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• Why this code generates different numbers?

  - by frbry

  Hello, I have this function that creates a unique number for hard-disk and CPU combination. DWORD hw_hash() { char drv[4]; char szNameBuffer[256]; DWORD dwHddUnique; DWORD dwProcessorUnique; DWORD dwUniqueKey; char *sysDrive = getenv ("SystemDrive"); strcpy(drv, sysDrive); drv[2] = '\\'; drv[3] = 0; GetVolumeInformation(drv, szNameBuffer, 256, &dwHddUnique, NULL, NULL, NULL, NULL); SYSTEM_INFO si; GetSystemInfo(&si); dwProcessorUnique = si.dwProcessorType + si.wProcessorArchitecture + si.wProcessorRevision; dwUniqueKey = dwProcessorUnique + dwHddUnique; return dwUniqueKey; } It returns different numbers if I format my hard-disk and install a new Windows. Any ideas, why? Thank you. Edit: OK, Got it: This function returns the volume serial number that the operating system assigns when a hard disk is formatted. To programmatically obtain the hard disk's serial number that the manufacturer assigns, use the Windows Management Instrumentation (WMI) Win32_PhysicalMedia property SerialNumber. I should do more research before posting my problems online. Sorry to bother you, let's keep this here in case anybody else can need it.

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• Web Shop Schema - Document Db

  - by Maxem

  I'd like to evaluate a document db, probably mongo db in an ASP.Net MVC web shop. A little reasoning at the beginning: There are about 2 million products. The product model would be pretty bad for rdbms as there'd be many different kinds of products with unique attributes. For example, there'd be books which have isbn, authors, title, pages etc as well as dvds with play time, directors, artists etc and quite a few more types. In the end, I'd have about 9 different products with a combined column count (counting common columns like title only once) of about 70 to 100 whereas each individual product has 15 columns at most. The three commonly used ways in RDBMS would be: EAV model which would have pretty bad performance characteristics and would make it either impractical or perform even worse if I'd like to display the author of a book in a list of different products (think start page, recommended products etc.). Ignore the column count and put it all in the product table: Although I deal with somewhat bigger databases (row wise), I don't have any experience with tables with more than 20 columns as far as performance is concered but I guess 100 columns would have some implications. Create a table for each product type: I personally don't like this approach as it complicates everything else. C# Driver / Classes: I'd like to use the NoRM driver and so far I think i'll try to create a product dto that contains all properties (grouped within detail classes like book details, except for those properties that should be displayed on list views etc.). In the app I'll use BookBehavior / DvdBehaviour which are wrappers around a product dto but only expose the revelent Properties. My questions now: Are my performance concerns with the many columns approach valid? Did I overlook something and there is a much better way to do it in an RDBMS? Is MongoDb on Windows stable enough? Does my approach with different behaviour wrappers make sense?

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• [F#] Parallelize code in nested loops

  - by Juliet

  You always hear that functional code is inherently easier to parallelize than non-functional code, so I decided to write a function which does the following: Given a input of strings, total up the number of unique characters for each string. So, given the input [ "aaaaa"; "bbb"; "ccccccc"; "abbbc" ], our method will returns a: 6; b: 6; c: 8. Here's what I've written: (* seq<#seq<char>> -> Map<char,int> *) let wordFrequency input = input |> Seq.fold (fun acc text -> (* This inner loop can be processed on its own thread *) text |> Seq.choose (fun char -> if Char.IsLetter char then Some(char) else None) |> Seq.fold (fun (acc : Map<_,_>) item -> match acc.TryFind(item) with | Some(count) -> acc.Add(item, count + 1) | None -> acc.Add(item, 1)) acc ) Map.empty This code is ideally parallelizable, because each string in input can be processed on its own thread. Its not as straightforward as it looks since the innerloop adds items to a Map shared between all of the inputs. I'd like the inner loop factored out into its own thread, and I don't want to use any mutable state. How would I re-write this function using an Async workflow?

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• How do I write this MySQL query?

