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• MySQL indexes - what are the best practises?

  - by Haroldo

  I've been using indexes on my mysql databases for a while now but never properly learnt about them. Generally I put an index on any fields that i will be searching or selecting using a WHERE clause but sometimes it doesn't seem so black and white. What are the best practises for mysql indexes? example situations/dilemas: If a table has six columns and all of them are searchable, should i index all of them or none of them? . What are the negetive performance impacts of indexing? . If i have a VARCHAR 2500 column which is searchable from parts of my site, should i index it?

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• When we should use NSThreads in a cocoa Touch ?

  - by srikanth rongali

  I am writing a small game by using cocos2d. It is a shooting game. Player on one side and enemy on other side. To run the both actions of player shooting and enemy shooting do we should use threads ? Or can we do without using them. At present I am not using threads. But I can manage to do both actions of player and enemy at same time. Should I use threads compulsory good performance ? Or am I doing wrong without using threads ? Please help me from this confusion. Thank you.

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• Which is more efficent PHP: array_intersect() OR array_intersect_key()

  - by Jordan Rutty

  Is it more efficient to use the key intersect or the value intersect if both key and value have the same contents for example: Array ( [743] => 743 [744] => 744 [745] => 745 [746] => 746 [747] => 747 [748] => 748 ) Is there any difference in performance in using one or the other with the same values. Similar to the difference of using double or single quotes?

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• how to handle db concurrency in client-server application in C#?

  - by RAJ K

  I am developing an application in C# WPF which will have Client-Server architecture (Client will do products sales billing). I am novice in this area and I asked this question to start my development process. Click here to view question. So, ultimately I have selected MySQl, WCf & WPF. Now I have one silly question. Do i need to handle DB concurrency explicitly in my application (like 3 clients inserting data same time) or MySQl will handle this without any conflict? To accomplish my project i thought, I will create a service in WCf which will do DB queries from client application. Do you have any suggestion to improve my application performance.

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• Phonegap and JqueryMobile freeze UI events and functions

  - by techytee

  I am developing a Phonegap app with JQuery mobile with their latest stable versinos (Phonegap 3 and JQM 1.3.2) for Android platform. My app downloads feeds from Google Feeds API and saves in a SQLite database. But whenever it starts fetching and saving data from the web (the no of feeds that download at a time can be many), the other functionality such as button events halt and freeze. To be precise the a button that opens and closes a panel does not either open or close the panel until the data fetching stops. How am I supposed to solve this issue? The performance has dropped drastically due to this issue in my app.

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• JS Framework that doesn't use CSS selectors?

  - by RoToRa

  A thing that I noticed about most JavaScript frameworks is that the most common way to find/access the DOM elements is to use CSS selectors. However this usually requires the framework to include a CSS selector parser, because they need to support selectors, that the browser natively doesn't, foremost the frameworks own proprietary extensions. I would think that these parsers are large and slow. Wouldn't it be more efficient to have something that doesn't require a parser, such a chained method calls? Some like: id("example").children().class("test").hasAttribute("href") instead of $("#example > .test[href]") Are there any frameworks around that do something like this? And how do they compare with jQuery and friends in regard to performance and size? EDIT: You can consider this a theoretical discussion topic. I don't plan to use anything other than jQuery in any practical projects in near furure. I was just wondering why there aren't any other, possibly better approaches.

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• Examples of both beautiful and ugly java code?

  - by tputkonen

  I would like to demonstrate how difficult it is for a layman to identify high quality code from flawed code. I'm thinking of doing this with the help of two java methods. Both of the methods should look like they do the same, pretty simple thing. However one of them should have several kind of flaws, for example: iteration with array off by one error string concatenations causing lots of objects to be created (as opposed to StringBuffer in the "good" code, which looks more complicated) possibly null pointer exception (but it should not be trivial to spot) Those are just some examples, all kinds of other issues including bugs and performance related structures are highly appreciated. Methods should be around 10-20 lines of length, and the task they do should be something simple - preferably printing something in an iteration.

