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  • Does Python Django support custom SQL and denormalized databases with no Foreign Key relationships?

    - by Jay
    I've just started learning Python Django and have a lot of experience building high traffic websites using PHP and MySQL. What worries me so far is Python's overly optimistic approach that you will never need to write custom SQL and that it automatically creates all these Foreign Key relationships in your database. The one thing I've learned in the last few years of building Chess.com is that its impossible to NOT write custom SQL when you're dealing with something like MySQL that frequently needs to be told what indexes it should use (or avoid), and that Foreign Keys are a death sentence. Percona's strongest recommendation was for us to remove all FKs for optimal performance. Is there a way in Django to do this in the models file? create relationships without creating actual DB FKs? Or is there a way to start at the database level, design/create my database, and then have Django reverse engineer the models file?

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  • when to use StringBuilder in java

    - by kostja
    It is supposed to be generally preferable to use a StringBuilder for String concatenation in Java. Is it always the case? What i mean is : Is the overhead of creating a StringBuilder object, calling the append() method and finally toString() smaller then concatenating existing Strings with + for 2 Strings already or is it only advisable for more Strings? If there is such a threshold, what does it depend on (the String length i suppose, but in which way)? And finally - would you trade the readability and conciseness of the + concatenation for the performance of the StringBuilder in smaller cases like 2, 3, 4 Strings?

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  • How to display label of unnamed drive ?

    - by iira
    I want to get the name or label of drive. I use this function : function GetVolumeLabel(DriveChar: Char): string; var NotUsed: DWORD; VolumeFlags: DWORD; VolumeInfo: array[0..MAX_PATH] of Char; VolumeSerialNumber: DWORD; Buf: array [0..MAX_PATH] of Char; begin GetVolumeInformation(PChar(DriveChar + ':\'), Buf, SizeOf(VolumeInfo), @VolumeSerialNumber, NotUsed, VolumeFlags, nil, 0); SetString(Result, Buf, StrLen(Buf)); { Set return result } Result:=AnsiUpperCase(Result) end; For example, here're my drives in Windows Explorer : Local Disk (C:) Data (D:) DVD RW Drive (E:) The output of the code : C: D: DATA E: The labels of C and E are empty. What winapi/function should I use to display the label of unnamed drive (C and E)?

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  • Gen folder disappearing in Eclipse Android project

    - by Adam Haile
    I'm just getting started developing for Android and I'm running into a weird problem. First off, I'm running Eclipse for Java devs v3.5.2 with the Android 2.1 SDK installed. Basically, whenever I do just about anything the "gen" (R.java, etc.) folder will just disappear from the project. I'm seen some people online say that it was still on the drive, just gone from the project listing in Eclipse, but in my case it is literally and completely gone. The only fix I've found is that if I refresh, then try to build, it gives an error and "gen" shows up in the project view (though it's not on the disk), then delete it from within the project, then Rebuild All and it will say that it cannot find it and is recreating it. Problem is, I have to do this every single time I want to build. There's got to be a fix for this.

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  • How can i convert between F# List and F# Tuple?

    - by ksharp
    Is there some way to convert between F# List and F# Tuple? For example: [1;2;3] -> (1,2,3) (1,2,3,4) -> [1;2;3;4] I need two Functions to do that: let listToTuple list = ... let tupleToList tuple = ... Thank you in advance. I think reflection is necessary to this problem. I know the performance is not good. I have to pay the cost of breaking functional programming rule.

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  • fast on-demand c++ compilation [closed]

    - by Amit Prakash
    I'm looking at the possibility of building a system where when a query hits the server, we turn the query into c++ code, compile it as shared object and the run the code. The time for compilation itself needs to be small for it to be worthwhile. My code can generate the corresponding c++ code but if I have to write it out on disk and then invoke gcc to get a .so file and then run it, it does not seem to be worth it. Are there ways in which I can get a small snippet of code to compile and be ready as a share object fast (can have a significant start up time before the queries arrive). If such a tool has a permissive license thats a further plus. Edit: I have a very restrictive query language that the users can use so the security threat is not relevant. My own code translates the query into c++ code. The answer mentioning clang is perfect.