  - by CT

  I am working on an Asset DB using a lamp stack. In this example consider the following 5 tables: asset, server, laptop, desktop, software All tables have a primary key of id, which is a unique asset id. Every object has all asset attributes and then depending on type of asset has additional attributes in the corresponding table. If the type is a server, desktop or laptop it also has items in the software table. Here are the table create statements: // connect to mysql server and database "asset_db" mysql_connect("localhost", "asset_db", "asset_db") or die(mysql_error()); mysql_select_db("asset_db") or die(mysql_error()); // create asset table mysql_query("CREATE TABLE asset( id VARCHAR(50) PRIMARY KEY, company VARCHAR(50), location VARCHAR(50), purchase_date VARCHAR(50), purchase_order VARCHAR(50), value VARCHAR(50), type VARCHAR(50), notes VARCHAR(200))") or die(mysql_error()); echo "Asset Table Created.</br />"; // create software table mysql_query("CREATE TABLE software( id VARCHAR(50) PRIMARY KEY, software VARCHAR(50), license VARCHAR(50))") or die(mysql_error()); echo "Software Table Created.</br />"; // create laptop table mysql_query("CREATE TABLE laptop( id VARCHAR(50) PRIMARY KEY, manufacturer VARCHAR(50), model VARCHAR(50), serial_number VARCHAR(50), esc VARCHAR(50), user VARCHAR(50), prev_user VARCHAR(50), warranty VARCHAR(50))") or die(mysql_error()); echo "Laptop Table Created.</br />"; // create desktop table mysql_query("CREATE TABLE desktop( id VARCHAR(50) PRIMARY KEY, manufacturer VARCHAR(50), model VARCHAR(50), serial_number VARCHAR(50), esc VARCHAR(50), user VARCHAR(50), prev_user VARCHAR(50), warranty VARCHAR(50))") or die(mysql_error()); echo "Desktop Table Created.</br />"; // create server table mysql_query("CREATE TABLE server( id VARCHAR(50) PRIMARY KEY, manufacturer VARCHAR(50), model VARCHAR(50), warranty VARCHAR(50))") or die(mysql_error()); echo "Server Table Created.</br />"; ?> How do I query the database so that if I search by id, I receive all related fields to that asset id? Thank you.

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• Improve performance of searching JSON object with jQuery

  - by cale_b

  Please forgive me if this is answered on SO somewhere already. I've searched, and it seems as though this is a fairly specific case. Here's an example of the JSON (NOTE: this is very stripped down - this is dynamically loaded, and currently there are 126 records): var layout = { "2":[{"id":"40","attribute_id":"2","option_id":null,"design_attribute_id":"4","design_option_id":"131","width":"10","height":"10", "repeat":"0","top":"0","left":"0","bottom":"0","right":"0","use_right":"0","use_bottom":"0","apply_to_options":"0"}, {"id":"41","attribute_id":"2","option_id":"115","design_attribute_id":"4","design_option_id":"131","width":"2","height":"1", "repeat":"0","top":"0","left":"0","bottom":"4","right":"2","use_right":"0","use_bottom":"0","apply_to_options":"0"}, {"id":"44","attribute_id":"2","option_id":"118","design_attribute_id":"4","design_option_id":"131","width":"10","height":"10", "repeat":"0","top":"0","left":"0","bottom":"0","right":"0","use_right":"0","use_bottom":"0","apply_to_options":"0"}], "5":[{"id":"326","attribute_id":"5","option_id":null,"design_attribute_id":"4","design_option_id":"154","width":"5","height":"5", "repeat":"0","top":"0","left":"0","bottom":"0","right":"0","use_right":"0","use_bottom":"0","apply_to_options":"0"}] }; I need to match the right combination of values. Here's the function I currently use: function drawOption(attid, optid) { var attlayout = layout[attid]; $.each(attlayout, function(k, v) { // d_opt_id and d_opt_id are global scoped variable set elsewhere if (v.design_attribute_id == d_att_id && v.design_option_id == d_opt_id && v.attribute_id == attid && ((v.apply_to_options == 1 || (v.option_id === optid)))) { // Do stuff here } }); } The issue is that I might iterate through 10-15 layouts (unique attid's), and any given layout (attid) might have as many as 50 possibilities, which means that this loop is being run A LOT. Given the multiple criteria that have to be matched, would an AJAX call work better? (This JSON is dynamically created via PHP, so I could craft a PHP function that could possibly do this more efficently), or am I completely missing something about how to find items in a JSON object? As always, any suggestions for improving the code are welcome! EDIT: I apologize for not making this clear, but the purpose of this question is to find a way to improve the performance. The page has a lot of javascript, and this is a location where I know that performance is lower than it could be.

