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  • Reference book on Ruby on Rails social network site for novices

    - by Christopher
    Hey, so I am a novice programmer who has only worked with HTML, CSS, and a touch of Java a couple of years ago. I am looking to try to get a social network site up and running on Ruby on Rails and was looking at RailsSpace: Building a Social Networking Website with Ruby on Rails (Addison-Wesley Professional Ruby Series) - Paperback (July 30, 2007) by Michael Hartl. This was published in 2007, however, and the newer reviews say it is not very helpful. Does anyone know if there are any new publications out there that walk you through building a social network site while teaching you the code(rather than just using a out of the box program)? Thanks

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  • MySQL: Is it faster to use inserts and updates instead of insert on duplicate key update?

    - by Nir
    I have a cron job that updates a large number of rows in a database. Some of the rows are new and therefore inserted and some are updates of existing ones and therefore update. I use insert on duplicate key update for the whole data and get it done in one call. But- I actually know which rows are new and which are updated so I can also do inserts and updates seperately. Will seperating the inserts and updates have advantage in terms of performance? What are the mechanics behind this ? Thanks!

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  • SQL query: how to translate IN() into a JOIN?

    - by tangens
    I have a lot of SQL queries like this: SELECT o.Id, o.attrib1, o.attrib2 FROM table1 o WHERE o.Id IN ( SELECT DISTINCT Id FROM table1, table2, table3 WHERE ... ) These queries have to run on different database engines (MySql, Oracle, DB2, MS-Sql, Hypersonic), so I can only use common SQL syntax. Here I read, that with MySql the IN statement isn't optimized and it's really slow, so I want to switch this into a JOIN. I tried: SELECT o.Id, o.attrib1, o.attrib2 FROM table1 o, table2, table3 WHERE ... But this does not take into account the DISTINCT keyword. Question: How do I get rid of the duplicate rows using the JOIN approach?

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  • AIO network sockets and zero-copy under Linux

    - by remyhorton
    I have been experimenting with async Linux network sockets (aio_read et al in aio.h/librt), and one thing i have been trying to find out is whether these are zero-copy or not. Pretty much all i have read so far discusses file I/O, whereas its network I/O i am interested in. AIO is a bit of a pain to use and i suspect is non-portable, so wondering whether its worth persevering with it. Zero-copy is just about the only advantage (albiet a major one for my purposes) it would have over (non-blocking) select/epoll..

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  • What are some good code optimization methods?

    - by esac
    I would like to understand good code optimization methods and methodology. How do I keep from doing premature optimization if I am thinking about performance already. How do I find the bottlenecks in my code? How do I make sure that over time my program does not become any slower? What are some common performance errors to avoid (e.g.; I know it is bad in some languages to return while inside the catch portion of a try{} catch{} block

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  • Designing a peer to peer network

    - by Varun
    I am designing a simple peer to peer network. The basic architecture will be as follows: A central server- that keeps track of all the peers. The job of this server is to keep track of all the peers that join the network. Every peer could do things: a. Download a file from it's peer b. Push a file (send a file) to it's peer. Could anybody please tell me what would be the best design for such a system? What would be the problems that i might run into and so on. I am planning to use Java as the programming language to implement. Would it be a good choice? Also, is it necessary that i would need a Linux box to develop the system? or is it fine if i use a Windows machine? Your help will be much appreciated! Thanks!

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  • Scalable way of doing self join with many to many table

    - by johnathan
    I have a table structure like the following: user id name profile_stat id name profile_stat_value id name user_profile user_id profile_stat_id profile_stat_value_id My question is: How do I evaluate a query where I want to find all users with profile_stat_id and profile_stat_value_id for many stats? I've tried doing an inner self join, but that quickly gets crazy when searching for many stats. I've also tried doing a count on the actual user_profile table, and that's much better, but still slow. Is there some magic I'm missing? I have about 10 million rows in the user_profile table and want the query to take no longer than a few seconds. Is that possible?

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  • Temporary intermediate table

    - by user289429
    In our project to generate massive reports in oracle we use some permanent table to hold intermediate results. For example to generate one report we run few queries and populate the table, at the final step we join the intermediate table with huge application tables. These intermediate tables are cleared for next report run. We have few concerns in performance areas. These intermediate tables are transactional and don't have statistics. Is it good idea to join these with application tables which are partitioned and have up to date statistics. We need these results stored in the intermediate tables to be available across requests from UI hence we are not in a position to use oracle provided temporary tables. Any thoughts on what could be done would be appreciated.

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  • How to decide between using PLINQ and LINQ at runtime?

