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• Premature optimization is the root of all evil, but can it ever be too late?

  - by polygenelubricants

  "We should forget about small efficiencies, say about 97% of the time: premature optimization is the root of all evil" So what is that 3% like? Can the avoidance of premature optimization ever be taken too extreme that it does more harm than good? Even if it's rare, has there been a case of a real measurable software engineering disaster due to complete negligence to optimize early in the process? Bonus question: is software engineering pretty much the only field that has such a counter intuitive principle regarding doing something earlier rather than later before things potentially become too big a problem to fix? Personal question: how do you justify something as premature optimization and not just a case of you being lazy/ignorant/dumb?

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• Looking for solution to persist rows sequence in a database table that allow efficient reordering at

  - by Chau Chee Yang

  I have a database table. There is a field name "Sequence" that indicate sequence when user presents the rows in report or grid visually. When the rows are retrieved and presented in a grid, there are few UI gadget that allow user to reorder the rows arbitrary. The new sequence will be persist in database table when user commit the changes. Here are some UI operations: Move to first Move to last Move up 1 row Move down 1 row multi-select rows and move up or down multi-select rows and drag to new position For operation like "Move to first" or "Move to Last", it usually involve many rows and the sequence those rows would need to be updated accordingly. This may not be efficient enough at runtime. It is a common practice to use INTEGER as sequence's data type. Other solution is using "DOUBLE" or "FLOAT" that could overcome the mass update of row sequence but we will face problem if we reach the limit of precision.

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• How do I add multiple joins (Fetches) to a joined table using nhibernate and LINQ ?

  - by ooo

  i have these tables /entities VacationRequestDate table which has a VacationRequestId field that links with VacationRequest table VacationRequest has PersonId and RequestStatusId fields that links with Person and RequestStatus respectively. i have this query so far: IEnumerable<VacationRequestDate> dates = Session.Query<VacationRequestDate>().Fetch(r => r.VacationRequest).ThenFetch(p=>p.RequestStatus).ToList(); this works fine and joins with VacationRequest and then VacationRequest joins with RequestStatus but i can't figure out how to add an additional EAGER join to the VacationRequest table. If i add a Fetch at the end, it refers to the VacationRequestDate table If i add a ThenFetch at the end, it refers to the RequestStatus table I can't find any api that will refer to the VacationRequest table as the reference point. how would you add multiple joins to a joined table using nhibernate LINQ ?

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• Drawing information from relational databases in Rails

  - by Trip

  I am trying to pull the name of the Artist from the Albums database. These are my two models class Album < ActiveRecord::Base belongs_to :artist validates_presence_of :title validates_length_of :title, :minimum => 5 end class Artist < ActiveRecord::Base has_many :albums end And here is the Albums Controller def index @ albums = Album.all respond_to do |format| format.html # index.html.erb format.xml { render :xml => @albums } end end And the View from the index: <% @albums.each do |album| %> <tr> <td><%=h album.id %></td> <td><%=h album.title %></td> <td><%=h album.artist.name %></td> </tr <% end %> My end result html is coming out like this for the artist field! # and if i set it to artist.name I get this: undefined method `name' for nil:NilClass

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• Implementing Iterable in Java

  - by Artium

  I have the following code public class A extends Iterable<Integer> { ... public Iterator<Integer> iterator() { return new Iterator<Integer>() { A a; public boolean hasNext() { ... } public Integer next() { ... } public void remove(){ ... } }; I would like to initialize the "a" field in the anonymous class with the instance of A that iterator method was called on. Is it possible? Thank you.

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• SQL Server 2008 GUID column is all 0's

  - by Andy Evans

  I'm hoping this is a simple goof I did on my end ... I have a table in my database set up like so: column name: widget_guid data type: uniqueidentifier allow nulls: false default value: newid() identity: false row guid: true When records are created (via LINQ to SQL) that the values in this field are formatted as a GUID but contain all 0's My assumption was that when a new record was created, that a guid would be autogenerated for that column, much like an auto-incrementing row id. Is this not true? Any help would be greatly appreciated. Thanks.

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• Read from POS Devices

  - by Garhwali Bhai

  Hi Experts, What would be the best design for a Java web based application to read Check or Credit Card from POS Devices which are configured/installed at client machine? The design which I have decided is: When cashier selects payment mode as 'Check' or 'Credit Card' open a pop-up. From pop-up, I am calling an Applet through JNLP which implements JPOS API to communicate with POS devices at client machine. When cashier swipes or inserts check, Applet class read them and send the information back to the pop-up window. Pop up window call the parent window, populate all the required field and close the pop-up.

