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• `enable_shared_from_this` has a non-virtual destructor

  - by Shtééf

  I have a pet project with which I experiment with new features of the upcoming C++0x standard. While I have experience with C, I'm fairly new to C++. To train myself into best practices, (besides reading a lot), I have enabled some strict compiler parameters (using GCC 4.4.1): -std=c++0x -Werror -Wall -Winline -Weffc++ -pedantic-errors This has worked fine for me. Until now, I have been able to resolve all obstacles. However, I have a need for enable_shared_from_this, and this is causing me problems. I get the following warning (error, in my case) when compiling my code (probably triggered by -Weffc++): base class ‘class std::enable_shared_from_this<Package>’ has a non-virtual destructor So basically, I'm a bit bugged by this implementation of enable_shared_from_this, because: A destructor of a class that is intended for subclassing should always be virtual, IMHO. The destructor is empty, why have it at all? I can't imagine anyone would want to delete their instance by reference to enable_shared_from_this. But I'm looking for ways to deal with this, so my question is really, is there a proper way to deal with this? And: am I correct in thinking that this destructor is bogus, or is there a real purpose to it?

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• selection issue in listview or TreeView

  - by Maneesh

  Hello i have a list view control, While the form is being loaded i fill the list, i have aprrox. say 100+ items. While filling i check some parameters and decide which item/row need to be selected. i set the Selected property to true... refer the code below: some lines here ..... ListViewItem listViewItem = new ListViewItem("COL1"); listViewItem.SubItems.Add("COL2"); check for some condition and then listViewItem.Selected = true; this.m_lstViewCtrl.Items.Add(listViewItem); This does select the item, there are no issues with it... however, say the ctrl is sized to see onlu say some 15 items, but the selection is say some 35th item.... currently the scroll bar appears the item is selected but i have to scroll to see what was selected? is it possible to scroll to the selected item so that is selection is clearly visible... Will the same apply for a Treeview?

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• Passing a outside variable into a <asp:sqldatasource> tag. ASP.NET 2.0

  - by MadMAxJr

  I'm designing some VB based ASP.NET 2.0, and I am trying to make more use of the various ASP tags that visual studio provides, rather than hand writing everything in the code-behind. I want to pass in an outside variable from the Session to identify who the user is for the query. <asp:sqldatasource id="DataStores" runat="server" connectionstring="<%$ ConnectionStrings:MY_CONNECTION %>" providername="<%$ ConnectionStrings:MY_CONNECTION.ProviderName %>" selectcommand="SELECT THING1, THING2 FROM DATA_TABLE WHERE (THING2 IN (SELECT THING2 FROM RELATED_DATA_TABLE WHERE (USERNAME = @user)))" onselecting="Data_Stores_Selecting"> <SelectParameters> <asp:parameter name="user" defaultvalue ="" /> </SelectParameters> </asp:sqldatasource> And on my code behind I have: Protected Sub Data_Stores_Selecting(ByVal sender As Object, ByVal e As System.Web.UI.WebControls.SqlDataSourceSelectingEventArgs) Handles Data_Stores.Selecting e.Command.Parameters("user").Value = Session("userid") End Sub Oracle squaks at me with ORA-01036, illegal variable name. Am I declaring the variable wrong in the query? I thought external variables share the same name with a @ prefixed. from what I understand, this should be placing the value I want into the query when it executes the select. EDIT: Okay, thanks for the advice so far, first error was corrected, I need to use : and not @ for the variable declaration in the query. Now it generates an ORA-01745 invalid host/bind variable name. EDIT AGAIN: Okay, looks like user was a reserved word. It works now! Thanks for other points of view on this one. I hadn't thought of that approach.

