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• Evaluating Django Chained QuerySets Locally

  - by jnadro52

  Hello All: I am hoping someone can help me out with a quick question I have regarding chaining Django querysets. I am noticing a slow down because I am evaluating many data points in the database to create data trends. I was wondering if there was a way to have the chained filters evaluated locally instead of hitting the database. Here is a (crude) example: pastries = Bakery.objects.filter(productType='pastry') # <--- will obviously always hit DB, when evaluated cannoli = pastries.filter(specificType='cannoli') # <--- can this be evaluated locally instead of hitting the DB when evaluated, as long as pastries was evaluated? I have checked the docs and I do not see anything specifying this, so I guess it's not possible, but I wanted to check with the 'braintrust' first ;-). BTW - I know that I can do this myself by implementing some methods to loop through these datapoints and evaluate the criteria, but there are so many datapoints that my deadline does not permit me manually implementing this. Thanks in advance.

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• How can i get notifications from server to android device?

  - by Vaibs

  I am creating a app wherein user shares some information. This data i am storing it in database through servlets i.e. i am calling my own servlets which will take data through url and store it in database. So i want other users of that same app to get notify that some information is available and in turn they will get the information that other user has updated. For this to work we can use polling or pusher. But polling will take lots of battery power. I have tried C2DM but its not working for me. So i am thinking for some other mechanism by which i can implement other than C2DM. Please suggest some way to work it. and e.g. if u have came across.

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• Does the Frontier Kernel have a future?

  - by pbreitenbach

  Whatever you think about Dave Winer, Frontier is an incredible piece of software. It includes quite a few advances that have yet to be surpassed: the object database, the database viewer, the scripting environment, the hierarchical-including website generation scheme, the elegant scripting language, the mixing of scripts and compilation, rapid prototyping, built in web server, simple debugger, cross-platform, simple UI, etc. My question: Dave turned Frontier over to open source and there is a Frontier Kernel project. However it is fairly quiet. Does Frontier have a future from here?

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• Creating a triple store query using SQL - how to find all triples that have a common predicate and o

  - by Ankur

  I have a database that acts like a triple store, except that it is just a simple MySQL database. I want to select all triples that have a common predicate and object. Info about RDF and triples I can't seem to work out the SQL. If I had just a single predicate and object to match I would do: select TRIPLE from TRIPLES where PREDICATE="predicateName" and OBJECT="objectName" But if I have a list (HashMap) of many pairs of (predicateName,objectName) I am not sure what I need to do. Please let me know if I need to provide more info, I am not sure that I have made this quite clear, but I am wary of providing too much info and confusing the issue.

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• Prevent sqlite INJECTION ATTACKS on your own iPhone?

  - by Bonnie

  I always take precautions regarding SQL INJECTION ATTACKS when data is saved between someone's iPhone and a remote database on the cloud. But is it also necessary to do the same... when just saving data (using sqlite) from someone's cell phone, to a database that's just on their own phone? What's the worse they can do? Delete their own data (or tables) on their own phone? (If they really try hard enough.) Thanks.

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• Calculated property with JPA / Hibernate

  - by Francois

  My Java bean has a childCount property. This property is not mapped to a database column. Instead, it should be calculated by the database with a COUNT() function operating on the join of my Java bean and its children. It would be even better if this property could be calculated on demand / "lazily", but this is not mandatory. In the worst case scenario, I can set this bean's property with HQL or the Criteria API, but I would prefer not to. The Hibernate @Formula annotation may help, but I could barely find any documentation. Any help greatly appreciated. Thanks.

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• Is there a more expressive way of executing SQL query using Qt?

  - by ShaChris23

  I currently have this code: // Construct query QString const statement = QString("drop database if exists %1") .arg(databaseName_); QSqlQuery query(db); query.exec(statement); Is there a better way to code than the above? Specifically, I dont like how I use QString for SQL statement. It'd be nice if Qt has some class so that I could do something like: // Construct query QSomeClass statement = "drop database if exists %1"; statement.setArg(1, databaseName_); // Replace all %1 in the original string. QSqlQuery query(db); query.exec(statement);

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• Using a ICollection Value in sqlite SELECT parameterized statment

  - by case23

  Im trying to get all the entrys from a sqlite Database which have the same name as the keys in a Hashtable. My Statement looks like this. // the keys from the hashtable are names equivalent // to name entrys in the SomeTable Names Collumn Hashtable names; String query = "SELECT Id, Name FROM SomeTable WHERE Name LIKE (@Names)"; SQLiteCommand command = new SQLiteCommand(query, _databaseConnection); command.Parameters.AddWithValue("@Names", names.Keys); SQLiteDataReader reader = reader.ExecuteReader(); while(reader.Read()) { Console.WriteLine("Name: {0}, ID: {1}", reader[1].ToString(), reader[0].ToString()); } Im totally sure there are similar values in the Database, but i get nothing back and the reader does not execute. Is it impossible to add a ICollection as a Parameter Value so i need to start the reader only one time?

