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• How to properly reserve identity values for usage in a database?

  - by esac

  We have some code in which we need to maintain our own identity (PK) column in SQL. We have a table in which we bulk insert data, but we add data to related tables before the bulk insert is done, thus we can not use an IDENTITY column and find out the value up front. The current code is selecting the MAX value of the field and incrementing it by 1. Although there is a highly unlikely chance that two instances of our application will be running at the same time, it is still not thread-safe (not to mention that it goes to the database everytime). I am using the ADO.net entity model. How would I go about 'reserving' a range of id's to use, and when that range runs out, grab a new block to use, and guarantee that the same range will not be used.

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• ASP.NET MVC: trying out a script injection hangs Visual Studio 2010 completely?

  - by Mark Redman

  Wondering if anyone has an idea of whats going on: I am new to ASP.NET MVC and am trying out a few things with jquery/ajax. The basic scenario is a dropdownlist with an add button next to it. Clicking the add button launches a jquery ui dialog with a textbox form, entering a value saves the item to the database and refreshes the drop-downlist. The dropdownlist is re-populated using a JSON result. This all works ok. I thought I would try a script injetion attack, ie add the text: alert("oh dear") to seee what would happen and to check if I need to encode anything. When I try and save this item (similar to the same process of adding a plain text entry) Visual Studio 2010 Beta 2 hangs completely. Any ideas? UPDATE: It happens when posting: "</"

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• How to discover table properties from SQLAlchemy mapped object

  - by ssaboum

  Hi, My point is i have a class mapped with a table, in my case in a declarative way, and i want to "discover" table properties, columns, names, relations, from this class : engine = create_engine('sqlite:///' + databasePath, echo=True) # setting up root class for declarative declaration Base = declarative_base(bind=engine) class Ship(Base): __tablename__ = 'ships' id = Column(Integer, primary_key=True) name = Column(String(255)) def __init__(self, name): self.name = name def __repr__(self): return "<Ship('%s')>" % (self.name) So now my goal is from the "Ship" class to get the table columns and their properties from another piece of code. I guess i can deal with it using instrumentation but is there any way provided by the SQLAlchemy API ? Thank you.

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• SQL query - choosing 'last updated' record in a group, better db design?

  - by Jimmy

  Hi, Let's say I have a MySQL database with 3 tables: table 1: Persons, with 1 column ID (int) table 2: Newsletters, with 1 column ID (int) table 3: Subscriptions, with columns Person_ID (int), Newsletter_ID (int), Subscribed (bool), Updated (Datetime) Subscriptions.Person_ID points to a Person, and Subscription.Newsletter_ID points to a Newsletter. Thus, each person may have 0 or more subscriptions to 0 or more magazines at once. The table Subscriptions will also store the entire history of each person's subscriptions to each newsletter. If a particular Person_ID-Newsletter_ID pair doesn't have a row in the Subscriptions table, then it's equivalent to that pair having a subscription status of 'false'. Here is a sample dataset Persons ID 1 2 3 Newsletters ID 4 5 6 Subscriptions Person_ID Newsletter_ID Subscribed Updated 2 4 true 2010-05-01 3 4 true 2010-05-01 3 5 true 2010-05-10 3 4 false 2010-05-15 Thus, as of 2010-05-16, Person 1 has no subscription, Person 2 has a subscription to Newsletter 4, and Person 3 has a subscription to Newsletter 5. Person 3 had a subscription to Newsletter 4 for a while, but not anymore. I'm trying to do 2 kinds of query. A query that shows everyone's active subscriptions as of query time (we can assume that updated will never be in the future -- thus, this means returning the record with the latest 'updated' value for each Person_ID-Newsletter_ID pair, as long as Subscribed is true (if the latest record for a Person_ID-Newsletter_ID pair has a Subscribed status of false, then I don't want that record returned)). A query that returns all active subscriptions for a specific newsletter - same qualification as in 1. regarding records with 'false' in the Subscribed column. I don't use SQL/databases often enough to tell if this design is good, or if the SQL queries needed would be slow on a database with, say, 1M records in the Subscriptions table. I was using the Visual query builder tool in Visual Studio 2010 but I can't even get the query to return the latest updated record for each Person_ID-Newsletter_ID pair. Is it possible to come up with SQL queries that don't involve using subqueries (presumably because they would become too slow with a larger data set)? If not, would it be a better design to have a separate Subscriptions_History table, and every time a subscription status for a Person_ID-Newsletter-ID pair is added to Subscriptions, any existing record for that pair is moved to Subscriptions_History (that way the Subscriptions table only ever contains the latest status update for any Person_ID-Newsletter_ID pair)? I'm using .net on Windows, so would it be easier (or the same, or harder) to do this kind of queries using Linq? Entity Framework? Thanks!

