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• How to get the second sub element of every element in a list in R

  - by PaulHurleyuk

  I know I've come across this problem before, but I'm having a bit of a mental block at the moment. and as I can't find it on SO, I'll post it here so I can find it next time. I have a dataframe that contains a field representing an ID label. This label has two parts, an alpha prefix and a numeric suffix. I want to split it apart and create two new fields with these values in. structure(list(lab = c("N00", "N01", "N02", "B00", "B01", "B02", "Z21", "BA01", "NA03")), .Names = "lab", row.names = c(NA, -9L ), class = "data.frame") df$pre<-strsplit(df$lab, "[0-9]+") df$suf<-strsplit(df$lab, "[A-Z]+") Which gives lab pre suf 1 N00 N , 00 2 N01 N , 01 3 N02 N , 02 4 B00 B , 00 5 B01 B , 01 6 B02 B , 02 7 Z21 Z , 21 8 BA01 BA , 01 9 NA03 NA , 03 So, the first strsplit works fine, but the second gives a list, each having two elements, an empty string and the result I want, and stuffs them both into the dataframe column. How can I select the second sub-element from each element of the list ? (or, is there a better way to do this) Thanks Paul.

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• array of structures, or structure of arrays?

  - by Jason S

  Hmmm. I have a table which is an array of structures I need to store in Java. The naive don't-worry-about-memory approach says do this: public class Record { final private int field1; final private int field2; final private long field3; /* constructor & accessors here */ } List<Record> records = new ArrayList<Record>(); If I end up using a large number ( 106 ) of records, where individual records are accessed occasionally, one at a time, how would I figure out how the preceding approach (an ArrayList) would compare with an optimized approach for storage costs: public class OptimizedRecordStore { final private int[] field1; final private int[] field2; final private long[] field3; Record getRecord(int i) { return new Record(field1[i],field2[i],field3[i]); } /* constructor and other accessors & methods */ } edit: assume the # of records is something that is changed infrequently or never I'm probably not going to use the OptimizedRecordStore approach, but I want to understand the storage cost issue so I can make that decision with confidence. obviously if I add/change the # of records in the OptimizedRecordStore approach above, I either have to replace the whole object with a new one, or remove the "final" keyword. kd304 brings up a good point that was in the back of my mind. In other situations similar to this, I need column access on the records, e.g. if field1 and field2 are "time" and "position", and it's important for me to get those values as an array for use with MATLAB, so I can graph/analyze them efficiently.

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• Using NULLs in matchup table

  - by TomWilsonFL

  I am working on the accounting portion of a reservation system (think limo company). In the system there are multiple objects that can either be paid or submit a payment. I am tracking all of these "transactions" in three tables called: tx, tx_cc, and tx_ch. tx generates a new tx_id (for transaction ID) and keeps the information about amount, validity, etc. Tx_cc and tx_ch keep the information about the credit card or check used, respectively, which link to other tables (credit_card and bank_account among others). This seems fairly normalized to me, no? Now here is my problem: The payment transaction can take place for a myriad of reasons. Either a reservation is being paid for, a travel agent that booked a reservation is being paid, a driver is being paid, etc. This results in multiple tables, one for each of the entities: agent_tx, driver_tx, reservation_tx, etc. They look like this: CREATE TABLE IF NOT EXISTS `driver_tx` ( `tx_id` int(10) unsigned zerofill NOT NULL, `driver_id` int(11) NOT NULL, `reservation_id` int(11) default NULL, `reservation_item_id` int(11) default NULL, PRIMARY KEY (`tx_id`) ) ENGINE=InnoDB DEFAULT CHARSET=utf8; Now this transaction is for a driver, but could be applied to an individual item on the reservation or the entire reservation overall. Therefore I demand either reservation_id OR reservation_item_id to be null. In the future there may be other things which a driver is paid for, which I would also add to this table, defaulting to null. What is the rule on this? Opinion? Obviously I could break this out into MANY three column tables, but the amount of OUTER JOINing needed seems outrageous. Your input is appreciated. Peace, Tom

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• JMeter CSV Data Set is corrupting Japanese strings stored as proper UTF-8, I get Question Marks instead

