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• What are the best practices for storing PHP session data in a database?

  - by undefined

  I have developed a web application that uses a web server and database hosted by a web host (on the ground) and a server running on Amazon Web Services EC2. Both servers may be used by a user during a session and both will need to know some session information about a user. I don't want to POST the information that is needed by both servers because I dont want it to be visible to browsers / Firebug etc. So I need my session data to persist across servers. And I think that this means that the best option is to store all / some of the data that I need in the database rather than in a session. The easiest thing to do seems to be to keep the sessions but to POST the session_id between servers and use this as the key to lookup the data I need from a 'user_session_data' table in the database. I have looked at Tony Marston's article "Saving PHP Session Data to a database" - should I use this or will a table with the session data that I need and session_id as key suffice? What would be the downside of creating my own table and set of methods for storing the data I need in the database?

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• How to design data storage for partitioned tagging system?

  - by Morgan Cheng

  How to design data storage for huge tagging system (like digg or delicious)? There is already discussion about it, but it is about centralized database. Since the data is supposed to grow, we'll need to partition the data into multiple shards soon or later. So, the question turns to be: How to design data storage for partitioned tagging system? The tagging system basically has 3 tables: Item (item_id, item_content) Tag (tag_id, tag_title) TagMapping(map_id, tag_id, item_id) That works fine for finding all items for given tag and finding all tags for given item, if the table is stored in one database instance. If we need to partition the data into multiple database instances, it is not that easy. For table Item, we can partition its content with its key item_id. For table Tag, we can partition its content with its key tag_id. For example, we want to partition table Tag into K databases. We can simply choose number (tag_id % K) database to store given tag. But, how to partition table TagMapping? The TagMapping table represents the many-to-many relationship. I can only image to have duplication. That is, same content of TagMappping has two copies. One is partitioned with tag_id and the other is partitioned with item_id. In scenario to find tags for given item, we use partition with tag_id. If scenario to find items for given tag, we use partition with item_id. As a result, there is data redundancy. And, the application level should keep the consistency of all tables. It looks hard. Is there any better solution to solve this many-to-many partition problem?

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• Python : How to close a UDP socket while is waiting for data in recv ?

  - by alexroat

  Hello, let's consider this code in python: import socket import threading import sys import select class UDPServer: def __init__(self): self.s=None self.t=None def start(self,port=8888): if not self.s: self.s=socket.socket(socket.AF_INET, socket.SOCK_DGRAM) self.s.bind(("",port)) self.t=threading.Thread(target=self.run) self.t.start() def stop(self): if self.s: self.s.close() self.t.join() self.t=None def run(self): while True: try: #receive data data,addr=self.s.recvfrom(1024) self.onPacket(addr,data) except: break self.s=None def onPacket(self,addr,data): print addr,data us=UDPServer() while True: sys.stdout.write("UDP server> ") cmd=sys.stdin.readline() if cmd=="start\n": print "starting server..." us.start(8888) print "done" elif cmd=="stop\n": print "stopping server..." us.stop() print "done" elif cmd=="quit\n": print "Quitting ..." us.stop() break; print "bye bye" It runs an interactive shell with which I can start and stop an UDP server. The server is implemented through a class which launches a thread in which there's a infinite loop of recv/*onPacket* callback inside a try/except block which should detect the error and the exits from the loop. What I expect is that when I type "stop" on the shell the socket is closed and an exception is raised by the recvfrom function because of the invalidation of the file descriptor. Instead, it seems that recvfrom still to block the thread waiting for data even after the close call. Why this strange behavior ? I've always used this patter to implements an UDP server in C++ and JAVA and it always worked. I've tried also with a "select" passing a list with the socket to the xread argument, in order to get an event of file descriptor disruption from select instead that from recvfrom, but select seems to be "insensible" to the close too. I need to have a unique code which maintain the same behavior on Linux and Windows with python 2.5 - 2.6. Thanks.

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• How to build a windows/web application that stores data locally and sync's with remote database?

