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• Looking for suggestions about an architecture of a MultiThreaded app.

  - by Dimitri

  Hello everyone. I am looking to develop a multithreaded application that will be running in unconditional loop and processing high volume of data. High volume is 2000+ records per minute. Processing will involve data retrieval, calculations and data updates. I need the application to perform so that there is virtually no back log, meaning i need to be able to finish up all of the 2000 points in one minute or even faster. Our current implementation features a multithreaded application that is spawn multiple times (from 10 to 20) and we are noticing that it's not handling data as expected and i even feel that instances of the application compete with each other for processor time and eventually if not slowing, not benefiting each other for sure. I would like to know what would be the best approach: have a single instance running but maximize threads that can run simultaneously? or is there other ways i don't know? I'm open to suggestions. Thank you in advance

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• How is fseek() implemented in the filesystem?

  - by pajton

  This is not a pure programming question, however it impacts the performance of programs using fseek(), hence it is important to know how it works. A little disclaimer so that it doesn't get closed. I am wondering how efficient it is to insert data in the middle of the file. Supposing I have a file with 1MB data and then I insert something at the 512KB offset. How efficient would that be compared to appending my data at the end of the file? Just to make the example complete lets say I want to insert 16KB of data. I understand the answer varies depending on the filesystem, however I assume that the techniques used in common filesystems are quite similar and I just want to get the right notion of it.

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• Does my basic PHP Socket Server need optimization?

  - by Tom

  Like many people, I can do a lot of things with PHP. One problem I do face constantly is that other people can do it much cleaner, much more organized and much more structured. This also results in much faster execution times and much less bugs. I just finished writing a basic PHP Socket Server (the real core), and am asking you if you can tell me what I should do different before I start expanding the core. I'm not asking about improvements such as encrypted data, authentication or multi-threading. I'm more wondering about questions like "should I maybe do it in a more object oriented way (using PHP5)?", or "is the general structure of the way the script works good, or should some things be done different?". Basically, "is this how the core of a socket server should work?" In fact, I think that if I just show you the code here many of you will immediately see room for improvements. Please be so kind to tell me. Thanks! #!/usr/bin/php -q <? // config $timelimit = 180; // amount of seconds the server should run for, 0 = run indefintely $address = $_SERVER['SERVER_ADDR']; // the server's external IP $port = 9000; // the port to listen on $backlog = SOMAXCONN; // the maximum of backlog incoming connections that will be queued for processing // configure custom PHP settings error_reporting(1); // report all errors ini_set('display_errors', 1); // display all errors set_time_limit($timelimit); // timeout after x seconds ob_implicit_flush(); // results in a flush operation after every output call //create master IPv4 based TCP socket if (!($master = socket_create(AF_INET, SOCK_STREAM, SOL_TCP))) die("Could not create master socket, error: ".socket_strerror(socket_last_error())); // set socket options (local addresses can be reused) if (!socket_set_option($master, SOL_SOCKET, SO_REUSEADDR, 1)) die("Could not set socket options, error: ".socket_strerror(socket_last_error())); // bind to socket server if (!socket_bind($master, $address, $port)) die("Could not bind to socket server, error: ".socket_strerror(socket_last_error())); // start listening if (!socket_listen($master, $backlog)) die("Could not start listening to socket, error: ".socket_strerror(socket_last_error())); //display startup information echo "[".date('Y-m-d H:i:s')."] SERVER CREATED (MAXCONN: ".SOMAXCONN.").\n"; //max connections is a kernel variable and can be adjusted with sysctl echo "[".date('Y-m-d H:i:s')."] Listening on ".$address.":".$port.".\n"; $time = time(); //set startup timestamp // init read sockets array $read_sockets = array($master); // continuously handle incoming socket messages, or close if time limit has been reached while ((!$timelimit) or (time() - $time < $timelimit)) { $changed_sockets = $read_sockets; socket_select($changed_sockets, $write = null, $except = null, null); foreach($changed_sockets as $socket) { if ($socket == $master) { if (($client = socket_accept($master)) < 0) { echo "[".date('Y-m-d H:i:s')."] Socket_accept() failed, error: ".socket_strerror(socket_last_error())."\n"; continue; } else { array_push($read_sockets, $client); echo "[".date('Y-m-d H:i:s')."] Client #".count($read_sockets)." connected (connections: ".count($read_sockets)."/".SOMAXCONN.")\n"; } } else { $data = @socket_read($socket, 1024, PHP_NORMAL_READ); //read a maximum of 1024 bytes until a new line has been sent if ($data === false) { //the client disconnected $index = array_search($socket, $read_sockets); unset($read_sockets[$index]); socket_close($socket); echo "[".date('Y-m-d H:i:s')."] Client #".($index-1)." disconnected (connections: ".count($read_sockets)."/".SOMAXCONN.")\n"; } else { if ($data = trim($data)) { //remove whitespace and continue only if the message is not empty switch ($data) { case "exit": //close connection when exit command is given $index = array_search($socket, $read_sockets); unset($read_sockets[$index]); socket_close($socket); echo "[".date('Y-m-d H:i:s')."] Client #".($index-1)." disconnected (connections: ".count($read_sockets)."/".SOMAXCONN.")\n"; break; default: //for experimental purposes, write the given data back socket_write($socket, "\n you wrote: ".$data); } } } } } } socket_close($master); //close the socket echo "[".date('Y-m-d H:i:s')."] SERVER CLOSED.\n"; ?>

