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  • How do you handle descriptive database table names and their effect on foreign key names?

    - by Carvell Fenton
    Hello, I am working on a database schema, and am trying to make some decisions about table names. I like at least somewhat descriptive names, but then when I use suggested foreign key naming conventions, the result seems to get ridiculous. Consider this example: Suppose I have table session_subject_mark_item_info And it has a foreign key that references sessionSubjectID in the session_subjects table. Now when I create the foreign key name based on fk_[referencing_table]__[referenced_table]_[field_name] I end up with this maddness: fk_session_subject_mark_item_info__session_subjects_sessionSubjectID Would this type of a foreign key name cause me problems down the road, or is it quite common to see this? Also, how do the more experienced database designers out there handle the conflict between descriptive naming for readability vs. the long names that result? I am using MySQL and MySQL Workbench if that makes any difference. Thanks!

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  • Fastest PNG decoder for .NET

    - by sboisse
    Our web server needs to process many compositions of large images together before sending the results to web clients. This process is performance critical because the server can receive several thousands of requests per hour. Right now our solution loads PNG files (around 1MB each) from the HD and sends them to the video card so the composition is done on the GPU. We first tried loading our images using the PNG decoder exposed by the XNA API. We saw the performance was not too good. To understand if the problem was loading from the HD or the decoding of the PNG, we modified that by loading the file in a memory stream, and then sending that memory stream to the .NET PNG decoder. The difference of performance using XNA or using System.Windows.Media.Imaging.PngBitmapDecoder class is not significant. We roughly get the same levels of performance. Our benchmarks show the following performance results: Load images from disk: 37.76ms 1% Decode PNGs: 2816.97ms 77% Load images on Video Hardware: 196.67ms 5% Composition: 87.80ms 2% Get composition result from Video Hardware: 166.21ms 5% Encode to PNG: 318.13ms 9% Store to disk: 3.96ms 0% Clean up: 53.00ms 1% Total: 3680.50ms 100% From these results we see that the slowest parts are when decoding the PNG. So we are wondering if there wouldn't be a PNG decoder we could use that would allow us to reduce the PNG decoding time. We also considered keeping the images uncompressed on the hard disk, but then each image would be 10MB in size instead of 1MB and since there are several tens of thousands of these images stored on the hard disk, it is not possible to store them all without compression.

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  • Help on Website response time KPI parameters

    - by geeth
    I am working on improving website performance. Here are the list of key performance indicators I am looking at for each page Total Bytes downloaded Number of requests DNS look up time FirstByte Download time DOM content load time Total load time Is there any optimum value for each KPI to indicate website performance? Please help me in this regard.

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  • How to rollback a database deployment without losing new data?

    - by devlife
    My company uses virtual machines for our web/app servers. This allows for very easy rollbacks of a deployment if something goes wrong. However, if an app server deployment also requires a database deployment and we have to rollback I'm kind of at a loss. How can you rollback database schema changes without losing data? The only thing that I can think of is to write a script that will drop/revert tables/columns back to their original state. Is this really the best way?

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  • FreeBSD ZFS RAID-Z2 performance issues

    - by Axel Gneiting
    I'm trying to build my own network attached storage based on FreeBSD+ZFS+standard components, but there are strange performance issues. The hardware specs are: AMD Athlon II X2 240e processor ASUS M4A78LT-M LE mainboard 2GiB Kingston ECC DDR3 (two sticks) Intel Pro/1000 CT PCIe network adapter 5x Western Digital Caviar Green 1.5TB I created a RAID-Z2 zpool from all disks. I installed FreeBSD 8.1 on that zpool following the tutorial. The SATA controllers are running in AHCI mode. Output of zpool status: pool: zroot state: ONLINE scrub: none requested config: NAME STATE READ WRITE CKSUM zroot ONLINE 0 0 0 raidz2 ONLINE 0 0 0 gptid/7ef815fc-eab6-11df-8ea4-001b2163266d ONLINE 0 0 0 gptid/80344432-eab6-11df-8ea4-001b2163266d ONLINE 0 0 0 gptid/81741ad9-eab6-11df-8ea4-001b2163266d ONLINE 0 0 0 gptid/824af5cb-eab6-11df-8ea4-001b2163266d ONLINE 0 0 0 gptid/82f98a65-eab6-11df-8ea4-001b2163266d ONLINE 0 0 0 The problem is that write performance on the pool is very very bad (<10 MB/s) and every application that is accessing the disk is unresponsive every few seconds when writing. It seems like writing is fine until the ZFS ark cache is full and then ZFS stalls the entire system I/O till it's finished writing that data. Also I'm getting kmem_malloc to small kernel panics. I've already tried to put vm.kmem_size="1500M" vm.kmem_size_max="1500M" into /boot/loader.conf, but it doesn't help. Does anyone know what's going on here? Am I really not having enough memory for ZFS to handle this RAID-Z2?

