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• Advice on setting up a central db with master tables for web apps

  - by Dragn1821

  I'm starting to write more and more web applications for work. Many of these web applications need to store the same types of data, such as location. I've been thinking that it may be better to create a central db and store these "master" tables there and have each applicaiton access them. I'm not sure how to go about this. Should I create tables in my application's db to copy the data from the master table and store in the app's table (for linking with other app tables using foreign keys)? Should I use something like a web service to read the data from the master table instead of firing up a new db connection in my app? Should I forget this idea and just store the data within my app's db? I would like to have data such as the location central so I can go to one table and add a new location and the next time someone needs to select a location from one of the apps, the new one would be there. I'm using ASP.NET MVC 1.0 to build the web apps and SQL 2005 as the db. Need some advice... Thanks!

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• hibernate: com.mysql.jdbc.exceptions.jdbc4.MySQLIntegrityConstraintViolationException

  - by user121196

  when saving an object to database using hibernate, sometimes it fails because certain fields of the object exceed the maximum varchar length defined in the database. There force I am using the following approach: 1. attempt to save 2. if getting an DataException, then I truncate the fields in the object to the max length specified in the db definition, then try to save again. However, in the second save after truncation. I'm getting the following exception: hibernate: com.mysql.jdbc.exceptions.jdbc4.MySQLIntegrityConstraintViolationException: Cannot add or update a child row: a foreign key constraint fails here's the relevant code, what's wrong? public static void saveLenientObject(Object obj){ try { save2(rec); } catch (org.hibernate.exception.DataException e) { // TODO Auto-generated catch block e.printStackTrace(); saveLenientObject(rec, e); } catch (Exception e) { // TODO Auto-generated catch block e.printStackTrace(); } } private static void saveLenientObject(Object rec, DataException e) { Util.truncateObject(rec); System.out.println("after truncation "); save2(rec); } public static void save2(Object obj) throws Exception{ try{ beginTransaction(); getSession().save(obj); commitTransaction(); }catch(Exception e){ e.printStackTrace(); rollbackTransaction(); //closeSession(); throw e; }finally{ closeSession(); } }

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• Connecting a django application to a drupal database?

  - by Hans

  I have a 3 - 4000 nodes in a drupal 6 installation on mysql and want to access these data through my django application. I have used manage.py inspectdb to get a skeleton of a model structure. I guess that there are good/historical reasons for drupal's database schemes, but find that there are some hard to understand structure and that there are some challenges in applying django models on the database. Some experiences this far are: node and node revision are intertwined and I solved this by using a OneToOneField (don't need the versions). This meens that the node's body gets accessible through node.vid.body, but it works. Foreign keys need to define the proper db_column to sort out the primary keys. Terms need to use an intermediary table with ManyToManyField.through. Drupal stores both the original and the thumbnailed/resized versions of any image as files in the files table. Does anyone have experiences in accessing drupal data in django? Are there better solution to for example the node <- node revision relationship? Drupal stores time/dates as unix-style timestamps in integerfields. Any recommendations? How about time zones?

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• mailing system DB structure, need help

  - by Anna

  i have a system there user(sender) can write a note to friends(receivers), number of receivers=0. Text of the message is saved in DB and visible to sender and all receivers then they login to system. Sender can add more receivers at any time. More over any of receivers can edit the message and even remove it from DB. For this system i created 3 tables, shortly: users(userID, username, password) messages(messageID, text) list(id, senderID, receiverID, messageID) in table "list" each row corresponds to pair sender-receiver, like sender_x_ID -- receiver_1_ID -- message_1_ID sender_x_ID -- receiver_2_ID -- message_1_ID sender_x_ID -- receiver_3_ID -- message_1_ID Now the problem is: 1. if user deletes the message from table "messages" how to automatically delete all rows from table "list" which correspond to deleted message. Do i have to include some foreign keys? More important: 2. if sender has let say 3 receivers for his message1 (username1, username2 and username3) and at certain moment decides to add username4 and username5 and at the same time exclude username1 from the list of receivers. PHP code will get the new list of receivers (username2, username3, username4, username5) That means insert to table "list" sender_x_ID -- receiver_4_ID -- message_1_ID sender_x_ID -- receiver_5_ID -- message_1_ID and also delete from table "list" the row corresponding to user1 (which is not in the list or receivers any more) sender_x_ID -- receiver_1_ID -- message_1_ID which sql query to send from PHP to make it in an easy and intelligent way? Please help! Examples of sql queries would be perfect!

