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• Solving Diophantine Equations Using Python

  - by HARSHITH

  In mathematics, a Diophantine equation (named for Diophantus of Alexandria, a third century Greek mathematician) is a polynomial equation where the variables can only take on integer values. Although you may not realize it, you have seen Diophantine equations before: one of the most famous Diophantine equations is: We are not certain that McDonald's knows about Diophantine equations (actually we doubt that they do), but they use them! McDonald's sells Chicken McNuggets in packages of 6, 9 or 20 McNuggets. Thus, it is possible, for example, to buy exactly 15 McNuggets (with one package of 6 and a second package of 9), but it is not possible to buy exactly 16 nuggets, since no non- negative integer combination of 6's, 9's and 20's adds up to 16. To determine if it is possible to buy exactly n McNuggets, one has to solve a Diophantine equation: find non-negative integer values of a, b, and c, such that 6a + 9b + 20c = n. Write an iterative program that finds the largest number of McNuggets that cannot be bought in exact quantity. Your program should print the answer in the following format (where the correct number is provided in place of n): "Largest number of McNuggets that cannot be bought in exact quantity: n"

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• Subsonic : Can’t decide which property to consider the Key? foreign key issue.

  - by AJ

  Hi I am trying to select count of rows from a table which has foreign keys of two tables. The C# code threw the error mentioned below. So, I added a primary key column to the table (schema as follows) and regenerated the code. But still the same error is coming. Error : Can't decide which property to consider the Key - you can create one called 'ID' or mark one with SubSonicPrimaryKey attribute sqLite Table schema CREATE TABLE "AlbumDocuments" ("Id" INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL , "AlbumId" INTEGER NOT NULL CONSTRAINT fk_AlbumId REFERENCES Albums(Id) , "DocumentId" INTEGER NOT NULL CONSTRAINT fk_DocumentId REFERENCES Documents(Id)) C# code int selectAlbumDocumentsCount = new SubSonic.Query.Select() .From<DocSafeDB.DataLayer.AlbumDocumentsTable>() .Where(DocSafeDB.DataLayer.AlbumDocumentsTable.AlbumIdColumn).In(request.AlbumId) .Execute(); Not sure what I should be doing next as I can't do where against primary key because I don;t have that info. So my questions are: How do I select count of rows against foreign key column? Is primary key required in this scenario? I have several things but not sure why its not working. To me it looks like a very normal use case. Please advise. Thanks AJ

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• Rails model belongs to model that belongs to model but i want to use another name

  - by Micke

  Hello. This may be a stupid question but im just starting to learn Rail thats why i am asking thsi question. I have one model called "User" which handles all the users in my community. Now i want to add a guestbook to every user. So i created a model called "user_guestbook" and inserted this into the new model: belongs_to :user and this into the user model: has_one :user_guestbook, :as => :guestbook The next thing i did was to add a new model to handle the posts inside the guestbook. I named it "guestbook_posts" and added this code into the new model: belongs_to :user_guestbook And this into the user_guestbook model: has_many :guestbook_posts, :as => :posts What i wanted to achive was to be able to fetch all the posts to a certain user by: @user = User.find(1) puts @user.guestbook.posts But it doesnt work for me. I dont know what i am doing wrong and if there is any easier way to do this please tell me so. Just to note, i have created some migrations for it to as follows: create_user_guestbook: t.integer :user_id create_guestbook_posts: t.integer :guestbook_id t.integer :from_user t.string :post Thanks in advance!

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• Problem with cascade delete using Entity Framework and System.Data.SQLite

  - by jamone

  I have a SQLite DB that is set up so when I delete a Person the delete is cascaded. This works fine when I manually delete a Person (all records that reference the PersonID are deleted). But when I use Entity Framework to delete the Person I get an error: System.InvalidOperationException: The operation failed: The relationship could not be changed because one or more of the foreign-key properties is non-nullable. When a change is made to a relationship, the related foreign-key property is set to a null value. If the foreign-key does not support null values, a new relationship must be defined, the foreign-key property must be assigned another non-null value, or the unrelated object must be deleted. I don't understand why this is occurring. My trigger is set to clean up all related objects before deleting the object it was told to delete. When I go into the model editor and check the properties of the relationship it shows no action for the OnDelete property. Why isn't this set correctly by pulling it from the DB? If I change this value to Cascade everything works properly, but I would rather not rely on this manual change because what if I refresh my model from the DB and it looses that. Here's the relivent SQL for my tables. CREATE TABLE [SomeTable] ( [SomeTableID] INTEGER NOT NULL PRIMARY KEY AUTOINCREMENT, [PersonID] INTEGER NOT NULL REFERENCES [Person](PersonID) ON DELETE CASCADE ) CREATE TABLE [Person] ( [PersonID] INTEGER NOT NULL PRIMARY KEY AUTOINCREMENT )

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• Problem deleting record using Entity Framework and System.Data.SQLite

  - by jamone

  I have a SQLite DB that is set up so when I delete a Person the delete is cascaded. This works fine when I manually delete a Person (all records that reference the PersonID are deleted). But when I use Entity Framework to delete the Person I get an error: System.InvalidOperationException: The operation failed: The relationship could not be changed because one or more of the foreign-key properties is non-nullable. When a change is made to a relationship, the related foreign-key property is set to a null value. If the foreign-key does not support null values, a new relationship must be defined, the foreign-key property must be assigned another non-null value, or the unrelated object must be deleted. I don't understand why this is occurring. My trigger is set to clean up all related objects before deleting the object it was told to delete. When I go into the model editor and check the properties of the relationship it shows no action for the OnDelete property. Why isn't this set correctly by pulling it from the DB? Here's the relivent SQL for my tables. CREATE TABLE [SomeTable] ( [SomeTableID] INTEGER NOT NULL PRIMARY KEY AUTOINCREMENT, [PersonID] INTEGER NOT NULL REFERENCES [Person](PersonID) ON DELETE CASCADE ) CREATE TABLE [Person] ( [PersonID] INTEGER NOT NULL PRIMARY KEY AUTOINCREMENT )

