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  • Postgesql select from 2 tables. Joins?

    - by Daniel
    I have 2 tables that look like this: Table "public.phone_lists" Column | Type | Modifiers ----------+-------------------+-------------------------------------------------------------------- id | integer | not null default nextval(('"phone_lists_id_seq"'::text)::regclass) list_id | integer | not null sequence | integer | not null phone | character varying | name | character varying | and Table "public.email_lists" Column | Type | Modifiers ---------+-------------------+-------------------------------------------------------------------- id | integer | not null default nextval(('"email_lists_id_seq"'::text)::regclass) list_id | integer | not null email | character varying | I'm trying to get the list_id, phone, and emails out of the tables in one table. I'm looking for an output like: list_id | phone | email ---------+-------------+-------------------------------- 0 | | [email protected] 0 | | [email protected] 0 | | [email protected] 0 | | [email protected] 0 | | [email protected] 1 | 15555555555 | 1 | 15555551806 | 1 | 15555555508 | 1 | 15055555506 | 1 | 15055555558 | 1 | | [email protected] 1 | | [email protected] I've come up with select pl.list_id, pl.phone, el.email from phone_lists as pl left join email_lists as el using (list_id); but thats not quite right. Any suggestions?

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  • Generics Type issue

    - by JohnJohnGa
    ArrayList<Integer> arrI = new ArrayList<Integer>(); ArrayList arrO = arrI; // Warning /* It is ok to add a String as it is an ArrayList of Objects but the JVM will know the real type, arrO is an arrayList of Integer... */ arrO.add("Hello"); /* How I can get a String in an ArrayList<Integer> ?? Even if the compiler told me that I will get an Integer! */ System.out.println(arrI.get(0)); Anybody can explain what's happening here?

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  • How do I resolve this scope issue in VB .NET?

    - by froadie
    I have a code structure something like this: For row = 1 To numRows Dim arrayIndex As Integer = 0 For column As Integer = bucketStartColumn To bucketEndColumn ' whatever code arrayIndex = arrayIndex + 1 Next Next Dim arrayIndex As Integer = 0 For column As Integer = bucketStartColumn To bucketEndColumn ' whatever code arrayIndex = arrayIndex + 1 Next Not exactly the code, so I don't really need suggestions about refactoring, but my problem is this - with this code I get a compiler error for the first Dim arrayIndex As Integer = 0 - "Variable 'arrayIndex' hides a variable in an enclosing block." As far as I can tell, arrayIndex is local to the first for loop and shouldn't exist by the time we reach the second loop. If I try to change the second declaration of arrayIndex to arrayIndex = 0, I get the error "Name 'arrayIndex' is not declared", as I expected. So is it visible, or not? Does this have something to do with the Dim keyword? Any suggestions of how to get around this, other than naming the second index variable something else?

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  • Dynamic binding in C++

    - by chmike
    I'm implementing a CORBA like server. Each class has remotely callable methods and a dispatch method with two possible input, a string identifying the method or an integer which would be the index of the method in a table. A mapping of the string to the corresponding integer would be implemented by a map. The caller would send the string on the first call and get back the integer with the response so that it simply has to send the integer on subsequent calls. It is just a small optimization. The integer may be assigned dynamically on demand by the server object. The server class may be derived from another class with overridden virtual methods. What could be a simple and general way to define the method binding and the dispatch method ?

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  • Setting a property in XAML for a User Control

    - by Ben
    Hi, I have a user control that has a property of type Integer, that i am trying to set in the XAML Template to be that of a property within the bindingsource. If I set the property using a hard coded integer i.e. <MyControl MyIntegerProperty="3" /> This works fine, but if i try <MyControl MyIntegerProperty="{Binding MyDataContextIntegerProperty}" /> it fails. I know that the integer property on MyDataContext is returning a valid integer, and i know that this format works, as directly above this in the template, i have the line <TextBlock Text="{Binding MyDataContextStringProperty}" /> which works correctly. Is there any flag that i need to set on my User Controls Integer property to allow this to work? Or am i doing something else wrong? Thanks

