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• Databases design - one link table or multiple link tables?

  - by David

  Hi there, I'm working on a front end for a database where each table essentially has a many to many relationship with all other tables. I'm not a DB admin, just a few basic DB courses. The typical solution in this case, as I understand it, would be multiple link tables to join each 'real' table. Here's what I'm proposing instead: one link table that has foreign key dependencies to all other PKs of the other tables. Is there any reason this could turn out badly in terms of scalability, flexibility, etc down the road?

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• How to determine OS Platform with WMI?

  - by cary.wagner

  I am trying to figure out if there is a location in WMI that will return the OS Architecture (i.e. 32-bit or 64-bit) that will work across "all" versions of Windows. I thought I had figured it out looking at my Win2k8 system when I found the following: Win32_OperatingSystem / OSArchitecture I was wrong. It doesn't appear that this field exists on Win2k3 systems. Argh! So, is anyone aware of another field in WMI that "is" the same across server versions? If not, what about a registry key that is the same? I am using a tool that only allows me to configure simple field queries, so I cannot use a complex script to perform. Any help would be greatly appreciated! Cheers... Cary

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• Django save, column specified twice

  - by realshadow

  Hey, I would like to save a modified model, but I get Programming error - that a field is specified twice. class ProductInfo(models.Model): product_info_id = models.AutoField(primary_key=True) language_id = models.IntegerField() product_id = models.IntegerField() description = models.TextField(blank=True) status = models.IntegerField() model = models.CharField(max_length=255, blank=True) label = models.ForeignKey(Category_info, verbose_name = 'Category_info', db_column = 'language_id', to_field = 'node_id', null = True) I get this error because the foreign key uses as db_column language_id. If I will delete it, my object will be saved properly. I dont quite understand whats going on and since I have defined almost all of my models this way, I fear its totally wrong or maybe I just missunderstood it... Any ideas? Regards

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• What stage of normalization is this? (moving repeating data into separate table)

  - by Sergio

  Hi There, I have noticed that when designing a database I tend to shift any repeating sets of data into a separate table. For example, say I had a table of people, with each person living in a state. I would then move these repeating states into a separate table and reference them with foreign keys. However, what if I was not storing any more data about states. I would then have a table with StateID and State in. Is this action correct? State is dependant on the primary key of the users table, so does shifting it into its own table help with anything? Thanks,

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• php, mySQL - how to create a table?

  - by user296516

  Hi guys, I have written a code that should check weather there is a table called imei.$addimei and, if not, create it... $userdatabase = mysqli_connect('localhost', 'root', 'marina', 'imei'); ... $result = mysqli_query($userdatabase, "SELECT * FROM imei".$addimei."" ); if ( !$result ) { echo('creating table...'); /// if no such table, make one! mysql_query ( $userdatabase, 'CREATE TABLE imei'.$addimei.'( ID int NOT NULL AUTO_INCREMENT, PRIMARY KEY(ID), EVENT varchar(15), TIME varchar(25), FLD1 varchar(35), FLD2 varchar(35), IP varchar(25), )' ); } Yet the CREATE TABLE somehow doesn't seem to work. Warning: mysql_query() expects parameter 1 to be string, object given in C:\xampp\xampp\htdocs\mobi\mainmenu.php on line 564 Any idea's what wrong? Thanks!

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• Using Python's ConfigParser to read a file without section name

  - by Arrieta

  Hello: I am using ConfigParser to read the runtime configuration of a script. I would like to have the flexibility of not providing a section name (there are scripts which are simple enough; they don't need a 'section'). ConfigParser will throw the NoSectionError exception, and will not accept the file. How can I make ConfigParser simply retrieve the (key, value) tuples of a config file without section names? For instance: key1=val1 key2:val2 I would rather not write to the config file.

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• What's the best way to count unique visitors with Hadoop?