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• HTML file: add annotations through IHTMLDocument

  - by peterchen

  I need to add "annotations" to existing HTML documents - best in the form of string property values I can read & write by name. Apparently (to me), meta elements in the header seem to be the common way - i.e. adding/modifying elements like <head> <meta name="unique-id_property-name" content="property-value"/> ... </head> Question 1: Ist that "acceptable" / ok, or is there a better way to add meta data? I have a little previous experience with getting/mut(il)ating HTML contents through the document in an web browser control. For this task, I've already loaded the HTML document into a HTMLDocument object, but I'm not sure how to go on: // what I have IHTMLDocument2Ptr doc; doc.CreateInstance(__uuidof(HTMLDocument)); IPersistFile pf = doc; pf->Load(fileName, STGM_READ); // everything ok until here Questions 2: Should I be using anything else than HTMLDocument? Questions 3..N: How do I get the head element? How do I get the value of a meta element with a given name? How do I set the value of a meta element (adding the item if and only if it doesn't exist yet)? doc->all returns a collection of all tags, which I can enumerate even though count returns 0. I could scan that for head, then scan that for all meta where the name starts with a certain string, etc. - but this feels very clumsy.

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• Get table row based on radio button using prototype/javascript

  - by David Buckley

  I have an html table that has a name and a radio button like so: <table id="cars"> <thead> <tr> <th>Car Name</th> <th></th> </tr> </thead> <tbody> <tr> <td class="car">Ford Focus</td> <td><input type="radio" id="selectedCar" name="selectedCar" value="8398"></td> </tr> <tr> <td class="car">Lincoln Navigator</td> <td><input type="radio" id="selectedCar" name="selectedCar" value="2994"></td> </tr> </tbody> </table> <input type="button" value="Select Car" onclick="selectCar()"></input> I want to be able to select a radio button, then click another button and get the value of the radio button (which is a unique ID) as well as the car name text (like Ford Focus). How should I code the selectCar method? I've tried a few things like: val1 = $('tr input[name=selectedCar]:checked').parent().find('#cars').html(); val1 = $("td input[name='selectedCar']:checked").parents().find('.cars').html(); val1 = $('selectedCar').checked; but I can't get the proper values. I'm using prototype, but the solution can be plain javascript as well.

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• URL shortening: using inode as short name?

  - by Licky Lindsay

  The site I am working on wants to generate its own shortened URLs rather than rely on a third party like tinyurl or bit.ly. Obviously I could keep a running count new URLs as they are added to the site and use that to generate the short URLs. But I am trying to avoid that if possible since it seems like a lot of work just to make this one thing work. As the things that need short URLs are all real physical files on the webserver my current solution is to use their inode numbers as those are already generated for me ready to use and guaranteed to be unique. function short_name($file) { $ino = @fileinode($file); $s = base_convert($ino, 10, 36); return $s; } This seems to work. Question is, what can I do to make the short URL even shorter? On the system where this is being used, the inodes for newly added files are in a range that makes the function above return a string 7 characters long. Can I safely throw away some (half?) of the bits of the inode? And if so, should it be the high bits or the low bits? I thought of using the crc32 of the filename, but that actually makes my short names longer than using the inode. Would something like this have any risk of collisions? I've been able to get down to single digits by picking the right value of "$referencefile". function short_name($file) { $ino = @fileinode($file); // arbitrarily selected pre-existing file, // as all newer files will have higher inodes $ino = $ino - @fileinode($referencefile); $s = base_convert($ino, 10, 36); return $s; }

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• How to create a "Shell IDList Array" to support drag-and-drop of virtual files from C# to Windows Ex

  - by JustABill

  I started trying to implement drag-and-drop of virtual files (from a C# 4/WPF app) with this codeplex tutorial. After spending some time trying to figure out a DV_E_FORMATETC error, I figured out I need to support the "Shell IDList Array" data format. But there seems to be next to zero documentation on what this format actually does. After some searching, I found this page on advanced data transfer which said that a Shell IDList Array was a pointer to a CIDA structure. This CIDA structure then contains the number of PIDLs, and a list of offsets to them. So what the hell is a PIDL? After some more searching, this page sort of implies it's a pointer to an ITEMIDLIST, which itself contains a single member that is a list of SHITEMIDs. My next idea was to try dragging a file from another application with virtual files. I just got a MemoryStream back for this format. At least I know what class to provide for the thing, but that doesn't help at all for explaining what to put in it. So now that that's explained, I still have no idea how to create one of these things so that it's valid. There's two real questions here: What is a valid "abID" member for a SHITEMID? These virtual files only exist with my program; will the thing they are dragged to pass the "abID" back later when it executes GetData? Do they have to be system-unique? Why are there two levels of lists; a list of PIDLs and each PIDL has a list of SHITEMIDs? I'm assuming one of them is one for each file, but what's the other one for? Multiple IDs for the same file? Any help or even links that explain what I should be doing would be greatly appreciated.