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• How add logic to Views? Ruby on Rails

  - by Gotjosh

  Right now I'm building a project management app in rails, here is some background info: Right now i have 2 models, one is User and the other one is Client. Clients and Users have a one-to-one relationship (client - has_one and user - belongs_to which means that the foreign key it's in the users table) So what I'm trying to do it's once you add a client you can actually add credentials (add an user) to that client, in order to do so all the clients are being displayed with a link next to that client's name meaning that you can actually create credentials for that client. What i can't figure it out how to do is, that if you actually have credentials in the database (meaning that there's a record in the users table with your client id) then don't display that link. Here's what i thought that would work <% for client in @client%> <h5> <h4><%= client.id %></h4> <a href="/clients/<%= client.id %>"><%= client.name %></a> <% for user in @user %> <% if user.client_id = client.id %> <a href="/clients/<%= client.id %>/user/new">Credentials</a> <%end%> <% end %> </h5> <% end %> And here's the controller: def index @client = Client.find_all_by_admin(0) @user = User.find(:all) end but instead it just puts the link the amount of times per records in the user table. Any help?

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• How to translate the fields of a database model?

  - by Tõnis M

  I have some tables/models in a web app that will have multilingual content. For example a university, with it's description in a default language(english) and the user wants he can see the same information in another language( if the object has it's fields translated). If there were only a few languages then I would just add fields like name_en and name_de and so on, but the number of languages isn't fixed, so that' would create a mess. I could also just create a new object with the translated data but then foreign keys wouldn't work, and only some of the fields can be translated so that would create duplicate data. Storing the translations in a file and using gettext or something similar is also not an option since the objects fields can be translated by the website user, not only developers/admins. What would be the best way to design/architect such a database? Searching from the translated data should also be not too complex - as it should not require creating complex joins which would make the queries slower I'm using PostgreSQL and Ruby of Rails but I'm not looking for a technical solution but for a general idea how to design it.

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• Is it possible to load an entire SQL Server CE database into RAM?

  - by DanM

  I'm using LinqToSql to query a small SQL Server CE database. I've noticed that any operations involving sub-properties are disappointingly slow. For example, if I have a Customer table that is referenced by an Order table via a foreign key, LinqToSql will automatically create an EntitySet<Order> property. This is a nice convenience, allowing me to do things like Customer.Order.Where(o => o.ProductName = "Stopwatch"), but for some reason, SQL Server CE hangs up pretty bad when I try to do stuff like this. One of my queries, which isn't really that complicated takes 3-4 seconds to complete. I can get the speed up to acceptable, even fast, if I just grab the two tables individually and convert them to List<Customer> and List<Order>, then join then manually with my own query, but this is throwing out a lot of the appeal of LinqToSql. So, I'm wondering if I can somehow get the whole database into RAM and just query that way, then occasionally save it. Is this possible? How? If not, is there anything else I can do to boost the performance? Note: My database in its initial state is about 250K and I don't expect it to grow to more than 1-2Mb. So, loading the data into RAM certainly wouldn't be a problem from a memory point of view.