  - by Mark Bennett

  I read in search terms from a simple text file to send to a search engine. It works fine in English, but gives me ???? for any Japanese text. Text with mixed English and Japanese does show the English text, so I know it's reading it. What I'm seeing: Input text: Snow Leopard ??????????????? Turns into: Snow Leopard ??????????????? This is in my POST field of an HTTP. If I set JMeter to encode the data, it just puts in the percent sequence for question marks. Interesting note: In the example above there are 15 Japanese characters, and then 15 question marks, so at some point it's being seen as full characters and not just bytes. About the Data: The CSV file is very simple in structure. There's only one field / one column, which I name TERM, and later use as ${TERM} I don't really need full CSV because it's only one string per line. There's no commas or quotes. When I run the Unix "file" command on the file, it says UTF-8 text. I've also verified it in command line and graphical mode on two machines. JMeter CSV Dataset Config: Filename: japanese-searches.csv File encoding: UTF-8 (also tried without) Variable names: TERM Delimiter: , Allow Quoted Data: False (I also tried True, different, but still wrong) Recycle at EOF: True Stop at EOF: False Staring mode: All threads A few things I've tried: Tried Allow quoted Data. It changed to other strange characters. -Dfile.encoding=UTF-8 Tried encoding the POST, but it just turned into a bunch of %nn for question marks And I'm not sure how "debug" just after the each line of the CSV is read in. I think it's corrupted right away, but I'm not sure. If it's only mangled when I reference it, then instead of ${TERM} perhaps there's some other "to bytes" function call. I'll start checking into that. I haven't done anything with the JMeter functions yet.

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• What could possibly be different between the table in a DataContext and an IQueryable<Table> when do

  - by Nate Bross

  I have a table, where I need to do a case insensitive search on a text field. If I run this query in LinqPad directly on my database, it works as expected Table.Where(tbl => tbl.Title.Contains("StringWithAnyCase") In my application, I've got a repository which exposes IQueryable objects which does some initial filtering and it looks like this var dc = new MyDataContext(); public IQueryable<Table> GetAllTables() { var ret = dc.Tables.Where(t => t.IsActive == true); return ret; } In the controller (its an MVC app) I use code like this in an attempt to mimic the LinqPad query: var rpo = new RepositoryOfTable(); var tables = rpo.GetAllTables(); // for some reason, this does a CASE SENSITIVE search which is NOT what I want. tables = tables.Where(tbl => tbl.Title.Contains("StringWithAnyCase"); return View(tables); The column is defiend as an nvarchar(50) in SQL Server 2008. Any help or guidance is greatly appreciated!

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• Improve Log Exceptions

  - by Jaider

  I am planning to use log4net in a new web project. In my experience, I see how big the log table can get, also I notice that errors or exceptions are repeated. For instance, I just query a log table that have more than 132.000 records, and I using distinct and found that only 2.500 records are unique (~2%), the others (~98%) are just duplicates. so, I came up with this idea to improve logging. Having a couple of new columns: counter and updated_dt, that are updated every time try to insert same record. If want to track the user that cause the exception, need to create a user_log or log_user table, to map N-N relationship. Create this model may made the system slow and inefficient trying to compare all these long text... Here the trick, we should also has a hash column of binary of 16 or 32, that hash the message and the exception, and configure an index on it. We can use HASHBYTES to help us. I am not an expert in DB, but I think that will made the faster way to locate a similar record. And because hashing doesn't guarantee uniqueness, will help to locale those similar record much faster and later compare by message or exception directly to make sure that are unique. This is a theoretical/practical solution, but will it work or bring more complexity? what aspects I am leaving out or what other considerations need to have? the trigger will do the job of insert or update, but is the trigger the best way to do it?

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• how do I deconstruct COUNT()?

