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• Updating a local sqlite db that is used for local metadata & caching from an service?

  - by Pharaun

  I've searched through the site and haven't found a question/answer that quite answer my question, the closest one I found was: Syncing objects between two disparate systems best approach. Anyway to begun, because there is no RSS feeds available, I'm screen scrapping a webpage, hence it does a fetch then it goes through the webpage to scrap out all of the information that I'm interested in and dumps that information into a sqlite database so that I can query the information at my leisure without doing repeat fetching from the website. However I'm also storing various metadata on the data itself that is stored in the sqlite db, such as: have I looked at the data, is the data new/old, bookmark to a chunk of data (Think of it as a collection of unrelated data, and the bookmark is just a pointer to where I am in processing/reading of the said data). So right now my current problem is trying to figure out how to update the local sqlite database with new data and/or changed data from the website in a manner that is effective and straightforward. Here's my current idea: Download the page itself Create a temporary table for the parsed data to go into Do a comparison between the official and the temporary table and copy updates and/or new information to the official table This process seems kind of complicated because I would have to figure out how to determine if the data in the temporary table is new, updated, or unchanged. So I am wondering if there isn't a better approach or if anyone has any suggestion on how to architecture/structure such system?

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• Core Data, Bindings, value transformers : crash when saving

  - by Gael

  Hi, I am trying to store a PNG image in a core data store backed by an sqlite database. Since I intend to use this database on an iPhone I can't store NSImage objects directly. I wanted to use bindings and an NSValueTransformer subclass to handle the transcoding from the NSImage (obtained by an Image well on my GUI) to an NSData containing the PNG binary representation of the image. I wrote the following code for the ValueTransformer : + (Class)transformedValueClass { return [NSImage class]; } + (BOOL)allowsReverseTransformation { return YES; } - (id)transformedValue:(id)value { if (value == nil) return nil; return [[[NSImage alloc] initWithData:value] autorelease]; } - (id)reverseTransformedValue:(id)value { if (value == nil) return nil; if(![value isKindOfClass:[NSImage class]]) { NSLog(@"Type mismatch. Expecting NSImage"); } NSBitmapImageRep *bits = [[value representations] objectAtIndex: 0]; NSData *data = [bits representationUsingType:NSPNGFileType properties:nil]; return data; } The model has a transformable property configured with this NSValueTransformer. In Interface Builder a table column and an image well are both bound to this property and both have the proper value transformer name (an image dropped in the image well shows up in the table column). The transformer is registered and called every time an image is added or a row is reloaded (checked with NSLog() calls). The problem arises when I am trying to save the managed objects. The console output shows the error message : [NSImage length]: unrecognized selector sent to instance 0x1004933a0 It seems like core data is using the value transformer to obtain the NSImage back from the NSData and then tries to save the NSImage instead of the NSData. There are probably workarounds such as the one presented in this post but I would really like to understand why my approach is flawn. Thanks in advance for your ideas and explanations.

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• Ruby array, javascript and json issue

  - by JohnMerlino

  Hey all, I am unable to get a highcharts plugin to render a chart in a rails application: http://github.com/loudpixel/highcharts-rails I believe it has something to do with the sql queries to the database placed in a ruby array, which the javascript is unable to intepret. This is what I have: def panels pass = Student.find_by_sql('SELECT COUNT(*) FROM students WHERE student_state = 1') fail = Student.find_by_sql('SELECT COUNT(*) FROM students WHERE student_state = 2') student_data = [ {:name => 'Pass', :y => pass}, {:name => 'Fail', :y => fail} ] pie_label_formatter = ' function() { if (this.y > 15) return this.point.name; }' pie_tooltip_formatter = ' function() { return "<strong>" + this.point.name + "</strong>: " + this.y + " %"; }' @pie_chart = Highchart.pie({ :chart => { :renderTo => "pie-chart-container", :margin => [50, 30, 0, 30] }, :plotOptions => { :pie => { :dataLabels => { :formatter => pie_label_formatter, :style => { :textShadow => '#000000 1px 1px 2px' } } } }, :series => [ { :type => 'pie', :data => student_data } ], :subtitle => { :text => 'April 2010' }, :title => { :text => 'Student Status Chart' }, :tooltip => { :formatter => pie_tooltip_formatter }, }) Note if I put this: :data = student_data.to_json It actually returns a json string of my query as text in the browser. Also, if I hard code values (e.g. :y = 1), it will render the chart properly. However, any database query will not render the chart properly. So I'm not sure exactly what the issue is. Any suggestions? Thanks.