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• mySQL select and group by values

  - by Foo

  I'd like to count and group rows by specific values. This seems fairly simple, but I can't seem to do it. I have a table set up similar to this: Table: Ratings id pID uID rating 1 1 2 7 2 1 7 7 3 1 5 4 4 1 1 1 id is the primary key, piD and uID are foreign-keys. Rating contains values between 1 and 10, and only between 1 and 10. I want to run some statistics and count the number of ratings with a certain value. In the example above, two have left a rating of 7. So I wrote the following query: SELECT COUNT(*) AS 'count' , 'rating' FROM 'ratings' WHERE pID= '1' GROUP BY `rating` ORDER BY `rating` Which yields the nice result as: count ratings 1 1 1 4 2 7 I'd like to get the mySQL query to include values between 1 and 10 as well. For example: Desired Result count ratings 1 1 0 2 0 3 1 4 0 5 0 6 2 7 0 8 0 9 0 10 Unfortunately, I'm relatively new to SQL and I've been reading through everything I could get my hands on for the past hour, but I can't get it to work. I've been leaning along the lines of a some type of JOIN. If anyone can point me in the right direction, it'd be appreciated. Thanks.

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• Creating UTF-8 files in Java from a runnable Jar

  - by RuntimeError

  I have a little Java project where I've set the properties of the class files to UTF-8 (I use a lot of foreign characters not found on the default CP1252). The goal is to create a text file (in Windows) containing a list of items. When running the class files from Eclipse itself (hitting Ctrl+F11) it creates the file flawlessly and opening it in another editor (I'm using Notepad++) I can see the characters as I wanted. +--------------------------------------------------+ ¦ Universidade2010 (18/18)¦ ¦ hidden: 0¦ +--------------------------------------------------¦ But, when I export the project (using Eclipse) as a runnable Jar and run it using 'javaw -jar project.jar' the new file created is a mess of question marks ???????????????????????????????????????????????????? ? Universidade2010 (19/19)? ? hidden: 0? ???????????????????????????????????????????????????? I've followed some tips on how to use UTF-8 (which seems to be broken by default on Java) to try to correct this so now I'm using Writer w = new OutputStreamWriter(fos, "UTF-8"); and writing the BOM header to the file like in this question already answered but still without luck when exporting to Jar Am I missing some property or command-line command so Java knows I want to create UTF-8 files by default ?

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• Codeigniter: how should I restructure db schema?

  - by Kevin Brown

  I don't even know if that's the right term. May it be known that I'm a major novice! I have three tables: users, profiles, and survey. Each one has user_id as it's first field, (auto-increment for users), and they're all tied by a foreign key constraint, CASCADE on DELETE. Currently, for each user, let's say user_id 1, they have a corresponding db entry in the other tables. For profiles it lists all their information, and the survey table holds all their survey information. Now I must change things...darn scope creep. Users need the ability to have multiple survey results. I imagine that this would be similar to a comment table for a blog... My entire app runs around the idea that a single user is linked to a constraining profile and survey. How should I structure my db? How should I design my app's db so that a user can have multiple tests/profiles for the test? Please assist! Any advice, information and personal-knowledge is appreciated! Right now the only way I know how to accompany my client is to create a pseudo-user for each test (so unnecessary) and list them in a view table (called "your tests")-- these are obtained from the db by saying: where user_id=manager_id

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• Persist data when the table was not mapped (JPA EclipseLink)

  - by enrique

  Hi everybody I need some help in persisting data into a table that has not been mapped... The issue is that the database we have has a table which all of its columns are foreign keys so by mapping the whole database all of the tables are correctly mapped. However that table called "category" is not mapped. The way in which we can browse the data is by passing for the table I mentioned using the @jointable annotation which was set by the system in the other tables with which "category" has a relation. So we can go ahead and using the collections and perform a query. But the issue comes when I want to persist data into that table because there´s no any entity. We tried to persist through the collections but no luck. Then I have just tried by creating the entity with its PK and Facade all by hand. However when I try to persist using the Merge method the system tries to perform an Insert when it is supposed to perform an Update. So obviously it returns an error. Does anybody have an idea on this situation? Thanks.-

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• Basic user authentication with records in AngularFire

