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  • Is it a good idea to use MySQL and Neo4j together?

    - by Sanoj
    I will make an application with a lot of similar items (millions), and I would like to store them in a MySQL database, because I would like to do a lot of statistics and search on specific values for specific columns. But at the same time, I will store relations between all the items, that are related in many connected binary-tree-like structures (transitive closure), and relation databases are not good at that kind of structures, so I would like to store all relations in Neo4j which have good performance for this kind of data. My plan is to have all data except the relations in the MySQL database and all relations with item_id stored in the Neo4j database. When I want to lookup a tree, I first search the Neo4j for all the item_id:s in the tree, then I search the MySQL-database for all the specified items in a query that would look like: SELECT * FROM items WHERE item_id = 45 OR item_id = 345435 OR item_id = 343 OR item_id = 78 OR item_id = 4522 OR item_id = 676 OR item_id = 443 OR item_id = 4255 OR item_id = 4345 Is this a good idea, or am I very wrong? I haven't used graph-databases before. Are there any better approaches to my problem? How would the MySQL-query perform in this case?

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  • Avoiding class_eval in Ruby metaprogramming

    - by Peter
    I want to have a return_empty_set class method in Ruby, similar to the attr_reader methods. My proposed implementation is class Class def return_empty_set *list list.each do |x| class_eval "def #{x}; Set.new; end" end end end and example usage: class Foo return_empty_set :one end Foo.new.one # returns #<Set: {}> but resorting to a string seems like quite a hack. Is there a cleaner or better way to write this, perhaps avoiding class_eval? Or is this the best way to go?

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  • Better code for accessing fields in a matlab structure array?

    - by John
    I have a matlab structure array Modles1 of size (1x180) that has fields a, b, c, ..., z. I want to understand how many distinct values there are in each of the fields. i.e. max(grp2idx([foo(:).a])) The above works if the field a is a double. {foo(:).a} needs to be used in the case where the field a is a string/char. Here's my current code for doing this. I hate having to use the eval, and what is essentially a switch statement. Is there a better way? names = fieldnames(Models1); for ix = 1 : numel(names) className = eval(['class(Models1(1).',names{ix},')']); if strcmp('double', className) || strcmp('logical',className) eval([' values = [Models1(:).',names{ix},'];']); elseif strcmp('char', className) eval([' values = {Models1(:).',names{ix},'};']); else disp(['Unrecognized class: ', className]); end % this line requires the statistics toolbox. [g, gn, gl] = grp2idx(values); fprintf('%30s : %4d\n',names{ix},max(g)); end

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  • Anyone Know a Great Sparse One Dimensional Array Library in Python?

    - by TheJacobTaylor
    I am working on an algorithm in Python that uses arrays heavily. The arrays are typically sparse and are read from and written to constantly. I am currently using relatively large native arrays and the performance is good but the memory usage is high (as expected). I would like to be able to have the array implementation not waste space for values that are not used and allow an index offset other than zero. As an example, if my numbers start at 1,000,000 I would like to be able to index my array starting at 1,000,000 and not be required to waste memory with a million unused values. Array reads and writes needs to be fast. Expanding into new territory can be a small delay but reads and writes should be O(1) if possible. Does anybody know of a library that can do it? Thanks!

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  • Second level cache for entities with where clause

    - by bertolami
    I am wondering where the hibernate second level cache works as expected if I put a where clause in the hbm.xml class definition: <hibernate-mapping> <class name="com.clazzes.A" table="TABLE_A" mutable="false" where="xyz=5" > <cache usage="read-only"/> <id name="id" /> ... Will hibernate still put the id as key into the cache, or do I have enable the query cache? E.g. when I then execute a HQL query like from A where id=2 that results in an SQL similar to select * from TABLE_A where id=2 and (xyz=5). If I execute this query twice, will it consider the second level cache, or will it nevertheless execute the SQL twice?

