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  • Problems by inserting values from textboxes

    - by simon
    I'm trying to insert the current date to the database and i allways get the message(when i press the button on the form to save to my access database), that the data type is incorect in the conditional expression. the code: string conString = "Provider=Microsoft.Jet.OLEDB.4.0;" + "Data Source=C:\\Users\\Simon\\Desktop\\save.mdb"; OleDbConnection empConnection = new OleDbConnection(conString); string insertStatement = "INSERT INTO obroki_save " + "([ID_uporabnika],[ID_zivila],[skupaj_kalorij]) " + "VALUES (@ID_uporabnika,@ID_zivila,@skupaj_kalorij)"; OleDbCommand insertCommand = new OleDbCommand(insertStatement, empConnection); insertCommand.Parameters.Add("@ID_uporabnika", OleDbType.Char).Value = users.iDTextBox.Text; insertCommand.Parameters.Add("@ID_zivila", OleDbType.Char).Value = iDTextBox.Text; insertCommand.Parameters.Add("@skupaj_kalorij", OleDbType.Char).Value = textBox1.Text; empConnection.Open(); try { int count = insertCommand.ExecuteNonQuery(); } catch (OleDbException ex) { MessageBox.Show(ex.Message); } finally { empConnection.Close(); textBox1.Clear(); textBox2.Clear(); textBox3.Clear(); textBox4.Clear(); textBox5.Clear(); } I have now cut out the date,( i made access paste the date ), still there is the same problem. Is the first line ok? users.idtextbox.text? Please help !

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  • Is the RESTORE process dependent on schema?

    - by Martin Aatmaa
    Let's say I have two database instances: InstanceA - Production server InstanceB - Test server My workflow is to deploy new schema changes to InstanceB first, test them, and then deploy them to InstanceA. So, at any one time, the instance schema relationship looks like this: InstanceA - Schema Version 1.5 InstanceB - Schema Version 1.6 (new version being tested) An additional part of my workflow is to keep the data in InstanceB as fresh as possible. To fulfill this, I am taking the database backups of InstanceA and applying them (restoring them) to InstanceB. My question is, how does schema version affect the restoral process? I know I can do this: Backup InstanceA - Schema Version 1.5 Restore to InstanceB - Schema Version 1.5 But can I do this? Backup InstanceA - Schema Version 1.5 Restore to InstanceB - Schema Version 1.6 (new version being tested) If no, what would the failure look like? If yes, would the type of schema change matter? For example, if Schema Version 1.6 differed from Schema Version 1.5 by just having an altered storec proc, I imagine that this type of schema change should't affect the restoral process. On the other hand, if Schema Version 1.6 differed from Schema Version 1.5 by having a different table definition (say, an additional column), I image this would affect the restoral process. I hope I've made this clear enough. Thanks in advance for any input!

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  • Multiple threads modifying a collection in Java??

    - by posdef
    Hi, The project I am working on requires a whole bunch of queries towards a database. In principle there are two types of queries I am using: read from excel file, check for a couple of parameters and do a query for hits in the database. These hits are then registered as a series of custom classes. Any hit may (and most likely will) occur more than once so this part of the code checks and updates the occurrence in a custom list implementation that extends ArrayList. for each hit found, do a detail query and parse the output, so that the classes created in (I) get detailed info. I figured I would use multiple threads to optimize time-wise. However I can't really come up with a good way to solve the problem that occurs with the collection these items are stored in. To elaborate a little bit; throughout the execution objects are supposed to be modified by both (I) and (II). I deliberately didn't c/p any code, as it would be big chunks of code to make any sense.. I hope it make some sense with the description above. Thanks,

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  • Generate an ID via COM interop