  - by beagleguy

  hey all, just getting started on hadoop and curious what the best way in mapreduce would be to count unique visitors if your logfiles looked like this... DATE siteID action username 05-05-2010 siteA pageview jim 05-05-2010 siteB pageview tom 05-05-2010 siteA pageview jim 05-05-2010 siteB pageview bob 05-05-2010 siteA pageview mike and for each site you wanted to find out the unique visitors for each site? I was thinking the mapper would emit siteID \t username and the reducer would keep a set() of the unique usersnames per key and then emit the length of that set. However that would be potentially storing millions of usernames in memory which doesn't seem right. Anyone have a better way? I'm using python streaming by the way thanks

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• LRU caches in C

  - by lazyconfabulator

  I need to cache a large (but variable) number of smallish (1 kilobyte to 10 megabytes) files in memory, for a C application (in a *nix environment). Since I don't want to eat all my memory, I'd like to set hard memory limit (say, 64 megabytes) and push files into a hash table with the file name as the key and dispose of the entries with the least use. What I believe I need is an LRU cache. Really, I'd rather not roll my own so if someone knows where I can find a workable library, please point the way? Failing that, can someone provide a simple example of an LRU cache in C? Related posts indicated that a hash table with a doubly-linked list, but I'm not even clear on how a doubly-linked list keeps LRU. Side note: I realize this is almost exactly the function of memcache, but it's not an option for me. I also took a look at the source hoping to enlighten myself on LRU caching, with no success.

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• How do I find hash value of a 3D vector ?

  - by brainydexter

  I am trying to perform broad-phase collision detection with a fixed-grid size approach. Thus, for each entity's position: (x,y,z) (each of type float), I need to find which cell does the entity lie in. I then intend to store all the cells in a hash-table and then iterate through to report (if any) collisions. So, here is what I am doing: Grid-cell's position: (int type) (Gx, Gy, Gz) = (x / M, y / M, z / M) where M is the size of the grid. Once, I have a cell, I'd like to add it to a hash-table with its key being a unique hash based on (Gx, Gy, Gz) and the value being the cell itself. Now, I cannot think of a good hash function and I need some help with that. Can someone please suggest me a good hash function? Thanks

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• Storing member function pointers of derived classes in map

  - by Kiran Mohan

  Hello, I am trying to implement a factory for two classes Circle, Square both of which inherits from Shape. class Shape { public: virtual static Shape * getInstance() = 0; }; class Circle : public Shape { public: static const std::string type; Shape * getInstance() { return new Circle; } }; const std::string Circle::type = "Circle"; class Square : public Shape { public: static const std::string type; Shape * getInstance() { return new Square; } }; const std::string Square::type = "Square"; I want to now create a map with key as shape type (string) and value as a function pointer to getInstance() of the corresponding derived class. Is it possible? Thanks, Kiran

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• Lose changed data in session

  - by user150528

  Our asp.net 2.0 application has a very long process (synchronized) before sending response back to client. I observed that a second request, exactly same the initial one, was sent after client IE8 waited response for a long period of time while our application was still processing the first request. I use page session with predefined key to store a flag when the initial request arrives and then starts long process while client IE waits for the response, so if second request comes in, our application checks the session value. After our application sets the session flag and starts processing, I use Fiddler “Abort Session” to abort the initial request, right away the second request (same as the first one) is sent automatically, but session value set earlier seems no longer exist. Any thoughts?

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• Database Modeling - Either/Or in Many-to-Many

  - by EkoostikMartin

  I have an either/or type of situation in a many-to-many relationship I'm trying to model. So I have these tables: Message ---- *MessageID MessageText Employee ---- *EmployeeID EmployeeName Team ---- *TeamID TeamName MessageTarget ---- MessageID EmployeeID (nullable) TeamID (nullable) So, a Message can have either a list of Employees, or a list of Teams as a MessageTarget. Is the MessageTarget table I have above the best way to implement this relationship? What constraints can I place on the MessageTarget effectively? How should I create a primary key on MessageTarget table?

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• Assigning the Tag Property of a Control in WPF

  - by jmayor

  If I have 7 checkBoxes, one for each day of the week, Can I assing in XAML the Tag property to each one of the the System.DayOfWeek enumeration value? <StackPanel > <StackPanel.Resources> <system:DayOfWeek x:Key="Monday" >Monday</system:DayOfWeek> </StackPanel.Resources> <CheckBox Name="chkMo" Tag="{StaticResource Monday}">Mo</CheckBox> ... </StackPanel> Is there a way to assign directly the enum value to the tag without using resources?

