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  • nHibernate storage of an object with self referencing many children and many parents

    - by AdamC
    I have an object called MyItem that references children in the same item. How do I set up an nhibernate mapping file to store this item. public class MyItem { public virtual string Id {get;set;} public virtual string Name {get;set;} public virtual string Version {get;set;} public virtual IList<MyItem> Children {get;set;} } So roughly the hbm.xml would be: <class name="MyItem" table="tb_myitem"> <id name="Id" column="id" type="String" length="32"> <generator class="uuid.hex" /> </id> <property name="Name" column="name" /> <property name="Version" column="version" /> <bag name="Children" cascade="all-delete-orphan" lazy="false"> <key column="children_id" /> <one-to-many class="MyItem" not-found="ignore"/> </bag> </class> This wouldn't work I don't think. Perhaps I need to create another class, say MyItemChildren and use that as the Children member and then do the mapping in that class? This would mean having two tables. One table holds the MyItem and the other table holds references from my item. NOTE: A child item could have many parents.

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  • Binding value for NSTableView, but tooltip gets set as well

    - by Mark
    I've set up an NSTableView in Interface Builder to be populated from an NSArray. Each value of the array represents one row in the table. The value is bound correctly, but as a side effect, the table cell's tooltip is set to the string representation of the bound object. In my case, the NSArray contains NSDictiorany objects and the tooltip looks like it could be the [... description] output of that dictionary. Very ugly... I don't want the tooltip to be set at all. I have other tables that have plain NSString values bound to them and they don't have a tooltip set automatically. Is there some Interface Builder magic going on? I tried to start with a blank project - same problem. I should add that the table cell is a custom implementation of NSTextFieldCell that uses an NSButtonCell instance to draw an image and a label into the table. The values are retrieved from the dictionary bound as value. Why is the tooltip set when I only bind the "value" attribute? Thanks in advance!

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  • Managing libraries and imports in a programming language

    - by sub
    I've created an interpreter for a stupid programming language in C++ and the whole core structure is finished (Tokenizer, Parser, Interpreter including Symbol tables, core functions, etc.). Now I have a problem with creating and managing the function libraries for this interpreter (I'll explain what I mean with that later) So currently my core function handler is horrible: // Simplified version myLangResult SystemFunction( name, argc, argv ) { if ( name == "print" ) { if( argc < 1 ) { Error('blah'); } cout << argv[ 0 ]; } else if ( name == "input" ) { if( argc < 1 ) { Error('blah'); } string res; getline( cin, res ); SetVariable( argv[ 0 ], res ); } else if ( name == "exit ) { exit( 0 ); } And now think of each else if being 10 times more complicated and there being 25 more system functions. Unmaintainable, feels horrible, is horrible. So I thought: How to create some sort of libraries that contain all the functions and if they are imported initialize themselves and add their functions to the symbol table of the running interpreter. However this is the point where I don't really know how to go on. What I wanted to achieve is that there is e.g.: an (extern?) string library for my language, e.g.: string, and it is imported from within a program in that language, example: import string myString = "abcde" print string.at( myString, 2 ) # output: c My problems: How to separate the function libs from the core interpreter and load them? How to get all their functions into a list and add it to the symbol table when needed? What I was thinking to do: At the start of the interpreter, as all libraries are compiled with it, every single function calls something like RegisterFunction( string namespace, myLangResult (*functionPtr) ); which adds itself to a list. When import X is then called from within the language, the list built with RegisterFunction is then added to the symbol table. Disadvantages that spring to mind: All libraries are directly in the interpreter core, size grows and it will definitely slow it down.

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  • Exit and rollback everything in script on error

    - by Jan W.
    Hey guys ! I'm in a bit of a pickle here. I have a TSQL script that does a lot of database structure adjustments but it's not really safe to just let it go through when something fails. to make things clear: using MS SQL 2005 it's NOT a stored procedure, just a script file (.sql) what I have is something in the following order BEGIN TRANSACTION ALTER Stuff GO CREATE New Stuff GO DROP Old Stuff GO IF @@ERROR != 0 BEGIN PRINT 'Errors Found ... Rolling back' ROLLBACK TRANSACTION RETURN END ELSE PRINT 'No Errors ... Committing changes' COMMIT TRANSACTION just to illustrate what I'm working with ... can't go into specifics now, the problem ... When I introduce an error (to test if things get rolled back), I get a statement that the ROLLBACK TRANSACTION could not find a corresponding BEGIN TRANSACTION. This leads me to believe that something when REALLY wrong and the transaction was already killed. what I also noticed is that the script didn't fully quit on error and thus DID try to execute every statement after the error occured. (I noticed this when new tables showed up when I wasn't expecting them because it should have rollbacked) any help in this department is welcome if more speficics are needed, ask! greetz