  - by Jason

  Hello, I am needing to build an application that stores data locally and then synchronizes with a remote MS SQL database. I am not sure how to go about doing this. Enter data offline on a form and store the data. Synchronize the data with a remote MS SQL database when online. There will be many users who enter data offline, the local database on each pc needs to update when online and grab the 30 most recent records for use offline. Example: Each day users will enter data on their "form". The users will be offline. The users will return to the office and need to sync with the "online" database. The next morning the users will need to sync with the online database before going offline. They will need to have offline access to the 30 most recent records. (They will use the 30 records for charting/graphing while they are offline) I am very new to building apps. I have VS 2010. I am wondering where to start? What language to use? Is there a "framework" for doing this type of app? Any info or suggestions would be greatly appreciated. Thanks!

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• (Rails) Creating multi-dimensional hashes/arrays from a data set...?

  - by humble_coder

  Hi All, I'm having a bit of an issue wrapping my head around something. I'm currently using a hacked version of Gruff in order to accommodate "Scatter Plots". That said, the data is entered in the form of: g.data("Person1",[12,32,34,55,23],[323,43,23,43,22]) ...where the first item is the ENTITY, the second item is X-COORDs, and the third item is Y-COORDs. I currently have a recordset of items from a table with the columns: POINT, VALUE, TIMESTAMP. Due to the "complex" calculations involved I must grab everything using a single query or risk way too much DB activity. That said, I have a list of items for which I need to dynamically collect all data from the recordset into a hash (or array of arrays) for the creation of the data items. I was thinking something like the following: @h={} e = Events.find_by_sql(my_query) e.each do |event| @h["#{event.Point}"][x] = event.timestamp @h["#{event.Point}"][y] = event.value end Obviously that's not the correct syntax, but that's where my brain is going. Could someone clean this up for me or suggest a more appropriate mechanism by which to accomplish this? Basically the main goal is to keep data for each pointname grouped (but remember the recordset has them all). Much appreciated. EDIT 1 g = Gruff::Scatter.new("600x350") g.title = self.name e = Event.find_by_sql(@sql) h ={} e.each do |event| h[event.Point.to_s] ||= {} h[event.Point.to_s].merge!({event.Timestamp.to_i,event.Value}) end h.each do |p| logger.info p[1].values.inspect g.data(p[0],p[1].keys,p[1].values) end g.write(@chart_file)

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• jQuery.data() works in Mac OS WebKit, but not on iPhone OS?

  - by rpj

  I'm playing around with jQTouch for an iPhone OS app that I've been toying with off and on for a while. I wanted to try my hand building it as a web app so I started playing with jQTouch. For reference, here is the page+source (all my code is currently in index.html so you can just "View Source" to see it all): http://rpj.me/doughapp.com/wd/ Essentially, I'm trying to save pertinent JSON objects retrieved from Google Local into DOM objects using the data() method (in this example, obj is the Google Local object): $('#locPane').data('selected', obj); then later (in a different "pane"), retrieving that object to be used: $('#locPane').bind('pageAnimationEnd', function(e, inf) { var selobj = $(this).data('selected'); // use 'selobj' here ... } In Chromium and Safari on the desktop OS (Snow Leopard in my case), this works perfectly (try it out). However, the same code returns undefined for the call to $(this).data('selected') in the second snippet above. I've also tried $('#' + e.target.id).data('selected') and even the naive $('#locPane').data('selected'). All variants return undefined in the iPhone OS version of WebKit, but not on the desktop. Interestingly, the running this on Mobile Safari in the iPhone Simulator fails as well. If you look at the full source, you'll see that I even try to save this object into my global jQTouch object (named jqt in my code). This, too, fails on the mobile platform. Has anyone else ever ran into this? I'll admit to not being a web/javascript programmer by trade, so if I'm making an idiot's error please call me out on it. Thank you in advance for the help! -RPJ Update: I didn't make it clear in the original post, but I'm open to any workaround if it works consistently. Since I'm having trouble storing these objects in general, anything that allows me to keep them around is good enough for now. Thanks!

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• How can I retain the data stored in plist from UITextField when application is restarted ?

