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• Is it possible to send OSC commands to an iPad via the Camera Connection Kit?

  - by HELVETICADE

  I'm building a small controller device that I'd like to partner with a computer. I've settled on using OSC out from my custom built hardware and am pretty satisfied with what I can get from WOscLib. Two goals I'd like to achieve are portability and a very nice ratio between battery:computing power, and this has lured me towards using iPhoneOS to accomplish my goals. I think the iPad would suit my needs perfectly, except that using wifi to broadcast OSC out from my device requires that device to be connected to a third device with a wifi chip, and this would destroy the goal of portability, whilst also introducing potential latency and stability headaches. My question is pretty simple: Can I push OSC commands FROM my controller TO an iPad via USB and the Camera Connection Kit? If I could accomplish this, the two major goals of my project would be fulfilled very nicely. This seems like it should be a simple little question, but researching this obsessively over the past few weeks has left me more almost more uncertain than if I had done no research at all. I'd really like some more confidence before I go down this route, and it seems like it should be possible. Any insight would be very, very appreciated.

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• A solution for the slow diff in (Tortoise)SVN?

  - by Michal Czardybon

  I often do code review in the following way: Open the SVN log Select a revision Double click on a file... ...and wait See the changes Goto 2 or 3 or finish The 4th step is very annoying. Do you know a solution for this?

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• Parallel.Foreach loop creating multiple db connections throws connection errors?

  - by shawn.mek

  Login failed. The login is from an untrusted domain and cannot be used with Windows authentication I wanted to get my code running in parallel, so I changed my foreach loop to a parallel foreach loop. It seemed simple enough. Each loop connects to the database, looks up some stuff, performs some logic, adds some stuff, closes the connection. But I get the above error? I'm using my local sql server and entity framework (each loop uses it's own context). Is there some problem with connecting multiple times using the same local login or something? How did I get around this? I have (before trying to covert to a parallel.foreach loop) split my list of objects that I am foreach looping through into four groups (separate csv files) and run four concurrent instances of my program (which ran faster overall than just one, thus the idea for parallel). So it seems connecting to the db shouldn't be a problem? Any ideas? EDIT: Here's before var gtgGenerator = new CustomGtgGenerator(); var connectionString = ConfigurationManager.ConnectionStrings["BioEntities"].ConnectionString; var allAccessionsFromObs = _GetAccessionListFromDataFiles(collectionId); ForEach(cloneIdAndAccessions in allAccessionsFromObs) DoWork(gtgGenerator, taxonId, organismId, cloneIdAndAccessions, connectionString)); after var gtgGenerator = new CustomGtgGenerator(); var connectionString = ConfigurationManager.ConnectionStrings["BioEntities"].ConnectionString; var allAccessionsFromObs = _GetAccessionListFromDataFiles(collectionId); Parallel.ForEach(allAccessionsFromObs, cloneIdAndAccessions => DoWork(gtgGenerator, taxonId, organismId, cloneIdAndAccessions, connectionString)); Inside the DoWork I use the BioEntities using (var bioEntities = new BioEntities(connectionString)) {...}

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• How to establish a socket connection from iPhone to a Apache server and communicate via PHP?

  - by candoyo

  Hi, I am working on an iPhone game which is depended on a LAMP server. I want to create a "event" based system where the apache server sends an event to the iphone. For this, I am thinking of using "CFStreamCreatePairWithSocketToHost" to connect to port 80 of the apache server. I am able to successfully connect to the server and open a read and write stream via the iPhone, but I am not sure how to send data to the iphone using PHP running from the LAMP server to the iPhone. I think I can use fsockopen in php to open a socket connection and write data to that socket. I tired running this code $fp = fsockopen("tcp://localhost", 80, $errno, $errstr); if (!$fp) { echo "ERROR: $errno - $errstr<br />\n"; } else { echo"writing to socket "; fwrite($fp, "wwqeqweqw eqwe qwe \n"); //echo fread($fp, 26); fclose($fp); echo "done"; } But, I dont see anything being read on the iphone.. Any idea what's going on, or how to accomplish this? Thanks!

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• How bad is opening and closing a SQL connection for several times? What is the exact effect?

