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  • Can in-memory SQLite databases scale with concurrency?

    - by Kent Boogaart
    In order to prevent a SQLite in-memory database from being cleaned up, one must use the same connection to access the database. However, using the same connection causes SQLite to synchronize access to the database. Thus, if I have many threads performing reads against an in-memory database, it is slower on a multi-core machine than the exact same code running against a file-backed database. Is there any way to get the best of both worlds? That is, an in-memory database that permits multiple, concurrent calls to the database?

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  • Multiple calculations on the same set of data: ruby or database?

    - by Pierre
    Hi, I have a model Transaction for which I need to display the results of many calculations on many fields for a subset of transactions. I've seen 2 ways to do it, but am not sure which is the best. I'm after the one that will have the least impact in terms of performance when data set grows and number of concurrent users increases. data[:total_before] = Transaction.where(xxx).sum(:amount_before) data[:total_after] = Transaction.where(xxx).sum(:amount_after) ... or transactions = Transaction.where(xxx) data[:total_before]= transactions.inject(0) {|s, e| s + e.amount_before } data[:total_after]= transactions.inject(0) {|s, e| s + e.amount_after } ... Which one should I choose? (or is there a 3rd, better way?) Thanks, P.

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  • How to map combinations of things to a relational database?

    - by Space_C0wb0y
    I have a table whose records represent certain objects. For the sake of simplicity I am going to assume that the table only has one row, and that is the unique ObjectId. Now I need a way to store combinations of objects from that table. The combinations have to be unique, but can be of arbitrary length. For example, if I have the ObjectIds 1,2,3,4 I want to store the following combinations: {1,2}, {1,3,4}, {2,4}, {1,2,3,4} The ordering is not necessary. My current implementation is to have a table Combinations that maps ObjectIds to CombinationIds. So every combination receives a unique Id: ObjectId | CombinationId ------------------------ 1 | 1 2 | 1 1 | 2 3 | 2 4 | 2 This is the mapping for the first two combinations of the example above. The problem is, that the query for finding the CombinationId of a specific Combination seems to be very complex. The two main usage scenarios for this table will be to iterate over all combinations, and the retrieve a specific combination. The table will be created once and never be updated. I am using SQLite through JDBC. Is there any simpler way or a best practice to implement such a mapping?

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  • Using IPrinciple.Identity.Name as a key in a dataBase to identify user's rows.

    - by bplus
    I'm writing a small intranet app that uses Windows Authentication and Asp.Net MVC. I need to store various bits of data in a db against each user. As far as I can tell the IPrinciple object does not seem to have something like a unique id. So I was thinking I could just use User.Identity.Name as a unique value to identify rows in my db. Is this a bad idea? Is there an alternative to this approach? Thanks for any help.

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  • How to use database to generate multiple folder content page?

    - by VenomVipes
    Scenario :I am trying to build a Mobile Entertainment Portal. It will enable users to download Music & Movies to their Cell Phones... Problem Exp : Suppose I upload 100 folders of Songs, each folder is for one Album. I want a way to generate a page with all the folders name (Album Name) in it. If user click on the page, they should be taken to a page where they get list of all songs in the album. Clicking on any song name will let them download it. Can it be done anyway or will I have to manually design each of the 3 pages for each album. If I do that, its time consuming and also will be difficult to change anything like footer, header...

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  • How do you optimize database performance when providing results for autocomplete/iterative search?

    - by Howiecamp
    Note: In this question I'm using the term "autocomplete" (or "iterative search") to refer to returning search-as-you-type results, e.g. like Google Search gives you. Also my question is not specific to web applications vs. fat client apps. How are SQL SELECT queries normally constructed to provide decent performance for this type of query, especially over arbitrarily large data sets? In the case where the search will only query based on the first n characters (easiest case) am I still issuing a new SELECT result FROM sometable WHERE entry LIKE... on each keypress. Even with various forms of caching this seems like it might result in poor performance. In cases where you want your search string to return results with prefix matches, substring matches, etc. it's an even more difficult problem. Looking at a case of searching a list of contacts, you might return results that match FirstName + LastName, LastName + FirstName, or any other substring.

