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• PostgreSQL: How to index all foreign keys?

  - by biggusjimmus

  I am working with a large PostgreSQL database, and I are trying to tune it to get more performance. Our queries and updates seem to be doing a lot of lookups using foreign keys. What I would like is a relatively simple way to add Indexes to all of our foreign keys without having to go through every table (~140) and doing it manually. In researching this, I've come to find that there is no way to have Postgres do this for you automatically (like MySQL does), but I would be happy to hear otherwise there, too.

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• code-style: Is inline initialization of JS objects ok?

  - by michael

  I often find myself using inline initialization (see example below), especially in a switch statement when I don't know which case loop will hit. I find it easier to read than if statements. But is this good practice or will it incur side-effects or a performance hit? for (var i in array) { var o = o ? o : {}; // init object if it doesn't exist o[array[i]] = 1; // add key-values } Is there a good website to go to get coding style tips?

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• Mysql query taking too much time

  - by aditya

  I have problem related to mysql database. i am linux webserver admin and i am facing a problem with a mysql query. The database is very small. I tried to track in logs and found that a query is taking minimum 5 sec to respond . The first page of site is coming from the database. Client are using cms. when the server gets some number of hits database server starts to give response very slowly and wait time increases from 5 sec to several seconds. I checked slow query logs { Query_time: 11.480138 Lock_time: 0.003837 Rows_sent: 921 Rows_examined: 3333 SET timestamp=1346656767; SELECT `Tender`.`id`, `Tender`.`department_id`, `Tender`.`title_english`, `Tender`.`content_english`, `Tender`.`title_hindi`, `Tender`.`content_hindi`, `Tender`.`file_name`, `Tender`.`start_publish`, `Tender`.`end_publish`, `Tender`.`publish`, `Tender`.`status`, `Tender`.`createdBy`, `Tender`.`created`, `Tender`.`modifyBy`, `Tender`.`modified` FROM `mcms_tenders` AS `Tender` WHERE `Tender`.`department_id` IN ( 31, 33, 32, 30 ); } Every line in the log is same only there is diff in Query time. Is there any way tweak the performance?

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• Interview Question: .Any() vs if (.Length > 0) for testing if a collection has elements

  - by Chris

  In a recent interview I was asked what the difference between .Any() and .Length > 0 was and why I would use either when testing to see if a collection had elements. This threw me a little as it seems a little obvious but feel I may be missing something. I suggested that you use .Length when you simply need to know that a collection has elements and .Any() when you wish to filter the results. Presumably .Any() takes a performance hit too as it has to do a loop / query internally.

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• How to correct this glitch

  - by Rebol Tutorial

  I removed background: url(none); in my stylesheet because of load performance http://stackoverflow.com/questions/2577422/why-firebug-pretends-that-my-stylesheet-is-calling-my-xmlrpc The problem is that it now causes some glitch on css list. Any idea how to fix this ? Thanks. Update: picture below Tried to put background: none as suggested but didn't solve the problem/ ul.sidebar_list li ul li ul { margin: 0px; padding: 0px!important; float: left; width: 100%; list-style-type: none; background: none; }

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• how do copyright permission systems for content hosting sites work?

  - by zebraman

  I am wondering about subscription sites that host content, like recorded performances from concerts. I'm sure there is a tangle of copyright permissions that must be granted for these video/audio files to be hosted. For example, if a band plays a cover of another band's song, permission must be obtained from not only the band that performed, but the band that owns the song. Perhaps even from the venue that hosted the performance, to record the video and post the content. I am curious how websites that host content like this work. How might an automated copyright system work to keep track of who has ownership of certain performances and obtain permission from said owners to record and post their content.

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• entity framework and dirty reads

  - by bryanjonker

  I have Entity Framework (.NET 4.0) going against SQL Server 2008. The database is (theoretically) getting updated during business hours -- delete, then insert, all through a transaction. Practically, it's not going to happen that often. But, I need to make sure I can always read data in the database. The application I'm writing will never do any types of writes to the data -- read-only. If I do a dirty read, I can always access the data; the worst that happens is I get old data (which is acceptable). However, can I tell Entity Framework to always use dirty reads? Are there performance or data integrity issues I need to worry about if I set up EF this way? Or should I take a step back and see about rewriting the process that's doing the delete/insert process?

