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• Where is my python script spending time? Is there "missing time" in my cprofile / pstats trace?

  - by fmark

  I am attempting to profile a long running python script. The script does some spatial analysis on raster GIS data set using the gdal module. The script currently uses three files, the main script which loops over the raster pixels called find_pixel_pairs.py, a simple cache in lrucache.py and some misc classes in utils.py. I have profiled the code on a moderate sized dataset. pstats returns: p.sort_stats('cumulative').print_stats(20) Thu May 6 19:16:50 2010 phes.profile 355483738 function calls in 11644.421 CPU seconds Ordered by: cumulative time List reduced from 86 to 20 due to restriction <20> ncalls tottime percall cumtime percall filename:lineno(function) 1 0.008 0.008 11644.421 11644.421 <string>:1(<module>) 1 11064.926 11064.926 11644.413 11644.413 find_pixel_pairs.py:49(phes) 340135349 544.143 0.000 572.481 0.000 utils.py:173(extent_iterator) 8831020 18.492 0.000 18.492 0.000 {range} 231922 3.414 0.000 8.128 0.000 utils.py:152(get_block_in_bands) 142739 1.303 0.000 4.173 0.000 utils.py:97(search_extent_rect) 745181 1.936 0.000 2.500 0.000 find_pixel_pairs.py:40(is_no_data) 285478 1.801 0.000 2.271 0.000 utils.py:98(intify) 231922 1.198 0.000 2.013 0.000 utils.py:116(block_to_pixel_extent) 695766 1.990 0.000 1.990 0.000 lrucache.py:42(get) 1213166 1.265 0.000 1.265 0.000 {min} 1031737 1.034 0.000 1.034 0.000 {isinstance} 142740 0.563 0.000 0.909 0.000 utils.py:122(find_block_extent) 463844 0.611 0.000 0.611 0.000 utils.py:112(block_to_pixel_coord) 745274 0.565 0.000 0.565 0.000 {method 'append' of 'list' objects} 285478 0.346 0.000 0.346 0.000 {max} 285480 0.346 0.000 0.346 0.000 utils.py:109(pixel_coord_to_block_coord) 324 0.002 0.000 0.188 0.001 utils.py:27(__init__) 324 0.016 0.000 0.186 0.001 gdal.py:848(ReadAsArray) 1 0.000 0.000 0.160 0.160 utils.py:50(__init__) The top two calls contain the main loop - the entire analyis. The remaining calls sum to less than 625 of the 11644 seconds. Where are the remaining 11,000 seconds spent? Is it all within the main loop of find_pixel_pairs.py? If so, can I find out which lines of code are taking most of the time?

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• how send data record using SendMessage(..) in separate process

  - by XBasic3000

  i use to send a data on two separate process but it fails. it works only under same process... this is concept. //----------------------------------------------------------------------------------- MainApps //----------------------------------------------------------------------------------- Type PMyrec = ^TMyrec; TMyrec = Record name : string; add : string; age : integer; end; :OnButtonSend var aData : PMyrec; begin new(aData); aData.Name := 'MyName'; aData.Add := 'My Address'; aData.Age : 18; SendMessage(FindWindow('SubApps'),WM_MyMessage,0,Integer(@aData)); end; //----------------------------------------------------------------------------------- SubApps //----------------------------------------------------------------------------------- Type PMyrec = ^TMyrec; TMyrec = Record name : string; add : string; age : integer; end; :OnCaptureMessage var aData : PMyrec; begin aData := PMyrec(Msg.LParam); showmessage(aData^.Name); end;

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• Which key value store is the most promising/stable?

  - by Mike Trpcic

  I'm looking to start using a key/value store for some side projects (mostly as a learning experience), but so many have popped up in the recent past that I've got no idea where to begin. Just listing from memory, I can think of: CouchDB MongoDB Riak Redis Tokyo Cabinet Berkeley DB Cassandra MemcacheDB And I'm sure that there are more out there that have slipped through my search efforts. With all the information out there, it's hard to find solid comparisons between all of the competitors. My criteria and questions are: (Most Important) Which do you recommend, and why? Which one is the fastest? Which one is the most stable? Which one is the easiest to set up and install? Which ones have bindings for Python and/or Ruby? Edit: So far it looks like Redis is the best solution, but that's only because I've gotten one solid response (from ardsrk). I'm looking for more answers like his, because they point me in the direction of useful, quantitative information. Which Key-Value store do you use, and why? Edit 2: If anyone has experience with CouchDB, Riak, or MongoDB, I'd love to hear your experiences with them (and even more so if you can offer a comparative analysis of several of them)

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• Which book should I choose?

