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  • Buffering db inserts in multithreaded program

    - by Winter
    I have a system which breaks a large taks into small tasks using about 30 threads as a time. As each individual thread finishes it persists its calculated results to the database. What I want to achieve is to have each thread pass its results to a new persisance class that will perform a type of double buffering and data persistance while running in its own thread. For example, after 100 threads have moved their data to the buffer the persistance class then the persistance class swaps the buffers and persists all 100 entries to the database. This would allow utilization of prepared statements and thus cut way down on the I/O between the program and the database. Is there a pattern or good example of this type of multithreading double buffering?

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  • Post and get at the same time in php

    - by user225269
    Do you have any suggestions with my problem. I need to use get and post at the same time. Get because I need to output what the user has typed. And post because I need to access the mysql database in relation to that input. It looks something like this: <form name="x" method="get" action="x.php"> <input name="year" type="text"> <select name="general" id="general"> <font size="3"> <option value="YEAR">Year</option> </form> This will output the contents of mysql depending on what the user will check: <form name="y" method="post" action"y.php"> <input name="fname" type="checkbox"> </form> And the form action of those two combined will look something like this: <?php if($_POST['general'] == 'YEAR'){ ?> <?php echo $_GET["year"]; ?> <?php $result2 = mysql_query("SELECT * FROM student WHERE student.YEAR='$syear'"); ?> <table border='1'> <tr> <?php if ( $ShowLastName ) { ?><th>LASTNAME</th><?php } ?> <?php if ( $ShowFirstName ) { ?><th>FIRSTNAME</th><?php } ?> </tr> <?php while ( $row = mysql_fetch_array($result2) ) { if (!$result2) { } ?> <tr> <td><?php echo $row['IDNO']?> </td> <td><?php echo $row['YEAR'] ?> </td> <?php if ( $ShowLastName ) { echo('<td>'.$row['LASTNAME'].'</td>'); } ?></td> <?php if ( $ShowFirstName ) { echo('<td>'.$row['FIRSTNAME'].'</td>'); } ?> I really get lots of undefined errors when I do this. What can you recommend that I should do in order to get the value inputted by the user together with the mysql data.

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  • How do I reload a Roo project without clearing the database?

    - by Omniwombat
    I've been learning how to build projects using Roo and am making good progress. I have the nucleus of a project which correctly displays my defined entities and allows me to create, edit, and delete the representative objects. I am using mysql at the database and I see that objects entered using the UI correctly appear in the mysql database. Per the Roo instructions, I am starting the webapp using "mvn tomcat:run". Unfortunately, I've discovered that whenever I restart Tomcat using Maven, it clears all of the existing objects out of the database. I'm left with empty tables. It seems to do this as the final step just prior to Tomcat stating that the server has started. I know this is just me being a n00b, but searches haven't been very helpful, none of the project's XML files seem relevant,

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  • how to write this query using joins?

    - by aquero
    Hi, i have a table campaign which has details of campaign mails sent. campaign_table: campaign_id campaign_name flag 1 test1 1 2 test2 1 3 test3 0 another table campaign activity which has details of campaign activities. campaign_activity: campaign_id is_clicked is_opened 1 0 1 1 1 0 2 0 1 2 1 0 I want to get all campaigns with flag value 3 and the number of is_clicked columns with value 1 and number of columns with is_opened value 1 in a single query. ie. campaign_id campaign_name numberofclicks numberofopens 1 test1 1 1 2 test2 1 1 I did this using sub-query with the query: select c.campaign_id,c.campaign_name, (SELECT count(campaign_id) from campaign_activity WHERE campaign_id=c.id AND is_clicked=1) as numberofclicks, (SELECT count(campaign_id) from campaign_activity WHERE campaign_id=c.id AND is_clicked=1) as numberofopens FROM campaign c WHERE c.flag=1 But people say that using sub-queries are not a good coding convention and you have to use join instead of sub-queries. But i don't know how to get the same result using join. I consulted with some of my colleagues and they are saying that its not possible to use join in this situation. Is it possible to get the same result using joins? if yes, please tell me how.

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  • using Hibernate to loading 20K products, modifying the entity and updating to db

    - by Blankman
    I am using hibernate to update 20K products in my database. As of now I am pulling in the 20K products, looping through them and modifying some properties and then updating the database. so: load products foreach products session begintransaction productDao.MakePersistant(p); session commit(); As of now things are pretty slow compared to your standard jdbc, what can I do to speed things up? I am sure I am doing something wrong here.