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  • Rails has_one vs belongs_to semantics

    - by Anurag
    I have a model representing a Content item that contains some images. The number of images are fixed as these image references are very specific to the content. For example, the Content model refers to the Image model twice (profile image, and background image). I am trying to avoid a generic has_many, and sticking to multiple has_one's. The current database structure looks like: contents - id:integer - integer:profile_image_id - integer:background_image_id images - integer:id - string:filename - integer:content_id I just can't figure out how to setup the associations correctly here. The Content model could contain two belongs_to references to an Image, but that doesn't seem semantically right cause ideally an image belongs to the content, or in other words, the content has two images. This is the best I could think of (by breaking the semantics): class Content belongs_to :profile_image, :class_name => 'Image', :foreign_key => 'profile_image_id' belongs_to :background_image, :class_name => 'Image', :foreign_key => 'background_image_id' end Am I way off, and there a better way to achieve this association?

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  • Why does the right-shift operator produce a zero instead of a one?

    - by mrt181
    Hi, i am teaching myself java and i work through the exercises in Thinking in Java. On page 116, exercise 11, you should right-shift an integer through all its binary positions and display each position with Integer.toBinaryString. public static void main(String[] args) { int i = 8; System.out.println(Integer.toBinaryString(i)); int maxIterations = Integer.toBinaryString(i).length(); int j; for (j = 1; j < maxIterations; j++) { i >>= 1; System.out.println(Integer.toBinaryString(i)); } In the solution guide the output looks like this: 1000 1100 1110 1111 When i run this code i get this: 1000 100 10 1 What is going on here. Are the digits cut off? I am using jdk1.6.0_20 64bit. The book uses jdk1.5 32bit.

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  • Is there a good (standalone) PHPDoc parser class or function in PHP?

    - by Kris
    Hi folks, I'm looking for some method of converting a PHP Docblock (as used for generating documentation by tools like Doxygen) into a structure I can inspect in PHP. For example, I want to parse the following lines: /** * Multiply two values * @CHECKME * * @author someone * @created eons ago * * @param integer $x * @param integer $x * * @return integer */ function multiply($x, $y) { return $x * $y; } Into something similar to: array( 'author' = 'someone' ,'created' = 'eons ago' ,'param' = array( 'integer $x' ,'integer $y' ) ,'_flags' = array( '@CHECKME' ) ); I explicitly cannot use PEAR or any such library, it has to be relatively standalone. Any given solution that is better than using a bunch of regexes after stripping away comment outline would be awesome.

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  • create a model in create action from a class

    - by Pontek
    As a newbie to rails I can't find how to solve my issue ^^ I want to create a VideoPost from a form with a text field containing a video url (like youtube) I'm getting information on the video thanks to the gem https://github.com/thibaudgg/video_info And I want to save thoses information using a model of mine (VideoInformation). But I don't know how the create process should work. Thanks for any help ! I'm trying to create a VideoPost in VideoPostsController like this : def create video_info = VideoInfo.new(params[:video_url]) video_information = VideoInformation.create(video_info) #undefined method `stringify_keys' for #<Youtube:0x00000006a24120> if video_information.save @video_post = current_user.video_posts.build(video_information) end end My VideoPost model : # Table name: video_posts # # id :integer not null, primary key # user_id :integer # video_information_id :integer # created_at :datetime not null # updated_at :datetime not null My VideoInformation model (which got same attributes name than VideoInfo gem) : # Table name: video_informations # # id :integer not null, primary key # title :string(255) # description :text # keywords :text # duration :integer # video_url :string(255) # thumbnail_small :string(255) # thumbnail_large :string(255) # created_at :datetime not null # updated_at :datetime not null

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  • Rails 3: Create an instance with 3 foreign keys.