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  • Encrypt/Decrypt SQLite-database and use it "on the fly"

    - by Berschi
    Here's the thing: In my Qt4.6-Project, I use a SQLite-Database. This database shouldn't be unencrypted on my harddrive. So I want, that on every start of my program, the user gets asked to enter a password to decrypt the database. Of course the database never should appear "in clear" (not encrypted) on my harddrive. So is there any possibility to decrypt a SQLite-database "on the fly" and read and write data? What algorithm is here the best (maybe AES)? When it's not possible (or very slow), maybe it's better to encrypt every string in the database and decrypt the string when the password was right (so that a user could open the database, but has no clue what all the entrys could mean)?

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  • Microsoft Database project requires Visual studio 2010 premium or higher? Are there any open source

    - by skurge
    Hello, I need to know wether or not to buy the VS 2010 premium or not. I have the database project working on my own version of vs 2008 team suite. My coworkers only have 2008 professional. We are moving to VS2010 now. We do not have MSDN licenses for our company right now. We are looking to buy just the VS2010 no MSDN. It is very pricey to get 6 of VS2010 premium. We need to get our database into source control. We are currently email scripts around, and it very difficult to keep track off. Are there any non-microsoft solutions that would be the same features and be free?

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  • ORM solutions (JPA; Hibernate) vs. JDBC

    - by Grasper
    I need to be able to insert/update objects at a consistent rate of at least 8000 objects every 5 seconds in an in-memory HSQL database. I have done some comparison performance testing between Spring/Hibernate/JPA and pure JDBC. I have found a significant difference in performance using HSQL.. With Spring/Hib/JPA, I can insert 3000-4000 of my 1.5 KB objects (with a One-Many and a Many-Many relationship) in 5 seconds, while with direct JDBC calls I can insert 10,000-12,000 of those same objects. I cannot figure out why there is such a huge discrepancy. I have tweaked the Spring/Hib/JPA settings a lot trying to get close in performance without luck. I want to use Spring/Hib/JPA for future purposes, expandability, and because the foreign key relationships (one-many and many-many) are difficult to maintain by hand; but the performance requirements seem to point towards using pure JDBC. Any ideas of why there would be such a huge discrepancy?

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  • mySQL database password change now crashes Joomla.

    - by casim
    I have a mySQL database behind a Joomla install. I changed the database password because I forgot it but now Joomla crashes looking for the database. I guess joomla has the password written somewhere - if anyone knows I might be able to manual edit it and enter the new database password. Otherwise I'm hoping a manual install of a backup of the original database will work. I need to know does a backup include the database password. If yes, will reinstating my original database solve the problem for me by reverting the system back to it's original password? Please help. thx, s.

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  • Can a binary tree or tree be always represented in a Database as 1 table and self-referencing?

    - by Jian Lin
    I didn't feel this rule before, but it seems that a binary tree or any tree (each node can have many children but children cannot point back to any parent), then this data structure can be represented as 1 table in a database, with each row having an ID for itself and a parentID that points back to the parent node. That is in fact the classical Employee - Manager diagram: one boss can have many people under him... and each person can have n people under him, etc. This is a tree structure and is represented in database books as a common example as a single table Employee.

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  • How and Where do I learn about how to hook up my uncreated Database to a 3rd party API

    - by raln
    I want to create a database with information that I can send to a third party... they give their api on their website but they don't break it down for new / newbs like myself... I'm confused and was thinking of getting a developer to do this all for me but I DON'T want to get ripped off... and overpay All it is is a webapplication backed by a database onto their platform where they support different API's but I also need a function in my web app that can send various messages via XML, or SMPP to their webservice.. . hmm -Ken

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  • Need help trying to diagnose Symmetrix SAN performance issues

    - by arcain
    I am helping to benchmark hardware for a new SQL Server instance, and the volume presented to the OS for the data files is carved from a set of spindles on a Symmetrix SAN. The server has yet to have SQL Server installed, so the only activity on the box is our benchmarking. Now, our storage engineers say that this volume and it's resources are dedicated to our new server (I don't have access to see the actual SAN config) however the performance benchmarks are troubling. For example, the numbers look good until suddenly, and randomly, we see in our IO benchmarking tool wait times of 100 seconds, and disk queue lengths of 255 in perfmon. This SAN has an 8 GB cache, plus there are other applications besides ours that use the SAN. I'm wondering if (even though the spindles for our volumes should be dedicated to us) the cache may be getting hammered during the performance testing, or perhaps the spindles our volumes are on aren't really dedicated to us. We're not getting much traction from our storage engineers in helping us track down the problem, so if anybody has experience with diagnosing a problem like this and would like to share insights and troubleshooting methodologies, I'd appreciate it.