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• Substrings, timer and LED lights, as3

  - by VideoDnd

  How would I sync my timer with my LED lights? I don't understand how to to set up the strings and conditions, so that they are unique to each number space. Need a condition and values for each blinker var condition:Number = 5; if(condition==5){ blink.visible = !blink.visible; //blink_.visible = !box.visible; //blink__.visible = !box.visible; } } Complete code //MY TIMER var timer:Timer = new Timer(100); //INTEGER VALUES var count:int = 0; var fcount:int = 0; var oldcount:int = 0; //FORMATTING STRING function formatCount(i:int):String { var fraction:int = i % 100; var whole:int = i / 100; return ("00" + whole).substr(-2, 2) + "." + (fraction < 10 ? "0" + fraction : fraction); } //START TIMER timer.start(); timer.addEventListener(TimerEvent.TIMER, condition); //ANIMATION function condition(event:TimerEvent):void{ count++; fcount=int(count) var toText:String = formatCount(fcount); dec.text = toText.substr(4, 1); decimal.text = toText.substr(3, 1); ones.text = toText.substr(1, 1); //LED LIGHTS var condition:Number = 5; if(condition==5){ blink.visible = !blink.visible; //blink_.visible = !box.visible; //blink__.visible = !box.visible; } }

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• Modularizing web applications

  - by Matt

  Hey all, I was wondering how big companies tend to modularize components on their page. Facebook is a good example: There's a team working on Search that has its own CSS, javascript, html, etc.. There's a team working on the news feed that has its own CSS, javascript, html, etc... ... And the list goes on They cannot all be aware of what everyone is naming their div tags and whatnot, so what's the controller(?) doing to hook all these components in on the final page?? Note: This doesn't just apply to facebook - any company that has separate teams working on separate components has some logic that helps them out. EDIT: Thanks all for the responses, unfortunately I still haven't really found what I'm looking for - when you check out the source code (granted its minified), the divs have UIDs, my guess is that there is a compilation process that runs through and makes each of the components unique, renaming divs and css rules.. any ideas? EDIT 2: Thanks all for contributing your thoughts - the bounty went to the highest upvoted answer. The question was designed to be vague- I think it led to a really interesting discussion. As I improve my build process, I will contribute my own thoughts and experiences. Thanks all! Matt Mueller

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• use awk to identify multi-line record and filtering

  - by nanshi

  I need to process a big data file that contains multi-line records, example input: 1 Name Dan 1 Title Professor 1 Address aaa street 1 City xxx city 1 State yyy 1 Phone 123-456-7890 2 Name Luke 2 Title Professor 2 Address bbb street 2 City xxx city 3 Name Tom 3 Title Associate Professor 3 Like Golf 4 Name 4 Title Trainer 4 Likes Running Note that the first integer field is unique and really identifies a whole record. So in the above input I really have 4 records although I dont know how many lines of attributes each records may have. I need to: - identify valid record (must have "Name" and "Title" field) - output the available attributes for each valid record, say "Name", "Title", "Address" are needed fields. Example output: 1 Name Dan 1 Title Professor 1 Address aaa street 2 Name Luke 2 Title Professor 2 Address bbb street 3 Name Tom 3 Title Associate Professor So in the output file, record 4 is removed since it doen't have the "Name" field. Record 3 doesn't have Address field but still being print to the output since it is a valid record that has "Name" and "Title". Can I do this with awk? But how do i identify a whole record using the first "id" field on each line? Thanks a lot to the unix shell script expert for helping me out! :)

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• Ordering by a max or a min from another table

  - by Paul Tomblin

  I have a table that consists of a unique id, and a few other attributes. It holds "schedules". Then I have another table that holds a list of all the times each schedule has or will "fire". This isn't the exact schema, but it's close: create table schedule ( id varchar(40) primary key, attr1 int, attr2 varchar(20) ); create table schedule_times ( id varchar(40) foreign key schedule(id), fire_date date ); I want to query the schedule table, getting the attributes and the next and previous fire_dates, in Java, sometimes ordering on one of the attributes, but sometimes ordering on either previous fire_date or the next fire_date. Ordering by the attributes is easy, I just stick an "order by" into the string while I'm building my prepared statement. I'm not even sure how to go about selecting the last fire_date and the next one in a single query - I know that I can find the next fire_date for a given id by doing a SELECT min(fire_date) FROM schedule_times WHERE id = ? AND fire_date > sysdate; and the similar thing for previous fire_date using max() and fire_date < sysdate. I'm just drawing a blank on how to incorporate that into a single select from the schedule so I can get both next and previous fire_date in one shot, and also how to order by either of those attributes.