    - by donald
    Hello, Having a reviews table: # Table name: reviews # # id :integer not null, primary key # wsp_id :integer # service_id :integer # user_id :integer # description :text # rating :integer # created_at :datetime # updated_at :datetime # belongs_to :wsp belongs_to :service belongs_to :user How can I create a review for a service and pass the wsp_id and user_id? Do I need to use nested routes? I am able to do @user.reviews.new(params[:review]) but I'm not being able of passing the wsp_id and the service_id. Here's my Reviews create controller. def create @review = current_user.reviews.new(params[:review]) if @review.save #Saved else #Error, not saved end end What am I doing wrong? Thank you!

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  • Efficient implementation of exclusive execution

    - by n0weak
    I have an ObjectManager class that is used to process payments. It is wrapped over the Order entities, so new instance has to be created when processing is required. I need to prevent the situation when several ObjectManager instances are dealing with the same order simultaneously (it happend once because of some errors on the remote payment processing center, somehow they called our callback urls twice). I'd love to get an advice how to implement it more efficiently. For now, I am thinking about something like that: public class OrderManager{ private static final CopyOnWriteArrayList<Integer> LOCKER = new CopyOnWriteArrayList<Integer>(); private static synchronized boolean tryLock(Integer key) { return LOCKER.addIfAbsent(key); } private static void releaseLock(Integer key) { LOCKER.remove(key); } public void processPayment(Integer orderId) throws Exception{ if (!tryLock(orderId)) { return; } try { //operate } finally { releaseLock(orderId); } } //remainder omitted }

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  • How to make Delphi Prism indexed properties visible to C# when properties are not default

    - by Arcturus
    I have several Delphi Prism classes with indexed properties that I use a lot on my C# web applications (we are migrating a big Delphi Win32 system to ASP.Net). My problem is that it seems that C# can't see the indexed properties if they aren't the default properties of their classes. Maybe I'm doing something wrong, but I'm completely lost. I know that this question looks a lot like a bug report, but I need to know if someone else knows how to solve this before I report a bug. If I have a class like this: TMyClass = public class private ... method get_IndexedBool(index: Integer): boolean; method set_IndexedBool(index: Integer; value: boolean); public property IndexedBool[index: Integer]: boolean read get_IndexedBool write set_IndexedBool; default; // make IndexedBool the default property end; I can use this class in C# like this: var myObj = new TMyClass(); myObj[0] = true; However, if TMyClass is defined like this: TMyClass = public class private ... method get_IndexedBool(index: Integer): boolean; method set_IndexedBool(index: Integer; value: boolean); public property IndexedBool[index: Integer]: boolean read get_IndexedBool write set_IndexedBool; // IndexedBool is not the default property anymore end; Then the IndexedBool property becomes invisible in C#. The only way I can use it is doing this: var myObj = new TMyClass(); myObj.set_IndexedBool(0, true); I don't know if I'm missing something, but I can't see the IndexedBool property if I remove the default in the property declaration. Besides that, I'm pretty sure that it is wrong to have direct access to a private method of a class instance. Any ideas?

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  • Mapping parent-child relationships with iBatis

    - by agnul
    I have the classic setup public class Parent { Integer id; ... // No generics Collection someCollectionAttribute; ... public void setChildren(Collection c) { ... } } public class Child { Integer id; ... } and I'm trying to map this on the usual table setup using iBatis (version 2.30... don't ask). create table parents ( ID integer primary key ... ) create table children ( ID integer primary key PARENT_ID integer references parents(id) ... ) My mapping file looks like this <resultMap id="ParentResult" groupBy="id"> <result property="id" column="ID" /> ... <result property="children" resultMap="ChildResult" /> </resultMap> <resultMap id="ChildResult"> <result property="id" column="ID" /> <result property="parentId" column="PARENT_ID" /> ... </result> <sql id="loadParent" resultMap="ParentResult"> select P.ID as p1, ..., C.ID as c1, C.PARENT_ID as c2 ... from parents P join children C on (P.ID = C.PARENT_ID) where P.ID = #id# order by P.ID </sql> Doing the usual sqlMap.queryForObject("loadParent", new Integer(42)) at first caused a NullPointerException inside the setChildren setter which apparently is called with a null argument (my bad). Fixing the setter everything works fine, but the logs show that setChildren is called only once before even running a single SQL statement, still with a null argument, so I'm wondering what's going on here. Anyone has any clues?