  - by srikanth rongali

  I am using the plist to store the data entered in the UITextFields. But, when I restart my application all the data entered previously was deleted. How can I retain the data in the Plist. I have a UITableView and when a cell is touched a view appears with two UITextFields. nameField and descriptionField. I stored the data in this way. My code is. -(void)save:(id)sender { indexOfDataArray = temp; //the cell selected in table view. NSString *string1 = [[NSString alloc]init]; NSString *string2 = [[NSString alloc]init]; string1 = nameField.text; string2 = descriptionField.text; NSDictionary *myDict = [[NSDictionary alloc] initWithObjectsAndKeys:string2, string1, nil]; [myArray addObject:myDict]; //myArray is NSMutableArray declared in tableViewController class. //[myArray insertObject:myDict atIndex:indexOfDataArray]; NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES); NSString *documentsDirectory = [paths objectAtIndex:0]; NSString *path = [documentsDirectory stringByAppendingPathComponent:@"tableVideoData.plist"]; [myArray writeToFile:path atomically:YES]; UIAlertView *alertMesage = [[UIAlertView alloc] initWithTitle: @"Save Alert" message:@"The data entered is saved" delegate:nil cancelButtonTitle:@"cancel" otherButtonTitles:nil] ; [alertMesage show]; [alertMesage release]; } When I am using the [myArray insertObject:myDict atIndex:indexOfDataArray]; It is giving the error *** Terminating app due to uncaught exception 'NSRangeException', reason: '*** -[NSCFArray insertObject:atIndex:]: index (2) beyond bounds (1)' So I used [myArray addObject:myDict]; Please help me, how can I retain the data in plist. Thank You.

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• Android lifecycle: Fill in data in activity in onStart() or onResume()?

  - by pjv

  Should you get data via a cursor and fill in the data on the screen, such as setting the window title, in onStart() or onResume()? onStart() would seem the logical place because after onStart() the Activity can already be displayed, albeit in the background. Notably I was having a problem with a managed dialog that made me rethink this. If the user rotates the screen while the dialog is still open, onCreateDialog() and onPrepareDialog() are called between onStart() and onResume(). If the dialog needs to be based on the data you need to have the data before onResume(). If I'm correct about onStart() then why does the Notepad example give a bad example by doing it in onResume()? See http://developer.android.com/resources/samples/NotePad/src/com/example/android/notepad/NoteEditor.html NoteEditor.java line 176 (title = mCursor.getString...). Also, what if my Activity launches another Actvity/Dialog that changes the data my cursor is tracking. Even in the simplest case, does that mean that I have to manually update my previous screen (a listener for a dialog in the main activity), or alternatively that I have to register a ContentObserver, since I'm no longer updating the data in onResume() (though I could update it twice of course)? I know it's a basic question but the dialog only recently, to my surprise, made me realize this.

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• Building html structure in php or javascript?

  - by Adam

  I've been doing a lot of ajax calls and using the returned data to build html with javascript. However, I've noticed some people are returning the constructed html in the ajax calls since they're doing it all in php. What is the preferred method? I have a bunch of stuff already using javascript, so I guess I would prefer not changing everything to use just php. But, I'm assuming php would be more "secure."? The following is what I've been doing: $main_frag = $("<div class='order-container'/>"); $contact_frag = $("<div class='group'><div class='line-data'>Name: "+data.name+"</div><div class='line-data'>Email: "+data.email+"</div><div class='line-data'>Phone: "+data.phone+"</div></div>"); $address_frag = $("<div class='group'><div class='line-data'>Address 1: "+data.address_one+"</div><div class='line-data'>Address 2: "+address2+"</div><div class='line-data'>City: "+data.city+"</div><div class='line-data'>Province: "+data.province+"</div><div class='line-data'>Postal Code: "+data.postal+"</div></div>"); etc.. I just want to hear the opinions of the community.

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• Get notified when UITableView has finished asking for data?