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• [ZF & jQuery] How can I access an URL using AJAX, receive no response, but just manipulate HTML?

  - by rasouza

  I don't know if it's better used with AJAX (tell me, otherwise) but here is my problem: Assuming i'm using Zend Framework, I have a table with several registries from a database with a delete button on each row. That's like this [...] <tbody> <?php foreach ($row as $reg) { ?> <tr <?php if ($reg['value'] < 0) { echo "class='error'"; } ?>> <td><?php echo $reg['creditor'] ?></td> <td><?php echo $reg['debtor'] ?></td> <td><?php echo $reg['reason'] ?></td> <td>R$ <?php echo number_format(abs($reg['value']), 2, ',', ' ')?></td> <td><a href="#" id="<?php echo $reg['id']; ?>" class="delete"><img src="http://192.168.0.102/libraries/css/blueprint/plugins/buttons/icons/cross.png" alt=""/></a></td> </tr> <?php } ?> </tbody> [...] I would like to .fadeOut() and delete (through the link history/delete/id/ROW_ID ) a table row when clicked in the respective delete button. My deleteAction() has no render. It really shouldn't have one, it just deletes a row in the database. Still, how can I make it happen? I tried: // TR Fading when deleted $('.delete') .click(function() { $.ajax({ type: 'GET', url: 'history/delete/id/'+$(this).attr('id'), success: function() { $(this).parent().parent().fadeOut(); } }); return false; }); without success

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• How do I create a dynamic data transfer object dynamically from ADO.net model

  - by Richard

  I have a pretty simple database with 5 tables, PK's and relationships setup, etc. I also have an ASP.net MVC3 project I'm using to create simple web services to feed JSON/XML to a mobile app using post/get. To access my data I'm using an ADO.net entity model class to handle generation of the entities, etc. Due to issues with serialization/circular references created by the auto-generated relations from ADO.net entity model, I've been forced to create "Data transfer objects" to strip out the relations and data that doesn't need to be transferred. Question 1: is there an easier way to create DTOs using the entity framework itself? IE, specify only the entity properties I want to convert to Jsonresults? I don't wish to use any 3rd party frameworks if I can help it. Question 2: A side question for Entity Framework, say I create an ADO.net entity model in one project within a solution. Because that model relies on the connection to the database specified in project A, can project B somehow use that model with a similar connection? Both projects are in the same solution. Thanks!

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• SQLAlchemy: select over multiple tables

  - by ahojnnes

  Hi, I wanted to optimize my database query: link_list = select( columns=[link_table.c.rating, link_table.c.url, link_table.c.donations_in], whereclause=and_( not_(link_table.c.id.in_( select( columns=[request_table.c.recipient], whereclause=request_table.c.donator==donator.id ).as_scalar() )), link_table.c.id!=donator.id, ), limit=20, ).execute().fetchall() and tried to merge those two selects in one query: link_list = select( columns=[link_table.c.rating, link_table.c.url, link_table.c.donations_in], whereclause=and_( link_table.c.active==True, link_table.c.id!=donator.id, request_table.c.donator==donator.id, link_table.c.id!=request_table.c.recipient, ), limit=20, order_by=[link_table.c.rating.desc()] ).execute().fetchall() the database-schema looks like: link_table = Table('links', metadata, Column('id', Integer, primary_key=True, autoincrement=True), Column('url', Unicode(250), index=True, unique=True), Column('registration_date', DateTime), Column('donations_in', Integer), Column('active', Boolean), ) request_table = Table('requests', metadata, Column('id', Integer, primary_key=True, autoincrement=True), Column('recipient', Integer, ForeignKey('links.id')), Column('donator', Integer, ForeignKey('links.id')), Column('date', DateTime), ) There are several links (donator) in request_table pointing to one link in the link_table. I want to have links from link_table, which are not yet "requested". But this does not work. Is it actually possible, what I'm trying to do? If so, how would you do that? Thank you very much in advance!