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• Scala case class generated field value

  - by Petteri Hietavirta

  I have an existing Scala application and it uses case classes which are then persisted in MongoDB. I need to introduce a new field to a case class but the value of it is derived from existing field. For example, there is phone number and I want to add normalised phone number while keeping the original phone number. I'll update the existing records in MongoDB but I would need to add this normalisation feature to existing save and update code. So, is there any nice shortcut in Scala to add a "hook" to a certain field of a case class? For example, in Java one could modify setter of the phone number.

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• whats wrong with this peace of code for saving contacts

  - by Shadow

  Hi, i am using the latest Nokia Qt SDK. i have tried to add the contacts, its not getting added.. what is missing here.. // Construct contact manager for default contact backend QContactManager* cm = new QContactManager("simulator"); // QContactManager* cm = new QContactManager("memory"); // i tried this, its also not working // Create example contact QContact example; // Add contact name QContactName name; name.setFirstName("John"); name.setLastName("Doe"); example.saveDetail(&name); // Add contact email address //QContactEmailAddress email; // email.setContexts(QContactDetail::ContextHome); //email.setEmailAddress(“[email protected]”); // example.saveDetail(&email); // Finally, save the contact details cm->saveContact(&example); delete cm; Thanks

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• Where is the used memory in Task Manager & Resource Monitor coming from?

  - by Sam Adams

  On a Windows 7, the working set memory usage plus private memory does not add up to the total used memory in Task Manager and Windows 7 Resource Monitor. How do you find out where the used memory is coming from? The cached memory can't be part of it because sometimes the total cache is greater than the total in use. The commit memory plus the working set also doesn't add up to the total in use - but even that shouldn't be significant if it did, since commit is virtual.

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• rails migration. modify starting point for auto_increment

  - by railsnew

  I have a table already created. I am looking for a rails migration where I can modify the starting point of the auto_increment number for id column of my table. Let's say I want it to start from 1000. I googled a bit and came across this: it says: :options "string" pass raw options to your underlying database, e.g. auto_increment = 10000. Note that passing options will cause you to lose the default ENGINE=InnoDB statement Can this be used for something I want? and how will the migration look since i am changing the column and not creating new one...

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• Can't see any entries on "File Types" tab on Windows 7's Desktop Search

  - by Mick

  For some reason, Windows Desktop Search (included with Windows 7.0) now no longer shows any file types on the "Advanced Options" dialog box. Any ideas on how to fix this? WDS claims to be indexing...but I'm not sure what it's actually indexing right now. I should also add that when I try to add a file type, nothing shows up or is ever actually added. If I login as a different user on the same system, everything appears normally.

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• Link a sequence with to an identity in hsqldb

  - by Candy Chiu

  In PostgreSql, one can define a sequence and use it as the primary key of a table. In HsqlDB, one can still accomplish creating an auto-increment identity column which doesn't link to any user defined sequence. Is it possible to use a user defined sequence as the generator of an auto-increment identity column in HsqlDB? Sample sql in PostgreSql: CREATE SEQUENCE seq_company_id START WITH 1; CREATE TABLE company ( id bigint PRIMARY KEY DEFAULT nextval('seq_company_id'), name varchar(128) NOT NULL CHECK (name < '') ); What's the equivalent in HsqlDB? Thanks.

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• How to lowercase every element of a collection efficiently?

  - by Chris

  Whats the most efficient way to lower case every element of a list or set? My idea for a List: final List<String> strings = new ArrayList<String>(); strings.add("HELLO"); strings.add("WORLD"); for(int i=0,l=strings.size();i<l;++i) { strings.add(strings.remove(0).toLowerCase()); } is there a better, faster way? How would this exmaple look like for a set? As there is currently no method for applying an operation to each element of a set (or list) can it be done without creating an additional temporary set? Something like this would be nice: Set<String> strings = new HashSet<String>(); strings.apply( function (element) { this.replace(element, element.toLowerCase();) } ); Thanks,

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• How do I UPDATE a Linked Server table where "alias" is required, in SQL Server 2000?

  - by Mark Hurd

  In SQL Server 2005 tablename can be used to distinguish which table you're referring to: UPDATE LinkedServer.database.user.tablename SET val=u.val FROM localtable u WHERE tablename.ID=u.ID In SQL Server 2000 this results in Server: Msg 107, Level 16, State 2 The column prefix 'tablename' does not match with a table name or alias name used in the query. Trying UPDATE LinkedServer.database.user.tablename SET val=u.val FROM localtable u WHERE LinkedServer.database.user.tablename.ID=u.ID results in Server: Msg 117, Level 15, State 2 The number name 'LinkedServer.database.user.tablename' contains more than the maximum number of prefixes. The maximum is 3. And, of course, UPDATE LinkedServer.database.user.tablename SET val=u.val FROM localtable u WHERE ID=u.ID results in Server: Msg 209, Level 16, State 1 Ambiguous column name 'ID'. (In fact searching on "The number name contains more than the maximum number of prefixes. The maximum is 3." I found the answer, but I've typed up this question and I'm going to post it! :-) )