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• Compiler turning a string& into a basic_string<>&

  - by Shtong

  Hello I'm coming back to C++ after long years spent on other technologies and i'm stuck on some weird behavior when calling some methods taking std::string as parameters : An example of call : LocalNodeConfiguration *LocalNodeConfiguration::ReadFromFile(std::string & path) { // ... throw configuration_file_error(string("Configuration file empty"), path); // ... } When I compile I get this (I cropped file names for readability) : /usr/bin/g++ -g -I/home/shtong/Dev/OmegaNoc/build -I/usr/share/include/boost-1.41.0 -o CMakeFiles/OmegaNocInternals.dir/configuration/localNodeConfiguration.cxx.o -c /home/shtong/Dev/OmegaNoc/source/configuration/localNodeConfiguration.cxx .../localNodeConfiguration.cxx: In static member function ‘static OmegaNoc::LocalNodeConfiguration* OmegaNoc::LocalNodeConfiguration::ReadFromFile(std::string&)’: .../localNodeConfiguration.cxx:72: error: no matching function for call to ‘OmegaNoc::configuration_file_error::configuration_file_error(std::string, std::basic_string<char, std::char_traits<char>, std::allocator<char> >&)’ .../configurationManager.hxx:25: note: candidates are: OmegaNoc::configuration_file_error::configuration_file_error(std::string&, std::string&) .../configurationManager.hxx:22: note: OmegaNoc::configuration_file_error::configuration_file_error(const OmegaNoc::configuration_file_error&) So as I understand it, the compiler is considering that my path parameter turned into a basic_string at some point, thus not finding the constructor overload I want to use. But I don't really get why this transformation happened. Some search on the net suggested me to use g++ but I was already using it. So any other advice would be appreciated :) Thanks

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• Refactoring routes - serving different layouts

  - by dmclark

  As a Rails NOOB, I started with a routes.rb of: ActionController::Routing::Routes.draw do |map| map.resources :events map.connect 'affiliates/list', :controller => "affiliates", :action => "list" map.connect 'affiliates/regenerate_thumb/:id', :controller => "affiliates", :action => "regenerate_thumb" map.connect 'affiliates/state/:id.:format', :controller => "affiliates", :action => "find_by_state" map.connect 'affiliates/getfeed', :controller => "affiliates", :action => "feed" map.resources :affiliates, :has_many => :events map.connect ":controller/:action" map.connect '', :controller => "affiliates" map.connect ":controller/:action/:id" map.connect ":controller/:action/:id/:format" end and i'm trying to tighten it up. and I've gotten as far as: ActionController::Routing::Routes.draw do |map| map.resources :events, :only => "index" map.resources :affiliates do |affiliates| affiliates.resources :has_many => :events affiliates.resources :collection => { :list => :get, :regenerate_thumb => "regenerate_thumb" } end # map.connect 'affiliates/regenerate_thumb/:id', :controller => "affiliates", :action => "regenerate_thumb" map.connect 'affiliates/state/:id.:format', :controller => "affiliates", :action => "find_by_state" map.connect 'affiliates/getfeed', :controller => "affiliates", :action => "feed" map.root :affiliates end what is confusing to me is routes vs parameters.. For example, I realized that the only difference between list and index is HOW it is rendered, rather than WHAT is rendered. Having a different action (as I do now) feels wrong but I can't figure out he right way. Thanks

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• Using external SOAP service in Workflow service

  - by whirlwin

  I am using the .NET 4 framework and have made a WCF Workflow Service Application. I want to use a SOAP web service (.NET 3.5) I have running in another instance of VS. The only method that is exposed is the following: [WebMethod] public string Reverse(string input) { char[] chars = input.ToCharArray(); Array.Reverse(chars); return new string(chars); } I have used the following steps to add the service in my Workflow: Add Service Reference Provided the WSDL (the operation shows in the Operations box as expected) Clicked OK Build the solution to ensure that the service shows in my toolbox Drag the service from the toolbox into the workflow However, when I look at the properties of the service in the workflow, there is no way to specify the input argument or where to store the result of the invocation of the service. I only have the option of specifying some obscure parameters such as Body:InArgument<ReverseRequestBody and outBody:OutArgument<ReverseResponseBody (none of which are strings). Here is a screenshot depicting the properties of the service in the workflow: My question is therefore: Is it possible at all to use the SOAP service by specifying a string as the input argument (like it is meant to be used), and also assign the result to a workflow variable?