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  • CakePHP: Need help using saveField to update a fields in a belongsTo model

    - by afrisch
    I am trying to update a password into two different models/tables in CakePHP. I can update it fine in the parent model, but not the second model. Models: Users (hasOne GameProfile) PK=id Gameprofiles (belongsTo User) FK=user_id Here is a stripped down version of my function in the Users_controller.php: function updatepass() { if (!empty($this->data)) { $this->User->id = $this->Auth->user('id'); $this->User->saveField('sha1password', $this->Auth->password($this->data['User']['newpass'])); $this->User->Gameprofile->saveField('plainpassword', $this->data['User']['newpass']); } } When I execute the function, the users table is updated fine. But the gameprofile table is not updated, rather Cake does an insert. SQL Query Log: 1195 Query UPDATE `users` SET `sha1password` = 'e9443e9f5e1a07832aad1b2f84de1a666daf89b5' WHERE `users`.`id` = 30 1195 Query INSERT INTO `gameprofiles` (`plainpassword`) VALUES ('abc') Is there a way to get CakePHP to do an update using saveField on a model with a belongsTo attribute? I've tried various ways to refer to user_id before executing the second saveField, but just can't seem to find the winning combination. Any help is greatly appreciated!

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  • ASP.Net MVC - how can I easily serialize query results to a database?

    - by Mortanis
    I've been working on a little property search engine while I learn ASP.Net MVC. I've gotten the results from various property database tables and sorted them into a master generic property response. The search form is passed via Model Binding and works great. Now, I'd like to add pagination. I'm returning the chunk of properties for the current page with .Skip() and .Take(), and that's working great. I have a SearchResults model that has the paged result set and various other data like nextPage and prevPage. Except, I no longer have the original form of course to pass to /Results/2. Previously I'd have just hidden a copy of the form and done a POST each time, but it seems inelegant. I'd like to serialize the results to my MS SQL database and return a unique key for that results set - this also helps with a "Send this query to a friend!" link. Killing two birds with one stone. Is there an easy way to take an IQueryable result set that I have, serialize it, stick it into the DB, return a unique key and then reverse the process with said key? I'm using Linq to SQL currently on a MS SQL Express install, though in production it'll be on MS SQL 2008.

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  • How Optimize sql query make it faster

    - by user502083
    Hello every one : I have a very simple small database, 2 of tables are: Node (Node_ID, Node_name, Node_Date) : Node_ID is primary key Citation (Origin_Id, Target_Id) : PRIMARY KEY (Origin_Id, Target_Id) each is FK in Node Now I write a query that first find all citations that their Origin_Id has a specific date and then I want to know what are the target dates of these records. I'm using sqlite in python the Node table has 3000 record and Citation has 9000 records, and my query is like this in a function: def cited_years_list(self, date): c=self.cur try: c.execute("""select n.Node_Date,count(*) from Node n INNER JOIN (select c.Origin_Id AS Origin_Id, c.Target_Id AS Target_Id, n.Node_Date AS Date from CITATION c INNER JOIN NODE n ON c.Origin_Id=n.Node_Id where CAST(n.Node_Date as INT)={0}) VW ON VW.Target_Id=n.Node_Id GROUP BY n.Node_Date;""".format(date)) cited_years=c.fetchall() self.conn.commit() print('Cited Years are : \n ',str(cited_years)) except Exception as e: print('Cited Years retrival failed ',e) return cited_years Then I call this function for some specific years, But it's crazy slowwwwwwwww :( (around 1 min for a specific year) Although my query works fine, it is slow. would you please give me a suggestion to make it faster? I'd appreciate any idea about optimizing this query :) I also should mention that I have indices on Origin_Id and Target_Id, so the inner join should be pretty fast, but it's not!!!

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  • How do I rescue a small portion of data from a SQL Server database backup?

