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  • C++ volatile required when spinning on boost::shared_ptr operator bool()?

    - by JaredC
    I have two threads referencing the same boost::shared_ptr: boost::shared_ptr<Widget> shared; On thread is spinning, waiting for the other thread to reset the boost::shared_ptr: while(shared) boost::thread::yield(); And at some point the other thread will call: shared.reset(); My question is whether or not I need to declare the shared pointer as volatile to prevent the compiler from optimizing the call to shared.operator bool() out of the loop and never detecting the change? I know that if I were simply looping on a variable, waiting for it to reach 0 I would need volatile, but I'm not sure if boost::shared_ptr is implemented in such a way that it is not necessary here.

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  • On saving a new record an associated id changes to 9 figure number

    - by Dave
    Hi, I have a table of venues, with each venue belonging to an area and a type. I recently dropped the table and added to it some addressline fields. I have re-migrated it but now the area_id field saves as a random? 9 figure number. Both the area_id and venuetype_id integers are created in the same way from the create new form and the venuetype_id saves as normal but not the area_id. Can anyone offer any help? whats shown in the console => [#<Venue id: 4, name: "sdf", addressline1: "", addressline2: "", addressline3 : "", addressline4: "", icontoppx: 234, iconleftpx: 234, area_id: 946717224, ven uetype_id: 8, created_at: "2011-03-17", updated_at: "2011-03-17 23:33:53">] irb(main):030:0> the area_id should be 8 in the above example. The area and venuetype id's are slected from dropdown boxes on the new venue form. new form <%= form_for @venue do |f| %> <p>name: <br> <%= f.text_field :name %></p> <p>top: <br> <%= f.text_field :icontoppx %></p> <p>left: <br> <%= f.text_field :iconleftpx %></p> <p>addressline1: <br> <%= f.text_field :addressline1 %></p> <p>addressline2: <br> <%= f.text_field :addressline2 %></p> <p>addressline3: <br> <%= f.text_field :addressline3 %></p> <p>addressline4: <br> <%= f.text_field :addressline4 %></p> <p>area: <br> <%= f.collection_select(:area_id, Area.all, :id, :name) %></p> <p>venuetype: <br> <%= f.collection_select(:venuetype_id, Venuetype.all, :id, :name) %></p> <br><br> <div class="button"><%= submit_tag %></div> <% end %> Areas table class CreateAreas < ActiveRecord::Migration def self.up create_table :areas do |t| t.string :name t.timestamps end end def self.down drop_table :areas end end Thanks very much for any help!

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  • Boost shared_ptr use_count function

    - by photo_tom
    My application problem is the following - I have a large structure foo. Because these are large and for memory management reasons, we do not wish to delete them when processing on the data is complete. We are storing them in std::vector<boost::shared_ptr<foo>>. My question is related to knowing when all processing is complete. First decision is that we do not want any of the other application code to mark a complete flag in the structure because there are multiple execution paths in the program and we cannot predict which one is the last. So in our implementation, once processing is complete, we delete all copies of boost::shared_ptr<foo>> except for the one in the vector. This will drop the reference counter in the shared_ptr to 1. Is it practical to use shared_ptr.use_count() to see if it is equal to 1 to know when all other parts of my app are done with the data. One additional reason I'm asking the question is that the boost documentation on the shared pointer shared_ptr recommends not using "use_count" for production code.

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  • What's the best way to return something like a collection of `std::auto_ptr`s in C++03?