  - by user151841

  I have a view with some joins in it. I'm doing a select from that view with COUNT(*) as one of the columns of the select. I'm surprised by the number it's returning. Note that there is no GROUP BY nor aggregate column statement in the source view that the query is drawing from. How can I take it apart to see how it arrives at this number? I have three columns in the GROUP BY clause. SELECT column1, column2, column3, COUNT(*) FROM View GROUP BY column1, column2, column3 I get a result like +---------+---------+---------+----------+ | column1 | column2 | column3 | COUNT(*) | +---------+---------+---------+----------+ | value1 | valueA | value_a | 103 | +---------+---------+---------+----------+ | value2 | valueB | value_b | 56 | +---------+---------+---------+----------+ etc. I'd like to see how it arrives at that 103, 26, etc. In other words, I want to run a query that returns 103 rows of something, so that I know that I've expressed the query properly. I'm double-checking my work. I'm not saying that I think COUNT(*) doesn't work ( I know that "SELECT is not broken" ), what I want to double-check is exactly what I'm expressing in my query, because I think I've expressed the wrong thing, which would be why I'm getting unexpected values. I need to see more what I'm actually directing MySQL to count. So should I take them one by one, and try out each value in a WHERE clause? In other words, should I do SELECT column1 FROM View WHERE column1 = 'first_grouped_value' SELECT column1 FROM View WHERE column1 = 'second_grouped_value' SELECT column2 FROM View WHERE column1 = 'first_grouped_value' SELECT column2 FROM View WHERE column1 = 'second_grouped_value' and see the row count returned matches the COUNT(*) value in the grouped results? Because of confidentiality, I won't be able to post any of the query or database structure. All I'm asking for is a general technique to see what COUNT(*) is actually counting.

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• Javascript tr click event with newly created rows

  - by yalechen

  I am very new to web development. I am currently using tablesorter jquery plugin to create a dynamic table, where the user can add and delete rows. I am having trouble with changing the background color of newly created rows upon clicking. It works fine with rows that are hard coded in html. Here is the relevant code: $(document).ready( function() { $('table.tablesorter td').click( function (event) { $(this).parent('tr').toggleClass('rowclick'); $(this).parent('tr').siblings().removeClass('rowclick'); }); } ) rowclick is a css class here: table.tablesorter tbody tr.rowclick td { background-color: #8dbdd8; } I have tried adding the following to my javascript function that adds a new row: var createClickHandler = function(newrow) { return function(event) { //alert(newrow.cells[0].childNodes[0].data); newrow.toggleClass('rowclick'); newrow.siblings().removeClass('rowclick'); }; } row.onclick = createClickHandler(row); The alert correctly displays the text in the first column of the row when I click the new row. However, my new rows do not respond to the css class. Anyone have any ideas? Thanks in advance.

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• Database design - table relationship question

  - by iama

  I am designing schema for a simple quiz application. It has 2 tables - "Question" and "Answer Choices". Question table has 'question ID', 'question text' and 'answer id' columns. "Answer Choices" table has 'question ID', 'answer ID' and 'answer text' columns. With this simple schema it is obvious that a question can have multiple answer choices & hence the need for the answer choices table. However, a question can have only one correct answer and hence the need for the 'answer ID' in the question table. However, this 'answer ID' column in the question table provides a illusion as though there can be multiple questions for a single answer which is not correct. The other alternative to eliminate this illusion is to have another table just for correct answer that will have just 2 columns namely the question ID and the answer ID with a 1-1 relationship between the two tables. However, I think this is redundant. Any recommendation on how best to design this thereby enforcing the rules that a question can have multiple answer choices but only one correct answer? Many Thanks.

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• active record relations – who needs it?

  - by M2_

  Well, I`m confused about rails queries. For example: Affiche belongs_to :place Place has_many :affiches We can do this now: @affiches = Affiche.all( :joins => :place ) or @affiches = Affiche.all( :include => :place ) and we will get a lot of extra SELECTs, if there are many affiches: Place Load (0.2ms) SELECT "places".* FROM "places" WHERE "places"."id" = 3 LIMIT 1 Place Load (0.3ms) SELECT "places".* FROM "places" WHERE "places"."id" = 3 LIMIT 1 Place Load (0.8ms) SELECT "places".* FROM "places" WHERE "places"."id" = 444 LIMIT 1 Place Load (1.0ms) SELECT "places".* FROM "places" WHERE "places"."id" = 222 LIMIT 1 ...and so on... And (sic!) with :joins used every SELECT is doubled! Technically we cloud just write like this: @affiches = Affiche.all( ) and the result is totally the same! (Because we have relations declared). The wayout of keeping all data in one query is removing the relations and writing a big string with "LEFT OUTER JOIN", but still there is a problem of grouping data in multy-dimentional array and a problem of similar column names, such as id. What is done wrong? Or what am I doing wrong? UPDATE: Well, i have that string Place Load (2.5ms) SELECT "places".* FROM "places" WHERE ("places"."id" IN (3,444,222,57,663,32,154,20)) and a list of selects one by one id. Strange, but I get these separate selects when I`m doing this in each scope: <%= link_to a.place.name, **a.place**( :id => a.place.friendly_id ) %> the marked a.place is the spot, that produces these extra queries.

