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  • Building highly scalable web services

    - by christopher-mccann
    My team and I are in the middle of developing an application which needs to be able to handle pretty heavy traffic. Not facebook level but in the future I would like to be able to scale to that without massive code re-writes. My thought was to modularise out everything into seperate services with their own interfaces. So for example messaging would have a messaging interface that might have send and getMessages() as methods and then the PHP web app would simply query this interface through soap or curl or something like that. The messaging application could then be any kind of application so a Java application or Python or whatever was suitable for that particular functionality with its own seperate database shard. Is this a good approach?

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  • Find all clauses related to an atom

    - by Luc Touraille
    This is probably a very silly question (I just started learning Prolog a few hours ago), but is it possible to find all the clauses related to an atom? For example, assuming the following knowledge base: cat(tom). animal(X) :- cat(X). , is there a way to obtain every possible information about tom (or at least all the facts that are explicitly stated in the base)? I understand that a query like this is not possible: ?- Pred(tom). so I thought I could write a rule that would deduce the correct information: meta(Object, Predicate) :- Goal =.. [Predicate, Object], call(Goal). so that I could write queries such as ?- meta(tom, Predicate). but this does not work because arguments to call are not sufficiently instantiated. So basically my question is: is this at all possible, or is Prolog not design to provide this kind of information? And if it is not possible, why?

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  • Is it possible to create ICriteria/ICriterion from LINQ or HQL?

    - by adrin
    I am creating a method that can create filter understood by NHibernate (by filter i mean a set of ICriteria object for example) from my abstract filter object. public static IEnumerable<ICriterion> ToNhCriteria(this MyCriteria criteria) { // T4 generated function // lots of result.Add(Expression.Or(Expression.Eq(),Expression.Eq)) expression trees - hard to generate // Is there a way to generate HQL/Linq query here istead? } then i want to do something like session.CreateCriteria<Entity>().Add(myCriteria.ToNhCriteria()) to filter entities. The problem is that using Expression. methods (Expression.Or etc) is quite tedious (the method is generated and i have multiple or statements that have to be joined into an expression somehow). Is there a way to avoid using Expression.Or() and create ICrietrion / ICriteria using LINQ or HQL?

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  • NullReferenceException in EntityFramework, how come?

    - by Mickel
    Take a look at this query: var user = GetUser(userId); var sessionInvites = ctx.SessionInvites .Include("InvitingUser") .Include("InvitedUser") .Where(e => e.InvitedUser.UserId == user.UserId) .ToList(); var invites = sessionInvites; // Commenting out the two lines below, and it works as expected. foreach (var invite in sessionInvites) ctx.DeleteObject(invite); ctx.SaveChanges(); return invites; Now, everything here executes without any errors. The invites that exists for the user are being deleted and the invites are being returned with success. However, when I then try to navigate to either InvitingUser or InvitedUser on any of the returned invites, I get NullReferenceException. All other properties of the SessionIvites returned, works fine. How come? [EDIT] Now the weird thing is, if I comment out the lines with delete it works as expected. (Except that the entities will not get deleted :S)

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  • How to deny payment via PayPal IPN?

    - by Nick
    Hello all, I need to create dynamic 'Pay Now' buttons on my site, and PayPal says the way to do this is via an HTML FORM with preset variables for the price, currency, and item of the purchase. I use PayPal IPN to notify me when a payment has complete. However, what's to stop someone from modifying the query parameters of the Pay Now button to change the price? Some people have told me to redirect the button through a PHP file that sends you to a PayPal payment page with the parameters in place, but the price could just as easily be manipulated in the Web browser's address bar. My question is, how can I deny a payment if the information I receive from PayPal's IPN service is invalid (if the price doesn't match our records)? I'm quite confused and couldn't find any documentation on what I'm looking for. Hopefully, you guys can help. Thanks!

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  • Active Directory: User UPN or DN for NTLM name, using pure LDAP?

    - by Bernd Haug
    I have a Java app that can authenticate to LDAP by logging users into the AD LDAP server with the NTLM name (which they are used to - this is a requirement). I now also need to do authorization, and hence need to find a forest-unique identifier for the user (DN or UPN should work), from which I can further query the directory. The method needs to be absolutely portable, even if the AD is structured in an unusual fashion, otherwise I could just do a string replacement and search for a UPN of "${ntlm-user}@${ntlm-domain}.${configured-trailing-domain}" How can I do this, using pure LDAP? Currently, I'm using the java.naming.directory package, which I'd like to keep using, since it doesn't throw up problems when not binding with a DN but logging in with an NTLM name?