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• Translate SQL to NHibernate Query

  - by Thad

  I have a SQL query that I would like to translate to nhibernate criteria, but I have not found a way to generate the MatchCount field. I tried adding it using a sqlprojection but I could not find a place to set the parameters. SELECT (CASE WHEN LEFT([FirstName], LEN(@Text0)) = @Text0 OR LEFT([FirstName], LEN(@Text1)) = @Text1 OR LEFT([FirstName], LEN(@Text2)) = @Text2 THEN 1 ELSE 0 END + CASE WHEN LEFT([LastName], LEN(@Text0)) = @Text0 OR LEFT([LastName], LEN(@Text1)) = @Text1 OR LEFT([LastName], LEN(@Text2)) = @Text2 THEN 1 ELSE 0 END + CASE WHEN LEFT([PreferredName], LEN(@Text0)) = @Text0 OR LEFT([PreferredName], LEN(@Text1)) = @Text1 OR LEFT([PreferredName], LEN(@Text2)) = @Text2 THEN 1 ELSE 0 END) AS MatchCount , * FROM [client].[Individual] WHERE ( [FirstName] LIKE @Text0 + '%' OR [FirstName] LIKE @Text1 + '%' OR [FirstName] LIKE @Text2 + '%' OR [LastName] LIKE @Text0 + '%' OR [LastName] LIKE @Text1 + '%' OR [LastName] LIKE @Text2 + '%' OR [PreferredName] LIKE @Text0 + '%' OR [PreferredName] LIKE @Text1 + '%' OR [PreferredName] LIKE @Text2 + '%' ) ORDER BY (CASE WHEN LEFT([FirstName], LEN(@Text0)) = @Text0 OR LEFT([FirstName], LEN(@Text1)) = @Text1 OR LEFT([FirstName], LEN(@Text2)) = @Text2 THEN 1 ELSE 0 END + CASE WHEN LEFT([LastName], LEN(@Text0)) = @Text0 OR LEFT([LastName], LEN(@Text1)) = @Text1 OR LEFT([LastName], LEN(@Text2)) = @Text2 THEN 1 ELSE 0 END + CASE WHEN LEFT([PreferredName], LEN(@Text0)) = @Text0 OR LEFT([PreferredName], LEN(@Text1)) = @Text1 OR LEFT([PreferredName], LEN(@Text2)) = @Text2 THEN 1 ELSE 0 END) DESC And yes, this is a ugly statement. Hate having a sql statement in the middle of everthing. Note: There is paging involved and I would prefer not returning all the data to the app server before cutting it down.

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• Problems with video conversions through the web (local host)

  - by ron-d

  Hello, I get the following errors when I attempt video format conversions called from the local host: “An invalid media type was specified” for M4V to WMV conversions. “One or more arguments are invalid” for MP4 to WMV conversions. Here are the details of the problems: I’ve written a dll in C# that accepts videos in the formats AVI, WMV, M4V and MP4 and performs the following actions: Creates a copy of the input video in WMV format . Creates a WAV file of the input video audio portion. Creates a JPG image from a frame of the input video. I attached the dll to an ASP.NET web project that performs the dll actions. When tested through the developer studio, the actions are performed as intended for all formats. When I place the web project in place to be read when the local host is called through the web browser, the following behavior takes place: WMV format: All actions performed as intended. AVI format: Creates WMV file – OK Creates JPG image – OK Creates empty WAV file – problem. M4V format: Creates empty WAV file – problem. Does not create WMV file -problem Does not create JPG file –problem Throws me the error “An invalid media type was specified” MP4 format: Creates empty WAV file – problem. Does not create WMV file -problem Does not create JPG file –problem Throws me the error “One or more arguments are invalid” When I check their security property, all the files have the same permission access parameters (when I check their security property. Can anyone guide me as to how to solve these problems when the web project is called from the local host? Thank you.

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• Is there anything bad in declaring nested class inside interface in java?

  - by Roman

  I have an interface ProductService with method findByCriteria. This method had a long list of nullable parameters, like productName, maxCost, minCost, producer and so on. I refactored this method by introducing Parameter Object. I created class SearchCriteria and now method signature looks like this: findByCriteria (SearchCriteria criteria) I thought that instances of SearchCriteria are only created by method callers and are only used inside findByCriteria method, i.e.: void processRequest() { SearchCriteria criteria = new SearchCriteria () .withMaxCost (maxCost) ....... .withProducer (producer); List<Product> products = productService.findByCriteria (criteria); .... } and List<Product> findByCriteria(SearchCriteria criteria) { return doSmthAndReturnResult(criteria.getMaxCost(), criteria.getProducer()); } So I did not want to create a separate public class for SearchCriteria and put it inside ProductServiceInterface: public interface ProductService { List<Product> findByCriteria (SearchCriteria criteria); static class SearchCriteria { ... } } Is there anything bad with this interface? Where whould you place SearchCriteria class?