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• Why is it not good to use $_SESSION in Restful Implementations?

  - by keisimone

  Original Question: i read that for RESTful websites. it is not good to use $_SESSION. Why is it not good? how then do i properly authenticate users without looking up database all the time to check for the user's roles? I read that it is not good to use $_SESSION. http://www.recessframework.org/page/towards-restful-php-5-basic-tips I am creating a WEBSITE, not web service in PHP. and i am trying to make it more RESTful. at least in spirit. right now i am rewriting all the action to use Form tags POST and add in a hidden value called _method which would be "delete" for deleting action and "put" for updating action. however, i am not sure why it is recommended NOT to use $_SESSION. i would like to know why and what can i do to improve. To allow easy authorization checking, what i did was to after logging in the user, the username is stored in the $_SESSION. Everytime the user navigates to a page, the page would check if the username is stored inside $_SESSION and then based on the $_SESSION retrieves all the info including privileges from the database and then evaluates the authorization to access the page based on the info retrieved. Is the way I am implementing bad? not RESTful? how do i improve performance and security? Thank you.

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• Bidirectional replication update record problem

  - by Mirek

  Hi, I would like to present you my problem related to SQL Server 2005 bidirectional replication. What do I need? My teamleader wants to solve one of our problems using bidirectional replication between two databases, each used by different application. One application creates records in table A, changes should replicate to second database into a copy of table A. When data on second server are changed, then those changes have to be propagated back to the first server. I am trying to achieve bidirectional transactional replication between two databases on one server, which is running SQL Server 2005. I have manage to set this up using scripts, established 2 publications and 2 read only subscriptions with loopback detection. Distributtion database is created, publishment on both databases is enabled. Distributor and publisher are up. We are using some rules to control, which records will be replicated, so we need to call our custom stored procedures during replication. So, articles are set to use update, insert and delete custom stored procedures. So far so good, but? Everything works fine, changes are replicating, until updates are done on both tables simultaneously or before changes are replicated (and that takes about 3-6 seconds). Both records then end up with different values. UPDATE db1.dbo.TestTable SET Col = 4 WHERE ID = 1 UPDATE db2.dbo.TestTable SET Col = 5 WHERE ID = 1 results to: db1.dbo.TestTable COL = 5 db2.dbo.TestTable COL = 4 But we want to have last change winning replication. Please, is there a way to solve my problem? How can I ensure same values in both records? Or is there easier solution than this kind of replication? I can provide sample replication script which I am using. I am looking forward for you ideas, Mirek

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• Best way to test a Delphi application

  - by Osama ALASSIRY

  I have a Delphi application that has many dependencies, and it would be difficult to refactor it to use DUnit (it's huge), so I was thinking about using something like AutomatedQA's TestComplete to do the testing from the front-end UI. My main problem is that a bugfix or new feature sometimes breaks old code that was previously tested (manually), and used to work. I have setup the application to use command-line switches to open-up a specific form that could be tested, and I can create a set of values and clicks needed to be done. But I have a few questions before I do anything drastic... (and before purchasing anything) Is it worth it? Would this be a good way to test? The result of the test should in my database (Oracle), is there an easy way in testcomplete to check these values (multiple fields in multiple tables)? I would need to setup a test database to do all the automated testing, would there be an easy way to automate re-setting the test db? Other than drop user cascade, create user,..., impdp. Is there a way in testcomplete to specify command-line parameters for an exe? Does anybody have any similar experiences.

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• Why does Hibernate ignore the JPA2 standardized properties in my persistence.xml?

  - by Ophidian

  I have an extremely simple web application running in Tomcat using Spring 3.0.1, Hibernate 3.5.1, JPA 2, and Derby. I am defining all of my database connectivity in persistence.xml and merely using Spring for dependency injection. I am using embedded Derby as my database. Everything works correctly when I define the driver and url properties in persistence.xml in the classic Hibernate manner as thus: <property name="hibernate.connection.driver_class" value="org.apache.derby.jdbc.EmbeddedDriver"/> <property name="hibernate.connection.url" value="jdbc:derby:webdb;create=true"/> The problems occur when I switch my configuration to the JPA2 standardized properties as thus: <property name="javax.persistence.jdbc.driver" value="org.apache.derby.jdbc.EmbeddedDriver"/> <property name="javax.persistence.jdbc.url" value="jdbc:derby:webdb;create=true"/> When using the JPA2 property keys, the application bails hard with the following exception: java.lang.UnsupportedOperationException: The user must supply a JDBC connection Does anyone know why this is failing? NOTE: I have copied the javax... property strings straight from the Hibernate reference documentation, so a typo is extremely unlikely.

