? EDIT: For the purposes of bounty Warning: SQL syntax is COMPLEX. I need something that can parse all kinds of SQL 2008, even if it looks stupid. No corner cases barred :) EDIT2: I would be OK if all I am missing is graphics.

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Changing style sheets depending on useragent

- by John Vasiliou

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git + partly shared files between branches/repositories. Is it possible?

- by Maxym

One team in company I work for has the following problem. They develop an application, which will have different builds (e.g. different design depending on customer). so they have some code shared between builds, and some specific to build. E.g. first build has (example is meaningless about files, it is just to understand the problem; I don't know exactly which code differs) /src/class1.java /src/class2.java /res/image1.png /res/image2.png second project contains /src/class1.java /src/class3.java /res/image1.png /res/image3.png as you see, both have class1.java and image1.png. Evething else is different. The project is much more complex of course, so to contain everything in one project is not comfortable... But also to make different branches and commit the same code to all of them is not comfortable... probably I picked wrong direction thinking about this problem, but I just took a look at git (we use svn), and it allows separated repositories. The question is: is it possible to make different branches in git, but tell it that "these files should be shared between them" and other files should be only in those branches. Then when developer commits class1.java git synchronizes it in all branches/repositorias etc. Maybe there is another solution which can be easy taken?

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HTML columns or rows for form layout?

- by Valera

I'm building a bunch of forms that have labels and corresponding fields (input element or more complex elements). Labels go on the left, fields go on the right. Labels in a given form should all be a specific width so that the fields all line up vertically. There are two ways (maybe more?) of achieving this: Rows: Float each label and each field left. Put each label and field in a field-row div/container. Set label width to some specific number. With this approach labels on different forms will have different widths, because they'll depend on the width of the text in the longest label. Columns: Put all labels in one div/container that's floated left, put all fields in another floated left container with padding-left set. This way the labels and even the label container don't need to have their widths set, because the column layout and the padding-left will uniformly take care of vertically lining up all the fields. So approach #2 seems to be easier to implement (because the widths don't need to be set all the time), but I think it's also less object oriented, because a label and a field that goes with that label are not grouped together, as they are in approach #1. Also, if building forms dynamically, approach #2 doesn't work as well with functions like addRow(label, field), since it would have to know about the label and the field containers, instead of just creating/adding one field-row element. Which approach do you think is better? Is there another, better approach than these two?

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Tools for debugging when debugger can't get you there?

- by brian1001

I have a fairly complex (approx 200,000 lines of C++ code) application that has decided to crash, although it crashes a little differently on a couple of different systems. The trick is that it doesn't crash or trap out in debugger. It only crashes when the application .EXE is run independently (either the debug EXE or the release EXE - both behave the same way). When it crashes in the debug EXE, and I get it to start debugging, the call stack is buried down into the windows/MFC part of things, and isn't reflecting any of my code. Perhaps I'm seeing a stack corruption of some sort, but I'm just not sure at the moment. My question is more general - it's about tools and techniques. I'm an old programmer (C and assembly language days), and a relative newcomer (couple/few years) to C++ and Visual Studio (2003 for this projecT). Are there tricks or techniques anyone's had success with in tracking down crashing issues when you cannot make the software crash in a debugger session? Stuff like permission issues, for example? The only thing I've thought of is to start plugging in debug/status messages to a logfile, but that's a long, hard way to go. Been there, done that. Any better suggestions? Am I missing some tools that would help? Is VS 2008 better for this kind of thing? Thanks for any guidance. Some very smart people here (you know who you are!). cheers.

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The best way to structure this database?

- by James P

At the moment I'm doing this: gems(id, name, colour, level, effects, source) id is the primary key and is not auto-increment. A typical row of data would look like this: id => 40153 name => Veiled Ametrine colour => Orange level => 80 effects => +12 sp, +10 hit source => Ametrine (Some of you gamers might see what I'm doing here :) ) But I realise this could be sorted a lot better. I have studied database relationships and secondary keys in my A-Level computing class but never got as far as to set one up properly. I just need help with how this database should be organised, like what tables should have what data with what secondary and foreign keys? I was thinking maybe 3 tables: gem, effects, source. Which then have relationships to each other? Can anyone shed some light on this? Is a complex way like I'm proposing really the way to go or should I just carry on with what I'm doing? Cheers.