  - by kennethmac2000

  Hi everyone, Is there some way to find out when a UITableView has finished asking for data from its data source? None of the viewDidLoad/viewWillAppear/viewDidAppear methods of the associated view controller (UITableViewController) are of use here, as they all fire too early. None of them (entirely understandably) guarantee that queries to the data source have finished for the time being (eg, until the view is scrolled). One workaround I have found is to call reloadData in viewDidAppear, since, when reloadData returns, the table view is guaranteed to have finished querying the data source as much as it needs to for the time being. However, this seems rather nasty, as I assume it is causing the data source to be asked for the same information twice (once automatically, and once because of the reloadData call) when it is first loaded. The reason I want to do this at all is that I want to preserve the scroll position of the UITableView - but right down to the pixel level, not just to the nearest row. When restoring the scroll position (using scrollRectToVisible:animated:), I need the table view to already have sufficient data in it, or else the scrollRectToVisible:animated: method call does nothing (which is what happens if you place the call on its own in any of viewDidLoad, viewWillAppear or viewDidAppear). Thanks in advance for your assistance!

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• Entity Framework vs. nHibernate for Performance, Learning Curve overall features

  - by hadi

  I know this has been asked several times and I have read all the posts as well but they all are very old. And considering there have been advancements in versions and releases, I am hoping there might be fresh views. We are building a new application on ASP.NET MVC and need to finalize on an ORM tool. We have never used ORM before and have pretty much boiled down to two - nHibernate & Entity Framework. I really need some advice from someone who has used both these tools and can recommend based on experience. There are three points that I am focusing on to finalize - Performance Learning Curve Overall Capability Your advice will be highly appreciated. Best Regards,

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• What is the performance hit of enabling sessions on Google App Engine?

  - by Spines

  What is the performance hit of enabling sessions on the Google App Engine? I just turned on <sessions-enabled>true</sessions-enabled> in my Google App Engine app and now my requests are consistently using 100 more ms of CPU time than before I enabled it. It also makes the user wait an additional 100ms for the server to respond on each request. This seems to be quite a significant cost, I'm not even calling getSession or using it in any way yet and it still adds this extra latency. Is there something I can do to speed this up?

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• zlib memory usage / performance. With 500kb of data.

  - by unixman83

  Is zLib Worth it? Are there other better suited compressors? I am using an embedded system. Frequently, I have only 3MB of RAM or less available to my application. So I am considering using zlib to compress my buffers. I am concerned about overhead however. The buffer's average size will be 30kb. This probably won't get compressed by zlib. Anyone know of a good compressor for extremely limited memory environments? However, I will experience occasional maximum buffer sizes of 700kb, with 500kb much more common. Is zlib worth it in this case? Or is the overhead too much to justify? My sole considerations for compression are RAM overhead of algorithm and performance at least as good as zlib.

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• C# Begin/EndReceive - how do I read large data?

  - by ryeguy

  When reading data in chunks of say, 1024, how do I continue to read from a socket that receives a message bigger than 1024 bytes until there is no data left? Should I just use BeginReceive to read a packet's length prefix only, and then once that is retrieved, use Receive() (in the async thread) to read the rest of the packet? Or is there another way? edit: I thought Jon Skeet's link had the solution, but there is a bit of a speedbump with that code. The code I used is: public class StateObject { public Socket workSocket = null; public const int BUFFER_SIZE = 1024; public byte[] buffer = new byte[BUFFER_SIZE]; public StringBuilder sb = new StringBuilder(); } public static void Read_Callback(IAsyncResult ar) { StateObject so = (StateObject) ar.AsyncState; Socket s = so.workSocket; int read = s.EndReceive(ar); if (read > 0) { so.sb.Append(Encoding.ASCII.GetString(so.buffer, 0, read)); if (read == StateObject.BUFFER_SIZE) { s.BeginReceive(so.buffer, 0, StateObject.BUFFER_SIZE, 0, new AyncCallback(Async_Send_Receive.Read_Callback), so); return; } } if (so.sb.Length > 0) { //All of the data has been read, so displays it to the console string strContent; strContent = so.sb.ToString(); Console.WriteLine(String.Format("Read {0} byte from socket" + "data = {1} ", strContent.Length, strContent)); } s.Close(); } Now this corrected works fine most of the time, but it fails when the packet's size is a multiple of the buffer. The reason for this is if the buffer gets filled on a read it is assumed there is more data; but the same problem happens as before. A 2 byte buffer, for exmaple, gets filled twice on a 4 byte packet, and assumes there is more data. It then blocks because there is nothing left to read. The problem is that the receive function doesn't know when the end of the packet is. This got me thinking to two possible solutions: I could either have an end-of-packet delimiter or I could read the packet header to find the length and then receive exactly that amount (as I originally suggested). There's problems with each of these, though. I don't like the idea of using a delimiter, as a user could somehow work that into a packet in an input string from the app and screw it up. It also just seems kinda sloppy to me. The length header sounds ok, but I'm planning on using protocol buffers - I don't know the format of the data. Is there a length header? How many bytes is it? Would this be something I implement myself? Etc.. What should I do?