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  • how to update multiple tables in oracle DB?

    - by murali
    hi, i am using two tables in my oracle 10g. the first table having the keyword,count,id(primary key) and my second table having id, timestamp.. but i am doing any chages in the first table(keyword,count) it will reflect on the my second table timestamp.. i am using id as reference for both the tables... table1: CREATE TABLE Searchable_Keywords (KEYWORD_ID NUMBER(18) PRIMARY KEY, KEYWORD VARCHAR2(255) NOT NULL, COUNT NUMBER(18) NOT NULL, CONSTRAINT Searchable_Keywords_unique UNIQUE(KEYWORD) ); table2: CREATE TABLE Keywords_Tracking_Report (KEYWORD_ID NUMBER(18), PROCESS_TIMESTAMP TIMESTAMP(8) ); how can update one table with reference of another table.. help me plz...

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  • Custom session state provider needed for DB storage?

    - by subt13
    I know this question is related to many others, but please bear with me. I am trying an experiment to store all information in database tables instead of the ASP.NET session. In ASP.NET 4 one can create a custom provider for session. So, again should I implement a Custom Session-State Provider or should I just disable session (in Web.config)? Thanks! From the comments my question can be misunderstood. Hopefully this tidbit will help clarify: I don't want to store the session in the database. I want to store information in the database that you would typically store in the session. One reason why: I don't want to carry around a session on every page, especially if that page doesn't care about 90 percent of the information in the session

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  • Data Visualization Prototype (Java/Eclipse/DAO/Relational DB)

    - by Vince
    Hello, I am building a prototype application which displays various 2D & 3D data charts. I am using a third party library for the charts, the database and data extraction layer have already been coded. Can you advise on a good desktop Framework to use within Eclipse to provide a 'professional' looking GUI with minimum coding required (This is just a prototype). Further can anyone advise an effective method to port this application to a web server so users could access remotely? I have limited experience with GWT, are their more suitable alternatives? Many Thanks

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  • Get the first and last posts in a thread

    - by Grampa
    I am trying to code a forum website and I want to display a list of threads. Each thread should be accompanied by info about the first post (the "head" of the thread) as well as the last. My current database structure is the following: threads table: id - int, PK, not NULL, auto-increment name - varchar(255) posts table: id - int, PK, not NULL, auto-increment thread_id - FK for threads The tables have other fields as well, but they are not relevant for the query. I am interested in querying threads and somehow JOINing with posts so that I obtain both the first and last post for each thread in a single query (with no subqueries). So far I am able to do it using multiple queries, and I have defined the first post as being: SELECT * FROM threads t LEFT JOIN posts p ON t.id = p.thread_id ORDER BY p.id LIMIT 0, 1 The last post is pretty much the same except for ORDER BY id DESC. Now, I could select multiple threads with their first or last posts, by doing: SELECT * FROM threads t LEFT JOIN posts p ON t.id = p.thread_id ORDER BY p.id GROUP BY t.id But of course I can't get both at once, since I would need to sort both ASC and DESC at the same time. What is the solution here? Is it even possible to use a single query? Is there any way I could change the structure of my tables to facilitate this? If this is not doable, then what tips could you give me to improve the query performance in this particular situation?

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  • Mobile application using REST web services in java to access database

    - by user1761991
    HTML5+CSS+javascript mobile app need to communicate with mysql database through REST Web services.I have a doubt in how html5 app consuming web services(Both storing and retrieving data in mysql database). Moreover, the app is not a native one. Phonegap is used to built this app to support in all OS available. The required rest web sevices ought to have JAVA in server coding part.Is there any possibility of having generalized rest web services which can able to consumed from all OS? Can anyone suggest any ideas related to this ? As i am new to mobile development unable to figure out the right and correct method to proceed. Thanks in Advance

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  • Manipulate data in the DB query or in the code

    - by DrDro
    How do you decide on which side you perform your data manipulation when you can either do it in the code or in the query ? When you need to display a date in a specific format for example. Do you retrieve the desired format directly in the sql query or you retrieve the date then format it through the code ? What helps you to decide : performance, best practice, preference in SQL vs the code language, complexity of the task... ?

