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• Implementing Transparent Persistence

  - by Jules

  Transparent persistence allows you to use regular objects instead of a database. The objects are automatically read from and written to disk. Examples of such systems are Gemstone and Rucksack (for common lisp). Simplified version of what they do: if you access foo.bar and bar is not in memory, it gets loaded from disk. If you do foo.bar = baz then the foo object gets updated on disk. Most systems also have some form of transactions, and they may have support for sharing objects across programs and even across a network. My question is what are the different techniques for implementing these kind of systems and what are the trade offs between these implementation approaches?

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• Threaded Django task doesn't automatically handle transactions or db connections?

  - by Gabriel Hurley

  I've got Django set up to run some recurring tasks in their own threads, and I noticed that they were always leaving behind unfinished database connection processes (pgsql "Idle In Transaction"). I looked through the Postgres logs and found that the transactions weren't being completed (no ROLLBACK). I tried using the various transaction decorators on my functions, no luck. I switched to manual transaction management and did the rollback manually, that worked, but still left the processes as "Idle". So then I called connection.close(), and all is well. But I'm left wondering, why doesn't Django's typical transaction and connection management work for these threaded tasks that are being spawned from the main Django thread?

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• How to handle Foreign key for optional field in .NET

  - by brz dot net

  What is the best way to handle following situation? A dropdown(for master table) is optional in a particular form. But, In database table the field is constrained with foreign key. If user don't select from dropdown then It creates problem because of foreign key. One solution is to create default option in master table and use it in case of blank selection. but in dropdown, we need to handle this to show on top. Is it perfect solution? Is there any other optimized solution for this? Thanks

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• Does introducing foreign keys to MySQL reduce performance

  - by Tam

  I'm building Ruby on Rails 2.3.5 app. By default, Ruby on Rails doesn't provide foreign key contraints so I have to do it manually. I was wondering if introducing foreign keys reduces query performance on the database side enough to make it not worth doing. Performance in this case is my first priority as I can check for data consistency with code. What is your recommendation in general? do you recommend using foreign keys? and how do you suggest I should measure this?

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• How to access a website's url programmatically from within the page

  - by Jeff

  For work, I am working on a site that has a feature that lets users make custom instances of the site depending on who they want to show it to. So if they want to show their potential employer a little bit about themselves, they can send them a custom url, that has a uid on the end of it that tells the database what to show and what not to when the site is loaded up. Now, I need to be able to take the value that is on the end of the url, this unique uid that corresponds with their preferences in the db, accessable on run time. Meaning that when someone types in this custom url, I need to be able to show the name of the person whose portfolio is being viewed BEFORE password authentication takes place... If I could get the URL, I suppose I could parse through it to find the necessary UID...but how do I get the url? Maybe I am just missing something here, but if anyone has any thoughts or ideas, it would be appreciated!! Thanks

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• ASP.net MVC How to run multiple instances of the same app at the same time in different subdomains?

  - by basilmir

  ASP.net MVC How to run multiple instances of the same app at the same time in different subdomains? I have a dozen or so subdomains. sub1.website.com sub2.website.com and the folder structure like this \website\sub1 \website\sub2 If i need to run the same app for all of the subdomains, what would be the best appoach? Host is in the root \website\ and have it figure out where to look based on the "user"? (i imagine i need to implement de logic in the code) OR Just copy the app in each of the subdomains, and have the app "not knowing" that it is actually an instance? (this would mean that when i update the app, i have to copy it everywhere) What other approaches are there to this kind of issue? Each app will use a different database name so that will need to we coded in somekind of external file.

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• FlockDB - What is it? And best cases for it uses.

  - by Guru

  Just came across FlockDB graph database. Details at github /flockDB. Twitter claims it uses FlockDB for the following: Twitter runs FlockDB on a large cluster of machines. we use it to store social graphs (who follows whom, who blocks whom) and secondary indices at twitter. At first glance, setup and trying it doesn't look straight forward. Have anyone already used it / setup this? If so, please answer the following general queries. What kind of applications is it better suited for? (Twitter claims it is simple and very rough, it remains to see what it meant though) How is FlockDB better than other graph db / noSQL db. Have you setup FlockDB, used it for a application? Early advices any? Note: I am evaluating the FlockDB and other graph databases mainly for learning them. Perhaps, I will build an application for that.

