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• Django - categories & sub-categories

  - by Bluey

  Some advice needed on how I can structure my models for my site. I have seen this post from Django project but still a little lost. Also come across Django-MPTT - but that's no help and possibly overkill. I'm looking to have categories & subcategories that are shown in the URLs like this: mysite.com/Level1/Maths/Calculations/Addition/ mysite.com/Level3/English/ mysite.com/Level2/English/Storytelling/ In my admin interface I'm looking to have drop downs for each level of category or subcategory. Also at each level I will be querying items (another model) like get all items that have the category 'Level1' AND 'Maths'. There could also be a situation where I have five or more subcategories. How is it best to create my models for best performance? It it worth using tagging instead?

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• Django IN query as a string result - invalid literal for int() with base 10

  - by bmelton

  Trying to query a 'Favorites' model to get a list of items a user has favorited, and then querying against a different model to get the objects back from that query to present to the template, but I'm getting an error: "invalid literal for int() with base 10" Looking over all of the other instances of that error, I couldn't find any in which the asker actually wanted to work with a comma separated list of integers, so I'm kind of at a loss. Model class Favorite(models.Model): # key should be the model name, id is the model.id, and user is the User object. key = models.CharField(max_length=255, unique=True) val = models.IntegerField(default=0) user = models.ForeignKey(User) class Admin: list_display = ('key', 'id', 'user') View def index(request): favorites = Favorite.objects.filter(key='blog', user=request.user.pk) values = "" for favorite in favorites: values += "%s," % favorite.val #values = "[%s]" % values blogs = Blog.objects.filter(pk__in=values) return render_to_response('favorite/index.html', { "favorites" : favorites, "blogs" : blogs, "values" : values, }, context_instance=RequestContext(request) ) enter code here

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• Hierarchical data in Linq - options and performance

  - by Anthony

  I have some hierarchical data - each entry has an id and a (nullable) parent entry id. I want to retrieve all entries in the tree under a given entry. This is in a SQL Server 2005 database. I am querying it with LINQ to SQL in C# 3.5. LINQ to SQL does not support Common Table Expressions directly. My choices are to assemble the data in code with several LINQ queries, or to make a view on the database that surfaces a CTE. Which option (or another option) do you think will perform better when data volumes get large? Is SQL Server 2008's HierarchyId type supported in Linq to SQL?

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• dbpedia auto-suggest labels

  - by Sid

  Wikipedia has a auto-suggest feature on its search field. If you for instance type in "mars" it lists a few items including Mars, Marseille, Marsh. I am looking to implement something similar working off the latest DBpedia export (wikipedia in database form). If I do a search for all labels in the labels_en.nt file that DBpedia offer that begin with "mars" then, even if I remove ones that redirect on to others that are listed, I end up with a huge list. In trying to understand how wikipedia does this I noticed that I'm actually querying this URL which returns a JSON string. Now my problem is that I don't know how wikipedia narrows the list down. Perhaps it does so based on page popularity. The higher views/edits a page has the higher it goes in this suggestion box. If so, does DBpedia export this information?

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• Postgresql 8.4 reading OID style BLOBs with Hibernate

  - by peter

  I am getting this weird case when querying Postgres 8.4 for some records with Blobs (of type OIDs) with Hibernate. The query does return all right but when my code wants to read the content of the BLOB with the simple code below, it gets 0 bytes back public static byte[] readBlob(Blob blob) throws Exception { InputStream is = null; try { is = blob.getBinaryStream(); return org.apache.commons.io.IOUtils.toByteArray(is); } finally { if (is != null) try { is.close(); } catch(Exception e) {} } } Funny think is that I am getting this behavior only since I've started adding more then one such records to the table. The underlying JDBC library is type 3 (postgresq 8.4-701). Can someone give me a hint as to how to solve this issue? Thanks Peter

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• Doctrine Mssql uniqueidentifier isn't cast as char or nvarchar when retrieved from the database.

  - by Tres

  When I retrieve a record from the database which has a column of type "uniqueidentifier", Doctrine fills it with "null" rather than the unique id from the database. Some research and testing has brought this down to a PDO/dblib driver issue. When directly querying via PDO, null is returned in place of the unique id. For reference, http://trac.doctrine-project.org/ticket/1096, has a bit on this, however, it was updated 11 months ago with no comment for resolution. A way around this, as mentioned at http://bugs.php.net/bug.php?id=24752&edit=1, is to cast the column as a char. However, it doesn't seem Doctrine exposes the native field type outside of generating models which makes it a bit hard to detect uniqueidentifier types and cast them internally when building the sql query. Has anyone found a workaround for this?