  - by ajkochanowicz

  Having spent literally days trying the different, various recommended ways to do this, I've landed on what I think is the most simple and promising. Also thanks to the kind gents from this SO question: Get the index ID of an item in Firebase AngularFire Curent setup Users can log in with email and social networks, so when they create a record, it saves the userId as a sort of foreign key. Good so far. But I want to create a rule so twitter2934392 cannot read facebook63203497's records. Off to the security panel Match the IDs on the backend Unfortunately, the docs are inconsistent with the method from is firebase user id unique per provider (facebook, twitter, password) which suggest appending the social network to the ID. The docs expect you to create a different rule for each of the login method's ids. Why anyone using 1 login method would want to do that is beyond me. (From: https://www.firebase.com/docs/security/rule-expressions/auth.html) So I'll try to match the concatenated auth.provider with auth.id to the record in userId for the respective registry item. According to the API, this should be as easy as In my case using $registry instead of $user of course. { "rules": { ".read": true, ".write": true, "registry": { "$registry": { ".read": "$registry == auth.id" } } } } But that won't work, because (see the first image above), AngularFire sets each record under an index value. In the image above, it's 0. Here's where things get complicated. Also, I can't test anything in the simulator, as I cannot edit {some: 'json'} To even authenticate. The input box rejects any input. My best guess is the following. { "rules": { ".write": true, "registry": { "$registry": { ".read": "data.child('userId').val() == (auth.provider + auth.id)" } } } } Which both throws authentication errors and simultaneously grants full read access to all users. I'm losing my mind. What am I supposed to do here?

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• Deserialization of a DataSet... deal with column name changes? how to migrate data from one column to another?

  - by Brian Kennedy

  So, we wanted to slightly generalize a couple columns in our typed dataset... basically dropped a foreign key constraint and then wanted to change a couple column names to better reflect their new state. All that is easy. The problem is that our users may have serialized out the old version of the DataSet as XML. We want to be able to read those old XML files and deserialize them into the revised DataSet. It seems that would be a fairly common desire... but I haven't yet figured out the right thing to search the internet for. One possible solution would seem to be some way to give a DataColumn an alias or alternate name such that when it reads the old column name, it knows that data can be read into the column with the new column name. I can find no support for any such thing. Another approach would seem to be an "after deserialization" method of some sort... so, I would let it read in the old column values into a normal DataColumn with that name, and then in the "after deserialization" method I would just move the data from the obsolete column into the new column, and then delete the old columns. That would seem to generalize to many other situations... and having such events or hooks is pretty common in ADO.NET. But I have looked for such a hook and haven't yet found it. If no "after deserialization" hook, it would seem I ought to be able to override ReadXml or ReadXmlSerializable methods to call the base and then do my "after" stuff to fix up old data into new. But it does not appear that is possible. Soooo, I have to think backward compatibility with old serialized DataSets and simple data migration would be a well-solved problem... so, trying to reinvent that wheel seems silly. But so far, I haven't seemed to find any documentation on doing those things. Suggestions? What is best practice for this?

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• Why trigger query fails in the sqlite with Qt?

  - by dexterous_stranger

  I am a beginner in the SQL. I am using SQLite, Qt - on embedded systems. I want to put a trigger here. The trigger is that whenever the primary key Id is greater than 32145, then channelNum=101 should be set. I want to set the attrib name - text also, but I got the compilation issue. I believe that the setting of trigger is the part of DDL - Data definition language. Please let me know that if I am wrong here. Here is my create db code. I get the sql query error. Also please do suggest how to set the text attrib = "COmedy". /** associate db with query **/ QSqlQuery query ( m_demo_db ); /** Foreign keys are disabled by default in sqlite **/ /** Here is the pragma to turn them on first **/ query.exec("PRAGMA foreign_keys = ON;"); if ( false == query.exec()) { qDebug()<<"Pragma failed"; } /** Create Table for storing user preference LCN for DTT **/ qDebug()<<"Create Table postcode.db"; query.prepare(" CREATE TABLE dttServiceList (Id INTEGER PRIMARY KEY, attrib varchar(20), channelNum integer )" ); if ( false == query.exec()) { qDebug()<<"Create dttServiceList table failed"; } /** Try placing trigger here **/ triggerQuery = "CREATE TRIGGER upd_check BEFORE INSERT ON dttServiceList \ FOR EACH ROW \ BEGIN \ IF Id > 32145 THEN SET channelNum=101; \ END IF; \ END; "; query.prepare(triggerQuery); if ( false == query.exec()) { qDebug()<<"Trigger failed !!"; qDebug() << query.lastError(); } Also, how to set the text name in the trigger - I want to SET attrib = "Comedy".