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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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• High level programming logic, design, pattern

  - by Muhammad Shahzad

  I have been doing programming from last 7 years, getting better and better, but still i think that am lacking something. I have been doing work in JOOMLA, MAGENTO, WP, Custom PHP, Opencart, laravel, codeignitor. Sometimes i need to design logic for a huge database application, in the applications we need nesting loops and queries, although i follow OOPS standards, ORM etc, still i feel i need more robust coding designs. I need to know how can i improve these things, so that code remain neat, efficient and faster. Also how big webapps like facebook twitter tests there code speed? How high level programmers choose design patterns. If you can help me find something useful with examples?

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• How to Detect Trusted Connection in Crystal Reports using VB.NET?

  - by Michael

  I have some Crystal Reports connecting to a Sql Server db that I would like to detect whether the connection is trusted or whether I need to supply the log on info (reports are not supplied by me so I can't control the connect method). If I just blindly supply login credentials, it won't connect if it is a trusted connection. The following does not work: oRpt = oCR.OpenReport("C:\MyReport.rpt") if oRpt.Database.Tables(1).ConnectionProperties.Item("Integrated Security") = True then 'trusted connection else 'supply login credentials end if It gives the following error: Operator '=' is not defined for type 'IConnectionProperty' and type 'Boolean'. I cannot find how create a construct in vb.net for IConnectionProperty. I can't find any documents from Crystal that explain it. I am using Crystal Reports XI - Developer

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• Deleting partial data from a field in MySQL

  - by Graham

  I am trying to remove a specific set of data from a MySQL database field, however I am not sure what the best statement would be for this. For example, if I have a data in a field such as... The use of a secondary password will allow you to gain access to your account from a non-authenticated computer. A non-authenticated computer is any computer that is not your primary computer, an elected authenticated computer or a computer that automatically deletes cookies. <p>This is a test</p> ...and I want to remove <p>This is a test</p> from the field, what statement would be best?

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• Should I use "id" or "unique username"?

  - by roa3

  I am using PHP, AS3 and mysql. I have a website. A flash(as3) website. The flash website store the members' information in mysql database through php. In "members" table, i have "id" as the primary key and "username" as a unique field. Now my situation is: When flash want to display a member's profile. My questions: Should Flash pass the member "ID" or "username" to php to process the mysql query? Is there any different passing the "id" or "username"? Which one is more secure? Which one you recommend? I would like to optimize my website in terms of security and performance.

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• Architecture for multiple web apps and databases.

  - by Matt

  We used to have only one web app, but now we are breaking it down into multiple ones. Each one will be packaged as separate product (web app) Some have things in common some do not. It was originally coded with php and using Postgresql 8.4 and CodeIgniter as the framework. I am looking for some good suggestions on how I should set up multiple web apps. They all have their own somewhat unique data. Some data in the databases can be common to some apps but not all. All the apps will be on one server and will have some kind of API to manipulate data. I want it to be structured such that one User account can access any product they purchase. (kinda like google accounts) I do not know if its a good idea to have multiple database, or just to have one big one. eventually we will be using S3 for some videos and other images. Your thoughts and suggestions are much appreciated.

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• PHP: Star rating system concept?

  - by Prashant

  I am using PHP/MYSQL/JQUERY. I have a site which have news section. On news details page, I want to add star rating system which will allow user to rate the news story. I am using this jquery rating system http://www.fyneworks.com/jquery/star-rating/ Now, I am not getting what will be the database structure and then what I need to code in PHP. I need what logic will be applied for this, like if 1000 people voted for the article, some given rating as 2 or 3 or1 or 5. Then Where I should be storing (db structure) this all and what I'll calculate (in php code). If someone has any article which shows this concept please provide. Please help, to understand the logic and concept of this. Thanks!