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  • ContextSwitchDeadlock Was Detected error in C#

    - by assassin
    Hi, I am running a C# application, and during run-time I get the following error: The CLR has been unable to transition from COM context 0x20e480 to COM context 0x20e5f0 for 60 seconds. The thread that owns the destination context/apartment is most likely either doing a non pumping wait or processing a very long running operation without pumping Windows messages. This situation generally has a negative performance impact and may even lead to the application becoming non responsive or memory usage accumulating continually over time. To avoid this problem, all single threaded apartment (STA) threads should use pumping wait primitives (such as CoWaitForMultipleHandles) and routinely pump messages during long running operations. Can anyone please help me out with the problem here? Thanks a lot.

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  • What is the impact/limitation of oracle select with large number of bind variables?

    - by Igal Serban
    We had our oracle server chocking during processing a select statement with close to 3500(!!) bind variables. This select is, obviously, build dynamically by code that we can't change. During the execution of this select the db server went to 100% cpu usage and our system almost halted. We know how to reproduce this problem. So we can prevent this specific condition. But I am wondering if there is a way to protect the db ( by configuration) from this type of problems.

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  • How do you encrypt data between client and server running in Flash and Java?

    - by ArmlessJohn
    We have a multiclient system where the client is written in Flash and the server is written in Java. Currently, communication is done in Flash by usage of flash.net.Socket and the protocol is written in JSON. The server uses a custom port to receive connections and then proceed to talk with each client. As expected, data is sent and received on both fronts as raw bytes, which are then decoded as needed. We would like to encrypt the communication between clients and server. I have some basic understanding about public/private key encryption, but I do not know what is the best way to exchange keys or what libraries are available (on both languages) to do this. What would be the best strategy to attack this problem and where should I start looking for libraries/methods to implement this encryption?

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  • WF4RC, How to: Activity to Xaml?

    - by johnny g
    Hello all, I have Googled a bit, and cannot seem to find any examples of Xaml-fying Activities - good, bad, or otherwise! public static string ToXaml (this Activity activity) { // i would use ActivityXamlServices to go from Xaml // to activity, but how to go other way? documentation // is slim, and cannot infer proper usage of // ActivityXamlServices from Xml remarks :S string xaml = string.Empty; return xaml; } Hints, tips, pointers would be welcome :) NOTE: so found this. Will work through and update once working. Anyone wanna beat me to the punch, by all means. Better yet, if you can find a way to be rid of WorkflowDesigner, seems odd it is required.

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  • WPF: How to efficiently update an Image 30 times per second

    - by John
    Hello, I'm writing a WPF application that uses a component, and this component returns a pointer (IntPtr) to pixels of a bitmap (stride * height). I know in advance that the bitmap is a 24bits rgb, its width and height. Updating the Image control with these bitmaps makes up a video to the user, but I'm not sure what's the most efficient way to do that, most of the time the CPU usage goes to 75%+ and memory changing from 40mb to 500mb and the nI think GC starts to work and then it drops again to 40mm. The app starts to not be responsive. What shoud I do? thanks!

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  • SQL Azure server as unit of billing

    - by vtortola
    Hi, One of the azure training kit presentation says: Each account has zero or more logical servers Provisioned via a common portal Establishes a billing instrument Each logical server has one or more databases Contains metadata about database & usage Unit of authentication, geo-location, billing, reporting Generated DNS-based name Each database has standard SQL objects Users, Tables, Views, Indices, etc Unit of consistency So now I'm lost :D. Were not the databases themselves the units of billing? I mean, I thought that servers were just like logical containers and you were charged per number and size of databases. How servers are billed? Thanks.

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  • Clean way to output values in ASP.NET MVC Views when value is not null

    - by Swoop
    Is there a better way to write the code below? I have quite a few blocks that are similar, and this is making the code in the Viewpage very messy to work with. The data value with the associated label only needs to be output when certain conditions are met, which is almost always if the value is not null. The options I can think is to use a response.write to atleast minimize the usage of the ASP script tags, or to format the webpage is such a way that the label displays with an appropriate n/a type value. <% if (myData.Balance != null) { %> Balance: <%= String.Format("{0:C}", (myData.Balance))%> <% } %>

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  • How do I open a hardware accelarated DirectX window on a secondary screen