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  • SQL with HAVING and temp table not working in Rails

    - by chrisrbailey
    I can't get the following SQL query to work quite right in Rails. It runs, but it fails to do the "HAVING row_number = 1" part, so I'm getting all the records, instead of just the first record from each group. A quick description of the query: it is finding hotel deals with various criteria, and in particular, priortizing them being paid, and then picking the one with the highest dealrank. So, if there are paid deal(s), it'll take the highest one of those (by dealrank) first, if no paid deals, it takes the highest dealrank unpaid deal for each hotel. Using MAX(dealrank) or something similar does not work as a way to pick off the first row of each hotel group, which is why I have the enclosing temptable and the creation of the row_number column. Here's the query: SELECT *, @num := if(@hid = hotel_id, @num + 1, 1) as row_number, @hid := hotel_id as dummy FROM ( SELECT hotel_deals.*, affiliates.cpc, (CASE when affiliates.cpc 0 then 1 else 0 end) AS paid FROM hotel_deals INNER JOIN hotels ON hotels.id = hotel_deals.hotel_id LEFT OUTER JOIN affiliates ON affiliates.id = hotel_deals.affiliate_id WHERE ((hotel_deals.percent_savings = 0) AND (hotel_deals.booking_deadline = ?)) GROUP BY hotel_deals.hotel_id, paid DESC, hotel_deals.dealrank ASC) temptable HAVING row_number = 1 I'm currently using Rails' find_by_sql to do this, although I've also tried putting it into a regular find using the :select, :from, and :having parts (but :having won't get used unless you have a :group as well). If there is a different way to write this query, that'd be good to know too. I am using Rails 2.3.5, MySQL 5.0.x.

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  • rails db migration, undefined method `to_sym', cant figure out syntax

    - by oelbrenner
    the original migration looks like this: class CreateUsers true do |t| t.string :login, :limit = 40 t.string :name, :limit = 100, :default = '', :null = true t.string :email, :limit = 100 t.string :crypted_password, :limit = 40 t.string :salt, :limit = 40 t.string :remember_token, :limit = 40 t.datetime :remember_token_expires_at t.string :activation_code, :limit = 40 t.datetime :activated_at, :datetime t.string :state, :null = :no, :default = 'passive' t.datetime :deleted_at t.integer :occupation_id, :null = :yes t.datetime :paid_up_to_date, :date t.timestamps end and I am trying to change the default of "state" to be "active" instead of passive so my attempt at a migration looks like this: ( still learning.. be gentle ) class ChangeUserStateDefault < ActiveRecord::Migration def self.up change_column :users, :state, :null = :no, :default = 'active' end def self.down end end

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  • Generating a set of files containing dumps of individual tables in a way that guarantees database co

    - by intuited
    I'd like to dump a MySQL database in such a way that a file is created for the definition of each table, and another file is created for the data in each table. I'd like this to be done in a way that guarantees database integrity by locking the entire database for the duration of the dump. What is the best way to do this? Similarly, what's the best way to lock the database while restoring a set of these dump files? edit I can't assume that mysql will have permission to write to files.

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  • Can't establish a DB connection. (Maybe threads related)

    - by JobGovernor
    Hello, I am getting this exception on the Rufus::Scheduler ActiveRecord::ConnectionTimeoutError: could not obtain a database connection within 5 seconds. The max pool size is currently 30; consider increasing it. I've increased the pool from 10 to 30. And I also monkey patched the method which raises the exception to also call ActiveRecord::Base.verify_active_connections! before doing its job. And I also restarted the service which executes the script so that the new code is run. Any ideas would be greatly appreciated. Let me know if you need any other info about environment or whatnot. Thank you.

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  • How do I set ORDER BY params using prepared PDO statement?

    - by Marlorn
    I'm having problems using params in the ORDER BY section of my SQL. It doesn't issue any warnings, but prints out nothing. $order = 'columnName'; $direction = 'ASC'; $stmt = $db->prepare("SELECT field from table WHERE column = :my_param ORDER BY :order :direction"); $stmt->bindParam(':my_param', $is_live, PDO::PARAM_STR); $stmt->bindParam(':order', $order, PDO::PARAM_STR); $stmt->bindParam(':direction', $direction, PDO::PARAM_STR); $stmt->execute(); The :my_param works, but not :order or :direction. Is it not being internally escaped correctly? Am I stuck inserting it directly in the SQL? Like so: $order = 'columnName'; $direction = 'ASC'; $stmt = $db->prepare("SELECT * from table WHERE is_live = :is_live ORDER BY $order $direction"); Is there a PDO::PARAM_COLUMN_NAME constant or some equivalent? Thanks!