  - by sebastianlarsson

  Hi guys, I'm looking for a good read on object oriented design. The two books I'm currently looking Head First Design Patterns and Head First Object object-oriented analysis & design. They seem very similar when looking at the contents and browsing through available sample text. Which one would be the best choice? About myself: I have a bachelor in computer science and I am currently studying Msc. Software Quality Engineering (read Software Engineering with focus on Quality). I am already confident in object-oriented design and have a lot of programming courses in my backpack. I have done games in c++, courses in advanced java programming (I am SCJP certified), but my preferred language is C#. I have also worked with Java for the last 7 months while studying. I am currently also studying for certificates in C# (apart from my usual studies). So I believe I have the prerequisites of actually understanding the contents of both books. Reason: I just want to be better and keep evolving as a programmer. I think it is fun. I believe Bert Bates and Kathy Sierra are involved in both these books and I have previously read their SCJP preparation book in java. I really do enjoy their style of writing. Other books which I am considering are: Clean Code: A Handbook Of Agile Software Craftsmanship Thx in advance Sebastian

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• ECM (Niche Vs Mass Market)

  - by Luj Reyes

  Hi Everyone, I recently started a little company with a couple of guys. Ours is the typical startup, a lot of ideas, dreams, talent and work hours :P. Our initial business plan was to develop a DM (Document Manager) with several features found on DropBox and other tools but with a big differentiator. Then we got in the team this Business Guy (I must say that several of us could be called 'Business Guys' but we are mainly hackers, he is just Another 'Networking Guy'), and along with him came this market analysis for a DM aimed at a very specific and narrow niche. We have many elements to believe in his market study and the idea is the classic "The market is X million, so if we grab a 10%...", and the market is really there to grab because all big providers deemed it too little and fled, let's say that the market is 5 million USD and demand very specific features. If we decide to go for this niche product we face a sales cycle of about 7 months, and the main goal of these revenue is to develop more ambitious projects. (Institutional VC is out of the question if you want to keep a marginal ownership of your company in my country). The only overlap between the niche and the mass market product features is the ability to store documents; everything else requires that we focus all of our efforts towards one or the other. I've studied a lot about the differences between Mass and Niche Markets, but I want to hear from people with actual experience. So everything comes down to this: If you have a really “saleable” idea what is the right thing to do: to go for the niche or go for the big prize and target primarily the mass market? Thanks for your input

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• Key Tips in WPF

  - by Brad Leach

  Office 2007 and the Ribbon introduced the concept of "Key Tips". In short, every single command in the Ribbon receives a letter which you can press to activate that command. ... The letters are indicated by small "KeyTips" which indicate the letter to press to activate the control. KeyTips are displayed using the Alt key, so using them feels similar to how menu navigation works in Windows. (Source: http://blogs.msdn.com/jensenh/archive/2006/04/12/574930.aspx) An example of the Key Tips can be shown as follows. In this diagram, the use has pressed the ALT key, and is awaiting further input. Are there any WPF Open Source examples of "Key Tips"? How would you go about implementing something like this feature in a generic way (i.e. not requiring a Ribbon)? How would you implement this using a MVVM pattern (given that ICommand does not support InputBindings). Note: ActiPro have implemented this feature in their implementation of a Ribbon, but they have not released source code.

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• Writing catch block with cleanup operations in Java ...