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• Master Detail same View binding controls

  - by pipelinecache

  Hi everyone, say I have a List View with ItemControls. And a Details part that shows the selected Item from List View. Both are in the same xaml page. I tried everything to accomplish it, but what do I miss? <!-- // List --> <ItemsControl ItemsSource="{Binding Path=Model, ElementName=SomeListViewControl, Mode=Default}" SnapsToDevicePixels="True" Focusable="False" IsTabStop="False"> <ItemsControl.ItemTemplate> <DataTemplate> <SomeListView:SomeListItemControl x:Name=listItem/> </DataTemplate> </ItemsControl.ItemTemplate> </ItemsControl> <!-- // Details --> <Label Content="Begindatum" FontSize="16" VerticalAlignment="Center" Grid.Row="1" Margin="2,0,0,0"/> <TextBox x:Name="Begindatum" Grid.Column="1" Grid.Row="1" Text="{Binding Path=BeginDate, ElementName=listItem,Converter={StaticResource DateTimeConverter}, ConverterParameter=dd-MM-yyyy}" IsEnabled="False" Style="{DynamicResource TextBoxStyle}" MaxLength="30"/> public event EventHandler<DataEventArgs<SomeEntity>> OnOpenSomething; public ObservableCollection<SomeEntity> Model { get { return (ObservableCollection<SomeEntity>)GetValue(ModelProperty); } set { Model.CollectionChanged -= new NotifyCollectionChangedEventHandler(Model_CollectionChanged); SetValue(ModelProperty, value); Model.CollectionChanged += new NotifyCollectionChangedEventHandler(Model_CollectionChanged); UpdateVisualState(); } } public static readonly DependencyProperty ModelProperty = DependencyProperty.Register("Model", typeof(ObservableCollection<SomeEntity>), typeof(SomeListView), new UIPropertyMetadata(new ObservableCollection<SomeEntity>(), new PropertyChangedCallback(ChangedModel))); private static void ChangedModel(DependencyObject source, DependencyPropertyChangedEventArgs e) { SomeListView someListView = source as SomeListView; if (someListView.Model == null) { return; } CollectionView cv = (CollectionView)CollectionViewSource.GetDefaultView(someListView.Model); } private void Model_CollectionChanged(object sender, NotifyCollectionChangedEventArgs e) { if (Model == null) { return; } }

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• Representing element as boolean with JAXB?

  - by Marcus

  We have this XML: <Summary> <ValueA>xxx</ValueA> <ValueB/> </Summary> <ValueB/> will never have any attributes or inner elements. It's a boolean type element - it exists (true) or it doesn't (false). JAXB generated a Summary class with a String valueA member, which is good. But for ValueB, JAXB generated a ValueB inner class and a corresponding member: @XmlElement(name = "ValueB") protected Summary.ValueB valueB; But what I'd like is a boolean member and no inner class: @XmlElement(name = "ValueB") protected boolean valueB; How can you do this? I'm not looking to regenerate the classes, I'd like to just make the code change manually. Update: In line with the accepted answer, we created a new method returning the boolean value conditional on whether valueB == null. As we are using Hibernate, we annotated valueB with @Transient and annotated the boolean getter with Hibernate's @Column annotation.

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• Hibernate collection mapping challenge

  - by Geln Yang

  Hi, There is a table Item like, code,name 01,parent1 02,parent2 0101,child11 0102,child12 0201,child21 0202,child22 Create a java object and hbm xml to map the table.The Item.parent is a Item whose code is equal to the first two character of its code : class Item{ string code; string name; Item parent; List<Item> children; .... setter/getter.... } <hibernate-mapping> <class name="Item" table="Item"> <id name="code" length="4" type="string"> <generator class="assigned" /> </id> <property name="name" column="name" length="50" not-null="true" /> <!--====================================== --> <many-to-one name="parent" class="Item" not-found="ignore"></many-to-one> <bag name="children"></bag> <!--====================================== --> </class> </hibernate-mapping> How to definition the mapping relationship? Thanks!