  - by Eren

  For example, I need to fill lots of DataTables with SQLDataAdapter's Fill() method: DataAdapter1.Fill(DataTable1); DataAdapter2.Fill(DataTable2); DataAdapter3.Fill(DataTable3); DataAdapter4.Fill(DataTable4); DataAdapter5.Fill(DataTable5); .... .... Even all the dataadapter objects use the same SQLConnection, each Fill method will open and close the connection unless the connection state is already open before the method call. What I want to know is how does unnecessarily opening and closing SQLConnections affect the performance of the application. How much does it need to scale to see the bad effects of this problem (100,000s of concurrent users?). In a mid-size website (daily 50000 users) does it worth bothering and searching for all the Fill() calls, keeping them together in the code and opening the connection before any Fill() call and closing afterwards?

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• Drawing an image in Java, slow as hell on a netbook.

  - by Norswap

  In follow-up to my previous questions (especially this one : http://stackoverflow.com/questions/2684123/java-volatileimage-slower-than-bufferedimage), i have noticed that simply drawing an Image (it doesn't matter if it's buffered or volatile, since the computer has no accelerated memory*, and tests shows it's doesn't change anything), tends to be very long. (*) System.out.println(GraphicsEnvironment.getLocalGraphicsEnvironment() .getDefaultScreenDevice().getAvailableAcceleratedMemory()); --> 0 How long ? For a 500x400 image, about 0.04 seconds. This is only drawing the image on the backbuffer (obtained via buffer strategy). Now considering that world of warcraft runs on that netbook (tough it is quite laggy) and that online java games seems to have no problem whatsoever, this is quite thought provoking. I'm quite certain I didn't miss something obvious, I've searched extensively the web, but nothing will do. So do any of you java whiz have an idea of what obscure problem might be causing this (or maybe it is normal, tough I doubt it) ? PS : As I'm writing this I realized this might be cause by my Linux installation (archlinux) tough I have the correct Intel driver. But my computer normally has "Integrated Intel Graphics Media Accelerator 950", which would mean it should have accelerated video memory somehow. Any ideas about this side of things ?

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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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• PHP APC - Why is loading cached array op codes slow?

  - by Aaron Kreider

  I'm using APC to reduce my loading time for my PHP files. My files load very fast, except for one file where I define more than 100 arrays. This 270 kb file takes 200 ms to load. The rest of the files are full of objects, methods, and functions. I'm wondering: does OP code caching not work as well for arrays? My APC cache should be big enough to handle all of my classes. Currently 40% of my cache is free. My hit rate is 99%. apc.shm_size=32 M apc.max_file_size = 1M apc.shm_segments= 1 APC 3.1.6 I'm using PHP 5.2, Apache 2, and Windows Vista.

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• Wordpress database query running slow - one of the columns doesn't exist!

  - by Pavel

  Hi there. I'm having some problems with the query that wordpress runs. That's the one: SELECT DISTINCT ID,post_title,post_date,post_content,MATCH(post_title,post_content) AGAINST ('S') AS score FROM wp_posts WHERE MATCH (post_title,post_content) AGAINST ('S') AND post_date <= 'S' AND post_status = 'S' AND id != N AND post_type = 'S' ORDER BY score DESC When I'm running this query in phpmyadmin it says that N column doesn't exist so clause "AND id != N" si not making any sense. I ran the query again without this clause and db behaved like fully optimized one. Please can someone give me a hint on that? My questions are: What this clause is used for? What wordpress is trying to find by running this and Can I modify core wordpress files to get rid of this clause? Any response or help greatly appreciated!!

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• Where are the network boundaries in the Java Connector Architecture (JCA)?

  - by Laird Nelson

  I am writing a JCA resource adapter. I'm also, as I go, trying to fully understand the connection management portion of the JCA specification. As a thought experiment, pretend that the only client of this adapter will be a Swing Java Application Client located on a different machine. Also assume that the resource adapter will communicate with its "enterprise information system" (EIS) over the network as well. As I understand the JCA specification, the .rar file is deployed to the application server. The application server creates the .rar file's implementation of the ManagedConnectionFactory interface. It then asks it to produce a connection factory, which is the opaque object that is deployed to JNDI for the user to use to obtain a connection to the resource. (In the case of JDBC, the connection factory is a javax.sql.DataSource.) It is a requirement that the connection factory retain a reference to the application-server-supplied ConnectionManager, which, in turn, is required to be Serializable. This makes sense--in order for the connection factory to be stored in JNDI, it must be serializable, and in order for it to keep a reference to the ConnectionManager, the ConnectionManager must also be serializable. So fine, this little object graph gets installed in the application client's JNDI tree. This is where I start to get queasy. Is the ConnectionManager--the piece supplied by the application server that is supposed to handle connection management, sharing, pooling, etc.--wholly present on the client at this point? One of its jobs is to create ManagedConnection instances, and a ManagedConnection is not required to be Serializable, and the user connection handles it vends are also not required to be Serializable. That suggests to me that the whole connection pooling machinery is shipped wholesale to the application client and stuffed into its JNDI tree. Does this all mean that JCA interactions from the client side bypass the server-side componentry of the application server? Where are the network boundaries in the JCA API?