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  • Can I change the datsource of report model at runtime

    - by Manab De
    I've some adhoc reports developed on some report models which are published on Report Server (we're using SSRS 2008). Everything is running well. Now in our production environment we've near about forty (40) customers who have their own database (each have the same table structures and other database objects). Now the challenge is whenever a customer will log into the report server using windows authentication and trying to view those reports we need to get the SQL data from the proper database only. Reports are designed using the report model and each model has a valid data source which is connected to particular database. We can create forty separate data sources each will be connected to specific database. My question is, is there any way through which we can change the report model data source name dynamically or during runtime based on the customer name so that during execution of the report, SSRS would fetch the data from the correct database but not from any other database. Please help me.

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  • How do i view the local database version in safari on the iphone?

    - by ~potsed
    I am trying to see the localDatabase version from my iPhone in safari but it is not displaying, according to the docs i am supposed to be able to do this: var db = openDatabase('dbShortName', '', 'dbLongName', 1000); alert(db.version); and it should alert the current version number. It does not. It works in Chrome and safari for the desktop but not the iPhone. Does anybody have some idea why? My next option is to store the version in a separate table, but I would prefer to use the built in system. Thanks in advance.

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  • How can I delete ghost database field between a special date?

    - by Chiyou
    I have a mysql table with many user input and I want to delete ghost e-mail between a special date. I use this query and it seems to work very good: DELETE u1 From tx_table u1 JOIN tx_table u2 USING (email) WHERE u1.tstamp < u2.tstamp but I want to delete between a longer time. When I add 300 it seems to delete everything in my table: DELETE u1 From tx_table u1 JOIN tx_table u2 USING (email) WHERE u1.tstamp < u2.tstamp+300. How can I add 5 minutes to the tstamp with SQL?

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  • Are indexes good or bad for a large database?

    - by gmemon
    Hello All, I read on MySQL Performance Blog that when tables are large, it is better to scan full tables, instead of using indexes. I have a table with tens of millions of rows. When conducting queries, if I use no indexes, then queries are 24 times slower than with indexes. I know lot of things may cause this (e.g., are rows stored sequentially), but can you please give me some hints what might be happening? Or how I should start examining this issue? I want to understand when use of indexes is preferred and when it's not Thanks

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  • How to enable an AdventureWorks database in a web application?

    - by salvationishere
    I am developing a C#/SQL ASP.NET web application in VS 2008. I want the users to be able to select an Adventureworks table and then an input file. The user is then able to map columns from the file with the selected table. This app works fine now in VS. But when I Browse in IIS, it doesn't show any of the tables. I think this is because currently Adventureworks connection string is integrated security (Windows authentication). If I want users to be able to select a table, do I have to change connection to SQL Server authentication? And if so, is the only way to do this to reinstall SQL Server? Or can I just reinstall Adventureworks? And if I reinstall SQL Server, do I need to reinstall VS also for this to work? This could be painful...

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  • How to fetch a random record from SQLite database?

    - by Bruce
    I am working on PHP. I was working with MySQL before. Here is the code I used - $offset_result = mysqli_query($con, " SELECT FLOOR(RAND() * COUNT(*)) AS `offset` FROM students "); $offset_row = mysqli_fetch_object( $offset_result ); $offset = $offset_row->offset; $result = mysqli_query($con, " SELECT name FROM students LIMIT $offset, 1 " ); $row = mysqli_fetch_row($result); mysqli_free_result($result); What will be the corresponding set of statements for SQLite?

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  • How to display records below form on submission in php without the use of database?

    - by OM The Eternity
    How to make the use of hidden variables as array for consecutive submission of data so that they can be used to display the records list. I have a form with 4 text fields and a file upload field.. as i submit he form it should get appended to the list which needs to be displayed below the form, such that these values are NOT stored in the DB.. So in this case how can i use the post array to collect the data and display in the list below?

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  • How to display records below form on submission in php without the use of database?