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• Wiki Database, is there one?

  - by Faiz

  I was searching the net for something like a wiki database, just like wikipedia but instead stores structured content, editable by users. What I was looking for was an online database accessible by everyone where people can design the schema and data with proper versioning of both schema and data. I couldn't find any such site. I am not sure if it is my search skills or if there really is no wiki database as of now. Does anyone out there know anything like this? I think there is a great potential for something like this. A possible example will be a website with a GUI for querying a MySQL DB where any website visitor can create DB objects and populate data.

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• PHP-GD: Dealing with Unicode characters

  - by sehugg

  I am developing a web service that renders characters using the PHP GD extension, using a user-selected TTF font. This works fine in ASCII-land, but there are a few problems: The string to be rendered comes in as UTF-8. I would like to limit the list of user-selectable fonts to be only those which can render the string properly, as some fonts only have glyphs for ASCII characters, ISO 8601, etc. In the case where some decorative characters are included, it would be fine to render the majority of characters in the selected font and render the decorative characters in Arial (or whatever font contains the extended glyphs). It does not seem like PHP-GD has support for querying the font metadata sufficiently to figure out if a character can be rendered in a given font. What is a good way to get font metrics into PHP? Is there a command-line utility that can dump in XML or other parsable format?

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• Yet another date formatting problem :(

  - by Jonesy

  Hi folks, I seem to have a date formatting problem every day! I am querying a table and am getting a date back in the format dd/mm/yyyy (as a string btw). Brilliant! thats what I want. But, now I want to convert that string to a date so i can do dim dayNumber as integer = day.DayOfWeek But when I convert it to a date it changes it to #m/dd/yyyy#. AHHHH! how can I change this? Cheers

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• C# Linq Entity Conversion Error on Nonexistent Value?

  - by Ryan

  While trying to query some data using the Linq Entity Framework I'm receiving the following exception: {"Conversion failed when converting the varchar value '3208,7' to data type int."} The thing that is confusing is that this value does not even exist in the view I am querying from. It does exist in the table the view is based on, however. The query I'm running is the following: return context.vb_audit_department .Where(x => x.department_id == department_id && x.version_id == version_id) .GroupBy(x => new { x.action_date, x.change_type, x.user_ntid, x.label }) .Select(x => new { action_date = x.Key.action_date, change_type = x.Key.change_type, user_ntid = x.Key.user_ntid, label = x.Key.label, count = x.Count(), items = x }) .OrderByDescending(x => x.action_date) .Skip(startRowIndex) .Take(maximumRows) .ToList(); Can somebody explain why LINQ queries the underlying table instead of the actual view, and if there is any way around this behavior?

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• How to create a custom ADO Multi Dimensional Catalog with no database

  - by Alan Clark

  Does anyone know of an example of how to dynamically define and build ADO MD (ActiveX Data Objects Multidimensional) catalogs and cube definitions with a set of data other than a database? Background: we have a huge amount of data in our application that we export to a database and then query using the usual SQL joins, groups, sums etc to produce reports. The data in the application is originally in objects and arrays. The problem is the amount of data is so large the export can take 2 hours. So I am trying to figure out a good way of querying the objects in memory, either by a custom OLAP algorithm or library, or ADO MD. But I haven't been able to find an example of using ADO MD without a database behind it. We are using Delphi 2010 so would use ADO ActiveX but I imagine the ADO.NET MD is similar. I realize that if the application data was already stored in a database the problem would solve itself. Also if Delphi had LINQ capability I could query the objects and arrays that way.

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• Subsonic SQLite Multiple Files

  - by Marcus Vinicius de LIma

  Hi, I have an application that must be accessed for many users. To optimize the performance I intend to store each user profile information at a independant database file. I need everytime a user login the application, to setup a new provider linked with his own database. All databases have the same structure. So while querying user the commom generated DAL classes must switch for the database file relative the the user. Is there a way for configure SubSonic for doing that switch at runtime? Thanks.

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• Google datastore stats

  - by Keyur

  I am querying the __Stat_Kind__ kind. It does not return me entities about kinds that currently exist in the datastore but it includes entities about kinds that I had deleted more than a week ago. I am not so much concerned about it returning me the non-existent kinds - the doc does mention this scenario after all. But I am concerned that it does not return me info about my current kinds. Is this a known issue or am I doing something wrong? To folks on the app engine team: Also, on the dev server neither __Stat_Kind__ nor __Stat_Total__ return any entities. Which means I need to deploy my app to appspot before I can test this behavior. It would be nice if the dev server did return some basic info. Thanks, Keyur

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• how to implement color search with sphinx?

