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  • Complex derived attributes in Django models

    - by rabidpebble
    What I want to do is implement submission scoring for a site with users voting on the content, much like in e.g. reddit (see the 'hot' function in http://code.reddit.com/browser/sql/functions.sql). My submission model currently keeps track of up and down vote totals. Currently, when a user votes I create and save a related Vote object and then use F() expressions to update the Submission object's voting totals. The problem is that I want to update the score for the submission at the same time, but F() expressions are limited to only simple operations (it's missing support for log(), date_part(), sign() etc.) From my limited experience with Django I can see 4 options here: extend F() somehow (haven't looked at the code yet) to support the missing SQL functions; this is my preferred option and seems to fit within the Django framework the best define a scoring function (much like reddit's 'hot' function) in my database, and have Django use the value of that function for the value of the score field; as far as I can tell, #2 is not possible wrap my two step voting process in a suitably isolated transaction so that I can calculate the voting totals in Python and then update the Submission's voting totals without fear that another vote against the submission could be added/changed in the meantime; I'm hesitant to take this route because it seems overly complex - what is a "suitably isolated transaction" in this case anyway? use raw SQL; I would prefer to avoid this entirely -- what's the point of an ORM if I have to revert to SQL for such a common use case as this! (Note that this coming from somebody who loves sprocs, but is using Django for ease of development.) Before I embark on this mission to extend F() (which I'm not sure is even possible), am I about to reinvent the wheel? Is there a more standard way to do this? It seems like such a common use case and yet in an hour of searching I have yet to find a common solution...

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  • Error with varchar(max) column when using net.sourceforge.jtds.jdbc.Driver

    - by Rihan Meij
    Hi I have a MS SQL database running (MS SQL 2005) and am connecting to it via the net.sourceforge.jtds.jdbc.Driver. The query works fine for all the columns except one that is a varchar(max). Any ideas how to get around this issues? I am using the jdbc driver to run a data index into a SOLR implementation. (I do not control the database, so the first prize solution would be where I can tweak the SQL command to get the desired results) Thanks

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  • Do console apps run faster than GUI apps?

    - by omair iqbal
    I am relatively new to world of programming. I have a few performance questions: Do console apps run faster than apps with a graphical user interface? Are languages like C and Pascal faster than object oriented languages like C++ and Delphi? I know language speed depends more on compiler than on language itself, but do compilers for procedural languages produce faster code than OO ones (including C++ compilers that can produce C code)?

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  • What do these .NET auto-generated table adapter commands do? e.g. UPDATE/INSERT followed by a SELECT

    - by RickL
    I'm working with a legacy application which I'm trying to change so that it can work with SQL CE, whilst it was originally written against SQL Server. The problem I am getting now is that when I try to do dataAdapter.Update, SQL CE complains that it is not expecting the SELECT keyword in the command text. I believe this is because SQL CE does not support batch SELECT statements. The auto-generated table adapter command looks like this... this._adapter.InsertCommand.CommandText = @"INSERT INTO [Table] ([Field1], [Field2]) VALUES (@Value1, @Value2); SELECT Field1, Field2 FROM Table WHERE (Field1 = @Value1)"; What is it doing? It looks like it is inserting new records from the datatable into the database, and then reading that record back from the database into the datatable? What's the point of that? Can I just go through the code and remove all these SELECT statements? Or is there an easier way to solve my problem of wanting to use these data adapters with SQL CE? I cannot regenerate these table adapters, as the people who knew how to have long since left.

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  • Using Perfmon with MySQL Connector/NET

    - by Mark Richman
    I am trying to diagnose repeated lock wait timeouts from my ASP.NET app to MySQL 5.1. I'm using MySQL Connector/NET 6.2.3. I don't see anything MySQL-related in Perfmon's Performance Object dropdown list. What else can I do to try to diagnose these issues?

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  • How to get the FPS from a JavaFX scene?