    - by user567021
    I'm looking to create a hardware accelarated DirectX (9 at the moment) window on a secondary screen. This screen is connected to the same graphics display as the primary screen (at least at the moment). Currently, when I try to open the window on the secondary screen based on window position or by dragging it there, CPU usage jumps by about 10%, which seems to indicate that windows is switching to a software fallback rather than the hardware accelaration. Machine is windows XP running a NVIDIA graphics card (varying cards as this runs on several machines), with the latest driver. It's also running CUDA at the same time to produce the images if that matters. Programming language is c++, manual window and message queue creation, no tookbox used at the moment to manage the GUI Thanks

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  • PHP / javascript live chat using too much bandwidth

    - by David
    So I am learning about javascript, so I am making a live chat system with PHP and javascript. I have it so the javascript refreshes the log (each message gets logged in a file on the server), and it refreshes every second. Im using firebug to monitor the resource usage, and I see under the net tab each times its updated, and the bytes add up really fast. I know I can change it to update less, but is there a way that when a user on the other end I'm talking to, when the send a message, it gets sent to the server, then an alert gets sent to me saying that the chatlog needs to update somehow. That way it only updates when the log is updated. let me know, thanks

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  • Access violation reading location 0x00184000.

    - by numerical25
    having troubles with the following line HR(md3dDevice->CreateBuffer(&vbd, &vinitData, &mVB)); it appears the CreateBuffer method is having troubles reading &mVB. mVB is defined in box.h and looks like this ID3D10Buffer* mVB; Below is the code it its entirety. this is all files that mVB is in. //Box.cpp #include "Box.h" #include "Vertex.h" #include <vector> Box::Box() : mNumVertices(0), mNumFaces(0), md3dDevice(0), mVB(0), mIB(0) { } Box::~Box() { ReleaseCOM(mVB); ReleaseCOM(mIB); } float Box::getHeight(float x, float z)const { return 0.3f*(z*sinf(0.1f*x) + x*cosf(0.1f*z)); } void Box::init(ID3D10Device* device, float m, float n, float dx) { md3dDevice = device; mNumVertices = m*n; mNumFaces = 12; float halfWidth = (n-1)*dx*0.5f; float halfDepth = (m-1)*dx*0.5f; std::vector<Vertex> vertices(mNumVertices); for(DWORD i = 0; i < m; ++i) { float z = halfDepth - (i * dx); for(DWORD j = 0; j < n; ++j) { float x = -halfWidth + (j* dx); float y = getHeight(x,z); vertices[i*n+j].pos = D3DXVECTOR3(x, y, z); if(y < -10.0f) vertices[i*n+j].color = BEACH_SAND; else if( y < 5.0f) vertices[i*n+j].color = LIGHT_YELLOW_GREEN; else if (y < 12.0f) vertices[i*n+j].color = DARK_YELLOW_GREEN; else if (y < 20.0f) vertices[i*n+j].color = DARKBROWN; else vertices[i*n+j].color = WHITE; } } D3D10_BUFFER_DESC vbd; vbd.Usage = D3D10_USAGE_IMMUTABLE; vbd.ByteWidth = sizeof(Vertex) * mNumVertices; vbd.BindFlags = D3D10_BIND_VERTEX_BUFFER; vbd.CPUAccessFlags = 0; vbd.MiscFlags = 0; D3D10_SUBRESOURCE_DATA vinitData; vinitData.pSysMem = &vertices; HR(md3dDevice->CreateBuffer(&vbd, &vinitData, &mVB)); //create the index buffer std::vector<DWORD> indices(mNumFaces*3); // 3 indices per face int k = 0; for(DWORD i = 0; i < m-1; ++i) { for(DWORD j = 0; j < n-1; ++j) { indices[k] = i*n+j; indices[k+1] = i*n+j+1; indices[k+2] = (i*1)*n+j; indices[k+3] = (i*1)*n+j; indices[k+4] = i*n+j+1; indices[k+5] = (i*1)*n+j+1; k+= 6; } } D3D10_BUFFER_DESC ibd; ibd.Usage = D3D10_USAGE_IMMUTABLE; ibd.ByteWidth = sizeof(DWORD) * mNumFaces*3; ibd.BindFlags = D3D10_BIND_INDEX_BUFFER; ibd.CPUAccessFlags = 0; ibd.MiscFlags = 0; D3D10_SUBRESOURCE_DATA iinitData; iinitData.pSysMem = &indices; HR(md3dDevice->CreateBuffer(&ibd, &iinitData, &mIB)); } void Box::Draw() { UINT stride = sizeof(Vertex); UINT offset = 0; md3dDevice->IASetVertexBuffers(0, 1, &mVB, &stride, &offset); md3dDevice->IASetIndexBuffer(mIB, DXGI_FORMAT_R32_UINT, 0); md3dDevice->DrawIndexed(mNumFaces*3, 0 , 0); } //Box.h #ifndef _BOX_H #define _BOX_H #include "d3dUtil.h" Box.h class Box { public: Box(); ~Box(); void init(ID3D10Device* device, float m, float n, float dx); void Draw(); float getHeight(float x, float z)const; private: DWORD mNumVertices; DWORD mNumFaces; ID3D10Device* md3dDevice; ID3D10Buffer* mVB; ID3D10Buffer* mIB; }; #endif Thanks again for the help