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• Best way of showing more results with javascript/css

  - by Ricardo Neves

  I'm developing a website and i'm having troubles showing the search results to the user the way I want. Basically, after the user search, the page makes a couple of ajax requests and as soon as a response arrive it appends the info to a specific element on my page. Each results is shown as a line... The problem is that in most case there are going to be more than 1000 results and this would make the page have a large scroll. My idea was to show only the first 15 results and when the user clicks "show more" the element would expand and show the next 15 results and so on... This would be easier to do if the website wasn't responsive, but because it is I can't find the proper way of implementing what I want without lowering the website perfomance. I have "2 ideas": The first is by using something like #element .div:nth-child(-n+15) on my css and figure a way of changing the "15" to how much results I want to show... I don't know if this can be done. Is it possible to call css rules with parameters? Maybe with less css? The second option is probably a bad option if i don't want to lower the website performance. Using javascript I would check if there is a specific css class(like .show-15 .show30 .show45) and add that class to my element and if it don't exist, create it somehow.. Any help would be appreciated.

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• SQL Server 2008 Stored Proc suddenly returns -1

  - by aaginor

  I use the following stored procedure from my SQL Server 2008 database to return a value to my C#-Program ALTER PROCEDURE [dbo].[getArticleBelongsToCatsCount] @id int AS BEGIN SET NOCOUNT ON; DECLARE @result int; set @result = (SELECT COUNT(*) FROM art_in_cat WHERE child_id = @id); return @result; END I use a SQLCommand-Object to call this Stored Procedure public int ExecuteNonQuery() { try { return _command.ExecuteNonQuery(); } catch (Exception e) { Logger.instance.ErrorRoutine(e, "Text: " + _command.CommandText); return -1; } } Till recently, everything works fine. All of a sudden, the stored procedure returned -1. At first, I suspected, that the ExecuteNonQuery-Command would have caused and Exception, but when stepping through the function, it shows that no Exception is thrown and the return value comes directly from return _command.ExecuteNonQuery(); I checked following parameters and they were as expected: - Connection object was set to the correct database with correct access values - the parameter for the SP was there and contained the right type, direction and value Then I checked the SP via SQLManager, I used the same value for the parameter like the one for which my C# brings -1 as result (btw. I checked some more parameter values in my C' program and they ALL returned -1) but in the manager, the SP returns the correct value. It looks like the call from my C# prog is somehow bugged, but as I don't get any error (it's just the -1 from the SP), I have no idea, where to look for a solution.

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• Ruby On Rails - Contact form not sending email via localhost

  - by anonymousxxx

  similar problem Rails contact form not working guides: https://github.com/thomasklemm/email_form_rails rails 3.2.x app\models\message.rb class Message include ActiveAttr::Model include ActiveModel::Validations attribute :name attribute :email attribute :subject attribute :body attr_accessible :name, :email, :subject, :body validates_presence_of :name validates_presence_of :email validates :email, email_format: { message: "is not looking like a valid email address"} validates_presence_of :subject validates_length_of :body, maximum: 500 end app\mailers\contact_form.rb class ContactForm < ActionMailer::Base default from: "[email protected]" default to: "[email protected]" def email_form(message) @message = message mail subject: "#{message.subject} #{message.name}" mail body: "#{message.body}" end end development.rb config.action_mailer.delivery_method = :smtp config.action_mailer.perform_deliveries = true config.action_mailer.smtp_settings = { :address => "smtp.gmail.com", :port => 587, :domain => "mydomain.com", :user_name => "[email protected]", :password => "mypassword", :authentication => :plain, :enable_starttls_auto => true } config.action_mailer.default_url_options = { :host => "localhost:3000" } output in command Started POST "/email" for 127.0.0.1 at 2012-09-04 22:10:40 +0700 Processing by HomeController#send_email_form as HTML Parameters: {"utf8"="v", "authenticity_token"="w39BLqCrjTMm4RRi/Sm5hZoEpcw46 npyRy/RS0h48x0=", "message"={"name"="anonymousxxx", "email"="[email protected]", "subject"="Test", "body"="send email"}, "commit"="Create Message"} Redirected to localhost:3000/home/contact Completed 302 Found in 1ms (ActiveRecord: 0.0ms) but email (message) no receive my email,..