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• LINQ to SQL - database relationships won't update after submit

  - by Quantic Programming

  I have a Database with the tables Users and Uploads. The important columns are: Users -> UserID Uploads -> UploadID, UserID The primary key in the relationship is Users -> UserID and the foreign key is Uploads -> UserID. In LINQ to SQL, I do the following operations: Retrieve files var upload = new Upload(); upload.UserID = user.UserID; upload.UploadID = XXX; db.Uploads.InsertOnSubmit(upload) db.SubmitChanges(); If I do that and rerun the application (and the db object is re-built, of course) - if do something like this: foreach(var upload in user.Uploads) I get all the uploads with that user's ID. (like added in the previous example) The problem is, that my application, after adding an upload an submitting changes, doesn't update the user.Uploads collection. i.e - I don't get the newly added uploads. The user object is stored in the Session object. At first, I though that the LINQ to SQL Framework doesn't update the reference of the object, therefore I should simply "reset" the user object from a new SQL request. I mean this: Session["user"] = db.Users.Where(u => u.UserID == user.UserID).SingleOrDefault(); (Where user is the previous user) But it didn't help. Please note: After rerunning the application, user.Uploads does have the new upload! Did anyone experience this type of problem, or is it normal behavior? I am a newbie to this framework. I would gladly take any advice. Thank you!

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• Checking if user owns file before deleting it

  - by Martin Hoe

  I'm building an API for my site that allows users to delete the files they upload. Obviously, I want to check if the user owns that file before they delete it through the API. I have a files table and a users table, here's the schema: f_id, s_id, u_id, name, size, uploaded u_id, username, password, email, activated, activation_code u_id is a foreign key. The u_id field in the files table points to the u_id in the users table. Given the users username, I want to find the users u_id, and then check if they own the file through the file ID (f_id). I wrote this SQL: $sql = 'SELECT u.username FROM `users` u JOIN `files` f ON u.u_id = f.u_id WHERE f_id = ? AND u.u_id = ? LIMIT 1'; I'm assuming that'd work if I was given the users u_id in the API request, but alas I'm given only their username. How can I modify that SQL to find their user ID and use that? Thanks. Edit: Alright I've got this query but it's always returning an empty result set even though both the file ID and username exist. SELECT u.username FROM `users` u JOIN `files` f ON u.u_id = f.u_id WHERE f.f_id = ? AND u.username = ? LIMIT 1

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• Why do I get this exception? {An item with the same key has already been added."})