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• Event Listener in Google Charts API

  - by DeanGrobler

  I'm busy using Google Charts in one of my projects to display data in a table. Everything is working great. Except that I need to see what line a user selected once they click a button. This would obviously be done with Javascript, but I've been struggling for days now to no avail. Below I've pasted code for a simple example of the table, and the Javascript function that I want to use (that doesn't work). <html> <head> <script type='text/javascript' src='https://www.google.com/jsapi'></script> <script type='text/javascript'> google.load('visualization', '1', {packages:['table']}); google.setOnLoadCallback(drawTable); var table = ""; function drawTable() { var data = new google.visualization.DataTable(); data.addColumn('string', 'Name'); data.addColumn('number', 'Salary'); data.addColumn('boolean', 'Full Time Employee'); data.addRows(4); data.setCell(0, 0, 'Mike'); data.setCell(0, 1, 10000, '$10,000'); data.setCell(0, 2, true); data.setCell(1, 0, 'Jim'); data.setCell(1, 1, 8000, '$8,000'); data.setCell(1, 2, false); data.setCell(2, 0, 'Alice'); data.setCell(2, 1, 12500, '$12,500'); data.setCell(2, 2, true); data.setCell(3, 0, 'Bob'); data.setCell(3, 1, 7000, '$7,000'); data.setCell(3, 2, true); table = new google.visualization.Table(document.getElementById('table_div')); table.draw(data, {showRowNumber: true}); } function selectionHandler() { selectedData = table.getSelection(); row = selectedData[0].row; item = table.getValue(row,0); alert("You selected :" + item); } </script> </head> <body> <div id='table_div'></div> <input type="button" value="Select" onClick="selectionHandler()"> </body> </html> Thanks in advance for anyone taking the time to look at this. I've honestly tried my best with this, hope someone out there can help me out a bit.

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• transform:translateX vs transition on left property. Which has better performance? CSS

  - by JackMahoney

  I'm making a slide out menu with HTML and CSS3 - especially transitions. I would like to know what is best practice / best performance to slide a relatively positioned div horizontally. When i click a button it adds a class to my div. Which class is better? (Note I can add all the browser prefixes later and this site only targets modern browsers). //option 1 .animate{ -webkit-transition:all ease 0.3s; -webkit-transform:translateZ(200px); } //option 2 .animate{ -webkit-transition:all ease 0.3s; left:200px; } Thanks

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• Maximum number of files one ext3 directory while still getting acceptable performance?

  - by knorv

  I have an application writing to an ext3 directory which over time has grown to roughly three million files. Needless to say, reading the file listing of this directory is unbearably slow. I don't blame ext3. The proper solution would have been to let the directory write to sub-directories such as ./a/b/c/abc.ext rather than just ./abc.ext. I'm changing to such a sub-directory structure and my question is simply: roughly how many files should I expect to store in one ext3 directory while still getting acceptable performance? Or in other words; assuming that I need to store three million files in the structure, how many levels deep should the ./a/b/c/abc.ext structure be? Obviously this is a question that cannot be answered exactly, but I'm looking for a ball park estimate.