    - by Greg
    I have a live database that had some data deleted from it and I need that data back. I have a very recent copy of that database that has already been restored on another machine. Unrelated changes have been made to the live database since the backup, so I do not want to wipe out the live database with a full restore. The data I need is small - just a dozen rows - but those dozen rows each have a couple rows from other tables with foreign keys to it, and those couple rows have god knows how many rows with foreign keys pointing to them, so it would be complicated to restore by hand. Ideally I'd be able to tell the backup copy of the database to select the dozen rows I need, and the transitive closure of everything that they depend on, and everything that depends on them, and export just that data, which I can then import into the live database without touching anything else. What's the best approach to take here? Thanks. Everyone has mentioned sp_generate_inserts. When using this, how do you prevent Identity columns from messing everything up? Do you just turn IDENTITY INSERT on?

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  • MySQL query puzzle - finding what WOULD have been the most recent date

    - by Hank
    I've looked all over and haven't yet found an intelligent way to handle this, though I feel sure one is possible: One table of historical data has quarterly information: CREATE TABLE Quarterly ( unique_ID INT UNSIGNED NOT NULL, date_posted DATE NOT NULL, datasource TINYINT UNSIGNED NOT NULL, data FLOAT NOT NULL, PRIMARY KEY (unique_ID)); Another table of historical data (which is very large) contains daily information: CREATE TABLE Daily ( unique_ID INT UNSIGNED NOT NULL, date_posted DATE NOT NULL, datasource TINYINT UNSIGNED NOT NULL, data FLOAT NOT NULL, qtr_ID INT UNSIGNED, PRIMARY KEY (unique_ID)); The qtr_ID field is not part of the feed of daily data that populated the database - instead, I need to retroactively populate the qtr_ID field in the Daily table with the Quarterly.unique_ID row ID, using what would have been the most recent quarterly data on that Daily.date_posted for that data source. For example, if the quarterly data is 101 2009-03-31 1 4.5 102 2009-06-30 1 4.4 103 2009-03-31 2 7.6 104 2009-06-30 2 7.7 105 2009-09-30 1 4.7 and the daily data is 1001 2009-07-14 1 3.5 ?? 1002 2009-07-15 1 3.4 && 1003 2009-07-14 2 2.3 ^^ then we would want the ?? qtr_ID field to be assigned '102' as the most recent quarter for that data source on that date, and && would also be '102', and ^^ would be '104'. The challenges include that both tables (particularly the daily table) are actually very large, they can't be normalized to get rid of the repetitive dates or otherwise optimized, and for certain daily entries there is no preceding quarterly entry. I have tried a variety of joins, using datediff (where the challenge is finding the minimum value of datediff greater than zero), and other attempts but nothing is working for me - usually my syntax is breaking somewhere. Any ideas welcome - I'll execute any basic ideas or concepts and report back.

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  • MS Excel automation without macros in the generated reports. Any thoughts?

    - by ezeki77
    Hello! I know that the web is full of questions like this one, but I still haven't been able to apply the answers I can find to my situation. I realize there is VBA, but I always disliked having the program/macro living inside the Excel file, with the resulting bloat, security warnings, etc. I'm thinking along the lines of a VBScript that works on a set of Excel files while leaving them macro-free. Now, I've been able to "paint the first column blue" for all files in a directory following this approach, but I need to do more complex operations (charts, pivot tables, etc.), which would be much harder (impossible?) with VBScript than with VBA. For this specific example knowing how to remove all macros from all files after processing would be enough, but all suggestions are welcome. Any good references? Any advice on how to best approach external batch processing of Excel files will be appreciated. Thanks! PS: I eagerly tried Mark Hammond's great PyWin32 package, but the lack of documentation and interpreter feedback discouraged me.

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  • C programming - How to print numbers with a decimal component using only loops?

    - by californiagrown
    I'm currently taking a basic intro to C programming class, and for our current assignment I am to write a program to convert the number of kilometers to miles using loops--no if-else, switch statements, or any other construct we haven't learned yet are allowed. So basically we can only use loops and some operators. The program will generate three identical tables (starting from 1 kilometer through the input value) for one number input using the while loop for the first set of calculations, the for loop for the second, and the do loop for the third. I've written the entire program, however I'm having a bit of a problem with getting it to recognize an input with a decimal component. Here is what I have for the while loop conversions: #include <stdio.h> #define KM_TO_MILE .62 main (void) { double km, mi, count; printf ("This program converts kilometers to miles.\n"); do { printf ("\nEnter a positive non-zero number"); printf (" of kilometers of the race: "); scanf ("%lf", &km); getchar(); }while (km <= 1); printf ("\n KILOMETERS MILES (while loop)\n"); printf (" ========== =====\n"); count = 1; while (count <= km) { mi = KM_TO_MILE * count; printf ("%8.3lf %14.3lf\n", count, mi); ++count; } getchar(); } The code reads in and converts integers fine, but because the increment only increases by 1 it won't print a number with a decimal component (e.g. 3.2, 22.6, etc.). Can someone point me in the right direction on this? I'd really appreciate any help! :)