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• Getting Error System.Runtime.InteropServices.COMException

  - by Savan Parmar

  Hey All, I am using Vb.Net to Create Labels in Microsoft. For that i am using below mantioend Code. Public Sub CreateLabel(ByVal StrFilter As String, ByVal Path As String) WordApp = CreateObject("Word.Application") ''Add a new document. WordDoc = WordApp.Documents.Add() Dim oConn As SqlConnection = New SqlConnection(connSTR) oConn.Open() Dim oCmd As SqlCommand Dim oDR As SqlDataReader oCmd = New SqlCommand(StrFilter, oConn) oDR = oCmd.ExecuteReader Dim intI As Integer Dim FilePath As String = "" With WordDoc.MailMerge With .Fields Do While oDR.Read For intI = 0 To oDR.FieldCount - 1 .Add(WordApp.Selection.Range, oDR.Item(intI)) Next Loop End With Dim objAutoText As Word.AutoTextEntry = WordApp.NormalTemplate.AutoTextEntries.Add("MyLabelLayout", WordDoc.Content) WordDoc.Content.Delete() .MainDocumentType = Word.WdMailMergeMainDocType.wdMailingLabels FilePath = CreateSource(StrFilter) .OpenDataSource(FilePath) Dim NewLabel As Word.CustomLabel = WordApp.MailingLabel.CustomLabels.Add("MyLabel", False) WordApp.MailingLabel.CreateNewDocument(Name:="MyLabel", Address:="", AutoText:="MyLabelLayout") objAutoText.Delete() .Destination = Word.WdMailMergeDestination.wdSendToNewDocument WordApp.Visible = True .Execute() End With oConn.Close() WordDoc.Close() End Sub Private Function CreateSource(ByVal StrFilter As String) As String Dim CnnUser As SqlConnection = New SqlConnection(connSTR) Dim sw As StreamWriter = File.CreateText("C:\Mail.Txt") Dim Path As String = "C:\Mail.Txt" Dim StrHeader As String = "" Try Dim SelectCMD As SqlCommand = New SqlCommand(StrFilter, CnnUser) Dim oDR As SqlDataReader Dim IntI As Integer SelectCMD.CommandType = CommandType.Text CnnUser.Open() oDR = SelectCMD.ExecuteReader For IntI = 0 To oDR.FieldCount - 1 StrHeader &= oDR.GetName(IntI) & " ," Next StrHeader = Mid(StrHeader, 1, Len(StrHeader) - 2) sw.WriteLine(StrHeader) sw.Flush() sw.Close() StrHeader = "" Do While oDR.Read For IntJ As Integer = 0 To oDR.FieldCount - 1 StrHeader &= oDR.GetString(IntJ) & " ," Next Loop StrHeader = Mid(StrHeader, 1, Len(StrHeader) - 2) sw = File.AppendText(Path) sw.WriteLine(StrHeader) CnnUser.Close() sw.Flush() sw.Close() Catch ex As Exception MessageBox.Show(ex.Message, "TempID", MessageBoxButtons.OK, MessageBoxIcon.Error) End Try Return Path End Function Now when i am running the programm i am getting this error.I tried hard but not able to locate what could be the problem the error is:- System.Runtime.InteropServices.COMException --Horizontal and vertical pitch must be greater than or equal to the label width and height, respectively. Even though i tried to set the Horizontal and vertical pitch programatically but it gives same err. Plz if any one can help

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• The file is damaged and could not be repaired

  - by acadia

  Hello Experts, I am trying to display a PDF file in my ASP.net page based on the binary data received from the ASP.net Web service. Below is the code. though I am getting the data from the Web Service for some reason, if I run the below mentioned code on page load I am getting the above mentioned error. Please help Response.Buffer = True Response.ContentType = "application/pdf" Response.AddHeader("Content-Disposition", "Inline") Dim ws As New imageGenService.Service1 Dim imagebyte As Byte() = Nothing imagebyte = ws.generateSamplePDF() If imagebyte IsNot Nothing Then '"attachment; filename=Whatever.pdf" Dim MemStream As New System.IO.MemoryStream Dim doc As New iTextSharp.text.Document Dim reader As iTextSharp.text.pdf.PdfReader Dim numberOfPages As Integer Dim currentPageNumber As Integer Dim writer As iTextSharp.text.pdf.PdfWriter = iTextSharp.text.pdf.PdfWriter.GetInstance(doc, MemStream) doc.Open() Dim cb As iTextSharp.text.pdf.PdfContentByte = writer.DirectContent Dim page As iTextSharp.text.pdf.PdfImportedPage Dim rotation As Integer reader = New iTextSharp.text.pdf.PdfReader(imagebyte) numberOfPages = reader.NumberOfPages currentPageNumber = 0 Do While (currentPageNumber < numberOfPages) currentPageNumber += 1 doc.SetPageSize(PageSize.LETTER) doc.NewPage() page = writer.GetImportedPage(reader, currentPageNumber) rotation = reader.GetPageRotation(currentPageNumber) If (rotation = 90) Or (rotation = 270) Then cb.AddTemplate(page, 0, -1.0F, 1.0F, 0, 0, reader.GetPageSizeWithRotation(currentPageNumber).Height) Else cb.AddTemplate(page, 1.0F, 0, 0, 1.0F, 0, 0) End If Loop If MemStream Is Nothing Then Response.Write("No Data is available for output") Else Response.BinaryWrite(MemStream.GetBuffer()) End If End If