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• Undefined method `add' on a cucumber step that usually works.

  - by Josiah Kiehl

  I have a path defined: when /the admin home\s?page/ "/admin/" I have scenario that is passing: Scenario: Let admins see the admin homepage Given "pojo" is logged in And "pojo" is an "admin" And I am on the admin home page Then I should see "Hi there." And I have a scenario that is failing: Scenario: Review flagged photo Given "pojo" is logged in And "pojo" is an "admin" ...bunch of steps that create stuff in the database... And I am on the admin home page Then ... the rest of the steps The step that fails in the second one is "And I am on the admin home page" which passes just fine in the first scenario. Here's the error I get: And I am on the admin home page # features/step_definitions/web_steps.rb:18 undefined method `add' for {}:Hash (NoMethodError) ./app/controllers/admin_controller.rb:13:in `index' ./app/controllers/admin_controller.rb:11:in `each' ./app/controllers/admin_controller.rb:11:in `index' /usr/lib/ruby/1.8/benchmark.rb:308:in `realtime' ./features/step_definitions/web_steps.rb:19:in `/^(?:|I )am on (.+)$/' features/admin.feature:52:in `And I am on the admin home page' This is very odd... why would it be fine in the first case, and not in the second where the only difference are a bunch of steps that create records in the db? [edit] Here's the add stuff to database step: Given /^there is a "([^\"]*)" with the following:$/ do |model, table| model.constantize.create!(table.rows_hash) end

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• proper use of volatile keyword

  - by luke

  I think i have a pretty good idea about the volatile keyword in java, but i'm thinking about re-factoring some code and i thought it would be a good idea to use it. i have a class that is basically working as a DB Cache. it holds a bunch of objects that it has read from a database, serves requests for those objects, and then occasionally refreshes the database (based on a timeout). Heres the skeleton public class Cache { private HashMap mappings =....; private long last_update_time; private void loadMappingsFromDB() { //.... } private void checkLoad() { if(System.currentTimeMillis() - last_update_time > TIMEOUT) loadMappingsFromDB(); } public Data get(ID id) { checkLoad(); //.. look it up } } So the concern is that loadMappingsFromDB could be a high latency operation and thats not acceptable, So initially i thought that i could spin up a thread on cache startup and then just have it sleep and then update the cache in the background. But then i would need to synchronize my class (or the map). and then i would just be trading an occasional big pause for making every cache access slower. Then i thought why not use volatile i could define the map reference as volatile private volatile HashMap mappings =....; and then in get (or anywhere else that uses the mappings variable) i would just make a local copy of the reference: public Data get(ID id) { HashMap local = mappings; //.. look it up using local } and then the background thread would just load into a temp table and then swap the references in the class HashMap tmp; //load tmp from DB mappings = tmp;//swap variables forcing write barrier Does this approach make sense? and is it actually thread-safe?

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• General JDBC Setup

  - by AeroDroid

  So I have a MySQL database set up on a Debian server and it works fine from a phpMyAdmin client. I'm currently working on a project to write a Java server that would be able to use the MySQL database that is already on this server through a JDBC connection. I've looked at many tutorials and documentations but all of them seem to just explain how to do client-side code, but I have yet to figure out how to even successfully open a JDBC connection to the server. As far as I am concerned, I believe that program has the drivers properly set up because it's not crashing anymore (I simply direct the Java Build Path of my program to the Connector/J provided by MySQL). As far as my program goes, this is what it looks like... import java.sql.*; public class JDBCTest { public static void main(String[] args) { System.out.println("Started!"); try { DriverManager.registerDriver(new com.mysql.jdbc.Driver()); System.out.println("Driver registered. Connecting..."); Connection conn = DriverManager.getConnection("jdbc:mysql://localhost/", "root", "password"); System.out.println("Connected!"); conn.close(); } catch (SQLException e) { System.out.println("Error!"); e.printStackTrace(); } } } This is what's printed... Started! Driver registered. Connecting... It's as if the DriverManager.getConnection(String) just freezes there. I'm sure this is a problem with the server because when I intentionally misspell localhost, or an IP address, the program crashes within 20 seconds. This just hangs there forever. Sorry about this wall of text, but my final question is if anyone has any information what I should do or install on the server to get this to work? Thank you so much!