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• Python 3, urllib ... Reset Connection Possible?

  - by Rhys

  In the larger scale of my program the goal of the below code is to filter out all dynamic html in a web-page source code code snippet: try: deepreq3 = urllib.request.Request(deepurl3) deepreq3.add_header("User-Agent","etc......") deepdata3 = urllib.request.urlopen(deepurl3).read().decode("utf8", 'ignore') The following code is looped 3 times in order to identify whether the target web-page is Dynamic (source code is changed at intervals) or not. If the page IS dynamic, the above code loops another 15 times and attempts to filter out the dynamic content. QUESTION: While this filtering method works 80% of the time, some pages will reload ALL 15 times and STILL contain dynamic code. HOWEVER. If I manually close down the Python Shell and re-execute my program, the dynamic html that my 'refresh-page method' could not shake off is no longer there ... it's been replaced with new dynamic html that my 'refresh-page method' cannot shake off. So I need to know, what is going on here? How is re-running my program causing the dynamic content of a page to change. AND, is there any way, any 'reset connection' command I can use to recreate this ... without manually restarting my app. Thanks for your response.

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• Getting unhandled error and connection get lost when a client tries to communicate with chat server in twisted

  - by user2433888

  from twisted.internet.protocol import Protocol,Factory from twisted.internet import reactor class ChatServer(Protocol): def connectionMade(self): print "A Client Has Connected" self.factory.clients.append(self) print"clients are ",self.factory.clients self.transport.write('Hello,Welcome to the telnet chat to sign in type aim:YOUR NAME HERE to send a messsage type msg:YOURMESSAGE '+'\n') def connectionLost(self,reason): self.factory.clients.remove(self) self.transport.write('Somebody was disconnected from the server') def dataReceived(self,data): #print "data is",data a = data.split(':') if len(a) > 1: command = a[0] content = a[1] msg="" if command =="iam": self.name + "has joined" elif command == "msg": ma=sg = self.name + ":" +content print msg for c in self.factory.clients: c.message(msg) def message(self,message): self.transport.write(message + '\n') factory = Factory() factory.protocol = ChatServer factory.clients = [] reactor.listenTCP(80,factory) print "Iphone Chat server started" reactor.run() The above code is running succesfully...but when i connect the client (by typing telnet localhost 80) to this chatserver and try to write message ,connection gets lost and following errors occurs : Iphone Chat server started A Client Has Connected clients are [<__main__.ChatServer instance at 0x024AC0A8>] Unhandled Error Traceback (most recent call last): File "C:\Python27\lib\site-packages\twisted\python\log.py", line 84, in callWithLogger return callWithContext({"system": lp}, func, *args, **kw) File "C:\Python27\lib\site-packages\twisted\python\log.py", line 69, in callWithContext return context.call({ILogContext: newCtx}, func, *args, **kw) File "C:\Python27\lib\site-packages\twisted\python\context.py", line 118, in callWithContext return self.currentContext().callWithContext(ctx, func, *args, **kw) File "C:\Python27\lib\site-packages\twisted\python\context.py", line 81, in callWithContext return func(*args,**kw) --- --- File "C:\Python27\lib\site-packages\twisted\internet\selectreactor.py", line 150, in _doReadOrWrite why = getattr(selectable, method)() File "C:\Python27\lib\site-packages\twisted\internet\tcp.py", line 199, in doRead rval = self.protocol.dataReceived(data) File "D:\chatserverultimate.py", line 21, in dataReceived content = a[1] exceptions.IndexError: list index out of range Where am I going wrong?