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  • Entity Framework POCO objects

    - by Dan
    I'm struggling with understanding Entity Framework and POCO objects. Here's what I'm trying to achieve. 1) Separate the DAL from the Business Layer by having my business layer use an interface to my DAL. Maybe use Unity to create my context. 2) Use Entity Framework inside my DAL. I have a Domain model with objects that reside in my business layer. I also have a database full of tables that doesn't really represent my domain model. I setup Entity Framework and generated POCO objects by using the ADO.NET POCO Generator extension. This gave me an object for each table in my database. Now I want to be able to say context.GetAll<User>(); and have it return a list of my User objects. The User object is in my business layer. Is that possible? Does that make sense or am I totally off and should start over? I'm guessing I need to use the repository pattern to achieve this, but I'm not sure. Can anyone help?

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  • Parse large XML file w/ script or use BioPython API ?

    - by jeremy04
    Hey guys this is my first question on here. I'm trying to make a local copy of the UniprotKB in SQL. The UniprotKB is 2.1GB, and it comes in XML and a special text format used by SwissProt Here are my options: 1) Use a SAX parser (XML) - I chose Ruby, and Nokogiri. I started writing the parser, but my initial reaction: how would I map the XML schema to the SAX parser? 2) BioPython - I already have BioSQL/Biopython installed, which literally created my SQL schema for me, and I was able to successfully insert one SwissProt/Uniprot txt file into the database. I'm running it right now (crosses fingers) on the entire 2.1gb. Here is the code I'm running: from Bio import SeqIO from BioSQL import BioSeqDatabase from Bio import SwissProt server = BioSeqDatabase.open_database(driver = "MySQLdb", user = "root", passwd = "", host="localhost", db = "bioseqdb") db = server["uniprot"] iterator = SeqIO.parse(open("/path/to/uniprot_sprot.dat", "r"), "swiss") db.load(iterator) server.commit() Edit: it's now crashing because the transactions are getting locked (since the tables are Innodb) Error Number: 1205 Lock wait timeout exceeded; try restarting transaction. I'm using MySQL version: 5.1.43 Should I switch my database to Postgrelsql ?

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  • SQLAlchemy Mapping problem

    - by asdvalkn
    Dear Everyone, I am trying to sqlalchemy to correctly map my data. Note that a unified group is basically a group of groups. (One unifiedGroup maps to many groups but each group can only map to one ug). So basically this is the definition of my unifiedGroups: CREATE TABLE `unifiedGroups` ( `ugID` INT AUTO_INCREMENT, `gID` INT NOT NULL, PRIMARY KEY(`ugID`, `gID`), KEY( `gID`) ) ENGINE=MyISAM DEFAULT CHARSET=utf8 ; Note that each row is a ugID, gID tuple. ( I do not know before hand how many gID is per ugID so this is probably the most sensible and simplest method). Definition for my UnifiedGroup class class UnifiedGroup(object): """UnifiedProduct behaves very much like a group """ def __init__(self, ugID): self.ugID=ugID #Added by mapping self.groups=False def __str__(self): return '<%s:%s>' % (self.ugID, ','.join( [g for g in self.groups])) These are my mapping tables: tb_groupsInfo = Table( 'groupsInfo', metadata, Column('gID', Integer, primary_key=True), Column('gName', String(128)), ) tb_unifiedGroups = Table( 'unifiedGroups', metadata, Column('ugID', Integer, primary_key=True), Column('gID', Integer, ForeignKey('groupsInfo.gID')), ) My mapper maps in the following manner: mapper( UnifiedGroup, tb_unifiedGroups, properties={ 'groups': relation( Group, backref='unifiedGroup') }) However, when I tried to do groupInstance.unifiedGroup, I am getting an empty list [], while groupInstance.unifiedGroup.groups returns me an error: AttributeError: 'InstrumentedList' object has no attribute 'groups' Traceback (most recent call last): File "Mapping.py", line 119, in <module> print p.group.unifiedGroup.groups AttributeError: 'InstrumentedList' object has no attribute 'groups' What is wrong?