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How do I call C++/CLI (.NET) DLLs from standard, unmanaged non-.NET applications?

- by tronjohnson

In the unmanaged world, I was able to write a __declspec(dllexport) or, alternatively, use a .DEF file to expose a function to be able to call a DLL. (Because of name mangling in C++ for the __stdcall, I put aliases into the .DEF file so certain applications could re-use certain exported DLL functions.) Now, I am interested in being able to expose a single entry-point function from a .NET assembly, in unmanaged-fashion, but have it enter into .NET-style functions within the DLL. Is this possible, in a simple and straight-forward fashion? What I have is a third-party program that I have extended through DLLs (plugins) that implement some complex mathematics. However, the third-party program has no means for me to visualize the calculations. I want to somehow take these pre-written math functions, compile them into a separate DLL (but using C++/CLI in .NET), but then add hooks to the functions so I can render what's going on under the hood in a .NET user control. I'm not sure how to blend the .NET stuff with the unmanaged stuff, or what to Google to accomplish this task. Specific suggestions with regard to the managed/unmanaged bridge, or alternative methods to accomplish the rendering in the manner I have described would be helpful. Thank you.

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Python: How to transfer varrying length arrays over a network connection

- by Devin

Hi, I need to transfer an array of varying length in which each element is a tuple of two integers. As an example: path = [(1,1),(1,2)] path = [(1,1),(1,2),(2,2)] I am trying to use pack and unpack, however, since the array is of varying length I don't know how to create a format such that both know the format. I was trying to turn it into a single string with delimiters, such as: msg = 1&1~1&2~ sendMsg = pack("s",msg) or sendMsg = pack("s",str(msg)) on the receiving side: path = unpack("s",msg) but that just prints 1 in this case. I was also trying to send 4 integers as well, which send and receive fine, so long as I don't include the extra string representing the path. sendMsg = pack("hhhh",p.direction[0],p.direction[1],p.id,p.health) on the receive side: x,y,id,health = unpack("hhhh",msg) The first was for illustration as I was trying to send the format "hhhhs", but either way the path doesn't come through properly. Thank-you for your help. I will also be looking at sending a 2D array of ints, but I can't seem to figure out how to send these more 'complex' structures across the network. Thank-you for your help.

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C#: How to implement a smart cache

- by Svish

I have some places where implementing some sort of cache might be useful. For example in cases of doing resource lookups based on custom strings, finding names of properties using reflection, or to have only one PropertyChangedEventArgs per property name. A simple example of the last one: public static class Cache { private static Dictionary<string, PropertyChangedEventArgs> cache; static Cache() { cache = new Dictionary<string, PropertyChangedEventArgs>(); } public static PropertyChangedEventArgs GetPropertyChangedEventArgsa(string propertyName) { if (cache.ContainsKey(propertyName)) return cache[propertyName]; return cache[propertyName] = new PropertyChangedEventArgs(propertyName); } } But, will this work well? For example if we had a whole load of different propertyNames, that would mean we would end up with a huge cache sitting there never being garbage collected or anything. I'm imagining if what is cached are larger values and if the application is a long-running one, this might end up as kind of a problem... or what do you think? How should a good cache be implemented? Is this one good enough for most purposes? Any examples of some nice cache implementations that are not too hard to understand or way too complex to implement?

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Call 32-bit or 64-bit program from bootloader