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  • Ternary operators and variable reassignment in PHP

    - by TomcatExodus
    I've perused the questions on ternary operators vs. if/else structures, and while I understand that under normal circumstances there is no performance loss/gain in using ternary operators over if/else structures, I've not seen any mention of this situation. Language specific to PHP (but any language agnostic details are welcome) does the interpreter reassign values in situations like this: $foo = 'bar' $foo = strlen($foo) > 3 ? substr($foo, 0, 3) : $foo; Since this would evaluate to $foo = $foo; is this inefficient, or does the interpreter simply overlook/discard this evaluation? On a side note, what about: !defined('SECURE') ? exit : null;

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  • What FIX implementation do you recommend for use with .NET

    - by Ajaxx
    I am reviewing implementation choices for FIX when using .NET. A few obvious choices come to mind, but I want to know if there are other options, better choices or if we've made the same decision as a lot of you. QuickFIX - Stable, C++ implementation - so you've got unmanaged code to interop with. FIX4NET - C# implementation - seems to have some gaps in its implementation. DIY - Chime in here if you've made your own FIX engine Let me throw in some caveats here. I'm not looking for sub 100 microsecond processing. Performance is a requirement, but not so much that it's driving my decisions. A solid product that is stable, performs well and is flexible enough to deal with vendor specific dialects is the sweet spot. The more we can do in .NET the better.

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  • how to pass in a reference to a string in javascript?

    - by ijjo
    maybe a closure is my solution? not exactly sure how to pull it off though. the code is set up like so: var globalVar = ''; var globalVar2 = ''; function func() { if (condition) func2(globalVar) else func2(globalVar2) } in func2() i cache some HTML in a main container into the appropriate global variable that i pass to it. basically i have a main container that holds different pages depending on what tab they choose. for performance i want to cache the page into global vars so i need to know what tab is active to figure out which global var to assign the html to.

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  • Android add image to button

    - by Christiaan de Jong
    I want to add an image to a Button (no imagebutton, as the particular button can either contain text or an image; plus the imagebutton has the same problem), while still retaining the original android-style button. So adding android:background in the XML doesn't cut it, as that will remove the android default button with rounded corners etc. (android.R.drawable.btn_default) Is this in any way possible? I think one way is to make a 9patch image for the button pressed (one for up and one for down) and onTouch Action_DOWN make a layered background drawable and put that onto the button, and doing the same thing but with another 9patch for onTouch Action_UP, but I think that will decrease the performance of the application substantially, as that will require quite a lot of resource reading and layer merging for all the button clicks (and for my application, that will be quite a lot). Is what I state above correct?

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  • Play a video with flash (with no controls, pause, etc) and stretch to full width and height of page.

    - by Tim
    Hi, I've managed this so far: [removed url] The plan is to have that video stretch across the whole page (the flash does, the video itself does not). Firstly: well aware of the issues - bad performance, horribly stretched/pixelated video. I know this. However a client wants it so we have to do it, simple as that. Does anyone have any ideas on how this can be achieved? I've been in touch with the creators of the flash video player I'm currently using and they've confirmed it isn't possible with that flash video player. Anyone know of any players where it is possible? Thanks, Tim

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  • How to handle images folder with many images

    - by Billy
    I'm developing a new aspnet website with 200k images in a /Images/ -folder. Many operations in Visual Studio is slow because it access the folder, adding a web service takes 10 minutes. The images is not checked into scm (svn). How should I structure the tree of code, to improve performance in VS? It would also be neat if not all developers needed to copy 200k images to their local disk to be able to develop on the site. Images as DB blobs is not an option.

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  • A 110 kb .NET 4.0 app needs 10 seconds for a cold start, thats not acceptable !