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  • Simple Android Binary Text Clock

    - by Hristo
    Hello, I want to create a simple android binary clock but my application crashes. I use 6 textview fields: 3 for the decimal and 3 for the binary representation of the current time (HH:mm:ss). Here's the code: import java.text.SimpleDateFormat; import java.util.Calendar; import android.app.Activity; import android.os.Bundle; import android.widget.TextView; public class Binary extends Activity implements Runnable { Thread runner; /** Called when the activity is first created. */ @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); if (runner == null) { //start the song runner = new Thread(this); runner.start(); } } @Override public void run() { TextView hours_dec = (TextView) findViewById(R.id.hours_dec); TextView mins_dec = (TextView) findViewById(R.id.mins_dec); TextView secs_dec = (TextView) findViewById(R.id.secs_dec); TextView hours_bin = (TextView) findViewById(R.id.hours_bin); TextView mins_bin = (TextView) findViewById(R.id.mins_bin); TextView secs_bin = (TextView) findViewById(R.id.secs_bin); SimpleDateFormat hours_sdf = new SimpleDateFormat("HH"); SimpleDateFormat mins_sdf = new SimpleDateFormat("mm"); SimpleDateFormat secs_sdf = new SimpleDateFormat("ss"); Calendar cal = Calendar.getInstance(); while (runner != null) { WaitAMoment(); cal.getTime(); hours_dec.setText(hours_sdf.format(cal.getTime())); mins_dec.setText(mins_sdf.format(cal.getTime())); secs_dec.setText(secs_sdf.format(cal.getTime())); hours_bin.setText(String.valueOf(Integer.toBinaryString(Integer.parseInt((String) hours_dec.getText())))); mins_bin.setText(String.valueOf(Integer.toBinaryString(Integer.parseInt((String) mins_dec.getText())))); secs_bin.setText(String.valueOf(Integer.toBinaryString(Integer.parseInt((String) secs_dec.getText())))); } } protected void WaitAMoment() { try { Thread.sleep(100); } catch (InterruptedException e) { }; } }`

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  • Visual Studio Macros on 64 bit fail with COM error

    - by bruce.kinchin
    I'm doing some javascript development and found a cool macro to region my code ("Using #region Directive With JavaScript Files in Visual Studio"). I used this on my 32 bit box, and it worked first time. (Visual Studio 2008 SP1, Win7) For easy of reference the macro is: Option Strict Off Option Explicit Off Imports System Imports EnvDTE Imports EnvDTE80 Imports System.Diagnostics Imports System.Collections Public Module JsMacros Sub OutlineRegions() Dim selection As EnvDTE.TextSelection = DTE.ActiveDocument.Selection Const REGION_START As String = "//#region" Const REGION_END As String = "//#endregion" DTE.ExecuteCommand("Edit.StopOutlining") selection.SelectAll() Dim text As String = selection.Text selection.StartOfDocument(True) Dim startIndex As Integer Dim endIndex As Integer Dim lastIndex As Integer = 0 Dim startRegions As Stack = New Stack() Do startIndex = text.IndexOf(REGION_START, lastIndex) endIndex = text.IndexOf(REGION_END, lastIndex) If startIndex = -1 AndAlso endIndex = -1 Then Exit Do End If If startIndex <> -1 AndAlso startIndex < endIndex Then startRegions.Push(startIndex) lastIndex = startIndex + 1 Else ' Outline region ... selection.MoveToLineAndOffset(CalcLineNumber(text, CInt(startRegions.Pop())), text.Length) selection.MoveToLineAndOffset(CalcLineNumber(text, endIndex) + 1, 1, True) selection.OutlineSection() lastIndex = endIndex + 1 End If Loop selection.StartOfDocument() End Sub Private Function CalcLineNumber(ByVal text As String, ByVal index As Integer) Dim lineNumber As Integer = 1 Dim i As Integer = 0 While i < index If text.Chars(i) = vbCr Then lineNumber += 1 i += 1 End If i += 1 End While Return lineNumber End Function End Module I then tried to use the same macro on two separate 64 bit machines (Win7 x64), identical other than the 64 bit OS version and it fails to work. Stepping through it with the Visual Studio Macros IDE, it fails the first time on the DTE.ExecuteCommand("Edit.StopOutlining") line with a COM error (Error HRESULT E_FAIL has been returned from a call to a COM component). If I attempt to run it a second time, I can run it from the Macro Editor with no issue, but not from within Visual Studio with the macro explorer 'run macro' command. I have reviewed the following articles without finding anything helpful: Stackoverflow: Visual Studio 2008 macro only works from the Macro IDE, not the Macro Explorer Recorded macro does not run; Failing on DTE.ExecuteCommand Am I missing something dumb?