  - by kedarmhaswade

  I was not able to find any advise on catch blocks in Java that involve some cleanup operations which themselves could throw exceptions. The classic example is that of stream.close() which we usually call in the finally clause and if that throws an exception, we either ignore it by calling it in a try-catch block or declare it to be rethrown. But in general, how do I handle cases like: public void doIt() throws ApiException { //ApiException is my "higher level" exception try { doLower(); } catch(Exception le) { doCleanup(); //this throws exception too which I can't communicate to caller throw new ApiException(le); } } I could do: catch(Exception le) { try { doCleanup(); } catch(Exception e) { //ignore? //log? } throw new ApiException(le); //I must throw le } But that means I will have to do some log analysis to understand why cleanup failed. If I did: catch(Exception le) { try { doCleanup(); } catch(Exception e) { throw new ApiException(e); } It results in losing the le that got me here in the catch block in the fist place. What are some of the idioms people use here? Declare the lower level exceptions in throws clause? Ignore the exceptions during cleanup operation?

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• Hazelcast Distributed Executor Service KeyOwner

  - by János Veres

  I have problem understanding the concept of Hazelcast Distributed Execution. It is said to be able to perform the execution on the owner instance of a specific key. From Documentation: <T> Future<T> submitToKeyOwner(Callable<T> task, Object key) Submits task to owner of the specified key and returns a Future representing that task. Parameters: task - task key - key Returns: a Future representing pending completion of the task I believe that I'm not alone to have a cluster built with multiple maps which might actually use the same key for different purposes, holding different objects (e.g. something along the following setup): IMap<String, ObjectTypeA> firstMap = HazelcastInstance.getMap("firstMap"); IMap<String, ObjectTypeA_AppendixClass> secondMap = HazelcastInstance.getMap("secondMap"); To me it seems quite confusing what documentation says about the owner of a key. My real frustration is that I don't know WHICH - in which map - key does it refer to? The documentation also gives a "demo" of this approach: import com.hazelcast.core.Member; import com.hazelcast.core.Hazelcast; import com.hazelcast.core.IExecutorService; import java.util.concurrent.Callable; import java.util.concurrent.Future; import java.util.Set; import com.hazelcast.config.Config; public void echoOnTheMemberOwningTheKey(String input, Object key) throws Exception { Callable<String> task = new Echo(input); HazelcastInstance hz = Hazelcast.newHazelcastInstance(); IExecutorService executorService = hz.getExecutorService("default"); Future<String> future = executorService.submitToKeyOwner(task, key); String echoResult = future.get(); } Here's a link to the documentation site: Hazelcast MultiHTML Documentation 3.0 - Distributed Execution Did any of you guys figure out in the past what key does it want?

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• Is it possible to write an IIS URL Rewrite Rule that examines content of HTTP Post?

  - by JohnRudolfLewis

  I need to split a portion of functionality away from a legacy ISAPI dll onto another solution (ASP.NET MVC most likely). IIS7's URL Rewrite sounded like a perfect candidate for the job, but it turns out I cannot find a way to configure the rules the way I need. I need to write a rule that examines the content of the HTTP post for a particular value. i.e. <form method="post" action="legacy_isapi.dll"> <input name="foo" /> </form> if (Request.Form["foo"] == "bar") Context.RewritePath("/some_other_url/on_the_same_machine/foo/bar"); As a proof of concept, I was able to create an IHttpModule that examines context.Request.Form collection and performs a rewrite when certain parameters are present. I installed this module in my website, and it works. Rather than a custom module, however, I'd rather extend the existing URL Rewrite module to support examining the content of the HTTP Post as one of its rules. Is this possible?

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• FLV performance and garbage collection

  - by justinbach

  I'm building a large flash site (AS3) that uses huge FLVs as transition videos from section to section. The FLVs are 1280x800 and are being scaled to 1680x1050 (much of which is not displayed to users with smaller screens), and are around 5-8 seconds apiece. I'm encoding the videos using On2's hi-def codec, VP6-S, and playback is pretty good with native FLV players, Perian-equipped Quicktime, and simple proof-of-concept FLV playback apps built in AS3. The problem I'm having is that in the context of the actual site, playback isn't as smooth; the framerate isn't quite as good as it should be, and more problematically, there's occasional jerkiness and dropped frames (sometimes pausing the video for as long as a quarter of a second or so). My guess is that this is being caused by garbage collection in the Flash player, which happens nondeterministically and is therefore hard to test and control for. I'm using a single instance of FLVPlayback to play the videos; I originally was using NetStream objects and so forth directly but switched to FLVPlayback for this reason. Has anyone experienced this sort of jerkiness with FLVPlayback (or more generally, with hi-def Flash video)? Am I right about GC being the culprit here, and if so, is there any way to prevent it during playback of these system-intensive transitions?

