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  • select all values from a dimension for which there are facts in all other dimensions

    - by ideasculptor
    I've tried to simplify for the purposes of asking this question. Hopefully, this will be comprehensible. Basically, I have a fact table with a time dimension, another dimension, and a hierarchical dimension. For the purposes of the question, let's assume the hierarchical dimension is zip code and state. The other dimension is just descriptive. Let's call it 'customer' Let's assume there are 50 customers. I need to find the set of states for which there is at least one zip code in which EVERY customer has at least one fact row for each day in the time dimension. If a zip code has only 49 customers, I don't care about it. If even one of the 50 customers doesn't have a value for even 1 day in a zip code, I don't care about it. Finally, I also need to know which zip codes qualified the state for selection. Note, there is no requirement that every zip code have a full data set - only that at least one zip code does. I don't mind making multiple queries and doing some processing on the client side. This is a dataset that only needs to be generated once per day and can be cached. I don't even see a particularly clean way to do it with multiple queries short of simply brute-force iteration, and there are a heck of a lot of 'zip codes' in the data set (not actually zip codes, but the there are approximately 100,000 entries in the lower level of the hierarchy and several hundred in the top level, so zipcode-state is a reasonable analogy)

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  • Django sub-applications & module structure

    - by Rob Golding
    I am developing a Django application, which is a large system that requires multiple sub-applications to keep things neat. Therefore, I have a top level directory that is a Django app (as it has an empty models.py file), and multiple subdirectories, which are also applications in themselves. The reason I have laid my application out in this way is because the sub-applications are separated, but they would never be used on their own, outside the parent application. It therefore makes no sense to distribute them separately. When installing my application, the settings file has to include something like this: INSTALLED_APPS = ( ... 'myapp', 'myapp.subapp1', 'myapp.subapp2', ... ) ...which is obviously suboptimal. This also has the slightly nasty result of requiring that all the sub-applications are referred to by their "inner" name (i.e. subapp1, subapp2 etc.). For example, if I want to reset the database tables for subapp1, I have to type: python manage.py reset subapp1 This is annoying, especially because I have a sub-app called core - which is likely to conflict with another application's name when my application is installed in a user's project. Am I doing this completely wrongly, or is there away to force these "inner" apps to be referred to by their full name?

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  • How to use named_scope to incrementally construct a complex query?

    - by wbharding
    I want to use Rails named_scope to incrementally build complex queries that are returned from external methods. I believe I can get the behavior I want with anonymous scopes like so: def filter_turkeys Farm.scoped(:conditions => {:animal => 'turkey'}) end def filter_tasty Farm.scoped(:conditions => {:tasty => true}) end turkeys = filter_turkeys is_tasty = filter_tasty tasty_turkeys = filter_turkeys.filter_tasty But say that I already have a named_scope that does what these anonymous scopes do, can I just use that, rather than having to declare anonymous scopes? Obviously one solution would be to pass my growing query to each of the filter methods, a la def filter_turkey(existing_query) existing_query.turkey # turkey is a named_scoped that filters for turkey end But that feels like an un-DRY way to solve the problem. Oh, and if you're wondering why I would want to return named_scope pieces from methods, rather than just build all the named scopes I need and concatenate them together, it's because my queries are too complex to be nicely handled with named_scopes themselves, and the queries get used in multiple places, so I don't want to manually build the same big hairy concatenation multiple times.

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  • URL development and mod_rewrite

    - by iRector
    My site is made-up of the main page, and multiple sub-directories, all under the same domain. My URLS are currently like .................| Ideal clean version: mysite.com mysite.com/?content=content1 ......................| mysite.com/content1/ mysite.com/?content=content2&page=4 ........| mysite.com/content2/4/ mysite.com/?content=content3 ......................| mysite.com/content3/ mysite.com/?content=content4 ......................| mysite.com/content4/ mysite.com/?content=article&id=34 ............| mysite.com/article/34/ Then the sub-directories are essentially the same: mysite.com/subdir, mysite.com/subdir2, mysite.com/subdir3, etc mysite.com/subdir/?content=content1 ...................| mysite.com/subdir/content1/ mysite.com/subdir/?content=content2&page=4 .....| mysite.com/subdir/content2/4/ mysite.com/subdir/?content=content3 ...................| mysite.com/subdir/content3/ mysite.com/subdir/?content=content4 ...................| mysite.com/subdir/content4/ mysite.com/subdir/?content=article&id=34 .........| mysite.com/subdir/article/34/ I've used mod_rewrite briefly, but I'm not sure how to approach these multiple variables. Also, how would I differentiate between the actually subfolders, and the content variable. As so to prevent 'subdir' or 'subdir2' from being plugged in as the content variable for the root site. I've played around with plenty of code snippets, but I've wiped my .htaccess slate clean, and approach you all in an attempt to help me repopulate it. Your input would thoroughly be appreciated. Note: The only time the page query string will be needed is when 'content' == 'content2' ?content=content2&page=4 **Same rule is shared by the article/id relationship, all other 'content' values are expected to be dynamic.