    - by valmar
    I am currently writing a small graphical performance test benchmark for JavaFX. Thus, I need to get the current FPS at which the JavaFX scene is being refreshed. So far, I haven't found a solution how to accomplish this. Does anyone know if there is some kind of event that I could use in order to get the FPS?

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  • Full text searching in SQL Server 2008 Express Advanced

    - by Iain Macleod
    Hi, I have recently installed SQL Server 2008 Express Edition with Advanced Services on XP Pro but am having trouble getting full text searching to work with an restored database. The database was originally created in SQL Server 2005. When I call a stored proc that uses the full text index then I get the following error: Full-Text Search is not installed, or a full-text component cannot be loaded. This is my db version: Microsoft SQL Server 2008 (RTM) - 10.0.1600.22 (Intel X86) Jul 9 2008 14:43:34 Copyright (c) 1988-2008 Microsoft Corporation Express Edition with Advanced Services on Windows NT 5.1 (Build 2600: Service Pack 3) When I run: SELECT DATABASEPROPERTY('DBNAME','ISFULLTEXTENABLED') I get: 1 Also, when I look in the advanced properties for the db server in Management Studio I see both the "Default Full-Text Language" and "Full-Text Upgrade Option" properties. However, when I go to SQL Server Configuration Manager I don't see the "MSSQLFDLauncher" service. Does anyone know how to get this working? Cheers, Iain

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  • why cant I more than two values from 3 different tables in one query

    - by zurna
    This is strange. In the news details page, I want to take a few different values from different tables with one query. However, for some strange reason, I only get two values back. So the outcome is like: <rows> <row id="4"> <FullName>Efe Tuncel</FullName> <CategoryName/> <Title>Runway Report</Title> <ShortDesc/> <Desc></Desc> <Date/> </row> </rows> If I disable fullname, then I get shortdesc but not others. Same things happens with others. NewsID = Request.QueryString("NEWSID") SQL = "SELECT N.NewsID, N.MembersID, N.CategoriesID, N.ImagesID, N.NewsTitle, N.NewsShortDesc, N.NewsDesc, N.NewsActive, N.NewsDateEntered, C.CategoriesID, C.CategoriesName, M.MembersID, M.MembersFullName" SQL = SQL & " FROM News N, Categories C, Members M" SQL = SQL & " WHERE N.NewsID = "& NewsID &" AND N.NewsActive = 1 AND N.MembersID = M.MembersID AND N.CategoriesID = C.CategoriesID" Set objViewNews = objConn.Execute(SQL) With Response .Write "<?xml version='1.0' encoding='windows-1254' ?>" .Write "<rows>" End With With Response .Write "<row id='"& objViewNews("NewsID") &"'>" .Write "<FullName>"& objViewNews("MembersFullName") &"</FullName>" .Write "<CategoryName>"& objViewNews("CategoriesName") &"</CategoryName>" .Write "<Title>"& objViewNews("NewsTitle") &"</Title>" .Write "<ShortDesc>"& objViewNews("NewsShortDesc") &"</ShortDesc>" .Write "<Desc><![CDATA["& objViewNews("NewsDesc") &"]]></Desc>" .Write "<Date>"& objViewNews("NewsDateEntered") &"</Date>" .Write "</row>" End With With Response .Write "</rows>" End With objViewNews.Close Set objViewNews = Nothing

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  • Doing a generic <sql:query> in Grails

    - by melling
    This is a generic way to select data from a table and show the results in an HTML table using JSP taglibs. What is the generic way to do this in Grails? That is, take a few lines of SQL and generate an HTML table from scratch in Grails, including the column names as headers. <sql:query var="results" dataSource="${dsource}" select * from foo </sql:query (# of rows: ${results.rowCount}) <table border="1" <!-- column headers -- <tr bgcolor=cyan <c:forEach var="columnName" items="${results.columnNames}" <th<c:out value="${columnName}"/</th </c:forEach </tr <!-- column data -- <c:forEach var="row" items="${results.rowsByIndex}" <tr <c:forEach var="column" items="${row}" <td<c:out value="${column}"/</td </c:forEach </tr </c:forEach </table The solution to this was answered in another StackOverFlow question. http://stackoverflow.com/questions/425294/sql-database-views-in-grails IF SOMEONE WRITES A GOOD ANSWER, I'LL ACCEPT IT. I would like a 100% acceptance on all of my questions.