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• Auto filling polymorphic table on save or on delete in django

  - by Mo J. Mughrabi

  Hi, Am working on an project in which I made an app "core" it will contain some of the reused models across my projects, most of those are polymorphic models (Generic content types) and will be linked to different models. Example below am trying to create audit model and will be linked to several models which may require auditing. This is the polls/models.py from django.db import models from django.contrib.auth.models import User from core.models import * from django.contrib.contenttypes import generic class Poll(models.Model): ## TODO: Document question = models.CharField(max_length=300) question_slug=models.SlugField(editable=False) start_poll_at = models.DateTimeField(null=True) end_poll_at = models.DateTimeField(null=True) is_active = models.BooleanField(default=True) audit_obj=generic.GenericRelation(Audit) def __unicode__(self): return self.question class Choice(models.Model): ## TODO: Document choice = models.CharField(max_length=200) poll=models.ForeignKey(Poll) audit_obj=generic.GenericRelation(Audit) class Vote(models.Model): ## TODO: Document choice=models.ForeignKey(Choice) Ip_Address=models.IPAddressField(editable=False) vote_at=models.DateTimeField("Vote at", editable=False) here is the core/modes.py from django.db import models from django.contrib.auth.models import User from django.contrib.contenttypes.models import ContentType from django.contrib.contenttypes import generic class Audit(models.Model): ## TODO: Document # Polymorphic model using generic relation through DJANGO content type created_at = models.DateTimeField("Created at", auto_now_add=True) created_by = models.ForeignKey(User, db_column="created_by", related_name="%(app_label)s_%(class)s_y+") updated_at = models.DateTimeField("Updated at", auto_now=True) updated_by = models.ForeignKey(User, db_column="updated_by", null=True, blank=True, related_name="%(app_label)s_%(class)s_y+") content_type = models.ForeignKey(ContentType) object_id = models.PositiveIntegerField(unique=True) content_object = generic.GenericForeignKey('content_type', 'object_id') and here is polls/admin.py from django.core.context_processors import request from polls.models import Poll, Choice from core.models import * from django.contrib import admin class ChoiceInline(admin.StackedInline): model = Choice extra = 3 class PollAdmin(admin.ModelAdmin): inlines = [ChoiceInline] admin.site.register(Poll, PollAdmin) Am quite new to django, what am trying to do here, insert a record in audit when a record is inserted in polls and then update that same record when a record is updated in polls.

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• Help with Hashmaps in Java

  - by Crystal

  I'm not sure how I use get() to get my information. Looking at my book, they pass the key to get(). I thought that get() returns the object associated with that key looking at the documentation. But I must be doing something wrong here.... Any thoughts? import java.util.*; public class OrganizeThis { /** Add a person to the organizer @param p A person object */ public void add(Person p) { staff.put(p, p.getEmail()); System.out.println("Person " + p + "added"); } /** * Find the person stored in the organizer with the email address. * Note, each person will have a unique email address. * * @param email The person email address you are looking for. * */ public Person findByEmail(String email) { Person aPerson = staff.get(email); return aPerson; } private Map<Person, String> staff = new HashMap<Person, String>(); public static void main(String[] args) { OrganizeThis testObj = new OrganizeThis(); Person person1 = new Person("J", "W", "111-222-3333", "[email protected]"); testObj.add(person1); System.out.println(testObj.findByEmail("[email protected]")); } }

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• Using JQuery to traverse DOM structure, finding a specific <table> element located after HTML 'comme

  - by Shadow

  I currently have a website source code (no control over the source) which contains certain content that needs to be manipulated. This would be simple on the surface, however there is no unique ID attribute on the tag in question that can uniquely identify it, and therefore allow for further traversal. Here is a snippet of the source code, surrounding the tag in question. ... <td width="100%"> <!--This table snaps the content columns(one or two)--> <table border="0" width="100%"> ... Essentially, the HTML comment stuck out as an easy way to gain access to that element. Using the JQuery comment add-on from this question, and some help from snowlord comment below, I have been able to identify the comment and retrieve the following output using the 'dump' extension. $('td').comments().filter(":contains('This table snaps the content columns(one or two)')").dump(); returns; jQuery Object { 0 = DOMElement [ nodeName: DIV nodeValue: null innerHTML: [ 0 = String: This table snaps the content columns(one or two) ] ] } However I am not sure how to traverse to the sibling element in the DOM. This should be simple, but I haven't had much selector experience with JQuery. Any suggestions are appreciated.