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• Best practices for managing updating a database with a complex set of changes

  - by Sarge

  I am writing an application where I have some publicly available information in a database which I want the users to be able to edit. The information is not textual like a wiki but is similar in concept because the edits bring the public information increasingly closer to the truth. The changes will affect multiple tables and the update needs to be automatically checked before affecting the public tables. I'm working on the design and I'm wondering if there are any best practices that might help with some particular issues. I want to provide undo capability. I want to show the user the combined result of all their changes. When the user says they're done, I need to check the underlying public data to make sure it hasn't been changed by somebody else. My current plan is to have the user work in a set of tables setup to be a private working area. Once they're ready they can kick off a process to check everything and update the public tables. Undo can be recorded using Command pattern saving to a table. Are there any techniques I might have missed or useful papers or patterns? Thanks in advance!

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• I have two choices of Master's classes this fall. Which is the most useful?

  - by ahplummer

  (For background purposes and context): I am a Software Engineer, and manage other Software Engineers currently. I kind of wear two hats right now: one of a programmer, and one as a 'team lead'. In this regard, I've started going back to school to get my Master's degree with an emphasis in Computer Science. I already have a Bachelor's in Computer Science, and have been working in the field for about 13 years. Our primary development environment is a Windows environment, writing in .NET, Delphi, and SQL Server. Choice #1: CST 798 DATA VISUALIZATION Course Description: Basically, this is a course on the "Processing" language: http://processing.org/ Choice #2: CST 711 INFORMATICS Course Description: (From catalog): Informatics is the science of the use and processing of data, information, and knowledge. This course covers a variety of applied issues from information technology, information management at a variety of levels, ranging from simple data entry, to the creation, design and implementation of new information systems, to the development of models. Topics include basic information representation, processing, searching, and organization, evaluation and analysis of information, Internet-based information access tools, ethics and economics of information sharing.

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• belongs_to with multiple models

  - by julie p

  Hi there! I am a Rails noob and have a question. I have a feed aggregator that is organized by this general concept: Feed Category (books, electronics, etc) Feed Site Section (home page, books page, etc) Feed (the feed itself) Feed Entry So: class Category < ActiveRecord::Base has_many :feeds has_many :feed_entries, :through => :feeds, :limit => 5 validates_presence_of :name attr_accessible :name, :id end class Section < ActiveRecord::Base has_many :feeds has_many :feed_entries, :through => :feeds, :limit => 5 attr_accessible :name, :id end class Feed < ActiveRecord::Base belongs_to :categories belongs_to :sections has_many :feed_entries validates_presence_of :name, :feed_url attr_accessible :name, :feed_url, :category_id, :section_id end class FeedEntry < ActiveRecord::Base belongs_to :feed belongs_to :category belongs_to :section validates_presence_of :title, :url end Make sense? Now, in my index page, I want to basically say... If you are in the Category Books, on the Home Page Section, give me the feed entries grouped by Feed... In my controller: def index @section = Section.find_by_name("Home Page") @books = Category.find_by_name("Books") end In my view: <%= render :partial => 'feed_list', :locals => {:feed_group => @books.feeds} -%> This partial will spit out the markup for each feed entry in the @books collection of Feeds. Now what I need to do is somehow combine the @books with the @section... I tried this: <%= render :partial => 'feed_list', :locals => {:feed_group => @books.feeds(:section_id => @section.id)} -%> But it isn't limiting by the section ID. I've confirmed the section ID by using the same code in the console... Make sense? Any advice? Thanks!

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• Packaging reference documentation with jar file

  - by soren.enemaerke

  We are porting our .NET library to a java equivalent and is now looking at how to distribute this port. Packaging the classes into a jar-file seems like best practice and we would then ship this jar file in a zip along with some license terms. But what about the documentation? In .NET land it seems like best practice to distribute the xml file that can be consumed by tooling (Visual Studio) but we can't seem to find such best practices for java. We have javadoc comments on our public classes and interfaces, so we are just looking for a way to generate and distribute these comments in a way that is developer friendly (we're thinking easily consumed from various IDEs). What are developers expecting and how do you best deliver this? We would really prefer to bundle the documentation along with the jar file and not have to host the documentation on our website EDIT: We would like for our documentation to appear inside the java IDEs so we want to provide the documentation in a way that integrates into the IDEs as gracefully as possible. In .NET land this is as an xml file placed next to the .dll file, but is there a similar concept for jar files that enables the integration into tooling? PS: We are developing in Eclipse and have an ant task doing the building and jar-file packaing in our automated build.

