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• Struggling with a data modeling problem

  - by rpat

  I am struggling with a data model (I use MySQL for the database). I am uneasy about what I have come up with. If someone could suggest a better approach, or point me to some reference matter I would appreciate it. The data would have organizations of many types. I am trying to do a 3 level classification (Class, Category, Type). Say if I have 'Italian Restaurant', it will have the following classification Food Services Restaurants Italian However, an organization may belong to multiple groups. A restaurant may also serve Chinese and Italian. So it will fit into 2 classifications Food Services Restaurants Italian Food Services Restaurants Chinese The classification reference tables would be like the following: ORG_CLASS (RowId, ClassCode, ClassName) 1, FOOD, Food Services ORG_CATEGORY(RowId, ClassCode, CategoryCode, CategoryName) 1, FOOD, REST, Restaurants ORG_TYPE (RowId, ClassCode, CategoryCode, TypeCode, TypeName) 100, FOOD, REST, ITAL, Italian 101, FOOD, REST, CHIN, Chinese 102, FOOD, REST, SPAN, Spanish 103, FOOD, REST, MEXI, Mexican 104, FOOD, REST, FREN, French 105, FOOD, REST, MIDL, Middle Eastern The actual data tables would be like the following: I will allow an organization a max of 3 classifications. I will have 3 GroupIds each pointing to a row in ORG_TYPE. So I have my ORGANIZATION_TABLE ORGANIZATION_TABLE (OrgGroupId1, OrgGroupId2, OrgGroupId3, OrgName, OrgAddres) 100,103,NULL,MyRestaurant1, MyAddr1 100,102,NULL,MyRestaurant2, MyAddr2 100,104,105, MyRestaurant3, MyAddr3 During data add, a dialog could let the user choose the clssa, category, type and the corresponding GroupId could be populated with the rowid from the ORG_TYPE table. During Search, If all three classification are chosen, It will be more specific. For example, if Food Services Restaurants Italian is the criteria, the where clause would be 'where OrgGroupId1 = 100' If only 2 levels are chosen Food Services Restaurants I have to do 'where OrgGroupId1 in (100,101,102,103,104,105, .....)' - There could be a hundred in that list I will disallow class level search. That is I will force selection of a class and category The Ids would be integers. I am trying to see performance issues and other issues. Overall, would this work? or I need to throw this out and start from scratch.

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• validation control unable to find its control to validate

  - by nat

  i have a repeater that is bound to a number of custom dataitems/types on the itemdatabound event for the repeater the code calls a renderedit function that depending on the custom datatype will render a custom control. it will also (if validation flag is set) render a validation control for the appropriate rendered edit control the edit control overrides the CreateChildControls() method for the custom control adding a number of literalControls thus protected override void CreateChildControls() { //other bits removed - but it is this 'hidden' control i am trying to validate this.Controls.Add(new LiteralControl(string.Format( "<input type=\"text\" name=\"{0}\" id=\"{0}\" value=\"{1}\" style=\"display:none;\" \">" , this.UniqueID , this.MediaId.ToString()) )); //some other bits removed } the validation control is rendered like this: where the passed in editcontrol is the control instance of which the above createchildcontrols is a method of.. public override Control RenderValidationControl(Control editControl) { Control ctrl = new PlaceHolder(); RequiredFieldValidator req = new RequiredFieldValidator(); req.ID = editControl.ClientID + "_validator"; req.ControlToValidate = editControl.UniqueID; req.Display = ValidatorDisplay.Dynamic; req.InitialValue = "0"; req.ErrorMessage = this.Caption + " cannot be blank"; ctrl.Controls.Add(req); return ctrl; } the problem is, altho the validation controls .ControlToValidate property is set to the uniqueid of the editcontrol. when i hit the page i get the following error: Unable to find control id 'FieldRepeater$ctl01$ctl00' referenced by the 'ControlToValidate' property of 'FieldRepeater_ctl01_ctl00_validator'. i have tried changing the literal in the createchildcontrols to a new TextBox(), and then set the id etc then, but i get a similar problem. can anyone enlighten me? is this because of the order the controls are rendered in? ie the validation control is written before the editcontrol? or... anyhow any help much appreciated thanks nat