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• JSON Select option question?

  - by user303832

  Hello,I wrote somethinh like this, `$sql = "SELECT * FROM dbase"; $strOptions = ""; if (!$q=mysql_query($sql)) { $strOptions = "<option>There was an error connecting to database</option>"; } if (mysql_num_rows($q)==0) { $strOptions = "<option>There are no news in database</option>"; }else { $a=0; while ($redak=mysql_fetch_assoc($q)) { $a=$a+1; $vvvv[$a]["id"]=$redak["id"]; $vvvv[$a]["ssss"]=$redak["ssss"]; } } for ($i=1; $i<=$a; $i++) { $strOptions = $strOptions. '<option value="'. $vvvv[$i]["id"] .'">'.$i.'.) - '.strip_tags($vvvv[$i]["ssss"]).'</option>'; } echo '[{ "message": "3" },{ "message": "' . count($wpdb->get_results("SELECT * FROM dbase")) . '" },{ "message": "'.$strOptions .'"}]';` I just cannot later parse json file,later I parse it on this way to fill select-option $jq("#select-my").children().remove(); $jq("#select-my").append(data[2].message); I use jquery form pluing,everything work fine,except this,I cant parse data for select-option element.I try and with json_encode in php.Can someone help please?

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• Images from SQL Server JPG/PNG Image Column not being Type Converted to Bitmap in HttpHandlers (cons

  - by kanchirk

  Our Silverlight 3.0 Client consumes Images stored/retrieved on the File System thorough ASP.NET HttpHandlers successfully. We are trying to store and read back Images using a SQL Server 2008 Database. Please find the stripped down code pasted below with the Exception. "Bitmap is not Valid" //Store document to the database private void SaveImageToDatabaseKK(HttpContext context, string pImageFileName) { try { //ADO.NET Entity Framework ImageTable documentDB = new ImageTable(); int intLength = Convert.ToInt32(context.Request.InputStream.Length); //Move the file contents into the Byte array Byte[] arrContent = new Byte[intLength]; context.Request.InputStream.Read(arrContent, 0, intLength); //Insert record into the Document table documentDB.InsertDocument(pImageFileName, arrContent, intLength); } catch { } } =The method to Read Back the Row from the Table and Send it back is below.= private void RetrieveImageFromDatabaseTableKK(HttpContext context, string pImageName) { try { ImageTable documentDB = new ImageTable(); var docRow = documentDB.GetDocument(pImageName); //based on Imagename which is unique //DocData column in table is **Image** if (docRow!=null && docRow.DocData != null && docRow.DocData.Length > 0) { Byte[] bytImage = docRow.DocData; if (bytImage != null && bytImage.Length > 0) { Bitmap newBmp = ConvertToBitmap(context, bytImage ); if (newBmp != null) { newBmp.Save(context.Response.OutputStream, ImageFormat.Jpeg); newBmp.Dispose(); } } } } catch (Exception exRI) { } } // Convert byte array to Bitmap (byte[] to Bitmap) protected Bitmap ConvertToBitmap(byte[] bmp) { if (bmp != null) { try { TypeConverter tc = TypeDescriptor.GetConverter(typeof(Bitmap)); Bitmap b = (Bitmap)tc.ConvertFrom(bmp); **//This is where the Exception Occurs.** return b; } catch (Exception) { } } return null; }

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• How does real world login process happen in web application in Java?