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• sqlalchemy date type in 0.6 migration using mssql

  - by nosklo

  I'm connection to mssql server through pyodbc, via FreeTDS odbc driver, on linux ubuntu 10.04. Sqlalchemy 0.5 uses DATETIME for sqlalchemy.Date() fields. Now Sqlalchemy 0.6 uses DATE, but sql server 2000 doesn't have a DATE type. How can I make DATETIME be the default for sqlalchemy.Date() on sqlalchemy 0.6 mssql+pyodbc dialect? I'd like to keep it as clean as possible. Here's code to reproduce the issue: import sqlalchemy from sqlalchemy import Table, Column, MetaData, Date, Integer, create_engine engine = create_engine( 'mssql+pyodbc://sa:sa@myserver/mydb?driver=FreeTDS') m = MetaData(bind=engine) tb = sqlalchemy.Table('test_date', m, Column('id', Integer, primary_key=True), Column('dt', Date()) ) tb.create() And here is the traceback I'm getting: Traceback (most recent call last): File "/tmp/teste.py", line 15, in <module> tb.create() File "/home/nosklo/.local/lib/python2.6/site-packages/sqlalchemy/schema.py", line 428, in create bind.create(self, checkfirst=checkfirst) File "/home/nosklo/.local/lib/python2.6/site-packages/sqlalchemy/engine/base.py", line 1647, in create connection=connection, **kwargs) File "/home/nosklo/.local/lib/python2.6/site-packages/sqlalchemy/engine/base.py", line 1682, in _run_visitor **kwargs).traverse_single(element) File "/home/nosklo/.local/lib/python2.6/site-packages/sqlalchemy/sql/visitors.py", line 77, in traverse_single return meth(obj, **kw) File "/home/nosklo/.local/lib/python2.6/site-packages/sqlalchemy/engine/ddl.py", line 58, in visit_table self.connection.execute(schema.CreateTable(table)) File "/home/nosklo/.local/lib/python2.6/site-packages/sqlalchemy/engine/base.py", line 1157, in execute params) File "/home/nosklo/.local/lib/python2.6/site-packages/sqlalchemy/engine/base.py", line 1210, in _execute_ddl return self.__execute_context(context) File "/home/nosklo/.local/lib/python2.6/site-packages/sqlalchemy/engine/base.py", line 1268, in __execute_context context.parameters[0], context=context) File "/home/nosklo/.local/lib/python2.6/site-packages/sqlalchemy/engine/base.py", line 1367, in _cursor_execute context) File "/home/nosklo/.local/lib/python2.6/site-packages/sqlalchemy/engine/base.py", line 1360, in _cursor_execute context) File "/home/nosklo/.local/lib/python2.6/site-packages/sqlalchemy/engine/default.py", line 277, in do_execute cursor.execute(statement, parameters) sqlalchemy.exc.ProgrammingError: (ProgrammingError) ('42000', '[42000] [FreeTDS][SQL Server]Column or parameter #2: Cannot find data type DATE. (2715) (SQLExecDirectW)') '\nCREATE TABLE test_date (\n\tid INTEGER NOT NULL IDENTITY(1,1), \n\tdt DATE NULL, \n\tPRIMARY KEY (id)\n)\n\n' ()

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• Accessing an enum stored in a QVariant

  - by Henry Thacker

  Hi, I have registered an enumeration type "ClefType" within my header file - this enum is registered with the MetaObject system using the Q_DECLARE_METATYPE and Q_ENUMS macros. qRegisterMetaType is also called in the class constructor. This allows me to use this type in a Q_PROPERTY, this all works fine. However, later on, I need to be able to get hold of the Q_PROPERTY of this enum type, given the object - in a form that is suitable for serialization. Ideally, it would be useful to store the integer value for that enum member, because I don't want this to be specific to the type of enum that is used - eventually I want to have several different enums. // This is inside a loop over all the properties on a given object QMetaProperty property = metaObject->property(propertyId); QString propertyName = propertyMeta.name(); QVariant variantValue = propertyMeta.read(serializeObject); // If, internally, this QVariant is of type 'ClefType', // how do I pull out the integer value for this enum? Unfortunately variantValue.toInt(); does not work - custom enums don't seem to be directly 'castable' to an integer value. Thanks in advance, Henry

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• Deleting JPA entity containing @CollectionOfElements throws ConstraintViolationException

  - by Lyle

  I'm trying to delete entities which contain lists of Integer, and I'm getting ConstraintViolationExceptions because of the foreign key on the table generated to hold the integers. It appears that the delete isn't cascading to the mapped collection. I've done quite a bit of searching, but all of the examples I've seen on how to accomplish this are in reference to a mapped collection of other entities which can be annotated; here I'm just storing a list of Integer. Here is the relevant excerpt from the class I'm storing: @Entity @Table(name="CHANGE_IDS") @GenericGenerator( name = "CHANGE_ID_GEN", strategy = "org.hibernate.id.enhanced.SequenceStyleGenerator", parameters = { @Parameter(name="sequence_name", value="course_changes_seq"), @Parameter(name="increment_size", value="5000"), @Parameter(name=" optimizer", value="pooled") } ) @NamedQueries ({ @NamedQuery( name="Changes.getByStatus", query= "SELECT c " + "FROM DChanges c " + "WHERE c.status = :status "), @NamedQuery( name="Changes.deleteByStatus", query= "DELETE " + "FROM Changes c " + "WHERE c.status = :status ") }) public class Changes { @Id @GeneratedValue(generator="CHANGE_ID_GEN") @Column(name = "ID") private final long id; @Enumerated(EnumType.STRING) @Column(name = "STATUS", length = 20, nullable = false) private final Status status; @Column(name="DOC_ID") @org.hibernate.annotations.CollectionOfElements @org.hibernate.annotations.IndexColumn(name="DOC_ID_ORDER") private List<Integer> docIds; } I'm deleting the Changes objects using a @NamedQuery: final Query deleteQuery = this.entityManager.createNamedQuery("Changes.deleteByStatus"); deleteQuery.setParameter("status", Status.POST_FLIP); final int deleted = deleteQuery.executeUpdate(); this.logger.info("Deleted " + deleted + " POST_FLIP Changes");