    - by Erik van Brakel
    At the moment, we've got an unmaintanable ball of code which offers an interface to a third party application. The third party application has a COM assembly which MUST be used to create new entries. This process involves two steps: generate a new object (basically an ID), and update that object with new field values. Because COM interop is so slow, we only use that to generate the ID (and related objects) in the database. The actual update is done using a regular SQL query. What I am trying to figure out if it's possible to use NHibernate to do some of the heavy lifting for us, without bypassing the COM assembly. Here's the code for saving something to the database as I envision it: using(var s = sessionFactory.OpenSession()) using(var t = s.BeginTransaction()) { MyEntity entity = new MyEntity(); s.Save(entity); t.Commit(); } Regular NH code I'd say. Now, this is where it gets tricky. I think I have to supply my own implementation of NHibernate.Id.IIdentifierGenerator which calls the COM assembly in the Generate method. That's not a problem. What IS a problem is that the COM assembly requires initialisation, which does take a bit of time. It also doesn't like multiple instances in the same process, for some reason. What I would like to know is if there's a way to properly access an external service in the generator code. I'm free to use any technique I want, so if it involves something like an IoC container that's no problem. The thing I am looking for is where exactly to hook-up my code so I can access the things I need in my generator, without having to resort to using singletons or other nasty stuff.

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  • Extensionless URLs in IIS 6

    - by Jason Marsell
    My client has asked me to build a personalized URL system so that they can send out really short URLs in postcards to customers like this: www.client.com/JasonSmith03 www.client.com/TonyAdams With these URLs, I need IIS 6 to trap the incoming request and pass that “JasonSmith03” token to my database to determine which landing page to redirect them to. I’d love to use an HttpHandler or HttpModule but they both look like they require an file extension (.aspx) in the URL. Wildcard mapping will chew up every incoming request and that’s ridiculous. ISAPI filters are just text routing files, so I can’t employ logic to call the database. According to Scott Guthrie, this would be cake if I had IIS 7, but I don’t. Can this be done using MVC? I’ve been working with MVP for the last few years, so I haven’t done any MVC and routing. I thought I remembered that MVC has the ability to use REST-style extensionless URLs. I’d be more than happy to have these personalized URLs land on a site that’s built in MVC, if it will work. Thank you!

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  • Copy SQL Server data from one server to another on a schedule

    - by rwmnau
    I have a pair of SQL Servers at different webhosts, and I'm looking for a way to periodically update the one server using the other. Here's what I'm looking for: As automated as possible - ideally, without any involvement on my part once it's set up. Pushes a number of databases, in their entirely (including any schema changes) from one server to the other Freely allows changes on the source server without breaking my process. For this reason, I don't want to use replication, as I'd have to break it every time there's an update on the source, and then recreate the publication and subscription One database is about 4GB in size and contains binary data. I'm not sure if there's a way to export this to a script, but it would be a mammoth file if I did. Originally, I was thinking of writing something that takes a scheduled full backup of each database, FTPs the backups from one server to the other once they're done, and then the new server picks it up and restores it. The only downside I can see to this is that there's no way to know that the backups are done before starting to transfer them - can these backups be done synchronously? Also, the server being refreshes is our test server, so if there's some downtime involved in moving the data, that's fine. Does anybody out there have a better idea, or is what I'm currently considering the best non-replication way to go? Thanks for your help, everybody. UPDATE: I ended up designing a custom solution to get this done using BAT files, 7Zip,command line FTP, and OSQL, so it runs in a completely automatic way and aggregates the data from a dozen servers across the country. I've detailed the steps in a blog entry. Thanks for all your input!

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  • how to changed editext values from first to last in customise listview in android

    - by prakash
    i am getting menunames from database then append to the custom listview edittext . now i am changing some values in edittext . i want all values with changed values of edittext into array Example :x,y,z menunames comes from database i append editext(Custom listview) now i am changed y to b now i want x,b,z in arraylist i try this code(Base adapter class) public View getView(int position, View convertView, ViewGroup parent) { final ViewHolder holder; if (convertView == null) { holder = new ViewHolder(); convertView = inflater.inflate(R.layout.editmainmenulist, null); holder.caption = (EditText) convertView .findViewById(R.id.editmaimenu); holder.caption1=(ImageView) convertView.findViewById(R.id.menuimage); convertView.setTag(holder); } else { holder = (ViewHolder) convertView.getTag(); } //Fill EditText with the value you have in data source holder.caption.setText(itemnames[position]); holder.caption.setId(position); holder.caption1.setImageBitmap(bmps[position]); arr.add(holder.caption.getText().toString());//here i get menunames data only not changed edittext values return convertView; } } class ViewHolder { EditText caption; ImageView caption1; } class ListItem { String caption; } please help me