    - by Billy ONeal
    std::auto_ptr is not allowed to be stored in an STL container, such as std::vector. However, occasionally there are cases where I need to return a collection of polymorphic objects, and therefore I can't return a vector of objects (due to the slicing problem). I can use std::tr1::shared_ptr and stick those in the vector, but then I have to pay a high price of maintaining separate reference counts, and object that owns the actual memory (the container) no longer logically "owns" the objects because they can be copied out of it without regard to ownership. C++0x offers a perfect solution to this problem in the form of std::vector<std::unique_ptr<t>>, but I don't have access to C++0x. Some other notes: I don't have access to C++0x, but I do have TR1 available. I would like to avoid use of Boost (though it is available if there is no other option) I am aware of boost::ptr_container containers (i.e. boost::ptr_vector), but I would like to avoid this because it breaks the debugger (innards are stored in void *s which means it's difficult to view the object actually stored inside the container in the debugger)

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  • loading record into detailview

    - by summer
    please please i need help..i think i am lost somewhere..basically i followed the example http://www.iphonesdkarticles.com/2008/10/sqlite-tutorial-loading-data-as.html, but i was stuck with error on reading description..something must had gone wrong some well but i am not very sure how should i solve it. this is my code, actually i dun really have an idea on wat's really going in this code..help please..2days!! no solution!! - (void) hydrateDetailViewData { //if detail view is hydrated then do not get it from database if(isDetailViewHydrated) return; if(detailStmt == nil) { const char *sql = "select snapTitle, snapDesc from Snap where snapID =?"; if(sqlite3_prepare_v2(database, sql, -1, &detailStmt, NULL) != SQLITE_OK) NSAssert1(0, @"Error while creating detail view statement. '%s'", sqlite3_errmsg(database)); NSLog(@"SQLite= %d", sqlite3_step(detailStmt)); } if(SQLITE_DONE != sqlite3_step(detailStmt)) { // NSString *descStr = [[NSString alloc] //initWithString:sqlite3_column_text(detailStmt, 2)]; NSString *descStr = [NSString stringWithUTF8String:(char *)sqlite3_column_text(detailStmt,2)]; self.snapDescription = descStr; [descStr release]; } else NSAssert1(0, @"Error getting description of snap2play. '%s'", sqlite3_errmsg(database)); sqlite3_reset(detailStmt); isDetailViewHydrated = YES; //if hydrated, make sure do not get from database again. } }

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  • How to know record has been updated successfully in php

    - by Lisa Ray
    $sql = "UPDATE...."; if(mysql_query($sql)) { $_SESSION['Trans']="COMMIT"; header("location:result.php"); exit; } else { $_SESSION['Trans']="FAIL"; $_SESSION['errors'] = "Error: Sorry! We are unable to update your Profile, Please contact to PNP HelpDesk."; header("location:result.php"); exit; }//end IF data is getting updated then why compiler is not coming inside IF condition.

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  • Insert Statment with Case for avoid duplicate record insertion

    - by rama
    I have written the below SP for Precheck for Duplicate records before insert into Table . but it is not allow me yo write insert staement inside the CASE . how can I write Stored Procedure for fist Check the value @Ordername into table After that if it is not present then it should inserted into Database . CREATE PROCEDURE [Test Procedure ] ( @section varchar(70), @mark varchar(70), @qty decimal(18,2), @Weight decimal(18,2), @dateupdateremark int, @OrderName varchar(70) ) AS BEGIN SET NOCOUNT ON; select case(@OrderName) when (select OrderName from dbo.tbl_insertxmldetails where(@OrderName) not in (select OrderName from tbl_insertxmldetails)) then insert into dbo.tbl_insertxmldetails (Section, Mark, QTY,Weight,Dateupdateremark ,OrderName,SystemDate) values (@Section, @Mark, @QTY,@Weight, @Dateupdateremark,@OrderName,GETDATE()) else 'File already Exists' end

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  • 'Good' programming form in maintaining / updating / accessing files by entry