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• Want to set 'src' of script to my IP-Won't load in Safari or Chrome. Relative link asp.netmvc

  - by Ozaki

  I have a script that links to the server I am hosting (IP can change) usually I would just use for links: var url ='http://' + window.location.hostname + 'end of url'; But in this case it isnt appearing to be so easy. I have tried: (1) $('#scriptid').attr('src', url); as well as: (2) var script = document.createElement( 'script' ); script.type = 'text/javascript'; script.src = url; $("#insert").append( script ); Now case (2) works loads the script runs the script. But when at the end of my script it hits the 'write data' it decides to replace the entire page with just the data. Any idea on how I can do this? Note: I am using plain html not ASP. With ASP backend that is just the way it has to be. Ok it now is <script src="myscript.js"></script> C# router.AddAsyncRoute("myscript.js"...... It workes in IE & FF. But I get blank pages in Chrome & Safari. I am using document.write to write a script onto my page. Any ideas why Chrome & Safari don't like this? I am so far assuming that in Crhome & Safari it takes longer to run the script therefore launching the document.write after the DOM has loaded therefore replacing the page with a blank one. edit the script im trying to run is a modification of: d = new dTree('d'); d.add(0,-1,'My example tree'); d.add(1,0,'Node 1','default.html'); d.add(2,0,'Node 2','default.html'); d.add(3,1,'Node 1.1','default.html'); d.add(4,0,'Node 3','default.html'); d.add(5,3,'Node 1.1.1','default.html') document.write(d); Any ideas how I can get around this? I am not to sure how to implement an appenChild in this case as the script is changing constantly with live data. So every refresh it will generally have changed some...

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• Mysterious constraints problem with SQL Server 2000

  - by Ramon

  Hi all I'm getting the following error from a VB NET web application written in VS 2003, on framework 1.1. The web app is running on Windows Server 2000, IIS 5, and is reading from a SQL server 2000 database running on the same machine. System.Data.ConstraintException: Failed to enable constraints. One or more rows contain values violating non-null, unique, or foreign-key constraints. at System.Data.DataSet.FailedEnableConstraints() at System.Data.DataSet.EnableConstraints() at System.Data.DataSet.set_EnforceConstraints(Boolean value) at System.Data.DataTable.EndLoadData() at System.Data.Common.DbDataAdapter.FillFromReader(Object data, String srcTable, IDataReader dataReader, Int32 startRecord, Int32 maxRecords, DataColumn parentChapterColumn, Object parentChapterValue) at System.Data.Common.DbDataAdapter.Fill(DataSet dataSet, String srcTable, IDataReader dataReader, Int32 startRecord, Int32 maxRecords) at System.Data.Common.DbDataAdapter.FillFromCommand(Object data, Int32 startRecord, Int32 maxRecords, String srcTable, IDbCommand command, CommandBehavior behavior) at System.Data.Common.DbDataAdapter.Fill(DataSet dataSet, Int32 startRecord, Int32 maxRecords, String srcTable, IDbCommand command, CommandBehavior behavior) at System.Data.Common.DbDataAdapter.Fill(DataSet dataSet) The problem appears when the web app is under a high load. The system runs fine when volume is low, but when the number of requests becomes high, the system starts rejecting incoming requests with the above exception message. Once the problem appears, very few requests actually make it through and get processed normally, about 2 in every 30. The vast majority of requests fail, until a SQL Server restart or IIS reset is performed. The system then start processing requests normally, and after some time it starts throwing the same error. The error occurs when a data adapter runs the Fill() method against a SELECT statement, to populate a strongly-typed dataset. It appears that the dataset does not like the data it is given and throws this exception. This error occurs on various SELECT statements, acting on different tables. I have regenerated the dataset and checked the relevant constraints, as well as the table from which the data is read. Both the dataset definition and the data in the table are fine. Admittedly, the hardware running both the web app and SQL Server 2000 is seriously outdated, considering the numbers of incoming requests it currently receives. The amount of RAM consumed by SQL Server is dynamically allocated, and at peak times SQL Server can consume up to 2.8 GB out of a total of 3.5 GB on the server. At first I suspected some sort of index or database corruption, but after running DBCC CHECKDB, no errors were found in the database. So now I'm wondering whether this error is a result of the hardware limitations of the system. Is it possible for SQL Server to somehow mess up the data it's supposed to pass to the dataset, resulting in constraint violation due to, say, data type/length mismatch? I tried accessing the RowError messages of the data rows in the retrieved dataset tables but I kept getting empty strings. I know that HasErrors = true for the datatables in question. I have not set the EnableConstraints = false, and I don't want to do that. Thanks in advance. Ray

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• Chaning coding style due to Android GC performance, how far is too far?