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• Jquery ui autocomplete different source

  - by voidnull

  Hi i try to use jquery ui autocomplete. I have different autocomplete field in one page and i need to get data with different sources (different url) depend to wich autocomplete field is used. i know how can i get the typed data (request.term), but i cant find the way to get the selected field ID. $(".ac").autocomplete({ source: function(request, response) { id = '??? the actually used field #id ???'; $.ajax({ type: "POST", url: "/admin_/sql/autocomplete/"+id, data: "test=...", async: false, success: function(data) { } }); }, search: function() { // }, focus: function() { // return false; }, select: function(event, ui) { // return false; } });

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• Set DetailsView as selected row of GridView

  - by Nix

  I am afraid this is a brain fart question. But I have searched around and have not been able to find the answer. I am creating a GridView/DetailsView page. I have a grid that displays a bunch of rows, when a row is selected it uses a DetailsView to allow for Insert/Update. My question is what is the best way to link these? I do not want to reach out to the web service again, all the data i need is in the selected grid view row. I basically have 2 separate data sources that share the same "DataObjectTypeName", the first data source retrieves the data, and the other to do the CRUD. What is the best way to transfer the Selected Grid View row to the Details View? Am I going to have to manualy handle the Insert/Update events and call the data source myself? <asp:GridView ID="gvDetails" runat="server" DataKeyNames="ID, Code" DataSourceID="odsSearchData" > <Columns> <asp:BoundField DataField="RowA" HeaderText="A" SortExpression="RowA" /> <asp:BoundField DataField="RowB" HeaderText="B" SortExpression="RowB" /> <asp:BoundField DataField="RowC" HeaderText="C" SortExpression="RowC" /> ....Code... <asp:DetailsView ID="dvDetails" runat="server" DataKeyNames="ID, Code" DataSourceID="odsCRUD" GridLines="None" DefaultMode="Edit" AutoGenerateRows="false" Visible="false" Width="100%"> <Fields> <asp:BoundField DataField="RowA" HeaderText="A" SortExpression="RowA" /> <asp:BoundField DataField="RowB" HeaderText="B" SortExpression="RowB" /> <asp:BoundField DataField="RowC" HeaderText="C" SortExpression="RowC" /> ...