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• MVC Entity Model not showing my table

  - by Jessica

  I have a database with multiple tables, and some basic relationships. Here is an example of the problem I am having: My Database: **Org** ID Name etc **Detail1** ID D1name **Org_Detail1** Org_ID Detail1_ID **Detail2** ID D2Name **Org_Detail2** Org_ID Detial1_ID BooleanField My problem is, the Org_detail1 table is not showing up in the entity model, but the Org_Details2 table does. I thought it may have been because the Org_Detail1 table only contains two ID fields that are both primary keys, while the Org_Details2 table contains 2 primary key ID fields as well as a boolean field. If I add a dummy field to Org_detail1 and update it, it still won't show up and wont allow me to add a new entity relating to the Org_Detail1 table. The table won't even show up in the list, but it is listed under the tables. Is there any solution to get this table to appear in my model?

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• XSS as attack vector even if XSS data not stored?

  - by Klaas van Schelven

  I have a question about XSS Can forms be used as a vector for XSS even if the data is not stored in the database and used at a later point? i.e. in php the code would be this: <form input="text" value="<?= @$_POST['my_field'] ?>" name='my_field'> Showing an alert box (demonstrate that JS can be run) on your own browser is trivial with the code above. But is this exploitable across browsers as well? The only scenario I see is where you trick someone into visiting a certain page, i.e. a combination of CSRF and XSS. "Stored in a database and used at a later point": the scenario I understand about CSS is where you're able to post data to a site that runs JavaScript and is shown on a page in a browser that has greater/different privileges than your own. But, to be clear, this is not wat I'm talking about above.

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• Finding Cities within 'X' Kilometers (or Miles)

  - by Mike Curry

  This may or may not be clear, leave me a comment if I am off base, or you need more information. Perhaps there is a solution out there already for what I want in PHP. I am looking for a function that will add or subtract a distance from a longitude OR latitude value. Reason: I have a database with all Latitudes and Longitudes in it and want to form a query to extract all cities within X kilometers (or miles). My query would look something like this... Select * From Cities Where (Longitude > X1 and Longitude < X2) And (Latitude > Y1 and Latitude < Y2) Where X1 = Longitude - (distance) Where X2 = Longitude + (distance) Where Y1 = Latitude - (distance) Where Y2 = Latitude + (distance) I am working in PHP, with a MySql Database. Open to any suggestions also! :)

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• Concatenating databases with Squeryl

  - by Pengin

  I'm trying to use Squeryl to take the contents of a table from one database, and append it to the equivalent table in another database. The primary key will have to be reassigned in the process, but I'm getting the error NULL not allowed for column "SIMID". Why is this? object Concatenator { def main(args: Array[String]) { Class.forName("org.h2.Driver"); val seshA = Session.create( java.sql.DriverManager.getConnection("jdbc:h2:file:data/resultsA", "sa", "password"), new H2Adapter ) val seshB = Session.create( java.sql.DriverManager.getConnection("jdbc:h2:file:data/resultsB", "sa", "password"), new H2Adapter ) using(seshA){ import Library._ from(sims){s => select(s)}.foreach{item => using(seshB){ sims.insert(item); } } } } case class Simulation( @Column("SIMID") var id: Long, val date: Date ) extends KeyedEntity[Long] object Library extends Schema { val sims = table[Simulation] on(sims)(s => declare( s.id is(unique, indexed, autoIncremented) )) } }

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• Classes to Entities; Like-class inheritence problems

  - by Stacey

  Beyond work, some friends and I are trying to build a game of sorts; The way we structure some of it works pretty well for a normal object oriented approach, but as most developers will attest this does not always translate itself well into a database persistent approach. This is not the absolute layout of what we have, it is just a sample model given for sake of representation. The whole project is being done in C# 4.0, and we have every intention of using Entity Framework 4.0 (unless Fluent nHibernate can really offer us something we outright cannot do in EF). One of the problems we keep running across is inheriting things in database models. Using the Entity Framework designer, I can draw the same code I have below; but I'm sure it is pretty obvious that it doesn't work like it is expected to. To clarify a little bit; 'Items' have bonuses, which can be of anything. Therefore, every part of the game must derive from something similar so that no matter what is 'changed' it is all at a basic enough level to be hooked into. Sounds fairly simple and straightforward, right? So then, we inherit everything that pertains to the game from 'Unit'. Weights, Measures, Random (think like dice, maybe?), and there will be other such entities. Some of them are similar, but in code they will each react differently. We're having a really big problem with abstracting this kind of thing into a database model. Without 'Enum' support, it is proving difficult to translate into multiple tables that still share a common listing. One solution we've depicted is to use a 'key ring' type approach, where everything that attaches to a character is stored on a 'Ring' with a 'Key', where each Key has a Value that represents a type. This works functionally but we've discovered it becomes very sluggish and performs poorly. We also dislike this approach because it begins to feel as if everything is 'dumped' into one class; which makes management and logical structure difficult to adhere to. I was hoping someone else might have some ideas on what I could do with this problem. It's really driving me up the wall; To summarize; the goal is to build a type (Unit) that can be used as a base type (Table per Type) for generic reference across a relatively global scope, without having to dump everything into a single collection. I can use an Interface to determine actual behavior so that isn't too big of an issue. This is 'roughly' the same idea expressed in the Entity Framework.