  - by Benju

  I keep hearing that Android applications should try to limit the number of objects created in order to reduce the workload on the garbage collector. It makes sense that you may not want to created massive numbers of objects to track on a limited memory footprint, for example on a traditional server application created 100,000 objects within a few seconds would not be unheard of. The problem is how far should I take this? I've seen tons of examples of Android applications relying on static state in order supposedly "speed things up". Does increasing the number of instances that need to be garbage collected from dozens to hundreds really make that big of a difference? I can imagine changing my coding style to now created hundreds of thousands of objects like you might have on a full-blown Java-EE server but relying on a bunch of static state to (supposedly) reduce the number of objects to be garbage collected seems odd. How much is it really necessary to change your coding style in order to create performance Android apps?

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• How to solve the performance decay of a VB.NET 1.1 application?

  - by marco.ragogna

  I have single-thread windows form application written with VB.NET and targeting Framework 1.1. The software communicates with external boards through a serial interface, and it mainly consist of a state machine that run some tests, driven in a loop done with a Timer and an Interval of 50ms. The feedback on the user interface is done through some custom events raised during the tests. The problem that is driving me crazy is that the performance slightly decrease over time, and in particular after 1200/1300 test operations. The memory occupied does not increase over time, it is only the CPU that seems interested by this problem. The strange thing is that, targeting framework 2.0 and using the same identical code, I do not have this problem. I know that is difficult without looking at the code, but do you have suggestions how can I approach the problem?

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• java System.nanoTime is really slow. Is it possible to implement a high performance java profiler?

  - by willpowerforever

  I did a test and found the overhead of a function call to System.nanoTime() is at least 500 ns on my machine. Seemed that it is very hard to have a high performance java profiler. For enterprise software, suppose a function takes about 350 seconds and has 12,500,000,000 times of method calls. Therefore, the number of calls to System.nanoTime() is: 12,500,000,000 * 2 = 25,000,000,000 (one for start timestamp, one for end timestamp) And the overhead of System.nanoTime in total is: 500 ns * 25,000,000,000 = 500 * 25000 s = 12500000s. Note: all data from real case. Any better way to acquire the timestamp?

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• Does the number of busy worker threads in the CLR ThreadPool affect performance of I/O threads?

  - by andrej351

  We have a Windows Service which hosts a number of WCF services and, in an unrelated part of the app, makes extensive use of the TPL Task class to asynchronously do relatively short bits of work. It is my understanding that WCF uses managed I/O threads from the ThreadPool to execute requests. I noticed that after deploying a feature which significantly raised the applications use of Tasks, and as such the use of ThreadPool worker threads as well, performance of a couple of web services has become very slow. We're talking minutes instead of less than a second. The number of Tasks actually trying to run at any one time can range between 20 and 1000, which makes me think that any new (last in) work needing some CPU time could be forced to wait for quite some time. Does the (in my case extremely large) number of busy ThreadPool worker threads affect the ThreadPool's managed I/O threads? Or could these two be connected in any way? Thanks!

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• Is there any short way to load data to the properties of a class, for each column name matching the properties of the class?

  - by Ugur Gümüshan

  I want to load data to an instance of an object using its constructor and I write $this->property=$row["colname"] each time for each property. the mysql_fetch_object function fetches the data as an object but I am not sure if the instance of an object can be assigned to some object from inside. othwerwise I would use __construct($object) { $this=$object; } //doesn't give any syntax error Maybe I should look into iteration of properties and use foreach($object as $key => $value) $value=$object[$key]; or can I assign like $this=$object; within the constructor?

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• Why I am not that user after I load cookies?

  - by MoreFreeze

  I want to grab some site data, but it must be a login account. So I register it and login, I found some API about this site that can be used to grab data. I use this Chrome plugin "cookie.txt export" export cookies.txt, I copy all content it export and use following cmd like wget -x --load-cookies cookies.txt http://www.example.com/api/name=xxxx but it doesn't work. It download the page that need I login. So I think this site has some other verification strategy, how can I pass it? Whether I must input in browser manually?

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