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  • Sharing a COM port over TCP

    - by guinness
    What would be a simple design pattern for sharing a COM port over TCP to multiple clients? For example, a local GPS device that could transmit co-ordinates to remote hosts in realtime. So I need a program that would open the serial port and accept multiple TCP connections like: class Program { public static void Main(string[] args) { SerialPort sp = new SerialPort("COM4", 19200, Parity.None, 8, StopBits.One); Socket srv = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp); srv.Bind(new IPEndPoint(IPAddress.Any, 8000)); srv.Listen(20); while (true) { Socket soc = srv.Accept(); new Connection(soc); } } } I would then need a class to handle the communication between connected clients, allowing them all to see the data and keeping it synchronized so client commands are received in sequence: class Connection { static object lck = new object(); static List<Connection> cons = new List<Connection>(); public Socket socket; public StreamReader reader; public StreamWriter writer; public Connection(Socket soc) { this.socket = soc; this.reader = new StreamReader(new NetworkStream(soc, false)); this.writer = new StreamWriter(new NetworkStream(soc, true)); new Thread(ClientLoop).Start(); } void ClientLoop() { lock (lck) { connections.Add(this); } while (true) { lock (lck) { string line = reader.ReadLine(); if (String.IsNullOrEmpty(line)) break; foreach (Connection con in cons) con.writer.WriteLine(line); } } lock (lck) { cons.Remove(this); socket.Close(); } } } The problem I'm struggling to resolve is how to facilitate communication between the SerialPort instance and the threads. I'm not certain that the above code is the best way forward, so does anybody have another solution (the simpler the better)?

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  • How to start with entity framework and service oriented architecture?

    - by citronas
    At work I need to create a new web application, that will connection to an MySql Database. (So far I only have expercience with Linq-To-Sql classes and MSSQL Servers.) My superior tells me to use the entity framework (he probably refers to Linq-To-Entity) and provide everything as a service based architecture. Unfortunatly nobody at work has experience with that framework and with a real nice server oriented architecture. (till now no customer wanted to pay for architecture that he can't see. This speficic project I'm leading will be long-term, meaning multiple years, so it would be best to design it the way, that multiple targetting plattforms like asp.net, c# wpf, ... could use it) For now, the main target plattform is ASP.net So I do have the following questions: 1) Where can I read best what's really behind service oriented architecture (but for now beginner tutorials work fine as well) and how to do it in best practise? 2) So far I can't seem a real difference between Linq-To-Sql classes and the information I've google so far on the 'entity framework'. So, whats the difference? Where do I find nice tutorials for it. 3) Is there any difference in the entity framework regarding the database server (MSSQL or MySQL). If not, does that mean that code snipperts I will stumble across will word database independent? 4) I do you Visual Studio 2010. Do I have to regard something specific?

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  • Dependency injection in constructors

    - by andre
    Hello everyone. I'm starting a new project and setting up the base to work on. A few questions have risen and I'll probably be asking quite a few in here, hopefully I'll find some answers. First step is to handle dependencies for objects. I've decided to go with the dependency injection design pattern, to which I'm somewhat new, to handle all of this for the application. When actually coding it I came across a problem. If a class has multiple dependencies and you want to pass on multiple dependencies via the constructor (so that they cannot be changed after you instantiate the object). How do you do it without passing an array of dependencies, using call_user_func_array(), eval() or Reflection? This is what i'm looking for: <?php class DI { public function getClass($classname) { if(!$this->pool[$classname]) { # Load dependencies $deps = $this->loadDependencies($classname); # Here is where the magic should happen $instance = new $classname($dep1, $dep2, $dep3); # Add to pool $this->pool[$classname] = $instance; return $instance; } else { return $this->pool[$classname]; } } } Again, I would like to avoid the most costly methods to call the class. Any other suggestions?