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• ASP.NET MVC PartialView generic ModelView

  - by Greg Ogle

  I have an ASP.NET MVC application which I want to dynamically pick the partial view and what data gets passed to it, while maintaining strong types. So, in the main form, I want a class that has a view model that contains a generically typed property which should contain the data for the partial view's view model. public class MainViewModel<T> { public T PartialViewsViewModel { get; set; } } In the User Control, I would like something like: Inherits="System.Web.Mvc.ViewUserControl<MainViewModel<ParticularViewModel>>" %> Though in my parent form, I must put Inherits="System.Web.Mvc.ViewPage<MainViewModel<ParticularViewModel>>" %> for it to work. Is there a way to work around this? The use case is to make the user control pluggable. I understand that I could inherit a base class, but that would put me back to having something like a dictionary instead of a typed view model.

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• @font-face fonts only work on their own domain

  - by Ben

  I am trying to create a type of font repository for use on my websites, so that I can call to any font in the repository in my css without any other set-up. To do this I created a subdomain on which I placed folders for each font in the repository that contained the various file types for each font. I also placed a css file called font-face.css on the root of the subdomain and filled it with @font-face declarations for each of the fonts, the fonts a linked with an absolute link so that they can be used from anywhere. My issue is that it seems that I can only use the fonts on that subdomain where they are located, on my other sites the font does not show. Using firebug I determined that the font-face.css file was successfully being linked to and loaded. So why does the font not correctly load? Is there protection on the font files or something? I am using all fonts that I should be allowed to do this with, so I don't see why this is occurring. Maybe it is an apache issue, but I can download the font just fine when I link to it. Oh, and just to clarify, I am not violating any copyrights by setting this up, all the fonts I am using are licensed to allow this sort of thing. I would however like to set up a way that only I can have access to this repository of fonts but that's another project.

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• Number of args for stored procedure PLS-00306

  - by Peter Kaleta

  Hi I have problem with calling for my procedure. Oracle scrams PLS-00306 Error: Wrong number of types of arguments in call to procedure. With my type declaration procedure has exact the same declaration like in header below. If I run it as separate procedure it works, when i work in ODCI interface for extensible index creation, it throws PLS-00306. MEMBER PROCEDURE FILL_TREE_LVL (target_column VARCHAR2, cur_lvl NUMBER, max_lvl NUMBER, parent_rect NUMBER,start_x NUMBER, start_y NUMBER, end_x NUMBER, end_y NUMBER) IS stmt VARCHAR2(2000); rect_id NUMBER; diff_x NUMBER; diff_y NUMBER; new_start_x NUMBER; new_end_x NUMBER; i NUMBER; j NUMBER; BEGIN {...} END FILL_TREE_LVL; STATIC FUNCTION ODCIINDEXCREATE (ia SYS.ODCIINDEXINFO, parms VARCHAR2, env SYS.ODCIEnv) RETURN NUMBER IS stmt VARCHAR2(2000); stmt2 VARCHAR2(2000); min_x NUMBER; max_x NUMBER; min_y NUMBER; max_y NUMBER; lvl NUMBER; rect_id NUMBER; pt_tab VARCHAR2(50); rect_tab VARCHAR2(50); cnum NUMBER; TYPE point_rect is RECORD( point_id NUMBER, rect_id NUMBER ); TYPE point_rect_tab IS TABLE OF point_rect; pr_table point_rect_tab; BEGIN {...} FILL_TREE_LVL('any string', 0, lvl,0, min_x, min_y, max_x, max_y); {...} END;

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• How to add XmlInclude attribute dynamically

