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• How to handle Many-To-Many In Grails without belongsTo?

  - by nute

  I need to create a many-to-many relationship in Grails. I have a "Question" domain and a "Tag" domain. A Question can have 0 or more tags. A Tag can have 0 or more Questions. If I put a "hasMany" on each sides, it gives me an error saying I need a "belongTo" somewhere. However, adding a belongsTo means that the owner must exist... Like I said, a Tag could have 0 questions, and a Question could have 0 tags. There is no concept of an owner, it's a many-to-many! What am I supposed to do?

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• Manipulating both unicode and ASCII character set in C#

  - by Murlex

  I have this mapping in my C# application string [,] unicode2Ascii = { { "&#3001;", "\x86" } }; ஹ - is the unicode value for a tamil literal "ஹ". This is the raw hex literal for the unicode value saved by MS Word as a byte sequence. I am trying to map these unicode value "strings" to a hex value under 255 (so as to accommodate non-unicode supported systems). I trying to use string.replace like this: S = S.replace(unicode2Ascii[0,0], unicode2Ascii[0,1]); However the resultant ouput has a ? instead of the actual hex 0x86 stored. Any pointer on how I could set the encoding for the second element of that array to something like windows-1252? Or is there a better way to do this conversion? thanks in advance

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• What are the differences between MVP, Presentation Model, MVVM and MVC?

  - by Nicholas

  I have a pretty good idea how each of these patterns work some of the minor differences between them, but are they really all that different from each other? It seems to me that the Presenter, Presentation Model, ViewModel and Controller are essentially the same concept. Why couldn't I classify all of these concepts as controllers? I feel like it might simplify the entire idea a great deal. Can anyone give a clear description of their differences? I want to clarify that I do understand how the patterns work, and have implemented most of them in one technology or another. What I am really looking for is someone's experience with one of these patterns, and why they would not consider their ViewModel a controller for instance.

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• Significance of date 02/31/2157?

  - by dpatchery

  I work in a large scale IT support environment. Twice now we have seen an invalid date of 02/31/2157 being inserted in an Oracle DATE column. So far I have not been able to reproduce this problem, but it appears to be happening occasionally when a user attempts to save '00/00/0000' into the column. I believe the value is originating from a PowerBuilder DataWindow update. The application uses myriad libraries for all sorts of technologies, so this question may be a bit vague, but... Has anyone seen the date 02/31/2157 in some established library that Oracle could be defaulting to when some other invalid date is entered? Perhaps an end-of-time concept analogous to the beginning-of-time date of 1/1/1970?

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• Is a full list returned first and then filtered when using linq to sql to filter data from a databas

  - by RJ

  This is probably a very simple question that I am working through in an MVC project. Here's an example of what I am talking about. I have an rdml file linked to a database with a table called Users that has 500,000 rows. But I only want to find the Users who were entered on 5/7/2010. So let's say I do this in my UserRepository: from u in db.GetUsers() where u.CreatedDate = "5/7/2010" select u (doing this from memory so don't kill me if my syntax is a little off, it's the concept I am looking for) Does this statement first return all 500,000 rows and then filter it or does it only bring back the filtered list?

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• mysql update too slow when joining multiple tables

  - by user293487

  Hi, I have two tables. they looks like as follows: Id (int) Tags char(128). the column Tags in table A does not have value. It is empty. The column Tags in table B has value. What I want to copy the Tags in table B to corresponding place of table A. the mapping is based on Id. My sql query is: update A INNER JOIN B set A.Tags = B.Tags where A.Id = B.Id There are about 2,000,000 rows in table A, and 50,000 rows in table B. The update seems very slow.... Could anyone tell me how to make it run faster?

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• What are good uses for Python3's "Function Annotations"

  - by agscala

  Function Annotations: PEP-3107 I ran across a snippet of code demonstrating Python3's function annotations. The concept is simple but I can't think of why these were implemented in Python3 or any good uses for them. Perhaps SO can enlighten me? How it works: def foo(a: 'x', b: 5 + 6, c: list) -> max(2, 9): ... function body ... Everything following the colon after an argument is an 'annotation', and the information following the -> is an annotation for the function's return value. foo.func_annotations would return a dictionary: {'a': 'x', 'b': 11, 'c': list, 'return': 9} What's the significance of having this available?