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  • Drupal 6 - I am using drupal_execute to insert a CCK node into my site. Everything is working excep

    - by rdurbin
    $form_state['values']['field_prx_mp3_labels'][0][value] = $mp3_labels; $form_state['values']['taxonomy'][0][value] = array('tags'=>array('1'=>'Music')); $errs = drupal_execute('prx_content_node_form', $form_state, (object) $nodeTmp); This is a Drupal 6 site. I am using drupal_execute to create a node programatically. The first line is working for field_prx_mp3_labels. The second (for taxonomy) is not. Here is what my select on the node add for my cck looks like: <select name="taxonomy[2][]" multiple="multiple" class="form-select" id="edit-taxonomy-2" size="9"><option value="">- None -</option><option value="5">Music</option><option value="6">-Rock/Pop</option><option value="7">-Jazz/Blues</option><option value="8">-Classical</option><option value="9">-Music Documentaries</option><option value="10">-Festivals/Concerts</option><option value="11">Arts</option><option value="19">-Literature</option><option value="12">Nature</option><option value="13">History</option><option value="15">-Music</option><option value="14">Culture</option><option value="17">-American Indian</option><option value="18">-Latino</option><option value="16">-Youth Perspective</option></select> I have tried many many variations for line 2 (relating to the taxonomy). This comment seemed close but it hasn't worked for me: http://drupal.org/node/178506#comment-1155576 Thanks!

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  • MySQL com_select?

    - by symcbean
    I'm looking to tune my query cache a bit. According to 7.6.3.4. Query Cache Status and Maintenance in the manual: The Com_select value is given by this formula: Qcache_inserts + Qcache_not_cached + queries with errors found during the column-privileges check However in 5.1.5. Server Status Variables it suggests that this is maintained by the DBMS. Having said that mysql> show status like 'Com_select%'; Always returns a value of 1 - and I'm pretty sure I've run more than one non-cached select query on my database since it started. It looks as if other people are similarly confused. Is this status variable redundant? Which bit of the manual is wrong? TIA

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  • Entity Framework and WCf

    - by Nihilist
    Hi I am little confused on designing WCf services with EF. When using WCf and EF, where do we draw this line on what properties to return and what not to with the entity. Here is my scenario I have User. Here are the relations. User [1 to many] Address, User [ 1 to many] Email, User [ 1 to many] Phone So now on the webform, on page1 I can edit user information. say I can edit few properties on the user entity and can also edit address, phone, email entities[ like add / delete and update any] On page2, i can only update user properties and nothing related to navigation properties [ address, email, phone]. So when I return the User Entity [ OR DTO] should i be returning the navigation properties too? Or should the client make multiple calls to get navigation properites. Also, how does it go with Save? Like should the client make multiple calls to save user and related entites or just one call to save the graph? Lets say, if I just have a Save(User user) [ where user has all the related entities too] both page1 and page2 will call save and pass me the user. but one page1 i will need a lot more information. but on page2 i just need the user primitive properties. So my question is, where do we draw this line, how do we design theses services ? Is the WCF operation designed on the page and the fields it has ? I am hoping i explained my problem well enough.

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  • How do I count how many arrays have the same name within a multidimensional array with php?

    - by zeckdude
    I have a multidimensional array, and I would have multiple arrays within it. Some of those arrays contain multiple arrays within them as well, and I would like to count how many arrays are within the second array(the date). This is an example of the structure of the multidimensional array: $_SESSION['final_shipping'][04/03/2010][book] $_SESSION['final_shipping'][04/12/2010][magazine] $_SESSION['final_shipping'][04/12/2010][cd] This is the foreach statement I am currently using to count how many of the second array(the one with the dates) exists. foreach($_SESSION['final_shipping'] as $date_key => $date_value) { foreach ($date_value as $product_key => $product_value) { echo 'There are ' . count($date_key) . ' of the ' . $date_key . ' selection.<br/>'; } } It is currently outputting this: There are 1 of the 04/03/2010 selection. There are 1 of the 04/12/2010 selection. There are 1 of the 04/12/2010 selection. I would like it to output this: There are 1 of the 04/03/2010 selection. There are 2 of the 04/12/2010 selection.