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• WPF Usercontrol with textboxes

  - by benPearce

  I have a WPF user control with a number of textboxes, this is hosted on a WPF window. The textboxes are not currently bound but I cannot type into any of them. I have put a breakpoint in the KeyDown event of one of the textboxes and it hits it fine and I can see the key I pressed. The textboxes are declared as <TextBox Grid.Row="3" Grid.Column="4" x:Name="PostcodeSearch" Style="{StaticResource SearchTextBox}" KeyDown="PostcodeSearch_KeyDown"/> The style is implemented as <Style x:Key="SearchTextBox" TargetType="{x:Type TextBox}"> <Setter Property="Control.Margin" Value="2"/> <Setter Property="Height" Value="20"/> <Setter Property="Width" Value="140"/> <Setter Property="HorizontalAlignment" Value="Left"/> </Style> I am hoping I have overlooked something obvious. EDIT: I only added the KeyDown and KeyUp events just to prove that the keys presses were getting through. I do not have any custom functionality.

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• WPF data-bound ComboBox only shows first item of ItemsSource list

  - by Mark

  Hi all, I'm sure I'm doing something stupid but for the life of me I can't think of right now. I have a ComboBox that is data-bound to a list of Layout objects. The list is initially empty but things are added over time. When the list is updated by the model the first time, this update reflects properly in the ComboBox. However, subsequent updates never show up in the ComboBox even though I can see that the list itself contains these items. Since the first update works, I know the data-binding is OK - so what am I doing wrong here? Here's the XAML (abridged): <Grid HorizontalAlignment="Stretch"> <ComboBox ItemsSource="{Binding Path=SavedLayouts, diagnostics:PresentationTraceSources.TraceLevel=High}" DisplayMemberPath="Name" SelectedValuePath="Name" SelectedItem="{Binding LoadLayout}" Height="25" Grid.Row="1" Grid.Column="0"></ComboBox> </Grid> And the related part of the model: public IList<Layout> SavedLayouts { get { return _layouts; } } public Layout SaveLayout( String data_ ) { Layout theLayout = new Layout( SaveLayoutName ); _layouts.Add( theLayout ); try { return theLayout; } finally { PropertyChangedEventHandler handler = PropertyChanged; if( handler != null ) { handler( this, new PropertyChangedEventArgs( "SavedLayouts" ) ); } } } And finally, the layout class (abridged): public class Layout { public String Name { get; private set; } } In the output window, I can see the update occurring: System.Windows.Data Warning: 91 : BindingExpression (hash=64564967): Got PropertyChanged event from TickerzModel (hash=43624632) System.Windows.Data Warning: 97 : BindingExpression (hash=64564967): GetValue at level 0 from TickerzModel (hash=43624632) using RuntimePropertyInfo(SavedLayouts): List`1 (hash=16951421 Count=11) System.Windows.Data Warning: 76 : BindingExpression (hash=64564967): TransferValue - got raw value List`1 (hash=16951421 Count=11) System.Windows.Data Warning: 85 : BindingExpression (hash=64564967): TransferValue - using final value List`1 (hash=16951421 Count=11) But I get do not get this 11th item in the ComboBox. Any ideas?

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• NSPopupButton Bindings with Value Transformer