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• MySQL Casting in C#

  - by user798080

  Okay, so I'm attempting to print out the contents of a table in a comma-separated file. using (OdbcCommand com = new OdbcCommand("SELECT * FROM pie_data WHERE Pie_ID = ?", con)) { com.Parameters.AddWithValue("", Request.Form["pie_id"]); com.ExecuteNonQuery(); using (OdbcDataReader reader = com.ExecuteReader()) { string finalstring = ""; while (reader.Read()) { finalstring = reader.GetString(9) + ","; for (int i = 0; i <= 8; i = i + 1) { finalstring = finalstring + reader.GetString(i) + ","; } } } Response.Write(finalstring); noredirect = 1; } My table layout is: CREATE TABLE `rent_data` ( `Pies` INT(10) UNSIGNED NOT NULL, `Name` VARCHAR(85) NOT NULL, `Email` VARCHAR(85) NOT NULL, `Pie_Rent` DATE NOT NULL, `Rent_To` DATE NOT NULL, `Returned_Date` DATE NULL DEFAULT NULL, `Place` VARCHAR(100) NOT NULL, `Purpose` MEDIUMTEXT NOT NULL, `Comments` MEDIUMTEXT NULL, `Pie_ID` SMALLINT(5) UNSIGNED ZEROFILL NOT NULL, INDEX `Pie_ID` (`Equipment_ID`) ) The error I'm getting is this: Exception Details: System.InvalidCastException: Unable to cast object of type 'System.Int64' to type 'System.String'. On the line: finalstring = finalstring + reader.GetString(i) + ",";

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• Stored procedure for generic MERGE

  - by GilliVilla

  I have a set of 10 tables in a database (DB1). And there are 10 tables in another database (DB2) with exact same schema on the same SQL Server 2008 R2 database server machine. The 10 tables in DB1 are frequently updated with data. I intend to write a stored procedure that would run once every day for synchronizing the 10 tables in DB1 with DB2. The stored procedure would make use of the MERGE statement. Now, my aim is to make this as generic and parametrized as possible. That is, accommodate for more tables down the line... and accommodate different source and target DB names. Definitely no hard coding is intended. This is my algorithm so far: Have the database names as parameters Have the first query within the stored procedure... result in giving the names of the 10 tables from a lookup table (this can be 10, 20 or whatever) Have a generic MERGE statement that does the sync for each of the above set of tables (based on primary key?) This is where I need more inputs on. What is the best way to achieve this stored procedure? SQL syntax would be helpful.

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• Communication with different social networks, strategy pattern?

  - by bclaessens

  Hi For the last few days I've been thinking how I can solve the following programming problem and find the ideal, flexible programming structure. (note: I'm using Flash as my platform technology but that shouldn't matter since I'm just looking for the ideal design pattern). Our Flash website has multiple situations in which it has to communicate with different social networks (Facebook, Netlog and Skyrock). Now, the communication strategy doesn't have to change multiple times over one "run". The strategy should be picked once (at launch time) for that session. The real problem is the way the communication works between each social network and our website. Some networks force us to ask for a token, others force us to use a webservice, yet another forces us to set up its communication through javascript. The problem becomes more complicated when our website has to run in each network's canvas. Which results in even more (different) ways of communicating. To sum up, our website has to work in the following cases: standalone on the campaign website url (user chooses their favourite network) communicate with netlog OR communicate with facebook OR communicate with skyrock run in a netlog canvas and log in automatically (website checks for netlog parameters) run in a facebook canvas and log in automatically (website checks for facebook params) run in a skyrock canvas and log in automatically (website checks for skyrock params) As you can see, our website needs 6 different ways to communicate with a social network. To be honest, the actual significant difference between all communication strategies is the way they have to connect to their individual network (as stated above in my example). Posting an image, make a comment, ... is the same whether it runs standalone or in the canvas url. WARNING: posting an image, posting a comment DOES differ from network to network. Should I use the strategy pattern and make 6 different communication strategies or is there a better way? An example would be great but isn't required ;) Thanks in advance