  - by Anindya Chatterjee

  I have the following classes [XmlRoot] public class AList { public List<B> ListOfBs {get; set;} } public class B { public string BaseProperty {get; set;} } public class C : B { public string SomeProperty {get; set;} } public class Main { public static void Main(string[] args) { var aList = new AList(); aList.ListOfBs = new List<B>(); var c = new C { BaseProperty = "Base", SomeProperty = "Some" }; aList.ListOfBs.Add(c); var type = typeof (AList); var serializer = new XmlSerializer(type); TextWriter w = new StringWriter(); serializer.Serialize(w, aList); } } Now when I try to run the code I got an InvalidOperationException at last line saying that The type XmlTest.C was not expected. Use the XmlInclude or SoapInclude attribute to specify types that are not known statically. I know that adding a [XmlInclude(typeof(C))] attribute with [XmlRoot] would solve the problem. But I want to achieve it dynamically. Because in my project class C is not known prior to loading. Class C is being loaded as a plugin, so it is not possible for me to add XmlInclude attribute there. I tried also with TypeDescriptor.AddAttributes(typeof(AList), new[] { new XmlIncludeAttribute(c.GetType()) }); before var type = typeof (AList); but no use. It is still giving the same exception. Does any one have any idea on how to achieve it?

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• Neural Network with softmax activation

  - by Cambium

  This is more or less a research project for a course, and my understanding of NN is very/fairly limited, so please be patient :) ============== I am currently in the process of building a neural network that attempts to examine an input dataset and output the probability/likelihood of each classification (there are 5 different classifications). Naturally, the sum of all output nodes should add up to 1. Currently, I have two layers, and I set the hidden layer to contain 10 nodes. I came up with two different types of implementations 1) Logistic sigmoid for hidden layer activation, softmax for output activation 2) Softmax for both hidden layer and output activation I am using gradient descent to find local maximums in order to adjust the hidden nodes' weights and the output nodes' weights. I am certain in that I have this correct for sigmoid. I am less certain with softmax (or whether I can use gradient descent at all), after a bit of researching, I couldn't find the answer and decided to compute the derivative myself and obtained softmax'(x) = softmax(x) - softmax(x)^2 (this returns an column vector of size n). I have also looked into the MATLAB NN toolkit, the derivative of softmax provided by the toolkit returned a square matrix of size nxn, where the diagonal coincides with the softmax'(x) that I calculated by hand; and I am not sure how to interpret the output matrix. I ran each implementation with a learning rate of 0.001 and 1000 iterations of back propagation. However, my NN returns 0.2 (an even distribution) for all five output nodes, for any subset of the input dataset. My conclusions: o I am fairly certain that my gradient of descent is incorrectly done, but I have no idea how to fix this. o Perhaps I am not using enough hidden nodes o Perhaps I should increase the number of layers Any help would be greatly appreciated! The dataset I am working with can be found here (processed Cleveland): http://archive.ics.uci.edu/ml/datasets/Heart+Disease

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• Database Design Question regaurding duplicate information.

  - by galford13x

  I have a database that contains a history of product sales. For example the following table CREATE TABLE SalesHistoryTable ( OrderID, // Order Number Unique to all orders ProductID, // Product ID can be used as a Key to look up product info in another table Price, // Price of the product per unit at the time of the order Quantity, // quantity of the product for the order Total, // total cost of the order for the product. (Price * Quantity) Date, // Date of the order StoreID, // The store that created the Order PRIMARY KEY(OrderID)); The table will eventually have millions of transactions. From this, profiles can be created for products in different geographical regions (based on the StoreID). Creating these profiles can be very time consuming as a database query. For example. SELECT ProductID, StoreID, SUM(Total) AS Total, SUM(Quantity) QTY, SUM(Total)/SUM(Quantity) AS AvgPrice FROM SalesHistoryTable GROUP BY ProductID, StoreID; The above query could be used to get the Information based on products for any particular store. You could then determine which store has sold the most, has made the most money, and on average sells for the most/least. This would be very costly to use as a normal query run anytime. What are some design descisions in order to allow these types of queries to run faster assuming storage size isn’t an issue. For example, I could create another Table with duplicate information. Store ID (Key), Product ID, TotalCost, QTY, AvgPrice And provide a trigger so that when a new order is received, the entry for that store is updated in a new table. The cost for the update is almost nothing. What should be considered when given the above scenario?