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• Fast response on first Socket I/O request but slow every other time when communicating with remote serial port

  - by GreenGodot

  I'm using sockets to pass Serial commands to a remote device. And the response to that request is sent back and printed out. However, I am having a problem in that the first time it is instant but the rest of the time it can take up to 20 seconds to receive a reply. I think the problem is with my attempt at threading but I am not entirely sure. new Thread() { @Override public void run() { System.out.println("opened"); try { isSocketRetrieving.setText("Opening Socket"); socket = new Socket(getAddress(), getRemotePort())); DataOutput = new DataOutputStream(socket .getOutputStream()); inFromServer = new BufferedReader( new InputStreamReader(socket .getInputStream())); String line = ""; isSocketRetrieving.setText("Reading Stream......"); while ((line = inFromServer.readLine()) != null) { System.out.println(line); if (line.contains(getHandshakeRequest())) { DataOutput.write((getHandshakeResponse()toString() + "\r").getBytes()); DataOutput.flush(); DataOutput .write((getCommand().toString() + "\r").getBytes()); DataOutput.flush(); int pause = (line.length()*8*1000)/getBaud(); sleep(pause); } else if (line.contains(readingObject .getExpected())) { System.out.println(line); textArea.append("value = " + line + "\n"); textAreaScroll.revalidate(); System.out.println("Got Value"); break; } } System.out.println("Ended"); try { inFromServer.close(); DataOutput.close(); socket.close(); isSocketRetrieving.setText("Socket is inactive..."); rs232Table.addMouseListener(listener); interrupt(); join(); } catch (IOException e) { e.printStackTrace(); } catch (InterruptedException e) { System.out.println("Thread exited"); } } catch (NumberFormatException e1) { e1.printStackTrace(); } catch (UnknownHostException e1) { e1.printStackTrace(); } catch (IOException e1) { e1.printStackTrace(); } catch (InterruptedException e) { // TODO Auto-generated catch block e.printStackTrace(); } } }.start();

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• How to slow down or speed up the playback of audio when using Audio Queue Services?

  - by mystify

  Is that possible? How is this done in theory? Would I simply make a very small buffer packet size and then delay the playback artificially? I assume that's the low-brain way? How could I do it in such a way that the sound is smooth and doesn't suck?

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• Google Chrome Extension : Port: Could not establish connection. Receiving end does not exist

  - by tcornelis

  I have been looking for an answer for almost a week now, but having read all the stackoverflow items i can't seem to find a solution that is working for me. The error that i'm having is : Port: Could not establish connection. Receiving end does not exist. lastError:30 set lastError:30 dispatchOnDisconnect messaging:277 folder layout : img developer_icon.png js sidebar.js main.js jquery-2.0.3.js manifest.json my the manifest.json file looks something like this (it is version 2) :` "browser_action": { "default_icon": "./img/developer_icon.png" }, "content_scripts": [ { "matches": ["*://*/*"], "js": ["./js/sidebar.js"], "run_at": "document_end" } ], "background" : { "scripts" : ["./js/main.js","./js/jquery-2.0.3.js"] }, I want to handle the user clicking the extension icon so i could inject a sidebar in the existing website (because the extension i would like to develop requires that amount of space). So in main.js : chrome.browserAction.onClicked.addListener(function(tab) { chrome.tabs.getSelected(null, function(tab){ chrome.tabs.sendMessage( //Selected tab id tab.id, //Params inside a object data {callFunction: "toggleSidebar"}, //Optional callback function function(response) { console.log(response); } ); }); }); and in sidebar.js : chrome.runtime.onMessage.addListener(function(req,sender,sendResponse){ console.log("sidebar handling request"); toggleSidebar(); }); but i'm never able to see the console.log in my console because of the error. Does someone know what i did wrong? Thanks in advance!

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• Iteration over a linq to sql query is very slow.

  - by devzero

  I have a view, AdvertView in my database, this view is a simple join between some tables (advert, customer, properties). Then I have a simple linq query to fetch all adverts for a customer: public IEnumerable<AdvertView> GetAdvertForCustomerID(int customerID) { var advertList = from advert in _dbContext.AdvertViews where advert.Customer_ID.Equals(customerID) select advert; return advertList; } I then wish to map this to modelItems for my MVC application: public List<AdvertModelItem> GetAdvertsByCustomer(int customerId) { List<AdvertModelItem> lstAdverts = new List<AdvertModelItem>(); List<AdvertView> adViews = _dataHandler.GetAdvertForCustomerID(customerId).ToList(); foreach(AdvertView adView in adViews) { lstAdverts.Add(_advertMapper.MapToModelClass(adView)); } return lstAdverts; } I was expecting to have some performance issues with the SQL, but the problem seems to be with the .ToList() function. I'm using ANTS performance profiler and it reports that the total runtime of the function is 1.400ms, and 850 of those is with the ToList(). So my question is, why does the tolist function take such a long time here?