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  • Recursively adding threads to a Java thread pool

    - by Leith
    I am working on a tutorial for my Java concurrency course. The objective is to use thread pools to compute prime numbers in parallel. The design is based on the Sieve of Eratosthenes. It has an array of n bools, where n is the largest integer you are checking, and each element in the array represents one integer. True is prime, false is non prime, and the array is initially all true. A thread pool is used with a fixed number of threads (we are supposed to experiment with the number of threads in the pool and observe the performance). A thread is given a integer multiple to process. The thread then finds the first true element in the array that is not a multiple of thread's integer. The thread then creates a new thread on the thread pool which is given the found number. After a new thread is formed, the existing thread then continues to set all multiples of it's integer in the array to false. The main program thread starts the first thread with the integer '2', and then waits for all spawned threads to finish. It then spits out the prime numbers and the time taken to compute. The issue I have is that the more threads there are in the thread pool, the slower it takes with 1 thread being the fastest. It should be getting faster not slower! All the stuff on the internet about Java thread pools create n worker threads the main thread then wait for all threads to finish. The method I use is recursive as a worker can spawn more worker threads. I would like to know what is going wrong, and if Java thread pools can be used recursively.

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  • VB.NET - Removing a number from a random number generator

    - by Alex
    I am trying to create a lottery simulator. The lottery has 6 numbers, the number generated must be between 1 - 49 and cannot be in the next number generated. I have tried using the OR function but I'm not entirely sure if I am using it properly. Any help would be great. Thanks. Public Class Form1 Private Sub cmdRun_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cmdRun.Click 'Creates a new Random class in VB.NET Dim RandomClass As New Random() '#################################### Dim RandomNumber1 As Integer RandomNumber1 = RandomClass.Next(1, 49) 'Displays first number generated txtFirst.Text = (RandomNumber1) '#################################### Dim RandomNumber2 As Integer RandomNumber2 = RandomClass.Next(1, 49) If RandomNumber2 = RandomNumber1 Then RandomNumber2 = RandomClass.Next(1, 49) End If 'Displays second number generated txtSecond.Text = (RandomNumber2) '#################################### Dim RandomNumber3 As Integer RandomNumber3 = RandomClass.Next(1, 49) If RandomNumber3 = RandomNumber2 Or RandomNumber2 Then RandomNumber3 = RandomClass.Next(1, 49) End If 'Displays third number generated txtThird.Text = (RandomNumber3) '#################################### Dim RandomNumber4 As Integer RandomNumber4 = RandomClass.Next(1, 49) If RandomNumber4 = RandomNumber3 Or RandomNumber2 Or RandomNumber1 Then RandomNumber4 = RandomClass.Next(1, 49) End If 'Displays fourth number generated txtFourth.Text = (RandomNumber4) '#################################### Dim RandomNumber5 As Integer RandomNumber5 = RandomClass.Next(1, 49) If RandomNumber5 = RandomNumber4 Or RandomNumber3 Or RandomNumber2 Or RandomNumber1 Then RandomNumber5 = RandomClass.Next(1, 49) End If 'Displays fifth number generated txtFifth.Text = (RandomNumber5) '#################################### Dim RandomNumber6 As Integer RandomNumber6 = RandomClass.Next(1, 49) If RandomNumber6 = RandomNumber5, RandomNumber4, RandomNumber3, RandomNumber2, RandomNumber1 Then RandomNumber6 = RandomClass.Next(1, 49) End If 'Displays sixth number generated txtSixth.Text = (RandomNumber6) End Sub