    - by msfanboy
    Hello, I am using the .NET 4.0 client profile for my app and I run a dual core with 4 GB Ram and a fast hard disk. nothing big is done at the start just showing a generic List in a wpf listview. How can I make the cold start faster of my assembly ? I have done now again a cold start and run the windowsapplication.exe in my \obj\x86\Debug folder and my harddisk run like hell and it took 10,5 seconds ??? What is wrong? The warm start after the cold one took 1 second. Java 6 apps has not that problem, not at all just to compare...

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  • Is there a library / tool to query MySQL data files (MyISAM / InnoDB) without the server? (the SQLit

    - by MGW
    Oftentimes I want to query my MySQL data directly without a server running or without having access to the server (but having read / write rights to the files). Is there a tool or maybe even a library around to query MySQL data files like it is possible with SQLite? I'm specifically looking for InnoDB and MyISAM support. Performance is not a factor. I don't have any knowledge about MySQL internals, but I presume it should be possible to do and not too hard to get the specific code out? Thank you for any suggestions!

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  • What are some Servlet Container pros and cons for a Solr installation?

    - by danieltalsky
    The SolrInstall wiki page lists seven different server / Servlet Containers compatible with Solr: Tomcat Jetty Resin JBoss WebSphere Weblogic Glassfish I'm sure that "best" is subjective, so I'll just say my criteria are: easiest to set up, best for search performance with a smallish, infrequently-updated dataset, and with the fewest number of gotchas. Jetty and Tomcat both have apt-get solr packages, so they're clearly the frontrunners for some. Jetty is used in the demo install, but there's some notes that Jetty has some difficulties handling Unicode in some cases. Tomcat is a common choice but my understanding is that it's not as lightweight and has a lot of features not needed by Solr. Is it worth considering any of the others? Are there some important pro's and cons I should be aware of?

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  • sharpziplib - can you add a file without it copying the entire zip first?

    - by schmoopy
    Im trying to add an existing file to a .zip file using sharpziplib - problem is, the zip file is 1GB in size. When i try to add 1 small file (400k) sharpziplib creates a copy/temp of the orig zip file before adding the new file - this poses a problem when the amount of free disk space is less than 2x the zip file you are trying to update. for example: 1GB zip myfile.zip 1GB zip myfile.zip.tmp.293 ZipFile zf = new ZipFile(path); zf.BeginUpdate(); zf.Add(file); // Adding a 400k file here causes a 1GB temp file to be created zf.EndUpdate(); zf.Close(); Is there a more efficient way to do this? Thanks :-)

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  • Stored Procedure or calculations via IQueryable?

    - by Shawn Mclean
    This is a question that is based on choosing performance over design practices. If I have a method that will be executed many times a second; public static IQueryable<IPerson> InRadius(this IQueryable<IPerson> query, Coordinate center, double radius) { return (from u in query where CallHeavyMathFormula(u, center, radius) select u); } This extension method for IQueryable generates a SQL that does some heavy maths calculation (Cosine, Sine, etc). This would mean the application sends 1-2KB of sql to the server per call. I've heard of placing all application logic, in your application. I also would like to change to a database such as azure or one of those scalable databases in the future. How do I handle something like this? Should I leave it as it is now or write stored procedures? How do applications like twitter or facebook do it?

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  • Oracle Triggers Query..

    - by AGeek
    Lets consider a Table STUD and a ROW-Level TRIGGER is implemented over INSERT query.. My scenario goes like this, whenever a row is inserted, a trigger is fired and it should access some script file which is placed in the hard disk, and ultimately should print the result. So, is this thing is possible? and if yes, then this thing should exist in dynamic form, i.e. if we change the content of script file, then the oracle should reflect those changes as well. I have tried doing this for java using External Procedures, but doesn't feel that much satisfied with the result that i wanted. Kindly give your point-of-view for this kind of scenario and ways that this can be implemented.

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  • Django: How do I go about changing my simple app to use Ajax?

    - by swisstony
    I currently have a web page where the user enters some data and then clicks a submit button. I process the data in views.py and then use the same Django template to return and display the original data and the results. What I would like to do is try to give it a bit more of a modern look and feel. You know the sort of thing, the page doesn't refresh but displays a spinning disk until the results are displayed. I assume this means using Ajax? How difficult is it to modify a simple app like this to use Ajax? What is involved? What are the best tools to use? JQuery?