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• MyMessage<T> throws an exception when calling XmlSerializer

  - by Arthis

  I am very new to nservicebus. I am using version 3.0.1, the last one up to date. And I wonder if my case is a normal limitation of NSB, I am not aware of. I have an asp.net MVC application, I am trying to setup and in my global.asax, I have the following : var configure = Configure.WithWeb() .DefaultBuilder() .ForMvc() .XmlSerializer(); But I have an error with the XmlSerializer when dealing with one of my object: [Serializable] public class MyMessage<T> : IMessage { public T myobject { get; set; } } I pass trough : XmlSerializer() instance.Initialize(types); this.InitType(type, moduleBuilder); this.InitType(info2.PropertyType, moduleBuilder); and then when dealing With T, string typeName = GetTypeName(t); typename is null and the following instruction : if (!nameToType.ContainsKey(typeName)) ends in error. null value not allowed. Is this some limitations to Nservicebus, or am I messing something up?

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• Linq Getting Customers group by date and then by their type

  - by Nitin varpe

  I am working on generating report for showing customer using LINQ in C#. I want to show no. of customers of each type. There are 3 types of customer registered, guest and manager. I want to group by customers by registered date and then by type of customer. i.e If today 3 guest, 4 registered and 2 manager are inserted. and tomorrow 4,5 and 6 are registered resp. then report should show Number of customers registerd on the day . separate row for each type. DATE TYPEOF CUSTOMER COUNT 31-10-2013 GUEST 3 31-10-2013 REGISTERED 4 31-10-2013 MANAGER 2 30-10-2013 GUEST 5 30-10-2013 REGISTERED 10 30-10-2013 MANAGER 3 LIKE THIS . var subquery = from eat in _customerRepo.Table group eat by new { yy = eat.CreatedOnUTC.Value.Year, mm = eat.CreatedOnUTC.Value.Month, dd = eat.CreatedOnUTC.Value.Day } into g select new { Id = g.Min(x => x.Id) }; var query = from c in _customerRepo.Table join cin in subquery.Distinct() on c.Id equals cin.Id select c; By above query I get minimum cutomers registerd on that day Thanks in advance

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• F#, Linux and makefiles

  - by rwallace

  I intend to distribute an F# program as both binary and source so the user has the option of recompiling it if desired. On Windows, I understand how to do this: provide .fsproj and .sln files, which both Visual Studio and MSBuild can understand. On Linux, the traditional solution for C programs is a makefile. This depends on gcc being directly available, which it always is. The F# compiler can be installed on Linux and works under Mono, so that's fine so far. However, as far as I can tell, it doesn't create a scenario where fsc runs the compiler, instead the command is mono ...path.../fsc.exe. This is also fine, except I don't know what the path is going to be. So the full command to run the compiler in my case could be mono ~/FSharp-2.0.0.0/bin/fsc.exe types.fs tptp.fs main.fs -r FSharp.PowerPack.dll except that I'm not sure where fsc.exe will actually be located on the user's machine. Is there a way to find that out within a makefile, or would it be better to fall back on just explaining the above in the documentation and relying on the user to modify the command according to his setup?

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• GWT serialization issue

  - by Eddy

  I am having a heck of a time returning an ArrayList of objects that implement IsSerializable via RPC. The IsSerializable pojo contains one variable, a String, and has a 0 parameter constructor. I have removed the .gwt.rpc file from my war and still I get: com.google.gwt.user.client.rpc.SerializationException: Type 'com.test.myApp.client.model.Test' was not included in the set of types which can be serialized by this SerializationPolicy or its Class object could not be loaded. For security purposes, this type will not be serialized.: instance = com.test.myApp.client.model.Test@17a9692 at com.google.gwt.user.server.rpc.impl.ServerSerializationStreamWriter.serialize(ServerSerializationStreamWriter.java:610) I am using GWT 2.0.2 with jdk 1.6.0_18. Any ideas on what might be going on or what I am doing wrong? Here is the code for the Test class and the remote method is returning ArrayList. I even modified the code for it to just return one instance of Test with the same result: the exception above. package com.test.myApp.client.model; import com.google.gwt.user.client.rpc.IsSerializable; public class Test implements IsSerializable{ private String s; public Test() {} public Test(String s) { this.s = s; } public String getS() { return s; } public void setS(String s) { this.s = s; } } Greatly appreciate the help! Eddy

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• Why Sql not bringing back results unless I set varchar size?