- by user1002358

There seems to be quite a lot of identical information on the Internet about writing the following 3 bootloaders: Infinite loop jmp $ Print a single character Print "Hello World". This is fantastic, and I've gone through these 3 variations with very little trouble. I'd like to write some 32- or 64-bit code in C and compile it, and call that code from the bootloader... basically a bootloader that, for example, sets the computer up to run some simple numerical simulation. I'll start by listing primes, for example, and then maybe some input/output from the user to maybe compute a Fourier transform. I don't know. I haven't found any information on how to do this, but I can already foresee some problems before I even begin. First of all, compiling a C program compiles it into one of several different files, depending on the target. For Windows, it's a PE file. For Linux, it's a .out file. These files are both quite different. In my instance, the target isn't Windows or Linux, it's just whatever I have written in the bootloader. Secondly, where would the actual code reside? The bootloader is exactly 512 bytes, but the program I write in C will certainly compile to something much larger. It will need to sit on my (virtual) hard disk, probably in some sort of file system (which I haven't even defined!) and I will need to load the information from this file into memory before I can even think about executing it. But from my understanding, all this is many, many orders of magnitude more complex than a 12-line "Hello World" bootloader. So my question is: How do I call a large 32- or 64-bit program (written in C/C++) from my 16-bit bootloader.

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Please help!! Is there a better way to write this LINQ query

- by Raj Aththanayake

Hi Is there a better simplified way to write this query. My logic is if collection contains customer ids and countrycodes, do the query ordey by customer id ascending. If there are no contain id in CustIDs then do the order by customer name. Is there a better way to write this query? I'm not really familiar with complex lambdas. var custIdResult = (from Customer c in CustomerCollection where (c.CustomerID.ToLower().Contains(param.ToLower()) && (countryCodeFilters.Any(item => item.Equals(c.CountryCode))) ) select c).ToList(); if (custIdResult.Count > 0) { return from Customer c in custIdResult ( c.CustomerName.ToLower().Contains(param.ToLower()) && countryCodeFilters.Any(item => item.Equals(c.CountryCode)) ) orderby c.CustomerID ascending select c; } else { return from Customer c in CustomerCollection where ( c.CustomerName.ToLower().Contains(param.ToLower()) && countryCodeFilters.Any(item => item.Equals(c.CountryCode)) ) orderby c.CustomerName descending select c; }

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Designing a database for a user/points system? (in Django)

- by AP257

First of all, sorry if this isn't an appropriate question for StackOverflow. I've tried to make it as generalisable as possible. I want to create a database (MySQL, site running Django) that has users, who can be allocated a certain number of points for various types of action - it's a collaborative game. My requirements are to obtain: the number of points a user has the user's ranking compared to all other users and the overall leaderboard (i.e. all users ranked in order of points) This is what I have so far, in my Django models.py file: class SiteUser(models.Model): name = models.CharField(max_length=250 ) email = models.EmailField(max_length=250 ) date_added = models.DateTimeField(auto_now_add=True) def points_total(self): points_added = PointsAdded.objects.filter(user=self) points_total = 0 for point in points_added: points_total += point.points return points_total class PointsAdded(models.Model): user = models.ForeignKey('SiteUser') action = models.ForeignKey('Action') date_added = models.DateTimeField(auto_now_add=True) def points(self): points = Action.objects.filter(action=self.action) return points class Action(models.Model): points = models.IntegerField() action = models.CharField(max_length=36) However it's rapidly becoming clear to me that it's actually quite complex (in Django query terms at least) to figure out the user's ranking and return the leaderboard of users. At least, I'm finding it tough. Is there a more elegant way to do something like this? This question seems to suggest that I shouldn't even have a separate points table - what do people think? It feels more robust to have separate tables, but I don't have much experience of database design.

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Database solution for 200million writes/day, monthly summarization queries

- by sb

Hello. I'm looking for help deciding on which database system to use. (I've been googling and reading for the past few hours; it now seems worthwhile to ask for help from someone with firsthand knowledge.) I need to log around 200 million rows (or more) per 8 hour workday to a database, then perform weekly/monthly/yearly summary queries on that data. The summary queries would be for collecting data for things like billing statements, eg. "How many transactions of type A did each user run this month?" (could be more complex, but that's the general idea). I can spread the database amongst several machines, as necessary, but I don't think I can take old data offline. I'll definitely need to be able to query a month's worth of data, maybe a year. These queries would be for my own use, and wouldn't need to be generated in real-time for an end-user (they could run overnight, if needed). Does anyone have any suggestions as to which databases would be a good fit? P.S. Cassandra looks like it would have no problem handling the writes, but what about the huge monthly table scans? Is anyone familiar with Cassandra/Hadoop MapReduce performance?

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