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• Cascading dropdowns

  - by SnowJim

  Hi! I am working with cascading dropdowns in MVC. It appears that I will not be able to easily create dropdowns on demand, instead I will have to add the dropdowns before sending it to the client. This is how I am doing it right now: In the aspx page <%: Html.DropDownListFor(model => model.ModelViewAd.Category1, Model.ModelViewAd.Category1List, "-- Välj kategori --")%> <%: Html.DropDownListFor(model => model.ModelViewAd.Category2, Model.ModelViewAd.Category2List, "-- Välj kategori --")%> <%: Html.DropDownListFor(model => model.ModelViewAd.Category3, Model.ModelViewAd.Category3List, "-- Välj kategori --")%> <%: Html.DropDownListFor(model => model.ModelViewAd.Category4, Model.ModelViewAd.Category4List, "-- Välj kategori --")%> This is rendered like this : <select id="ModelViewAd_Category1" name="ModelViewAd.Category1"> <option value="">-- V&#228;lj kategori --</option> <option value="10">Fordon</option> <option value="15">F&#246;r hemmet</option> <option value="17">Bostad</option> </select> <select id="ModelViewAd_Category2" name="ModelViewAd.Category2"> <option value="">-- V&#228;lj kategori --</option> </select> <select id="ModelViewAd_Category3" name="ModelViewAd.Category3"> <option value="">-- V&#228;lj kategori --</option> </select> <select id="ModelViewAd_Category4" name="ModelViewAd.Category4"> <option value="">-- V&#228;lj kategori --</option> </select> This is what the script on the page looks like: <script type="text/javascript"> $(function () { $("select#ModelViewAd_Category1").change(function () { var id = $(this).val(); var urlAction = "/AdCategory/GetCategoriesByParent1/" + id; $.getJSON(urlAction, { id: id }, function (data) { $("#ModelViewAd_Category2").addItems(data.d); }); }); $("select#ModelViewAd_Category2").change(function () { var id = $(this).val(); var urlAction = "/AdCategory/GetCategoriesByParent1/" + id; $.getJSON(urlAction, { id: id }, function (data) { $("#ModelViewAd_Category3").addItems(data.d); }); }); $("select#ModelViewAd_Category3").change(function () { var id = $(this).val(); var urlAction = "/AdCategory/GetCategoriesByParent1/" + id; $.getJSON(urlAction, { id: id }, function (data) { $("#ModelViewAd_Category4").addItems(data.d); }); }); }); </script> And then I have an included file that contains this: $.fn.clearSelect = function () { return this.each(function () { if (this.tagName == 'SELECT') this.options.length = 0; }); } $.fn.addItems = function (data) { return this.clearSelect().each(function () { if (this.tagName == 'SELECT') { var dropdownList = this; $.each(data, function (index, optionData) { var option = new Option(optionData.Text, optionData.Value); if ($.browser.msie) { dropdownList.add(option); } else { dropdownList.add(option, null); } if ($(this).children().size() < 2) { $(this).hide(); } else { $(this).show(); } }); } }); } The problem I now have is that I need to hide the dropdowns that do not contain any options or only contain one option. This should be checked when doing a call to the service as well as when the page is sent to the client ("POSTBACK"). What I need is : 4 Dropdowns Only the first dropdown is visible when first entering the page. When selecting an option from dropdown1 the dropdown2 will be populated and so on If there is only 1 option then the dropdown should be hidden If all 4 dropdowns are set and the end-user changes dropdown1, then dropdown2 should be reloaded and the rest be hidden If the user has selected some of the dropdowns (say 1, 2 and 3) and hit submit and the page is not accepted on the server side (not valid) the dropdowns should be set exactly as when the user clicked the submit button when the page returns to the user. Any suggestions on this?

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• Choropleth mapping issue in R

  - by chasec

  I am trying to follow the tutorial described here: http://www.thisisthegreenroom.com/2009/choropleths-in-r/ The below code executes, but it is either not matching my dataset with the maps_counties data properly, or it isn't plotting it in the order I would expect. For example, the resulting areas for the greater NYC area show no density while random counties in PA show the highest density. The general format of my data table is: county state count fairfield connecticut 17 hartford connecticut 6 litchfield connecticut 3 new haven connecticut 12 ... ... westchester new york 70 yates new york 1 luzerne pennsylvania 1 Note this data is in order by state and then county and includes data for CT, NJ, NY, & PA. First, I read in my data set: library(maps) library(RColorBrewer) d <- read.table("gissum.txt", sep="\t", header=TRUE) #Concatenate state and county info to match maps library d$stcon <- paste(d$state, d$county, sep=",") #Color bins colors = brewer.pal(5, "PuBu") d$colorBuckets <- as.factor(as.numeric(cut(d$count,c(0,10,20,30,40,50,300)))) Here is my matching mapnames <- map("county",plot=FALSE)[4]$names colorsmatched <- d$colorBuckets [na.omit(match(mapnames ,d$stcon))] Plotting: map("county" ,c("new york","new jersey", "connecticut", "pennsylvania") ,col = colors[d$colorBuckets[na.omit(match(mapnames ,d$stcon))]] ,fill = TRUE ,resolution = 0 ,lty = 0 ,lwd= 0.5 ) map("state" ,c("new york","new jersey", "connecticut", "pennsylvania") ,col = "black" ,fill=FALSE ,add=TRUE ,lty=1 ,lwd=2 ) map("county" ,c("new york","new jersey", "connecticut", "pennsylvania") ,col = "black" ,fill=FALSE ,add=TRUE , lty=1 , lwd=.5 ) title(main="Respondent Home ZIP Codes by County") I am sure I am missing something basic re: the order in which the maps function plots items - but I can't seem to figure it out. Thanks for the help. Please let me know if you need any more information.