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  • SQL indexing on varchar

    - by alex
    I have a table whose columns are varchar(50) and a float - I need to (very quickly) look get the float associated with a given string. Even with indexing, this is rather slow. I know, however, that each string is associated with an integer, which I know at the time of lookup, so that each string maps to a unique integer, but each integer does not map to a unique string. One might think of it as a tree structure. Is there anything to be gained by adding this integer to the table, indexing on it, and using a query like SELECT floatval FROM mytable WHERE phrase=givenstring AND assoc=givenint? This is Postgres, and if you couldn't tell, I have very little experience with databases.

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  • Save in Sessions to reduce database load

    - by Kovu
    at the moment I try to reduce the load on my database extremly, so I had a look in my website and think about - what database calls can I try to avoid. So is there a rule for that? Sould I save every information in a Session that is nearly never changed? e.g.: The User-Table is a 35-coloumn-table which I need so often in so different ways, that in the moment I got this user-object at nearly every PageLoad AND in the master-site-page-load (Settings, display the username for a welcome message, colors etc etc.). So is that good to avoid the database query here, save the User-Object in a Session and call it from the session - and of course destroy the session whereever the User-Object get changed (e.g. User change his settings)?

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  • Obtain stored procedure metadata for a procedure within an Oracle package using ADO.NET

    - by alwayslearning
    Hi, I am trying to obtain the stored procedure metadata (procedure name,parameter types,parameter names etc) for a procedure declared within an Oracle package, using the standard ADO.NET API - DbConnection.GetSchema call. I am using the ODP driver. I see that the Package is listed in the 'Packages' and 'PackageBodies' metadata collections. The procedure parameter appears in the 'Arguments' and 'ProcedureParameters' collections. I do not see a way to get to the procedure information via the package metadata. Even if the procedure does not have any parameters there is a row in the 'ProcedureParameters' collection for this procedure. My question: To obtain the procedure metadata do I have to query the 'ProcedureParameters' collection and search for an entry with the required package name? I can then construct the procedure metadata based on the parameter information. Is there a shorter or quicker way to obtain the same information?

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  • getting data problem with MYSQL under linux

    - by aelshereay
    Hi all, Recently I started to use Linux (Ubuntu 9.10) instead of windows. I am working on a java web application with Spring, MYSQL with jpa. However, before to install linux I made a backup file from the database, then installed linux, installed the MYSQL Query Browser and Administrator tools, and using the Admin tool restored the backup file, then got all the tables and made a simple select statement from one of the tables and got result normally and everything seems to work just fine. There a USER table, and there's a namedQuery defined to get a user by userName, the problem is that when I pass a correct userName I still get nothing! I really don't know what is the problem! The application was working perfectly under windows! Please, can anyone help me to solve this problem? Thank you in advance.

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  • Django: ordering by backward related field property

    - by Silver Light
    Hello! I have two models related one-to-many: a Post and a Comment: class Post(models.Model): title = models.CharField(max_length=200); content = models.TextField(); class Comment(models.Model): post = models.ForeignKey('Post'); body = models.TextField(); date_added = models.DateTimeField(); I want to get a list of posts, ordered by the date of the latest comment. If I would write a custom SQL query it would look like this: SELECT `posts`.`*`, MAX(`comments`.`date_added`) AS `date_of_lat_comment` FROM `posts`, `comments` WHERE `posts`.`id` = `comments`.`post_id` GROUP BY `posts`.`id` ORDER BY `date_of_lat_comment` DESC How can I do same thing using django ORM?

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  • Easy way to parse a url in C++ cross platform?

    - by Andrew Bucknell
    I need to parse a url to get the protocol host path and query in an application I am writing in c++. The application is intended to be cross platform. Im surprised I cant find anything that does this in boost or poco libraries. Is it somewhere obvious Im not looking? Any suggestions on appropriate open source libs? Or is this something I just have to do my self? Its not super complicated but it seems such a common task I am surprised there isnt a common solution.

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  • linq merge elements with orderby

    - by Sanja Melnichuk
    Hi all. I need to select all terminals sorted by Attributes[2] // get all query IQueryable<ITerminal> itt = repository.Terminals.GetQuery(); // get all with Attributes[2] IQueryable<ITerminal> itt2 = itt .Select(item => new { attrs = item.Attributes[2], term = item }) .OrderBy(x => x.attrs) .Select(x => x.term); Now how to select from itt all terminals but ordered by itt2 results? How to order them by itt2? Example: itt = c,d,r,a,w,b itt2 = a,b,c // after select and after merge: a,b,c d,r,w Thanks all

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  • Storing year/make/model in a database?