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• How to perform Linq select new with datetime in SQL 2008

  - by kd7iwp

  In our C# code I recently changed a line from inside a linq-to-sql select new query as follows: OrderDate = (p.OrderDate.HasValue ? p.OrderDate.Value.Year.ToString() + "-" + p.OrderDate.Value.Month.ToString() + "-" + p.OrderDate.Value.Day.ToString() : "") To: OrderDate = (p.OrderDate.HasValue ? p.OrderDate.Value.ToString("yyyy-mm-dd") : "") The change makes the line smaller and cleaner. It also works fine with our SQL 2008 database in our development environment. However, when the code deployed to our production environment which uses SQL 2005 I received an exception stating: Nullable Type must have a value. For further analysis I copied (p.OrderDate.HasValue ? p.OrderDate.Value.ToString("yyyy-mm-dd") : "") into a string (outside of a Linq statement) and had no problems at all, so it only causes an in issue inside my Linq. Is this problem just something to do with SQL 2005 using different date formats than from SQL 2008? Here's more of the Linq: dt = FilteredOrders.Where(x => x != null).Select(p => new { Order = p.OrderId, link = "/order/" + p.OrderId.ToString(), StudentId = (p.PersonId.HasValue ? p.PersonId.Value : 0), FirstName = p.IdentifierAccount.Person.FirstName, LastName = p.IdentifierAccount.Person.LastName, DeliverBy = p.DeliverBy, OrderDate = p.OrderDate.HasValue ? p.OrderDate.Value.Date.ToString("yyyy-mm-dd") : ""}).ToDataTable(); This is selecting from a List of Order objects. The FilteredOrders list is from another linq-to-sql query and I call .AsEnumerable on it before giving it to this particular select new query. Doing this in regular code works fine: if (o.OrderDate.HasValue) tempString += " " + o.OrderDate.Value.Date.ToString("yyyy-mm-dd");

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• Bi-directional view model syncing with "live" collections and properties (MVVM)

  - by Schneider

  I am getting my knickers in a twist recently about View Models (VM). Just like this guy I have come to the conclusion that the collections I need to expose on my VM typically contain a different type to the collections exposed on my business objects. Hence there must be a bi-directional mapping or transformation between these two types. (Just to complicate things, on my project this data is "Live" such that as soon as you change a property it gets transmitted to other computers) I can just about cope with that concept, using a framework like Truss, although I suspect there will be a nasty surprise somewhere within. Not only must objects be transformed but a synchronization between these two collections is required. (Just to complicate things I can think of cases where the VM collection might be a subset or union of business object collections, not simply a 1:1 synchronization). I can see how to do a one-way "live" sync, using a replicating ObservableCollection or something like CLINQ. The problem then becomes: What is the best way to create/delete items? Bi-directinal sync does not seem to be on the cards - I have found no such examples, and the only class that supports anything remotely like that is the ListCollectionView. Would bi-directional sync even be a sensible way to add back into the business object collection? All the samples I have seen never seem to tackle anything this "complex". So my question is: How do you solve this? Is there some technique to update the model collections from the VM? What is the best general approach to this?

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• How do I properly implement a property in F#?

  - by Greg D

  Consider my first attempt, a simple type in F# like the following: type Test() = inherit BaseImplementingNotifyPropertyChangedViaOnPropertyChanged() let mutable prop: string = null member this.Prop with public get() = prop and public set value = match value with | _ when value = prop -> () | _ -> let prop = value this.OnPropertyChanged("Prop") Now I test this via C# (this object is being exposed to a C# project, so apparent C# semantics are desirable): [TestMethod] public void TaskMaster_Test() { var target = new FTest(); string propName = null; target.PropertyChanged += (s, a) => propName = a.PropertyName; target.Prop = "newString"; Assert.AreEqual("Prop", propName); Assert.AreEqual("newString", target.Prop); return; } propName is properly assigned, my F# Setter is running, but the second assert is failing because the underlying value of prop isn't changed. This sort of makes sense to me, because if I remove mutable from the prop field, no error is generated (and one should be because I'm trying to mutate the value). I think I must be missing a fundamental concept. What's the correct way to rebind/mutate prop in the Test class so that I can pass my unit test?