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  • MS Access 2003 - Save button enabling on form open on different tabs

    - by Justin
    I have a tab control on a form, and a couple different tabs have save buttons on them. Once the user saves data (via SQL statements in VBA), I set the .enabled = false so that they cannot use this button again until moving to a brand new record (which is a button click on the overall form). so when my form open i was going to reference a sub that enabled all these save buttons because the open event would mean new record. though i get an error that says it either does not exist, or is closed. any ideas? thanks EDIT: Sub Example() error handling Dim db as dao.database dim rs as dao.recordset dim sql as string SQL = "INSERT INTO tblMain (Name, Address, CITY) VALUES (" if not isnull (me.name) then sql = sql & """" & me.name & """," else sql = sql & " NULL," end if if not insull(me.adress) then sql = sql & " """ & me.address & """," else sql = sql & " NULL," end if if not isnull(me.city) then sql = sql & " """ & me.city & """," else sql = sql & " NULL," end if 'debug.print(sql) set db = currentdb db.execute (sql) MsgBox "Changes were successfully saved" me.MyTabCtl.Pages.Item("SecondPage").setfocus me.cmdSaveInfo.enabled = false and then on then the cmdSave needs to get re enabled on a new record (which by the way, this form is unbound), so it all happens when the form is re-opened. I tried this: Sub Form_Open() me.cmdSaveInfo.enabled = true End Sub and this is where I get the error stated above. So this is also not the tab that has focus when the form opens. Is that why I get this error? I cannot enable or disable a control when the tab is not showing?

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  • Is there a way to generate a short random id, avoiding collisions, without hitting persistent storag

    - by bshacklett
    If you've used GoToMeeting, that's the type of ID I want. I'd like it to be random so that it obfuscates the number of items being tracked and short, so that it's easy to reference manually; UUIDs are way too long. I'd like to avoid hitting persistent storage merely for performance reasons, but I can't think of any other way to avoid collisions. Is 9 digits enough to do something time-based?

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  • Run Sql file in MYSQL PHPMyadmin

    - by Dev
    Hi All, I have written the SQL file with on excecuting it is throwing the error as mysql @"C:\Documents and Settings\Hemant\Desktop\create_tables.sql"; ERROR 1064 (42000): 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 '@"C:\ Documents and Settings\Hemant\Desktop\create_tables.sql"' at line 1 on line 1 code is CREATE DATABASE IF NOT EXISTS test; DEFAULT CHARACTER SET latin1 COLLATE latin1_swedish_ci; USE test; please let me know is i am missing something

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  • Persistent (purely functional) Red-Black trees on disk performance

    - by Waneck
    I'm studying the best data structures to implement a simple open-source object temporal database, and currently I'm very fond of using Persistent Red-Black trees to do it. My main reasons for using persistent data structures is first of all to minimize the use of locks, so the database can be as parallel as possible. Also it will be easier to implement ACID transactions and even being able to abstract the database to work in parallel on a cluster of some kind. The great thing of this approach is that it makes possible implementing temporal databases almost for free. And this is something quite nice to have, specially for web and for data analysis (e.g. trends). All of this is very cool, but I'm a little suspicious about the overall performance of using a persistent data structure on disk. Even though there are some very fast disks available today, and all writes can be done asynchronously, so a response is always immediate, I don't want to build all application under a false premise, only to realize it isn't really a good way to do it. Here's my line of thought: - Since all writes are done asynchronously, and using a persistent data structure will enable not to invalidate the previous - and currently valid - structure, the write time isn't really a bottleneck. - There are some literature on structures like this that are exactly for disk usage. But it seems to me that these techniques will add more read overhead to achieve faster writes. But I think that exactly the opposite is preferable. Also many of these techniques really do end up with a multi-versioned trees, but they aren't strictly immutable, which is something very crucial to justify the persistent overhead. - I know there still will have to be some kind of locking when appending values to the database, and I also know there should be a good garbage collecting logic if not all versions are to be maintained (otherwise the file size will surely rise dramatically). Also a delta compression system could be thought about. - Of all search trees structures, I really think Red-Blacks are the most close to what I need, since they offer the least number of rotations. But there are some possible pitfalls along the way: - Asynchronous writes -could- affect applications that need the data in real time. But I don't think that is the case with web applications, most of the time. Also when real-time data is needed, another solutions could be devised, like a check-in/check-out system of specific data that will need to be worked on a more real-time manner. - Also they could lead to some commit conflicts, though I fail to think of a good example of when it could happen. Also commit conflicts can occur in normal RDBMS, if two threads are working with the same data, right? - The overhead of having an immutable interface like this will grow exponentially and everything is doomed to fail soon, so this all is a bad idea. Any thoughts? Thanks! edit: There seems to be a misunderstanding of what a persistent data structure is: http://en.wikipedia.org/wiki/Persistent_data_structure