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  • Virus - How much it can affect?

    - by Sarang
    In our daily life, we come across various Viruses. In this internet world, we do have lots of type of viruses come to visit us ! While for the beginners, Virus is a complicated matter to fight with. Please explain the way how the virus come flow across the PC using Internet. What are the ways to search for them in the Personal Computer ? Also, we do have various solutions available in the market of Anti-Viruses, but also have different comments available for different software. Which is actually, really a useful Anti-Virus in the market that can give reliable performance ? Every Personal Computer connected to internet has to face against the viruses. Isn't there any general solution using Internet itself through which all networked computers get protected against Viruses ? Please give any solution.

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  • Large Video Uploads via a website

    - by Andrew
    Some of the problems that can happen are timeouts, disconnections, and not being able to resume a file and having to start from the beginning. Assuming these files are up to around 5gigs in size, what is the best solution for dealing with this problem? I'm using a Drupal 6 install for the website. Some of my constraints due to the server setup I have to deal with: Shared hosting with max 200 connections at a time (unlimited disk space) Shared hosting. Unable to create users through an API (so can't automatically generate ftp accounts) I do have the ability to run cron-type scripts via a Drupal module. My initial thought was to create ftp users based off of Drupal accounts and requiring them to download an ftp client for their OS of choice. But the lack of API to auto-create ftp accounts and the inability to do it from command line kind of hinder that solution. If there's a workaround someone can think of, let me know! Thanks

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  • iPhone App takes up too much memory

    - by Stephen Furlani
    Ok, so here's my problem. My iPhone app is 1.2MB on disk. Granted I have a bunch of Images for the GUI buttons and backgrounds, etc. In-memory, my app takes up a whopping 15MB! That means if I then take a picture with the camera, 8MB default, it gives a memory warning (several) even before the picker calls its delegate! How can I tell what is grabbing so much memory, and how to remove it? I've removed all of my debugging symbols and added [-Os], but it still takes up a huge amount of memory! Also, (how) can I change the default resolution of the camera?

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  • Is select() Ok to implement single socket read/write timeout ?

    - by chmike
    I have an application processing network communication with blocking calls. Each thread manages a single connection. I've added a timeout on the read and write operation by using select prior to read or write on the socket. Select is known to be inefficient when dealing with large number of sockets. But is it ok, in term of performance to use it with a single socket or are there more efficient methods to add timeout support on single sockets calls ? The benefit of select is to be portable.

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  • (NOT) NULL for NVARCHAR columns

    - by Anders Abel
    Allowing NULL values on a column is normally done to allow the absense of a value to be represented. When using NVARCHAR there is aldready a possibility to have an empty string, without setting the column to NULL. In most cases I cannot see a semantical difference between an NVARCHAR with an empty string and a NULL value for such a column. Setting the column as NOT NULL saves me from having to deal with the possibility of NULL values in the code and it feels better to not have to different representations of "no value" (NULL or an empty string). Will I run into any other problems by setting my NVARCHAR columns to NOT NULL. Performance? Storage size? Anything I've overlooked on the usage of the values in the client code?

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  • MEMORY(HEAP) vs. InnoDB in a Read and Write Envirnment

    - by Johannes
    I want to programm a real-time application using MySQL. It needs a small table (less than 10000 rows) that will be under heavy read (scan) and write (update and some insert/delete) load. I am really speaking of 10000 updates or selects per second. These statements will be executed on only a few (less than 10) open mysql connections. The table is small and does not contain any data that needs to be stored on disk. So I ask which is faster: InnoDB or MEMORY (HEAP)? My thoughts are: Both enginges will probably serve SELECTs directly from memory, as even InnoDB will cache the whole table. What about the UPDATAEs? (innodb_flush_log_at_trx_commit?) My main concern is the locking behavior: InnoDB row lock vs. MEMORY table lock. Will this present the bottleneck in the MEMORY implementation? Thanks for your thoughts!

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