  - by Tom

  I've got an SQL script that fetches results based on the colour passed to it, but unless I set the size of the variable defined as a varchar to (50) no results are returned. If I use: like ''+@Colour+'%' then it works but I don't really want to use it in case it brings back results I don't need or want. The column FieldValue has a type of Varchar(Max) (which can't be changed as this field can store different things). It is part of aspdotnetstorefront package so I can't really change the tables or field types. This doesn't work: declare @Col VarChar set @Col = 'blu' select * from dbo.MetaData as MD where MD.FieldValue = @Colour But this does work: declare @Col VarChar (50) set @Col = 'blu' select * from dbo.MetaData as MD where MD.FieldValue = @Colour The code is used in the following context, but should work either way <query name="Products" rowElementName="Variant"> <sql> <![CDATA[ select * from dbo.MetaData as MD where MD.Colour = @Colour ]]> </sql> <queryparam paramname="@ProductID" paramtype="runtime" requestparamname="pID" sqlDataType="int" defvalue="0" validationpattern="^\d{1,10}$" /> <queryparam paramname="@Colour" paramtype="runtime" requestparamname="pCol" sqlDataType="varchar" defvalue="" validationpattern=""/> </query> Any Ideas?

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• How to perform spatial partitioning in n-dimensions?

  - by kevin42

  I'm trying to design an implementation of Vector Quantization as a c++ template class that can handle different types and dimensions of vectors (e.g. 16 dimension vectors of bytes, or 4d vectors of doubles, etc). I've been reading up on the algorithms, and I understand most of it: here and here I want to implement the Linde-Buzo-Gray (LBG) Algorithm, but I'm having difficulty figuring out the general algorithm for partitioning the clusters. I think I need to define a plane (hyperplane?) that splits the vectors in a cluster so there is an equal number on each side of the plane. [edit to add more info] This is an iterative process, but I think I start by finding the centroid of all the vectors, then use that centroid to define the splitting plane, get the centroid of each of the sides of the plane, continuing until I have the number of clusters needed for the VQ algorithm (iterating to optimize for less distortion along the way). The animation in the first link above shows it nicely. My questions are: What is an algorithm to find the plane once I have the centroid? How can I test a vector to see if it is on either side of that plane?

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• emacs: x-popup-menu max size constraints?

  - by Cheeso

  I'm working on an intellisense or code-completion capability for C#. So far, so good. Right now I have basic completion working. There are 2 ways to request completion. The first cycles through all the potential matches. The second presents a popup menu of the matches. It works for types: And also for local variables: I'm confronting two problems with x-popup-menu: the popup menu can expand to consume all available screen space, when the number of choices is large. Literally it can obscure the entire screen. The silly thing is, it's scrollable. First it expands to consume all available space, then it also becomes scrollable. Is there a way I can limit the maximum size of x-popup-menu? To specify the position of the popup menu, I pass in a position, and x-popup-menu uses that as the *middle*, not the left, of the top line of the menu. Why middle? who knows. What this means is, if I specify (40 . 60) for the location of the menu, and the menu happens to be 100 pixels wide, the menu will extend beyond the left border of the emacs window. You can see this in the 2nd image above. If I knew how wide the popup would be before specifying the position, I could compensate. But I don't. Is there a workaround? Is there a way to get x-popup-menu to take its position as the LEFT rather than the middle.

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• how to handle multiple profiles per user?

