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  • Rails - operation outside of a rollback

    - by Brian Armstrong
    I have a before_create filter that checks if people are posting too many comments. If they are I want to flag their account. class Comment < ActiveRecord::Base before_create :check_rate_limit def check_rate_limit comments_in_last_minute = self.user.comments.count(:conditions => ["comments.created_at > ?", 1.minute.ago]) if comments_in_last_minute > 2 user.update_attribute :status, "suspended" return false end true end end The before filter returns false to stop the comment from being created. The problem is that this triggers a ROLLBACK which also undoes the changes I made to the user model. What's the correct pattern to accomplish this? Specifically: running a check each time an object is created and being able to edit another model if the check fails.

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  • How can I "best fit" an arbitrary cairo (pycairo) path?

    - by Daniel Straight
    It seems like given the information in stroke_extents() and the translate(x, y) and scale(x, y) functions, I should be able to take any arbitrary cairo (I'm using pycairo) path and "best fit" it. In other words, center it and expand it to fill the available space. Before drawing the path, I have scaled the canvas such that the origin is the lower left corner, up is y+, right is x+, and the height and width are both 1. Given these conditions, this code seems to correctly scale the path: # cr is the canvas extents = cr.stroke_extents() x_size = abs(extents[0]) + abs(extents[2]) y_size = abs(extents[1]) + abs(extents[3]) cr.scale(1.0 / x_size, 1.0 / y_size) I cannot for the life of me figure out the translating though. Is there a simpler approach? How can I "best fit" a cairo path on its canvas? Please ask for clarification if anything is unclear in this question.

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  • Limit a user to view only associated records in rails

    - by trobrock
    I have an application with three Models (Profile - SubModel - SubSubModel) chained together with has many relationships. I am trying to limit a user, after logging in, to only retrieving records that are associated with their Profile. I am very new to rails and this is what I had been trying in the Profile model has_many :submodels, :conditions => {:profile_id => self.id} but this is returning an empty data set when calling with Profile.find_by_id(1).submodels, how else could I achieve what I am trying to do. Or should I handle this in the controller or view instead, I thought it sounded well suited for the model to handle this.

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  • How do I display two different objects in a search?

    - by JZ
    github url I am using a simple search that displays search results: @adds = Add.search(params[:search]) In addition to the search results I'm trying to utilize a method, nearbys(), which displays objects that are close in proximity to the search result. The following method displays objects which are close to 2, but it does not display object 2. How do I display object 2 in conjunction with the nearby objects? @adds = Add.find(2).nearbys(10) While the above code functions, when I use search, @adds = Add.search(params[:search]).nearbys(10) a no method error is returned, undefined methodnearbys' for Array:0x30c3278` How can I search the model for an object AND use the nearbys() method AND display all results returned? Model: def self.search(search) if search find(:all, :conditions => ['address LIKE ?', "%#{search}%"]) # where('address LIKE ?', "%#{search}") else find(:all) end end

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  • What are some best practises and "rules of thumb" for creating database indexes?

    - by Ash
    I have an app, which cycles through a huge number of records in a database table and performs a number of SQL and .Net operations on records within that database (currently I am using Castle.ActiveRecord on PostgreSQL). I added some basic btree indexes on a couple of the feilds, and as you would expect, the peformance of the SQL operations increased substantially. Wanting to make the most of dbms performance I want to make some better educated choices about what I should index on all my projects. I understand that there is a detrement to performance when doing inserts (as the database needs to update the index, as well as the data), but what suggestions and best practices should I consider with creating database indexes? How do I best select the feilds/combination of fields for a set of database indexes (rules of thumb)? Also, how do I best select which index to use as a clustered index? And when it comes to the access method, under what conditions should I use a btree over a hash or a gist or a gin (what are they anyway?).

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  • How to prevent Closure Compiler from renaming "true", "false" and "null"

    - by Armagan Amcalar
    Google Closure Compiler renames all "true", "false" and "null" occurences in code like; var s = true, x = null, V = false; and uses these shorthands instead; in conditions such as; if (someVariable == s) now; Google Analytics code defines it's own "s" variable; overriding the value "true"; and as you can see this causes a lot of problems. I don't want to change GA code; I just want Closure Compiler to quit renaming true etc. Externs do not work. Do you know any way to accomplish this?