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• assignment vs std::swap and merging and keeping duplicates in seperate object

  - by rubenvb

  Say I have two std::set<std::string>s. The first one, old_options, needs to be merged with additional options, contained in new_options. I can't just use std::merge (well, I do, but not only that) because I also check for doubles and warn the user about this accordingly. To this effect, I have void merge_options( set<string> &old_options, const set<string> &new_options ) { // find duplicates and create merged_options, a stringset containing the merged options // handle duplicated the way I want to // ... old_options = merged_options; } Is it better to use std::swap( merged_options, old_options ); or the assignment I have? Is there a better way to filter duplicates and return the merged set than consecutive calls to std::set_intersection and std::set_union to detect dupes and merge the sets? I know it's slower than one traversal and doing both at once, but these sets are small (performance is not critical) and I trust the Standard more than I trust myself.

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• Is there an additional runtime cost for using named parameters?

  - by Jurily

  Consider the following struct: public struct vip { string email; string name; int category; public vip(string email, int category, string name = "") { this.email = email; this.name = name; this.category = category; } } Is there a performance difference between the following two calls? var e = new vip(email: "foo", name: "bar", category: 32); var e = new vip("foo", 32, "bar"); Is there a difference if there are no optional parameters defined?

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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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• How to implement square root and exponentiation on arbitrary length numbers?

  - by tomp

  I'm working on new data type for arbitrary length numbers (only non-negative integers) and I got stuck at implementing square root and exponentiation functions (only for natural exponents). Please help. I store the arbitrary length number as a string, so all operations are made char by char. Please don't include advices to use different (existing) library or other way to store the number than string. It's meant to be a programming exercise, not a real-world application, so optimization and performance are not so necessary. If you include code in your answer, I would prefer it to be in either pseudo-code or in C++. The important thing is the algorithm, not the implementation itself. Thanks for the help.

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• Multimedia content in REST responce(XML/JSON)

  - by Koushik

  In my thesis I need to test different architectures. A request to a REST web service developed using Apache CXF and Spring MVC with MySQL as back end serving references(a field in database) to images,audio and video files stored in file system. In the response message, what is the best method to send the content to the client(another application using the service which I developed). URI: http://www.filmservices.com/film/{id} A client here is not the end user. Send the encoded hyperlink's(where the content is stored in the file system) to the client, so that the client renders the response and displays it to the browser. Use Base64 to encode the message(image,audio,video) and send it to the client. Main concern is performance.

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• Java data structure to use with Hibernate to store unknown number of parameters?

  - by Lunikon

  Following problem: I want to render a news stream of short messages based on localized texts. In various places of these messages I have to insert parameters to "customize" them. I guess you know what I mean ;) My question probably falls into the "Which is the best style to do it?" category: How would you store these parameters (they may be Strings and Numbers that need to be formatted according to Locale) in the database? I'm using Hibernate to do the ORM and I can think of the following solutions: build a combined String and save it as such (ugly and hard to maintain I think) do some kind of fancy normalization and and make every parameter a single row on the database (clean I guess, but a performance nightmare) Put the params into an Array, Map or other Java data structure and save it in binary format (probably causes a lot of overhead size-wise) I tend towards option #3 but I'm afraid that it might be to costly in terms of size in the database. What do you think?

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• Dealing with Windows line-endings in Python

  - by Adam Nelson

  I've got a 700MB XML file coming from a Windows provider. As one might expect, the line endings are '\r\n' (or ^M in vi). What is the most efficient way to deal with this situation aside from getting the supplier to send over '\n' :-) Use os.linesep Use rstrip() (requiring opening the file ... which seems crazy) Using Universal newline support is not standard on my Mac Snow Leopard - so isn't an option. I'm open to anything that requires Python 2.6+ but it needs to work on Snow Leopard and Ubuntu 9.10 with minimal external requirements. I don't mind a small performance penalty but I am looking for the standard best way to deal with this.