  - by Scott Willman

  I'm doing something that doesn't feel very efficient. From my code below, you can probably see that I'm trying to allow for multiple profiles of different types attached to my custom user object (Person). One of those profiles will be considered a default and should have an accessor from the Person class. Can this be done better? from django.db import models from django.contrib.auth.models import User, UserManager class Person(User): public_name = models.CharField(max_length=24, default="Mr. T") objects = UserManager() def save(self): self.set_password(self.password) super(Person, self).save() def _getDefaultProfile(self): def_teacher = self.teacher_set.filter(default=True) if def_teacher: return def_teacher[0] def_student = self.student_set.filter(default=True) if def_student: return def_student[0] def_parent = self.parent_set.filter(default=True) if def_parent: return def_parent[0] return False profile = property(_getDefaultProfile) def _getProfiles(self): # Inefficient use of QuerySet here. Tolerated because the QuerySets should be very small. profiles = [] if self.teacher_set.count(): profiles.append(list(self.teacher_set.all())) if self.student_set.count(): profiles.append(list(self.student_set.all())) if self.parent_set.count(): profiles.append(list(self.parent_set.all())) return profiles profiles = property(_getProfiles) class BaseProfile(models.Model): person = models.ForeignKey(Person) is_default = models.BooleanField(default=False) class Meta: abstract = True class Teacher(BaseProfile): user_type = models.CharField(max_length=7, default="teacher") class Student(BaseProfile): user_type = models.CharField(max_length=7, default="student") class Parent(BaseProfile): user_type = models.CharField(max_length=7, default="parent")

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• How to determine the data type of a CvMat

  - by Chris

  When using the CvMat type, the type of data is crucial to keeping your program running. For example, depending on whether your data is type float or unsigned char, you would choose one of these two commands: cvmGet(mat, row, col); cvGetReal2D(mat, row, col); Is there a universal approach to this? If the wrong data type matrix is passed to these calls, they crash at runtime. This is becoming an issue, since a function I have defined is getting passed several different types of matrices. How do you determine the data type of a matrix so you can always access its data? I tried using the "type()" function as such. CvMat* tmp_ptr = cvCreateMat(t_height,t_width,CV_8U); std::cout << "type = " << tmp_ptr->type() << std::endl; This does not compile, saying "term does not evaluate to a function taking 0 arguments". If I remove the brackets after the word type, I get a type of 1111638032 EDIT minimal application that reproduces this... int main( int argc, char** argv ) { CvMat *tmp2 = cvCreateMat(10,10, CV_32FC1); std::cout << "tmp2 type = " << tmp2->type << " and CV_32FC1 = " << CV_32FC1 << " and " << (tmp2->type == CV_32FC1) << std::endl; } Output: tmp2 type = 1111638021 and CV_32FC1 = 5 and 0

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• Maintaining state and data context between requests in ASP.NET + EF4

  - by Nick

  I have a EF4/ASP.NET web application that is structured to use POCOs and generic repositories, based essentially on this excellent article. The application is relatively sophisticated with one page that involves selection and linking of multiple entities to build up a complex user profile. This requires access to multiple entity types (20 or so) and associated repositories across multiple posts. When a repository is first accessed it uses the existing data context if exists, else it creates a new context. The problem is that if the lifetime of the context is only per-request (as suggested in the article) then you have to deal with multiple contexts and the complexity around detaching and attaching entities from contexts. My solution is to share the context between posts by creating a single View Model that includes all required repositories (initialised to share the same context) plus any associated data and store this model in a Session variable, retrieving from Session on subsequent page requests. Therefore maintaining the same context across all posts until the profile is saved. This works fine BUT I am concerned that I don't actually know exactly what is stored in the model session variable or more importantly the size of the Session variable. So two questions I suppose: firstly should I look for a better solution to handle the shared context across posts issue (any suggestions welcome)? And secondly what is actually stored in the Session when it includes a repository plus context? Any help appreciated!