  - by Alan

  Aknittel NewSellerID is the result of a lookup on tblSellers. These tables (tblSellerListings and tblSellers) are not "officially" joined with a foreign key relationship, either in the model or in the database, but I want some referential integrity maintained for the future. So my issue remains. Why do I get the exception ({"An item with the same key has already been added."}) with this code, if I don't begin each iteration of the foreach loop with a new ObjectContext and end it with SaveChanges, which I think will affect performance. Also, could you tell me why ORCSolutionsDataService.tblSellerListings (An ADO.NET DataServices/WCF object is not IDisposable, like LINQ to Entities?? ============================================== // Add listings to previous seller int NewSellerID = 0; // Look up existing Seller key using SellerUniqueEBAYID var qryCurrentSeller = from s in service.tblSellers where s.SellerEBAYUserID == SellerUserID select s; foreach (var s in qryCurrentSeller) NewSellerID = s.SellerID; // Save the selected listings for this seller foreach (DataGridViewRow dgr in dgvRows) { ORCSolutionsDataService.tblSellerListings NewSellerListing = new ORCSolutionsDataService.tblSellerListings(); NewSellerListing.ItemID = dgr.Cells["txtSellerItemID"].Value.ToString(); NewSellerListing.Title = dgr.Cells["txtSellerItemTitle"].Value.ToString(); NewSellerListing.CurrentPrice = Convert.ToDecimal(dgr.Cells["txtSellerItemPrice"].Value); NewSellerListing.QuantitySold = Convert.ToInt32(dgr.Cells["txtSellerItemSold"].Value); NewSellerListing.EndTime = Convert.ToDateTime(dgr.Cells["txtSellerItemEnds"].Value); NewSellerListing.CategoryName = dgr.Cells["txtSellerItemCategory"].Value.ToString(); NewSellerListing.ExtendedPrice = Convert.ToDecimal(dgr.Cells["txtExtendedReceipts"].Value); NewSellerListing.RetrievedDtime = Convert.ToDateTime(dtSellerDataRetrieved.ToString()); NewSellerListing.SellerID = NewSellerID; service.AddTotblSellerListings(NewSellerListing); } service.SaveChanges(); } catch (Exception ex) { MessageBox.Show("Unable to add a new case. Exception: " + ex.Message); }

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• sql queries slower than expected

  - by neubert

  Before I show the query here are the relevant table definitions: CREATE TABLE phpbb_posts ( topic_id mediumint(8) UNSIGNED DEFAULT '0' NOT NULL, poster_id mediumint(8) UNSIGNED DEFAULT '0' NOT NULL, KEY topic_id (topic_id), KEY poster_id (poster_id), ); CREATE TABLE phpbb_topics ( topic_id mediumint(8) UNSIGNED NOT NULL auto_increment ); Here's the query I'm trying to do: SELECT p.topic_id, p.poster_id FROM phpbb_topics AS t LEFT JOIN phpbb_posts AS p ON p.topic_id = t.topic_id AND p.poster_id <> ... WHERE p.poster_id IS NULL; Basically, the query is an attempt to find all topics where the number of times someone other than the target user has posted in is zero. In other words, the topics where the only person who has posted is the target user. Problem is that query is taking a super long time. My general assumption when it comes to SQL is that JOINs of any are super fast and can be done in no time at all assuming all relevant columns are primary or foreign keys (which in this case they are). I tried out a few other queries: SELECT COUNT(1) FROM phpbb_topics AS t JOIN phpbb_posts AS p ON p.topic_id = t.topic_id; That returns 353340 pretty quickly. I then do these: SELECT COUNT(1) FROM phpbb_topics AS t JOIN phpbb_posts AS p ON p.topic_id = t.topic_id AND p.poster_id <> 77198; SELECT COUNT(1) FROM phpbb_topics AS t JOIN phpbb_posts AS p ON p.topic_id = t.topic_id WHERE p.poster_id <> 77198; And both of those take quite a while (between 15-30 seconds). If I change the < to a = it takes no time at all. Am I making some incorrect assumptions? Maybe my DB is just foobar'd?

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• Django Admin Running Same Query Thousands of Times for Model