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• Collection type generated by for with yield

  - by Jesper

  When I evaluate a for in Scala, I get an immutable IndexedSeq (a collection with array-like performance characteristics, such as efficient random access): scala> val s = for (i <- 0 to 9) yield math.random + i s: scala.collection.immutable.IndexedSeq[Double] = Vector(0.6127056766832756, 1.7137598183155291, ... Does a for with a yield always return an IndexedSeq, or can it also return some other type of collection class (a LinearSeq, for example)? If it can also return something else, then what determines the return type, and how can I influence it? I'm using Scala 2.8.0.RC3.

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• hibernate distributed 2nd level cache options

  - by ishmeister

  Not really a question but I'm looking for comments/suggestions from anyone who has experiences using one or more of the following: EhCache with RMI EhCache with JGroups EhCache with Terracotta Gigaspaces Data Grid A bit of background: our applications is read only for the most part but there is some user data that is read-write and some that is only written (and can also be reasonably inaccurate). In addition, it would be nice to have tools that enable us to flush and fill the cache at intervals or by admin intervention. Regarding the first option - are there any concerns about the overhead of RMI and performance of Java serialization?

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• JSF Pages call ManagedBeans that are not defined on the page and call all getters sometimes more tha

  - by Bill Leeper

  I have several JSF pages that are initializing and accessing ManagedBeans that are not even used on that page. This is creating a really hairy problem for initialization. I either have to make them all session scope and continually make calls to re-inialize or take the performance hit of having them read large amounts of data from the DB whenever they decide to initialize. Some of the managed beans being accessed are not even defined on the page in question. I have done some optimization based on comments related to multiple calls to getters, but I still have the issue that I have a very specialized (and expensive to initialize) bean that is getting called when I don't want it initialized. Any insight into why/what JSF calls might do something like this. I have a very complex page making use of JSTL, Tomahawk and standard JSF tags. I could include code, but its very complex and sensitive in nature.

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• Linq to SQL and Realtime Data

  - by Jeremy

  I have an application that needs to constantly (every 50ms), call to an MVC action, and pickup/drop off data. I am using Linq to SQL and MVC because of how simple they are to implement, and I know that they aren't perfect when it comes to performance, but it works relatively well, but the best speed I can get with my current approach is 200ms (without requests overlapping). Each call to the site will create a new instance of the datacontext, query/insert it and return that data. Is there a way to have the datacontext static, but submitchanges say every 5 seconds, so that i am pretty much hitting an in-memory version of the data?

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• conceptually different entities with a few similar properties should be stored in one table or more?

  - by Haghpanah

  Assume A and B are conceptually different entities that have a few similar properties and of course their own specific properties. In database design, should I put those two entities in one big aggregated table or two respectively designed tables. For instance, I have two types of payment; Online-payment and Manual-payment with following definition, TABLE [OnlinePayments] ( [ID] [uniqueidentifier], [UserID] [uniqueidentifier], [TrackingCode] [nvarchar](32), [ReferingCode] [nvarchar](32), [BankingAccID] [uniqueidentifier], [Status] [int], [Amount] [money], [Comments] [nvarchar](768), [CreatedAt] [datetime], [ShopingCartID] [uniqueidentifier], ) And TABLE [ManualPayments] ( [ID] [uniqueidentifier], [UserID] [uniqueidentifier], [BankingAccID] [uniqueidentifier], [BankingOrgID] [uniqueidentifier], [BranchName] [nvarchar](64), [BranchCode] [nvarchar](16), [Amount] [money], [SlipNumber] [nvarchar](64), [SlipImage] [image], [PaidAt] [datetime], [Comments] [nvarchar](768), [CreatedAt] [datetime], [IsApproved] [bit], [ApprovedByID] [uniqueidentifier], ) One of my friends told me that creating two distinct tables for such similar entities is not a well design method and they should be put in one single table for the sake of performance and ease of data manipulations. I’m now wondering what to do? What is the best practice in such a case?