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  • SQL Error (1064) when importing data from SQL file

    - by mejpark
    I have a MySQL database, which was originally set up with the default latin1 character set and latin1_swedish_ci collation. I was using the database like this for sometime, until I noticed strange characters on my production web site, which is powered by a database exported from my development machine. At this point, I changed the default character set of the database and tables to utf8 and the collation to utf8_unicode_ci, converted the latin1 data inside each table to utf8 (using the 'convert data' option) and exported the database as a single SQL file using HeidiSQL. When the resulting SQL file is opened in Notepad++, several characters are rendered incorrectly. For example, en dashes (-) are displayed as – and e with accent (é) are displayed as é. I changed the encoding of the file from ANSI to UTF-8 (using the encoding menu option in Notepad++) and the offending characters are rendered correctly. I saved the new utf8-encoded SQL file and attempted to import the contents into the MySQL database on my production server. The import process fails with following error: /* SQL Error (1064): You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '?# -------------------------------------------------------- # Host: ' at line 1 */ /* Error with snippets directory: The specified path was not found */ The head of the SQL file: # -------------------------------------------------------- # Host: 127.0.0.1 # Server version: 5.1.33-community # Server OS: Win32 # HeidiSQL version: 6.0.0.3773 # Date/time: 2011-04-20 09:48:36 # -------------------------------------------------------- It chokes on the first line of the file, which is commented out. Why is this happening? I didn't have a problem loading data from SQL files until I changed the character set and collation of the database. I came up with an ugly workaround to this problem by performing following steps: Export database as single SQL file using HeidiSQL Open resulting file in Notepad++ and convert from ANSI to UTF-8 encoding Create new empty file in Notepad++, paste in UTF-8 and save file normally What am I missing here?

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  • How to select the nth row in a SQL database table?

    - by Charles Roper
    I'm interested in learning some (ideally) database agnostic ways of selecting the nth row from a database table. It would also be interesting to see how this can be achieved using the native functionality of the following databases: SQL Server MySQL PostgreSQL SQLite Oracle I am currently doing something like the following in SQL Server 2005, but I'd be interested in seeing other's more agnostic approaches: WITH Ordered AS ( SELECT ROW_NUMBER() OVER (ORDER BY OrderID) AS RowNumber, OrderID, OrderDate FROM Orders) SELECT * FROM Ordered WHERE RowNumber = 1000000 Credit for the above SQL: Firoz Ansari's Weblog Update: See Troels Arvin's answer regarding the SQL standard. Troels, have you got any links we can cite?

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  • ADO.NET: Faster way to check if the database server is accessible?

    - by lotana
    At the moment I am using this code to check if the database is accessible: public bool IsDatabaseOnline(string con) { bool isConnected = false; SQLConnection connect = null; try { connect = new SQLConnection(con); connect.Open(); isConnected = true; } catch (Exception e) { isConnected = false; } finally { if (connect != null) connect.Close(); } return isConnected; } While this code works fine, there is a disadvantage. If the server is not online it spends about 4 full seconds trying to open the connection before deciding that it is not available. Is there a way to test the connection without trying to actually opening it and waiting for the timeout? Something like a database-equivalent of ping?

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  • How to schedule a cron job to backup a MySql database every week?

    - by KevinM
    What is a command line I can use to back up a MySql database every single week into a file name with the date (so that it doesn't collide with previous backups)? Also, is this a reasonable backup strategy? My database is relatively small (a complete export is only 3.2 megs right now). The churn rate is relatively low. I need to be able to get the complete DB back if something goes wrong. And it would be extra cool if there's a way that I could see the changes that occur across a time span.

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  • python threading and performace?