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• Rabbitmq queue sharding

  - by kolchanov

  I have to implement this scenario: An external application publish message to rabbitmq. This message has a client_id property. We can place this id to routing key or message header or some other property. I have to implement sharding in a exchange routng logic - the message should be delivered to specific queue based on the client_id range. Is it possible to implement in a standard exchanges? If not what exchange should I take as the base? How to dynamicly change client_id ranges?

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• Sort by an object's type

  - by Richard Levasseur

  Hi all, I have code that statically registers (type, handler_function) pairs at module load time, resulting in a dict like this: HANDLERS = { str: HandleStr, int: HandleInt, ParentClass: HandleCustomParent, ChildClass: HandleCustomChild } def HandleObject(obj): for data_type in sorted(HANDLERS.keys(), ???): if isinstance(obj, data_type): HANDLERS[data_type](obj) Where ChildClass inherits from ParentClass. The problem is that, since its a dict, the order isn't defined - but how do I introspect type objects to figure out a sort key? The resulting order should be child classes follow by super classes (most specific types first). E.g. str comes before basestring, and ChildClass comes before ParentClass. If types are unrelated, it doesn't matter where they go relative to each other.

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• Converting HTML special characters into their value using Python

  - by tipu

  I have a file that's littered with these: http://www.utexas.edu/learn/html/spchar.html That link just displays all sorts of HTML entities, such as – &ndash; — &mdash; ¡ &iexcl; and so on. Is it possible in Python to natively convert these characters back into their values so any occurrences of &ndash; will appear as – instead? My current approach was just to make a dict of key html entities and their utf-8 values and do search and replace, but I was wondering if there are any libraries that can take care of this for me.

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• Web.config encryption/decryption

  - by Akshay

  In my applications we.config file I have a connection string stored. I encrypted it using '---open the web.config file Dim config As Configuration = _ ConfigurationManager.OpenWebConfiguration( _ Request.ApplicationPath) '---indicate the section to protect Dim section As ConfigurationSection = _ config.Sections("connectionStrings") '---specify the protection provider section.SectionInformation.ProtectSection(protectionProvider) '---Apple the protection and update config.Save() Now I can decrypt it using the code Dim config As Configuration = _ ConfigurationManager.OpenWebConfiguration( _ Request.ApplicationPath) Dim section As ConfigurationSection = _ config.Sections("connectionStrings") section.SectionInformation.UnProtectSection() config.Save() I want to know where is the key stored. Also If somehow my web.config file is stolen, will it be possible for him/her to decrypt it using thhe code above.

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• Access event.target in IE8 unobstrusive Javascript

  - by Mirko

  The following function gets the target element in a dropdown menu: function getTarget(evt){ var targetElement = null; //if it is a standard browser if (typeof evt.target != 'undefined'){ targetElement = evt.target; } //otherwise it is IE then adapt syntax else{ targetElement = evt.srcElement; } //return id of element when hovering over or if (targetElement.nodeName.toLowerCase() == 'li'){ return targetElement; } else if (targetElement.parentNode.nodeName.toLowerCase() == 'li'){ return targetElement.parentNode; } else{ return targetElement; } Needless to say, it works in Firefox, Chrome, Safari and Opera but it does not in IE8 (and I guess in previous versions as well). When I try to debug it with IE8 I get the error "Member not Found" on the line: targetElement = evt.srcElement; along with other subsequent errors, but I think this is the key line. Any help will be appreciated.

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• Help needed with MySQL query to join data spanning multiple tables with data used as column names

  - by gurun8

  I need a little help putting together a SQL query that will give me the following resultsets: and The data model looks like this: The tricky part for me is that the columns to the right of the "Product" in the resultset aren't really columns in the database but rather key/value pairs spanned across the data model. Table data is as follows: My apologies in advance for the image heavy question and the image quality. This just seemed like the easiest way to convey the information. It'll probably take someone less time to write the query statement to achieve the results than it did for me to assemble this question. By the way, the "product_option" table image is truncated but it illustrated the general idea of the data structure. The MySQL server version is 5.1.45.