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• How to perform COUNT() or COUNT(*)

  - by ninumedia

  I have a list of tags in a database. Ex: villan hero spiderman superman superman I wanted to obtain a sorted list of the tag names in ascending order and the number of times the unique tag appeared in the database. I wrote this code: Ex: SELECT hashtag.tag_name, COUNT( * ) AS number FROM hashtag GROUP BY hashtag.tag_name ORDER BY hashtag.tag_name ASC This yields the correct result: hero - 1 spiderman - 1 superman - 2 villan - 1 How can I obtain the full COUNT of this entire list. The answer should be 4 in this case because there are naturally 4 rows. I can't seem to get a correct COUNT() without the statement failing. Thanks so much for the help! :)

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• How to create temporary files on the client machine, from Web Application?

  - by Gaurav Srivastava

  I am creating a Web Application using JSP, Struts, EJB and Servlets. The Application is a combined CRM and Accounting Package so the Database size is very huge. So, in order to make Execution faster, I want prevent round trips to the Database. For that purpose, what I want to do is create some temporary XML files on the client Machine and use them whenever required. How can I do this, as Javascript do not permits me to do so. Is there any way of doing this? Or, is there any other solution which I can adopt in order to make my application Faster?

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• At what level should security be implemented in a social network web application ?

  - by Rajkumar Gupta

  I am developing a social web application in php/mysql, I would like to hear your advice about what would be a better way to implement security. I am planning something like this:- At the presentation level, I restricting the user to see only those items/content he is eligible to see with the rights he is eligible & at the database level, whenever my data is read/ written or updated I verify that the person has rights to such interactions with that part of data. So for each action there is 2 layers of security one at the view level & another at the database level. Would double checking be much overhead ? ofcourse this handles only with the internal security issues ..

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• Losing DateTimeOffset precision when using C#

  - by Darvis Lombardo

  I have a SQL Server table with a CreatedDate field of type DateTimeOffset(2). A sample value which is in the table is 2010-03-01 15:18:58.57 -05:00 As an example, from within C# I retrieve this value like so: var cmd = new SqlCommand("SELECT CreatedDate FROM Entities WHERE EntityID = 2", cn); var da = new SqlDataAdapter(cmd); DataTable dt =new DataTable(); da.Fill(dt); And I look at the value: MessageBox.Show(dt.Rows[0][0].ToString()); The result is 2010-03-01 15:18:58 -05:00, which is missing the .57 that is stored in the database. If I look at dt.Rows[0][0] in the Watch window, I also do not see the .57, so it appears it has been truncated. Can someone shed some light on this? I need to use the date to match up with other records in the database and the .57 is needed. Thanks! Darvis

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• Auto Generated - CREATE Table Script in SQL 2008 throws error

  - by jack

  I scripted the tables in my dev database using SQL 2008 - generate scripts option (Datbase-right click-Tasks-Generate Scripts) and ran it on the staging database, but the script throws the below error for each table Msg 102, Level 15, State 1, Line 1 Incorrect syntax near '('. Msg 319, Level 15, State 1, Line 15 Incorrect syntax near the keyword 'with'. If this statement is a common table expression, an xmlnamespaces clause or a change tracking context clause, the previous statement must be terminated with a semicolon. Below is the script for one of my table ALTER TABLE [dbo].[Customer]( [CustomerID] [int] IDENTITY(1,1) NOT NULL, [FirstName] [nvarchar](500) NULL, [LastName] [nvarchar](500) NULL, [DateOfBirth] [datetime] NULL, [EmailID] [nvarchar](200) NULL, [ContactForOffers] [bit] NULL, CONSTRAINT [PK_Customer] PRIMARY KEY CLUSTERED ( [CustomerID] ASC )WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY] ) ON [PRIMARY] GO Any help will be much appreciated.

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• DbMetal chokes on repeated foreign key references in SQLite - any ideas?