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• DataMapper: using auto_migrate! with many-to-many dependencies?

  - by pschuegr

  Hi, I'm trying to migrate my app from MySql to Postgresql, using Rails3-pre and the latest DataMapper. I have several models which are related through many-to-many relationships using :through = Resource, which means that DataMapper creates a join table with foreign keys for both models. I can't auto_migrate! these changes, because I keep getting this: ERROR: cannot drop table users because other objects depend on it DETAIL: constraint artist_users_owner_fk on table artist_users depends on table users constraint site_users_owner_fk on table site_users depends on table users HINT: Use DROP ... CASCADE to drop the dependent objects too. I have tried everything I can think of, and thought I had things working when I added :constraint = :skip to the field definition, but I keep getting that error back when I try and run auto_migrate. I thought that :skip meant that it would ignore the dependents, but maybe that only applies for deleting rows and not dropping tables? I should mention that I can run auto_migrate after i nuke the db once, but after that, errors. Any suggestions or advice much appreciated.

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• Are there programming languages that rely on non-latin alphabets?

  - by Jaxsun

  Every programming language I have ever seen has been based on the Latin alphabet, this is not surprising considering I live in Canada... But it only really makes sense that there would be programming languages based on other alphabets, or else bright computer scientists across the world would have to learn a new alphabet to go on in the field. I know for a fact that people in countries dominated by other alphabets develop languages based off the Latin alphabet (eg. Ruby from Japan), but just how common is it for programming languages to be based off of other alphabets like Arabic, or Cyrillic, or even writing systems which are not alphabetic but rather logographic in nature such as Japanese Kanji? Also are any of these languages in active widespread use, or are they mainly used as teaching tools? This is something that has bugged me since I started programming, and I have never run across someone who could think of a real answer.

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• Considering getting into reverse engineering/disassembly

  - by Zombies

  Assuming a decent understanding of assembly on common CPU architectures (eg: x86), how can one explore a potential path (career, fun and profit, etc) into the field of reverse engineering? There is so little educational guides out there so it is difficult to understand what potential uses this has today (eg: is searching for buffer overflow exploits still common, or do stack monitoring programs make this obselete?). I am not looking for any step by step program, just some relevant information such as tips on how to efficiently find a specific area of a program. Basic things in the trade. As well as what it is currently being used for today. So to recap, what current uses does reverse engineering yield today? And how can one find some basic information on how to learn the trade (again it doesn't have to be step-by-step, just anything which can through a clue would be helpful).

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• YUI Autocomplete: search after pasting?

  - by rassie

  I'm using an auto-complete widget from YUI to implement live search as in the examples. However, it works fine when search text is typed in, but fails to work when the text is pasted into the field. Which would be the proper way to initiate an autocompletion on paste? Haven't found anything for that in the documentation... EDIT: Pasting is not Ctrl-V, it's usually "Paste" from the context-menu. YUI does react to a keypress, but doesn't if anything is pasted by the mouse.

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• Preventing Spoofing with Paypal

  - by wcpro

  I have a scenario where i need to have a user checkout through PayPal and then once we receive the payment then we create a membership record in our membership site. The PayPal requires a "return" field when you submit the form button that will take the user back to our page once the order has been successfully processed. On that page is where we actually track the sale and fire a chunk of javascript to track the sale. So my question is this, how can i make sure that the return page comes from PayPal and is not spoofed by a user in the system. I know there is a way to use the notify_url to have PayPal post back to our system, but in this case i have to run a chunk of javascript. Is there an easy way to do this, or would i have to write some looping/timeout function that checks to see if the notify post has come through? Im using .net to do the posting to paypal

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• Make XStream ignore one specific private variable

  - by Tigraine

  Hi guys, I have a little problem with a class I am currently writing a save function for. I'm using XStream (com.thoughtworks.xstream) to serialize a class to XML using the DOMDriver. The class looks like this: public class World { private Configuration config; public World(Configuration config) { this.config = config; } } So, the issue here is that I do not want to serialize Configuration when serializing world, rather I'd like to give XStream a preconstructed Configuration instance when calling fromXml(). Problem here is mainly class design, Configuration holds a private reference to the GUI classes and therefore serializing Configuration means serializing the whole application completely with GUI etc.. And that's kind of bad. Is there a way to instruct XStream to not serialize the private field config, and upon load supply XStream with a configuration instance to use? greetings Daniel