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• How to access the backing field of a base class using fluent nhibernate?

  - by Akk

  How do i set the Access Strategy in the mapping class to point to the base _photos field? public class Content { private IList<Photo> _photos; public Content() { _photos = new List<Photo>(); } public virtual IEnumerable<Photo> Photos { get { return _photos; } } public virtual void AddPhoto() {...} } public class Article : Content { public string Body {get; set;} } I am currently using the following to try and locate the backing field but an exception is thrown as it cannot be found. public class ArticleMap : ClassMap<Article> { HasManyToMany(x => x.Photos) .Access.CamelCaseField(Prefix.Underscore) //_photos //... } i tried moving the backing field _photos directly into the class and the access works. So how can i access the backing field of the base class?

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• Where's the definitive resource online about how to carry out Agile development?

  - by jdk

  I want to start Agile practices in a team. I'm assuming the information is available for free online about how to specifically carry it out. Online I can locate the manifesto, the alliances and corporations involved but where is the actual central guide or root instruction set about how to do it? (Maybe the practices themselves are more ethereal or subjective than I expect and it's found in multiple places?) Edit to summarize solutions: Agile is a concept so that's what's to be found online about it. However specific processes or methods of Agile development have been created like Scrum and Extreme programming to provide concrete solutions to teams who want to adopt Agile and reap its proposed benefits. Find the shoe (or method) that fits best. Maybe create it. If looking for solutions online to implement Agile development in your organization or for your project, seek out the specific methods too and decide among them.

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• Hibernate - why use many-to-one to represent a one-to-one?

  - by aberrant80

  I've seen people use many-to-one mappings to represent one-to-one relationships. I've also read this in a book by Gavin King and on articles. For example, if a customer can have exactly one shipping address, and a shipping address can belong to only one customer, the mapping is given as: <class name="Customer" table="CUSTOMERS"> ... <many-to-one name="shippingAddress" class="Address" column="SHIPPING_ADDRESS_ID" cascade="save-update" unique="true"/> ... </class> The book reasons as (quoting it): "You don't care what's on the target side of the association, so you can treat it like a to-one association without the many part." My question is, why use many-to-one and not one-to-one? What is it about a one-to-one that makes it a less desirable option to many-to-one? Thanks.

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• What is this project/compilation source structure?

  - by Werner

  Hi, I am working on some project my boss sent to me. After unzipping, this is the structure of the files: executable_file config.mk doc include lib Makefile sources I have only worked with "usual" Makefile projects. But I do not undersatnd the meaning of config.mk here. Do you know which kind of "build" structure (what is the right name for this concept?) is it, and where can i find more information about this? I need to modify it, so it compiles in another hardware, so I do not know where I sohuld work on. Thanks

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• How to get the line number an xml element is on via the Java w3c dom api

  - by Benju

  Is there a way to lookup the line number that a given element is at in an xml file via the w3c dom api? My use case for this is that we have 30,000+ maps in kml/xml format. I wrote a unit test that iterates over each file found on the hard drive (about 17GB worth) and tests that it is parseable by our application. When it fails I throw an exception that contains the element instance that was considered "invalid". In order for our mapping department (nobody here knows how to program) to easily track down the typo we would like to log the line number of the element that caused the exception. Can anybody suggest a way to do this? Please note we are using the W3C dom api included in the Android 1.6 SDK.

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• User controlled html title tags

  - by zaf

  What are the best practices for allowing a user to maintain the html title tags of all the major pages of his/her site? One way could be to allow the mapping of URLs to some text. For example, we have an app with the following (most complex) url format: http://lang.example.com/searchpage.zaf?a=foo&b=bar&c=RANDOM There are several parts to this: Language sub domain Search page Static parameter 'a' (user may want this in the title) Dynamic and relevant parameter 'b' (user may want this in the title) Dynamic parameter 'c' which can be ignored Never done this before, so I'm asking how you would tackle this!