    - by Mark
    Here's what I'm thinking (excuse the Django format): class VehicleMake(Model): name = CharField(max_length=50) class VehicleModel(Model): make = ForeignKey(VehicleMake) name = CharField(max_length=50) class VehicleYear(Model): model = ForeignKey(VehicleModel) year = PositiveIntegerField() This is going to be used in those contingent drop-down select boxes, which would visually be laid out like [- Year -][- Make -][- Model -]. So, to query the data I need I would first have to select all distinct years from the years table, sorted descending. Then I'd find all the vehicle makes that have produced a model in that year. And then all the models by that make in that year. Is this a good way to do it, or should I re-arrange the foreign keys somehow? Or use a many-to-many table for the years/models so that no year is repeated?

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  • SQL: How can i update a value on a column only if that value is null?

    - by user321185
    Hey, I have an SQL question which may be basic to some but is confusing me. Here is an example of column names for a table 'Person': PersonalID, FirstName, LastName, Car, HairColour, FavDrink, FavFood Let's say that I input the row: 121312, Rayna, Pieterson, BMW123d, Brown, NULL, NULL Now I want to update the values for this person, but only if the new value is not null, Update: 121312, Rayna, Pieterson, NULL, Blonde, Fanta, NULL The new row needs to be: 121312, Rayna, Pieterson, BMW123d, Blonde, Fanta, NULL So I was thinking something along the lines of: Update Person(PersonalID, FirstName, LastName, Car, HairColour, FavDrink, FavFood) set Car = @Car (where @Car is not null), HairColour = @HairColour (where @HairColour...)... etc. My only concern is that I can't group all the conditions at the end of the query because it will require all the values to have the same condition. Can't i do something like Update HairColour if @HairColour is not Null

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  • [Java/Android] Multidimensional array to ListView.. how?

    - by Yverman
    I have a query result set which I like to edit first and then put it to my ListView. Without editing my data first, I could use SimpleCursorAdapter like that: ListAdapter adapter = new SimpleCursorAdapter( this, R.layout.list_item, mCursor, new String[] { "address", "city" }, new int[] { R.id.address, R.id.zip_city }); this.setListAdapter(adapter); But now, I put everything in a multidimensional array like that: if(mCursor.isFirst()) { //create a new array String[][] listData = new String[mCursor.getCount()][3]; int i = 0; do { listData[i] = new String[] { mCursor.getString(mCursor.getColumnIndex("address")), mCursor.getString(mCursor.getColumnIndex("zip")) + " " + mCursor.getString(mCursor.getColumnIndex("city")), calculateDistance(Double.parseDouble(mCursor.getString(mCursor.getColumnIndex("diff")))) }; i++; } while(mCursor.moveToNext()); } So my problem is now, I have no idea how to put this to my ListView. Could someone help me here? Sorry for my bad english and Java knowledge. :)

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  • One executable with cmd-line params or just many satellite executables?

    - by Nikos Baxevanis
    I design an application back-end. For now, it is a .NET process (a Console Application) which hosts various communication frameworks such as Agatha and NServiceBus. I need to periodically update my datastore with values (coming from the application while it's running). I found three possible ways: Accept command line arguments, so I can call my console app with -update. On start up a background thread will periodically invoke the update method. Create an updater.exe app which will do the updates, but I will have code duplication since in some way it will need to query the data from the source in order to save it to the datastore. Which one is better?

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  • how to prune data set?

    - by sakura90
    The MovieLens data set provides a table with columns: userid | movieid | tag | timestamp I have trouble reproducing the way they pruned the MovieLens data set used in: http://www.cse.ust.hk/~yzhen/papers/tagicofi-recsys09-zhen.pdf In 4.1 Data Set of the above paper, it writes "For the tagging information, we only keep those tags which are added on at least 3 distinct movies. As for the users, we only keep those users who used at least 3 distinct tags in their tagging history. For movies, we only keep those movies that are annotated by at least 3 distinct tags." I tried to query the database: select TMP.userid, count(*) as tagnum from (select distinct T.userid as userid, T.tag as tag from tags T) AS TMP group by TMP.userid having tagnum = 3; I got a list of 1760 users who labeled 3 distinct tags. However, some of the tags are not added on at least 3 distinct movies. Any help is appreciated.