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• Geohashing - recursively find neighbors of neighbors

  - by itsme

  I am now looking for an elegant algorithm to recursively find neighbors of neighbors with the geohashing algorithm (http://www.geohash.org). Basically take a central geohash, and then get the first 'ring' of same-size hashes around it (8 elements), then, in the next step, get the next ring around the first etc. etc. Have you heard of an elegant way to do so? Brute force could be to take each neighbor and get their neighbors simply ignoring the massive overlap. Neighbors around one central geohash has been solved many times (here e.g. in Ruby: http://github.com/masuidrive/pr_geohash/blob/master/lib/pr_geohash.rb) Edit for clarification: Current solution, with passing in a center key and a direction, like this (with corresponding lookup-tables): def adjacent(geohash, dir) base, lastChr = geohash[0..-2], geohash[-1,1] type = (geohash.length % 2)==1 ? :odd : :even if BORDERS[dir][type].include?(lastChr) base = adjacent(base, dir) end base + BASE32[NEIGHBORS[dir][type].index(lastChr),1] end (extract from Yuichiro MASUI's lib) I say this approach will get ugly soon, because directions gets ugly once we are in ring two or three. The algorithm would ideally simply take two parameters, the center area and the distance from 0 being the center geohash only (["u0m"] and 1 being the first ring made of 8 geohashes of the same size around it (= [["u0t", "u0w"], ["u0q", "u0n"], ["u0j", "u0h"], ["u0k", "u0s"]]). two being the second ring with 16 areas around the first ring etc. Do you see any way to deduce the 'rings' from the bits in an elegant way?

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• What is the fastest way to get a DataTable into SQL Server?

  - by John Gietzen

  I have a DataTable in memory that I need to dump straight into a SQL Server temp table. After the data has been inserted, I transform it a little bit, and then insert a subset of those records into a permanent table. The most time consuming part of this operation is getting the data into the temp table. Now, I have to use temp tables, because more than one copy of this app is running at once, and I need a layer of isolation until the actual insert into the permanent table happens. What is the fastest way to do a bulk insert from a C# DataTable into a SQL Temp Table? I can't use any 3rd party tools for this, since I am transforming the data in memory. My current method is to create a parameterized SqlCommand: INSERT INTO #table (col1, col2, ... col200) VALUES (@col1, @col2, ... @col200) and then for each row, clear and set the parameters and execute. There has to be a more efficient way. I'm able to read and write the records on disk in a matter of seconds...

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• Indexing/Performance strategies for vast amount of the same value

  - by DrColossos

  Base information: This is in context to the indexing process of OpenStreetMap data. To simplify the question: the core information is divided into 3 main types with value "W", "R", "N" (VARCHAR(1)). The table has somewhere around ~75M rows, all columns with "W" make up ~42M rows. Existing indexes are not relevant to this question. Now the question itself: The indexing of the data is done via an procedure. Inside this procedure, there are some loops that do the following: [...] SELECT * FROM table WHERE the_key = "W"; [...] The results get looped again and the above query itself is also in a loop. This takes a lot of time and slows down the process massivly. An indexon the_key is obviously useless since all the values that the index might use are the same ("W"). The script itself is running with a speed that is OK, only the SELECTing takes very long. Do I need to create a "special" kind of index that takes this into account and makes the SELECT quicker? If so, which one? need to tune some of the server parameters (they are already tuned and the result that they deliver seem to be good. If needed, I can post them)? have to live with the speed and simply get more hardware to gain more power (Tim Taylor grunt grunt)? Any alternatives to the above points (except rewriting it or not using it)?

