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  • Vacancy Tracking Algorithm implementation in C++

    - by Dave
    I'm trying to use the vacancy tracking algorithm to perform transposition of multidimensional arrays in C++. The arrays come as void pointers so I'm using address manipulation to perform the copies. Basically, there is an algorithm that starts with an offset and works its way through the whole 1-d representation of the array like swiss cheese, knocking out other offsets until it gets back to the original one. Then, you have to start at the next, untouched offset and do it again. You repeat until all offsets have been touched. Right now, I'm using a std::set to just fill up all possible offsets (0 up to the multiplicative fold of the dimensions of the array). Then, as I go through the algorithm, I erase from the set. I figure this would be fastest because I need to randomly access offsets in the tree/set and delete them. Then I need to quickly find the next untouched/undeleted offset. First of all, filling up the set is very slow and it seems like there must be a better way. It's individually calling new[] for every insert. So if I have 5 million offsets, there's 5 million news, plus re-balancing the tree constantly which as you know is not fast for a pre-sorted list. Second, deleting is slow as well. Third, assuming 4-byte data types like int and float, I'm using up actually the same amount of memory as the array itself to store this list of untouched offsets. Fourth, determining if there are any untouched offsets and getting one of them is fast -- a good thing. Does anyone have suggestions for any of these issues?

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  • NHibernate: Using value tables for optimization AND dynamic join

    - by Kostya
    Hi all, My situation is next: there are to entities with many-to-many relation, f.e. Products and Categories. Also, categories has hierachial structure, like a tree. There is need to select all products that depends to some concrete category with all its childs (branch). So, I use following sql statement to do that: SELECT * FROM Products p WHERE p.ID IN ( SELECT DISTINCT pc.ProductID FROM ProductsCategories pc INNER JOIN Categories c ON c.ID = pc.CategoryID WHERE c.TLeft >= 1 AND c.TRight <= 33378 ) But with big set of data this query executes very long and I found some solution to optimize it, look at here: DECLARE @CatProducts TABLE ( ProductID int NOT NULL ) INSERT INTO @CatProducts SELECT DISTINCT pc.ProductID FROM ProductsCategories pc INNER JOIN Categories c ON c.ID = pc.CategoryID WHERE c.TLeft >= 1 AND c.TRight <= 33378 SELECT * FROM Products p INNER JOIN @CatProducts cp ON cp.ProductID = p.ID This query executes very fast but I don't know how to do that with NHIbernate. Note, that I need use only ICriteria because of dynamic filtering\ordering. If some one knows a solution for that, it will be fantastic. But I'll pleasure to any suggestions of course. Thank you ahead, Kostya

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  • Help needed for writing a Set Based query for finding the highest marks obtained by the students

    - by priyanka.sarkar_2
    I have the below table declare @t table (id int identity, name varchar(50),sub1 int,sub2 int,sub3 int,sub4 int) insert into @t select 'name1',20,30,40,50 union all select 'name2',10,30,40,50 union all select 'name3',40,60,100,50 union all select 'name4',80,30,40,80 union all select 'name5',80,70,40,50 union all select 'name6',10,30,40,80 The desired output should be Id Name Sub1 Sub2 Sub3 Sub4 3 Name3 100 4 Name4 80 80 5 Name5 80 70 6 Name6 80 What I have done so far is ;with cteSub1 as ( select rn1 = dense_rank() over(order by sub1 desc),t.id,t.name,t.sub1 from @t t ) ,cteSub2 as ( select rn2 = dense_rank() over(order by sub2 desc),t.id,t.name,t.sub2 from @t t ) ,cteSub3 as ( select rn3 = dense_rank() over(order by sub3 desc),t.id,t.name,t.sub3 from @t t ) ,cteSub4 as ( select rn4 = dense_rank() over(order by sub4 desc),t.id,t.name,t.sub4 from @t t ) select x1.id,x2.id,x3.id,x4.id ,x1.sub1,x2.sub2,x3.sub3,x4.sub4 from (select c1.id,c1.sub1 from cteSub1 c1 where rn1 =1) as x1 full join (select c2.id,c2.sub2 from cteSub2 c2 where rn2 =1)x2 on x1.id = x2.id full join (select c3.id,c3.sub3 from cteSub3 c3 where rn3 =1)x3 on x1.id = x3.id full join (select c4.id,c4.sub4 from cteSub4 c4 where rn4 =1)x4 on x1.id = x4.id which is giving me the output as id id id id sub1 sub2 sub3 sub4 5 5 NULL NULL 80 70 NULL NULL 4 NULL NULL 4 80 NULL NULL 80 NULL NULL 3 NULL NULL NULL 100 NULL NULL NULL NULL 6 NULL NULL NULL 80 Help needed. Also how can I reduce the number of CTE's?