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  • Active Record two belongs_to calls or single table inheritance

    - by ethyreal
    In linking a sports event to two teams, at first this seemed to make sense: events - id:integer - integer:home_team_id - integer:away_team_id teams - integer:id - string:name However I am troubled by how I would link that up in the active record model: class Event belongs_to :home_team, :class_name => 'Team', :foreign_key => "home_team_id" belongs_to :away_team, :class_name => 'Team', :foreign_key => "away_team_id" end Is that the best solution? In an answer to a similar question I was pointed to single table inheritance, and then later found polymorphic associations. Neither of which seemed to fit this association. Perhaps I am looking at this wrong, but I see no need to subclass a team into home and away teams since the distinction is only in where the game is played. If I did go with single table inheritance I wouldn't want each team to belong_to an event so would this work? # app/models/event.rb class Event < ActiveRecord::Base belongs_to :home_team belongs_to :away_team end # app/models/team.rb class Team < ActiveRecord::Base has_many :teams end # app/models/home_team.rb class HomeTeam < Team end # app/models/away_team.rb class AwayTeam < Team end I thought also about a has_many through association but that seems two much as I will only ever need two teams, but those two teams don't belong to any one event. event_teams - integer:event_id - integer:team_id - boolean:is_home Is there a cleaner more semantic way for making these associations in active record? or is one of these solutions the best choice? Thanks

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  • Invert linear linked list

    - by ArtWorkAD
    Hi, a linear linked list is a set of nodes. This is how a node is defined (to keep it easy we do not distinguish between node an list): class Node{ Object data; Node link; public Node(Object pData, Node pLink){ this.data = pData; this.link = pLink; } public String toString(){ if(this.link != null){ return this.data.toString() + this.link.toString(); }else{ return this.data.toString() ; } } public void inc(){ this.data = new Integer((Integer)this.data + 1); } public void lappend(Node list){ Node child = this.link; while(child != null){ child = child.link; } child.link = list; } public Node copy(){ if(this.link != null){ return new Node(new Integer((Integer)this.data), this.link.copy()); }else{ return new Node(new Integer((Integer)this.data), null); } } public Node invert(){ Node child = this.link; while(child != null){ child = child.link; } child.link = this;.... } } I am able to make a deep copy of the list. Now I want to invert the list so that the first node is the last and the last the first. The inverted list has to be a deep copy. I started developing the invert function but I am not sure. Any Ideas? Update: Maybe there is a recursive way since the linear linked list is a recursive data structure. I would take the first element, iterate through the list until I get to a node that has no child and append the first element, I would repeat this for the second, third....

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  • sqlalchemy relation through another (declarative)