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• UDP + total order, non-reliable

  - by disown

  I'm trying to find a version of UDP which just alleviates the restriction of a maximum size of the message sent. I don't care about reliability or partial retransmission, if all chunks arrive I want the message to be assembled from the chunks in sending order and delivered to the listening app. If one or more chunks are missing I would just like to discard the message. The goal is to have a low-latency notification mechanism about real time data, but with the added support for bigger messages than what would fit in an IP datagram. I would like the protocol to be one way only, and not have long connection setup times. An optional feature to be able to respond to a received message wouldn't hurt (a concept of an unreliable connection), but is not necessary.

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• geom_rect and NULL

  - by csgillespie

  I've been looking at the geom_rect example in section 5.10 of the ggplot2 book and don't understand the purpose of the NULL's in the aes function. For example, using the mpg data: g = ggplot(data=mpg, aes(x=displ, y=hwy)) + geom_point() #Produces a plot with a transparent filled region g + geom_rect(aes(NULL, NULL), alpha=0.1,xmin=5, xmax=7, ymin=10, ymax=45, fill="blue") #Solid filled region (v0.9) or nothing in v0.8 g + geom_rect(alpha=0.1,xmin=5, xmax=7, ymin=10, ymax=45, fill="blue") My understanding is that the NULL's are resetting the x & y mapping, but I don't see why this should affect the transparency.

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• Keeping historic of modification in a database.

  - by mada

  Hi, Im a j2ee developper & we are using hibernatne mapping with a postgres databasae. We have to keep track of any changes occurs in the databse , in others words alls previous & current value of any field should be saved & field can be various types (bytea, int, char...) With a simple table it is easy but we a graph of objets things are more difficult So we have , speaking in a UML point of view, a graph of objects to store in the database with every changes & the user. Any idea or pattern how to do that ? Thanks in advance.

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• EntityFramework how to Override properties

  - by plotnick

  I've just started using EF in VS2010. That thing is just amazin'. I frankly can't understand something. For example I have EntityType with property, they generated from database structure. Now, I have to simply override that property in my code. I don't need to save value of the property back into DB, but everytime when it gets read from DB it should be substituted with run-time calculated value. Of course I can create derived class based on my EntityType but I've tried and found kinda difficulties, I'm not sure this is kinda right way to do. Anyway even when I try to change the whole EntityType to Abstract, damn Visual Studio doesn't want to validate that and says something like: "Error 2078: The EntityType 'AssetsModel.Asset' is Abstract and can be mapped only using IsTypeOf." "Error 2063: At least one property must be mapped in the set mapping for 'Assets'" What the hell is this suppose to mean I dunno.. Any ideas gentlemen?

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• Hibernate inserting into join table

  - by Karl

  I got several entities. Two of them got a many-to-many relation. When I do a bigger operation on these entities it fails with this exception: org.hibernate.exception.ConstraintViolationException: could not insert collection rows: I execute the operation i a @Transactional context. I don't do any explicit flushing i my daos. The flush is triggered by a query. In the queue are 15 elements (all of the same structure). one of them always fails (but it's always a different one (I checked) and always at a different position). Does anybody have a hint for me for what I might do wrong? My Mapping: @ManyToMany(targetEntity = CategoryImpl.class) protected Set<Category> categories = new HashSet<Category>();

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• jquery not working in mvc after publishing to server

  - by czuroski

  Hello, I've built an mvc application which contains some jquery code. When I run the app from my ide, everything works perfectly. When I publish to the server and open the page, the jquery does not work. I get object expected errors. Could this be due to my file mappings? here is a sample of my mapping in the app - <script type="text/javascript" href="../../Scripts/jquery-1.3.2.js"></script> I published the app to iis7 successfully, but the jquery is broken. I did publish to an application within an existing web site. Any thoughts?

