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• MySQL - are FK's useful / viable in a web app?

  - by yoda

  Hi all, I've encountered this discussion related to FK's and web applications. Basically some people say that FK's in web applications doesn't represent a real improvement and can even make the application slower in some cases. What do you guys think, what's your experience? -- A quote from Heikki Tuuri, creator of InnoDB engine, founder and CEO of Innobase: InnoDB checks foreign keys as soon as a row is updated, no batching is performed or checks delayed till transaction commit Foreign keys are often serious performance overhead, but help maintain data consistency Foreign Keys increase amount of row level locking done and can make it spread to a lot of tables besides the ones directly updated

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• How can I calculate data for a boxplot (quartiles, median) in a Rails app on Heroku? (Heroku uses Po

  - by hadees

  I'm trying to calculate the data needed to generate a box plot which means I need to figure out the 1st and 3rd Quartiles along with the median. I have found some solutions for doing it in Postgresql however they seem to depend on either PL/Python or PL/R which it seems like Heroku does not have either enabled for their postgresql databases. In fact I ran "select lanname from pg_language;" and only got back "internal". I also found some code to do it in pure ruby but that seems somewhat inefficient to me. I'm rather new to Box Plots, Postgresql, and Ruby on Rails so I'm open to suggestions on how I should handle this. There is a possibility to have a lot of data which is why I'm concerned with performance however if the solution ends up being too complex I may just do it in ruby and if my application gets big enough to warrant it get my own Postgresql I can host somewhere else. *note: since I was only able to post one link, cause I'm new, I decided to share a pastie with some relevant information

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• What is the best possible technology for pulling huge data from 4 remote servers

  - by Habib Ullah Bahar

  Hello, For one of our project, we need to pull huge real time stock data from 4 remote servers across two countries. The trivial process here, check the sources for a regular interval and save the update to database. But as these are real time stock data of more than 1000 companies, I have to pull every second, which isn't good in case of memory, bandwidth I think. Please give me suggestion on which technology/platform [We are flexible here. PHP, Python, Java, PERL - anyone of them will be OK for us] we should choose, it can be achieved easily and with better performance.

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• What are the main benefits of implementing a virtual machine as part of an application?

  - by Marplesoft

  Several databases I've been looking at recently implement a virtual machine internally to perform the respective data reads and writes. For an example, check out this article on SQLite's virtual machine they call the 'VDBE'. I'm curious as to what the benefits of such an architecture are. I would assume performance is one but why would a virtual machine like this run faster? In fact, it seems to be that this extra layer could cause it to run slower. So perhaps it's for security? Or portability? Anyway, just curious about this.

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• Finding the Formula for a Curve

  - by Mystagogue

  Is there a program that will take "response curve" values from me, and provide a formula that approximates the response curve? It would be cool if such a program would take a numeric "percent correct" (perhaps with a standard deviation) so that it returns simplified formulas when laxity is permissable, and more precise (viz. complex) formulas when the curve needs to be approximated closely. My interest is to play with the response curve values and "laxity" factor, until such a tool spits out a curve-fit formula simple enough that I know it will be high performance during machine computations.

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• GWT : Type of Container

  - by moorsu

  I see that there are two ways of transferring objects from server to client Use the same domain object (Contact.java) as used in the service layer. (I do not use hibernate) Use the HashMap to send the domain object field values in the form of Map with the help of BeanUtilsBean class. For multiple objects, use the List. Similary, use the Map to submit form values from client to server Is there any performance advantage for option 1 over 2?. Is there a way to hide the classname/package name that is sent to the browser if we use option 1?. thanks!.

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• What is the best solution to do Reporting on Object data for .NET ?

  - by Peter Fox

  Hi, Our projects are using objects as the data source to reports. Our business layer is returning single objects or IEnumerable. Our reports (quite complex) need to display value-type properties of the object, and its related objects. Typical case would be, from a List, display a master report with category data, then a subreport with data for each Product inside each Category, then a subreport for each Part of each Product, and so on. Reporting from the database is not an option for us. We have tried so far - Reporting Services : works but have to mess around with the XML definition of the report to define the datasource classes, very hard to work with if you use an object datasource, architecturally not too clean - Telerik Reports : quite nice (esp., nice architecture) but seems to have problems with complex reports (master/sub), does not give great paging control, rumored to have performance/crash problems (immature product). Does anyone know a good reporting solution that can be integrated in an ASP.NET application and works well with objects as datasources ?