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  • Merging rows with uniqueness constraints

    - by Flambino
    I've got a little time-tracking web app (implemented in Rails 3.2.8 & MySQL). The app has several users who add their time to specific tasks, on a given date. The system is set up so a user can only have 1 time entry (i.e. row) per task per date. I.e. if you add time twice on the same task and date, it'll add time to the existing row, rather than create a new one. Now I'm looking to merge 2 tasks. In the simplest terms, merging task ID 2 into task ID 1 would take this time | user_id | task_id | date ------+----------+----------+----------- 10 | 1 | 1 | 2012-10-29 15 | 2 | 1 | 2012-10-29 10 | 1 | 2 | 2012-10-29 5 | 3 | 2 | 2012-10-29 and change it into this time | user_id | task_id | date ------+----------+----------+----------- 20 | 1 | 1 | 2012-10-29 <-- time values merged (summed) 15 | 2 | 1 | 2012-10-29 <-- no change 5 | 3 | 1 | 2012-10-29 <-- task_id changed (no merging necessary) I.e. merge by summing the time values, where the given user_id/date/task combo would conflict. I figure I can use a unique constraint to do a ON DUPLICATE KEY UPDATE ... if I do an insert for every task_id=2 entry. But that seems pretty inelegant. I've also tried to figure a way to first update all the rows in task 1 with the summed-up times, but I can't quite figure that one out. Any ideas?

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  • How to store and synchronize a big list of strings

    - by Joel
    I have a large database table in SQLExpress on Windows, with a particular field of interest 'code'. I have an Apache web server with MySQL on Linux. The web application on the Linux box needs access to the list of all codes. The only thing it will use the list for is checking for the existence of a given code. Having the Linux server call out to the Windows server is impractical as the Windows server is behind a NAT'ed office internet connection, and it may not always be accessible. I have set it so the Windows server will push the list of codes to the web server by means of a simple HTTP POST request. However, at this point I have not implemented the storage of the codes on the Linux box. Should I store them in a MySQL table with a single field 'code'? Then I get fast indexed lookups O(1), however I think synchronization will be an issue - given an updated list of codes, pushed from the Windows box, how would I optimally synchronize the list with the database? TRUNCATE, followed by INSERT? Should I instead store them in a flat file? Then I have O(n) look up time rather than O(1). Additionally an extra constant-time overhead too, as I will be processing the file in Ruby. However, synchronization is easy - simply replace the file.

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  • Add Custom Control to DataGridViewCell

    - by Kovscer
    Hello, I create a custom control inherited from Windows.System.Forms.Controls. This is my code of this control: public partial class MonthEventComponent : Control { private Color couleur; private Label labelEvenement; public MonthEventComponent(Color couleur_c, String labelEvenement_c ) { InitializeComponent(); this.couleur = couleur_c; this.labelEvenement.Text = labelEvenement_c; this.labelEvenement.ForeColor = couleur; this.labelEvenement.BackColor = Color.White; this.labelEvenement.TextAlign = ContentAlignment.MiddleLeft; this.labelEvenement.Dock = DockStyle.Fill; this.Controls.Add(labelEvenement); } public MonthEventComponent() { InitializeComponent(); this.couleur = Color.Black; this.labelEvenement = new Label(); this.labelEvenement.ForeColor = couleur; this.labelEvenement.BackColor = Color.White; this.labelEvenement.Text = "Evénement Initialiser"; this.labelEvenement.TextAlign = ContentAlignment.MiddleLeft; this.labelEvenement.Dock = DockStyle.Fill; this.Controls.Add(labelEvenement); } protected override void OnClick(EventArgs e) { base.OnClick(e); MessageBox.Show("Click"); } } I would like to insert this control or multiple of this control on a DataGridViewCell but i don't know how to do this. Thank you in advance for your answer, Best Regards, PS: I'm french, i'm apologize for any can of language errors.