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• how to protect an imported win32 dll into a .net application from memory issues

  - by Eric

  I have a c# application that needs to use a legacy win32 dll. The dll is almost its own app, it has dialogs, operations with hardware, etc. When this dll is imported and used, there are a couple of problems that occur: Dragging a dialog (not a windows system dialog, but one created by the dll) across the managed code app causes the UI to not repaint. Further it generates a system out of memory exception from various ui controls. The performance is incredibly slow. There seems to be no way to unload the dll so the memory never gets cleaned up. When we close our managed app, we get another memory exception. At the moment we import each method call as such: [DllImport("dllname.dll", EntryPoint = "MethodName", SetLastError = true, CharSet = CharSet.Auto, ExactSpelling = true, CallingConvention = CallingConvention.StdCall)]

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• ASP.NET Session StateServer - is it possible to extract info about current sessions?

  - by Moe Sisko

  I'm looking into changing the ASP.NET session state mode of our application from SQLServer to StateServer (for performance reasons). In SQLServer mode, it is easy to extract information about the current sessions by querying SQL Server tables like ASPStateTempSessions. e.g. things like when each session was created, when it is due to expire, etc. You could even query the session state blob data to extract further application specific info (e.g. like the UserID, if it was saved in session state). This info was useful for administrators. Just wondering if anyone has managed to do something similar for StateServer mode.

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• Question About Eclipse Java Debugger Conditional Breakpoints Inefficiency

  - by Personman

  I just set a conditional breakpoint in Eclipse's debugger with a mildly inefficient condition by breakpoint standards - checking whether a HashMap's value list (8 elements) contains Double.NaN. This resulted in an extremely noticeable slowdown in performance - after about five minutes, I gave up. Then I copy pasted the condition into an if statement at the exact same line, put a noop in the if, and set a normal breakpoint there. That breakpoint was reached in the expected 20-30 seconds. Is there something special that conditional breakpoints do that is different from this, or is Eclipse's implementation just kinda stupid? It seems like they could fairly easily just do exactly the same thing behind the scenes.

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• What's a good way to set up a development environment on OS X for ruby, rails, and git?

  - by Ein2015

  I'm going to start development on a web app using ruby, rails, probably either postgres or mysql, and most likely apache. I'll be using a git repository with the master repo on another server. I've searched through stackoverflow and done some Googling... so here's what I have so far... What are your opinions on what's described on this page?: http://robots.thoughtbot.com/post/159805668/2009-rubyists-guide-to-a-mac-os-x-development What about this one?: http://www.buildingwebapps.com/articles/79197-setting-up-rails-on-leopard-mac I don't need helping finding an editor, there's plenty out there (TextMate, TextWrangler, MacVim), but I do need help to make sure I'm setting things up correctly to code, build, and run the web app from my mac. Here's a specific set of scenarios I could use some help on: Testing various versions of rails and/or ruby. Testing performance, vulnerabilities, monitoring queries, etc. Testing different versions of gems. Working on other projects on this same machine.

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• Indexing XMLType columns

  - by Chris

  Hello, I am working with a XMLType and currently experiencing significant performance issues and would like to incorporate indexing to the column type. Currently I am taking the approach of using the XMLTable() and XQuery functions to create a virtual table. I would like to use this Virtual Table to create a function based index on the table containing the XMLType, but I am receiving this error: Error report: SQL Error: ORA-00907: missing right parenthesis 00907. 00000 - "missing right parenthesis" *Cause: *Action: This is the index.. any assistance would be greatly appreciated. CREATE INDEX indx_medicinalproduct ON d.ProductName XMLTable('for $i at $a in /safetyreport/patient//drug for $j in $i/medicinalproduct return element r { $i/medicinalproduct }' PASSING s.safetyreport COLUMNS ProductName varchar2(70) PATH 'medicinalproduct') d;

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• Is there any disadvantage to putting API code into a JAR along with the classes?

  - by Adam Gent

  In Java if you package the source code (.java) files into the jar along with classes (.class) most IDE's like eclipse will show the javadoc comments for code completion. IIRC there are few open-source projects that do this like JMock. Lets say I have cleanly separated my API code from implementation code so that I have something like myproject-api.jar and myproject-impl.jar is there any reason why I should not put the source code in my myproject-api.jar ? Because of Performance? Size? Why don't other projects do this?

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• Linq to SQL - design question.