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• How do I show information to users belonging to different groups (web) in modx

  - by Gaurav Sharma

  Hello Everyone, I have created a website using modx evolution v1.0.2. The website that I have developed has 12 different types of users (categorized in groups). Each user will be shown a different price depending on the group to which he belongs. Till now I have been able to fetch the group name of current logged in user (created a snippet for that), but how can I achieve the above mentioned functionality so that each user should be able to see only the price that I have coded according to his group. For example: If a user is associated with the 'ocassional' group then he should be shown the price as , say, 50 bucks and if a user is associated with the 'regular' group then he should be shown the price as, say, 40 bucks I can easily do this by coding a single snippet for every product's variant, but there are a lot of variants (more than 100 and growing). I have created a resource(page) for every product and it's variant. Every variant has a price. It is this price that I want to be shown according to the logged in user group membership. I hope I am able to explain my query clearly. Please help me do this functionality. Thanks

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• Why use INCLUDE in a SQL index

  - by StarLite

  I recently encountered an index in a database I maintain that was of the form: CREATE INDEX [IX_Foo] ON [Foo] ( Id ASC ) INCLUDE ( SubId ) In this particular case, the performance problem that I was encountering (a slow SELECT filtering on both Id and SubId) could be fixed by simply moving the SubId column into the index proper rather than as an included column. This got me thinking however that I don't understand the reasoning behind included columns at all, when generally, they could simply be a part of the index itself. Even if I don't particularly care about the items being in the index itself is there any downside to having column in the index rather than simply being included. After some research, I am aware that there are a number of restrictions on what can go into an indexed column (maximum width of the index, and some column types that can't be indexed like 'image'). In these cases I can see that you would be forced to include the column in the index page data. The only thing I can think of is that if there are updates on SubId, the row will not need to be relocated if the column is included (though the value in the index would need to be changed). Is there something else that I'm missing? I'm considering going through the other indexes in the database and shifting included columns in the index proper where possible. Would this be a mistake? I'm primarily interested in MS SQL Server, but information on other DB engines is welcome also.

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• Design suggestion for expression tree evaluation with time-series data

  - by Lirik

  I have a (C#) genetic program that uses financial time-series data and it's currently working but I want to re-design the architecture to be more robust. My main goals are: sequentially present the time-series data to the expression trees. allow expression trees to access previous data rows when needed. to optimize performance of the data access while evaluating the expression trees. keep a common interface so various types of data can be used. Here are the possible approaches I've thought about: I can evaluate the expression tree by passing in a data row into the root node and let each child node use the same data row. I can evaluate the expression tree by passing in the data row index and letting each node get the data row from a shared DataSet (currently I'm passing the row index and going to multiple synchronized arrays to get the data). Hybrid: an immutable data set is accessible by all of the expression trees and each expression tree is evaluated by passing in a data row. The benefit of the first approach is that the data row is being passed into the expression tree and there is no further query done on the data set (which should increase performance in a multithreaded environment). The drawback is that the expression tree does not have access to the rest of the data (in case some of the functions need to do calculations using previous data rows). The benefit of the second approach is that the expression trees can access any data up to the latest data row, but unless I specify what that row is, I'll have to iterate through the rows and figure out which one is the last one. The benefit of the hybrid is that it should generally perform better and still provide access to the earlier data. It supports two basic "views" of data: the latest row and the previous rows. Do you guys know of any design patterns or do you have any tips that can help me build this type of system? Should I use a DataSet to hold and present the data, or are there more efficient ways to present rows of data while maintaining a simple interface? FYI: All of my code is written in C#.

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• Is it approproate it use django signals withing the same app

  - by Alex Lebedev

  Trying to add email notification to my app in the cleanest way possible. When certain fields of a model change, app should send a notification to a user. Here's my old solution: from django.contrib.auth import User class MyModel(models.Model): user = models.ForeignKey(User) field_a = models.CharField() field_b = models.CharField() def save(self, *args, **kwargs): old = self.__class__.objects.get(pk=self.pk) if self.pk else None super(MyModel, self).save(*args, **kwargs) if old and old.field_b != self.field_b: self.notify("b-changed") # Sevelar more events here # ... def notify(self, event) subj, text = self._prepare_notification(event) send_mail(subj, body, settings.DEFAULT_FROM_EMAIL, [self.user.email], fail_silently=True) This worked fine while I had one or two notification types, but after that just felt wrong to have so much code in my save() method. So, I changed code to signal-based: from django.db.models import signals def remember_old(sender, instance, **kwargs): """pre_save hanlder to save clean copy of original record into `old` attribute """ instance.old = None if instance.pk: try: instance.old = sender.objects.get(pk=instance.pk) except ObjectDoesNotExist: pass def on_mymodel_save(sender, instance, created, **kwargs): old = instance.old if old and old.field_b != instance.field_b: self.notify("b-changed") # Sevelar more events here # ... signals.pre_save.connect(remember_old, sender=MyModel, dispatch_uid="mymodel-remember-old") signals.post_save.connect(on_mymodel_save, sender=MyModel, dispatch_uid="mymodel-on-save") The benefit is that I can separate event handlers into different module, reducing size of models.py and I can enable/disable them individually. The downside is that this solution is more code and signal handlers are separated from model itself and unknowing reader can miss them altogether. So, colleagues, do you think it's worth it?