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• Java: JPA classes, refactoring from Date to DateTime

  - by bguiz

  With a table created using this SQL Create Table X ( ID varchar(4) Not Null, XDATE date ); and an entity class defined like so @Entity @Table(name = "X") public class X implements Serializable { @Id @Basic(optional = false) @Column(name = "ID", nullable = false, length = 4) private String id; @Column(name = "XDATE") @Temporal(TemporalType.DATE) private Date xDate; //java.util.Date ... } With the above, I can use JPA to achieve object relational mapping. However, the xDate attribute can only store dates, e.g. dd/MM/yyyy. How do I refactor the above to store a full date object using just one field, i.e. dd/MM/yyyy HH24:mm?

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• Adding business logic to a domain class using a getter style method name

  - by Richard Paul

  I'm attempting to add a method to a grails domain class, e.g. class Item { String name String getReversedName() { name.reverse() } } When I attempt to load the application using grails console I get the following error: Caused by: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'sessionFactory':Invocation of init method failed; nested exception is org.hibernate.PropertyNotFoundException: Could not find a setter for property reversedName in class Item ... 18 more It looks like Hibernate is interpreting getReversedName() as a getter for a property, however in this case it is a derived field and hence should not be persisted. Obviously in my actual code the business logic I'm exposing is more complex but it isn't relevant to this question. I want to be able to call item.reversedName in my code/gsps. How can I provide property (getter) access to a method in a Grails domain class without Grails attempting to map it with Hibernate?

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• how to have separate keys per record in mongo_mapper + Rails

  - by Vitaly Kushner

  When I'm adding a record in mongodb I can specify whatever keys I want and it will store it in the db. The problem is that it will remember those keys for the next time I insert another record. so for example if I do the following: Product.create :foo => 123 and then Product.create :bar => 456 I get :foo => nil field in the 2nd record. This is definitely not a limitation of mongodb itself, since if I restart the rails console and create yet another record with different set of columns, it will not add the columns from the 1st 2 records. So it seems like mongomapper remembers all the keys used and inserts them all into all records, even if values are not provided. The question is obviously: how do I disable this crazy attributes explosion? Basically I want only the 'permanent' keys that I specify in the model to be in every record, but all the 'extra' attributes to be specified per record and not to mess the consequent records.

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• Should app using VCL migrate?

  - by Fdr

  Is VCL dead, or does it have a future as a GUI library? As CLX ended, is there any chance for cross-platform support in future releases? I've had to do some work with legacy app that uses Borland's VCL(BCB6). Now that new features have to be implemented, it's necessary to revalue alternatives. Whether to stick with VCL or migrate to some other library/framework. I've never read much what's happening in the field Embarcadero(Borland) tools. At least there seems to be only few VCL tagged questions here in SO and no much luck with google either.

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• How can I check if a binary string is UTF-8 in mysql?

  - by Piotr Czapla

  I've found a Perl regexp that can check if a string is UTF-8 (the regexp is from w3c site). $field =~ m/\A( [\x09\x0A\x0D\x20-\x7E] # ASCII | [\xC2-\xDF][\x80-\xBF] # non-overlong 2-byte | \xE0[\xA0-\xBF][\x80-\xBF] # excluding overlongs | [\xE1-\xEC\xEE\xEF][\x80-\xBF]{2} # straight 3-byte | \xED[\x80-\x9F][\x80-\xBF] # excluding surrogates | \xF0[\x90-\xBF][\x80-\xBF]{2} # planes 1-3 | [\xF1-\xF3][\x80-\xBF]{3} # planes 4-15 | \xF4[\x80-\x8F][\x80-\xBF]{2} # plane 16 )*\z/x; But I'm not sure how to port it to MySQL as it seems that MySQL don't support hex representation of characters see this question. Any thoughts how to port the regexp to MySQL? Or maybe you know any other way to check if the string is valid UTF-8? UPDATE: I need this check working on the MySQL as I need to run it on the server to correct broken tables. I can't pass the data through a script as the database is around 1TB.