    - by OM The Eternity
    I have a form with multiple fields in it along with a image input field, just below the form i have a list to be displayed on every submit of this form... this has to be done without the use of DB.. I think this can be achieved by using session but its not working with me, as evrytime page gets refreshed and session gets recreated/reset.. Please help me in resolving this issue

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  • Should I *always* import my file references into the database in drupal?

    - by sprugman
    I have a cck type with an image field, and a unique_id text field. The file name of the image is based on the unique_id. All of the content, including the image itself is being generated automatically via another process, and I'm parsing what that generates into nodes. Rather than creating separate fields for the id and the image, and doing an official import of the image into the files table, I'm tempted to only create the id field and create the file reference in the theme layer. I can think of pros and cons: 1) Theme Layer Approach Pros: makes the import process much less complex don't have to worry about syncing the db with the file system as things change more flexible -- I can move my images around more easily if I want Cons: maybe not as much The Drupal Way™ not as pure -- I'll wind up with more logic on the theme side. 2) Import Approach Pros: import method is required if we ever wanted to make the files private (we won't.) safer? Maybe I'll know if there's a problem with the image at import time, rather than view time. Since I'll be bulk importing, that might make a difference. if I delete a node through the admin interface, drupal might be able to delete the file for me, as well. Con: more complex import and maintenance All else being equal, simpler is always better, so I'm leaning toward #1. Are there any other issues I'm missing? (Since this is an open ended question, I guess I'll make it a community wiki, whatever that means.)

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  • How do I go about link web content in a database with a nested set model?

    - by wb
    My nested set table is as follows. create table depts ( id int identity(0, 1) primary key , lft int , rgt int , name nvarchar(60) , abbrv nvarchar(20) ); Test departments. insert into depts (lft, rgt, name, abbrv) values (1, 14, 'root', 'r'); insert into depts (lft, rgt, name, abbrv) values (2, 3, 'department 1', 'd1'); insert into depts (lft, rgt, name, abbrv) values (4, 5, 'department 2', 'd2'); insert into depts (lft, rgt, name, abbrv) values (6, 13, 'department 3', 'd3'); insert into depts (lft, rgt, name, abbrv) values (7, 8, 'sub department 3.1', 'd3.1'); insert into depts (lft, rgt, name, abbrv) values (9, 12, 'sub department 3.2', 'd3.2'); insert into depts (lft, rgt, name, abbrv) values (10, 11, 'sub sub department 3.2.1', 'd3.2.1'); My web content table is as follows. create table content ( id int identity(0, 1) , dept_id int , page_name nvarchar(60) , content ntext ); Test content. insert into content (dept_id, page_name, content) values (3, 'index', '<h2>welcome to department 3!</h2>'); insert into content (dept_id, page_name, content) values (4, 'index', '<h2>welcome to department 3.1!</h2>'); insert into content (dept_id, page_name, content) values (6, 'index', '<h2>welcome to department 3.2.1!</h2>'); insert into content (dept_id, page_name, content) values (2, 'what-doing', '<h2>what is department 2 doing?/h2>'); I'm trying to query the correct page content (from the content table) based on the url given. I can easily accomplish this task with a root department. However, querying a department with multiple depths is proving to be a little harder. For example: http://localhost/departments.asp?d3/ (Should return <h2>welcome to department 3!</h2>) http://localhost/departments.asp?d2/what-doing (Should return <h2>what is department 2 doing?</h2>) I'm not sure if this can be create in one query or if there will need to be a recursive function of some sort. Also, if there is nothing after the last / then assume we want the index page. How can this be accomplished? Thank you.

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  • Database, Jquery, Ajax and Zend Framework. How to use all togheter?

    - by rasouza
    I have a form rendered in the view which action is setted to the same page /index. <form action="" name="formRegistro" id="formRegistro"> and a JQuery function which is called when the form is submitted $('#formRegistro').submit(function() { // Retrevies data from the form data = $('#someInput').val() //Execute AJAX $.get( 'http://localhost/myproject/', { data }, function(data){ $('#divStatus').html(data); } ); //Prevent page loading return false; }); I'm using and if statement in the IndexController to change between normal view and post view if ($this->_request->isGet()) { and I'd like to output a message in the #divStatus but with I don't know how to do it

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