  - by Tom

  Running into an odd . . . loop when trying to view a model in the Django admin. I have three related models (code trimmed for brevity, hopefully I didn't trim something I shouldn't have): class Association(models.Model): somecompany_entity_id = models.CharField(max_length=10, db_index=True) name = models.CharField(max_length=200) def __unicode__(self): return self.name class ResidentialUnit(models.Model): building = models.CharField(max_length=10) app_number = models.CharField(max_length=10) unit_number = models.CharField(max_length=10) unit_description = models.CharField(max_length=100, blank=True) association = models.ForeignKey(Association) created = models.DateTimeField(auto_now_add=True) updated = models.DateTimeField(auto_now=True) def __unicode__(self): return '%s: %s, Unit %s' % (self.association, self.building, self.unit_number) class Resident(models.Model): unit = models.ForeignKey(ResidentialUnit) type = models.CharField(max_length=20, blank=True, default='') lookup_key = models.CharField(max_length=200) jenark_id = models.CharField(max_length=20, blank=True) user = models.ForeignKey(User) is_association_admin = models.BooleanField(default=False, db_index=True) show_in_contact_list = models.BooleanField(default=False, db_index=True) created = models.DateTimeField(auto_now_add=True) updated = models.DateTimeField(auto_now=True) _phones = {} home_phone = None work_phone = None cell_phone = None app_number = None account_cache_key = None def __unicode__(self): return '%s' % self.user.get_full_name() It's the last model that's causing the problem. Trying to look at a Resident in the admin takes 10-20 seconds. If I take 'self.association' out of the __unicode__ method for ResidentialUnit, a resident page renders pretty quickly. Looking at it in the debug toolbar, without the association name in ResidentialUnit (which is a foreign key on Resident), the page runs 14 queries. With the association name put back in, it runs a far more impressive 4,872 queries. The strangest part is the extra queries all seem to be looking up the association name. They all come from the same line, the __unicode__ method for ResidentialUnit. Each one is the exact same thing, e.g., SELECT `residents_association`.`id`, `residents_association`.`jenark_entity_id`, `residents_association`.`name` FROM `residents_association` WHERE `residents_association`.`id` = 1096 ORDER BY `residents_association`.`name` ASC I assume I've managed to create a circular reference, but if it were truly circular, it would just die, not run 4000x and then return. Having trouble finding a good Google or StackOverflow result for this.

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• Is it possible to modify the value of a record's primary key in Oracle when child records exist?

  - by Chris Farmer

  I have some Oracle tables that represent a parent-child relationship. They look something like this: create table Parent ( parent_id varchar2(20) not null primary key ); create table Child ( child_id number not null primary key, parent_id varchar2(20) not null, constraint fk_parent_id foreign key (parent_id) references Parent (parent_id) ); This is a live database and its schema was designed long ago under the assumption that the parent_id field would be static and unchanging for a given record. Now the rules have changed and we really would like to change the value of parent_id for some records. For example, I have these records: Parent: parent_id --------- ABC123 Child: child_id parent_id -------- --------- 1 ABC123 2 ABC123 And I want to modify ABC123 in these records in both tables to something else. It's my understanding that one cannot write an Oracle update statement that will update both parent and child tables simultaneously, and given the FK constraint, I'm not sure how best to update my database. I am currently disabling the fk_parent_id constraint, updating each table independently, and then enabling the constraint. Is there a better, single-step way to update this content?

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• when to use Hibernate vs. Simple ResultSets for small application

  - by luke

  I just started working on upgrading a small component in a distributed java application. The main application is a rather complicated applet/servlet combo running on JBoss and it extensively uses Hibernate for its DataAccess. The component i am working on however is very a very straightforward data importing service. Basically the workflow is Listen for a network event Parse the data packet, extract a set of identifiers Map the identifier set to a primary key in our database Parse the rest of the packet and insert items in a related table using the foreign key found in step 3 Repeat in the previous version of this component it used a hibernate based DAL, that is no longer usable for a variety of reasons (in particular it is EOL), so I am in charge of replacing the Data Access layer for this component. So on the one hand I think i should use Hibernate because that's what the rest of the application does, but on the other i think i should just use regular java.sql.* classes because my requirements are really straightforward and aren't expected to change any time soon. So my question is (and i understand it is subjective) at what point do you think that the added complexity of using an ORM tool (in terms of configuration, dependencies...) is worth it? UPDATE due to the way the DataAccesLayer for the main application was written (weird dependencies) i cannot easily use it, i would have to implement it myself.

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• CakePHP 2.0: how to access properties of the parent object?