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  • if exist !SOMEPATH! not working in batch file

    - by akash
    I have a batch script in which i am using multiple if exist statement, the problem is all statements are working except one . Following variables are set SETLOCAL ENABLEDELAYEDEXPANSION SET basedrive=E: SET tfworkspace=!basedrive!\TFS SET envdefault=%1 SET projenv=!envdefault! echo subapp=!subapp! subappservice=!subappservice! SET tfworkspacepath=!tfworkspace!\!releasebranch!\!app!\!subapp! SET tfworkspacepathservice=!tfworkspace!\!releasebranch!\!app!\!subapp!\sourcecode\build\!projenv! This statement works, if exist "!tfworkspacepath!" (robocopy "!tfworkspacepath!"\sourcecode\messagebroker\ /E /NFL /NJS /NDL /ETA "!basedir!\!messagebroker!" ) else SET /a foldererror=1 This statement doesn't work, by does not work i mean even thou the path does not exist it it still tries to robocopy. if exist !tfworkspacepathservice! ( robocopy !tfworkspacepathservice! /E /NFL /NJS /NDL /ETA "!basedir!\!scripts!") else SET /a foldererror =!foldererror!+1 I am new to batch writing, please guide me

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  • How do I handle the messages for a simple web-based live chat, on the server side?

    - by Carson Myers
    I'm building a simple live chat into a web application running on Django, but one thing I'm confused about is how I should store the messages between users. The chat will support multiple users, and a chat "session" is composed of users connected to one user that is the "host." The application is a sort of online document collaboration thing, so user X has a document, and users Y and Z would connect to user X to talk about the document, and that would be one chat session. If user Y disconnected for five minutes, and then signed back in and reconnected to user X, he should not get any of the messages shared between users X and Z while he was away. if users X, Y, and Z can have a chat session about user X's document, then users X and Y can connect to a simultaneous, but separate discussion about user Z's document. How should I handle this? Should I keep each message in the database? Each message would have an owner user and a target user (the host), and a separate table would be used to connect users with messages (which messages are visible to what users). Or should I store each session as an HTML file on the server, which messages get appended to? The problem is, I can't just send messages directly between clients. They have to be sent to the server in a POST request, and then each client has to periodically check for the messages in a GET request. Except I can't just have each message cleared after a client fetches it, because there could be multiple clients. How should I set this up? Any suggestions?

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  • No grammar constraints (DTD or XML schema) detected for the document.

    - by fastcodejava
    I have this dtd : http://fast-code.sourceforge.net/template.dtd But when I include in an xml I get the warning : No grammar constraints (DTD or XML schema) detected for the document. The xml is : <?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE templates PUBLIC "//UNKNOWN/" "http://fast-code.sourceforge.net/template.dtd"> <templates> <template type="type"> <description>Some</description> <variation></variation> <variation-field></variation-field> <allow-multiple-variation></allow-multiple-variation> <class-pattern></class-pattern> <getter-setter>setter</getter-setter> <allowed-file-extensions>java</allowed-file-extensions> <number-required-classes>1</number-required-classes> <template-body> <![CDATA[ Some Data ]]> </template-body> </template> </templates> Any clue?

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  • Multi-reader IPC solution?

    - by gct
    I'm working on a framework in C++ (just for fun for now), that lets the user write plugins that use a standard API to stream data between each other. There's going to be three basic transport mechanisms for the data: files, sockets, and some kind of IPC piping system. The system is set up so that for the non-file transport, each stream can have multiple readers. IE once a server socket it setup, multiple computers can connect and stream the data. I'm a little stuck at the multi-reader IPC system though. All my plugins run in threads so they live in the same address space, so some kind of shared memory system would work fine, I was thinking I'd write my own circular buffer with a write pointer and read pointers chassing it around the buffer, but I have my doubts that I can achieve the same performance as something like linux pipes. I'm curious what people would suggest for a multi-reader solution to something like this? Is the overhead for pipes or domain sockets low enough that I could just open a connection to each reader and issue separate writes to each reader? This is intended to be significant volumes of data (tens of mega-samples/sec), so performance is a must.