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• Approach for caching data from data logger

  - by filip-fku

  Greetings, I've been working on a C#.NET app that interacts with a data logger. The user can query and obtain logs for a specified time period, and view plots of the data. Typically a new data log is created every minute and stores a measurement for a few parameters. To get meaningful information out of the logger, a reasonable number of logs need to be acquired - data for at least a few days. The hardware interface is a UART to USB module on the device, which restricts transfers to a maximum of about 30 logs/second. This becomes quite slow when reading in the data acquired over a number of days/weeks. What I would like to do is improve the perceived performance for the user. I realize that with the hardware speed limitation the user will have to wait for the full download cycle at least the first time they acquire a larger set of data. My goal is to cache all data seen by the app, so that it can be obtained faster if ever requested again. The approach I have been considering is to use a light database, like SqlServerCe, that can store the data logs as they are received. I am then hoping to first search the cache prior to querying a device for logs. The cache would be updated with any logs obtained by the request that were not already cached. Finally my question - would you consider this to be a good approach? Are there any better alternatives you can think of? I've tried to search SO and Google for reinforcement of the idea, but I mostly run into discussions of web request/content caching. Thanks for any feedback!

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• Extracting DCT coefficients from encoded images and video

  - by misha

  Is there a way to easily extract the DCT coefficients (and quantization parameters) from encoded images and video? Any decoder software must be using them to decode block-DCT encoded images and video. So I'm pretty sure the decoder knows what they are. Is there a way to expose them to whomever is using the decoder? I'm implementing some video quality assessment algorithms that work directly in the DCT domain. Currently, the majority of my code uses OpenCV, so it would be great if anyone knows of a solution using that framework. I don't mind using other libraries (perhaps libjpeg, but that seems to be for still images only), but my primary concern is to do as little format-specific work as possible (I don't want to reinvent the wheel and write my own decoders). I want to be able to open any video/image (H.264, MPEG, JPEG, etc) that OpenCV can open, and if it's block DCT-encoded, to get the DCT coefficients. In the worst case, I know that I can write up my own block DCT code, run the decompressed frames/images through it and then I'd be back in the DCT domain. That's hardly an elegant solution, and I hope I can do better. Presently, I use the fairly common OpenCV boilerplate to open images: IplImage *image = cvLoadImage(filename); // Run quality assessment metric The code I'm using for video is equally trivial: CvCapture *capture = cvCaptureFromAVI(filename); while (cvGrabFrame(capture)) { IplImage *frame = cvRetrieveFrame(capture); // Run quality assessment metric on frame } cvReleaseCapture(&capture); In both cases, I get a 3-channel IplImage in BGR format. Is there any way I can get the DCT coefficients as well?

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• What are the original reasons for ToString() in Java and .NET?

  - by d.

  I've used ToString() modestly in the past and I've found it very useful in many circumstances. However, my usage of this method would hardly justify to put this method in none other than System.Object. My wild guess is that, at some point during the work carried out and meetings held to come up with the initial design of the .NET framework, it was decided that it was necessary - or at least extremely useful - to include a ToString() method that would be implemented by everything in the .NET framework. Does anyone know what the exact reasons were? Am I missing a ton of situations where ToString() proves useful enough as to be part of System.Object? What were the original reasons for ToString()? Thanks a lot! PS - Again: I'm not questioning the method or implying that it's not useful, I'm just curious to know what makes it SO useful as to be placed in System.Object. Side note - Imagine this: AnyDotNetNativeClass someInitialObject = new AnyDotNetNativeClass([some constructor parameters]); AnyDotNetNativeClass initialObjectFullCopy = AnyDotNetNativeClass.FromString(someInitialObject.ToString()); Wouldn't this be cool? EDIT(1): (A) - Based on some answers, it seems that .NET languages inherited this from Java. So, I'm adding "Java" to the subject and to the tags as well. If someone knows the reasons why this was implemented in Java then please shed some light! (B) - Static hypothetical FromString vs Serialization: sure, but that's quite a different story, right?