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• MySQL import in phpmyadmin (CSV) chokes on quotes

  - by Andrew Swift

  I am trying to import a .csv file into a MySQL table via phpMyAdmin. The .csv file is separated by pipes, formated like this: data|d'ata|d'a"ta|dat"a| data|"da"ta|data|da't'a| dat'a|data|da"ta"|da'ta| The data contains quotes. I have no control over the format in which I recieve the data -- it is generated by a third party. The problem comes when there is a | followed by a double quote. I always get an "invalid field count in CSV input on line N" error. I am uploading the file from the import page, using Latin1, CSV, terminated by |, separated by ". I would like to just change the "enclosed by" character, but I keep getting "Invalid parameter for CSV import: Fields enclosed by". I have tried various characters with no success. How can I tell MySQL to accept this format in phpMyAdmin? Setting up these tables is the first step in writing a program that will use uploaded gzipped .csv files to maintain the catalog of an e-commerce site.

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• Sharing variable within different javascript file at client side

  - by Aman

  I was actually going through this link. which explains how we can share global variable across multiple js. but the point is what need to be done if I am getting some variable into one js and need to pass to another one mentioned in same document after the 1st one. approach which followed was: Script 1 <script type="text/javascript" src="js/client.js"></script> body added some hidden input with id myHiddenId, where values are set using client.js Script 2 <script type="text/javascript" src="js/anotherJS.js"></script> inside script 2 I am simply using $("#myHiddenId").val(); and using for my purpose. I want to know whether I am following correct approach, because that hidden field may have some data which client should not get aware of. is there any other way through which I can pass the variable values across the js files ? Since I am at beginner level hence digging up some resources/books but still no luck.

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• Are the built-in images in iPhone documented, and is there a list of their names somewhere?

  - by Alex Gosselin

  I discovered somewhat by accident that if you make a UIButton in Interface Builder and type in Plus in the image field, a + image appears for the button. A similar result comes from typing Minus. I am wondering if this is a bug, or if there is some way the poor programmers can access the built-in general GUI images from other apple apps, such as the green +, the red -, the detail disclosure chevron, the big red "Delete Contact" or similarly styled button, etc. Has anyone else encountered this, or know where to access these things in Xcode? It makes sense to me that they should be usable, cause the Apple HIG seems to be all about making things recognizable and intuitive, and using them the way other apps use them.

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• CSS: Size of buttons in Chrome is different than Firefox

  - by Hank

  I have the following HTML code: <style type="text/css"> .submitbutton{margin-left:-2px} </style> ... <form> ... <input class=submitbutton type=submit value="Create Listings" /> </form> In Firefox, the input button has more padding than in Chrome. Any ideas why? UPDATE: If you're wondering why I have the negative margin - it's because between the input field and the input button - there is too much space.

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• Rails: has_many association with a table in another database and without foreign key

  - by Fernando

  Here is my situation. I have model called Account. An account can have one or more contracts. The problem is that i'm dealing with a legacy application and each account's contracts are stored in a different database. Example: Account 1's contract are in account1_db.contracts. Account 2's contract are in account2_db.contracts. The database name is a field stored in accounts table. How can i make rails association work with this? This is a legacy PHP application and i simply can't change it to store everything in one table. I need to make it work somehow. I tried this, but it didn't worked: has_many :contracts, :conditions => [lambda{ Contract.set_table_name(self.database + '.contracts'); return '1' }] Any ideas?

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• How do I retrieve readonly values when using a DetailsView control to update a record?

  - by lincolnk

  I'm using a detailsview control to update a record, however in this particular case there's only one field that can be changed out of a many. The update method for my object takes all fields as parameters. When the detailsview's updating method fires, the values for the readonly fields (those rendered as a Label) are not available in the e.NewValues collection. I'm currently grabbing a reference to the object when the detailsview is databound (in the objectdatasource selected event handler), storing it in session and manually adding entries to the e.NewValues collection when updating fires. It works but seems kind of heavy handed. So, is there a better way to get the read only values back into my update method? Or is there a better way of doing this altogether?

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• Selecting keys based on metadata, possible with Amazon S3?

  - by nbv4

  I'm sending files to my S3 bucket that are basically gzipped database dumps. They keys are a human readable date ("2010-05-04.dump"), and along with that, I'm setting a metadata field to the UNIX time of the dump. I want to write a script that retrieve the latest dump from the bucket. That is to say I want the the key with the largest unix time metadata value. Is this possible with Amazon S3, or is this not how S3 is meant to work? I'm using both the command line tool aws, and the python library boto

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