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  • Getting Wikipedia infoboxes in a format that Ruby can understand

    - by hadees
    I am trying to get the data from Wikipedia's infoboxes into a hash or something so that I can use it in my Ruby on Rails program. Specifically I'm interested in the Infobox company and Infobox person. The example I have been using is "Ford Motor Company". I want to get the company info for that and the person info for the people linked to in Ford's company box. I've tried figuring out how to do this from the Wikipedia API or DBPedia but I haven't had much luck. I know wikipedia can return some things as json which I could parse with ruby but I haven't been able to figure out how to get the infobox. In the case of DBPedia I am kind of lost on how to even query it to get the info for Ford Motor Company.

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  • When should I open and close a connection to SQL Server

    - by Martin
    I have a simple static class with a few methods in it. Each of those methods open a SqlConnection, query the database and close the connection. This way, I am sure that I always close the connection to the database, but on the other hand, I don't like to always open and close connection. Below is an example of what my methods look like. public static void AddSomething(string something) { using (SqlConnection connection = new SqlConnection("...")) { connection.Open(); // ... connection.Close(); } } Considering that the methods are inside a static class, should I have a static member containing a single SqlConnection? How and when should I drop it? What are the best practices?

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  • Problem with Full text Searching

    - by devendra
    I am searching in resumes weather the word is exist or not i am using the below query Case1: select top(10) c_resume_text from sntbl_candidates where contains(c_resume_text,'"a/dm"') in the above example only it is not working properly .It showing resumes even though there is no text like that. In Messages i am getting the following message. Informational: The full-text search condition contained noise word(s). if i try with Case 2: select top(10) c_resume_text from sntbl_candidates where contains(c_resume_text,'"a/d') i am getting proper results in case 2 can any one suggest me what to do. Thanks

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  • Low cost way to host a large table yet keep the performance scalable?

    - by Leo Liang
    I have a growing table storing time series data, 500M entries now, and 200K new records every day. The total size is around 15GB for now. My clients are querying the table via a PHP script mostly, and the size of the result set is around 10K records (not very large). select * from T where timestamp > X and timestamp < Y and additionFilters And I want this operation cheap. Currently my table is hosting in Postgres 7, on a single 16G memory Box, and I would love to see some good suggestion for me to host this in low cost and also allow me to scale up for performance if needed. The table serves: 1. Query: 90% 2. Insert: 9.9% 2. Update: 0.1% <-- very rare.

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  • SQLITE basic syntax

    - by Doori Bar
    I seem to misunderstand a basic syntax, why this sample works: sqlite3_prepare_v2(db, "insert into test values('boo','boo',0);", strlen(querystring)+1 , &stmt, NULL); if ((rc = sqlite3_step(stmt)) != SQLITE_DONE) fprintf(stderr, "Error: sqlite3_step() %d. Error Message %s;\n",rc,sqlite3_errmsg(db)); But when I try this query: "insert into test(strtest) values('boo');" I get an error: Error: sqlite3_step() 19. Error Message constraint failed; What am I missing? table test is: "create table test (blobtest BLOB(4) NOT NULL, strtest VARCHAR NOT NULL, inttest INTEGER NOT NULL );" Thanks, Doori Bar

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  • Lookahead regex produces unexpected group

    - by Ivan Yatskevich
    I'm trying to extract a page name and query string from a URL which should not contain .html Here is an example code in Java: public class TestRegex { public static void main(String[] args) { Pattern pattern = Pattern.compile("/test/(((?!\\.html).)+)\\?(.+)"); Matcher matcher = pattern.matcher("/test/page?param=value"); System.out.println(matcher.matches()); System.out.println(matcher.group(1)); System.out.println(matcher.group(2)); } } By running this code one can get the following output: true page e What's wrong with my regex so the second group contains the letter e instead of param=value?

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  • Alternative databases to use when putting IIS Logs into a database using LogParser

    - by Robin Day
    We have run some scripts that use LogParser to dump our IIS logs into a SQL Server database. We can then query this to get simple stats on hits, usage etc. It's also good when linking it to error log databases and performance counter database to compare usage with errors, etc. Having implemented this for just one system and for the last 2-3 weeks we already have a 5GB database with around 10 million records. This is making any queries to this database quite slow and will no doubt cause storage issues if we continue to log as we are. Can anyone suggest any alternative databases that we could use for this data that would be more efficient for such logs? I'd be particularly interested in any experience of Google's BigTable or Amazon's SimbleDB. Are either of these suitable for reporting queries? COUNTs, GROUP BYs, PIVOTs?

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