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  • Which approach is better in term of saving the data? How to handle this?

    - by dewacorp.alliances
    Hi there I have Telerik grid within a Telerik grid. Due to I have a different view between insert and edit mode, so as per suggested I have to use UserControl instead. Inside this control, it could have another Telerik grid plus bunch of ASP.NET textboxes. This thing works well. My dilemma is this: Scenario 1: Handling the save in the user control - OnClick event I have a button to save this. I need to get the value of the "selected grid" so I am using this snippet below and again works well. foreach (GridDataItem dataItem in radgrdTariffNetworkDistributorRateItems.SelectedItems) { string ID = dataItem.OwnerTableView.DataKeyValues[dataItem.ItemIndex]["SupplierRateItemID"].ToString(); } But then how do I get the id of the parent grid where this control sit? I use the following this event to save: protected void bttnNetworkTariffReviewItemInsert_Click(object sender, EventArgs e) the e of course not the right one though?!?!? GridDataItem parentItem = (GridDataItem)e.Item.OwnerTableView.ParentItem; string reviewID = parentItem.OwnerTableView.DataKeyValues[parentItem.ItemIndex]["ID"].ToString(); Scenario 2: Handling the save in the page instead (OnInsertCommand on the master grid) With this approach works well to get id of the grid etc BUT I am having a problem to get selected grid in the UserControl and plus couple controls value. How do I make this feasible? Logically, I should handle this at the user control level to save but again because the user control relying on the child grid I am having trouble to get this value. I am appreciated your suggestion.

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  • How to store arbitrary data for some HTML tags

    - by nickf
    I'm making a page which has some interaction provided by javascript. Just as an example: links which send an AJAX request to get the content of articles and then display that data in a div. Obviously in this example, I need each link to store an extra bit of information: the id of the article. The way I've been handling it in case was to put that information in the href link this: <a class="article" href="#5"> I then use jQuery to find the a.article elements and attach the appropriate event handler. (don't get too hung up on the usability or semantics here, it's just an example) Anyway, this method works, but it smells a bit, and isn't extensible at all (what happens if the click function has more than one parameter? what if some of those parameters are optional?) The immediately obvious answer was to use attributes on the element. I mean, that's what they're for, right? (Kind of). <a articleid="5" href="link/for/non-js-users.html"> In my recent question I asked if this method was valid, and it turns out that short of defining my own DTD (I don't), then no, it's not valid or reliable. A common response was to put the data into the class attribute (though that might have been because of my poorly-chosen example), but to me, this smells even more. Yes it's technically valid, but it's not a great solution. Another method I'd used in the past was to actually generate some JS and insert it into the page in a <script> tag, creating a struct which would associate with the object. var myData = { link0 : { articleId : 5, target : '#showMessage' // etc... }, link1 : { articleId : 13 } }; <a href="..." id="link0"> But this can be a real pain in butt to maintain and is generally just very messy. So, to get to the question, how do you store arbitrary pieces of information for HTML tags?

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  • When to use () with classes?