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• Web scrapping from a Google Chrome extension

  - by limoragni

  I've started to develop a Chrome extension to navigate and prform actions on a website. Until now the extension is able to receive a couple of parameters and check a set of radio-buttons, fill in a few inputs of a form and then submit it. What I want to do now is to repeat the process, but I'm stuck when the page is reloaded. And I don't know how can I do to make the script reacts to the finish of the request. The workflow I want to achieve is the following (is for automaticly copying a certain object): Popup side Enter the number of the Master object to copy Enter the base name of the copies (example Mod, so the I can iterate and add mod1, mod2, modn) Enter the number of copies Background side Select master Select standard options Fill in inputs Submit form Wait for the page to complete the request and continue to the next copy. (here I need help) The problem is on the repetition, the rest is taking care of. I assume that must be a way of dealing with requests. Any ideas? By the way I'm doing it all with the extension and tabs methods of google chrome plus javascript and jquery.

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• System Calls in windows & Native API?

  - by claws

  Recently I've been using lot of Assembly language in *NIX operating systems. I was wondering about the windows domain. Calling convention in linux: mov $SYS_Call_NUM, %eax mov $param1 , %ebx mov $param2 , %ecx int $0x80 Thats it. That is how we should make a system call in linux. Reference of all system calls in linux: Regarding which $SYS_Call_NUM & which parameters we can use this reference : http://docs.cs.up.ac.za/programming/asm/derick_tut/syscalls.html OFFICIAL Reference : http://kernel.org/doc/man-pages/online/dir_section_2.html Calling convention in Windows: ??? Reference of all system calls in Windows: ??? Unofficial : http://www.metasploit.com/users/opcode/syscalls.html , but how do I use these in assembly unless I know the calling convention. OFFICIAL : ??? If you say, they didn't documented it. Then how is one going to write libc for windows without knowing system calls? How is one gonna do Windows Assembly programming? Atleast in the driver programming one needs to know these. right? Now, whats up with the so called Native API? Is Native API & System calls for windows both are different terms referring to same thing? In order to confirm I compared these from two UNOFFICIAL Sources System Calls: http://www.metasploit.com/users/opcode/syscalls.html Native API: http://undocumented.ntinternals.net/aindex.html My observations: All system calls are beginning with letters Nt where as Native API is consisting of lot of functions which are not beginning with letters Nt. System Call of windows are subset of Native API. System calls are just part of Native API. Can any one confirm this and explain.

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• How to set buffer size in client-server app using sockets?

  - by nelly

  First of all i am new to networking so i may say dumb thing in here. Considering a client-server application using sockets(.net with c# if that matters). The client sends some data, the server process it and sends back a string. The client sends some other data, the serve process it, queries the db and sends back several hundreds of items from the database The client sends some other type of data and the server notifies some other clients . My question is how to set the buffer size correctly for reading/writing operation. Should i do something like this: byte[] buff = new byte[client.ReceiveBufferSize] ? I am thinking of something like this: Client sends data to the server(and the server will follow the same pattern) byte[] bytesToSend=new byte[2048] //2048 to be standard for any command send by the client bytes 0..1 ->command type bytes 1..2047 ->command parameters byte[] bytesToReceive=new byte[8]/byte[64]/byte[8192] //switch(command type) But..what is happening when a client is notified by the server without sending data? What is the correct way to accomplish what i am trying to do? Thanks for reading.

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• Drupal 6 Validation for Form Callback Function

  - by Wade

  I have a simple form with a select menu on the node display page. Is there an easy way to validate the form in my callback function? By validation I don't mean anything advanced, just to check that the values actually existed in the form array. For example, without ajax, if my select menu has 3 items and I add a 4th item and try to submit the form, drupal will give an error saying something similar to "an illegal choice was made, please contact the admin." With ajax this 4th item you created would get saved into the database. So do I have to write validation like if ($select_item > 0 && $select_item <= 3) { //insert into db } Or is there an easier way that will check that the item actually existed in the form array? I'm hoping there is since without ajax, drupal will not submit the form if it was manipulated. Thanks. EDIT: So I basically need this in my callback function? $form_state = array('storage' => NULL, 'submitted' => FALSE); $form_build_id = $_POST['form_build_id']; $form = form_get_cache($form_build_id, $form_state); $args = $form['#parameters']; $form_id = array_shift($args); $form_state['post'] = $form['#post'] = $_POST; $form['#programmed'] = $form['#redirect'] = FALSE; drupal_process_form($form_id, $form, $form_state); To get $_POST['form_build_id'], I sent it as a data param, is that right? Where I use form_get_cache, looks like there is no data. Kind of lost now.

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