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• Linux, how to capture screen, and simulate mouse movements.

  - by 2di

  Hi All I need to capture screen (as print screen) in the way so I can access pixel color data, to do some image recognition, after that I will need to generate mouse events on the screen such as left click, drag and drop (moving mouse while button is pressed, and then release it). Once its done, image will be deleted. Note: I need to capture whole screen everything that user can see, and I need to simulate clicks outside window of my program (if it makes any difference) Spec: Linux ubuntu Language: C++ Performance is not very important,"print screen" function will be executed once every ~10 sec. Duration of the process can be up to 24 hours so method needs to be stable and memory leaks free (as usuall :) I was able to do in windows with win GDI and some windows events, but I'ev no idea how to do it in Linux. Thanks a lot

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• HSM - cryptoki - opening sessions overhead

  - by Raj

  I am having a query regarding sessions with HSM. I am aware that there is an overhead if you initialise and finalise the cryptoki api for every file you want to encrypt/decrypt. My queries are, Is there an overhead in opening and closing individual sessions for every file, you want to encrypt/decrypt.(C_Initialize/C_Finalize) How many maximum number of sessions can i have for a HSM simultaneously, with out affecting the performance? Is opening and closing the session for processing individual files the best approach or opening a session and processing multiple files and then closing the session the best approach? Thanks

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• Python urllib3 and how to handle cookie support?

  - by bigredbob

  So I'm looking into urllib3 because it has connection pooling and is thread safe (so performance is better, especially for crawling), but the documentation is... minimal to say the least. urllib2 has build_opener so something like: #!/usr/bin/python import cookielib, urllib2 cj = cookielib.CookieJar() opener = urllib2.build_opener(urllib2.HTTPCookieProcessor(cj)) r = opener.open("http://example.com/") But urllib3 has no build_opener method, so the only way I have figured out so far is to manually put it in the header: #!/usr/bin/python import urllib3 http_pool = urllib3.connection_from_url("http://example.com") myheaders = {'Cookie':'some cookie data'} r = http_pool.get_url("http://example.org/", headers=myheaders) But I am hoping there is a better way and that one of you can tell me what it is. Also can someone tag this with "urllib3" please.

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• SELECT INTO or Stored Procedure?

  - by Kerry

  Would this be better as a stored procedure or leave it as is? INSERT INTO `user_permissions` ( `user_id`, `object_id`, `type`, `view`, `add`, `edit`, `delete`, `admin`, `updated_by_user_id` ) SELECT `user_id`, $object_id, '$type', 1, 1, 1, 1, 1, $user_id FROM `user_permissions` WHERE `object_id` = $object_id_2 AND `type` = '$type_2' AND `admin` = 1 You can think of this with different objects, lets say you have groups and subgroups. If someone creates a subgroup, it is making everyone who had access to the parent group now also have access to the subgroup. I've never made a stored procedure before, but this looks like it might be time. This call be probably be called very often. Should I be creating a procedure or will the performance be insignificant?

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• Deleting orphans with JPA

  - by homaxto

  I have a one-to-one relation where I use CascadeType.PERSIST. This has over time build up a huge amount of child records that has not been deleted, to such an extend that it is reflected in the performance. Now I wish to add some code that cleans up the database removing all the child records that are not referenced by a parent. At the moment we are talking 400K+ records, at I need to run the code on all customer installations just to be sure they do not run into the same problem. I think the best solution would be to run a named query (because we support two databases) that deletes the necessary records, and this is where I get into problems, because how should I write it in JPQL? The result I want can be defined like the following sql statement, which unfortunaltely does not run on MySQL. DELETE FROM child c1 WHERE c1.pk NOT IN (SELECT DISTINCT p.pk FROM child c2 JOIN parent p ON p.child = c2.pk);