  - by Nitesh Panchal

  Hello, I am very much confused regarding login process that happen in Java web application. I read many tutorials regarding jdbcRealm and JAAS. But, one thing that i don't understand is that why should i use them ? Can't i simply check directly against my database of users? and once they successfully login to the site, i store some variable in session as a flag. And probably check that session variable on all restricted pages (I mean keep a filter for restricted resources url pattern).If the flag doesn't exist simply redirect the user to login page. Is this approach correct?Does this approch sound correct? If yes, then why did all this JAAS and jdbcRealm came into existence? Secondly, I am trying to completely implement SAS(Software as service) in my web application, meaning everything is done through web services.If i use webservices, is it possible to use jdbcRealm? If not, then is it possible to use JAAS? If yes, then please show me some example which uses mySql as a database and then authenticates and authorizes. I even heard about Spring Security. But, i am confused about that too in the sense that how do i use webservice with Spring Security. Please help me. I am really very confused. I read sun's tutorials but they only keep talking about theories. For programmers to understand a simple concept, they show a 100 page theory first before they finally come to one example.

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• How to cache pages using background jobs ?

  - by Alexandre

  Definitions: resource = collection of database records, regeneration = processing these records and outputting the corresponding html Current flow: Receive client request Check for resource in cache If not in cache or cache expired, regenerate Return result The problem is that the regeneration step can tie up a single server process for 10-15 seconds. If a couple of users request the same resource, that could result in a couple of processes regenerating the exact same resource simultaneously, each taking up 10-15 seconds. Wouldn't it be preferrable to have the frontend signal some background process saying "Hey, regenerate this resource for me". But then what would it display to the user? "Rebuilding" is not acceptable. All resources would have to be in cache ahead of time. This could be a problem as the database would almost be duplicated on the filesystem (too big to fit in memory). Is there a way to avoid this? Not ideal, but it seems like the only way out. But then there's one more problem. How to keep the same two processes from requesting the regeneration of a resource at the same time? The background process could be regenerating the resource when a frontend asks for the regeneration of the same resource. I'm using PHP and the Zend Framework just in case someone wants to offer a platform-specific solution. Not that it matters though - I think this problem applies to any language/framework. Thanks!

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• g++ problem with -l option and PostgreSQL

  - by difek

  Hi I've written simple program. Here a code: #include <iostream> #include <stdio.h> #include <D:\Program Files\PostgreSQL\8.4\include\libpq-fe.h> #include <string> using namespace std; int main() { PGconn *conn; PGresult *res; int rec_count; int row; int col; cout << "ble ble: " << 8 << endl; conn = PQconnectdb("dbname=db_pm host=localhost user=postgres password=postgres"); if (PQstatus(conn) == CONNECTION_BAD) { puts("We were unable to connect to the database"); exit(0); } } I'm trying to connect with PostgreSQL. I compile this code with following command: gcc -I/"d:\Program Files\PostgreSQL\" -L/"d:\Program Files\PostgreSQL\8.4\lib\" -lpq -o firstcpp.o firstcpp.cpp This command is from following site: http://www.mkyong.com/database/how-to-building-postgresql-libpq-programs/ And when I compile it I get following error: /cygnus/cygwin-b20/H-i586-cygwin32/i586-cygwin32/bin/ld: cannot open -lpq: No such file or directory collect2: ld returned 1 exit status Does anyone help me? Difek

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• django class with an array of "parent" foreignkeys issue

  - by user298032

  Let's say I have a class called Fruit with child classes of the different kinds of Fruit with their own specific attributes, and I want to collect them in a FruitBasket: class Fruit(models.Model):     type = models.CharField(max_length=120,default='banana',choices=FRUIT_TYPES)     ... class Banana(Fruit):     """banana (fruit type)"""     length = models.IntegerField(blank=True, null=True)     ... class Orange(Fruit):     """orange (fruit type)"""     diameter = models.IntegerField(blank=True, null=True)     ... class FruitBasket(models.Model):     fruits = models.ManyToManyField(Fruit)     ... The problem I seem to be having is when I retrieve and inspect the Fruits in a FruitBasket, I only retrieve the Fruit base class and can't get at the Fruit child class attributes. I think I understand what is happening--when the array is retrieved from the database, the only fields that are retrieved are the Fruit base class fields. But is there some way to get the child class attributes as well without multiple expensive database transactions? (For example, I could get the array, then retrieve the child Fruit classes by the id of each array element). thanks in advance, Chuck

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• What's the most DRY-appropriate way to execute an SQL command?