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• Trying to generate all sequences of specified numbers up to a max sum

  - by Stecy

  Hi, Given the following list of descending unique numbers (3,2,1) I wish to generate all the sequences consisting of those numbers up to a maximum sum. Let's say that the sum should be below 10. Then the sequences I'm after are: 3 3 3 3 3 2 1 3 3 2 3 3 1 1 1 3 3 1 1 3 3 1 3 3 3 2 2 2 3 2 2 1 1 3 2 2 1 3 2 2 3 2 1 1 1 1 3 2 1 1 1 3 2 1 1 3 2 1 3 2 3 1 1 1 1 1 1 3 1 1 1 1 1 3 1 1 1 1 3 1 1 1 3 1 1 3 1 3 2 2 2 2 1 2 2 2 2 2 2 2 1 1 1 2 2 2 1 1 2 2 2 1 2 2 2 2 2 1 1 1 1 1 2 2 1 1 1 1 2 2 1 1 1 2 2 1 1 2 2 1 2 2 2 1 1 1 1 1 1 1 2 1 1 1 1 1 1 2 1 1 1 1 1 2 1 1 1 1 2 1 1 1 2 1 1 2 1 2 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 I'm sure that there's a "standard" way to generate this. I thought of using linq but can't figure it out. Also, I am trying a stack based approach but I am still not successful. Any idea?

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• jQuery - select onchange to slide in / slide out div or form

  - by slayaz

  Hi, I am trying to enhance a form, by showing only relevant fields depending on initial selection via a form select field. It is an order form for 3 products and all 3 products have unique properties. My idea was to hide all the content in divs, then reveal the relevant div when the product is selected. I have found some solutions that show / hide a div, but none with any animation. It doesn't have to be a slide but just something nice! The alternative is instead of revealing a div, would be to load a seperate form, but this seems unnecessary. I am not sure whether i need a plug in, as I am pretty new to jquery. What i have in the html is: <style type="text/css"> .hide { display:none; } <select> <option value="" >Please select product below</option> <option value="pro1">Product 1</option> <option value="pro2">Product 2</option> </select> <div id="pro1" class="hide" >Product 1</div> <div id="pro2" class="hide" >Product 2</div> Many thanks in advance

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• Problem with Active Record

  - by kshchepelin

  Hello everyone. Lets assume we have a User model. And user can plan some activities. The number of types of activities is about 50. All activities have common properties, such as start_time, end_time, user_id, etc. But each of them has some unique properties. Now we have each activity living in its own table in DB. And thats why we have such terrible sql queries like SELECT * FROM `first_activities_table` WHERE (`first_activity`.`id` IN (17,18)) SELECT * FROM `second_activities_table` WHERE (`second_activity`.`id` = 17) ..... SELECT * FROM `n_activities_table` WHERE (`n_activity`.`id` = 44) About 50 queries. That's terrible. There are different ways to solve this. Choose the activity type with the biggest number of properties, create the table 'Activities' and have STI model. But this way we must name our columns in uncomfortable way and often the record in that table would have some NULL fields. Also STI model, but having columns, common for all of activity types and some blob column with serialized properties. But we have to do some search on activities - there can be a problem. And serialization is quite slow. Please help me dealing with this. Maybe my problem has quite different solution that will fit my needs. Thanks for help.

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• Dynamically setting the queryset of a ModelMultipleChoiceField to a custom recordset

  - by Daniel Quinn

  I've seen all the howtos about how you can set a ModelMultipleChoiceField to use a custom queryset and I've tried them and they work. However, they all use the same paradigm: the queryset is just a filtered list of the same objects. In my case, I'm trying to get the admin to draw a multiselect form that instead of using usernames as the text portion of the , I'd like to use the name field from my account class. Here's a breakdown of what I've got: # models.py class Account(models.Model): name = models.CharField(max_length=128,help_text="A display name that people understand") user = models.ForeignKey(User, unique=True) # Tied to the User class in settings.py class Organisation(models.Model): administrators = models.ManyToManyField(User) # admin.py from django.forms import ModelMultipleChoiceField from django.contrib.auth.models import User class OrganisationAdminForm(forms.ModelForm): def __init__(self, *args, **kwargs): from ethico.accounts.models import Account self.base_fields["administrators"] = ModelMultipleChoiceField( queryset=User.objects.all(), required=False ) super(OrganisationAdminForm, self).__init__(*args, **kwargs) class Meta: model = Organisation This works, however, I want queryset above to draw a selectbox with the Account.name property and the User.id property. This didn't work: queryset=Account.objects.all().order_by("name").values_list("user","name") It failed with this error: 'tuple' object has no attribute 'pk' I figured that this would be easy, but it's turned into hours of dead-ends. Anyone care to shed some light?