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• Is using joins in select clause slow in Oracle?

  - by gniquil

  I would like to write a query like the following select username, (select state from addresses where addresses.username = users.username) email from users This works in Oracle (assuming the result from the inner query is unique). However, is there a performance penalty associated with this style of writing query?

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• Jython & Mysql - what is the current practice for connection?

  - by Sector7B

  Just trying jython for the first time, because something came up at work that would fit for this perfect for it. I assume jython can make mysql jdbc connection using the mysql jdbc driver. After googling and reading, however I am having problems and it seems jython specific and probably simple. so i do jython: Jython 2.5.1 (Release_2_5_1:6813, Sep 26 2009, 13:47:54) [Java HotSpot(TM) 64-Bit Server VM (Apple Inc.)] on java1.6.0_17 Type "help", "copyright", "credits" or "license" for more information. >>> import sys >>> print sys.path ['', '/JYTHONPATH/mysql-connector-java-5.1.10-bin.jar', '/WorkArea/Apps/jython/jython2.5.1/Lib', '__classpath__', '__pyclasspath__/', '/WorkArea/Apps/jython/jython2.5.1/Lib/site-packages'] >>> code i'm running from java.lang import * from java.sql import * driverName="com.mysql.jdbc.Driver" Class.forName(driverName) url = "jdbc:mysql://localhost/test?user=jgreenaw&password=" con = DriverManager.getConnection(url) stmt = con.createStatement() output riux:Desktop$ jython pymysql.py Traceback (most recent call last): File "pymysql.py", line 7, in <module> Class.forName(driverName) at java.net.URLClassLoader$1.run(URLClassLoader.java:200) at java.security.AccessController.doPrivileged(Native Method) at java.net.URLClassLoader.findClass(URLClassLoader.java:188) at java.lang.ClassLoader.loadClass(ClassLoader.java:315) at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:330) at java.lang.ClassLoader.loadClass(ClassLoader.java:250) at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:398) at java.lang.Class.forName0(Native Method) at java.lang.Class.forName(Class.java:169) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) at java.lang.reflect.Method.invoke(Method.java:597) java.lang.ClassNotFoundException: java.lang.ClassNotFoundException: com.mysql.jdbc.Driver any advice? thanks

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• JAR files, don't they just bloat and slow Java down?

  - by Josamoto

  Okay, the question might seem dumb, but I'm asking it anyways. After struggling for hours to get a Spring + BlazeDS project up and running, I discovered that I was having problems with my project as a result of not including the right dependencies for Spring etc. There were .jars missing from my WEB-INF/lib folder, yes, silly me. After a while, I managed to get all the .jar files where they belong, and it comes at a whopping 12.5MB at that, and there's more than 30 of them! Which concerns me, but it probably and hopefully shouldn't be concerned. How does Java operate in terms of these JAR files, they do take up quite a bit of hard drive space, taking into account that it's compressed and compiled source code. So that can really quickly populate a lot of RAM and in an instant. My questions are: Does Java load an entire .jar file into memory when say for instance a class in that .jar is instantiated? What about stuff that's in the .jar that never gets used. Do .jars get cached somehow, for optimized application performance? When a single .jar is loaded, I understand that the thing sits in memory and is available across multiple HTTP requests (i.e. for the lifetime of the server instance running), unlike PHP where objects are created on the fly with each request, is this assumption correct? When using Spring, I'm thinking, I had to include all those fiddly .jars, wouldn't I just be better off just using native Java, with say at least and ORM solution like Hibernate? So far, Spring just took extra time configuring, extra hard drive space, extra memory, cpu consumption, so I'm concerned that the framework is going to cost too much application performance just to get for example, IoC implemented with my BlazeDS server. There still has to come ORM, a unit testing framework and bits and pieces here and there. It's just so easy to bloat up a project quickly and irresponsibly easily. Where do I draw the line?

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• How can creating the SessionFactory become slow after updating Hibernate?