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  • Is .NET 4.0 just a show?

    - by Will Marcouiller
    I went to a presentation about the .NET Framework and Visual Studio 2010, last night. The topis were: ASP.NET 4 - Some of the new features of ASP.NET 4 More control over ClientID's in WebForms; Output Caching; ... // Some other stuff I don't really remember being more in framework and WinForms world. Entity Framework 2.0 (.NET 4.0) T4 Templates; Domain driven development; Data driven development; Contexts (edmx files); Some of real-world limitations of EF4 (projects with over 70 to 75 tables); Better POCO support, despite there are still these hidden EntityObject and StructuralObject, but used differently in comparison to EF 1.0 so that it doesn't take off your inheritance; Allows to easily choose how to persist the hierarchy into the underlying database; Code only (start working with EF4 directly from your code!); Design by Contract (DbC). The most interesting feature is, and only, as far as I'm concerned, all related to parallelism made easier. Which really works! No additional assembly references to add. In conclusion, I'm far from impressed about .NET Framework 4.0, apart that it makes some things easier to do. But when you're used to make it a way, it doesn't really change much, in my opinion. Is it me who cannot foresee what .NET 4.0 has to offer? What would you guys base your decision on to migrate to .NET 4.0, in a practical way?

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  • The question about the basics of LINQ to SQL working

    - by Alex
    I just started learning LINQ to SQL, and so far I'm impressed with the easy of use and good performance. I used to think that when doing LINQ queries like from Customer in DB.Customers where Customer.Age > 30 select Customer Get all customers from the database ("SELECT * FROM Customers"), move them to the Customers array and then make a search in that Array using .NET methods. This is very inefficient, what if there are hundreds of thousands of customers in the database? Making such big SELECT queries would kill the web application. Now after experiencing how actually fast LINQ to SQL is, I start to suspect that when doing that query I just wrote, LINQ somehow converts it to a SQL Query string SELECT * FROM Customers WHERE Age > 30 And only when necessary it will run the query. So my question is: am I right? And when is the query actually run? The reason why I'm asking is not only because I want to understand how it works in order to build good optimized applications, but because I came across the following problem. I have 2 tables, one of them is Books, the other has information on how many books were sold on certain days. My goal is to select books that had at least 50 sales/day in past 10 days. It's done with this simple query: from Book in DB.Books where (from Sale in DB.Sales where Sale.SalesAmount >= 50 and Sale.DateOfSale >= DateTime.Now.AddDays(-10) select Sale.BookID).Contains(Book.ID) select Book The point is, I have to use the checking part in several queries and I decided to create an array with IDs of all popular books: var popularBooksIDs = from Sale in DB.Sales where Sale.SalesAmount >= 50 and Sale.DateOfSale >= DateTime.Now.AddDays(-10) select Sale.BookID; BUT when I try to do the query now: from Book in DB.Books where popularBooksIDs.Contains(Book.ID) select Book It doesn't work! That's why I think that we can't use thins kinds of shortcuts in LINQ to SQL queries, like we can't use them in real SQL. We have to create straightforward queries, am I right?

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  • Using Memcached in Python/Django - questions.

    - by Thomas
    I am starting use Memcached to make my website faster. For constant data in my database I use this: from django.core.cache import cache cache_key = 'regions' regions = cache.get(cache_key) if result is None: """Not Found in Cache""" regions = Regions.objects.all() cache.set(cache_key, regions, 2592000) #(2592000sekund = 30 dni) return regions For seldom changed data I use signals: from django.core.cache import cache from django.db.models import signals def nuke_social_network_cache(self, instance, **kwargs): cache_key = 'networks_for_%s' % (self.instance.user_id,) cache.delete(cache_key) signals.post_save.connect(nuke_social_network_cache, sender=SocialNetworkProfile) signals.post_delete.connect(nuke_social_network_cache, sender=SocialNetworkProfile) Is it correct way? I installed django-memcached-0.1.2, which show me: Memcached Server Stats Server Keys Hits Gets Hit_Rate Traffic_In Traffic_Out Usage Uptime 127.0.0.1 15 220 276 79% 83.1 KB 364.1 KB 18.4 KB 22:21:25 Can sombody explain what columns means? And last question. I have templates where I am getting much records from a few table (relationships). So in my view I get records from one table and in templates show it and related info from others. Generating page last a few seconds for very small table (<100records). Is it some easy way to cache queries from templates? Have I to do some big structure in my view (with all related tables), cache it and send to template?