    - by zhermes
    Basic Question: If I'm storying/modifying data, should I access elements of a file by index hard-coded index, i.e. targetFile.getElement(5); via a hardcoded identifier (internally translated into index), i.e. target.getElementWithID("Desired Element"), or with some intermediate DESIRED_ELEMENT = 5; ... target.getElement(DESIRED_ELEMENT), etc. Background: My program (c++) stores data in lots of different 'dataFile's. I also keep a list of all of the data-files in another file---a 'listFile'---which also stores some of each one's properties (see below, but i.e. what it's name is, how many lines of information it has etc.). There is an object which manages the data files and the list file, call it a 'fileKeeper'. The entries of a listFile look something like: filename , contents name , number of lines , some more numbers ... Its definitely possible that I may add / remove fields from this list --- but in general, they'll stay static. Right now, I have a constant string array which holds the identification of each element in each entry, something like: const string fileKeeper::idKeys[] = { "FileName" , "Contents" , "NumLines" ... }; const int fileKeeper::idKeysNum = 6; // 6 - for example I'm trying to manage this stuff in 'good' programatic form. Thus, when I want to retrieve the number of lines in a file (for example), instead of having a method which just retrieves the '3'rd element... Instead I do something like: string desiredID = "NumLines"; int desiredIndex = indexForID(desiredID); string desiredElement = elementForIndex(desiredIndex); where the function indexForID() goes through the entries of idKeys until it finds desiredID then returns the index it corresponds to. And elementForIndex(index) actually goes into the listFile to retrieve the index'th element of the comma-delimited string. Problem: This still seems pretty ugly / poor-form. Is there a way I should be doing this? If not, what are some general ways in which this is usually done? Thanks!

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  • Boost Shared Pointers and Memory Management

    - by Izza
    I began using boost rather recently and am impressed by the functionality and APIs provided. In using boost::shared_ptr, when I check the program with Valgrind, I found a considerable number of "Still reachable" memory leaks. As per the documentation of Valgrind, these are not a problem. However, since I used to use the standard C++ library only, I always made sure that any program written is completely free from memory leaks. My question is, are these memory leaks something to worry about? I tried using reset(), however it only decrements the reference count, doesn't deallocate memory. Can I safely ignore these, or any way to forcibly deallocate the memory allocated by boost::shared_ptr? Thank you.

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  • SqlAlchemy hangs after adding record in MS SQL

    - by Patrick
    I'm running SQLAlchemy on Jython and trying to connect to a MS SQL database using jTDS with windows authentication. I can query and delete just fine but when I try to insert new values it will hang when I commit. int 'before add' session.add(newVal) print 'after add' session.commit() print 'after commit' I see the first two print statements but not the last. My CPU maxes out and I can't even query the table directly using the MS SQL Management Studio. When I kill the Jython java process I can query again but the new values haven't been added. Strangely enough I can insert values directly using an SQL command: insert_sql = "INSERT INTO my_table (my_value) VALUES ('test_value')" session.execute(insert_sql) session.commit() Any ideas what I'm doing wrong?

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  • How do record updates behave internally?

    - by redxaxder
    data Thing = Thing {a :: Int, b :: Int, c :: Int, (...) , z :: Int} deriving Show foo = Thing 1 2 3 4 5 (...) 26 mkBar x = x { c = 30 } main = do print $ mkBar foo What is copied over when I mutate foo in this way? As opposed to mutating part of a structure directly. Data Thing = Thing {a :: IORef Int, b :: IORef Int, (...) , z :: IORef Int} instance Show Thing where (...something something unsafePerformIO...) mkFoo = do a <- newIORef 1 (...) z <- newIORef 26 return Thing a b (...) z mkBar x = writeIORef (c x) 30 main = do foo <- mkFoo mkBar foo print foo Does compiling with optimizations change this behavior?

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  • Saving a Record with Rails Association

    - by tshauck
    Hi, I've been going through the Rails Guides, but have gotten stuck on associations after going through validations and migrations. So, I have the following models Job and Person, where a Person can have many jobs. I know that in reality there'd be a many-to-many, but I'm trying to get my handle on this first. class Job < ActiveRecord::Base belongs_to :people end and class Person < ActiveRecord::Base has_many :jobs end Here's the schema ActiveRecord::Schema.define(:version => 20110108185924) do create_table "jobs", :force => true do |t| t.string "occupation" t.boolean "like" t.datetime "created_at" t.datetime "updated_at" t.integer "person_id" end create_table "people", :force => true do |t| t.string "first_name" t.string "last_name" t.datetime "created_at" t.datetime "updated_at" end end Is there some I can do the following j = Job.first; j.Person? Then that'd give me access to the Person object associated with the j. I couldn't find it on guides.rubyonrails.org, although it has been very helpful getting a grip on migrations and validations thus far. Thanks PS, If there are any tutorials that covers more of this kind of things links would be great.