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• stat() get group name is root

  - by mengmenger

  I have a file src.tar.gz whoes owner and group are named "src". When I run test.c compiled with name "test" (permission: -rwsr-xr-x owner:root group:staff) The way I run it: I am running it as group member under "src" group. But I run "test" as root since "test" permission is -rwsr-xr-x Question: Why did result come out like this? is the src.tar.gz group should be "src"? Output: Error: my group: src Error: src.tar.gz group is root test.c #include <stdio.h> #include <stdlib.h> #include <unistd.h> #include <string.h> #include <sys/types.h> #include <sys/stat.h> #include <grp.h> void main(int ac, char **args) { const char *ERR_MSG_FORMAT = "%s: %s %s.\n"; char *ptr_source_file = "src.tar.gz"; struct stat src_stat; gid_t src_gid, my_gid; int i = stat(ptr_source_file, &src_stat); my_gid = getgid(); struct group *cur_gr = getgrgid(my_gid); fprintf(stderr, ERR_MSG_FORMAT, "Error", "my group: ", cur_gr->gr_name); src_gid = src_stat.st_gid; struct group *src_gr = getgrgid(src_gid); fprintf(stderr, ERR_MSG_FORMAT, "Error","src.tar.gz group is ", src_gr->gr_name); }

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• invalid argument IE7 javascript line number changes

  - by Lauren

  This is the test page: http://www.onebagoneearth.com/ OBOEKindBag (spaces between the pagename and domain because I don't want the URL indexed as such) If you click on one of the thumbnails, or on the main image, you see a popup window, and if you enter a quantity and then click "add to cart" here, in IE7 (and IE6, but I'm not focusing on that as much), you see an invalid argument error with Code:0. The line # changes depending on which item you add to cart! The URL also changes because it depends on this line of javascript: var cartUrl = "/app/site/backend/additemtocart.nl?c=659197&n=2&buyid=" + zbuyid + "&qty=" + zqty + "&" + strOptionId + "=" + zitmId . The strOptionId variable, which contains the bag color type (ie. this changes for the different types of bags, like Kind bags, regular OBOE bags), and the zitmID variable which contains the particular bag color that you've selected (ie. Black), are what change, and also what seem to affect the line number that the invalid argument occurs on. The error definitely doesn't occur in Chrome 4, IE 8, or FF 3.5. Ideas?

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• 406 Not Acceptable error when using Jquery $.post in Firefox but not in Safari or Chrome

  - by jlfenaux

  I'm using Jquery (1.3.2) $.post command to trigger an ajax call to a rails server. The code works great on Safari and on Google Chrome (mac), but when I tried it on Firefox (3.5.7), I got a weird '406 Not Acceptable' error. When I look at the headers, it Firefox indicated that it accepted only ' text/javascript' responses. And the response Content-Type was 'text/html; charset=utf-8'. In Chrome the accepted types were 'application/json, text/javascript, /, text/javascript' and the response Content-Type was 'application/json; charset=utf-8'. I tried to force the content type in rails to 'text/javascript' format.json do render :json => @races.to_json, :content_type => 'text/javascript' end The content type is indeed changed in Chrome, but not in Firefox where it remains 'text/html'. Here is the code I used to trigger the ajax call. $.post( "/locator", params, function(data){...}, "json" ); Is there something I can do to make this work in Firefox? Thanks

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