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• Extraction Event

  - by Anicho

  So I have the following code: public override void Extract(object sender, ExtractionEventArgs e) { if (e.Response.HtmlDocument != null) { var myParam = e.Request.QueryStringParameters.Where(parameter => parameter.Name == QueryName).Select(parameter => parameter.Value).Distinct(); myParam. // add the extracted value to the web performance test context e.WebTest.Context.Add(this.ContextParameterName, myParam.ToString()); e.Success = true; return; } // If the extraction fails, set the error text that the user sees e.Success = false; e.Message = String.Format(CultureInfo.CurrentCulture, "Not Found: {0}", QueryName); } It's returning: System.Linq.Enumerable+<DistinctItem>d_81`1[system.string] I am expecting something along the lines of: 0152-1231-1231-123d My question is how do I extract the querystring's actual value from extractioneventargs. They say it's possible, but I have no idea.

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• How can I dynamically inject code to event handlers in Delphi?

  - by mjustin

  For debugging / performance tests I would like to dynamically add logging code to all event handlers of components of a given type. For example, for all Dataset components located ona TDatamodule, I would like to add some code for the BeforeOpen and the AfterOpen event to store the start and end time and send a line to a logger with the elapsed time in the AfterOpen event. I would prefer to do this dynamically (no component subclassing), so that I can add this to all existing datamodules and forms with minimal effort only when needed. Iterating all components and filtering by their type is easy, but for the components which already have event handlers assigned, I need a way to store the existing event handlers, and assign a new modified event handler which first does the logging and then will invoke the original code which was already present. Is there a design pattern which can be applied, or even some example code which shows how to implement this in Delphi?

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• Best practice for Python Assert

  - by meade

  Is there a performance or code maintenance issue with using assert as part of the standard code instead of using it just for debugging purposes? Is assert x >= 0, 'x is less then zero' and better or worse then if x < 0: raise Exception, 'x is less then zero' Also, is there anyway to set a business rule like if x < 0 raise error that is always checked with out the try, except, finally so, if at anytime throughout the code x is < 0 an error is raised, like if you set assert x < 0 at the start of a function, anywhere within the function where x becomes less then 0 an exception is raised?

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• [C#] Async threaded tcp server

  - by mark_dj

  I want to create a high performance server in C# which could take about ~10k clients. Now i started writing a TcpServer with C# and for each client-connection i open a new thread. I also use one thread to accept the connections. So far so good, works fine. The server has to deserialize AMF incoming objects do some logic ( like saving the position of a player ) and send some object back ( serializing objects ). I am not worried about the serializing/deserializing part atm. My main concern is that I will have a lot of threads with 10k clients and i've read somewhere that an OS can only hold like a few hunderd threads. Are there any sources/articles available on writing a decent async threaded server ? Are there other possibilties or will 10k threads work fine ? I've looked on google, but i couldn't find much info about design patterns or ways which explain it clearly

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• How do I rename a field in a structure array in MATLAB?

  - by Matthew Simoneau

  Given a structure array, how do I rename a field? For example, given the following, how do I change "bar" to "baz". clear a(1).foo = 1; a(1).bar = 'one'; a(2).foo = 2; a(2).bar = 'two'; a(3).foo = 3; a(3).bar = 'three'; disp(a) What is the best method, where "best" is a balance of performance, clarity, and generality?

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• Loading a XML, but for asp.net 2.0

  - by Blankman

  I need to load an XML document into my Dictionary<string,string> object. XML looks like: <nodes> <node id="123"> <text>text goes here</text> </node> </nodes> How can I do this using XmlDocument? I want readability over performance, and I find XmlReader to be hard to read b/c you have to keep checking the node type.

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• PyPy -- How can it possibly beat CPython?

  - by Vulcan Eager

  From the Google Open Source Blog: PyPy is a reimplementation of Python in Python, using advanced techniques to try to attain better performance than CPython. Many years of hard work have finally paid off. Our speed results often beat CPython, ranging from being slightly slower, to speedups of up to 2x on real application code, to speedups of up to 10x on small benchmarks. How is this possible? Which Python implementation was used to implement PyPy? CPython? And what are the chances of a PyPyPy or PyPyPyPy beating their score? (On a related note... why would anyone try something like this?)