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• Compiling Java code in terminal having a Jar in CLASSPATH

  - by Masi

  How can you compile the code using javac in a terminal by using google-collections in CLASSPATH? Example of code trying to compile using javac in a terminal (works in Eclipse) import com.google.common.collect.BiMap; import com.google.common.collect.HashBiMap; public class Locate { ... BiMap<MyFile, Integer> rankingToResult = HashBiMap.create(); ... } Compiling in terminal src 288 % javac Locate.java Locate.java:14: package com.google.common.collect does not exist import com.google.common.collect.BiMap; ^ Locate.java:15: package com.google.common.collect does not exist import com.google.common.collect.HashBiMap; ^ Locate.java:153: cannot find symbol symbol : class BiMap location: class Locate BiMap<MyFile, Integer> rankingToResult = HashBiMap.create(); ^ Locate.java:153: cannot find symbol symbol : variable HashBiMap location: class Locate BiMap<MyFile, Integer> rankingToResult = HashBiMap.create(); ^ 4 errors My CLASSPATH src 289 % echo $CLASSPATH /u/1/bin/javaLibraries/google-collect-1.0.jar

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• N-Tier Architecture - Structure with multiple projects in VB.NET

  - by focus.nz

  I would like some advice on the best approach to use in the following situation... I will have a Windows Application and a Web Application (presentation layers), these will both access a common business layer. The business layer will look at a configuration file to find the name of the dll (data layer) which it will create a reference to at runtime (is this the best approach?). The reason for creating the reference at runtime to the data access layer is because the application will interface with a different 3rd party accounting system depending on what the client is using. So I would have a separate data access layer to support each accounting system. These could be separate setup projects, each client would use one or the other, they wouldn't need to switch between the two. Projects: MyCompany.Common.dll - Contains interfaces, all other projects have a reference to this one. MyCompany.Windows.dll - Windows Forms Project, references MyCompany.Business.dll MyCompany.Web.dll - Website project, references MyCompany.Business.dll MyCompany.Busniess.dll - Business Layer, references MyCompany.Data.* (at runtime) MyCompany.Data.AccountingSys1.dll - Data layer for accounting system 1 MyCompany.Data.AccountingSys2.dll - Data layer for accounting system 2 The project MyCompany.Common.dll would contain all the interfaces, each other project would have a reference to this one. Public Interface ICompany ReadOnly Property Id() as Integer Property Name() as String Sub Save() End Interface Public Interface ICompanyFactory Function CreateCompany() as ICompany End Interface The project MyCompany.Data.AccountingSys1.dll and MyCompany.Data.AccountingSys2.dll would contain the classes like the following: Public Class Company Implements ICompany Protected _id As Integer Protected _name As String Public ReadOnly Property Id As Integer Implements MyCompany.Common.ICompany.Id Get Return _id End Get End Property Public Property Name As String Implements MyCompany.Common.ICompany.Name Get Return _name End Get Set(ByVal value as String) _name = value End Set End Property Public Sub Save() Implements MyCompany.Common.ICompany.Save Throw New NotImplementedException() End Sub End Class Public Class CompanyFactory Implements ICompanyFactory Public Function CreateCompany() As ICompany Implements MyCompany.Common.ICompanyFactory.CreateCompany Return New Company() End Function End Class The project MyCompany.Business.dll would provide the business rules and retrieve data form the data layer: Public Class Companies Public Shared Function CreateCompany() As ICompany Dim factory as New MyCompany.Data.CompanyFactory Return factory.CreateCompany() End Function End Class Any opinions/suggestions would be greatly appreciated.

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• No output from exception

  - by Grasper

  Why does this code not print an exception stack trace? import java.util.concurrent.Executors; import java.util.concurrent.ScheduledExecutorService; import java.util.concurrent.TimeUnit; public class Playground { /** * @param args */ public static void main(String[] args) { startThread(); } private static void startThread() { ScheduledExecutorService timer = Executors .newSingleThreadScheduledExecutor(); Runnable r = new Runnable() { int dummyInt = 0; boolean dummyBoolean = false; @Override public void run() { dummyInt = Integer.parseInt("AAAA"); if (dummyBoolean) { dummyBoolean= false; } else { dummyBoolean= true; } } }; timer.scheduleAtFixedRate(r, 0, 100, TimeUnit.MILLISECONDS); } } How can I get it to? I would expect to see this: java.lang.NumberFormatException: For input string: "AAAA" at java.lang.NumberFormatException.forInputString(Unknown Source) at java.lang.Integer.parseInt(Unknown Source) at java.lang.Integer.parseInt(Unknown Source) at Playground$1.run(Playground.java:25) at java.util.concurrent.Executors$RunnableAdapter.call(Unknown Source) at java.util.concurrent.FutureTask$Sync.innerRunAndReset(Unknown Source) at java.util.concurrent.FutureTask.runAndReset(Unknown Source) at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$101(Unknown Source) at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.runPeriodic(Unknown Source) at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(Unknown Source) at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(Unknown Source) at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source) at java.lang.Thread.run(Unknown Source)

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• Why can't Doctrine retrieve my model data?