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  • How to delete data in DB efficiently using LinQ to NHibernate (one-shot-delete)

    - by kastanf
    Hello, producing software for customers, mostly using MS SQL but some Oracle, a decision was made to plunge into Nhibernate (and C#). The task is to delete efficiently e.g. 10 000 rows from 100 000 and still stay sticked to ORM. I've tried named queries - link already, IQuery sql = s.GetNamedQuery("native-delete-car").SetString(0, "Kirsten"); sql.ExecuteUpdate(); but the best I have ever found seems to be: using (ITransaction tx = _session.BeginTransaction()) { try { string cmd = "delete from Customer where Id < GetSomeId()"; var count = _session.CreateSQLQuery(cmd).ExecuteUpdate(); ... Since it may not get into dB to get all complete rows before deleting them. My questions are: If there is a better way for this kind of delete. If there is a possibility to get the Where condition for Delete like this: Having a select statement (using LinQ to NHibernate) = which will generate appropriate SQL for DB = we get that Where condition and use it for Delete. Thanks :-)

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  • T-SQL - Date rounding and normalization

    - by arun prakash
    Hi: I have a stored procedure that rounds a column with dates in (yyyy:mm:dd hh:mM:ss) to the nearest 10 minute handle (yyyy:mm:dd hh:mM) 20100303 09:46:3000 ------ 20100303 09:50 but i want to chage it to round it off to the nearest 15 minute handle: 20100303 09:46:3000 ------20100303 09:45 here is my code : IF OBJECT_ID(N'[dbo].[SPNormalizeAddWhen]') IS NOT NULL DROP PROCEDURE [dbo].[SPNormalizeAddWhen] GO CREATE PROCEDURE [dbo].[SPNormalizeAddWhen] As declare @colname nvarchar(20) set @colname='Normalized Add_When' if not exists (select * from syscolumns where id=object_id('Risk') and name=@colname) exec('alter table Risk add [' + @colname + '] datetime') declare @sql nvarchar(500) set @sql='update Risk set [' + @colname + ']=cast(DATEPART(yyyy,[add when]) as nvarchar(4)) + ''-'' + cast(DATEPART(mm,[add when]) as nvarchar(2)) + ''-'' + cast(DATEPART(dd,[add when]) as nvarchar(2)) + '' '' + cast(DATEPART(Hh,[add when]) as nvarchar(2)) + '':'' + cast(round(DATEPART(Mi,[add when]),-1) as nvarchar(2)) ' print @sql exec(@sql) GO

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  • What do these C# auto-generated table adapter commands do? e.g. UPDATE/INSERT followed by a SELECT