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• onActivityResult method not being called Android

  - by Chintan

  I am trying to send data from child activity to parent. But somehow, onActivityResult(..) is not getting called. here is code Parent activity selectedText.setOnTouchListener(new OnTouchListener() { public boolean onTouch(View v, MotionEvent event) { if (event.getActionMasked() == MotionEvent.ACTION_DOWN) { Intent intent = new Intent(Parents.this,Child.class); startActivityForResult(intent, 1); } return true; } }); @Override protected void onActivityResult(int requestCode, int resultCode, Intent data) { switch (requestCode) { case 1: if (resultCode == RESULT_OK) { if (data.hasExtra("selText")) { selectedText.setText(data.getExtras().getString( "selText")); } break; } } Child Activity: I can see selected value set in the setResult(). But after finish of child activity, it's not going back to parent activity. textListView.setOnItemClickListener(new OnItemClickListener() { @Override public void onItemClick(AdapterView<?> arg0, View arg1, int myItemInt, long arg3) { selectedFromList =(String) (textListView.getItemAtPosition(myItemInt)); Intent data = new Intent(); data.putExtra("selText", selectedFromList); setResult(RESULT_OK,data); finish(); } });

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• cakephp - form for belongsTo Model

  - by user1511579

  I createt the following model to link 2 relational tables: class Ficha extends AppModel { //public $useTable = 'ficha_seg'; var $primaryKey = 'id_ficha'; var $name = 'Ficha'; var $belongsTo = array( 'Perigo' => array( 'className' => 'Perigo', 'foreignKey' => false, 'conditions' => 'Perigo.id_fichas = Ficha.id_ficha' ) ); } Now, i have a form that requires data from the class Ficha, and then is redirected to another ctp page where i will input the data for the table "Perigos". However, since i'm still a newbie in cakephp i'm having difficult building that second form to insert the data on the table "Perigos". Here goes the code i built at the moment related to the second form: FichasController.php (the method where is it supposed to save the data on the table "Perigos": public function preencher_ficha(){ if ($this->request->is('ficha')) { $this->Ficha->create(); if ($this->Ficha->Perigo->save($this->request->data)) { $last_id=$this->Ficha->getLastInsertID(); $this->Session->setFlash('Your post has been updated '.$last_id.'.'); //$this->redirect(array('action' => 'preencher_ficha')); } else { $this->Session->setFlash('Unable to qualquer coisa your post.'); } } } The preencher_ficha.ctp file with the form: echo $this->Form->create('Ficha->Perigo', array('action' => 'index')); echo $this->Form->input('class_subst', array('label' => 'Classificação:')); echo $this->Form->input('simbolos_perigo', array('label' => 'Símbolos:')); echo $this->Form->input('frases_r', array('label' => 'Frases:')); echo $this->Form->end('Finalizar Ficha'); Here i guess the create part is wrong, but i think i have errors too in the controller part.

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• C++ pointer to objects

  - by Tony

  In C++ do you always have initialize a pointer to an object with the new keyword? Or can you just have this too: MyClass *myclass; myclass->DoSomething(); I thought this was a pointer allocated on the stack instead of the heap, but since objects are normally heap allocated, I think my theory is probably faulty?? Please advice.

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• Using an embedded DB (SQLite / SQL Compact) for Message Passing within an app?

  - by wk1989

  Hello, Just out of curiosity, for applications that have a fairly complicated module tree, would something like sqlite/sql compact edition work well for message passing? So if I have modules containing data such as: \SubsystemA\SubSubSysB\ModuleB\ModuleDataC, \SubSystemB\SubSubSystemC\ModuleA\ModuleDataX Using traditional message passing/routing, you have to go through intermediate modules in order to pass a message to ModuleB to request say ModuleDataC. Instead of doing that, if we we simply store "\SubsystemA\SubSubSysB\ModuleB\ModuleDataC" in a sqlite database, getting that data is as simple as a sql query and needs no routing and passing stuff around. Has anyone done this before? Even if you haven't, do you foresee any issues & performance impact? The only concern I have right now would be the passing of custom types, e.g. if ModuleDataC is a custom data structure or a pointer, I'll need some way of storing the data structure into the DB or storing the pointer into the DB. Thanks, JW EDIT One usage case I haven't thought about is when you want to send a message from ModuleA to ModuleB to get ModuleB to do something rather than just getting/setting data. Is it possible to do this using an embedded DB? I believe callback from the DB would be needed, how feasible is this?