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• DDEX Firebird editing queries duplicates columns in Visual Studio 2008

  - by A Bothe

  Hello everybody! I don't know if some of you also has experienced it but when I edit a query in Visual Studio (it uses DDEX 2.0.5 for accessing the Firebird 2.5 database), it duplicates some of the columns. What's really interesting is the fact that only System.Boolean columns are duplicated: Originally, there was only ,for instance, a 'PRO_DELETED' field... Now I wanted to sort my results by this field - I had to change the select statement in the so-called QueryBuilder by adding "ORDER BY PRO_DELETED" ...After clicking OK it somehow created a new column (!?) called 'PRO_DELETED1' My question is: Why does DDEX add such a new row to the column view and why can't I access the original PRO_DELETED field anymore? Thanks in advance!

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• Get DataGridView checkbox cell value?

  - by George

  Hello guys. I'm having a strange issue here. I have a 3 column datagrid that is filled by a connection with the database. So far so good. I have an extra column, of checkbox type. I need to get it's value for perfoming a bulk operation on it. Here is the catch: When all cells are selected, it works fine. But when an user selects any cell that its not the first, software gives me a object reference exception. Here is the code public List<String> GetSelected() { List<String> selected = new List<String>(); foreach(DataGridViewRow row in datagrid.rows) { if ((Boolean)row.Cells[wantedCell].Value == true) { selected.Add(row.Cells[anotherCell]); } } } I tracked down the failure to the if-test, throwing a exception, because the value of the cell is read as null. Any thougths? Thanks

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• Should I create a unique clustered index, or non-unique clustered index on this SQL 2005 table?

  - by Bremer

  I have a table storing millions of rows. It looks something like this: Table_Docs ID, Bigint (Identity col) OutputFileID, int Sequence, int …(many other fields) We find ourselves in a situation where the developer who designed it made the OutputFileID the clustered index. It is not unique. There can be thousands of records with this ID. It has no benefit to any processes using this table, so we plan to remove it. The question, is what to change it to… I have two candidates, the ID identity column is a natural choice. However, we have a process which does a lot of update commands on this table, and it uses the Sequence to do so. The Sequence is non-unique. Most records only contain one, but about 20% can have two or more records with the same Sequence. The INSERT app is a VB6 piece of crud throwing thousands insert commands at the table. The Inserted values are never in any particular order. So the Sequence of one insert may be 12345, and the next could be 12245. I know that this could cause SQL to move a lot of data to keep the clustered index in order. However, the Sequence of the inserts are generally close to being in order. All inserts would take place at the end of the clustered table. Eg: I have 5 million records with Sequence spanning 1 to 5 million. The INSERT app will be inserting sequence’s at the end of that range at any given time. Reordering of the data should be minimal (tens of thousands of records at most). Now, the UPDATE app is our .NET star. It does all UPDATES on the Sequence column. “Update Table_Docs Set Feild1=This, Field2=That…WHERE Sequence =12345” – hundreds of thousands of these a day. The UPDATES are completely and totally, random, touching all points of the table. All other processes are simply doing SELECT’s on this (Web pages). Regular indexes cover those. So my question is, what’s better….a unique clustered index on the ID column, benefiting the INSERT app, or a non-unique clustered index on the Sequence, benefiting the UPDATE app?

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• Visual Studio: Link executable

  - by smerlin

  Lets say I have: a static library project called "LIB" a application project called "LIBAPP" a application project called "APP" a application project called "APPTEST" When i add "LIB" to LIBAPP Project Dependencies, Visual Studio automatically links "LIBAPP" against LIB. But when i add APP to APPTEST Project Dependencies, it doesnt. Since i am doing unit tests of APP's classes in APPTEST, i have to link against APP, therefore i am currently manually linking against all *.obj files of APP (hundreds...) Since i have to change the link targets of APPTEST everytime i add or remove a *.cpp file from APP, this isnt a nice solution. So is there a way to force Visual Studio to do this for me automatically, like it does when adding a static library Project Dependency ?

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• How to get min/max of two integers in Postgres/SQL?

  - by HRJ

  How do I find the maximum (or minimum) of two integers in Postgres/SQL? One of the integers is not a column value. I will give an example scenario: I would like to subtract an integer from a column (in all rows), but the result should not be less than zero. So, to begin with, I have: UPDATE my_table SET my_column = my_column - 10; But this can make some of the values negative. What I would like (in pseudo code) is: UPDATE my_table SET my_column = MAXIMUM(my_column - 10, 0);

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• How to use Datasource to fetch some value that has been filled in it.