  - by scottm

  So, I'm trying to use Doctrine to retrieve some data. I have some basic code like this: $conn = Doctrine_Manager::connection(CONNECTION_STRING); $site = Doctrine_Core::getTable('Site')->find('00024'); echo $site->SiteName; However, this keeps throwing a SQL error that 'column siteid does not exist'. When I look at the exception the SQL query is this (you can see the error is that the inner_tbl alias for siteid is set to s__siteid, so querying inner_tabl.siteid is what's broken): SELECT TOP 1 [inner_tbl].[siteid] AS [s__siteid] FROM (SELECT TOP 1 [s].[siteid] AS [s__siteid], [s].[name] AS [s__name], [s].[address] AS [s__address], [s].[city] AS [s__city], [s].[zip] AS [s__zip], [s].[state] AS [s__state], [s].[region] AS [s__region], [s].[callprocessor] AS [s__callprocessor], [s].[active] AS [s__active], [s].[dateadded] AS [s__dateadded] FROM [Sites] [s] WHERE ([s].[siteid] = '00024') ) AS [inner_tbl] Why is the query being generated this way? Could it be the way the Yaml schema is laid out? Site: connection: 0 tableName: Sites columns: siteid: type: string(5) fixed: true unsigned: false primary: true autoincrement: false name: type: string(300) fixed: false unsigned: false notnull: true primary: false autoincrement: false address: type: string(100) fixed: false unsigned: false notnull: false primary: false autoincrement: false city: type: string(100) fixed: false unsigned: false notnull: false primary: false autoincrement: false zip: type: string(5) fixed: false unsigned: false notnull: false primary: false autoincrement: false state: type: string(2) fixed: true unsigned: false notnull: true primary: false autoincrement: false region: type: integer(4) fixed: false unsigned: false notnull: true default: (5) primary: false autoincrement: false callprocessor: type: integer(4) fixed: false unsigned: false notnull: true primary: false autoincrement: false active: type: integer(1) fixed: false unsigned: false notnull: true primary: false autoincrement: false dateadded: type: timestamp(16) fixed: false unsigned: false notnull: true default: (getdate()) primary: false autoincrement: false

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• The "first past the post election" query problem

  - by MPelletier

  This problem may seem like school work, but it isn't. At best it is self-imposed school work. I encourage any teachers to take is as an example if they wish. "First past the post" elections are single-round, meaning that whoever gets the most votes win, no second rounds. Suppose a table for an election. CREATE TABLE ElectionResults ( DistrictHnd INTEGER NOT NULL, PartyHnd INTEGER NOT NULL, CandidateName VARCHAR2(100) NOT NULL, TotalVotes INTEGER NOT NULL, PRIMARY KEY DistrictHnd, PartyHnd); The table has two foreign keys: DistrictHnd points to a District table (lists all the different electoral districts) and PartyHnd points to a Party table (lists all the different political parties). I won't bother with other tables here, joining them is trivial. This is just a wee bit of context. The question: What SQL query will return a table listing the DistrictHnd, PartyHnd, CandidateName and TotalVotes of the winners (max votes) in each District? This does not suppose any particular database system. If you wish to stick to a particular implementation of SQL, go the way of SQLite and MySQL. If you can devise a better schema (or an easier one), that is acceptable too. Criteria: simplicity, portability to other databases.

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• database design to speed up hibernate querying of large dataset

  - by paddydub

  I currently have the below tables representing a bus network mapped in hibernate, accessed from a Spring MVC based bus route planner I'm trying to make my route planner application perform faster, I load all the above tables into Lists to perform the route planner logic. I would appreciate if anyone has any ideas of how to speed my performace Or any suggestions of another method to approach this problem of handling a large set of data Coordinate Connections Table (INT,INT,INT)( Containing 50,000 Coordinate Connections) ID, FROMCOORDID, TOCOORDID 1 1 2 2 1 17 3 1 63 4 1 64 5 1 65 6 1 95 Coordinate Table (INT,DECIMAL, DECIMAL) (Containing 4700 Coordinates) ID , LAT, LNG 0 59.352669 -7.264341 1 59.352669 -7.264341 2 59.350012 -7.260653 3 59.337585 -7.189798 4 59.339221 -7.193582 5 59.341408 -7.205888 Bus Stop Table (INT, INT, INT)(Containing 15000 Stops) StopID RouteID COORDINATEID 1000100001 100 17 1000100002 100 18 1000100003 100 19 1000100004 100 20 1000100005 100 21 1000100006 100 22 1000100007 100 23 This is how long it takes to load all the data from each table: stop.findAll = 148ms, stops.size: 15670 Hibernate: select coordinate0_.COORDINATEID as COORDINA1_2_, coordinate0_.LAT as LAT2_, coordinate0_.LNG as LNG2_ from COORDINATES coordinate0_ coord.findAll = 51ms , coordinates.size: 4704 Hibernate: select coordconne0_.COORDCONNECTIONID as COORDCON1_3_, coordconne0_.DISTANCE as DISTANCE3_, coordconne0_.FROMCOORDID as FROMCOOR3_3_, coordconne0_.TOCOORDID as TOCOORDID3_ from COORDCONNECTIONS coordconne0_ coordinateConnectionDao.findAll = 238ms ; coordConnectioninates.size:48132 Hibernate Annotations @Entity @Table(name = "STOPS") public class Stop implements Serializable { @Id @GeneratedValue @Column(name = "COORDINATEID") private Integer CoordinateID; @Column(name = "LAT") private double latitude; @Column(name = "LNG") private double longitude; } @Table(name = "COORDINATES") public class Coordinate { @Id @GeneratedValue @Column(name = "COORDINATEID") private Integer CoordinateID; @Column(name = "LAT") private double latitude; @Column(name = "LNG") private double longitude; } @Entity @Table(name = "COORDCONNECTIONS") public class CoordConnection { @Id @GeneratedValue @Column(name = "COORDCONNECTIONID") private Integer CoordinateID; /** * From Coordinate_id value */ @Column(name = "FROMCOORDID", nullable = false) private int fromCoordID; /** * To Coordinate_id value */ @Column(name = "TOCOORDID", nullable = false) private int toCoordID; //private Coordinate toCoordID; }