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• Memory usage in Flash / Flex / AS3

  - by ggambett

  I'm having some trouble with memory management in a flash app. Memory usage grows quite a bit, and I've tracked it down to the way I load assets. I embed several raster images in a class Embedded, like this [Embed(source="/home/gabriel/text_hard.jpg")] public static var ASSET_text_hard_DOT_jpg : Class; I then instance the assets this way var pClass : Class = Embedded[sResource] as Class; return new pClass() as Bitmap; At this point, memory usage goes up, which is perfectly normal. However, nulling all the references to the object doesn't free the memory. Based on this behavior, looks like the flash player is creating an instance of the class the first time I request it, but never ever releases it - not without references, calling System.gc(), doing the double LocalConnection trick, or calling dispose() on the BitmapData objects. Of course, this is very undesirable - memory usage would grow until everything in the SWFs is instanced, regardless of whether I stopped using some asset long ago. Is my analysis correct? Can anything be done to fix this?

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• PHP: Aggregate Model Classes or Uber Model Classes?

  - by sunwukung

  In many of the discussions regarding the M in MVC, (sidestepping ORM controversies for a moment), I commonly see Model classes described as object representations of table data (be that an Active Record, Table Gateway, Row Gateway or Domain Model/Mapper). Martin Fowler warns against the development of an anemic domain model, i.e. a class that is nothing more than a wrapper for CRUD functionality. I've been working on an MVC application for a couple of months now. The DBAL in the application I'm working on started out simple (on account of my understanding - oh the benefits of hindsight), and is organised so that Controllers invoke Business Logic classes, that in turn access the database via DAO/Transaction Scripts pertinent to the task at hand. There are a few "Entity" classes that aggregate these DAO objects to provide a convenient CRUD wrapper, but also embody some of the "behaviour" of that Domain concept (for example, a user - since it's easy to isolate). Taking a look at some of the code, and thinking along refactoring some of the code into a Rich Domain Model, it occurred to me that were I to try and wrap the CRUD routines and behaviour of say, a Company into a single "Model" class, that would be a sizeable class. So, my question is this: do Models represent domain objects, business logic, service layers, all of the above combined? How do you go about defining the responsibilities for these components?

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• How can I create a new Person object correctly in Javascript?

  - by TimDog

  I'm still struggling with this concept. I have two different Person objects, very simply: ;Person1 = (function() { function P (fname, lname) { P.FirstName = fname; P.LastName = lname; return P; } P.FirstName = ''; P.LastName = ''; var prName = 'private'; P.showPrivate = function() { alert(prName); }; return P; })(); ;Person2 = (function() { var prName = 'private'; this.FirstName = ''; this.LastName = ''; this.showPrivate = function() { alert(prName); }; return function(fname, lname) { this.FirstName = fname; this.LastName = lname; } })(); And let's say I invoke them like this: var s = new Array(); //Person1 s.push(new Person1("sal", "smith")); s.push(new Person1("bill", "wonk")); alert(s[0].FirstName); alert(s[1].FirstName); s[1].showPrivate(); //Person2 s.push(new Person2("sal", "smith")); s.push(new Person2("bill", "wonk")); alert(s[2].FirstName); alert(s[3].FirstName); s[3].showPrivate(); The Person1 set alerts "bill" twice, then alerts "private" once -- so it recognizes the showPrivate function, but the local FirstName variable gets overwritten. The second Person2 set alerts "sal", then "bill", but it fails when the showPrivate function is called. The new keyword here works as I'd expect, but showPrivate (which I thought was a publicly exposed function within the closure) is apparently not public. I want to get my object to have distinct copies of all local variables and also expose public methods -- I've been studying closures quite a bit, but I'm still confused on this one. Thanks for your help.