    - by SoulBeaver
    This is really starting to confuse the hell out of me. When do I use them, when don't I? For example I was reading a .cpp on linked lists whose class declaration was: struct CarPart { long PartNumber; char Partname[40]; double UnitPrice; CarPart *next; }; class ListOfParts { int size; public: CarPart *head; ListOfParts(); ~ListOfParts(); const int count() const; void insert( CarPart *item ); CarPart *retrieve( int pos ); }; With this code, why am I allowed to write ListOfParts *pPart = new ListOfParts(); CarPart *pCarPart = new CarPart; Declaring an instance of ListOfParts requires (), but not my CarPart? That's confusing me. When I asked a question before and people told me that such a declaration is a function that returns a ListOfParts object, but not the actual constructor. So I'm guessing this is still something different. What's happening here? PS: Am I correct to assume that the const to the right of count() means I cannot modify any values in count?

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  • Retrieving the first picture with a HTML parser

    - by justin01
    Hey guys, (Not a native english speaker) I'm doing a personal project in PHP in which I use the Simple HTML Parser to parse the HTML of a given URL and retrieve the first image in a DIV that have a specific ID or class (maincontent, content, main, wrapper, etc. - it's all in an array) and ignore ads. The goal is to take this image and make a thumbnail with it, pretty much like on Digg and others. I thought everything was working fine until I tried my script with the website Snopes ("http://www.snopes.com/photos/animals/luckycoyote.asp" <- this page more exactly). The source of the first image it gets is: " graphics/luckycoyote1.jpg ". So far, to correct this problem I created a little function that gets the domain name of the given URL and insert it before the IMG's source attribute. So for sites like Snopes.com, it gives me: "http://www.snopes.com/graphics/luckycoyote1.jpg" ... while the real URL for this image is "http://www.snopes.com*/photos/animals/graphics/luckycoyote1.jpg*" (or, more precisely: " http://graphics1.snopes.com/photos/animals/graphics/luckycoyote1.jpg " - note the subdomain here). So my main question is: how can I externally/dynamically retrieve the full URL address of an image ("absolute path") when I am only given the "relative path"? I'm pretty sure this is possible, since when I paste the link in Facebook's "What are you doing?" field for example, it gives me the correct path to the image while on the website, the source of the image is only (example) "image/photo/example.jpg". Thank you for your time.

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  • Save many-to-one relationship from JSON into Core Data

    - by Snow Crash
    I'm wanting to save a Many-to-one relationship parsed from JSON into Core Data. The code that parses the JSON and does the insert into Core Data looks like this: for (NSDictionary *thisRecipe in recipes) { Recipe *recipe = [NSEntityDescription insertNewObjectForEntityForName:@"Recipe" inManagedObjectContext:insertionContext]; recipe.title = [thisRecipe objectForKey:@"Title"]; NSDictionary *ingredientsForRecipe = [thisRecipe objectForKey:@"Ingredients"]; NSArray *ingredientsArray = [ingredientsForRecipe objectForKey:@"Results"]; for (NSDictionary *thisIngredient in ingredientsArray) { Ingredient *ingredient = [NSEntityDescription insertNewObjectForEntityForName:@"Ingredient" inManagedObjectContext:insertionContext]; ingredient.name = [thisIngredient objectForKey:@"Name"]; } } NSSet *ingredientsSet = [NSSet ingredientsArray]; [recipe setIngredients:ingredientsSet]; Notes: "setIngredients" is a Core Data generated accessor method. There is a many-to-one relationship between Ingredients and Recipe However, when I run this I get the following error: NSCFDictionary managedObjectContext]: unrecognized selector sent to instance If I remove the last line (i.e. [recipe setIngredients:ingredientsSet];) then, taking a peek at the SQLite database, I see the Recipe and Ingredients have been stored but no relationship has been created between Recipe and Ingredients Any suggestions as to how to ensure the relationship is stored correctly?

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  • MySQLi Wrapper -- will this slow down performance?