  - by DR

  In my Java SE application I used Hibernate 3.4 and creating the SessionFactory took about 5 seconds. Today I updated to Hibernate 3.5.1 and suddenly it takes over a minute. What can be the cause of such a dramatic effect? I tried different things the better part of the day and I have no clue... Some data I collected According to the profiler the most time is spent in PersisterFactory.createClassPersister and in that method ProxyFactory.createClass takes the most time. The log shows nothing unusual Changing hibernate.bytecode.use_reflection_optimizer makes no difference

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• Data Warehouse ETL slow - change primary key in dimension?

  - by Jubbles

  I have a working MySQL data warehouse that is organized as a star schema and I am using Talend Open Studio for Data Integration 5.1 to create the ETL process. I would like this process to run once per day. I have estimated that one of the dimension tables (dimUser) will have approximately 2 million records and 23 columns. I created a small test ETL process in Talend that worked, but given the amount of data that may need to be updated daily, the current performance will not cut it. It takes the ETL process four minutes to UPDATE or INSERT 100 records to dimUser. If I assumed a linear relationship between the count of records and the amount of time to UPDATE or INSERT, then there is no way the ETL can finish in 3-4 hours (my hope), let alone one day. Since I'm unfamiliar with Java, I wrote the ETL as a Python script and ran into the same problem. Although, I did discover that if I did only INSERT, the process went much faster. I am pretty sure that the bottleneck is caused by the UPDATE statements. The primary key in dimUser is an auto-increment integer. My friend suggested that I scrap this primary key and replace it with a multi-field primary key (in my case, 2-3 fields). Before I rip the test data out of my warehouse and change the schema, can anyone provide suggestions or guidelines related to the design of the data warehouse the ETL process how realistic it is to have an ETL process INSERT or UPDATE a few million records each day will my friend's suggestion significantly help If you need any further information, just let me know and I'll post it. UPDATE - additional information: mysql> describe dimUser; Field Type Null Key Default Extra user_key int(10) unsigned NO PRI NULL auto_increment id_A int(10) unsigned NO NULL id_B int(10) unsigned NO NULL field_4 tinyint(4) unsigned NO 0 field_5 varchar(50) YES NULL city varchar(50) YES NULL state varchar(2) YES NULL country varchar(50) YES NULL zip_code varchar(10) NO 99999 field_10 tinyint(1) NO 0 field_11 tinyint(1) NO 0 field_12 tinyint(1) NO 0 field_13 tinyint(1) NO 1 field_14 tinyint(1) NO 0 field_15 tinyint(1) NO 0 field_16 tinyint(1) NO 0 field_17 tinyint(1) NO 1 field_18 tinyint(1) NO 0 field_19 tinyint(1) NO 0 field_20 tinyint(1) NO 0 create_date datetime NO 2012-01-01 00:00:00 last_update datetime NO 2012-01-01 00:00:00 run_id int(10) unsigned NO 999 I used a surrogate key because I had read that it was good practice. Since, from a business perspective, I want to keep aware of potential fraudulent activity (say for 200 days a user is associated with state X and then the next day they are associated with state Y - they could have moved or their account could have been compromised), so that is why geographic data is kept. The field id_B may have a few distinct values of id_A associated with it, but I am interested in knowing distinct (id_A, id_B) tuples. In the context of this information, my friend suggested that something like (id_A, id_B, zip_code) be the primary key. For the large majority of daily ETL processes (80%), I only expect the following fields to be updated for existing records: field_10 - field_14, last_update, and run_id (this field is a foreign key to my etlLog table and is used for ETL auditing purposes).

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• Slow query. Wrong database structure?