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  • Database schema for a library

    - by ABach
    Hi all - I'm designing a library management system for a department at my university and I wanted to enlist your eyes on my proposed schema. This post is primarily concerned with how we store multiple copies of each book; something about what I've designed rubs me the wrong way, and I'm hoping you all can point out better ways to tackle things. For dealing with users checking out books, I've devised three tables: book, customer, and book_copy. The relationships between these tables are as follows: Every book has many book_copies (to avoid duplicating the book's information while storing the fact that we have multiple copies of that book). Every user has many book_copies (the other end of the relationship) The tables themselves are designed like this: ------------------------------------------------ book ------------------------------------------------ + id + title + author + isbn + etc. ------------------------------------------------ ------------------------------------------------ customer ------------------------------------------------ + id + first_name + first_name + email + address + city + state + zip + etc. ------------------------------------------------ ------------------------------------------------ book_copy ------------------------------------------------ + id + book_id (FK to book) + customer_id (FK to customer) + checked_out + due_date + etc. ------------------------------------------------ Something about this seems incorrect (or at least inefficient to me) - the perfectionist in me feels like I'm not normalizing this data correctly. What say ye? Is there a better, more effective way to design this schema? Thanks!

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  • How to Detect that Current (Bash) Shell is a (Vi/Vim) Subshell?

    - by Jeet
    From inside Vi/Vim, I can type: :shell to drop into a shell. Is there any way to detect that I am in a Vi-spawned subshell? The environmental variable SHLVL is 2, but that does not tell me explicitly that I am in a Vi/Vim-spawned subshell. On OS X, the following variables are also set: MYVIMRC, VIMRUNTIME, VIM. How universal are these? Can I count on these being set in any system, if and only if I am in a Vi/Vim subshell? If not, is there any portable, robust and hopefully efficient way to tell that I am in a Vi/Vim subshell? Thanks.

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  • Select return dynamic columns

    - by Ascalonian
    I have two tables: Standards and Service Offerings. A Standard can have multiple Service Offerings. Each Standard can have a different number of Service Offerings associated to it. What I need to be able to do is write a view that will return some common data and then list the service offerings on one line. For example: Standard Id | Description | SO #1 | SO #2 | SO #3 | ... | SO #21 | SO Count 1 | One | A | B | C | ... | G | 21 2 | Two | A | | | ... | | 1 3 | Three | B | D | E | ... | | 3 I have no idea how to write this. The number of SO columns is set to a specific number (21 in this case), so we cannot exceed past that. Any ideas on how to approach this? A place I started is below. It just returned multiple rows for each Service Offering, when they need to be on one row. SELECT * FROM SERVICE_OFFERINGS WHERE STANDARD_KEY IN (SELECT STANDARD_KEY FROM STANDARDS)

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  • Event handle in drop-down menu.