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• Find maximum number of logged on users in SQL

  - by lleto

  Hi, I want to keep tabs on the number of concurrent users of my application. I therefore log a time_start and a time_stop. If I now want to query the database for the maximum number of logged on users and return the start date, how would I do that. The table looks like this: id | time_start | time_stop ----+---------------------+--------------------- 1 | 2010-03-07 05:40:59 | 2010-03-07 05:41:33 2 | 2010-03-07 06:50:51 | 2010-03-07 10:50:51 3 | 2010-02-21 05:20:00 | 2010-03-07 12:23:44 4 | 2010-02-19 08:21:12 | 2010-03-07 12:37:28 5 | 2010-02-13 05:52:13 | Where time_stop is empty the user is still logged on. In this case I would expect to see 2010-03-07 returned, since all users (5) were logged on at that moment. However if I would run the query with 'where time_start BETWEEN '2010-02-17' AND '2010-02-23' I would expect to see 2010-02-21 with a maximum of 2. Is this possible direct in SQL (using postgres) or do I need to parse the results in PHP? Thanks, lleto

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• mysql_real_escape_string and search data in mySql DB

  - by ryrysz

  I have problem with php function : mysql_real_escape_string My test string: @,&!#$%^*()_+' "\/ I add this data to mySql database, like that (in short): $str = mysql_real_escape_string($str); $sql = "INSERT INTO table(company) VALUES('".$str. "')"; In DB is stored as: @,&!#$%^*()_+\' \"\\/ But problem is with find this data by SELECT statement. I want find, company where name is like ' " My SELECT's: SELECT company FROM table WHERE company LIKE '%\' "%'; SELECT company FROM table WHERE company LIKE '%\\' \\"%'; ; not working. This works: SELECT `company` FROM `table` WHERE `company` LIKE '%\\\' \\\\"%'; and SELECT `company` FROM `table` WHERE `company` LIKE '%\\\\\\\' \\\\\\\"%' But I dont know why this work :(. My questions are: why must add so many slashes ? how I can make correct query in PHP: $query = '\' "'; '%'.mysql_real_escape_string($query).'%' result is : '%\' \"%' '%'.mysql_real_escape_string(mysql_real_escape_string($query)).'%' result is : '%\\\' \\\"%' '%'.mysql_real_escape_string(mysql_real_escape_string(mysql_real_escape_string($query))).'%' result is : '%\\\\\\\' \\\\\\\"%' Only last one works good.

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• What is the best way to store categorical references in SQL tables?

  - by jlafay

  I'm wanting to store a wide array of categorical data in MySQL database tables. Let's say that for instance I want to to information on "widgets" and want to categorize attributes in certain ways, i.e. shape category. For instance, the widgets could be classified as: round, square, triangular, spherical, etc. Should these categories be stored within a table to reference them best from an application? Another possibility, I would imagine, would be to add a column to widgets that contained a shape column that contained a tiny int. That way my application could search shapes by that and then use a coordinating enum type that would map the shape int meanings. Which would be best? Or is there another solution that I'm not thinking of yet?

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• Best way to Store Passwords, User information/Profile data and Photo/Video albums for a social websi

  - by Nick

  Need some help figuring out how to best Store Passwords, User information/Profile data and Photo/Video albums for a social website? For photos/videos the actual photo/video + even encrypting the URL with the IDs to the photo/videos so other users cannot figure it out. Creating a site like myspace and designing retirement documents but i am unsure how to specify the security requirements for the database. Two things: 1) Protect from outside users 2) Protect all these from employees being able to access this info For #2, the additional question is: If we encrypt the user info and password so even the system admins cannot get in, how can we retrieve the user data tomorrow if someone flags the user's account as spam and admin needs to check it out or if law enforcement wants info on a user? Thanks.