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• Oracle why does creating trigger fail when there is a field called timestamp?

  - by Omar Kooheji

  I've just wasted the past two hours of my life trying to create a table with an auto incrementing primary key bases on this tutorial, The tutorial is great the issue I've been encountering is that the Create Target fails if I have a column which is a timestamp and a table that is called timestamp in the same table... Why doesn't oracle flag this as being an issue when I create the table? Here is the Sequence of commands I enter: Creating the Table: CREATE TABLE myTable (id NUMBER PRIMARY KEY, field1 TIMESTAMP(6), timeStamp NUMBER, ); Creating the Sequence: CREATE SEQUENCE test_sequence START WITH 1 INCREMENT BY 1; Creating the trigger: CREATE OR REPLACE TRIGGER test_trigger BEFORE INSERT ON myTable REFERENCING NEW AS NEW FOR EACH ROW BEGIN SELECT test_sequence.nextval INTO :NEW.ID FROM dual; END; / Here is the error message I get: ORA-06552: PL/SQL: Compilation unit analysis terminated ORA-06553: PLS-320: the declaration of the type of this expression is incomplete or malformed Any combination that does not have the two lines with a the word "timestamp" in them works fine. I would have thought the syntax would be enough to differentiate between the keyword and a column name. As I've said I don't understand why the table is created fine but oracle falls over when I try to create the trigger... CLARIFICATION I know that the issue is that there is a column called timestamp which may or may not be a keyword. MY issue is why it barfed when I tried to create a trigger and not when I created the table, I would have at least expected a warning. That said having used Oracle for a few hours, it seems a lot less verbose in it's error reporting, Maybe just because I'm using the express version though. If this is a bug in Oracle how would one who doesn't have a support contract go about reporting it? I'm just playing around with the express version because I have to migrate some code from MySQL to Oracle.

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• t-sql most efficient row to column? crosstab for xml path, pivot

  - by ajberry

  I am looking for the most performant way to turn rows into columns. I have a requirement to output the contents of the db (not actual schema below, but concept is similar) in both fixed width and delimited formats. The below FOR XML PATH query gives me the result I want, but when dealing with anything other than small amounts of data, can take awhile. select orderid ,REPLACE(( SELECT ' ' + CAST(ProductId as varchar) FROM _details d WHERE d.OrderId = o.OrderId ORDER BY d.OrderId,d.DetailId FOR XML PATH('') ),'&#x20;','') as Products from _orders o I've looked at pivot but most of the examples I have found are aggregating information. I just want to combine the child rows and tack them onto the parent. I should also point out I don't need to deal with the column names either since the output of the child rows will either be a fixed width string or a delimited string. For example, given the following tables: OrderId CustomerId ----------- ----------- 1 1 2 2 3 3 DetailId OrderId ProductId ----------- ----------- ----------- 1 1 100 2 1 158 3 1 234 4 2 125 5 3 101 6 3 105 7 3 212 8 3 250 for an order I need to output: orderid Products ----------- ----------------------- 1 100 158 234 2 125 3 101 105 212 250 or orderid Products ----------- ----------------------- 1 100|158|234 2 125 3 101|105|212|250 Thoughts or suggestions? I am using SQL Server 2k5. Example Setup: create table _orders ( OrderId int identity(1,1) primary key nonclustered ,CustomerId int ) create table _details ( DetailId int identity(1,1) primary key nonclustered ,OrderId int ,ProductId int ) insert into _orders (CustomerId) select 1 union select 2 union select 3 insert into _details (OrderId,ProductId) select 1,100 union select 1,158 union select 1,234 union select 2,125 union select 3,105 union select 3,101 union select 3,212 union select 3,250 using FOR XML PATH: select orderid ,REPLACE(( SELECT ' ' + CAST(ProductId as varchar) FROM _details d WHERE d.OrderId = o.OrderId ORDER BY d.OrderId,d.DetailId FOR XML PATH('') ),'&#x20;','') as Products from _orders o which outputs what I want, however is very slow for large amounts of data. One of the child tables is over 2 million rows, pushing the processing time out to ~ 4 hours. orderid Products ----------- ----------------------- 1 100 158 234 2 125 3 101 105 212 250