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  • Avoid slowdowns while using off-site database

    - by Anders Holmström
    The basic layout of my problem is this: Website (ASP.NET/C#) hosted at a dedicated hosting company (location 1) Company database (SQL Server) with records of relevant data (location 2). Location 1 & 2 connected through VPN. Customer visiting the website and wanting to pull data from the company database. No possibility of changing the server locations or layout (i.e. moving the website to an in-office server isn't possible). What I want to do is figure out the best way to handle the data acces in this case, minimizing the need for time-expensive database calls over the VPN. The first idea I'm getting is this: When a user enters the section of the website needing the DB data, you pull all the needed tables from the database into a in-memory dataset. All subsequent views/updates to the data is done on this dataset. When the user leaves (logout, session timeout, browser closed etc) the dataset gets sent to the SQL server. I'm not sure if this is a realistic solution, and it obviously has some problems. If two web visitors are performing updates on the same data, the one finishing up last will have their changes overwriting the first ones. There's also no way of knowing you have the latest data (i.e. if a customer pulls som info on their projects and we update this info while they are viewing them, they won't see these changes PLUS the above overwriting issue will arise). The other solution would be to somehow aggregate database calls and make sure they only happen when you need them, e.g. during data updates but not during data views. But then again the longer a pause between these refreshing DB calls, the bigger a chance that the data view is out of date as per the problem described above. Any input on the above or some fresh ideas would be most welcome.

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  • Big-O for GPS data

    - by HH
    A non-critical GPS module use lists because it needs to be modifiable, new routes added, new distances calculated, continuos comparisons. Well so I thought but my team member wrote something I am very hard to get into. His pseudo code int k =0; a[][] <- create mapModuleNearbyDotList -array //CPU O(n) for(j = 1 to n) // O(nlog(m)) for(i =1 to n) for(k = 1 to n) if(dot is nearby) adj[i][j]=min(adj[i][j], adj[i][k] + adj[k][j]); His ideas transformations of lists to tables His worst case time complexity is O(n^3), where n is number of elements in his so-called table. Exception to the last point with Finite structure: O(mlog(n)) where n is number of vertices and m is an arbitrary constants Questions about his ideas why to waste resources to transform constantly-modified lists to table? Fast? only point where I to some extent agree but cannot understand the same upper limits n for each for-loops -- perhaps he supposed it circular why does the code take O(mlog(n)) to proceed in time as finite structure? The term finite may be wrong, explicit?

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  • regexp in java problem

    - by Staszek28
    Hello! I found some problem while testing my NLP system. I have a java regex "(.\.\s)*Dendryt.*" and for string "v Table of Contents List of Tables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . " it just dont stop computing. Its clear that this regex complexity is very high, I will try to refactor it. Have you some suggestions for me for a future regex development ??? Thanks.

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  • Using group_by with fields_for and accepts_nested_attributes_for

    - by Derek
    I have a the following rails models: class Release < ActiveRecord::Base has_many :release_questionnaires, :dependent => :destroy accepts_nested_attributes_for :release_questionnaires ... end class class ReleaseQuestionnaire < ActiveRecord::Base belongs_to :release belongs_to :milestone ... end class In my view code, I have the following form. <% form_for @release, ... do |f| %> ... <table class="questionnaires"> <% f.fields_for :release_questionnaires, @release.release_questionnaires.sort_by{|ra| ra.questionnaire.name} do |builder| %> ... <% end %> </table> <% end %> This works and allows me to view and edit the questionnaires as desired. However, I have an additional requirement to break the questionnaires out into their own tables grouped by the milestone they are associated to, rather than in a single table. It appears as though the group_by method is design to accomplish this, but I cannot get it to work as desired inside the tag. It may be that I'm missing something obvious, as I am a beginner... Any help is appreciated.