  - by rdelmar

  I don't know if what I see with a popup button populated by bindings with a value transformer is the way it's supposed to be or not -- the unusual thing I'm seeing (at least with respect to what I've seen with value transformers and table views) is that the "value" parameter in the transformedValue: method is the whole array bound to the array controller, not the individual strings in the array. When I've done this with table views, the transformer is called once for each displayed row in the table, and the "value" parameter is whatever object is bound to that row and column, not the whole array that serves as the content array for the array controller. I have a very simple app to test this. In the app delegate there is this: +(void)initialize { RDTransformer *transformer = [[RDTransformer alloc] init]; [NSValueTransformer setValueTransformer:transformer forName:@"testTransformer"]; } - (void)applicationDidFinishLaunching:(NSNotification *)aNotification { self.theData = @[@{@"name":@"William", @"age":@"24"},@{@"name":@"Thomas", @"age":@"23"},@{@"name":@"Alexander", @"age":@"64"},@{@"name":@"James", @"age":@"47"}]; } In the RDTransformer class is this: + (Class)transformedValueClass { return [NSString class]; } +(BOOL)allowsReverseTransformation { return NO; } -(id)transformedValue:(id)value { NSLog(@"%@",value); return value; } In IB, I added an NSPopupButton to the window and an array controller to the objects list. The content array of the controller is bound to App Delegate.theData, and the Content Values of the popup button is bound to Array Controller.arrangedObjects.name with the value transformer, testTransformer. When I run the program, the log from the transformedValue: method is this: 2012-09-19 20:31:39.975 PopupBindingWithTransformer[793:303] ( ) 2012-09-19 20:31:40.019 PopupBindingWithTransformer[793:303] ( William, Thomas, Alexander, James ) This doesn't seem to be other people's experience from what I can see on SO. Is there something I'm doing wrong with either the bindings or the value transformer?

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• Getting the first of a GROUP BY clause in SQL

  - by Michael Bleigh

  I'm trying to implement single-column regionalization for a Rails application and I'm running into some major headaches with a complex SQL need. For this system, a region can be represented by a country code (e.g. us) a continent code that is uppercase (e.g. NA) or it can be NULL indicating the "default" information. I need to group these items by some relevant information such as a foreign key (we'll call it external_id). Given a country and its continent, I need to be able to select only the most specific region available. So if records exist with the country code, I select them. If, not I want a records with the continent code. If not that, I want records with a NULL code so I can receive the default values. So far I've figured that I may be able to use a generated CASE statement to get an arbitrary sort order. Something like this: SELECT *, CASE region WHEN 'us' THEN 1 WHEN 'NA' THEN 2 ELSE 3 END AS region_sort FROM my_table WHERE region IN ('us','NA') OR region IS NULL GROUP BY external_id ORDER BY region_sort The problem is that without an aggregate function the actual data returned by the GROUP BY for a given row seems to be untameable. How can I massage this query to make it return only the first record of the region_sort ordered groups?

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• String or binary data would be truncated -- Heisenberg problem

  - by harpo

  When you get this error, the first thing you ask is, which column? Unfortunately, SQL Server is no help here. So you start doing trial and error. Well, right now I have a statement like: INSERT tbl (A, B, C, D, E, F, G) SELECT A, B * 2, C, D, E, q.F, G FROM tbl ,othertable q WHERE etc etc Note that Some values are modified or linked in from another table, but most values are coming from the original table, so they can't really cause truncation going back to the same field (that I know of). Eliminating fields one at a time eventually makes the error go away, if I do it cumulatively, but — and here's the kicker — it doesn't matter which fields I eliminate. It's as if SQL Server is objecting to the total length of the row, which I doubt, since there are only about 40 fields in all, and nothing large. Anyone ever seen this before? Thanks. UPDATE: I have also done "horizontal" testing, by filtering out the SELECT, with much the same result. In other words, if I say WHERE id BETWEEN 1 AND 100: Error WHERE id BETWEEN 1 AND 50: No error WHERE id BETWEEN 50 AND 100: No error I tried many combinations, and it cannot be limited to a single row.

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• How to implement an ID field on a POCO representing an Identity field in SQL Server?

  - by Dr. Zim

  If I have a Domain Model that has an ID that maps to a SQL Server identity column, what does the POCO look like that contains that field? Candidate 1: Allows anyone to set and get the ID. I don't think we want anyone setting the ID except the Repository, from the SQL table. public class Thing { public int ID {get;set;} } Candidate 2: Allows someone to set the ID upon creation, but we won't know the ID until after we create the object (factory creates a blank Thing object where ID = 0 until we persist it). How would we set the ID after persisting? public class Thing { public Thing () : This (ID: 0) {} public Thing (int ID) { this.ID = ID } private int _ID; public int ID { get { return this.ID;}; } Candidate 3: Methods to set ID? Somehow we would need to allow the Repository to set the ID without allowing the consumer to change it. Any ideas? Is this barking up the wrong tree? Do we send the object to the Repository, save it, throw it away, then create a new object from the loaded version and return that as a new object?