    - by kumar
    I had to do heavy I/o bound operation, i.e Parsing large files and converting from one format to other format. Initially I used to do it serially, i.e parsing one after another..! Performance was very poor ( it used take 90+ seconds). So I decided to use threading to improve the performance. I created one thread for each file. ( 4 threads) for file in file_list: t=threading.Thread(target = self.convertfile,args = file) t.start() ts.append(t) for t in ts: t.join() But for my astonishment, there is no performance improvement whatsoever. Now also it takes around 90+ seconds to complete the task. As this is I/o bound operation , I had expected to improve the performance. What am I doing wrong?

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  • PHP - How to insert special characters into a database?

    - by Dodi300
    Hello. Can anyone tell me how to insert special characters into a MySQL database? I've made a PHP script which is meant to insert some words into a database, although if the word contains a ' then it wont be inserted. I can insert the special characters fine when using PHPmyAdmin, but it just doesn't work when inserting them via PHP. Could it be that PHP is changing the special characters into something else? If so, is there a way to make them insert properly? Thanks!

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  • Jquery Retrieving data from webpage and entering it in database.

    - by user279321
    Hello Everyone. I am new to Jquery. I want to read specific data(some div's only) from a webpage and store it in my database. Now I am not able to do so as load functions loads the data into the current page id. My goal is to read specific data and store them in database. So which Jquery function should I use for this? if someone can throw some light on it, it would be really helpful for me. I am using JSP,MySQL,Java.

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  • How does TopCoder evaluates code?

    - by Carlos
    If you are familiar with TopCoder you know that your source-code gets a final "grade/points" this depends on time, how many compiles, etc, one of the highest weighted being performance. But how can they test that, is there some sort of simple code (java or c++) to do it that you could share for me to evaluate and hopefully write my own to test the programs I write for University? This is sort of a follow up question to this one where I ask if shorter code results in best performance. P.S: Im interested in both of how topcoders knows performance and writing code to test performance.

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  • Are there any PHP Frameworks (e.g. CodeIgniter) that support database connections on a per user acco

    - by Brad G
    I'm looking into developing a multi-tenant SaaS application, and I found several sites that describe a solid way to separate the data using tenantIDs and updateable views. e.g. This blog post It all hinges on the ability to have your user accounts authenticated from a master users table and then having their respective database connections use those user-specific credentials. This way, the views can pull the userid and map it to the tenantID to display that user's view. However, most PHP frameworks tend to be very static when it comes to database connections (stored in text config files). They appear to be at odds. Does anyone know: a) how to make CodeIgniter handle this gracefully? b) a different PHP framework that might?

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  • Can a binary tree or tree be always represented in a Database table as 1 table and self-referencing?

    - by Jian Lin
    I didn't feel this rule before, but it seems that a binary tree or any tree (each node can have many children but children cannot point back to any parent), then this data structure can be represented as 1 table in a database, with each row having an ID for itself and a parentID that points back to the parent node. That is in fact the classical Employee - Manager diagram: one boss can have many people under him... and each person under him can have n people under him, etc. This is a tree structure and is represented in database books as a common example as a single table Employee.

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  • What is the correct stage to use for Google Guice in production in an application server?

    - by Yishai
    It seems like a strange question (the obvious answer would Production, duh), but if you read the java docs: /** * We want fast startup times at the expense of runtime performance and some up front error * checking. */ DEVELOPMENT, /** * We want to catch errors as early as possible and take performance hits up front. */ PRODUCTION Assuming a scenario where you have a stateless call to an application server, the initial receiving method (or there abouts) creates the injector new every call. If there all of the module bindings are not needed in a given call, then it would seem to have been better to use the Development stage (which is the default) and not take the performance hit upfront, because you may never take it at all, and here the distinction between "upfront" and "runtime performance" is kind of moot, as it is one call. Of course the downside of this would appear to be that you would lose the error checking, causing potential code paths to cause a problem by surprise. So the question boils down to are the assumptions in the above correct? Will you save performance on a large set of modules when the given lifetime of an injector is one call?

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  • PropelBundle database:create for postgres

    - by Karol85
    I've installed propel bundle for symfony2. my database configuration is: propel: dbal: driver: pgsql user: postgres password: postgres dsn: pgsql:host=localhost;port=5432;dbname=test_database options: {} attributes: {} When i wan to create this database from console (console propel: database:create) i have got strange error : Unable to open PDO connection [wrapped: SQLSTATE[08006] [7] FATAL: database "pgsql" does not exist. i created pgsql database on my localhost and everything was good. Database "test_database" was succesfull created. Can somebody explain me why i got this previous error? On mysql i've created database without any problems.

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