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• Obtaining memory available to JVM at runtime

  - by Bo Tian

  I'm trying to sort a bunch of data such that that the size of data input to the program can be larger than the memory available to the JVM, and handling that requires external sort which is much slower than Quicksort. Is there any way of obtaining memory available to the JVM at runtime such that I could use in place sorting as much as possible, and only switch to Mergesort when data input is too large?

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• This process does not work in JavaScript: createElement() -> setAttribute('id') -> getElementById()

  - by kristovaher

  I was so sure that this question has been answered a thousand times before, but I've been unable to find an answer in StackOverflow. If there is already an answer and I was unable to find it then I apologize. I create hidden form elements dynamically like this: submitForm=document.getElementById('my-form'); var element=document.createElement('input'); element.id='hidden-form-data'; // or setAttribute('id','hidden-form-data'); element.name='my-hidden-form-data'; element.type='hidden'; element.value='my-data'; submitForm.appendChild(element); This works and the input field is created and it is taken into account when submitting the form. But I want to remove it after I have dynamically created it. I was sure that creating a new node this way would be 'correct' for browser and DOM, but apparently it is not. This returns null: element=document.getElementById('hidden-form-data'); if(element!=null){ element.parentNode.removeChild(element); } But it never gets removed and is always null. Is there any way I can remove a dynamically created node with an ID? Thank you! Please do not suggest jQuery, it's not possible to use jQuery for this, footprint is too heavy for such a small task I could not get a working answer from here, which was the closest thread I could find.

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• jQuery jqXHR - cancel chained calls, trigger error chain

  - by m0sa

  I am creating a ajax utility for interfacing with my server methods. I would like to leverage jQuery 1.5+ deferred methods from the object returned from the jQuery.ajax() call. The situation is following. The serverside method always returns a JSON object: { success: true|false, data: ... } The client-side utility initiates the ajax call like this var jqxhr = $.ajax({ ... }); And the problem area: jqxhr.success(function(data, textStatus, xhr) { if(!data || !data.success) { ???? // abort processing, trigger error } }); return jqxhr; // return to caller so he can attach his own handlers So the question is how to cancel invocation of all the callers appended success callbacks an trigger his error handler in the place mentioned with ???? ? The documentation says the deferred function invocation lists are FIFO, so my success handler is definitely the first one.

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• Combine MD5 hashes of multiple files

  - by user685869

  I have 7 files that I'm generating MD5 hashes for. The hashes are used to ensure that a remote copy of the data store is identical to the local copy. Unfortunately, the link between these two copies of the data is mind numbingly slow. Changes to the data are very rare but I have a requirement that the data be synchronized at all times (or as soon as possible). Rather than passing 7 different MD5 hashes across my (extremely slow) communications link, I'd like to generate the hash for each file and then combine these hashes into a single hash which I can then transfer and then re-calculate/use for comparison on the remote side. If the "combined hash" differs, then I'd start sending the 7 individual hashes to determine exactly which file(s) have been changed. For example, here are the MD5 hashes for the 7 files as of last week: 0709d609d69385255c496436eb50402c 709465a74411bd596595c7b9b158ae6a 4ab657320ef33e3d5eb498e4c13d41b7 3b49c6ab199994fd776bb63761414e72 0fc28c5a010fc3c06c0c930c88e31a15 c4ecd214662cac5aae0e53f6f252bf0e 8b086431e43148a2c2d943ba30d31cc6 I'd like to combine these hashes together such that I get a single unique value (perhaps another MD5 hash?) that I can then send to the remote system. On the remote system, I'd then perform the same calculation to determine if the data as a whole has been changed. If it has, then I'd start sending the individual hashes, etc. The most important factor is that my "combined hash" be short enough so that it uses less bandwidth than just sending all 7 hashes in the first place. I thought of writing the 7 MD5 hashes to a file and then hashing that file but is there a better way?