  - by PaulJ

  I just started learning CakePHP 2.0 a few days ago, and there's one thing that is leaving me stumped: say I have an User model and a Posts model: class User extends AppModel { public $name = "User"; public $hasMany=array( 'Post' => array( 'className' => 'Post', 'foreignKey' => 'author_id' ) ); } class Post extends AppModel { public $name = 'Post'; public $belongsTo = array( 'className' = 'User', 'foreignKey' = 'author_id', ); } (Where "author_id" is the foreign key in the posts table that references the Users table's primary key). And now, in the PostsController, I want to access the properties of the user that owns the current post (to show his display name, for example). What would be the proper syntax? I tried: $this->Post->User->find('first', array('conditions' => array('User.id' => "$usuario"))) But it didn't work (I guess it's because the User is the parent of the Post object, not its child). Or should CakePHP load everything automatically, once you've declared the $hasMany and $belongsTo relationships?

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• Rails - Create if record doesn't exist or else update.....Whats Best way to do this?

  - by ChrisWesAllen

  Hi, I have a create statement for some models but its creating a record within a join table regardless if the record exist. Here is what my code looks like. @user = User.find(current_user) @event = Event.find(params[:id]) for interest in @event.interests @user.choices.create(:interest => interest, :score => 4) end The problem is it creates records no matter what. I would like it to create a record if it doesnt exist, if a record does exist I would just to it to take the attribute of the found record and add or subtract 1. So, I've been looking around and I see something called find_or_create_by. My question is what happens if it finds? Preferably if it finds,I would like to take the current :score attribute and +1. SO is it possible to find or create by id? I'm not sure what attribute I would find by since the model I'm looking at is a join model which only had id foreign keys and the score attribute. I tried @user.choices.find_or_create_by_user(:user => @user.id, :interest => interest, :score => 4) but got "undefined method `find_by_user'".....ANy ideas or help?

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• Rails how to return a list of answers with a specific question_id

  - by mytwocentsisworthtwocents

  Let's say I have two Models, Answers and Questions (there are others, but irrelevant to the question). The models are as follows: Answer.rb class Answer < ActiveRecord::Base attr_accessible :description, :question_id has_one :question, :through => :user, :dependent => :destroy validates :description, :presence => true end Question.rb class Question < ActiveRecord::Base attr_accessible :budget, :description, :headline, :user_id, :updated_at, :created_at belongs_to :user has_many :answers validates :headline, :description, :user_id, :presence => true end I'd like to display on a page a list of all answers associated with a question, and only those questions. I got this far. I believe this variable finds all the questions in the database by the question_id (foreign key): @findanswers = Answer.all(params[:question_id]) And this one grabs the the id of the current question (this code will reside as an ERB on the page where the current question is located): @questionshow = Question.find(params[:id]) And now I'm stuck. How do I put the two together so that I list all the answers with the current question id?

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• Actionscript flex sockets and telnet

  - by MAC

  I am trying to make a flex application where it gets data from a telnet connection and I am running into a weird problem. To give a brief introduction, i want to read data from a process that exposes it through a socket. So if in the shell i type telnet localhost 8651i receive the xml and then the connection is closed (I get the following Connection closed by foreign host.) Anyway i found a simple tutorial online for flex that essentially is a telnet client and one would expect it to work but everything follows Murphy's laws and nothing ever works! Now i have messages being printed in every event handler and all places that i can think off. When i connect to the socket nothing happens, no event handler is triggered even the connect or close handler and if i do the following the socket.connected returns false! I get no errors, try catch raises no exception. I am at a loss as to whats going wrong? socket.connect(serverURL, portNumber); msg(socket.connected.toString()); Is there something about telnet that i do not know and its causing this to not work. Whats more interesting is why none of the events get fired. Another interesting thing is that i have some python code that does the same thing and its able to get the xml back! The following is the python code that works! def getStats(host, port): sock = socket.socket() sock.connect((host, port)) res = sock.recv(1024*1024*1024, socket.MSG_WAITALL) sock.close() return statFunc(res) So i ask you whats going wrong!!!!!! Is there some inherent problem with how flex handles sockets?

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