  - by DanM

  I've been struggling to get DbMetal to process my SQLite database. I finally isolated the problem. It won't allow a table to have two foreign key references to the same column. For example, a SQLite database with these two tables will fail: CREATE TABLE Person ( Id INTEGER PRIMARY KEY, Name TEXT NOT NULL ); CREATE TABLE Match ( Id INTEGER PRIMARY KEY, WinnerPersonId INTEGER NOT NULL REFERENCES Person(Id), LoserPersonId INTEGER NOT NULL REFERENCES Person(Id) ); I get this error: DbMetal: Sequence contains more than one matching element If I get rid of the second foreign key reference, no error occurs. So, this works: CREATE TABLE Match ( Id INTEGER PRIMARY KEY, WinnerPersonId INTEGER NOT NULL REFERENCES Person(Id), LoserPersonId INTEGER NOT NULL ); But I really need both "person" columns to reference the person table. I submitted a bug report for this, but I could use a workaround in the meantime. Any ideas?

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• Display using QtWebKit, whilst parsing xml

  - by Beren Scott

  I wish to use QtWebKit to load a url for display, but, that's the easy part, I can do that. What I wish to do is record / log xml as I go. My attention here is to record and database certain details on the fly, by recording those details. My problem is, how to do this all on the fly, without requesting the same url from the server twice, once for the xml, and the second time to view the url. My hope here, is to implement a very fast way of recording set data as the user passes over it. Take for example, rather then have to type out details displayed by a website, I wish to have those details chucked into a database as I the user views the website. Now, I am using QtWebKit, and I have everything pretty much solved viewing wise. I have a loadUrl() routine which calls load(url) inside the qwebview.h The problem is, how do I piggyback xml parsing on top of this?

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• How to use a variable to specify filegroup in MSSQL

  - by gt

  I want to alter a table to add a constraint during upgrade on a MSSQL database. This table is normally indexed on a filegroup called 'MY_INDEX' - but may also be on a database without this filegroup. In this case I want the indexing to be done on the 'PRIMARY' filegroup. I tried the following code to achieve this: DECLARE @fgName AS VARCHAR(10) SET @fgName = CASE WHEN EXISTS(SELECT groupname FROM sysfilegroups WHERE groupname = 'MY_INDEX') THEN QUOTENAME('MY_INDEX') ELSE QUOTENAME('PRIMARY') END ALTER TABLE [dbo].[mytable] ADD CONSTRAINT [PK_mytable] PRIMARY KEY ( [myGuid] ASC ) ON @fgName -- fails: 'incorrect syntax' However, the last line fails as it appears a filegroup cannot be specified by variable. Is this possible?

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• Howt o get the t-sql statements being used to Update a DataSet

  - by Dennis

  I've a c# DataSet object with one table in it, and put some data in it and i've made some changes to that dataset (by code). Is there a way to get the actual t-sql queries this dataset will perform on the sql server when I update the dataset to the database with code that looks something like this: var dataAdapter = new SqlDataAdapter(cmdText, connection); var affected = dataAdapter.Update(updatedDataSet); I want to know what queries this dataset will fire to the database so I can log these changes to a logfile in my c# program.

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• How to order the items in a nested LINQ-provided collection

  - by Carson McComas

  I've got a (SQL Server) database table called Category. And another database table called SubCategory. SubCategory has a foreign key relationship to Category. Because of this, thanks to LINQ, each Cateogory has a property called SubCategories and LINQ is nice enough to return all the SubCategories associated with my Category when I grab it. If I want to sort the Categories alphabetically, I can just do: return db.Categories.OrderBy(c => c.Name); However, I have no idea how to order the SubCategories collection inside each Category. My goal is to return a collection of Categories, where all of the SubCategory collections inside of them are ordered alphabetically by Name.

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• Possible Performance Considerations using Linq to SQL Repositories

  - by Robert Harvey

  I have an ASP.NET MVC application that uses Linq to SQL repositories for all interactions with the database. To deal with data security, I do trimming to filter data to only those items to which the user has access. This occurs in several places: Data in list views Links in a menu bar A treeview on the left hand side containing links to content Role-based security A special security attribute, inheriting from AuthorizeAttribute, that implements content-based authorization on every controller method. Each of these places instantiates a repository, which opens a Linq to Sql DataContext and accesses the database. So, by my count, each request for a page access opens at least six separate Linq to SQL DataContexts. Should I be concerned about this from a performance perspective, and if so, what can be done to mitigate it?

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• How can you configure or extend BITS (Background Intelligent Transfer Service) to read files from a

  - by Mark

  I have a ASP .NET load balanced application (webservice and website). It runs on SQL server. I need to be able to provide large files for download. However, because of the load balancing situation, the files are stored in the SQL database as opposed to the file system. BITS seems to be the best approach. I have full control of the client. However, i don't know how to configure BITS to read the file from the database. I know how to write the C# code for that, but i don't know how to get BITS to hook into it as opposed to reading the file from the file system. Any ideas?

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