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• Setting Connection Parameters via ADO for SQL Server

  - by taspeotis

  Is it possible to set a connection parameter on a connection to SQL Server and have that variable persist throughout the life of the connection? The parameter must be usable by subsequent queries. We have some old Access reports that use a handful of VBScript functions in the SQL queries (let's call them GetStartDate and GetEndDate) that return global variables. Our application would set these before invoking the query and then the queries can return information between date ranges specified in our application. We are looking at changing to a ReportViewer control running in local mode, but I don't see any convenient way to use these custom functions in straight T-SQL. I have two concept solutions (not tested yet), but I would like to know if there is a better way. Below is some pseudo code. Set all variables before running Recordset.OpenForward Connection->Execute("SET @GetStartDate = ..."); Connection->Execute("SET @GetEndDate = ..."); // Repeat for all parameters Will these variables persist to later calls of Recordset->OpenForward? Can anything reset the variables aside from another SET/SELECT @variable statement? Create an ADOCommand "factory" that automatically adds parameters to each ADOCommand object I will use to execute SQL // Command has been previously been created ADOParameter *Parameter1 = Command->CreateParameter("GetStartDate"); ADOParameter *Parameter2 = Command->CreateParameter("GetEndDate"); // Set values and attach etc... What I would like to know if there is something like: Connection->SetParameter("GetStartDate", "20090101"); Connection->SetParameter("GetEndDate", 20100101"); And these will persist for the lifetime of the connection, and the SQL can do something like @GetStartDate to access them. This may be exactly solution #1, if the variables persist throughout the lifetime of the connection.

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• mysql subselect alternative

  - by Arnold

  Hi, Lets say I am analyzing how high school sports records affect school attendance. So I have a table in which each row corresponds to a high school basketball game. Each game has an away team id and a home team id (FK to another "team table") and a home score and an away score and a date. I am writing a query that matches attendance with this seasons basketball games. My sample output will be (#_students_missed_class, day_of_game, home_team, away_team, home_team_wins_this_season, away_team_wins_this_season) I now want to add how each team did the previous season to my analysis. Well, I have their previous season stored in the game table but i should be able to accomplish that with a subselect. So in my main select statement I add the subselect: SELECT COUNT(*) FROM game_table WHERE game_table.date BETWEEN 'start of previous season' AND 'end of previous season' AND ( (game_table.home_team = team_table.id AND game_table.home_score > game_table.away_score) OR (game_table.away_team = team_table.id AND game_table.away_score > game_table.home_score)) In this case team-table.id refers to the id of the home_team so I now have all their wins calculated from the previous year. This method of calculation is neither time nor resource intensive. The Explain SQL shows that I have ALL in the Type field and I am not using a Key and the query times out. I'm not sure how I can accomplish a more efficient query with a subselect. It seems proposterously inefficient to have to write 4 of these queries (for home wins, home losses, away wins, away losses). I am sure this could be more lucid. I'll absolutely add color tomorrow if anyone has questions

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• RegularExpression-esque search matching Objects in List

  - by Pindatjuh

  I'm currently working on an implementation of the following idea, and I was wondering if there is any literature on this subject. Working with Java, but the principle applies on any language with a decent type-system, I like to implement: matching Objects from a List using a RegularExpression-esque search: So let's say I have a List containing List<Object> x = new ArrayList<Object>(); x.add(new Object()); x.add("Hello World"); x.add("Second String"); x.add(5); // Integer (auto-boxing) x.add(6); // Integer Then I create a "Regular Expression" (not working with a stream of characters, but working with a stream of Objects), and instead of character-classes, I use type-system properties: [String][Integer] And this would match one sublist: {Match["Second String", 5]}. The expression: [String:length()<15] Will match two sublist (each of length 1) containing a String which instance is passing the expression instance.length() < 5: {Match["Hello World"],Match["Second String"]}. [Object][Object] Matches any pair in the List: {Match[Object,"Hello World"],Match["Second String", 5]}, in a streamed manner (no overlapping matches). Ofcourse, my implementation will have grouping, lookahead/lookbehinds and is hierarchical (i.e. matching n elements from Lists in Lists), etc. The above merely illustrates the concept. Is there a name for this principle, and is there literature available on it?

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