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  • SQL Server 2008 - Get Latest Record from Joined Table

    - by user336786
    Hello, I have a SQL Server 2008 database. This database has two tables called Customer and Order. These tables are defined as follows: Customer -------- ID, First Name, Last Name Order ----- ID, CustomerID, Date, Description I am trying to write a query that returns all of the customers in my database. If the user has placed at least one order, I want to return the information associated with the most recent order placed. Currently, I have the following: SELECT * FROM Customer c LEFT OUTER JOIN Order o ON c.[ID]=o.[CustomerID] As you can imagine, this will return all of the orders associated with a customer. In reality though, I only want the most recent one. How do I do this in SQL? Thank you!

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  • Entityframework duplicate record on second insert

    - by Delysid
    I am building an application for recipe/meal planning, and i have come across a problem i cant seem to figure out. i have a table for units of measure, where i keep the used units in, i only want unique units in here (for grocery list calculation and so forth) but if i use a unit from the table on a recipe, the first time it is okay, nothing is inserted in units of measure, but the second time i get a "duplicate". i suspect it has something to do with entitykey, because the primary key is identity column on the sql server (2008 r2) for some reason it works to change the objectstate on some objects (courses, see code) and that does not generate a duplicate, but that does not work on the unit of measure my insert methods looks like this : public recipe Create(recipe recipe) { using (RecipeDataContext ctx = new RecipeDataContext()) { foreach (recipe_ingredient rec_ing in recipe.recipe_ingredient) { if (rec_ing.ingredient.ingredient_id == 0) { ingredient ing = (from _ing in ctx.ingredients where _ing.name == rec_ing.ingredient.name select _ing).FirstOrDefault(); if (ing != null) { rec_ing.ingredient_id = ing.ingredient_id; rec_ing.ingredient = null; } } if (rec_ing.unit_of_measure.unit_of_measure_id == 0) { unit_of_measure _uom = (from dbUom in ctx.unit_of_measure where dbUom.unit == rec_ing.unit_of_measure.unit select dbUom).FirstOrDefault(); if (_uom != null) { rec_ing.unit_of_measure_id = _uom.unit_of_measure_id; rec_ing.unit_of_measure = null; } } ctx.Recipes.AddObject(recipe); //for some reason it works to change object state of this, and not generate a duplicate ctx.ObjectStateManager.ChangeObjectState(recipe.courses[0], EntityState.Unchanged); } ctx.SaveChanges(); } return recipe; } My datamodel looks like this : http://i.imgur.com/NMwZv.png

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  • why is Active Record firing extra query when I use Includes method to fetch data

    - by riddhi_agrawal
    I have the following model structure: class Group < ActiveRecord::Base has_many :group_products, :dependent => :destroy has_many :products, :through => :group_products end class Product < ActiveRecord::Base has_many :group_products, :dependent => :destroy has_many :groups, :through => :group_products end class GroupProduct < ActiveRecord::Base belongs_to :group belongs_to :product end I wanted to minimize my database queries so I decided to use includes.In the console I tried something like, groups = Group.includes(:products) my development logs show the following calls, Group Load (403.0ms) SELECT `groups`.* FROM `groups` GroupProduct Load (60.0ms) SELECT `group_products`.* FROM `group_products` WHERE (`group_products`.group_id IN (1,3,14,15,16,18,19,20,21,22,23,24,25,26,27,28,29,30,33,42,49,51)) Product Load (22.0ms) SELECT `products`.* FROM `products` WHERE (`products`.`id` IN (382,304,353,12,63,103,104,105,262,377,263,264,265,283,284,285,286,287,302,306,307,308,328,335,336,337,340,355,59,60,61,247,309,311,66,30,274,294,324,350,140,176,177,178,64,240,327,332,338,380,383,252,254,255,256,257,325,326)) Product Load (10.0ms) SELECT `products`.* FROM `products` WHERE (`products`.`id` = 377) LIMIT 1 I could analyze the initial three calls were necessary but don't get the reason why the last database call is made, Product Load (10.0ms) SELECT `products`.* FROM `products` WHERE (`products`.`id` = 377) LIMIT 1 Any idea why this is happening? Thanks in advance. :)