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• Export Multiple Crystal Reports ASP.NET

  - by AProgrammer

  Hey all, I want to export 2 different reports when I click an Export button. The problem is the routine only fires once and I only get one report to print out. Am I doing something wrong? I think it has something to do with the HTTPResponse, but I'm not sure. Here's my code: Dim badgeSize As Integer = 0 'Drop Down selection Dim badgeData As New DataSet 'Visitor Badge Data Dim badgeEmployeeData As New DataSet 'Employee Badge Data Dim badgeTotals As Integer = 0 'Totals for both badgeSize = ddlBadgeSize.SelectedValue ' Get Visitor Data badgeData = _DatabaseAccess.GetProjectReportData(sessionInfo.myEventID, sessionInfo.EventCreator) ' Get Employee Data badgeEmployeeData = _DatabaseAccess.GetProjectReportEmployeeData(sessionInfo.myEventID, sessionInfo.EventCreator) 'Obtain Totals badgeTotals = badgeData.Tables(0).Rows.Count + badgeEmployeeData.Tables(0).Rows.Count If badgeTotals = 0 Then ShowMessage("There are no badges to print.") Exit Sub End If If badgeSize.Equals(0) Then 'Small If badgeEmployeeData.Tables(0).Rows.Count > 0 Then If badgeEmployeeData.Tables(0).Rows.Count >= 6 Then PrintProjectBadges(badgeEmployeeData, "Employee", badgeSize) Else PrintStandardDymo(badgeEmployeeData, "Employee", 1) End If End If If badgeData.Tables(0).Rows.Count > 0 Then If badgeData.Tables(0).Rows.Count >= 6 Then PrintProjectBadges(badgeData, "Visitor", badgeSize) Else PrintStandardDymo(badgeData, "Visitor", 1) End If End If else 'do somethign else endif And the Report Code: Private Sub PrintProjectBadges(ByVal theData As DataSet, ByVal badgeType As String, ByVal badgeSize As Integer) Dim ourReport As New ReportDocument Dim crConnectionInfo As New ConnectionInfo(SetCrystalConnection) If badgeSize = 0 Then Try If badgeType = "Visitor" Then ourReport.Load(Server.MapPath("SmallProjectBadge.rpt"), OpenReportMethod.OpenReportByDefault) 'LIVE SERVER USE Else ourReport.Load(Server.MapPath("SmallProjectEmployeeBadge.rpt"), OpenReportMethod.OpenReportByDefault) 'LIVE SERVER USE End If Catch ex As Exception Dim TraceList As New ArrayList TraceList.Add("DBLog") DatabaseAccess.WriteToErrorLog("Visitor Registration", "Printing Project Badges", ex.Message, TraceEventType.Information, 1, TraceList) Exit Sub End Try ourReport.SetDataSource(theData.Tables("Project")) Else 'Do somethign else... End If Response.Buffer = True 'Clear the response content and headers Response.ClearContent() Response.ClearHeaders() SetLogon(ourReport, crConnectionInfo) 'Export the Report to Response stream in PDF format and file name Customers ourReport.ExportToHttpResponse(ExportFormatType.PortableDocFormat, Response, True, "Visitor_Badges") Response.End() 'Response.Close() End Sub Any Help would be much appreciated.

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• Array help needed for unit conversion application

  - by Manolis

  I have a project to do in Visual Basic. My problem is that the outcome is always wrong (ex. instead of 2011 it gives 2000). And i cannot set as Desired unit the Inch(1) or feet(3), it gives the Infinity error. And if i put as Original and Desired unit the inch(1), the outcome is "Not a Number". Here's the code i made so far. The project is about arrays. Any help appreciated. Public Class Form1 Private Sub btnConvert_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnConvert.Click Dim original(9) As Long Dim desired(9) As Long Dim a As Integer Dim o As Integer Dim d As Integer Dim inch As Long, fathom As Long, furlong As Long, kilometer As Long Dim meter As Long, miles As Long, rod As Long, yard As Long, feet As Long a = Val(Input3.Text) o = Val(Input1.Text) d = Val(Input2.Text) inch& = 0.0833 rod& = 16.5 yard& = 3 furlong& = 660 meter& = 3.28155 kilometer& = 3281.5 fathom& = 6 miles& = 5280 original(1) = inch original(2) = fathom original(3) = feet original(4) = furlong original(5) = kilometer original(6) = meter original(7) = miles original(8) = rod original(9) = yard desired(1) = inch desired(2) = fathom desired(3) = feet desired(4) = furlong desired(5) = kilometer desired(6) = meter desired(7) = miles desired(8) = rod desired(9) = yard If o < 1 Or o > 9 Or d < 1 Or d > 9 Then MessageBox.Show("Units must range from 1-9.", "Error", _ MessageBoxButtons.OK, _ MessageBoxIcon.Information) Return End If Output.Text = (a * original(o)) / desired(d) End Sub End Class