  - by Tin

  I have a database with table that contains tasks. Tasks have a lifecycle. The status of the task's lifecycle can change. These state transitions are stored in a separate table tasktransitions. Now I wrote a query to find all open/reopened tasks and recently changed tasks but I already see with a rather small number of tasks (<1000) that execution time has becoming very long (0.5s). Tasks +-------------+---------+------+-----+---------+----------------+ | Field | Type | Null | Key | Default | Extra | +-------------+---------+------+-----+---------+----------------+ | taskid | int(11) | NO | PRI | NULL | auto_increment | | description | text | NO | | NULL | | +-------------+---------+------+-----+---------+----------------+ Tasktransitions +------------------+-----------+------+-----+-------------------+----------------+ | Field | Type | Null | Key | Default | Extra | +------------------+-----------+------+-----+-------------------+----------------+ | tasktransitionid | int(11) | NO | PRI | NULL | auto_increment | | taskid | int(11) | NO | MUL | NULL | | | status | int(11) | NO | MUL | NULL | | | description | text | NO | | NULL | | | userid | int(11) | NO | | NULL | | | transitiondate | timestamp | NO | | CURRENT_TIMESTAMP | | +------------------+-----------+------+-----+-------------------+----------------+ Query SELECT tasks.taskid,tasks.description,tasklaststatus.status FROM tasks LEFT OUTER JOIN ( SELECT tasktransitions.taskid,tasktransitions.transitiondate,tasktransitions.status FROM tasktransitions INNER JOIN ( SELECT taskid,MAX(transitiondate) AS lasttransitiondate FROM tasktransitions GROUP BY taskid ) AS tasklasttransition ON tasklasttransition.lasttransitiondate=tasktransitions.transitiondate AND tasklasttransition.taskid=tasktransitions.taskid ) AS tasklaststatus ON tasklaststatus.taskid=tasks.taskid WHERE tasklaststatus.status IS NULL OR tasklaststatus.status=0 or tasklaststatus.transitiondate>'2013-09-01'; I'm wondering if the database structure is best choice performance wise. Could adding indexes help? I already tried to add some but I don't see great improvements. +-----------------+------------+----------------+--------------+------------------+-----------+-------------+----------+--------+------+------------+---------+---------------+ | Table | Non_unique | Key_name | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment | Index_comment | +-----------------+------------+----------------+--------------+------------------+-----------+-------------+----------+--------+------+------------+---------+---------------+ | tasktransitions | 0 | PRIMARY | 1 | tasktransitionid | A | 896 | NULL | NULL | | BTREE | | | | tasktransitions | 1 | taskid_date_ix | 1 | taskid | A | 896 | NULL | NULL | | BTREE | | | | tasktransitions | 1 | taskid_date_ix | 2 | transitiondate | A | 896 | NULL | NULL | | BTREE | | | | tasktransitions | 1 | status_ix | 1 | status | A | 3 | NULL | NULL | | BTREE | | | +-----------------+------------+----------------+--------------+------------------+-----------+-------------+----------+--------+------+------------+---------+---------------+ Any other suggestions?

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• MySQL very slow compared to MS Access when inserting hundred of thousands of rows ! So is there a my

  - by asksuperuser

  I am currently adding hundred of thousands of rows of data to a table first on a MS Access Table then on a MySQL Table. I first tried with MS Access, it tooks less than 40 seconds. Then I tried exactly with the same source and with the same table structure to MySQL and it took 6 min and 40 seconds that is 1000% slower !!! So is there a myth that a database server is more performant ?

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• How to find which method makes my iPhone app slow ?

  - by Stewart Hou

  Currently I am working on a production app. One function acts like the settings.app on iPhone. When the user click a cell of a tableView, as shown below http://www.penguintech.net/images/stackoverflow/1.png It will push another view, which includes a textfield to let user input something. However, on both simulator and device, after the app just loaded, the delay between clicking and showing the second view takes around 2 seconds. Then if user get back to previous view and click again, it will be no delay at all. To detect which method makes the delay, I put a NSLog() in every involved methods, but when I was inspecting the console while running the app, all NSLog() message showed in 0.1 seconds, and then still a delay on the app. Is there any other way to trace the performance footage of a app? The Instruments shows only CPU usage in Mac OS not in iPhone.

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• Why is this loop over mysql resultset slow? (1.4ms per cycle)

  - by pawpro

  The $res contains around 488k rows the whole loop takes 61s! that's over 1.25ms per cycle! What is taking all that time? while($row = $res->fetch_assoc()) { $clist[$row['upload_id']][$row['dialcode_id']][$row['carrier_id']]['std'] = $row['cost_std']; $clist[$row['upload_id']][$row['dialcode_id']][$row['carrier_id']]['ecn'] = $row['cost_ecn']; $clist[$row['upload_id']][$row['dialcode_id']][$row['carrier_id']]['wnd'] = $row['cost_wnd']; $dialcode_destination[$row['upload_id']][$row['carrier_id']][$row['dialcode_id']]['other_destination'] = $row['destination_id']; $dialcode_destination[$row['upload_id']][$row['carrier_id']][$row['dialcode_id']]['carrier_destination'] = $row['carrier_destination_id']; } Now resultset of 10 rows, smaller arrays and performance 30 times higher (0.041ms) not the fastest still but better. while($row = $res->fetch_assoc()) { $customer[$row['id']]['name'] = $row['name']; $customer[$row['id']]['code'] = $row['customer']; }

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