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  • Find out which row caused the error

    - by Felipe Fiali
    I have a big fat query that's written dynamically to integrate some data. Basically what it does is query some tables, join some other ones, treat some data, and then insert it into a final table. The problem is that there's too much data, and we can't really trust the sources, because there could be some errored or inconsistent data. For example, I've spent almost an hour looking for an error while developing using a customer's database because somewhere in the middle of my big fat query there was an error converting some varchar to datetime. It turned out to be that they had some sales dating '2009-02-29', an out-of-range date. And yes, I know. Why was that stored as varchar? Well, the source database has 3 columns for dates, 'Month', 'Day' and 'Year'. I have no idea why it's like that, but still, it is. But how the hell would I treat that, if the source is not trustable? I can't HANDLE exceptions, I really need that it comes up to another level with the original message, but I wanted to provide some more info, so that the user could at least try to solve it before calling us. So I thought about displaying to the user the row number, or some ID that would at least give him some idea of what record he'd have to correct. That's also a hard job because there will be times when the integration will run up to 80000 records. And in an 80000 records integration, a single dummy error message: 'The conversion of a varchar data type to a datetime data type resulted in an out-of-range datetime value' means nothing at all. So any idea would be appreciated. Oh I'm using SQL Server 2005 with Service Pack 3.

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  • Using Client Application Services in windows forms not working

    - by Nickson
    i am trying to implement asp.net membership, profile and role based security in a windows application by configuring client Application Services for my windows forms application. I have followed both these articles http://www.dotnetbips.com/articles/e863aa3c-0dd6-468d-bd35-120a334c5030.aspx and http://msdn.microsoft.com/en-us/library/bb546195.aspx step-by-step but for some reason i can't get the authentication working. I have a deployed intranet asp.net website which is already using an asp.net membership database for authentication and want to use that same database for authenitcation in my windows forms application. The site URL is http://myServer_Name:My_Port and i am specifying that URL as the both the Authentication service location and Roles service location in the windows application services property tab. But in the windows application login form, when i say Dim msg As String = "Welcome " If Not Membership.ValidateUser(UsernameTextBox.Text), PasswordTextBox.Text)) Then MessageBox.Show("Invalid User ID or Password!") Else msg = msg + UsernameTextBox.Text End If i get my "Invalid User ID or Password!" message even when i supply a valid user name with the corresponding password. i am able to login with the same credentials from the asp.net site. How can i test if the Authentication service location is being reached from the windows application?? Or what other information can i provide here such that one is able to help me get this working??

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  • multithreading issue

    - by vbNewbie
    I have written a multithreaded crawler and the process is simply creating threads and having them access a list of urls to crawl. They then access the urls and parse the html content. All this seems to work fine. Now when I need to write to tables in a database is when I experience issues. I have 2 declared arraylists that will contain the content each thread parse. The first arraylist is simply the rss feed links and the other arraylist contains the different posts. I then use a for each loop to iterate one while sequentially incrementing the other and writing to the database. My problem is that each time a new thread accesses one of the lists the content is changed and this affects the iteration. I tried using nested loops but it did not work before and this works fine using a single thread.I hope this makes sense. Here is my code: SyncLock dlock For Each l As String In links finallinks.Add(l) Next End SyncLock SyncLock dlock For Each p As String In posts finalposts.Add(p) Next End SyncLock ... Dim i As Integer = 0 SyncLock dlock For Each rsslink As String In finallinks postlink = finalposts.Item(i) i = i + 1 finallinks and finalposts are the two arraylists. I did not include the rest of the code which shows the threads working but this is the essential part where my error occurs which is basically here postlink = finalposts.Item(i) i = i + 1 ERROR: index was out of range. Must be non-negative and less than the size of the collection Is there an alternative?