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  • Howto read system informations in C++ on windows and linux?

    - by f4
    I need to read system information like cpu/ram/disks usage in C++. Maybe swap, network and process too but that's less important. It has probably been done thousand of times before so I first tried to search for a library. Someone here suggested SIGAR, which seems to fit my needs but is GPL and it is for inclusion in a proprietary product. So it's not an option here. I feel like it's something not that easy to implement, as it'll need testing on several platforms. So a library would be welcome. If you don't know of any library, could you point me in the right direction for both platforms?

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  • string manipulations in C

    - by Vivek27
    Following are some basic questions that I have with respect to strings in C. If string literals are stored in read-only data segment and cannot be changed after initialisation, then what is the difference between the following two initialisations. char *string = "Hello world"; const char *string = "Hello world"; When we dynamically allocate memory for strings, I see the following allocation is capable enough to hold a string of arbitary length.Though this allocation work, I undersand/beleive that it is always good practice to allocate the actual size of actual string rather than the size of data type.Please guide on proper usage of dynamic allocation for strings. char *string = (char *)malloc(sizeof(char));

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  • Integrating Prolog with C#

    - by TK
    Does anyone know of a nice (and preferably free) way to integrate Prolog and C#? Im looking to create a Prolog dll or similar to call from my managed code, and retrieve an answer once all the processing has been complete. Im looking for it to be predominantly one sided (c# calls Prolog). I have seen this question which talks about Prologs real world usage but I was wondering if anyone had either any experience with c# & Prolog? or a nice tutorial/article?

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  • What about the Sql transaction log

    - by Michel
    Hi, i always thought that the sql transaction log keeps track of all the transactions done in the database so it could help recovering the database file in case of a unexpected power down or something like that So then, in normal usage, when the data is committed and written to disk, it is cleared because all the data is nice and safe in the mdf file. Seeing the ldf file grow and reading some i understand that that is not the case, and it will keep growing, until: you shrink the log. Only at that point all the commited transactions are cleared and the log file is shrinked. I found some sp's who should do this, but also found the theory that you first have to backup the database? That last step doesn't make sense to me, so can anyone tell me of that is correct and if so, why that is?

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  • Have parameters in Dao methods to get entities the most efficient way for read-only access

    - by Blankman
    Allot of my use of hibernate, at least for that data that is presented on many parts of the web application, is for read-only purposes. I want to add some parameters to my Dao methods so I can modify the way hibernate pulls the data and how it handles transactions etc. Example usage: Data on the front page of my website is displayed to the users, it is read-only, so I want to avoid any session/entity tracking that hibernate usually does. This is data that is read-only, will not be changed in this transaction, etc. What would be the most performant way to pull the data? (the code below is c#/nhibernate, I'm implementing this in java as I learn it) public IList<Article> GetArticles() { return Session.CreateCriteria(typeof(Article)) // some where cluase }

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  • What other Freemarker JSP Tag libraries are out-there?