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  • database logic for tracking each and every operation in my web application

    - by ripa
    I am developing an Web application. In my application, I need to keep track of each and every operation for every logged in user. I have planned following for achieving this task:- I will create stored procedure in mysql. I will trigger this procedure on each table's insert , update delete. This is an tough job for me. Will anybody direct me in the right way? I am using PHP based Codeigniter framework and mysql database.

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  • Using boost::random to select from an std::list where elements are being removed

    - by user144182
    See this related question on more generic use of the Boost Random library. My questions involves selecting a random element from an std::list, doing some operation, which could potentally include removing the element from the list, and then choosing another random element, until some condition is satisfied. The boost code and for loop look roughly like this: // create and insert elements into list std::list<MyClass> myList; //[...] // select uniformly from list indices boost::uniform_int<> indices( 0, myList.size()-1 ); boost::variate_generator< boost::mt19937, boost::uniform_int<> > selectIndex(boost::mt19937(), indices); for( int i = 0; i <= maxOperations; ++i ) { int index = selectIndex(); MyClass & mc = myList.begin() + index; // do operations with mc, potentially removing it from myList //[...] } My problem is as soon as the operations that are performed on an element result in the removal of an element, the variate_generator has the potential to select an invalid index in the list. I don't think it makes sense to completely recreate the variate_generator each time, especially if I seed it with time(0).

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  • GUID not being generated automatically when db.submitchanges()

    - by BlindingDawn
    I have a couple of tables I ported over to a new database. Everything is exactly the same from the legacy one to the new one. The back-end code that submits the user generated data to the database is also the same. When I submit changes to the database, all of the submitted information populates the correct columns but the column that stores the GUID populates with all 0's. When I enter in the columns manually using SQL Server Management Studio, the GUID gets populated as it does in the legacy version. Am I missing something?

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  • Bash init.d script detect that mysqld has started and is running

    - by Ricket
    I'm working on my dedicated server running CentOS. I found out that one of my applications which starts up via a script in /etc/init.d/ requires MySQL to be running, or else it throws an error, so essentially I currently have to start it by hand. How can I detect, in a bash script (#!/bin/sh), whether the MySQL service has started yet? Is there some way to poll port 3306 until it is open to accept connections, and only then continue with the script? Or maybe set an order so that the script doesn't run until the mysqld script runs?

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  • How to use SOCI C++ Database library?

    - by NeDark
    I'm trying to implement soci in my program but I don't know how. I'm using C++ on linux, on a project on netbeans. I have followed the steps in http://soci.sourceforge.net/doc/structure.html to install it, and I tried to copy the files soci.h from /src/core and soci-mysql.h from /src/backends/mysql in my proyect but it gives compilation error (these files include other soci files, but it's illogical to copy all files into the directory...). I have read the guide several time but I don't understand what I'm doing wrong, the examples only include these files. Thanks. Edit: I have given more information in a comment below the answer. I don't know what steps I have to do to implement soci.

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  • dotnet nuke mysql

    - by user311166
    windows server 2003. i have an existing dotnetnuke website. ms sql is currently running and being used by dotnetnuke. i want to use mysql for other purposes. would installing mysql on the same server interfere with dotnetnuke? it seems that shortly after installing dotnetnuke our website stopped populating pages.

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  • Using Enum in Hibernate causes select followed by an update statement

    - by Leonardo
    Hi all, I have a mapped entity wich has an enum property. By loking at log file, whenever I run a select statement on such entity, the result is an immediately following update. For example if my result set contains 100 records, then I have: [INFO org... select...] [INFO org... update... where id=?] [INFO org... update... where id=?] .... repeated 100 times If I mark the property as update=false the problem disappear. The enum is assigned trough an enum converter class, which I copied from a well known book. So I don't know if I just copy and paste the code. Here it is how is declared on hbm file. <typedef class="mypackage.HbnEnumConverter" name="the_type"> <param name="enumClassname">mypackage.TheType</param> </typedef> Can you point out a direction to investigate this ? Beside, what are the consequences of having update=false on hibernate field ? thanks

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