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  • retrieving object information with Doctrine

    - by ajsie
    i want to fetch information from the database using objects. i really like this approach cause this is more OOP: $user = Doctrine_Core::getTable('User')->find(1); echo $user->Email['address']; echo $user->Phonenumbers[0]->phonenumber; rather than: $q = Doctrine_Query::create() ->from('User u') ->leftJoin('u.Email e') ->leftJoin('u.Phonenumbers p') ->where('u.id = ?', 1); $user = $q->fetchOne(); echo $user->Email['address']; echo $user->Phonenumbers[0]['phonenumber']; the problem is that the first one uses 3 queries (3 different tables), while the second one uses only 1 (and is therefore recommended technique). but i feel that it destroys the object oriented design. cause ORM is meant to give us an OOP approach so that we could focus on objects and not the relational database. but now they want us to go back to use SQL like pattern. there isn't a way to get information form multiple tables not using DQL? the above examples are taken from the documentation: doctrine

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  • Passing an ActionScript JPG Byte Array to Javscript (and eventually to PHP)

    - by Gus
    Our web application has a feature which uses Flash (AS3) to take photos using the user's web cam, then passes the resulting byte array to PHP where it is reconstructed and saved on the server. However, we need to be able to take this web application offline, and we have chosen Gears to do so. The user takes the app offline, performs his tasks, then when he's reconnected to the server, we "sync" the data back with our central database. We don't have PHP to interact with Flash anymore, but we still need to allow users to take and save photos. We don't know how to save a JPG that Flash creates in a local database. Our hope was that we could save the byte array, a serialized string, or somehow actually persist the object itself, then pass it back to either PHP or Flash (and then PHP) to recreate the JPG. We have tried: - passing the byte array to Javascript instead of PHP, but javascript doesn't seem to be able to do anything with it (the object seems to be stripped of its methods) - stringifying the byte array in Flash, and then passing it to Javascript, but we always get the same string: ÿØÿà Now we are thinking of serializing the string in Flash, passing it to Javascript, then on the return route, passing that string back to Flash which will then pass it to PHP to be reconstructed as a JPG. (whew). Since no one on our team has extensive Flash background, we're a bit lost. Is serialization the way to go? Is there a more realistic way to do this? Does anyone have any experience with this sort of thing? Perhaps we can build a javascript class that is the same as the byte array class in AS?

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  • Pros/cons of reading connection string from physical file vs Application object (ASP.NET)?

    - by HaterTot
    my ASP.NET application reads an xml file to determine which environment it's currently in (e.g. local, development, production). It checks this file every single time it opens a connection to the database, in order to know which connection string to grab from the Application Settings. I'm entering a phase of development where efficiency is becoming a concern. I don't think it's a good idea to have to read a file on a physical disk ever single time I wish to access the database (very often). I was considering storing the connection string in Application["ConnectionString"]. So the code would be public static string GetConnectionString { if (Application["ConnectionString"] == null) { XmlDocument doc = new XmlDocument(); doc.Load(HttpContext.Current.Request.PhysicalApplicationPath + "bin/ServerEnvironment.xml"); XmlElement xe = (XmlElement) xnl[0]; switch (xe.InnerText.ToString().ToLower()) { case "local": connString = Settings.Default.ConnectionStringLocal; break; case "development": connString = Settings.Default.ConnectionStringDevelopment; break; case "production": connString = Settings.Default.ConnectionStringProduction; break; default: throw new Exception("no connection string defined"); } Application["ConnectionString"] = connString; } return Application["ConnectionString"].ToString(); } I didn't design the application so I figure there must have been a reason for reading the xml file every time (to change settings while the application runs?) I have very little concept of the inner workings here. What are the pros and cons? Do you think I'd see a small performance gain by implementing the function above? THANKS