    - by Mat Banik
    I have been using Freemarker for a while and found displaytag library very useful. I just wondering if there are any other libraries that could be used in similar means as displaytag, which have been very helpful to you in development: FTL page <#assign display=JspTaglibs["/WEB-INF/tlds/displaytag.tld"]/> <@display.table uid="items" name="items" pagesize=10 class="table"> <@display.column title="Category" property="category.name"/> <@display.column title="Delivery" property="delivery"/> </@display.table> Example of usage would be appreciated since most of the JSP tag libs don't have them.

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  • How can I use the Scala program schema2src?

    - by pr1001
    This perhaps more a Server Fault question... I installed schema2src via sbaz and now I would like to convert a DTD (Apple's plist schema) to Scala source. $ schema2src usage: schema2src [flags] --module mname arg* or schema2src dtd arg* or (experimental) schema2src xsd arg* (this doesn't work at all yet) where supported [flags] may be: --verbose prints some debugging information However, if I try give any argument, it appears it can't find Scala: $ schema2src --verbose Exception in thread "main" java.lang.NoClassDefFoundError: scala/runtime/BoxesUtility at schema2src.Main$.processArgs(Main.scala:56) at schema2src.Main$.main(Main.scala:25) at schema2src.Main.main(Main.scala) Caused by: java.lang.ClassNotFoundException: scala.runtime.BoxesUtility at java.net.URLClassLoader$1.run(URLClassLoader.java:200) at java.security.AccessController.doPrivileged(Native Method) at java.net.URLClassLoader.findClass(URLClassLoader.java:188) at java.lang.ClassLoader.loadClass(ClassLoader.java:315) at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:330) at java.lang.ClassLoader.loadClass(ClassLoader.java:250) at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:398) ... 3 more I have scala in my PATH... Any suggestions? Assuming that problem can be fixed, is this the correct syntax? $ schema2src PropertyList-1.0.dtd

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  • CSS "and" and "or"

    - by Misiur
    Hi there. I've got quite big trouble, because i need to anathematise from styling some input types. I had something like: .registration_form_right input:not([type="radio") { //Nah. } But i don't want to style checkboxes too. I've tried: .registration_form_right input:not([type="radio" && type="checkbox"]) .registration_form_right input:not([type="radio" && "checkbox"]) .registration_form_right input:not([type="radio") && .registration_form_right input:not(type="checkbox"]) How to use &&? And I'll need to use || soon, and I think that usage will be same. Thanks.

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  • Multiple indexes for a Java Collection - most basic solution?

    - by chris_l
    Hi, I'm looking for the most basic solution to create multiple indexes on a Java Collection. Required functionality: When a Value is removed, all index entries associated with that value must be removed. Index lookup must be faster than linear search (at least as fast as a TreeMap). Side conditions: It should ideally work with JavaSE (6.0) alone - no extra libraries, if possible. If necessary, then only small (not something like Lucene), common and well tested libraries. No database! Of course, I could write a class that manages multiple Maps myself. But I'd like to know, if it can be done without - while still getting a simple usage similar to using a single indexed java.util.Map. Thanks, Chris

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  • How can I do this Aggrigate, group by, in query in LINQ?

    - by Ólafur Waage
    Please do not give me a full working example, I want to know how this is done rather than to get some code I can copy paste This is the query I need, and can't for the life of me create it in LINQ. SELECT * FROM dbo.Schedules s, dbo.Videos v WHERE s.VideoID = v.ID AND s.ID IN ( SELECT MAX(ID) FROM dbo.Schedules WHERE ChannelID = 1 GROUP BY VideoID ) ORDER BY v.Rating DESC, s.StartTime DESC I have the "IN" query in LINQ I think, it's something like this var uniqueList = from schedule in db.Schedules where schedule.ChannelID == channelID group schedule by schedule.VideoID into s select new { id = s.Max(i => i.ID) }; It is possibly wrong, but now I can not check in another query for this in a where clause uniqueList.Contains(schedule.ID) There is possibly a better way to write this query, if you have any idea I would love some hints. I get this error and it's not making much sense. The type arguments for method 'System.Linq.Queryable.Contains(System.Linq.IQueryable, TSource)' cannot be inferred from the usage. Try specifying the type arguments explicitly.

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