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  • How can I prevent MEF from throwing an exception when an Export is not found?

    - by Kilhoffer
    I have a class with an IList<T> property decorated with the [ImportMany(allowRecomposition = true)] attribute. There are some conditions in which the application might not find any available Exports of the requested type. Right now, it's throwing a CompositionException if no Exports of the requested type are found. I dislike application flow being determined by thrown exceptions, so I would rather not catch and react in this case. Rather, I just want program execution to continue. Is there a flag or something I can set to make this Import optional? I know for single import properties, you can do this: [Import(AllowDefault = true)] but 'AllowDefault' is not an option on the ImportMany attribute.

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  • Creating database desktop application with data manipulation in Netbeans using Java Persistence

    - by Lulu
    It's my first time to use Persistence in developing a Java program because I usually connect via JDBC. I read that for large amounts of data, it is best to use persistence. I tried playing with the CRUD example of Netbeans. It's not very helpful thought because it only connects to the DB and allows addition and deletion of records. I need something that will allow me to manipulate the data like if the value from column C1 of table T1 is such, it will retrieve data from table t2. In short, I need to apply conditions before knowing what to retrieve exactly. The example in CRUD example already has a specific table to retrieve and only acts like a database manager. How is it possible to retrieve a specific item first then from this, will determine the next steps to be done. I'm also using embedded JavaDB/Derby as my database (also my first time to use because I usually use remote mysql)

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  • Abstract out repeated code

    - by CookieMonster
    The code in this event is repeated exactly in two other event handlers. How do I put the repeated code into a method and call that method from the event handlers so I only have to maintain it in one place? I'm not sure how to pass the event args to the calling method. protected void gvDocAssoc_RowDataBound(object sender, GridViewRowEventArgs e) { if (e.Row.RowType == DataControlRowType.DataRow) { if ((Convert.ToString(DataBinder.Eval(e.Row.DataItem, "DETAIL_TYPE_DESC")) == "Transcript") && (Convert.ToString(DataBinder.Eval(e.Row.DataItem, "INSTITUTION_CODE")) == "")) { e.Row.BackColor = System.Drawing.Color.Red; } if ((Convert.ToString(DataBinder.Eval(e.Row.DataItem, "DETAIL_TYPE_DESC")) == "Certified Diploma") && (Convert.ToString(DataBinder.Eval(e.Row.DataItem, "INSTITUTION_CODE")) == "")) { e.Row.BackColor = System.Drawing.Color.Red; } if ((Convert.ToString(DataBinder.Eval(e.Row.DataItem, "DOC_TYPE_DESC")) == "Post Graduate conditions") && (Convert.ToString(DataBinder.Eval(e.Row.DataItem, "INSTITUTION_CODE")) == "")) { e.Row.BackColor = System.Drawing.Color.Red; } } }

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  • Can I inject a SessionBean into a JEE AroundInvoke-Interceptor?

    - by Michael Locher
    I have an EAR with modules: foo-api.jar foo-impl.jar interceptor.jar In foo-api there is: @Local FooService // (interface of a local stateless session bean) In foo-impl there is: @Stateless FooServiceImpl implements FooService //(implementation of the foo service) In interceptor.jar I want public class BazInterceptor { @EJB private FooService foo; @AroundInvoke public Object intercept( final InvocationContext i) throws Exception { // do someting with foo service return i.proceed(); } The question is: Will a Java EE 5 compliant application server (e.g. JBoss 5) inject into the interceptor? If no, what is good strategy for accessing the session bean? To consider: Deployment ordering / race conditions

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  • hierarchical clustering on correlations in Python scipy/numpy?

    - by user248237
    How can I run hierarchical clustering on a correlation matrix in scipy/numpy? I have a matrix of 100 rows by 9 columns, and I'd like to hierarchically clustering by correlations of each entry across the 9 conditions. I'd like to use 1-pearson correlation as the distances for clustering. Assuming I have a numpy array "X" that contains the 100 x 9 matrix, how can I do this? I tried using hcluster, based on this example: Y=pdist(X, 'seuclidean') Z=linkage(Y, 'single') dendrogram(Z, color_threshold=0) however, pdist is not what I want since that's euclidean distance. Any ideas? thanks.