    - by QLiu
    Hello fellows, I am trying to develop a dynamic drop down menu by a customized widget style The custom widget has two main features: Read user's location cookies variable to set the proper contact phone number in the CP pages When users select on the drop down menu, it triggers onChange event, it re-select the contact phone number based on users' selections, but it won't reset the location cookies. My widgets conatins two files: Controller.php: Simply one, it uses to handle get cookies variables class serial extends Widget { function __construct() { parent::__construct(); } function generateWidgetInformation() { $this->info['notes'] = "Serial Number search Box"; } function getData() { //Get cookies code will go here, and pass to view.php $this->data['locale'] = 'gb';// for test purpose now } } view.php is about Presentation layer contains HTML, which get the data from my controller <div style="border: 1px solid black; display: block;" id="<?=$this->instanceID;?>"></div> <script>locale2contact('<?=$this->data['locale']?>', '<?=$this->instanceID;?>');</script> And then the Javascript function, call locale2contact var element_id =''; //Define Global Variables, //Receive the cookies locale, and instance id from view.php function locale2contact(locale, instance_id) { var details = ''; this.element_id=instance_id; //assing the instance id into global variable // alert(instance_id); //Check whether we got the instance id from view files if (locale == 'gb') details = 'UK Contact Details<br>' + build_dropdown(locale); else if (locale == 'fr') details = 'French Contact Details<br>'+build_dropdown(locale); else if (locale == 'be') details = 'Belgian Contact Details<br>'+ build_dropdown(locale); else details = 'Unknown Contact Detail'; writeContactInfo(details); } //Build the drop down menu with pre-selected option by using cookies. function build_dropdown(locale) { var dropdown = '<select onChange=changeContactInfo(this.options[selectedIndex].text)>'; dropdown += '<option' + (locale == 'gb' ? ' selected' : '') + '>UK</option>'; dropdown += '<option' + (locale == 'be' ? ' selected' : '') + '>Belgium</option>'; dropdown += '</select>'; return dropdown; } // Not smart way in here, once the people select the drop down box, it reselect the drop down menu and reset the contact info function changeContactInfo(selected) { var details =''; //alert(this.element_id); //alert(locale); if (selected == 'UK') details = 'UK Contact Details<br>' + build_dropdown2(selected); else if (selected == 'fr') details = 'French Contact Details<br>'+ build_dropdown2(selected); else if (selected == 'Belgium') details = 'Belgian Contact Details<br>'+ build_dropdown2(selected); else details = 'Unknown Contact Detail'; writeContactInfo(details); } //Build the drop down menu function build_dropdown2(selected) { var dropdown = '<select onChange=changeContactInfo(this.options[selectedIndex].text)>'; dropdown += '<option' + (selected == 'UK' ? ' selected' : '') + '>UK</option>'; dropdown += '<option' + (selected == 'Belgium' ? ' selected' : '') + '>Belgium</option>'; dropdown += '</select>'; return dropdown; } //Back to view function writeContactInfo(details) { document.getElementById(this.element_id).innerHTML = details; //update the instance field in view } Javascript function is not efficient. As you see, I got two similar duplicate functions to handle events. Users go to the page, the widget read the cookies variable to display contact info (locale2contact)and preselect the drop-down menu (function build_dropdown) If users select the drop down menu, the displya contact info change (function changeContactInfo), and then I need to rebuild the drop down menu with user previously selection (function build_dropdown2). I am looking for best practices for adding this functionality to RightNow widget. Thank you. I really do not like the way i am doing now. It works; but the code looks bad.

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  • What are good and bad jitter times for a LAN

    - by garyb32234234
    Ive just ran jperf (frontend to iperf) on our network between 2 workstations, its recorded jitter between 0.033ms and 0.048ms. Is this good or bad? Are there more variables that i would need to consider to make the decision? EDIT: TCP/IP Ethernet LAN 43 PCs 1 server, 100Mbits main switch, various small 8 port switches, test was done using UDP, Its a Windows Domain. I want to instal a few voip softphones on the workstations, see how many i can use that reliably work, im testing a few different workstations around the network to see where the best quality network paths are. Will also change some equipment if i identify bad connections.

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  • Resource mapping in a Ruby on Rails URL (RESTful API)

    - by randombits
    I'm having a bit of difficulty coming up with the right answer to this, so I will solicit my problem here. I'm working on a RESTFul API. Naturally, I have multiple resources, some of which consist of parent to child relationships, some of which are stand alone resources. Where I'm having a bit of difficulty is figuring out how to make things easier for the folks who will be building clients against my API. The situation is this. Hypothetically I have a 'Street' resource. Each street has multiple homes. So Street :has_many to Homes and Homes :belongs_to Street. If a user wants to request an HTTP GET on a specific home resource, the following should work: http://mymap/streets/5/homes/10 That allows a user to get information for a home with the id 10. Straight forward. My question is, am I breaking the rules of the book by giving the user access to: http://mymap/homes/10 Technically that home resource exists on its own without the street. It makes sense that it exists as its own entity without an encapsulating street, even though business logic says otherwise. What's the best way to handle this?

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  • django join-like expansion of queryset