  - by Sean U

  I'm looking to figure out the best way to execute a database query using the least amount of boilerplate code. The method suggested in the SqlCommand documentation: private static void ReadOrderData(string connectionString) { string queryString = "SELECT OrderID, CustomerID FROM dbo.Orders;"; using (SqlConnection connection = new SqlConnection(connectionString)) { SqlCommand command = new SqlCommand(queryString, connection); connection.Open(); SqlDataReader reader = command.ExecuteReader(); try { while (reader.Read()) { Console.WriteLine(String.Format("{0}, {1}", reader[0], reader[1])); } } finally { reader.Close(); } } } mostly consists of code that would have to be repeated in every method that interacts with the database. I'm already in the habit of factoring out the establishment of a connection, which would yield code more like the following. (I'm also modifying it so that it returns data, in order to make the example a bit less trivial.) private SQLConnection CreateConnection() { var connection = new SqlConnection(_connectionString); connection.Open(); return connection; } private List<int> ReadOrderData() { using(var connection = CreateConnection()) using(var command = connection.CreateCommand()) { command.CommandText = "SELECT OrderID FROM dbo.Orders;"; using(var reader = command.ExecuteReader()) { var results = new List<int>(); while(reader.Read()) results.Add(reader.GetInt32(0)); return results; } } } That's an improvement, but there's still enough boilerplate to nag at me. Can this be reduced further? In particular, I'd like to do something about the first two lines of the procedure. I don't feel like the method should be in charge of creating the SqlCommand. It's a tiny piece of repetition as it is in the example, but it seems to grow if transactions are being managed manually or timeouts are being altered or anything like that.

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• ASP.NET retrieve Average CPU Usage

  - by Sam

  Last night I did a load test on a site. I found that one of my shared caches is a bottleneck. I'm using a ReaderWriterLockSlim to control the updates of the data. Unfortunately at one point there are ~200 requests trying to update the data at approximately the same time. This also coincided with CPU usage spikes. The data being updated is in the ASP.NET Cache. What I'd like to do is if the CPU usage is around 75%, I'd like to just skip the cache and hit the database on another machine. My problem is that I don't know how expensive it is to create a new performance counter to check the cpu usage. Also, if I would probably like the average cpu usage over the last 2 or 3 seconds. However, I can't sit there and calculate the cpu time as that would take longer than it's taking to update the cache currently. Is there an easy way to get the average CPU usage? Are there any drawbacks to this? I'm also considering totaling the wait count for the lock and then at a certain threshold switch over to the database. The concern I had with this approach would be that changing hardware might allow more locks with less of a strain on the system. And also finding the right balance for the threshold would be cumbersome and it doesn't take into account any other load on the machine. But it's a simple approach, and simple is 99% of the time better.

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• How to reuse results with a schema for end of day stock-data

  - by Vishalrix

  I am creating a database schema to be used for technical analysis like top-volume gainers, top-price gainers etc.I have checked answers to questions here, like the design question. Having taken the hint from boe100 's answer there I have a schema modeled pretty much on it, thusly: Symbol - char 6 //primary Date - date //primary Open - decimal 18, 4 High - decimal 18, 4 Low - decimal 18, 4 Close - decimal 18, 4 Volume - int Right now this table containing End Of Day( EOD) data will be about 3 million rows for 3 years. Later when I get/need more data it could be 20 million rows. The front end will be asking requests like "give me the top price gainers on date X over Y days". That request is one of the simpler ones, and as such is not too costly, time wise, I assume. But a request like " give me top volume gainers for the last 10 days, with the previous 100 days acting as baseline", could prove 10-100 times costlier. The result of such a request would be a float which signifies how many times the volume as grown etc. One option I have is adding a column for each such result. And if the user asks for volume gain in 10 days over 20 days, that would require another table. The total such tables could easily cross 100, specially if I start using other results as tables, like MACD-10, MACD-100. each of which will require its own column. Is this a feasible solution? Another option being that I keep the result in cached html files and present them to the user. I dont have much experience in web-development, so to me it looks messy; but I could be wrong ( ofc!) . Is that a option too? Let me add that I am/will be using mod_perl to present the response to the user. With much of the work on mysql database being done using perl. I would like to have a response time of 1-2 seconds.

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• How much does Website Development cost nowadays?