    - by Hamish Grubijan
    Or decide between a parallel and a sequential operation in general. It is hard to know without testing whether parallel or sequential implementation is best due to overhead. Obviously it will take some time to train "the decider" which method to use. I would say that this method cannot be perfect, so it is probabilistic in nature. The x,y,z do influence "the decider". I think a very naive implementation would be to give both 1/2 chance at the beginning and then start favoring them according to past performance. This disregards x,y,z, however. I suspect that this question would be better answered by academics than practitioners. Anyhow, please share your heuristic, your experience if any, your tips on this. Sample code: public interface IComputer { decimal Compute(decimal x, decimal y, decimal z); } public class SequentialComputer : IComputer { public decimal Compute( ... // sequential implementation } public class ParallelComputer : IComputer { public decimal Compute( ... // parallel implementation } public class HybridComputer : IComputer { private SequentialComputer sc; private ParallelComputer pc; private TheDecider td; // Helps to decide between the two. public HybridComputer() { sc = new SequentialComputer(); pc = new ParallelComputer(); td = TheDecider(); } public decimal Compute(decimal x, decimal y, decimal z) { decimal result; decimal time; if (td.PickOneOfTwo() == 0) { // Time this and save result into time. result = sc.Compute(...); } else { // Time this and save result into time. result = pc.Compute(); } td.Train(time); return result; } }

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  • How to profile object creation in Java?

    - by gooli
    The system I work with is creating a whole lot of objects and garbage collecting them all the time which results in a very steeply jagged graph of heap consumption. I would like to know which objects are being generated to tune the code, but I can't figure out a way to dump the heap at the moment the garbage collection starts. When I tried to initiate dumpHeap via JConsole manually at random times, I always got results after GC finished its run, and didn't get any useful data. Any notes on how to track down excessive temporary object creation are welcome.

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  • How to set up a load/stress test for a web site?

    - by Ryan
    I've been tasked with stress/load testing our company web site out of the blue and know nothing about doing so. Every search I make on google for "how to load test a web site" just comes back with various companies and software to physically do the load testing. For now I'm more interested in how to actually go about setting up a load test like what I should take into account prior to load testing, what pages within my site I should be testing load against and what things I'm going to want to monitor when doing the test. Our web site is on a multi-tier system complete with a separate database server (IIS 7 Web Server, SQL Server 2000 db). I imagine I'd want to monitor both the web server and the database server for testing load however when setting up scenarios to load test the web server I'd have to use pages that query the database to see any load on the database server at the same time. Are web servers and database servers generally tested simultaneously or are they done as separate tests? As you can see I'm pretty clueless as to the whole operation so any incite as to how to go about this would be very helpful. FYI I have been tinkering with Pylot and was able to create and run a scenario against our site but I'm not sure what I should be looking for in the results or if the scenario I created is even a scenario worth measuring for our site. Thanks in advance.

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  • Transfer of directory structure over network

    - by singh
    I am designing a remote CD/DVD burner to address hardware constraints on my machine. My design works like this: (analogous to a network printer) Unix-based machine (acts as server) hosts a burner. Windows-based machine acts as client. Client prepares data to burn and transfers it to the server. Server burns the data on CD/DVD. My question is: what is the best protocol to transfer data over the network (Keeping the same directory hierarchy) between different operating systems?

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  • java increase xmx dynamically at runtime

    - by Tomer
    Hi, I have a jvm server in my machine, now I want to have 2 apservers of mine sitting in same machine, however I want the standby one to have a really low amount of memory allocated with xmx because its passive, one the main server (active) goes down I want to allocate more memory to my passive server which is already up without restarting it (I have have them both having too much xmx - note they would consume memory at startup and I cant allow possibility of outOfMemory). So I want passive - low xmx once active goes down I want my passive to receive much more xmx. is there a way for me to achieve that. Thanks

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  • Capturing network traffic on Linux

    - by Quandary
    Question: I have one Windows laptop, one Linux laptop and a wireless router. Now I want to "investigate" the hotmail/windows live protocol. What I want to do is route network traffic from the windows laptop via ethernet to the linux laptop, capture it on the Linux computer, forward it wirelessly to the router, receive the hotmail response from the router on the linux computer and forward it to the windows computer. How do I do that? In essence, switching the Linux laptop between the Windows laptop and the router, to capture network traffic ? Which program is best for capturing/analysing ? Please note that for whatever reason, packet capturing with winpcap on the windows computer doesn't work...

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  • Image size guidelines

    - by user502014
    Hi all, This may well be a little of an open-ended question The site I am working on requires to be optimised for performance. One of the key areas is to optimise the file sizes of the images used upon the site. Unfortunatley these images are being created by employees who do not have the required knowledge for creating images for the web, and it is my job to produce a set of guidelines for them to use. I was wondering whether there was any resource/guidlines/literature regarding typical images file sizes for images of different dimensions - as I would like to include something like this to aid them to ensure their images are being created properly. Any info would be greatly appreciated. Thanks in advance

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  • Improving WPF memory usage