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• Error-invalid length for a base-64 char array

  - by dmenaria

  Hi , I have silverlight app that post some data to another web application ,the data to post is converted to base 64 using code byte[] byteArray = Encoding.UTF8.GetBytes(sDataToPost); sDataToPost = Convert.ToBase64String(byteArray); Another webapplication get the data using the code strText = System.Text.Encoding.ASCII.GetString(System.Convert.FromBase64String(postedData)); But it gives the exception invalid length for a base-64 char array Thanks in Advance DNM

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• Cannot running next process when a variable save no value

  - by bruine

  First, I wanna compare between 2 tables tb_wrapper and tb_summary to get the data in the tb_wrapper that doesn't exist in the tb_summary then save in $link. If I don't get the same data, I want to print the result $link. When I don't get the not same data, I want it to go to another process. Here's the code : $q2 = mysql_query(" SELECT a.doc_url FROM tb_wrapper a LEFT JOIN tb_summary b ON a.doc_name = b.doc_summ WHERE b.doc_summ IS NULL"); while ($row = mysql_fetch_array($q2)){ $link = $row['doc_url']; if (!$link){ include 'next_process.php'; } else { print_r($link); } } it doesn't work. When I don't get the not same data or $link not save a value. table : CREATE TABLE tb1 (`id` int, `doc_name` varchar(100), `doc_url` varchar(50)) } CREATE TABLE tb2 (`id` int, `doc_summ` varchar(100)) }

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• How can we use order by in SQLite

  - by Nidhi

  There is two field in my data base id(primary key) and name. I want arrange my data in descending order by using id

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• Rails Testing Question

  - by Steve

  Hi, I am trying to test a functionality, which inserts few details into the DB. In the test.log, it shows the insert command that is generated and also the log messages that I have placed to show the progress and everything seems to be working fine except the actual data is not getting inserted into the DB. I am checking whether data is inserted in db/test.sqlite3. No exception is generated when the test cases are run. Is there a setting, which I have to set inorder to insert data into the test DB? or am i missing anything else Thanks

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• How to create unique user key

  - by Grayson Mitchell

  Scenario: I have a fairly generic table (Data), that has an identity column. The data in this table is grouped (lets say by city). The users need an identifier in order for printing on paper forms, etc. The users can only access their cites data, so if they use the identity column for this purpose they will see odd numbers (e.g. a 'New York' user might see 1,37,2028... as the listed keys. Idealy they would see 1,2,3... (or something similar) The problem of course is concurrency, this being a web application you can't just have something like: UserId = Select Count(*)+1 from Data Where City='New York' Has anyone come up with any cunning ways around this problem?

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• extract transform load

  - by mitch

  Wikipedia defines a 'typical' ETL cycle as : Cycle initiation Build reference data Extract (from sources) Validate Transform (clean, apply business rules, check for data integrity, create aggregates or disaggregates) Stage (load into staging tables, if used) Audit reports (for example, on compliance with business rules. Also, in case of failure, helps to diagnose/repair) Publish (to target tables) Archive Clean up ..What is meant by 'Build reference data'?

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• Trying to packetize TCP with non-blocking IO is hard! Am I doing something wrong?