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  • enable_shared_from_this and inheritance

    - by DeadMG
    I've got a type which inherits from enable_shared_from_this<type>, and another type that inherits from this type. Now I can't use the shared_from_this method because it returns the base type and in a specific derived class method I need the derived type. Is it valid to just construct a shared_ptr from this directly? Edit: In a related question, how can I move from an rvalue of type shared_ptr<base> to a type of shared_ptr<derived>? I used dynamic_cast to verify that it really was the correct type, but now I can't seem to accomplish the actual move.

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  • DataSet.GetChanges - Save the updated record in a different table than the source one

    - by John Dev
    I'm doing operation on a dataset containing data from a sql table named Test_1 and then get the updated records using the DataSet.GetChanges(DataRowState.Modified) function. Then i try to save the dataset containing the updated records on a different table than the source one (the table is names Test and has the same structure as Test_1) using the following statement: sqlDataAdapter.Update(changesDataSet,"Test"); I'm getting the following error : Update unable to find TableMapping['Test'] or DataTable 'Test' I'm new to ado.net and don't even know if it"s something possible. Any advice is welcome. Just to provide a bit of context. ETL jobs are importing data in temp table with same structure as the original but with _jobid suffix. Right after a rule engine is doing validation before updating the original table.

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  • rails active record - Advanced find

    - by par
    I have the following model setup - a User is interested in projects in many project Categories. Each Project has many categories. Like so: class User has_many :projects has_and_belongs_to_many :project_categories class Project belongs_to :user has_and_belongs_to_many :project_categories class ProjectCategory has_and_belongs_to_many :projects has_and_belongs_to_many :users Now, I'd like to do a find for projects with any of the catogories that a certain user are interested in, i.e. if a user is interested in project categories A,B,C then I'd like to find projects which are part of one or more of those project categories. Anyone?

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  • dealing with a large flat data files with a very big record length

    - by gsp
    I have a large data file that is creatd from a shell script. Next script processes it by sorting and reading several times, that takes more than 14 hours, it is not viable. I want to replace this long running script with a program, probably in JAVA, C, or COBOl, that can run on windows or on sun solaris. I have to read a group of records everytime, sort and process and write to the output sort file and at the same time insert into db2/sql tables.

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  • This query show me with this active record

    - by New Kid
    I am having trouble getting two tables and passing them to controller: IN A MODEL: function get_all_entries() { $query = $this->db->get('entry'); return $query->result(); $this->db->select('entry_id , count(comment_id) as total_comment'); $this->db->group_by('entry_id'); $comment = $this->db->get('comment'); return $comment->result(); } IN A CONTROLLER: $data['query'] = $this->blog_model->get_all_entries(); $this->load->view('blog/index',$data); How do I return $query and $comment variables to controller? I think I am doing it wrong.

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  • Concatenate multi value into one record.

    - by mikehjun
    I joined two tables together and what I like to do is concatenate multi vaule in one records without duplicated value. TAXLOT_ZONE TID ZONE 1 A 1 A 1 B 1 C 2 D 2 D 2 E 3 A 3 B 4 C 5 D Desirable Final table looks like; TID ZONE 1 A, B, C 2 D, E 3 A, B 4 C 5 D

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