    - by RickL
    I'm working with a legacy application which I'm trying to change so that it can work with SQL CE, whilst it was originally written against SQL Server. The problem I am getting now is that when I try to do dataAdapter.Update, SQL CE complains that it is not expecting the SELECT keyword in the command text. I believe this is because SQL CE does not support batch SELECT statements. The auto-generated table adapter command looks like this... this._adapter.InsertCommand.CommandText = @"INSERT INTO [Table] ([Field1], [Field2]) VALUES (@Value1, @Value2); SELECT Field1, Field2 FROM Table WHERE (Field1 = @Value1)"; What is it doing? It looks like it is inserting new records from the datatable into the database, and then reading that record back from the database into the datatable? What's the point of that? Can I just go through the code and remove all these SELECT statements? Or is there an easier way to solve my problem of wanting to use these data adapters with SQL CE? I cannot regenerate these table adapters, as the people who knew how to have long since left.

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  • translate stored procedure - to Linq2SQL (count, max, group, orderby)

    - by Walter
    I've two tables (1:N) CREATE TABLE master (idMaster int identity (1,1) not null, TheName varchar( 100) null, constraint pk_master primary key(idMaster) clustered) and - CREATE TABLE lnk (idSlave int not null, idMaster int not null, constraint pk_lnk_master_slave(idSlave) primary key clustered) link between Master.idMaster and lnk.idMaster I've a SQL query: select max (master.idMaster) as idMaster, master.theName, count (lnk.idSlave) as freq from lnk inner join master ON lnk.idMaster = master.idMaster Group by master.theName order by freq desc, master.theName I need to translate this T-SQL query to a Linq-to-SQL statement, preferably in C#

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  • ASP.NET Caching : Good As Well As Bad ! Page shows old content!

    - by Shyju
    I have an ASP.NET website where i have implemented page level caching using the OutPutCache directive.This boosted the page performance.My pages has few parts(Some buttons,links and labels) which are specific to the logged in user.If user is not logged in,they will see different links.Now Since i implemented the page level caching,Even after the user logged in,It's showing the old page content(Links and buttons meant for the Non logged in User). Caching is obviously good.But how to get rid of this problem ? Do i need to completely remove caching ?

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  • How can I speed up the rendering of my WPF ListBox?

    - by Justin Bozonier
    I have a WPF ListBox control (view code) and I am keeping maybe like 100-200 items in it. Every time the ObservableCollection it is bound to changes though it takes it a split second to update and it freezes the whole UI. Is there a way to add elements incrementally or something I can do to improve the performance of this control?

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  • Ruby on Rails: Accessing production database data for testing

    - by williamjones
    With Ruby on Rails, is there a way for me to dump my production database into a form that the test part of Rails can access? I'm thinking either a way to turn the production database into fixtures, or else a way to migrate data from the production database into the test database that will not get routinely cleared out by Rails. I'd like to use this data for a variety of tests, but foremost in my mind is using real data with the performance tests, so that I can get a realistic understanding of load times.

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  • Nhibernate setting query time out period for commands and pessimistic locking

    - by Nagesh
    I wish to specify a specific command timeout (or LOCK_TIMEOUT) for an SQL and once this time out is reached an exception (or alert) has to be raised in nHibernate. The following is an example pseudo-code what I have written: using (var session = sessionFactory.OpenSession()) { using (var sqlTrans = session.BeginTransaction()) { ICriteria criteria = session.CreateCriteria(typeof(Foo)); criteria.SetTimeout(5); //Here is the specified command timout, eg: property SqlCommand.CommandTimeout Foo fooObject = session.Load<Foo>(primaryKeyIntegerValue, LockMode.Force); session.SaveOrUpdate(fooObject); sqlTrans.Commit(); } } In SQL server we used to achieve this using the following SQL: BEGIN TRAN SET LOCK_TIMEOUT 500 SELECT * FROM Foo WITH (UPDLOCK, ROWLOCK) WHERE PrimaryKeyID = 1000001 If PrimaryKeyID row would have locked in other transaction the following error message is being shown by SQL Server: Msg 1222, Level 16, State 51, Line 3 Lock request time out period exceeded Similarly I wish to show a lock time out or command time out information using nHibernate. Please help me to achieve this. Thanks in advance for your help.

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