  - by harald

  hello, searching a photo by dominant colors using mysql is quite simple. assuming that the r,g,b values of the most dominant colors of the photo is already stored in the database, this could be achieved for example by something like: SELECT * FROM colors WHERE ABS(dominant_r - :r) < :threshold AND ABS(dominant_g - :g) < :threshold AND ABS(dominant_b - :b) < :threshold i wonder, if it's anyhow possible to store the colors in sphinx and perform the querying using the sphinx search engine? thanks!

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• Guide for http://www.ch-werner.de/javasqlite java wrapper library for SQlite?

  - by Tom Nielsen

  I'm working on a large computer science school project using java and SQlite. After finding out that the zentus.org wrapper errors on databases with ON DELETE and ON UPDATE clauses set, I have changed to the other wrapper found at http://www.ch-werner.de/javasqlite. However, I find the documentation lacking somewhat when trying to get an overview on how it works and how to use it, and the function descriptions are very very short, and you have to scan through every function and somewhat guess how they work and what they do. I wasn't able to find any guides on google on how to use it. My question: Does anyone know a link for a guide or tutorial for the ch-werner.de/javasqlite wrapper, or else can give me a basic code example, or give a quick overview of querying the database and the most used functions, and how to use them?

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• MySQL Need help constructing query: join multiple tables into single row

  - by Jed Daniels

  Hello stackoverflowers, Forgive me if this question has been asked and answered, I've searched and found a few that look similar but I'm too much of a novice with SQL to adapt them to my needs. Also forgive me if I don't use the correct terminology, I know it can be annoying when someone asks a question and they don't even know enough to be able to ask for what they need. I'm helping a friend gather some data, and need to perform a query that results in a single row per record, but instead I get multiple rows. Here is an example of what I'm querying right now (simplified, hopefully not too much): SELECT * FROM `table_one` AS t1 INNER JOIN `table_two` AS t2 ON t1.id = t2.id INNER JOIN `table_three` AS t3 ON t1.id = t3.id WHERE 1 The result is: id text number 5 Subtotal 17 5 Tax 3 5 Total 20 What I need is to create a query that results in something more like this: id text number text number text number 5 subtotal 17 Tax 3 Total 20 Any assistance/guidance would be much appreciated. Thanks! --jed

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• Entity framework - exclude list of values

  - by DutrowLLC

  Is there a way to exclude a list of values for an object attribute when querying the database through entity framework? I tried to be slick and pull this number: List<String> StringList = new List<String>(); StringList.Add("ya_mama"); StringList.Add("has"); StringList.Add("fleas"); servicesEntities context = new servicesEntities(); var NoFleasQuery = (from x in context.person where !StringList.Any(y => y.CompareTo(x.the_string_I_dont_want_it_to_be) == 0) // <--- the part where I thought I was slick select x); ...it compiled, but after I ran it, it gave me this error: Unable to create a constant value of type 'Closure type'. Only primitive types ('such as Int32, String, and Guid') are supported in this context. 'Closure type'???? How about MY closure!!! Entity framework... you broke my heart.

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• How to establish a two-way communication between Activity and Service in different process?

  - by steff

  Hi everyone, I'm working on establishing a two-way communication between an Activity and a Service which runs in a different process. Querying the process from the Activity is no big deal. But I want the process to notify the Activity on events. The idea behind it is this: the service runs independently from the actual app. It queries a webserver periodically. If a new task is found on the webserver the process should notify the activity. I found this thread over at AndDev.org but it doesn't seem to work for me. I've been messing around with BroadcastReceiver. I've implemented an interface which should notify the Activity but the problem is that the listener is always null since the Broadcast from the process is done via Intent, hence the class that extends BroadcastReceiver will be newly instantiated. How can I establish a 2-way communication? This has to be possible. Thanks for any help, steff

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• Remove Duplicates from List of HashMap Entries

  - by HonorGod

  I have a List<HashMap<String,Object>> which represents a database where each list record is a database row. I have 10 columns in my database. There are several rows where the values of 2 particular columns are equals. I need to remove the duplicates from the list after the list is updated with all the rows from database. What is the efficient way? FYI - I am not able to do distinct while querying the database, because the GroupName is added at a later stage to the Map after the database is loaded. And since Id column is not primary key, once you add GroupName to the Map. You will have duplicates based on Id + GroupName combination! Hope my question makes sense. Let me know if we need more clarification.