  - by UshaP

  HI, Currently i have one big datacontex with 35 tables (i dragged all my DB tables to the designer). I must admit it is very comfortable cause i have ORM to my full DB and query with linq is easy and simple. My questions are: 1. Would you consider it bad design to have one datacontext with 35 tables or should i split it to logic units? 2. Is there any performance penalties for using such a big datacontext? Thanks, Pini.

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• Best choice for off-site backup: dd vs tar

  - by plok

  I have two 1TB single-partition hard disks configured as RAID1, of which I would like to make an off-site backup on a third disk, which I am still to buy. The idea is to store the backup at a relative's house, considerably far away from my place, in the hope that all the information will be safe in the case of a global thermonuclear apocalypse. Of course, this backup would be well encrypted. What I still have to decide is whether I am going to simply tar the entire partition or, instead, use dd to create an image of the disks. Is there any non-trivial difference between these two approaches that I could be overlooking? This off-site backup would be updated no more than two or three times a year, in the best of the cases, so performance should not be a factor to be pondered at all. What, and why, would you use if you were me? dd, tar, or a third option?

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• How can I force a subscriber to be synchronized from a local snapshot?

  - by Brian

  Hello, I have a SQL 2005 server replicating(merge\push) to SQL 2005 and SQL 2000 servers. I have multiple subscribers spread througout the United states. I have set , @snapshot_in_defaultfolder = N'false', @alt_snapshot_folder = N'c:\snapshots\Merge\' (sample location). I take the snapshot from the publisher that is in the same location, 'c:\snapshots\Merge\', and copy it to the subscribers. I wanted to avoid applying the snapshot over the WAN but from the performance I am getting the synchronization is going over the WAN. Does anybody have any ideas how to make sure that I am using the local copy of the snapshot and not the copy at the publisher? Thanks

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• Help choosing the right data structure

  - by devoured elysium

  I need a data structure with the following requirements: Needs to be able to get elements by index (like a List). I will always just add / remove elements from the end of the structure. I am inclined to use an ArrayList. In this situation, it seems to be O(1) both to read elements (they always are?), remove elements (I only need to remove them at the end of the list) and to add(I only add to the end of the list). There is only the problem that time to time the ArrayList will have a performance penalty when it's completly full and I need to add more elements to it. Is there any other better idea? I don't think of a data structure that'd beat the ArrayList here. Thanks

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• What is the best way to keep database data encrypted with user passwords?

  - by Dan Sosedoff

  Let's say an application has really specific data which belongs to a user, and nobody is supposed to see it except the owner. I use MySQL database with DataMapper ORM mapper. The application is written in Ruby on Sinatra. Application behavior: User signs up for an account. Creates username and password. Logs into his dashboard. Some fields in specific tables must be protected. Basically, I'm looking for auto-encryption for a model properties. Something like this: class Transaction include DataMapper::Resource property :id, Serial property :value, String, :length => 1024, :encrypted => true ... etc ... belongs_to :user end I assume that encryption/decryption on the fly will cause performance problems, but that's ok. At least if that works - I'm fine. Any ideas how to do this?

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• Using function arguments as local variables

  - by Rubys

  Something like this (yes, this doesn't deal with some edge cases - that's not the point): int CountDigits(int num) { int count = 1; while (num >= 10) { count++; num /= 10; } return count; } What's your opinion about this? That is, using function arguments as local variables. Both are placed on the stack, and pretty much identical performance wise, I'm wondering about the best-practices aspects of this. I feel like an idiot when I add an additional and quite redundant line to that function consisting of int numCopy = num, however it does bug me. What do you think? Should this be avoided?

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• Why SQL functions are faster than UDF

  - by Zerotoinfinite

  Though it's a quite subjective question but I feel it necessary to share on this forum. I have personally experienced that when I create a UDF (even if that is not complex) and use it into my SQL it drastically decrease the performance. But when I use SQL inbuild function they happen to work pretty faster. Conversion , logical & string functions are clear example of that. So, my question is "Why SQL in build functions are faster than UDF"? and it would be an advantage if someone can guide me how can I judge/manipulate function cost either mathematically or logically.

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