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• Conversion failed when converting the varchar value to int

  - by onedaywhen

  Microsoft SQL Server 2008 (SP1), getting an unexpected 'Conversion failed' error. Not quite sure how to describe this problem, so below is a simple example. The CTE extracts the numeric portion of certain IDs using a search condition to ensure a numeric portion actually exists. The CTE is then used to find the lowest unused sequence number (kind of): CREATE TABLE IDs (ID CHAR(3) NOT NULL UNIQUE); INSERT INTO IDs (ID) VALUES ('A01'), ('A02'), ('A04'), ('ERR'); WITH ValidIDs (ID, seq) AS ( SELECT ID, CAST(RIGHT(ID, 2) AS INTEGER) FROM IDs WHERE ID LIKE 'A[0-9][0-9]' ) SELECT MIN(V1.seq) + 1 AS next_seq FROM ValidIDs AS V1 WHERE NOT EXISTS ( SELECT * FROM ValidIDs AS V2 WHERE V2.seq = V1.seq + 1 ); The error is, 'Conversion failed when converting the varchar value 'RR' to data type int.' I can't understand why the value ID = 'ERR' should be being considered for conversion because the predicate ID LIKE 'A[0-9][0-9]' should have removed the invalid row from the resultset. When the base table is substituted with an equivalent CTE the problem goes away i.e. WITH IDs (ID) AS ( SELECT 'A01' UNION ALL SELECT 'A02' UNION ALL SELECT 'A04' UNION ALL SELECT 'ERR' ), ValidIDs (ID, seq) AS ( SELECT ID, CAST(RIGHT(ID, 2) AS INTEGER) FROM IDs WHERE ID LIKE 'A[0-9][0-9]' ) SELECT MIN(V1.seq) + 1 AS next_seq FROM ValidIDs AS V1 WHERE NOT EXISTS ( SELECT * FROM ValidIDs AS V2 WHERE V2.seq = V1.seq + 1 ); Why would a base table cause this error? Is this a known issue? UPDATE @sgmoore: no, doing the filtering in one CTE and the casting in another CTE still results in the same error e.g. WITH FilteredIDs (ID) AS ( SELECT ID FROM IDs WHERE ID LIKE 'A[0-9][0-9]' ), ValidIDs (ID, seq) AS ( SELECT ID, CAST(RIGHT(ID, 2) AS INTEGER) FROM FilteredIDs ) SELECT MIN(V1.seq) + 1 AS next_seq FROM ValidIDs AS V1 WHERE NOT EXISTS ( SELECT * FROM ValidIDs AS V2 WHERE V2.seq = V1.seq + 1 );

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• Database design MySQL using foreign keys

  - by dscher

  I'm having some a little trouble understanding how to handle the database end of a program I'm making. I'm using an ORM in Kohana, but am hoping that a generalized understanding of how to solve this issue will lead me to an answer with the ORM. I'm writing a program for users to manage their stock research information. My tables are basically like so: CREATE TABLE tags( id INT AUTO_INCREMENT NOT NULL PRIMARY KEY, tags VARCHAR(30), UNIQUE(tags) ) ENGINE=INNODB DEFAULT CHARSET=utf8; CREATE TABLE stock_tags( id INT AUTO_INCREMENT NOT NULL PRIMARY KEY, tag_id INT NOT NULL, stock_id INT NOT NULL, FOREIGN KEY (tag_id) REFERENCES tags(id), FOREIGN KEY(stock_id) REFERENCES stocks(id) ON DELETE CASCADE ) ENGINE=INNODB DEFAULT CHARSET=utf8; CREATE TABLE notes( id INT AUTO_INCREMENT NOT NULL, stock_id INT NOT NULL, notes TEXT NOT NULL, FOREIGN KEY (stock_id) REFERENCES stocks(id) ON DELETE CASCADE, PRIMARY KEY(id) ) ENGINE=INNODB DEFAULT CHARSET=utf8; CREATE TABLE links( id INT AUTO_INCREMENT NOT NULL, stock_id INT NOT NULL, links VARCHAR(2083) NOT NULL, FOREIGN KEY (stock_id) REFERENCES stocks(id) ON DELETE CASCADE, PRIMARY KEY(id) ) ENGINE=INNODB DEFAULT CHARSET=utf8; How would I get all the attributes of a single stock, including its links, notes, and tags? Do I have to add links, notes, and tags columns to the stocks table and then how do you call it? I know this differs using an ORM and I'd assume that I can use join tables in SQL. Thanks for any help, this will really help me understand the issue a lot better.