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• How to Populate ComboBox from access db in C#

  - by Bomboe Cristian

  I have the next combobox: this.comboBoxProd.Enabled = false; this.comboBoxProd.FormattingEnabled = true; this.comboBoxProd.Items.AddRange(new object[] { "Cameras", "------------", " Digital IXUS 850 IS ", " Digital IXUS 900 Ti ", " Digital IXUS 75 -NEW- ", " Digital IXUS 70 -NEW- ", etc. I want to change it and take the values from a db. My database name is bd1.mdb and in the table Cameras it has the following fields: CamID, Cameras, Warranty, Year. I am only interested in the "Cameras" field. Thank you!

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• Microsoft Access vs Native SQL

  - by ktm5124

  Hypothetical: Let's say you are writing complex queries to a database and it is very important that the data you extracted is the correct result set (e.g., that you didn't mess up a JOIN by not using all the correct keys, and all the other things that can go wrong, et cetera). What would you rather use to do this? Would you write the query using Microsoft Access and its Design View, or would you write it in native SQL using a SQL IDE? What is the better professional choice? Thanks in advance your feedback!

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• 600 tables in DDBB

  - by Michael

  Hi all, I'm a very young software architect. Now I'm working in a very large and I have to lead a group of developers to rewrite all the mortgage system of the bank. I'm looking at database tables and I realize that there is no any data model, neither documentation. The worst part is that there are about 1000 tables in dev environment, and like 600 in production. I trust more the production environment, but anyway, what can I do? I mean, I can suicide me or something, but is there any good reverse engineering tool, so at least I could get the schema definition with the relations between tables and comments extracted from the fields? Can you advice me something? Thanks in advance.

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• Any tips of how to handle hierarchial trees in relational model?

  - by George

  Hello all. I have a tree structure that can be n-levels deep, without restriction. That means that each node can have another n nodes. What is the best way to retrieve a tree like that without issuing thousands of queries to the database? I looked at a few other models, like flat table model, Preorder Tree Traversal Algorithm, and so. Do you guys have any tips or suggestions of how to implement a efficient tree model? My objective in the real end is to have one or two queries that would spit the whole tree for me. With enough processing i can display the tree in dot net, but that would be in client machine, so, not much of a big deal. Thanks for the attention

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• How to Merge two databases in one in SQL Server 2008?

  - by SzamDev

  Hi I have 2 PCs, each one of them has SQL Server 2008 installed on it and there is a database with data in it. I need a way that I can move data in my DB from this SQL Server to another one (another PC which has the same DB) move data from one PC to another one - There is one problem, the ID column, because each DB in my 2 PCs has data in it so this column counts from 1,2,3,....... ( data will be conflict with other data in my DB ) Is there any way to solve my problem and move data successfully?

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• How to make schema and code dynamic?

  - by Jonarch

  I want to make my database schema and application code as dynamic as possible to handle "unknown" use cases and changes. Developing in PHP and MySQL. Twice now I have had to change my entire schema including table and column names and this means the developers have to go back to the application code and modify all the SQL queries and table/columns names. So to prevent this I want to if just like we do on pages where we have page content, title bar etc dynamic like a %variable%, can we do it for the schema and maybe even for the php code functions and classes somehow? It takes weeks to re-do all changes like this vs if it is dynamic it can be done in under a day.

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• Android: How to close a cursor that returns from Class to Activity

  - by Daniel

  I have: Accounts.java public class Accounts{ private SQLiteDatabase dbConfig; public Cursor list(Context context, String db, String where, String order) { DBHelper dbHelper = new DBHelper(context, db); dbConfig = dbHelper.getReadableDatabase(); Cursor c = dbConfig.query("accounts", new String[]{ "iId","sName"}, where, null, null, null, order); return c; } } and: MainActivity.java Accounts account = new Accounts(); Cursor cursor = account.list(getApplicationContext(), globalDB, null, null); while (cursor.moveToNext()) { int id = cursor.getInt(0); String name = cursor.getString(1); } cursor.close(); Running my application I get some logcat messages like: close() was never explicitly called on database... What is the best way to prevent it? How can I close a Cursor that returns from other class? Thanks

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