    - by clayg
    Is anyone familiar with ActiveRecord's "has_many :through" relations for models? I'm not really a Rails guy, but that's basically what I'm trying to do. As a contrived example consider Projects, Programmers, and Assignments: from sqlalchemy import create_engine from sqlalchemy.orm import sessionmaker from sqlalchemy import Column, ForeignKey from sqlalchemy.types import Integer, String, Text from sqlalchemy.orm import relation from sqlalchemy.ext.declarative import declarative_base Base = declarative_base() class Assignment(Base): __tablename__ = 'assignment' id = Column(Integer, primary_key=True) description = Column(Text) programmer_id = Column(Integer, ForeignKey('programmer.id')) project_id = Column(Integer, ForeignKey('project.id')) def __init__(self, description=description): self.description = description def __repr__(self): return '<Assignment("%s")>' % self.description class Programmer(Base): __tablename__ = 'programmer' id = Column(Integer, primary_key=True) name = Column(String(64)) assignments = relation("Assignment", backref='programmer') def __init__(self, name=name): self.name = name def __repr__(self): return '<Programmer("%s")>' % self.name class Project(Base): __tablename__ = 'project' id = Column(Integer, primary_key=True) name = Column(String(64)) description = Column(Text) assignments = relation("Assignment", backref='project') def __init__(self, name=name, description=description): self.name = name self.description = description def __repr__(self): return '<Project("%s", "%s...")>' % (self.name, self.description[:10]) engine = create_engine('sqlite://') Base.metadata.create_all(engine) Session = sessionmaker(bind=engine) session = Session() Projects have many Assignments. Programmers have many Assignments. (understatement?) But in my office at least, Programmers also have many Projects - I'd like this relationship to be inferred through the Assignments assigned to the Programmer. I'd like the Programmer model to have a attribute "projects" which will return a list of Projects associated to the Programmer through the Assignment model. me = session.query(Programmer).filter_by(name='clay').one() projects = session.query(Project).\ join(Project.assignments).\ join(Assignment.programmer).\ filter(Programmer.id==me.id).all() How can I describe this relationship clearly and simply using the sqlalchemy declarative syntax? Thanks!

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  • Can't return a List from a Compiled Query.

    - by Andrew
    I was speeding up my app by using compiled queries for queries which were getting hit over and over. I tried to implement it like this: Function Select(ByVal fk_id As Integer) As List(SomeEntity) Using db As New DataContext() db.ObjectTrackingEnabled = False Return CompiledSelect(db, fk_id) End Using End Function Shared CompiledSelect As Func(Of DataContext, Integer, List(Of SomeEntity)) = _ CompiledQuery.Compile(Function(db As DataContext, fk_id As Integer) _ (From u In db.SomeEntities _ Where u.SomeLinkedEntity.ID = fk_id _ Select u).ToList()) This did not work and I got this error message: Type : System.ArgumentNullException, mscorlib, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089 Message : Value cannot be null. Parameter name: value However, when I changed my compiled query to return IQueryable instead of List like so: Function Select(ByVal fk_id As Integer) As List(SomeEntity) Using db As New DataContext() db.ObjectTrackingEnabled = False Return CompiledSelect(db, fk_id).ToList() End Using End Function Shared CompiledSelect As Func(Of DataContext, Integer, IQueryable(Of SomeEntity)) = _ CompiledQuery.Compile(Function(db As DataContext, fk_id As Integer) _ From u In db.SomeEntities _ Where u.SomeLinkedEntity.ID = fk_id _ Select u) It worked fine. Can anyone shed any light as to why this is? BTW, compiled queries rock! They sped up my app by a factor of 2.

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  • To have efficient many-to-many relation in Java

    - by Masi
    How can you make the efficient many-to-many -relation from fileID to Words and from word to fileIDs without database -tools like Postgres in Java? I have the following classes. The relation from fileID to words is cheap, but not the reverse, since I need three for -loops for it. My solution is not apparently efficient. Other options may be to create an extra class that have word as an ID with the ArrayList of fileIDs. Reply to JacobM's answer The relevant part of MyFile's constructors is: /** * Synopsis of data in wordToWordConutInFile.txt: * fileID|wordID|wordCount * * Synopsis of the data in the file wordToWordID.txt: * word|wordID **/ /** * Getting words by getting first wordIDs from wordToWordCountInFile.txt and then words in wordToWordID.txt. */ InputStream in2 = new FileInputStream("/home/dev/wordToWordCountInFile.txt"); BufferedReader fi2 = new BufferedReader(new InputStreamReader(in2)); ArrayList<Integer> wordIDs = new ArrayList<Integer>(); String line = null; while ((line = fi2.readLine()) != null) { if ((new Integer(line.split("|")[0]) == currentFileID)) { wordIDs.add(new Integer(line.split("|")[6])); } } in2.close(); // Getting now the words by wordIDs. InputStream in3 = new FileInputStream("/home/dev/wordToWordID.txt"); BufferedReader fi3 = new BufferedReader(new InputStreamReader(in3)); line = null; while ((line = fi3.readLine()) != null) { for (Integer wordID : wordIDs) { if (wordID == (new Integer(line.split("|")[1]))) { this.words.add(new Word(new String(line.split("|")[0]), fileID)); break; } } } in3.close(); this.words.addAll(words); The constructor of Word is at the paste.