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• Hibernate collection mapping Problem

  - by Geln Yang

  Hi, There is a table Item like, code,name 01,parent1 02,parent2 0101,child11 0102,child12 0201,child21 0202,child22 Create a java object and hbm xml to map the table.The Item.parent is a Item whose code is equal to the first two characters of its code : class Item{ String code; String name; Item parent; List<Item> children; .... setter/getter.... } <hibernate-mapping> <class name="Item" table="Item"> <id name="code" length="4" type="string"> <generator class="assigned" /> </id> <property name="name" column="name" length="50" not-null="true" /> <many-to-one name="parent" class="Item" not-found="ignore"> <formula> <![CDATA[ (select i.code,r.name from Item i where (case length(code) when 4 then i.code=SUBSTRING(code,1,2) else false end)) ]]> </formula> </many-to-one> <bag name="children"></bag> </class> </hibernate-mapping> I try to use formula to define the many-to-one relationship,but it doesn't work!Is there something wrong?Or is there other method? Thanks! ps,I use mysql database.

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• NHibernate One to One Foreign Key ON DELETE CASCADE

  - by xll

  I need to implement One-to-one association between Project and ProjecSettings using fluent NHibernate: public class ProjectMap : ClassMap<Project> { public ProjectMap() { Id(x => x.Id) .UniqueKey(MapUtils.Col<Project>(x => x.Id)) .GeneratedBy.HiLo("NHHiLoIdentity", "NextHiValue", "1000", string.Format("[EntityName] = '[{0}]'", MapUtils.Table<Project>())) .Not.Nullable(); HasOne(x => x.ProjectSettings) .PropertyRef(x => x.Project); } } public class ProjectSettingsMap : ClassMap<ProjectSettings> { public ProjectSettingsMap() { Id(x => x.Id) .UniqueKey(MapUtils.Col<ProjectSettings>(x => x.Id)) .GeneratedBy.HiLo("NHHiLoIdentity", "NextHiValue", "1000", string.Format("[EntityName] = '[{0}]'", MapUtils.Table<ProjectSettings>())); References(x => x.Project) .Column(MapUtils.Ref<ProjectSettings, Project>(p => p.Project, p => p.Id)) .Unique() .Not.Nullable(); } } This results in the following sql for Project Settings: CREATE TABLE ProjectSettings ( Id bigint PRIMARY KEY NOT NULL, Project_Project_Id bigint NOT NULL UNIQUE, /* Foreign keys */ FOREIGN KEY (Project_Project_Id) REFERENCES Project() ON DELETE NO ACTION ON UPDATE NO ACTION ); What I am trying to achieve is to have ON DELETE CASCADE for the FOREIGN KEY (Project_Project_Id), so that when the project is deleted through sql query, it's settings are deleted too. How can I achieve this ? EDIT: I know about Cascade.Delete() option, but it's not what I need. Is there any way to intercept the FK statement generation?

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• What should i do for accomodating large scale data storage and retrieval?

  - by kailashbuki

  There's two columns in the table inside mysql database. First column contains the fingerprint while the second one contains the list of documents which have that fingerprint. It's much like an inverted index built by search engines. An instance of a record inside the table is shown below; 34 "doc1, doc2, doc45" The number of fingerprints is very large(can range up to trillions). There are basically following operations in the database: inserting/updating the record & retrieving the record accoring to the match in fingerprint. The table definition python snippet is: self.cursor.execute("CREATE TABLE IF NOT EXISTS `fingerprint` (fp BIGINT, documents TEXT)") And the snippet for insert/update operation is: if self.cursor.execute("UPDATE `fingerprint` SET documents=CONCAT(documents,%s) WHERE fp=%s",(","+newDocId, thisFP))== 0L: self.cursor.execute("INSERT INTO `fingerprint` VALUES (%s, %s)", (thisFP,newDocId)) The only bottleneck i have observed so far is the query time in mysql. My whole application is web based. So time is a critical factor. I have also thought of using cassandra but have less knowledge of it. Please suggest me a better way to tackle this problem.