    - by Kerry
    I found the following code on php.net. I'm trying to write a wrapper for the MySQLi library to make things incredibly simple. If this is going to slow down performance, I'll skip it and find another way, if this works, then I'll do that. I have a single query function, if someone passes in more than one variable, I assume the function has to be prepared. The function that I would use to pass in an array to mysqli_stmt_bind_param is call_user_func_array, I have a feeling that is going to slow things down. Am I right? <?php /* just explaining how to call mysqli_stmt_bind_param with a parameter array */ $sql_link = mysqli_connect('localhost', 'my_user', 'my_password', 'world'); $type = "isssi"; $param = array("5", "File Description", "File Title", "Original Name", time()); $sql = "INSERT INTO file_detail (file_id, file_description, file_title, file_original_name, file_upload_date) VALUES (?, ?, ?, ?, ?)"; $sql_stmt = mysqli_prepare ($sql_link, $sql); call_user_func_array('mysqli_stmt_bind_param', array_merge (array($sql_stmt, $type), $param); mysqli_stmt_execute($sql_stmt); ?>

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  • How to pass values from array into mysql with php

    - by moustafa
    my original code is this <tr> <th> <label for="user_level"> User Level: * <?php echo isset($valid_user_level) ? $valid_user_level : NULL; ?> </label> </th> </tr> <td> <select name="user_level" id="user_level" class="sel"> <option value="">Select one…</option> <option value="1">User</option> <option value="5">Admin</option> </select> </td> this give me the option to select one of choice from the drop down menu i.e. user and when user is selected and the submit button is pressed this will insert the value 1 into the database which will when the user logs in tell the system that they are are normal user. I want to change the code to the following <tr> <td> <select name="user_level" id="user_level" class="sel"> <option value="">Select one…</option> <?php if(!empty($level)) { foreach($level as $value) { echo "<option value='{$value}'"; echo getSticky(2,'user_level',$value); echo ">{$value}</option>"; } } ?> </select> </td> </tr> With this being my array query $level = array('User','Admin'); How can I pass the values of 1 for user level and 5 for admin in this code so when the user is selected it inouts 1 into the database?

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  • Another way to handle a common JQuery event handling pattern

    - by bradgonesurfing
    I have the following code for example $("a.foo").bind(function (e){ var t; if ( $(e.target).is("a") ){ t = $(e.target); }else{ t = $(e.target).parent("a"); } var data = t.attr("data-info"); }); In english. I might have a list of anchors within which there may be a number of spans. Each anchor is declared as <a class="foo" href="#" data-info="1"> <span> ... </span> <span> ... </span> </a> <a class="foo" href="#" data-info="2"> <span> ... </span> <span> ... </span> </a> ... ... I bind a handler to the click event of the anchor but the event object comes back with the anchor OR one of the spans depending on where I click. So to get my html5 "data-info" value into the callback I have to insert a bit of messy code. This is now appearing throughout my code to the point where I am guessing there might be an idiomatic JQuery way of handling this.

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  • Is there a way to sync (two way) tables betwen a mysql server and a local MS Access?

    - by Kailen
    Help me figure out a solution to a (not so unique) problem. My research group has gps devices attached to migratory animals. Every once in a while, a research tech will be within range of an animal and will get the chance to download all the logged points. Each individual spits out a single dbf and new locations are just appended to the end (so the file is just cumulative). These data need to be shared among a research group. Everyone else (besides me) wants to use access, so they can make small edits and prefer that interface. They do not like using MySQL. The solution I came up with is: a) The person who downloads the file goes to a web page, enters animal ID into a form, chooses .dbf file and uploads to a mysql database on the server (I still have to write php code to read the dbf and write sql insert statements from it). b) Everyone syncs from their local access database to the server. (This is natively possible from access but very clunky). Is there a tool (preferably open source), that can compare a access table to mysql table and sync the two (both ways)? Alternatively, does anyone have a more elegant solution? The ultimate goal is to allow everyone to have access to the most current data on their computers using their preferred database app.