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  • TreeMap sort by value

    - by vito huang
    I'm new to java, i want to write an comparator to that will let me sort TreeMap by value instead of the default natural sorting. i tried something like this, but can't find out what went wrong: import java.util.*; class treeMap { public static void main(String[] args) { System.out.println("the main"); byValue cmp = new byValue(); Map<String, Integer> map = new TreeMap<String, Integer>(cmp); map.put("de",10); map.put("ab", 20); map.put("a",5); for (Map.Entry<String,Integer> pair: map.entrySet()) { System.out.println(pair.getKey()+":"+pair.getValue()); } } } class byValue implements Comparator<Map.Entry<String,Integer>> { public int compare(Map.Entry<String,Integer> e1, Map.Entry<String,Integer> e2) { if (e1.getValue() < e2.getValue()){ return 1; } else if (e1.getValue() == e2.getValue()) { return 0; } else { return -1; } } } I guess what am i asking is what controls what get pass to comparator function, can i get an Map.Entry pass to comparator?

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  • Active Record two belongs_to calls to the same model

    - by ethyreal
    In linking a sports event to two teams, at first this seemed to make since: events - id:integer - integer:home_team_id - integer:away_team_id teams - integer:id - string:name However I am troubled by how I would link that up in the active record model: class Event belongs_to :home_team, :class_name => 'Team', :foreign_key => "home_team_id" belongs_to :away_team, :class_name => 'Team', :foreign_key => "away_team_id" end Is that the best solution? In an answer to a similar question I was pointed to single table inheritance, and then later found polymorphic associations. Neither of which seemed to fit this association. Perhaps I am looking at this wrong, but I see no need to subclass a team into home and away teams since the distinction is only in where the game is played. I thought also about a has_many through association but that seems two much as I will only ever need two teams, but those two teams don't belong to any one event. event_teams - integer:event_id - integer:team_id - boolean:is_home Is there a cleaner more semantic way for making these associations in active record? Thanks

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  • Filling a byte array in Java

    - by Corleone
    Hey all! For part of a project I'm working on I am implementing a RTPpacket where I have to fill the header array of byte with RTP header fields. //size of the RTP header: static int HEADER_SIZE = 12; // bytes //Fields that compose the RTP header public int Version; // 2 bits public int Padding; // 1 bit public int Extension; // 1 bit public int CC; // 4 bits public int Marker; // 1 bit public int PayloadType; // 7 bits public int SequenceNumber; // 16 bits public int TimeStamp; // 32 bits public int Ssrc; // 32 bits //Bitstream of the RTP header public byte[] header = new byte[ HEADER_SIZE ]; This was my approach: /* * bits 0-1: Version * bit 2: Padding * bit 3: Extension * bits 4-7: CC */ header[0] = new Integer( (Version << 6)|(Padding << 5)|(Extension << 6)|CC ).byteValue(); /* * bit 0: Marker * bits 1-7: PayloadType */ header[1] = new Integer( (Marker << 7)|PayloadType ).byteValue(); /* SequenceNumber takes 2 bytes = 16 bits */ header[2] = new Integer( SequenceNumber >> 8 ).byteValue(); header[3] = new Integer( SequenceNumber ).byteValue(); /* TimeStamp takes 4 bytes = 32 bits */ for ( int i = 0; i < 4; i++ ) header[7-i] = new Integer( TimeStamp >> (8*i) ).byteValue(); /* Ssrc takes 4 bytes = 32 bits */ for ( int i = 0; i < 4; i++ ) header[11-i] = new Integer( Ssrc >> (8*i) ).byteValue(); Any other, maybe 'better' ways to do this?

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