  - by Shantanu Gupta

  I am trying to fetch a column value from a datasource when some value is selected from a dropdownlist on its change event. <asp:DropDownList ID="ddlCityName" runat="server" DataSourceID="dsCity" DataTextField="CityName" DataValueField="CityID" AutoPostBack="True" OnTextChanged="CityName_OnTextChanged"> </asp:DropDownList> <asp:SqlDataSource ID="dsCity" runat="server" ConnectionString="<%$ ConnectionStrings:GmapConnectionString %>" SelectCommand="SELECT * FROM [vcity]" ></asp:SqlDataSource> Here I want to fetch any other column's value that is not binded to a ddlCityName from sqldatasource. I have four columns in datasource i.e. name, id, address, phno. I want to fetch an address of a person who selects some value from ddl.

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• Problem with Oracle/SQL ORDER BY Statement

  - by ArneRie

  Hi, i have the following content inside an varchar2 column: 10.1.2.3 10.2.3.4 8.3.4.1 8.3.2.1 4.2.1.3 4.3.2.1 9.3.1.2 When i query the database i need an result ordered: 4.... 8.... 9.... 10... the NLS_SORT parameter is set to german, an simple "order by COLUMN DESC/ASC" is not working like excepted. It returns 10..... 8...... 9...... any suggestions?

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• Edit and create nodes in a view?

  - by tputkonen

  We are storing people's class attendance information to Drupal. We would like to show this in a grid/chart, where the first column of each row shows person's name, and rest of the columns (ca. 20) either a checkbox or "X" if the user attended a class, or otherwise an non-checked box or empty column: (dates here) Jack X XXX X X Jill XX XXX XX It should also be possible to edit the attendance information on the grid. Each attendance information is a node of its own. This functionality can probably mostly be achieved using views and editablefields, but there is one problem: if a person has not attended a specific class he/she will not have at all an attendace node for that day. What would be the easiest way to create an attendace node in those cases, so that it would be possible for the end user to edit the grid by just clicking on the checkbox or typing an 'X'?

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• MochaUI: 'A is null' when adding columns

  - by Richard John

  I've just downloaded MochaUI, and I'm playing around trying to build an interface. I've successfully created windows, but I'm having trouble when it comes to layouts with columns. I've included all of the libraries in the same order as the demo, and this is in my init code: window.addEvent('domready', function(){ new MochaUI.Column({ id: 'sideColumn1', placement: 'left', width: 200, resizeLimit: [100, 300] }); }); When run, no column is created and I get the error: A is null Does anyone have any ideas? Thanks!

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• Mercurial (hg) commit only certain files

  - by bresc

  Hi I'm trying to commit only certain files with hg. Because of of hg having auto-add whenever I try to commit a change it wants to commit all files. But I don't want that because certain files are not "ready" yet. There is hg commit -I thefile.foo, but this is only for one file. The better way for me would be if I can turn off auto-add as in git. Is this possible? thx

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• How to append to an XML response an error attribute using Ruby on Rails 3?

  - by user502052

  I am trying to implement REST APIs, so in my RoR3 application I have XML responses. Before to pass to a consumer the XML, I wuold like to check if there are errors and, if so, send back a response with error messages. I read "Active Record Validations and Callbacks" guides on the RoR website, but it seems not work in my case. I extract from the database a resource doing @response = User.find_by_id(1) and I wuold like, if possible, to add error to it. Seeing some examples I have seen how to report errors in an XML file format.xml { render :xml => @response.errors } but how I can add append new errors to the @response? Maybe something like this: errors.add(:password, "is invalid")

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• Fixing "Lock wait timeout exceeded; try restarting transaction" for a 'stuck" Mysql table?

  - by Tom

  From a script I sent a query like this thousands of times to my local database: update some_table set some_column = some_value I forgot to add the where part, so the same column was set to the same a value for all the rows in the table and this was done thousands of times and the column was indexed, so the corresponding index was probably updated too lots of times. I noticed something was wrong, because it took too long, so I killed the script. I even rebooted my computer since them, but something stuck in the table, because simple queries take a very long time to run and when I try dropping the relevant index it fails with this message: Lock wait timeout exceeded; try restarting transaction It's an innodb table, so stuck the transaction is probably implicit. How can I fix this table and remove the stuck transaction from it?

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• Constant in Hibernate Mapping Files

  - by bertolami

  I would like to add a value object to a mapped class where one column is fixed depending of the class that contains the component. How can I do something like this? <component name="aComponent"> <property name="abc" column="cde"/> <property name="xyz" value="FIXED"/> </component> Unfortunatly, the value attribute does not exist. Is there another way to apply a constant value to property? Thanks in advance.

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