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  • Rails from with better url

    - by Sam
    wow, switching to rest is a different paradigm for sure and is mainly a headache right now. view <% form_tag (businesses_path, :method => "get") do %> <%= select_tag :business_category_id, options_for_select(@business_categories.collect {|bc| [bc.name, bc.id ]}.insert(0, ["All Containers", 0]), which_business_category(@business_category) ), { :onchange => "this.form.submit();"} %> <% end %> controller def index @business_categories = BusinessCategory.find(:all) if params[:business_category_id].to_i != 0 @business_category = BusinessCategory.find(params[:business_category_id]) @businesses = @business_category.businesses else @businesses = Business.all end respond_to do |format| format.html # index.html.erb format.xml { render :xml => @businesses } end end routes map.resources What I want to to is get a better url than what this form is presenting which is the following: http://localhost:3000/businesses?business_category_id=1 Without rest I would have do something like http://localhost:3000/business/view/bbq bbq as permalink or I would have done http://localhost:300/business_categories/view/bbq and get the business that are associated with the category but I don't really know the best way of doing this. So the two questions are what is the best logic of finding a business by its categories using the latter form and number two how to get that in a pretty url all through restful routes in rails.

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  • How to implement a Linked List in Java?

    - by nbarraille
    Hello! I am trying to implement a simple HashTable in Java that uses a Linked List for collision resolution, which is pretty easy to do in C, but I don't know how to do it in Java, as you can't use pointers... First, I know that those structures are already implemented in Java, I'm not planning on using it, just training here... So I created an element, which is a string and a pointer to the next Element: public class Element{ private String s; private Element next; public Element(String s){ this.s = s; this.next = null; } public void setNext(Element e){ this.next = e; } public String getString(){ return this.s; } public Element getNext(){ return this.next; } @Override public String toString() { return "[" + s + "] => "; } } Of course, my HashTable has an array of Element to stock the data: public class CustomHashTable { private Element[] data; Here is my problem: For example I want to implement a method that adds an element AT THE END of the linked List (I know it would have been simpler and more efficient to insert the element at the beginning of the list, but again, this is only for training purposes). How do I do that without pointer? Here is my code (which could work if e was a pointer...): public void add(String s){ int index = hash(s) % data.length; System.out.println("Adding at index: " + index); Element e = this.data[index]; while(e != null){ e = e.getNext(); } e = new Element(s); } Thanks!

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  • Storing large json strings to database + hash

    - by Guy
    I need to store quiete large JSON data strings to the database. I am using gzip to compress the string and therefore BLOB MySQL data type to store it. However, only 5% of all the requests contain unique data and only unique data ought to be stored to the database. My approach is as follows. array_multisort data (array [a, b, c] is virtually the same as [a, c, b]). json_encode data (json_encode is faster than serialize; we need string array representation for the step 3). sha1 data (slower than md5, though less possible the collisions). Check if the hash exists in the database. 5.1 yes – do not insert the data. 5.2. no – gzip the data and store it along the hash. Is there anything about this (apart from storing JSON data to the database in the first place) that sounds fishy or should be done a different way? p.s. We are talking about a database with roughly 1kk unique records being created every month.

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  • Time.new does not work as I would expect

    - by Marius Pop
    I am trying to generate some seed material. seed_array.each do |seed| Task.create(date: Date.new(2012,06,seed[1]), start_t: Time.new(2012,6,2,seed[2],seed[3]), end_t: Time.new(2012,6,2,seed[2] + 2,seed[3]), title: "#{seed[0]}") end Ultimately I will put random hours, minutes, seconds. The problem that I am facing is that instead of creating a time with the 2012-06-02 date it creates a time with a different date: 2000-01-01. I tested Time.new(2012,6,2,2,20,45) in rails console and it works as expected. When I am trying to seed my database however some voodo magic happens and I don't get the date I want. Any inputs are appreciated. Thank you! Update1: * [1m[36m (0.0ms)[0m [1mbegin transaction[0m [1m[35mSQL (0.5ms)[0m INSERT INTO "tasks" ("created_at", "date", "description", "end_t", "group_id", "start_t", "title", "updated_at") VALUES (?, ?, ?, ?, ?, ?, ?, ?) [["created_at", Tue, 03 Jul 2012 02:15:34 UTC +00:00], ["date", Thu, 07 Jun 2012], ["description", nil], ["end_t", 2012-06-02 10:02:00 -0400], ["group_id", nil], ["start_t", 2012-06-02 08:02:00 -0400], ["title", "99"], ["updated_at", Tue, 03 Jul 2012 02:15:34 UTC +00:00]] [1m[36m (2.3ms)[0m [1mcommit transaction * This is a small sample of the log. Update 2 Task id: 101, date: "2012-06-26", start_t: "2000-01-01 08:45:00", end_t: "2000-01-01 10:45:00", title: "1", description: nil, group_id: nil, created_at: "2012-07-03 02:15:33", updated_at: "2012-07-03 02:15:33" This is what shows up in rails console.