  - by Andreas Grech

  I am thinking of setting up my own freelance business but coming from a workplace that offers a particular service to huge clients, I do not know what are the current charges for websites are nowadays. I know that as technology just keeps changing and changing (most of the time, for the better...), the amount you charge for a single website is constantly differing. Like for example, I don't think static websites (with just static html pages) are that expensive today, no? (as i said, I might be mistaken since I haven't really touched on this freelance industry yet) So, freelance web-developers out there, can you give me estimates on how much you charge for your clients? Some examples of websites that I want to know an approx charge: ~10 static html pages ~10 dhtml pages (with maybe a flasy menu on the top/side) Database driven websites with a standard CMS (be it the one you developed, or an existing one) Database driven but with a custom-built cms for the particular client Using an existing template for a design Starting the design from scratch etc... I know that the normally clients don't really care about the technologies used to construct their websites, but do you charge differently according to which technology you use to build the website with?; as in, is the technology a factor when setting the price? ...being ASP.Net, PHP, Ruby On Rails etc... Also, how do you go on about charging your clients for your services? What are the major factors that you consider when setting a price tag for a website to a client ? And better yet, how do you even find prospective clients? <= [or should I leave this question for a different post?] Btw, in your post, also mention some numbers (in cash values, be it in USD, GBP, EUR or anything) because I want to be able to take calculate some averages from this post when some answers stack up

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• Running migration on server when deploying with capistrano

  - by Pandafox

  Hi, I'm trying to deploy my rails application with capistrano, but I'm having some trouble running my migrations. In my development environment I just use sqlite as my database, but on my production server I use MySQL. The problem is that I want the migrations to run from my server and not my local machine, as I am not able to connect to my database from a remote location. My server setup: A debian box running ngnix, passenger, mysql and a git repository. What is the easiest way to do this? update: Here's my deploy script: set :application, "example.com" set :domain, "example.com" set :scm, :git set :repository, "[email protected]:project.git" set :use_sudo, false set :deploy_to, "/var/www/example.com" role :web, domain role :app, domain role :db, "localhost", :primary = true after "deploy", "deploy:migrate" When I run cap deploy, everything is working fine until it tries to run the migration. Here's the error I'm getting: ** [deploy:update_code] exception while rolling back: Capistrano::ConnectionError, connection failed for: localhost (Errno::ECONNREFUSED: Connection refused - connect(2)) connection failed for: localhost (Errno::ECONNREFUSED: Connection refused - connect(2))) This is why I need to run the migration from the server and not from my local machine. Any ideas?

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• does sfWidgetFormSelect provide a string or an int of the selected item?

  - by han

  Hey guys, I'm having an annoying problem. I'm trying to find out what fields of a form were changed, and then insert that into a table. I managed to var_dump in doUpdateObjectas shown in the following public function doUpdateObject($values) { parent::doUpdateObject($values); var_dump($this->getObject()->getModified(false)); var_dump($this->getObject()->getModified(true)); } And it seems like $this-getObject()-getModified seems to work in giving me both before and after values by setting it to either true or false. The problem that I'm facing right now is that, some how, sfWidgetFormSelect seems to be saving one of my fields as a string. before saving, that exact same field was an int. (I got this idea by var_dump both before and after). Here is what the results on both var dumps showed: array(1) {["annoying_field"]=> int(3)} array(1) {["annoying_field"]=>string(1)"3"} This seems to cause doctrine to think that this is a modification and thus gives a false positive. In my base form, I have under $this->getWidgets() 'annoying_field' => new sfWidgetFormInputText(), under $this->setValidators 'annoying_field' => new sfValidatorInteger(array('required' => false)), and lastly in my configured Form.class.php I have reconfigured the file as such: $this->widgetSchema['annoying_field'] = new sfWidgetFormSelect(array('choices' => $statuses)); statuses is an array containing values like {""a", "b", "c", "d"} and I just want the index of the status to be stored in the database. And also how can I insert the changes into another database table? let's say my Log table? Any ideas and advice as to why this is happen is appreciated, I've been trying to figure it out and browsing google for various keywords with no avail. Thanks! Edit: ok so I created another field, integer in my schema just for testing. I created an entry, saved it, and edited it. this time the same thing happened!

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