    - by Krishna
    Hello developers Is there any way you can store the UI state to disk when a WPF form has been minimised. I have a complex GUI with few Tab Controls and it consumes quite a bit of memory which is kept allocated when the application is not active. I was hoping one of you may have got this working along the lines (or similar) Application Active User does work, plays with UI - enters some information in the text boxes and moves around the tabs User minimises the form to work with other applications On Minimise, Save the current state to the disk and dispose the root tabcontrol On Activiate, build the root tabcontrol from the disk and add to the controls collection Before I divein to do this, I thought it will help me if I ask this question here. Please let me know your thoughts

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  • Ping or otherwise tell if a device is on the network by MAC in C#

    - by Aric TenEyck
    I'm developing a home security application. One thing I'd like to do is automatically turn it off and on based on whether or not I'm at home. I have a phone with Wifi that automatically connects to my network when I'm home. The phone connects and gets its address via DHCP. While I could configure it to use a static IP, I'd rather not. Is there any kind of 'Ping' or equivalent in C# / .Net that can take the MAC address of a device and tell me whether or not it's currently active on the network?

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  • PHP: Mapped Network Drives

    - by Abs
    Hello all, I have mapped a network drive to a computer in my home network. Now I am trying to access it via PHP - I did this quick test: echo opendir('Z:\\'); This gives me: Warning: opendir(Z:\) [function.opendir]: failed to open dir: No error in C:\wamp\www\webs\tester-function.php on line 3 What have I done wrong here? I don't want my users typing in the UNC path so is there a way to get the UNC path for them and maybe that will work when I try to access it? This is possible in Microsoft languages but I am not sure how to get PHP to do this - maybe using a cmd.exe command? Please note, the mapped drive does exist as I can see it and I can access it. It also does not appear to be a permissions problem as I am assuming it would of complained about this IF it could access that drive...right? Thanks all for any help

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  • Is count(*) really expensive ?

    - by Anil Namde
    I have a page where I have 4 tabs displaying 4 different reports based off different tables. I obtain the row count of each table using a select count(*) from <table> query and display number of rows available in each table on the tabs. As a result, each page postback causes 5 count(*) queries to be executed (4 to get counts and 1 for pagination) and 1 query for getting the report content. Now my question is: are count(*) queries really expensive -- should I keep the row counts (at least those that are displayed on the tab) in the view state of page instead of querying multiple times? How expensive are COUNT(*) queries ?

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  • How can i test my DB speed? (Learning)

    - by acidzombie24
    I have design a database. Theres no columns with indexing, nor any code for optimizing. I am positive i should index certain columns since i search them a lot. My question is HOW do i test if any part of my database will be slow? ATM I am using sqlite and i will be switching to either MS Sql or MySql based on my host provider. Will creating 100,000 records in each table be enough? Or will that always be fast in sqlite and i need to do 1mil? Do i need 10mil before a database will become slow? Also how do i time it? I am using C# so should i use StopWatch or is there a ADO.NET/Sqlite function i should use?

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  • Will creating index help in this case

    - by The King
    I'm still a learning user of SQL-SERVER2005. Here is my table structure CREATE TABLE [dbo].[Trn_PostingGroups]( [ControlGroup] [char](5) COLLATE SQL_Latin1_General_CP1_CI_AS NOT NULL, [PracticeCode] [char](5) COLLATE SQL_Latin1_General_CP1_CI_AS NOT NULL, [ScanDate] [smalldatetime] NULL, [DepositDate] [smalldatetime] NULL, [NameOfFile] [varchar](50) COLLATE SQL_Latin1_General_CP1_CI_AS NULL, [DepositValue] [decimal](11, 2) NULL, [RecordStatus] [char](1) COLLATE SQL_Latin1_General_CP1_CI_AS NULL, CONSTRAINT [PK_Trn_PostingGroups_1] PRIMARY KEY CLUSTERED ( [ControlGroup] ASC, [PracticeCode] ASC )WITH (IGNORE_DUP_KEY = OFF) ON [PRIMARY] ) ON [PRIMARY] Scenario 1 : Suppose I have a query like this... Select * from Trn_PostingGroups where PracticeCode = 'ABC' Will indexing on Practice Code seperately help me in making my query faster?? Scenario 2 : Select * from Trn_PostingGroups where ControlGroup = 12701 and PracticeCode = 'ABC' and NameOfFile = 'FileName1' Will indexing on NameOfFile seperately help me in making my query faster ??

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  • How optimize queries with fully qualified names in t-sql?

    - by tomaszs
    Whe I call: select * from Database.dbo.Table where NAME = 'cat' It takes: 200 ms And when I change database to Database in Management Studio and call it without fully qualified name it's much faster: select * from Table where NAME = 'cat' It takes: 17 ms Is there any way to make fully qualified queries faster without changing database?

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  • SQL Query Theory Question...

    - by Keng
    I have a large historical transaction table (15-20 million rows MANY columns) and a table with one row one column. The table with one row contains a date (last processing date) which will be used to pull the data in the trasaction table ('process_date'). Question: Should I inner join the 'process_date' table to the transaction table or the transaction table to the 'process_date' table?

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