  - by Ricket

  Oh how I wish TCP was packet-based like UDP is! But alas, that's not the case, so I'm trying to implement my own packet layer. Here's the chain of events so far (ignoring writing packets) Oh, and my Packets are very simply structured: two unsigned bytes for length, and then byte[length] data. (I can't imagine if they were any more complex, I'd be up to my ears in if statements!) Server is in an infinite loop, accepting connections and adding them to a list of Connections. PacketGatherer (another thread) uses a Selector to figure out which Connection.SocketChannels are ready for reading. It loops over the results and tells each Connection to read(). Each Connection has a partial IncomingPacket and a list of Packets which have been fully read and are waiting to be processed. On read(): Tell the partial IncomingPacket to read more data. (IncomingPacket.readData below) If it's done reading (IncomingPacket.complete()), make a Packet from it and stick the Packet into the list waiting to be processed and then replace it with a new IncomingPacket. There are a couple problems with this. First, only one packet is being read at a time. If the IncomingPacket needs only one more byte, then only one byte is read this pass. This can of course be fixed with a loop but it starts to get sorta complicated and I wonder if there is a better overall way. Second, the logic in IncomingPacket is a little bit crazy, to be able to read the two bytes for the length and then read the actual data. Here is the code, boiled down for quick & easy reading: int readBytes; // number of total bytes read so far byte length1, length2; // each byte in an unsigned short int (see getLength()) public int getLength() { // will be inaccurate if readBytes < 2 return (int)(length1 << 8 | length2); } public void readData(SocketChannel c) { if (readBytes < 2) { // we don't yet know the length of the actual data ByteBuffer lengthBuffer = ByteBuffer.allocate(2 - readBytes); numBytesRead = c.read(lengthBuffer); if(readBytes == 0) { if(numBytesRead >= 1) length1 = lengthBuffer.get(); if(numBytesRead == 2) length2 = lengthBuffer.get(); } else if(readBytes == 1) { if(numBytesRead == 1) length2 = lengthBuffer.get(); } readBytes += numBytesRead; } if(readBytes >= 2) { // then we know we have the entire length variable // lazily-instantiate data buffers based on getLength() // read into data buffers, increment readBytes // (does not read more than the amount of this packet, so it does not // need to handle overflow into the next packet's data) } } public boolean complete() { return (readBytes > 2 && readBytes == getLength()+2); } Basically I need feedback on my code. Please suggest any improvements. Even overhauling my entire system would be okay, if you have suggestions for how better to implement the whole thing. Book recommendations are welcome too; I love books. I just get the feeling that something isn't quite right.

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• Update existing columns and rows within csv file using Python

  - by wilbev

  So I've been attempting to use the csv module in Python to add data to existing rows and columns, but only specific columns of each row. So for examples let's say my existing csv file has the following: id, name, city, age 1, Ed,, 34 2, Pat,, 23 So basically the city of each person is missing, so I would like to update each row with that person's city. However, the writerow method only seems replace the existing data within the csv file. Changing the open file to append mode just adds the data to a new row. Is there any way to skip the existing data, and only add the city to each row? Thanks

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• SQL Server float datatype

  - by Martin Smith

  The documentation for SQL Server Float says Approximate-number data types for use with floating point numeric data. Floating point data is approximate; therefore, not all values in the data type range can be represented exactly. Which is what I expected it to say. If that is the case though why does the following return 'Yes' in SQL Server DECLARE @D float DECLARE @E float set @D = 0.1 set @E = 0.5 IF ((@D + @D + @D + @D +@D) = @E) BEGIN PRINT 'YES' END ELSE BEGIN PRINT 'NO' END but the equivalent C++ program returns "No"? #include <iostream> using namespace std; int main() { float d = 0.1F; float e = 0.5F; if((d+d+d+d+d) == e) { cout << "Yes"; } else { cout << "No"; } }

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• Using KnockoutJS 2.2.0 & jQuery 1.8.2 remove all bindings from all children of #someDiv

  - by Nukeface

  I'm wanting to delete All bindings (ko.cleanNode) from all child elements of a certain div. Must be a noobie question but I can't figure out how to use jQuery to loop through all childre, grand-children, great-grand-children, etc. whilst having KnockoutJS remove the bindings of all the DOM elements. I do NOT want to remove the elements from the DOM. This is a single page application, therefore the elements are pre-loaded as embedded resources and don't get resend to a client if they were to visit the page again. If a client revisits that part of the application I'll have a function rebind the necessary elements, which currently works fine. Current setup: <html> <head> //loading all resources </head> <body> //load first element using some obscure setup <div id="firsPage" data-role="page"> <div data-role="header">@Global.header</div> <div data-role="fieldcontain"> <label for="firstInput" /> <input id="firstInput some other stuff /> </div> <div data-role="datebox <!-- some settings --> > //creates table using jQuery mobile (lots of (great-)(grand-)children) </div> <div data-role="fieldcontain"> <div id="secondInput"> <div class="checklist"> <ul> <li /> <li /> </ul> </div> </div> </div> </div> //Here the whole thing starts again <div id="secondPage" data-role="page"> <!-- repeat above innerHTML in your mind ;) --> </div> //And here again! and again... </body> The problem I'm having is that bindings of the children don't seem to get "cleaned up" when i use ko.cleanNode($('#firstPage')[0]); Or when I get the Element into a variable and then format it to ko.cleanNode($element). Is there a way to do this? Been staring at it for a good few hours now, so probably overlooking a way too obvious way of doing it... Thanks!

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