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• Wmode transparent and symbols issue with foreign keyboard

  - by Boun

  Hello, I have the known issue with wmode transparent and input textfield in my page. I know that the question is often asked but I have a special situation with that case. I need to embed my swf with wmode=transparent but in my swf I have an input textfield and the bug with "@" or "." symbols exists. I have a french keyboard and I decided to overcome this problem with a string replacement with the FirefoxWmodeFix class from Manmaru (see the link below). http://www.manmaru.fr/mlab/?p=95 It works for my keyboard but I need that "trick" with EN/DE/IT keyboard. Could anyone help me with the right combination of keys on different keyboard and different OS system to display "@" and "." symbols. I don't have any foreign Windows system to get the key code for each combination. Or if anyone has another solution, I will be pleased to hear that one. Thanks in advance for any help.

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• Custom certificate as proof of transaction

  - by Andy

  I'm developing a site where a user conducts a given transaction and once completed, the user is issued with a 'secure certificate'. The certificate serves as proof of the transaction and the user is able to upload the certificate at a later stage, to view the details of the transaction. At the moment I'm using a custom XML document with encrypted fields. It works perfect, but I would like a standardized approach, such as an X.509 certificate. I'm no encryption expert, but from what I gather, X.509 is more geared towards SSL issued by a CA. Is it possible to create your own valid valid CRT file? As a test, I created a CRT file with the example provided on WikiPedia. However, when I open the file in Windows I get this warning: Invalid Public Key Security Object File - This file is invalid as the following: Security Certificate. Not having much luck here, so time to ask the experts. What direction should I be heading in? Any guidance would be greatly appreciated.

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• postgres store with composite value type, or a better way of attributing an inverted index

  - by Hassan Syed

  can't seem to figure out the syntax for populating a hstore with a value of composite type -- note: I do not want to convert a record to a hstore. select hstore('hello => ROW(1,2)'); I know it's something simple; However, google is not my friend today. use case : custom inverted index. The data is modelling an inverted index of lexemes, the composite data types are various probabilities related to the lexemes which I will use to implement document clustering. Does anyone know a better way of doing this ? I'm open to using an external system if it allows attaching attributes to key-posting pairs in the inverted index. I'd use something external if it had solid support for what I am trying to do, I suspect that sticking 3-10k lexemes per tuple and then doing batch processing on them is gonna be nasty as the whole hstore will have to be parsed and converted .

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• PostgreSQL - disabling constraints

  - by azp74

  I have a table with approx 5 million rows which has a fk constraint referencing the primary key of another table (also approx 5 million rows). I need to delete about 75000 rows from both tables. I know that if I try doing this with the fk constraint enabled it's going to take an unacceptable amount of time. Coming from an Oracle background my first thought was to disable the constraint, do the delete & then reenable the constraint. PostGres appears to let me disable constraint triggers if I am a super user (I'm not, but I am logging in as the user that owns/created the objects) but that doesn't seem to be quite what I want. The other option is to drop the constraint and then reinstate it. I'm worried that rebuilding the constraint is going to take ages given the size of my tables. Any thoughts?

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• Does DB2 have an "insert or update" statement?

  - by Mikael Eriksson

  From my code (Java) I want to ensure that a row exists in the database (DB2) after my code is executed. My code now does a select and if no result is returned it does an insert. I really don't like this code since it exposes me to concurrency issuses when running in a multi-threaded environment. What I would like to do is to put this logic in DB2 instead of in my Java code. Does DB2 have an "insert-or-update" statement? Or anything like it that I can use? For example: insertupdate into mytable values ('myid') Another way of doing it would probably be to allways do the insert and catch "SQL-code -803 primary key already exists", but I would like to avoid that if possible.

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• NSSortDescriptor for NSFetchRequest sorting unexpectedly

  - by E-Madd

  My entity has a property (sortOrder) that is of the type Decimal(NSDecimalNumber) but when I execute a fetch request using that property as a key, I get back results in a seemingly random order. If I output the value of the property I get really strange values until I get it's intValue. Example: The first run produces this result. The first value is the raw value of the property. The second is the intValue, the actual value of the property when I created the object - or at least I thought. 85438160 10 74691424 20 Second run... 85333744 10 85339168 20 Third... 85263696 20 85269568 10 What the hell?

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