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  • A self-creator: What pattern is this? php

    - by user151841
    I have several classes that are basically interfaces to database rows. Since the class assumes that a row already exists ( __construct expects a field value ), there is a public static function that allows creation of the row and returns an instance of the class. Here's a pseudo-code example : class fruit { public $id; public function __construct( $id ) { $this->id = $id; $sql = "SELECT * FROM Fruits WHERE id = $id"; ... $this->arrFieldValues[$field] = $row[$value]; } public function __get( $var ) { return $this->arrFieldValues[$var]; } public function __set( $var, $val ) { $sql = "UPDATE fruits SET $var = $val WHERE id = $this->id"; } public static function create( $id ) { $sql = "INSERT INTO Fruits ( fruit_name ) VALUE ( '$fruit' )"; $id = mysql_insert_id(); $fruit = & new fruit($id); return $fruit; } } $obj1 = fruit::create( "apple" ); $obj2 = & new fruit( 12 ); What is this pattern called? Edit: I changed the example to one that has more database-interface functionality. For most of the time, this kind of class would be instantiated normally, through __construct(). But sometimes when you need to create a new row first, you would call create().

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  • Not getting concept of null

    - by appu
    Hy Guys, Beginning with mysql. I am not able to grasp the concept of NULL. Check screen-shot (*declare_not_null, link*). In it when I specifically declared 'name' field to be NOT NULL. When i run the 'desc test' table command, the table description shows default value for name field to be NULL.Why is that so? From what I have read about NULL, it connotes a missing or information that is not applicable. So when I declare a field to be NOT NULL it implies (as per my understanding) that user must enter a value for the name field else the DB engine should generate an error i.e. record will not be entered in DB. However when i run 'insert into test value();' the DB engine enters the record in table. Check screen-shot(*empty_value, link*). FLICKR LINKS *declare_not_null* http://www.flickr.com/photos/55097319@N03/5302758813/ *empty_values* Check the second screenshot on flickr Q.2 what would be sql statemetn to drop a primary key from a table's field. If I use 'ALTER TABLE test drop key id;' it gives the following: ERROR: Incorrect table definition; there can be only one auto column and it must be defined as a key. Thanks for your help..

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  • Why do I get 'Connection refused - connect(2)' for some models?

    - by Will
    I have a rails application running for the past 90 days that suddenly stopped working. Debugging the problem I found that I can read from the DB but not write to it. At least for certain models. There is one model that I can save whereas all others return Connection refused - connect(2) when I attempt to save them. They all used to work fine last month. I have no idea how to determine what the problem may be. Unfortunately I do not have access to the actual server remotely right now so I am limited in my debugging ability. I was able to get some non-tech people to run simple commands though that may help identify my problem. I will also be getting access tomorrow at some point. 1 Check from the console ./script/console >> a = Post.last.clone => #<Post id: nil, title: "test"... >> a.ex_id = 7 >> a.save Connection refused - connect(2) ... ... >> b = Story.last.console => #<Story id: nil, title: "test"... >> a.ex_id = 7 >> a.save => true I am not sure why this works for story and not post. This is consistent over many tests. 2 Check from mysql ./script/dbconsole -p mysql> INSERT INTO Posts (`title`,`body`, `ex_id`) SELECT `title`, `body`, 7 FROM Posts WHERE ID = 1; Query OK, 1 row affected (0.01 sec) Records: 1 Duplicates: 0 Warnings: 0 And as you can see I am able to write to the table with the same credientials that Rails uses? Does anyone know why I get connection refused in the console?