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• Fluent NHibernate CheckProperty and Dates

  - by Chris C

  I setup a NUnit test as such: new PersistenceSpecification<MyTable>(_session) .CheckProperty(c => c.ActionDate, DateTime.Now); When I run the test via NUnit I get the following error: SomeNamespace.MapTest: System.ApplicationException : Expected '2/23/2010 11:08:38 AM' but got '2/23/2010 11:08:38 AM' for Property 'ActionDate' The ActionDate field is a datetime field in a SQL 2008 database. I use Auto Mapping and declare the ActionDate as a DateTime property in C#. If I change the test to use DateTime.Today the tests pass. My question is why is the test failing with DateTime.Now? Is NHibernate losing some precision when saving the date to the database and if so how do prevent the lose? Thank you.

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• Accessing items from a dictionary using pickle efficiently in Python

  - by user248237

  I have a large dictionary mapping keys (which are strings) to objects. I pickled this large dictionary and at certain times I want to pull out only a handful of entries from it. The dictionary has usually thousands of entries total. When I load the dictionary using pickle, as follows: from cPickle import * # my dictionary from pickle, containing thousands of entries mydict = open(load('mypickle.pickle')) # accessing only handful of entries here for entry in relevant_entries: # find relevant entry value = mydict[entry] I notice that it can take up to 3-4 seconds to load the entire pickle, which I don't need, since I access only a tiny subset of the dictionary entries later on (shown above.) How can I make it so pickle only loads those entries that I have from the dictionary, to make this faster? Thanks.

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• Dynamic Custom Fields for Data Model

  - by Jerry Deng

  I am in the process of creating a dynamic database where user will be able to create resource type where he/she can add custom fields (multiple texts, strings, and files) Each resource type will have the ability to display, import, export its data; I've been thinking about it and here are my approaches. I would love to hear what do you guys think. Ideas: just hashing all the custom data in a data field (pro: writing is easier, con: reading back out may be harder); children fields (the model will have multiple fields of strings, fields of text, and fields for file path); fixed number of custom fields in the same table with a key mapping data hash stored in the same row; Non-SQL approach, but then the problem would be generating/changing models on the fly to work with different custom fields;

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• How to use TestAndSet() for solving the critical section problem?

  - by Dan Mantyla

  I'm studying for an exam and I'm having difficulty with a concept. This is the pseudo code I am given: int mutex = 0; do { while (TestAndSet(&mutex)); // critical section mutiex = 0; // remainder section } while (TRUE); My instructor says that only two of the three necessary conditions (mutual exclusion, progress, and bounded waiting) are met with this code, but I don't understand which one isn't being met...?? How should the code be modified to support the missing condition to solve the critical region problem? Thanks in advance for any insight!

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• in .net, what programming model would be good for prototyping, but then reusable for production (for

  - by Greg

  Hi, In .NET land what would be a good approach for quick prototyping of a concept (i.e. development just on my PC) that could then be extended out to product (users across LAN/WAN), BUT in a fashion that the model/business logic code and data access layer code can be used as is? One thought for example I had as to do: (a) WinForms with business logic and Entity Framework layer to SQL Server Express on my PC, then (b) Go then to ASP.net (using the business logic / data library) with SQL Server/IIS Any comments? Other suggestions?

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• How to organise a many to many relationship in MongoDB

  - by Gareth Elms

  I have two tables/collections; Users and Groups. A user can be a member of any number of groups and a user can also be an owner of any number of groups. In a relational database I'd probably have a third table called UserGroups with a UserID column, a GroupID column and an IsOwner column. I'm using MongoDB and I'm sure there is a different approach for this kind of relationship in a document database. Should I embed the list of groups and groups-as-owner inside the Users table as two arrays of ObjectIDs? Should I also store the list of members and owners in the Groups table as two arrays, effectively mirroring the relationship causing a duplication of relationship information? Or is a bridging UserGroups table a legitimate concept in document databases for many to many relationships? Thanks

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