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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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  • [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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  • 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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  • How do I view the full content of a text or varchar(MAX) column in SQL Server 2008 Management Studio

    - by adamjford
    In this live SQL Server 2008 (build 10.0.1600) database, there's an Events table, which contains a text column named Details. (Yes, I realize this should actually be a varchar(MAX) column, but whoever set this database up did not do it that way.) This column contains very large logs of exceptions and associated JSON data that I'm trying to access through SQL Server Management Studio, but whenever I copy the results from the grid to a text editor, it truncates it at 43679 characters. I've read on various locations on the Internet that you can set your Maximum Characters Retrieved for XML Data in Tools > Options > Query Results > SQL Server > Results To Grid to Unlimited, and then perform a query such as this: select Convert(xml, Details) from Events where EventID = 13920 (Note that the data is column is not XML at all. CONVERTing the column to XML is merely a workaround I found from Googling that someone else has used to get around the limit SSMS has from retrieving data from a text or varchar(MAX) column.) However, after setting the option above, running the query, and clicking on the link in the result, I still get the following error: Unable to show XML. The following error happened: Unexpected end of file has occurred. Line 5, position 220160. One solution is to increase the number of characters retrieved from the server for XML data. To change this setting, on the Tools menu, click Options. So, any idea on how to access this data? Would converting the column to varchar(MAX) fix my woes?

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  • SQL Query to return maximums over decades

    - by Abraham Lincoln
    My question is the following. I have a baseball database, and in that baseball database there is a master table which lists every player that has ever played. There is also a batting table, which tracks every players' batting statistics. I created a view to join those two together; hence the masterplusbatting table. CREATE TABLE `Master` ( `lahmanID` int(9) NOT NULL auto_increment, `playerID` varchar(10) NOT NULL default '', `nameFirst` varchar(50) default NULL, `nameLast` varchar(50) NOT NULL default '', PRIMARY KEY (`lahmanID`), KEY `playerID` (`playerID`), ) ENGINE=MyISAM AUTO_INCREMENT=18968 DEFAULT CHARSET=latin1; CREATE TABLE `Batting` ( `playerID` varchar(9) NOT NULL default '', `yearID` smallint(4) unsigned NOT NULL default '0', `teamID` char(3) NOT NULL default '', `lgID` char(2) NOT NULL default '', `HR` smallint(3) unsigned default NULL, PRIMARY KEY (`playerID`,`yearID`,`stint`), KEY `playerID` (`playerID`), KEY `team` (`teamID`,`yearID`,`lgID`) ) ENGINE=MyISAM DEFAULT CHARSET=latin1; Anyway, my first query involved finding the most home runs hit every year since baseball began, including ties. The query to do that is the following.... select f.yearID, f.nameFirst, f.nameLast, f.HR from ( select yearID, max(HR) as HOMERS from masterplusbatting group by yearID )as x inner join masterplusbatting as f on f.yearID = x.yearId and f.HR = x.HOMERS This worked great. However, I now want to find the highest HR hitter in each decade since baseball began. Here is what I tried. select f.yearID, truncate(f.yearid/10,0) as decade,f.nameFirst, f.nameLast, f.HR from ( select yearID, max(HR) as HOMERS from masterplusbatting group by yearID )as x inner join masterplusbatting as f on f.yearID = x.yearId and f.HR = x.HOMERS group by decade You can see that I truncated the yearID in order to get 187, 188, 189 etc instead of 1897, 1885,. I then grouped by the decade, thinking that it would give me the highest per decade, but it is not returning the correct values. For example, it's giving me Adrian Beltre with 48 HR's in 2004 but everyone knows that Barry Bonds hit 73 HR in 2001. Can anyone give me some pointers?

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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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  • 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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  • 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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  • 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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  • 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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  • 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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