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  • Migrate Data and Schema from MySQL to SQL Server

    - by colithium
    Are there any free solutions for automatically migrating a database from MySQL to SQL Server Server that "just works"? I've been attempting this simple (at least I thought so) task all day now. I've tried: SQL Server Management Studio's Import Data feature Create an empty database Tasks - Import Data... .NET Framework Data Provider for Odbc Valid DSN (verified it connects) Copy data from one or more tables or views Check 1 VERY simple table Click Preview Get Error: The preview data could not be retrieved. ADDITIONAL INFORMATION: ERROR [42000] [MySQL][ODBC 5.1 Driver][mysqld-5.1.45-community]You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '"table_name"' at line 1 (myodbc5.dll) A similar error occurs if I go through the rest of the wizard and perform the operation. The failed step is "Setting Source Connection" the error refers to retrieving column information and then lists the above error. It can retrieve column information just fine when I modify column mappings so I really don't know what the issue is. I've also tried getting various MySql tools to output ddl statements that SQL Server understand but haven't succeeded. I've tried with MySQL v5.1.11 to SQL Server 2005 and with MySQL v5.1.45 to SQL Server 2008 (with ODBC drivers 3.51.27.00 and 5.01.06.00 respectively)

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  • Ruby on Rails : How can i display data for the current view from a different table

    - by krishkule
    This might be a easy-to-answer question, but its a pain in the bum for me.... So... I have two tables - Chords - |id|chord|name|rating|artist_id| Artists - |id|artist| (the relations : chords : belongs_to :artist artists : has_many :chords ) And in the index page for "chords" i want to display chord,name,rating from Chords table AND artist from the Artists table this is the code for the chrod's index.html.erb : <table border="1"> <%@chords.each do |chord|%> <tr> <td><%=chord.artist.artist%></td> <td><%= link_to chord.name, chord %></td> <td><%=chord.rating%></td> <td><%= chord.created_at %></td> </tr> <%end%> </table> The error message is : undefined method `artist' for nil:NilClass Actually, at first it worked, but when i started to create the "new.html.erb" page and the create,new controllers, it stopped working - thats why this is so confusing for me! I will be glad to hear any critique and suggestions! Thank you

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  • NHibernate many-to-many mapping

    - by Scozzard
    Hi, I am having an issue with many-to-many mapping using NHibernate. Basically I have 2 classes in my object model (Scenario and Skill) mapping to three tables in my database (Scenario, Skill and ScenarioSkill). The ScenarioSkills table just holds the IDs of the SKill and Scenario table (SkillID, ScenarioID). In the object model a Scenario has a couple of general properties and a list of associated skills (IList) that is obtained from the ScenarioSkills table. There is no associated IList of Scenarios for the Skill object. The mapping from Scenario and Skill to ScenarioSkill is a many-to-many relationship: Scenario * --- * ScenarioSkill * --- * Skill I have mapped out the lists as bags as I believe this is the best option to use from what I have read. The mappings are as follows: Within the Scenario class <bag name="Skills" table="ScenarioSkills"> <key column="ScenarioID" foreign-key="FK_ScenarioSkill_ScenarioID"/> <many-to-many class="Domain.Skill, Domain" column="SkillID" /> </bag> And within the Skill class <bag name="Scenarios" table="ScenarioSkills" inverse="true" access="noop" cascade="all"> <key column="SkillID" foreign-key="FK_ScenarioSkill_SkillID" /> <many-to-many class="Domain.Scenario, Domain" column="ScenarioID" /> </bag> Everything works fine, except when I try to delete a skill, it cannot do so as there is a reference constraint on the SkillID column of the ScenarioSkill table. Can anyone help me? I am using NHibernate 2 on an C# asp.net 3.5 web application solution.

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  • "Too many indexes on table" error when creating relationships in Microsoft Access 2010.

    - by avianattackarmada
    I have tblUsers which has a primary key of UserID. UserID is used as a foreign key in many tables. Within a table, it is used as a foreign key for multiple fields (e.g. ObserverID, RecorderID, CheckerID). I have successfully added relationships (with in the the MS Access 'Relationship' view), where I have table aliases to do the multiple relationships per table: *tblUser.UserID - 1 to many - tblResight.ObserverID *tblUser_1.UserID - 1 to many - tblResight.CheckerID After creating about 25 relationships with enforcement of referential integrity, when I try to add an additional one, I get the following error: "The operation failed. There are too many indexes on table 'tblUsers.' Delete some of the indexes on the table and try the operation again." I ran the code I found here and it returned that I have 6 indexes on tblUsers. I know there is a limit of 32 indexes per table. Am I using the relationship GUI wrong? Does access create an index for the enforcement of referential integrity any time I create a relationship (especially indexes that wouldn't turn up when I ran the script)? I'm kind of baffled, any help would be appreciated.

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