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• General zoom algorithm for drawing program

  - by Steven Sproat

  My GUI toolkit, wxPython provides some methods for implementing a user zoom factor, however the quality isn't too good. I'm looking for ideas on how to create a zooming feature, which I know is complicated. I have a bitmap representing my canvas which is drawn to. This is displayed inside a scrolled window. Problems I forsee: - performance when zoomed in and panning around the canvas - difficulties with "real" coordinates and zoomed in coordinates - image quality not degrading with the zoom Using wxPython's SetUserScale() on its device contexts presents image quality like this - this is with a 1px line, at 30% zoomed in. I'm just wondering the general steps I'll need to take and the challenges I'll encounter. Thanks for any suggestions

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• What messaging technologies in windows-ce for guaranteed msg delivery?

  - by Aidanapword

  We are building a windows-ce (6.0R3) based device that requires guaranteed and audit-ready message delivery (including store & forward) up to and down from the cloud. I have been looking for choices beyond: MSMQ a proprietary solution (what our prototype device is using) AMQP (I have not found any RabbitMQ clients for CE, by example) ... are there any others? We will be transporting sensitive data (who isn't?!?!) over a public network, and large scale options are required. Anything running on an embedded device will be performance sensitive too.

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• how to implement unitofwork pattern when using subsonic 2.1(Repository pattern) ?

  - by ROHITH

  I am using subsonic repository pattern(2.1) for asp.net mvc application.In my application,there are many repositories like categoryRepository,Blogrepository etc.Inside each of this repository i am calling subsonic's DB.Select().From()...ExecuteReader() and then loading domain objects from those reader. In the controller action i make multiple calls from these repositories for e.g. List<IBlog> blogs=_blogRepository.GetHottestBlogs(); List<ICategory> categories=_categoryRepository.GetAll(); do i have to implement any unitofwork pattern for this ?.My doubt is that how subsonic performs each operation DB.Update/Insert/Select .Is a TransactionScope is enough for batch update or do i have to use SharedDbConnectionScope to get better performance?

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• How to save objects using Multi-Threading in Core Data?

  - by Konstantin

  I'm getting some data from the web service and saving it in the core data. This workflow looks like this: get xml feed go over every item in that feed, create a new ManagedObject for every feed item download some big binary data for every item and save it into ManagedObject call [managedObjectContext save:] Now, the problem is of course the performance - everything runs on the main thread. I'd like to re-factor as much as possible to another thread, but I'm not sure where I should start. Is it OK to put everything (1-4) to the separate thread?

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• Java multiline string

  - by skiphoppy

  Coming from Perl, I sure am missing the "here-document" means of creating a multi-line string in source code: $string = <<"EOF" # create a three line string text text text EOF In Java I have to have cumbersome quotes and plus signs on every line as I concatenate my multiline string from scratch. What are some better alternatives? Define my string in a properties file? Edit: Two answers say StringBuilder.append() is preferable to the plus notation. Could anyone elaborate as to why they think so? It doesn't look more preferable to me at all. I'm looking for away around the fact that multiline strings are not a first-class language construct, which means I definitely don't want to replace a first-class language construct (string concatenation with plus) with method calls. Edit: To clarify my question further, I'm not concerned about performance at all. I'm concerned about maintainability and design issues.

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• How do you handle large repeated UI elements with JQuery

  - by jpoz

  Howdy, Here's the situation: You have a very complex UI element that is repeated in a list. Each has a menu on it, buttons, it hides and shows subelements, buttons for switch it's state, etc, etc. The elements are populated via JSON so you have to construct the elements and the functionality of the fly. What's the best way to accomplish this with JQuery? Where would you save the reusable template for the DOM structure? How would you add the behavior on? $().live? .livequery? onclick? manual after every JSON get? I guess I just see a lot of people doing different things. What's your experience with performance? Any insight would be much appreciated. Thanks, JPoz

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