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  • Adding an Object to Vector loses Reference using Java?

    - by thechiman
    I have a Vector that holds a number of objects. My code uses a loop to add objects to the Vector depending on certain conditions. My question is, when I add the object to the Vector, is the original object reference added to the vector or does the Vector make a new instance of the object and adds that? For example, in the following code: private Vector numbersToCalculate; StringBuffer temp = new StringBuffer(); while(currentBuffer.length() > i) { //Some other code numbersToCalculate.add(temp); temp.setLength(0); //resets the temp StringBuffer } What I'm doing is adding the "temp" StringBuffer to the numbersToCalculate Vector. Should I be creating a new StringBuffer within the loop and adding that or will this code work? Thanks for the help! Eric

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  • Which is better? private static vs private

    - by KiD0M4N
    In this code sample: public class SuperMan { private static bool IsProper(decimal x) { return x > 31.0m && x < 45.0m; } public bool CheckStuff(string a, string b, string c) { // lots of code, some of which introduces a variable x return IsProper(x) && /* other conditions */; } } Should IsProper(..) be a 'private static' or a 'private'. Assuming: IsProper(..) doesn't need to access any instance state.

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  • Changing the Default View Engine's view search behavior.

    - by bradhe
    I'm working with ASP.NET MVC 2. I have a bunch of partial views that I render based on different conditions within the same controller. I'd like to not put the physical partial view files in with the controller's other views. I know that when I want a ViewResult using the View() or PartialView() methods the default view engine will search through the folder in the Views directory associated with the controller (i.e. if my controller is called Register it will look in the Register folder under Views) and also in the Shared folder. Is there any way to change this behavior, or perhaps tell it specifically where to look for the view -- heck, even give it a specific file to render? Is that possible? Perhaps even a sub-folder under the Shared folder will work...

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  • How to calculate real-time stats?

    - by Diego Jancic
    I have a site with millions of users (well, actually it doesn't have any yet, but let's imagine), and I want to calculate some stats like "log-ins in the past hour". The problem is similar to the one described here: http://highscalability.com/blog/2008/4/19/how-to-build-a-real-time-analytics-system.html The simplest approach would be to do a select like this: select count(distinct user_id) from logs where date>='20120601 1200' and date <='20120601 1300' (of course other conditions could apply for the stats, like log-ins per country) Of course this would be really slow, mainly if it has millions (or even thousands) of rows, and I want to query this every time a page is displayed. How would you summarize the data? What should go to the (mem)cache? EDIT: I'm looking for a way to de-normalize the data, or to keep the cache up-to-date. For example I could increment an in-memory variable every time someone logs in, but that would help to know the total amount of logins, not the "logins in the last hour". Hope it's more clear now.

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  • Numeric comparison difficulty in R

    - by Matt Parker
    I'm trying to compare two numbers in R as a part of a if-statement condition: (a-b) >= 0.5 In this particular instance, a = 0.58 and b = 0.08... and yet (a-b) >= 0.5 is false. I'm aware of the dangers of using == for exact number comparisons, and this seems related: (a - b) == 0.5) is false, while all.equal((a - b), 0.5) is true. The only solution I can think of is to have two conditions: (a-b) > 0.5 | all.equal((a-b), 0.5). This works, but is that really the only solution? Should I just swear off of the = family of comparison operators forever?

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  • linux thread synchronization