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• Account activation PHP

  - by Wayne

  I created this account registration activation script of my own, I have checked it over again and again to find errors, I don't see a particular error... The domain would be like this: http://domain.com/include/register.php?key=true&p=AfRWDCOWF0BO6KSb6UmNMf7d333gaBOB Which comes from an email, when a user clicks it, they get redirected to this script: if($_GET['key'] == true) { $key = $_GET['p']; $sql = "SELECT * FROM users WHERE user_key = '" . $key . "'"; $result = mysql_query($sql) or die(mysql_error()); if(mysql_affected_rows($result) > 0) { $sql = "UPDATE users SET user_key = '', user_active = '1' WHERE user_key = '" . $key . "'"; $result = mysql_query(sql) or die(mysql_error()); if($result) { $_SESSION['PROCESS'] = $lang['Account_activated']; header("Location: ../index.php"); } else { $_SESSION['ERROR'] = $lang['Key_error']; header("Location: ../index.php"); } } else { $_SESSION['ERROR'] = $lang['Invalid_key']; header("Location: ../index.php"); } } It doesn't even work at all, I looked in the database with the user with that key, it matches but it keeps coming up as an error which is extremely annoying me. The database is right, the table and column is right, nothing wrong with the database, it's the script that isn't working. Help me out, guys. Thanks :)

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• Behavior of <- NULL on lists versus data.frames for removing data

  - by Ananda Mahto

  Many R users eventually figure out lots of ways to remove elements from their data. One way is to use NULL, particularly when you want to do something like drop a column from a data.frame or drop an element from a list. Eventually, a user comes across a situation where they want to drop several columns from a data.frame at once, and they hit upon <- list(NULL) as the solution (since using <- NULL will result in an error). A data.frame is a special type of list, so it wouldn't be too tough to imagine that the approaches for removing items from a list should be the same as removing columns from a data.frame. However, they produce different results, as can be seen in the example below. ## Make some small data--two data.frames and two lists cars1 <- cars2 <- head(mtcars)[1:4] cars3 <- cars4 <- as.list(cars2) ## Demonstration that the `list(NULL)` approach works cars1[c("mpg", "cyl")] <- list(NULL) cars1 # disp hp # Mazda RX4 160 110 # Mazda RX4 Wag 160 110 # Datsun 710 108 93 # Hornet 4 Drive 258 110 # Hornet Sportabout 360 175 # Valiant 225 105 ## Demonstration that simply using `NULL` does not work cars2[c("mpg", "cyl")] <- NULL # Error in `[<-.data.frame`(`*tmp*`, c("mpg", "cyl"), value = NULL) : # replacement has 0 items, need 12 Switch to applying the same concept to a list, and compare the difference in behavior. ## Does not fully drop the items, but sets them to `NULL` cars3[c("mpg", "cyl")] <- list(NULL) # $mpg # NULL # # $cyl # NULL # # $disp # [1] 160 160 108 258 360 225 # # $hp # [1] 110 110 93 110 175 105 ## *Does* drop the `list` items while this would ## have produced an error with a `data.frame` cars4[c("mpg", "cyl")] <- NULL # $disp # [1] 160 160 108 258 360 225 # # $hp # [1] 110 110 93 110 175 105 The main questions I have are, if a data.frame is a list, why does it behave so differently in this scenario? Is there a foolproof way of knowing when an element will be dropped, when it will produce an error, and when it will simply be given a NULL value? Or do we depend on trial-and-error for this?

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• How can my controls size be NaN when it is actually shown?

  - by Stian Karlsen

  I have a Grid which contains an Image in one of its columns. The image itself does not have any Width or Height set, but its size is correctly controlled through the ColumnDefinition set. From this I would assume that the image controller actually has a Width and Height set, but when I try to bind another element to its Width and Height it doesn't work. When debugging it turns out that the value of Image.Height and Image.Width are NaN. Why? <Grid> <Grid.ColumnDefinitions> <ColumnDefinition Width="350"></ColumnDefinition> <ColumnDefinition Width="*"></ColumnDefinition> <ColumnDefinition Width="10"></ColumnDefinition> <ColumnDefinition Width="*"></ColumnDefinition> </Grid.ColumnDefinitions> <Grid Grid.Column="0" Margin="5"> <Image x:Name="_image" Source="image.jpg"></Image> </Grid> </Grid>

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