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• Symfony fk issue on insertion

  - by Daniel Hertz

  Hi, I posted a similar problem but it could not be resolved. I create a relational database of users and groups but for some reason I cannot insert test data with fixtures properly. Here is a sample of the schema: User: actAs: { Timestampable: ~ } columns: name: { type: string(255), notnull: true } email: { type: string(255), notnull: true, unique: true } nickname: { type: string(255), unique: true } password: { type: string(300), notnull: true } image: { type: string(255) } Group: actAs: { Timestampable: ~ } columns: name: { type: string(500), notnull: true } image: { type: string(255) } type: { type: string(255), notnull: true } created_by_id: { type: integer } relations: User: { onDelete: SET NULL, class: User, local: created_by_id, foreign: id, foreignAlias: groups_created } FanOf: actAs: { Timestampable: ~ } columns: user_id: { type: integer, primary: true } group_id: { type: integer, primary: true } relations: User: { onDelete: CASCADE, local: user_id, foreign: id, foreignAlias: fanhood } Group: { onDelete: CASCADE, local: group_id, foreign: id, foreignAlias: fanhood } And this is the data i try to input: User: user1: name: Danny email: [email protected] nickname: danny password: f05050400c5e586fa6629ef497be Group: group1: name: Mets type: sports FanOf: fans1: user_id: user1 group_id: group1 I keep getting this error: SQLSTATE[23000]: Integrity constraint violation: 1452 Cannot add or update a child row: a foreign key constraint fails (`krowdd`.`fan_of`, CONSTRAINT `fan_of_user_id_user_id` FOREIGN KEY (`user_id`) REFERENCES `user` (`id`) ON DELETE CASCADE) The users and groups are clearly being created before the "fanhood" is so why am I getting this error?? Thanks!

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• autocommit and @Transactional and Cascading with spring, jpa and hibernate

  - by subes

  Hi, what I would like to accomplish is the following: have autocommit enabled so per default all queries get commited if there is a @Transactional on a method, it overrides the autocommit and encloses all queries into a single transaction, thus overriding the autocommit if there is a @Transactional method that calls other @Transactional annotated methods, the outer most annotation should override the inner annotaions and create a larger transaction, thus annotations also override eachother I am currently still learning about spring-orm and couldn't find documentation about this and don't have a test project for this yet. So my questions are: What is the default behaviour of transactions in spring? If the default differs from my requirement, is there a way to configure my desired behaviour? Or is there a totally different best practice for transactions? --EDIT-- I have the following test-setup: @javax.persistence.Entity public class Entity { @Id @GeneratedValue private Integer id; private String name; public Integer getId() { return id; } public void setId(Integer id) { this.id = id; } public String getName() { return name; } public void setName(String name) { this.name = name; } } @Repository public class Dao { @PersistenceContext private EntityManager em; public void insert(Entity ent) { em.persist(ent); } @SuppressWarnings("unchecked") public List<Entity> selectAll() { List<Entity> ents = em.createQuery("select e from " + Entity.class.getName() + " e").getResultList(); return ents; } } If I have it like this, even with autocommit enabled in hibernate, the insert method does nothing. I have to add @Transactional to the insert or the method calling insert for it to work... Is there a way to make @Transactional completely optional?

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• Comparable and Comparator contract with regards to null

  - by polygenelubricants

  Comparable contract specifies that e.compareTo(null) must throw NullPointerException. From the API: Note that null is not an instance of any class, and e.compareTo(null) should throw a NullPointerException even though e.equals(null) returns false. On the other hand, Comparator API mentions nothing about what needs to happen when comparing null. Consider the following attempt of a generic method that takes a Comparable, and return a Comparator for it that puts null as the minimum element. static <T extends Comparable<? super T>> Comparator<T> nullComparableComparator() { return new Comparator<T>() { @Override public int compare(T el1, T el2) { return el1 == null ? -1 : el2 == null ? +1 : el1.compareTo(el2); } }; } This allows us to do the following: List<Integer> numbers = new ArrayList<Integer>( Arrays.asList(3, 2, 1, null, null, 0) ); Comparator<Integer> numbersComp = nullComparableComparator(); Collections.sort(numbers, numbersComp); System.out.println(numbers); // "[null, null, 0, 1, 2, 3]" List<String> names = new ArrayList<String>( Arrays.asList("Bob", null, "Alice", "Carol") ); Comparator<String> namesComp = nullComparableComparator(); Collections.sort(names, namesComp); System.out.println(names); // "[null, Alice, Bob, Carol]" So the questions are: Is this an acceptable use of a Comparator, or is it violating an unwritten rule regarding comparing null and throwing NullPointerException? Is it ever a good idea to even have to sort a List containing null elements, or is that a sure sign of a design error?

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• ibm informix spatial datablade select statement error