    - by johnnycrash
    I am new to linux and linux threads. I have spent some time googling to try to understand the differences between all the functions available for thread synchronization. I still have some questions. I have found all of these different types of synchronizations, each with a number of functions for locking, unlocking, testing the lock, etc. gcc atomic operations futexes mutexes spinlocks seqlocks rculocks conditions semaphores My current (but probably flawed) understanding is this: semaphores are process wide, involve the filesystem (virtually I assume), and are probably the slowest. Futexes might be the base locking mechanism used by mutexes, spinlocks, seqlocks, and rculocks. Futexes might be faster than the locking mechanisms that are based on them. Spinlocks dont block and thus avoid context swtiches. However they avoid the context switch at the expense of consuming all the cycles on a CPU until the lock is released (spinning). They should only should be used on multi processor systems for obvious reasons. Never sleep in a spinlock. The seq lock just tells you when you finished your work if a writer changed the data the work was based on. You have to go back and repeat the work in this case. Atomic operations are the fastest synch call, and probably are used in all the above locking mechanisms. You do not want to use atomic operations on all the fields in your shared data. You want to use a lock (mutex, futex, spin, seq, rcu) or a single atomic opertation on a lock flag when you are accessing multiple data fields. My questions go like this: Am I right so far with my assumptions? Does anyone know the cpu cycle cost of the various options? I am adding parallelism to the app so we can get better wall time response at the expense of running fewer app instances per box. Performances is the utmost consideration. I don't want to consume cpu with context switching, spinning, or lots of extra cpu cycles to read and write shared memory. I am absolutely concerned with number of cpu cycles consumed. Which (if any) of the locks prevent interruption of a thread by the scheduler or interrupt...or am I just an idiot and all synchonization mechanisms do this. What kinds of interruption are prevented? Can I block all threads or threads just on the locking thread's CPU? This question stems from my fear of interrupting a thread holding a lock for a very commonly used function. I expect that the scheduler might schedule any number of other workers who will likely run into this function and then block because it was locked. A lot of context switching would be wasted until the thread with the lock gets rescheduled and finishes. I can re-write this function to minimize lock time, but still it is so commonly called I would like to use a lock that prevents interruption...across all processors. I am writing user code...so I get software interrupts, not hardware ones...right? I should stay away from any functions (spin/seq locks) that have the word "irq" in them. Which locks are for writing kernel or driver code and which are meant for user mode? Does anyone think using an atomic operation to have multiple threads move through a linked list is nuts? I am thinking to atomicly change the current item pointer to the next item in the list. If the attempt works, then the thread can safely use the data the current item pointed to before it was moved. Other threads would now be moved along the list. futexes? Any reason to use them instead of mutexes? Is there a better way than using a condition to sleep a thread when there is no work? When using gcc atomic ops, specifically the test_and_set, can I get a performance increase by doing a non atomic test first and then using test_and_set to confirm? *I know this will be case specific, so here is the case. There is a large collection of work items, say thousands. Each work item has a flag that is initialized to 0. When a thread has exclusive access to the work item, the flag will be one. There will be lots of worker threads. Any time a thread is looking for work, they can non atomicly test for 1. If they read a 1, we know for certain that the work is unavailable. If they read a zero, they need to perform the atomic test_and_set to confirm. So if the atomic test_and_set is 500 cpu cycles because it is disabling pipelining, causes cpu's to communicate and L2 caches to flush/fill .... and a simple test is 1 cycle .... then as long as I had a better ratio of 500 to 1 when it came to stumbling upon already completed work items....this would be a win.* I hope to use mutexes or spinlocks to sparilngly protect sections of code that I want only one thread on the SYSTEM (not jsut the CPU) to access at a time. I hope to sparingly use gcc atomic ops to select work and minimize use of mutexes and spinlocks. For instance: a flag in a work item can be checked to see if a thread has worked it (0=no, 1=yes or in progress). A simple test_and_set tells the thread if it has work or needs to move on. I hope to use conditions to wake up threads when there is work. Thanks!

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  • Can I populate multiple DropDownLists from one SqlDataSource using parameters?

    - by death_au
    Basically, I have four asp:DropDownLists and I wish to populate all of them from the same table, with certain conditions. For example, I have this data source: <asp:SqlDataSource ID="ReferenceDataSource1" runat="server" ConnectionString="<%$ ConnectionStrings:mrapConnectionString1 %> SelectCommand="SELECT * FROM [reference_data] WHERE ([component] = @component)" > <SelectParameters> <asp:Parameter DefaultValue="MB" Name="component" Type="String" /> </SelectParameters> </asp:SqlDataSource> And I want to know if I can change that component parameter to be different for each of my four dropdown lists. I tried adding the following code on the DataBinding event for my DropDown: ReferenceDataSource1.SelectParameters.Remove(ReferenceDataSource1.SelectParameters["component"]); ReferenceDataSource1.SelectParameters.Add("component", "MB"); But I ironically got a StackOverflowException...