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• Fast single thread comet server, possible?

  - by Pepijn

  I recently encountered a few cases where a server would distribute an event stream that contains the exact same data for all listeners, such as a 'recent activity' box. It occurred to me that it is quite strange and inefficient to have a server like Apache run a thread processing and querying the database for every single comet stream containing the same data. What I would do for those global(not per user) streams is run a single thread that continuously emits data, and a new (green)thread for every new request that outputs the headers and then 'merges' into the main thread. Is it possible for one thread to serve multiple sockets, or for multiple clients to listen to the same socket? An example o = event # threads received | a b # 3 o / / # 3 - |/_/ | # 1 o c # 2 a, b | / o/ # 2 a, b o # 1 a, b, c | # connection b closed o # 1 a, c Does something like this exist? Would it work? Is it possible to do? Disclaimer: I'm not a server expert.

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• Subsonic linq using activerecord very slow compared to simplerepository

  - by skiik

  Anyone know anything about why linq queries are about 6 times slower when querying using active record vs simplerepository? The below code runs 6 times slower than when i query the data using a simple repository. This code is executed 1000 times in a loop Thanks in advance string ret = ""; // if (plan == null) { plan =VOUCHER_PLAN.SingleOrDefault(x => x.TENDER_TYPE == tenderType); } if (plan == null) throw new InvalidOperationException("voucher type does not exist." + tenderType); seq = plan.VOUCHER_SEQUENCES.First(); int i = seq.CURRENT_NUMBER; seq.CURRENT_NUMBER += seq.STEP; seq.Save();

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• Declarative JDOQL vs Single-String JDOQL : performance

  - by DrDro

  When querying with JDOQL is there a performance difference between using the declarative version and the Single-String version: Example from the JDOQL doc: //Declarative JDOQL : Query q = pm.newQuery(org.jpox.Person.class, "lastName == \"Jones\" && age < age_limit"); q.declareParameters("double age_limit"); List results = (List)q.execute(20.0); //Single-String JDOQL : Query q = pm.newQuery("SELECT FROM org.jpox.Person WHERE lastName == \"Jones\"" + " && age < :age_limit PARAMETERS double age_limit"); List results = (List)q.execute(20.0); Other then performance, are there any reasons for which one is better to use then the other or is it just about the one with which we feel more comfortable.

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• NHibernate Query object collection issue

  - by Mahesh

  Hi, I am new to NHibernate and need some information regarding the internal working of the engine: I have a table called Student and the design is as follows: RollNo Name City Postcode and there are 5 more columns like this. I have School class and mappings associated with it. I am querying RollNo and Name using session as given below: IQuery query = session.CreateQuery("SELECT RollNo,Name FROM Student); Executing query.List resulting in error because the query is returning object[][]. Now, I changed the query as given below: IQuery query = session.CreateQuery("FROM Student); Executing query.List on this query yeilds the desired results. But, the results contain more data than I want. Could you please let me know the query to which I can get RollNo and Name from Student and castable as Student collection. Thanks, Mahesh

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• in-memory database in Python

  - by Claudiu

  I'm doing some queries in Python on a large database to get some stats out of the database. I want these stats to be in-memory so other programs can use them without going to a database. I was thinking of how to structure them, and after trying to set up some complicated nested dictionaries, I realized that a good representation would be an SQL table. I don't want to store the data back into the persistent database, though. Are there any in-memory implementations of an SQL database that supports querying the data with SQL syntax?

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• Pros and cons of ways of storing an unsigned int without an unsigned int data type

  - by fields

  I have values that are 64-bit unsigned ints, and I need to store them in mongodb, which has no unsigned int type. I see three main possibilities for storing them in other field types, and converting on going in and out: Using a signed int is probably easiest and most space efficient, but has the disadvantage that they're not human readable and if someone forgets to do the conversion, some of them will work, which may obscure errors. Raw binary is probably most difficult for inexperienced programmers to deal with, and also suffers from non-human-readability. A string representation is the least space efficient (~40 bytes in unicode vs 8 bytes per field), but then at least all of the possible values will map properly, and for querying only a conversion to string is required instead of a more complicated conversion. I need these values to be available from different platforms, so a single driver-specific solution isn't an option. Any major pros and cons I've missed? Which one would you use?

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