    - by jimbob
    I have a list of Persons each which have multiple fields that I usually filter what's upon, using the object_list generic view. Each person can have multiple Comments attached to them, each with a datetime and a text string. What I ultimately want to do is have the option to filter comments based on dates. class Person(models.Model): name = models.CharField("Name", max_length=30) ## has ~30 other fields, usually filtered on as well class Comment(models.Model): date = models.DateTimeField() person = models.ForeignKey(Person) comment = models.TextField("Comment Text", max_length=1023) What I want to do is get a queryset like Person.objects.filter(comment__date__gt=date(2011,1,1)).order_by('comment__date') send that queryset to object_list and be able to only see the comments ordered by date with only so many objects on a page. E.g., if "Person A" has comments 12/3/11, 1/2/11, 1/5/11, "Person B" has no comments, and person C has a comment on 1/3, I would see: "Person A", 1/2 - comment "Person C", 1/3 - comment "Person A", 1/5 - comment I would strongly prefer not to have to switch to filtering based on Comments.objects.filter(), as that would make me have to largely repeat large sections of code in the both the view and template. Right now if I tried executing the following command, I will get a queryset returning (PersonA, PersonC, PersonA), but if I try rendering that in a template each persons comment_set will contain all their comments even if they aren't in the date range. Ideally they're would be some sort of functionality where I could expand out a Person queryset's comment_set into a larger queryset that can be sorted and ordered based on the comment and put into a object_list generic view. This normally is fairly simple to do in SQL with a JOIN, but I don't want to abandon the ORM, which I use everywhere else.

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  • Locked out by changing file permissions

    - by Valeriy
    I just locked my root account (and all other accounts if it matters) completely out of the RHEL 5.4 by changing permissions on every file to 400. Now I have "Permission denied" on any command that I try to run, including chmod itself. Any idea on how to recover? The only access I have to the server is via terminal or SSH. (If anyone cares how it happened, I was running a hardening script and one of the lines was supposed to change permission on some config files in /etc directory. It has couple of variables that had not been set, so the command essentially evaluated to chmod -R 0400 /* Ouch! This is sure a great lesson on checking the scripts even more carefully in the future but what can I do now?

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  • How to design data storage for partitioned tagging system?

    - by Morgan Cheng
    How to design data storage for huge tagging system (like digg or delicious)? There is already discussion about it, but it is about centralized database. Since the data is supposed to grow, we'll need to partition the data into multiple shards soon or later. So, the question turns to be: How to design data storage for partitioned tagging system? The tagging system basically has 3 tables: Item (item_id, item_content) Tag (tag_id, tag_title) TagMapping(map_id, tag_id, item_id) That works fine for finding all items for given tag and finding all tags for given item, if the table is stored in one database instance. If we need to partition the data into multiple database instances, it is not that easy. For table Item, we can partition its content with its key item_id. For table Tag, we can partition its content with its key tag_id. For example, we want to partition table Tag into K databases. We can simply choose number (tag_id % K) database to store given tag. But, how to partition table TagMapping? The TagMapping table represents the many-to-many relationship. I can only image to have duplication. That is, same content of TagMappping has two copies. One is partitioned with tag_id and the other is partitioned with item_id. In scenario to find tags for given item, we use partition with tag_id. If scenario to find items for given tag, we use partition with item_id. As a result, there is data redundancy. And, the application level should keep the consistency of all tables. It looks hard. Is there any better solution to solve this many-to-many partition problem?

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  • NSFetchedResultsController on secondary UITableView - how to query data?

    - by Jason
    I am creating a core-data based Navigation iPhone app with multiple screens. Let's say it is a flash-card application. The data model is very simple, with only two entities: Language, and CardSet. There is a one-to-many relationship between the Language entity and the CardSet entities, so each Language may contain multiple CardSets. In other words, Language has a one-to-many relationship Language.cardSets which points to the list of CardSets, and CardSet has a relationship CardSet.language which points to the Language. There are two screens: (1) An initial TableView screen, which displays the list of languages; and (2) a secondary TableView screen, which displays the list of CardSets in the Language. In the initial screen, which lists the languages, I am using NSFetchedResultsController to keep the list of languages up-to-date. The screen passes the Language selected to the secondary screen. On the secondary screen, I am trying to figure out whether I should again use an NSFetchedResultsController to maintain the list of CardSets, or if I should work through Language.cardSets to simply pull the list out of the object model. The latter makes the most sense programatically because I already have the Language - but then it would not automatically be updated on changes. I have looked at the NSFetchedResultsController documentation, and it seems like I can easily create predicates based on attributes - but not relationships. I.e., I can create the following NSFetchedResultsController: NSPredicate *predicate = [NSPredicate predicateWithFormat:@"name LIKE[c] 'Chuck Norris'"]; How can I access my data through the direct relationship - Language.cardSets - and also have the table auto-update using NSFetchedResultsController? Is this possible?

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