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  • find a duplicate series in SQL

    - by SomeMiscGuy
    I have a table with 3 columns containing a variable number of records based off of the first column which is a foreign key. I am trying to determine if I can detect when there is a duplicate across multiple rows for an entire series declare @finddupseries table ( portid int, asset_id int, allocation float ) ; INSERT INTO @finddupseries SELECT 250, 6, 0.05 UNION ALL SELECT 250, 66, 0.8 UNION ALL SELECT 250, 2, 0.105 UNION ALL SELECT 250, 4, 0.0225 UNION ALL SELECT 250, 5, 0.0225 UNION ALL SELECT 251, 13, 0.6 UNION ALL SELECT 251, 2, 0.3 UNION ALL SELECT 251, 5, 0.1 UNION ALL SELECT 252, 13, 0.8 UNION ALL SELECT 252, 2, 0.15 UNION ALL SELECT 252, 5, 0.05 UNION ALL SELECT 253, 13, 0.4 UNION ALL SELECT 253, 2, 0.45 UNION ALL SELECT 253, 5, 0.15 UNION ALL SELECT 254, 6, 0.05 UNION ALL SELECT 254, 66, 0.8 UNION ALL SELECT 254, 2, 0.105 UNION ALL SELECT 254, 4, 0.0225 UNION ALL SELECT 254, 5, 0.0225 select * from @finddupseries The records for portid 250 and 254 match. Is there any way I can write a query to detect this? edit: yes, the entire series must match. Also, if there was a way to determine which one it DID match would be helpful as the actual table has around 10k records. thanks!

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  • Powershell wait for file to delete, then copy a folder

    - by user3317623
    Morning guys, I have a couple of scripts that have to sync a folder from the network server, to the local terminal server, and lastly into the %LOCALAPPDATA%. I need to first check if a folder is being synced (this is done by creating a temporary COPYING.TXT on the server), and wait until that is removed, THEN copy to %LOCALAPPDATA%. Something like this: Server-side script executes, which syncs my folder to all of my terminal servers. It creates a COPYING.TXT temporary file, which indicates the sync is in progress. Once the sync is finished, the script removes the COPYING.TXT If someone logs on during the sync, I need a script to wait until the COPYING.TXT is deleted I.E the sync is finished, then resume the local sync into their %LOCALAPPDATA%. do{cp c:\folder\program $env:LOCALAPPDATA} while(!(test-path c:\folder\COPYING.txt)) (So that copies the folder while the file DOESN'T exist, but I don't think that exits cleanly) I cannot format the above as code for some reason I'm sorry? Or: while(!(test-path c:\folder\COPYING.txt)){ cp c:\folder\program $env:LOCALAPPDATA\ -recurse -force if (!(test-path c:\folder\program)){return} } But that script quits if the COPYING.TXT exists. I think I need to create a function and insert that function within itself, or a nested while loop, but that is starting to make my head hurt. Any help would be greatly appreciated. Thanks guys.

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  • MySQL Delete Records Older Than X Minutes?

    - by sajanNOPPIX
    I've searched quite a bit and found a few solutions that didn't end up working for me and can't understand why. I have a table with a timestamp column. The MySQL type for this column is 'datetime'. I insert into this table the following from PHP. date('Y-m-d H:i:s') This enters, what looks like the correct value for the MySQL date time. 2012-06-28 15:31:46 I want to use this column to delete rows that are older than say 10 minutes. I'm running the following query, but it's not working. It affects 0 rows. DELETE FROM adminLoginLog WHERE timestamp < (NOW() - INTERVAL 10 MINUTE); Can anyone shed some light as to what I'm doing wrong and why it's not working properly? Thanks. Update: It looks like my first issue is that I'm using DATETIME when I should be using the TIMESTAMP data type. I'm updating my code to do that now. Thanks.

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