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  • SQL Server join and wildcards

    - by Ernst
    I want to get the results of a left join between two tables, with both having a column of the same name, the column on which I join. The following query is seen as valid by the import/export wizard in SQL Server, but it always gives an error. I have some more conditions, so the size wouldn't be too much. We're using SQL Server 2000 iirc and since we're using an externally developed program to interact with the database (except for some information we can't retrieve that way), we can not simply change the column name. SELECT table1.*, table2.* FROM table1 LEFT JOIN table2 ON table1.samename = table2.samename At least, I think the column name is the problem, or am I doing something else wrong?

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  • help me to cheat with numericUpDown1_ValueChanged event

    - by alex
    I have a Form and numericupdown control located on it. I want that in some conditions (_condition1) user cannot be able to change a value of numericupdown control. How can I do it ? I wrote some code but it works twice (double time). class Form1 : Form { bool _condition1; int _previousValue; void numericUpDown1_ValueChanged(object sender, EventArgs e) { if(_condition1) { numericUpDown1.Value = (decimal)_previousValue; } else { _previousValue = (int)numericUpDown1.Value; } } } Control must be enable.

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  • Rail plugin acts_as_taggable_on :through

    - by Craig
    I have two models: class Employee < ActiveRecord::Base has_many :projects end class Project < ActiveRecord::Base acts_as_taggable_on :skills, :roles end I would like to find Employees using the tags associated with their projects. The geokit-rails plugin supports a similar concept, using its ':through' relationship. Ideally, I would be able to: specify which tags (i.e. skills, roles) would be included in the conditions order the employees by the total number of projects with matching tags be able to access the matching-tag count for each employee for the purposes of building a tag cloud Any thoughts would be appreciated.

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  • When is performance gain significant enough to implement that optimization?

    - by Zwei steinen
    Hi, following the text book, I do measure performance whenever I try optimizing my code. Sometimes, however, the performance gain is rather small and I can't decisively decide whether I should implement that optimization. For example, when a fix shortens an average response time of 100ms to 90ms under some conditions, should I implement that fix? What if it shortens 200ms to 190ms? How many condition should I try before I can conclude that it will be beneficial overall? I guess it's not possible to give a straight forward answer to this, as it depends on too many things, but is there a good rule of thumb that I should follow? Are there any guideline/best-practices?

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  • Remove a certain value from string which keeps on changing

    - by user2971375
    I m trying to make a utility to generate a Insert script of sql tables along with relational table. I got all the values in c#. Now I want to remove the one column name and its value from the script.most probably the identity column. Eg. The string I have (which keeps on changing with table name and varies) INSERT Core.Customers ([customerId],[customername],[customeradress],[ordernumber]) Values(123,N'Rahul',N'244 LIZ MORN',2334) NOW I know I have to remove CustomerId. (sometimes need to be replaces with @somevariable) Please give me an efficient way how to retrieve customerId value and Deleting column name and value . Conditions: insert script length and columns names keep changing. Method should return the deleted value. At some point of time customer id can be same as order id. In that case my string.remove method fails.

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  • How to check function parameters in Go

    - by deamon
    Guava Preconditions allows to check method parameters in Java easily. public void doUsefulThings(Something s, int x, int position) { checkNotNull(s); checkArgument(x >= 0, "Argument was %s but expected nonnegative", x); checkElementIndex(position, someList.size()); // ... } These check methods raise exceptions if the conditions are not met. Go has no exceptions but indicates errors with return values. So I wonder how an idiomatic Go version of the above code would look like.

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  • NSZombieEnabled hides EXC_BAD_ACCESS error entirely

    - by David Liu
    So I have a subclass of a UIView that starts causing EXC_BAD_ACCESS errors when I go through a specific set of conditions (run on iPad instead of iPhone or simulator, first login only). It throws the exception when the UIView subclass gets deallocated, during the last line, where I have [super dealloc]. I heard about using NSZombieEnabled, so I tossed that on to see if I could get any more information about it, but now it hides the error completely! Does anyone know a bit more about this type of situation? I thought NSZombie would start spewing stuff into my console like before, but I'm hoping that the nonexistance of errors would tell me some sort of information as well.

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