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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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• SSIS - Connection Management Within a Loop

  - by Rob Bowman

  Hi I have the following SSIS package: The problem is that within the Foreach loop a connection is opened and closed for each iteration. On running SQL Profiler I see a series of: Audit Login RPC:Completed Audit Lout The duration for the login and the RPC that actually does the work is minimal. However, the duration for the logout is significant, running into several seconds each. This causes the JOB to run very slowly - taking many hours. I get the same problem when running either on a test server or stand-alone laptop. Could anyone please suggest how I may change the package to improve performance? Also, I have noticed that when running the package from Visual Studio, it looks as though it continues to run with the component blocks going amber then green but actually all the processing has been completed and SQL profiler has dropped silent? Thanks, Rob.

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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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• Is it really wrong to version documents using CouchDB's behaviour?

  - by Tomas Sedovic

  This is one of those "I know I shouldn't do this but it's oh so convenient." questions. Sorry about that. I plan to use CouchDB for storing a bunch of documents and keeping their entire revision history. CouchDB does the versioning automatically, but it is strongly discouraged for programmer's use: "You cannot rely on document revisions for any other purpose than concurrency control." From what I've found on the CouchDB wiki, the versions can get deleted either during compaction or during replication. As far as I can tell, Compaction must always be triggered manually and Replication occurs only when there's more than one database server. The question is: if I won't run compaction and will use only single database instance for my documents, can I just use CouchDB's document versioning and expect it to work? What other problems I might run into? E.g. does not running compaction hurt the performance or consume significantly more disk space (than if I did handle the versioning manually)?

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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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• Managing Data Prefetching and Dependencies with .NET Typed Datasets

  - by Derek Morrison

  I'm using .NET typed datasets on a project, and I often get into situations where I prefetch data from several tables into a dataset and then pass that dataset to several methods for processing. It seems cleaner to let each method decide exactly which data it needs and then load the data itself. However, several of the methods work with the same data, and I want the performance benefit of loading data in the beginning only once. My problem is that I don't know of a good way or pattern to use for managing dependencies (I want to be sure I load all the data that I'm going to need for each class/method that will use the dataset). Currently, I just end up looking through the code for the various classes that will use the dataset to make sure I'm loading everything appropriately. What are good approaches or patterns to use in this situation? Am I doing something fundamentally wrong? Although I'm using typed datasets, this seems like it would be a common situation where prefetching data is used. Thanks!

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• parsing/matching string occurrence in C

  - by David

  I have the following string: const char *str = "\"This is just some random text\" 130 28194 \"Some other string\" \"String 3\"" I would like to get the the integer 28194 of course the integer varies, so I can't do strstr("20194"). So I was wondering what would be a good way to get that part of the string? I was thinking to use #include <regex.h> which I already have a procedure to match regexp's but not sure how the regexp in C will look like using the POSIX style notation. [:alpha:]+[:digit:] and if performance will be an issue. Or will it be better using strchr,strstr? Any ideas will be appreciate it

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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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• Conceptually, how does replay work in a game?

  - by SnOrfus

  I was kind of curious as to how replay might be implemented in a game. Initially, I thought that there would be just a command list of every player/ai action that was taken in the game, and it then 're-plays' the game and lets the engine render as usual. However, I have looked at replays in FPS/RTS games, and upon careful inspection even things like the particles and graphical/audible glitches are consistent (and those glitches are generally *in*consistent). So How does this happen. In fixed camera angle games I though it might just write every frame of the whole scene to a stream that gets stored and then just replays the stream back, but that doesn't seem like enough for games that allow you to pause and move the camera around. You'd have to store the locations of everything in the scene at all points in time (No?). So for things like particles, that's a lot of data to push which seems like a significant draw on the game's performance whilst playing.

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• Best way to store chat messages and files

  - by Stnaire

  I would like to know what do you think about storing chat messages in a database? I need to be able to bind other stuff to them (like files, or contacts) and using a database is the best way I see for now. The same question comes for files, because they can be bound to chat messages, I have to store them in the database too.. With thousands of messages and files I wonder about performance drops and database size. What do you think considering I'm using PHP with MySQL/Doctrine?

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• How to update only certain items in a list when using MVC?

  - by Eugen

  I'm building a GUI that includes a list with quite a lot of items. I allow the user to add/delete/edit those items. Up until now my update method called in the controller implied an entire JList reset (with its obvious performance issues). Now that there are hundreds of items available, updating the entire list is not fezable any longer. Does anyone know of a tutorial or can share an example (I haven't found any to suit my needs so far) in which the JList is updated something like JList.update(startIndex, endIndex);? Thanks for taking the time to answer.

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