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• Fast, easy, and secure method to perform DB actions with GET

  - by rob - not a robber

  Hey All, Sort of a methods/best practices question here that I am sure has been addressed, yet I can't find a solution based on the vague search terms I enter. I know starting off the question with "Fast and easy" will probably draw out a few sighs, so my apologies. Here is the deal. I have a logged in area where an ADMIN can do a whole host of POST operations to input data relating to their profile. The way I have data structured is pretty distinct and well segmented in most tables as it relates to the ID of the admin. Now, I have a table where I dump one type of data into and differentiate this data by assigning the ADMIN's unique ID to each record. In other words, all ADMINs have this one type of data writing to this table. I just differentiate by the ADMIN ID with each record. I was planning on letting the ADMIN remove these records by clicking on a link with a query string - obviously using GET. Obviously, the query structure is in the link so any logged in admin could then exploit the URL and delete a competitor's records. Is the only way to safely do this through POST or should I pass through the session info that includes password and validate it against the ADMIN ID that is requesting the delete? This is obviously much more work for me. As they said in the auto repair biz I used to work in... there are 3 ways to do a job: Fast, Good, and Cheap. You can only have two at a time. Fast and cheap will not be good. Good and cheap will not have fast turnaround. Fast and good will NOT be cheap. haha I guess that applies here... can never have Fast, Easy and Secure all at once ;) Thanks in advance...

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• Which parts of the client certificate to use when uniquely identifying users?

  - by miha

  I'm designing a system where users will be able to register and afterward authenticate with client certificates in addition to username/password authentication. The client certificates will have to be valid certificates issued by a configured list of certificate authorities and will be checked (validated) when presented. In the registration phase, I need to store part(s) of the client certificate in a user repository (DB, LDAP, whatever) so that I can map the user who authenticates with client certificate to an internal "user". One fairly obvious choice would be to use certificate fingerprint; But fingerprint itself is not enough, since collisions may occur (even though they're not probable), so we need to store additional information from the certificate. This SO question is also informative in this regard. RFC 2459 defines (4.1.2.2) that certificate serial number must be unique within a given CA. With all of this combined, I'm thinking of storing certificate serial number and certificate issuer for each registered user. Given that client certificates will be verified and valid, this should uniquely identify each client certificate. That way, even when client certificate is renewed, it would still be valid (serial number stays the same, and so does the issuer). Did I miss something?

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• PHP Form Validation

  - by JM4

  This question will undoubtedly be difficult to answer and ask in a way that makes sense but I'll try my best: I have a form which uses PHP to display certain sections of the form such as: <?php if ($_SESSION['EnrType'] == "Individual") { display only form information for individual enrollment } ?> and <?php if ($_SESSION['Num_Enrs'] > 6) { display only form information for 7 total members enrollment } ?> In each form piece, unique information is collected about each enrollee but the basic criteria for each enrollee is the same, i.e. All enrollee's must use have a value in the FirstName field. Each field is named according to the enrollee number, i.e. Num1FirstName; Num2FirstName. I have a PHP validation script which is absolutely fantastic and am not looking to change it but the issue I am running into is duplication of the script in order to validate ALL fields in one swoop. On submission, all POSTED items are run through my validation script and based on the rules set return an error if they do not equal true. Sample code: if (isset($_POST['submit'])) { // import the validation library require("validation.php"); $rules = array(); // stores the validation rules //All Enrollee Rules $rules[] = "required,Num1FirstName,Num2FirstName,The First Name field is required."; The script above does the following, $rules[] ="REQUIREMENT,fieldname,error message" where requirement gives criteria (in this case, simply that a value is passed), fieldname is the name of the field being validated, and error message returns the error used. My Goal is to use the same formula above and have $rules[] run through ALL firstnames and return the error posted ONLY if they exist (i.e. dont check for member #7's first name if it doesnt exist on the screen). If I simply put a comma between the 'fieldnames' this only checks for the first, then second, and so on so this wont work. Any ideas?

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