  - by changed

  Hi I am using IBM informix spatial datablade module for some geo specific data. I am trying to find points in table xmlData lying in a specified region. But i am getting this error for select statement. SELECT sa.pre, sa.post FROM xmlData sa WHERE ST_Contains( ST_PolyFromText('polygon((2 2,6 2,6 6,2 6,2 2))',6),sa.point) Query: select count(*) as mycnt fromText('polygon((2 2,6 2,6 6,2 6,2 2))',6),sa.point) Error: -201 [Informix][Informix ODBC Driver][Informix]A syntax error has occurred. (SQLPrepare[-201] at /work/lwchan/workspace/OATPHPcompile/pdo_informix/pdo_informix/informix_driver.c:131) If any one can help me with this. CREATE TABLE xmlData (row_id integer NOT NULL, x integer, y integer, tagname varchar(40,1), point ST_POINT ); EXECUTE FUNCTION SE_CreateSRID(0, 0, 250000, 250000, "use the return value in next query last column"); INSERT INTO geometry_columns (f_table_catalog, f_table_schema, f_table_name, f_geometry_column, geometry_type, srid) VALUES ("mydatabase", -- database name "informix", -- user name "xmlData", -- table name "point", -- spatial column name 1, -- column type (1 = point) 6); -- srid //use value returned by above query. INSERT INTO xmlData VALUES ( 1, 20,20, 'country', ST_PointFromText('point (20 20)',6) ); INSERT INTO xmlData VALUES ( 1, 12,13, 'sunday', ST_PointFromText('point (12 13)',6) ); INSERT INTO xmlData VALUES ( 1, 21,22, 'monday', ST_PointFromText('point (21 22)',6) ); SELECT sa.pre, sa.post FROM xmlData sa WHERE ST_Contains( ST_PolyFromText('polygon((1 1,30 1,30 30,1 30,1 1))', 6),sa.point); I am using following query as reference "ibm link". SELECT name, type, zone FROM sensitive_areas WHERE SE_EnvelopesIntersect(zone, ST_PolyFromText('polygon((20000 20000,60000 20000,60000 60000,20000 60000,20000 20000))', 5));

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• Importing fixtures with foreign keys and SQLAlchemy?

  - by Chris Reid

  I've been experimenting with using fixture to load test data sets into my Pylons / PostgreSQL app. This works great except that it fails to properly create foreign keys if they reference an auto increment id field. My fixture looks like this: class AuthorsData(DataSet): class frank_herbert: first_name = "Frank" last_name = "Herbert" class BooksData(DataSet): class dune: title = "Dune" author_id = AuthorsData.frank_herbert.ref('id') And the model: t_authors = sa.Table("authors", meta.metadata, sa.Column("id", sa.types.Integer, primary_key=True), sa.Column("first_name", sa.types.String(100)), sa.Column("last_name", sa.types.String(100)), ) t_books = sa.Table("books", meta.metadata, sa.Column("id", sa.types.Integer, primary_key=True), sa.Column("title", sa.types.String(100)), sa.Column("author_id", sa.types.Integer, sa.ForeignKey('authors.id')) ) When running "paster setup-app development.ini", SQLAlchemey reports the FK value as "None" so it's obviously not finding it: 15:59:48,683 INFO [sqlalchemy.engine.base.Engine.0x...9eb0] INSERT INTO books (title, author_id) VALUES (%(title)s, %(author_id)s) RETURNING books.id 15:59:48,683 INFO [sqlalchemy.engine.base.Engine.0x...9eb0] {'author_id': None, 'title': 'Dune'} The fixture docs actually warn that this might be a problem: "However, in some cases you may need to reference an attribute that does not have a value until it is loaded, like a serial ID column. (Note that this is not supported by the SQLAlchemy data layer when using sessions.)" http://farmdev.com/projects/fixture/using-dataset.html#referencing-foreign-dataset-classes Does this mean that this is just not supported with SQLAlchemy? Or is it possible to load the data without using SA "sessions"? How are other people handling this issue?

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• Saving a record in Authlogic table

  - by denniss

  I am using authlogic to do my authentication. The current model that serves as the authentication model is the user model. I want to add a "belongs to" relationship to user which means that I need a foreign key in the user table. Say the foreign key is called car_id in the user's model. However, for some reason, when I do u = User.find(1) u.car_id = 1 u.save! I get ActiveRecord::RecordInvalid: Validation failed: Password can't be blank My guess is that this has something to do with authlogic. I do not have validation on password on the user's model. This is the migration for the user's table. def self.up create_table :users do |t| t.string :email t.string :first_name t.string :last_name t.string :crypted_password t.string :password_salt t.string :persistence_token t.string :single_access_token t.string :perishable_token t.integer :login_count, :null => false, :default => 0 # optional, see Authlogic::Session::MagicColumns t.integer :failed_login_count, :null => false, :default => 0 # optional, see Authlogic::Session::MagicColumns t.datetime :last_request_at # optional, see Authlogic::Session::MagicColumns t.datetime :current_login_at # optional, see Authlogic::Session::MagicColumns t.datetime :last_login_at # optional, see Authlogic::Session::MagicColumns t.string :current_login_ip # optional, see Authlogic::Session::MagicColumns t.string :last_login_ip # optional, see Authlogic::Session::MagicColumns t.timestamps end end And later I added the car_id column to it. def self.up add_column :users, :user_id, :integer end Is there anyway for me to turn off this validation?

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• Parsing CSV string and binding it to listbox

  - by Amit Ranjan

  I have splitted comma separated values in an string array, something like this str[0] ="210" str[1] ="abc.pdf" str[2] = "211" str[3] = "xyz.docx" and so on. Please note 0,2,4,6,8 [even positions] are having number and odd positions are having string. I am having a class Attachmodel Public Class AttachmentModel Private _attachmentID As Integer = 0 Private _attachmentPath As String = "" ''' <summary> ''' Get Set Attachment ID ''' </summary> ''' <value></value> ''' <returns></returns> ''' <remarks></remarks> Public Property AttachmentID() As Integer Get Return _attachmentID End Get Set(ByVal value As Integer) _attachmentID = value End Set End Property ''' <summary> ''' Get Set Attachment Path ''' </summary> ''' <value></value> ''' <returns></returns> ''' <remarks></remarks> Public Property AttachmentPath() As String Get Return _attachmentPath End Get Set(ByVal value As String) _attachmentPath = value End Set End Property End Class In the above i want to set the values and bind it to the grid, using List

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