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  • How do I perform a batch insert in Django?

    - by Thierry Lam
    In mysql, you can insert multiple rows to a table in one query for n 0: INSERT INTO tbl_name (a,b,c) VALUES(1,2,3),(4,5,6),(7,8,9), ..., (n-2, n-1, n); Is there a way to achieve the above with Django queryset methods? Here's an example: values = [(1, 2, 3), (4, 5, 6), ...] for value in values: SomeModel.objects.create(first=value[0], second=value[1], third=value[2]) I believe the above is calling an insert query for each iteration of the for loop. I'm looking for a single query, is that possible in Django?

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  • How to protect compiled Java classes?

    - by Registered User
    I know, many similar questions has been asked here. I am not asking if I can protect my compiled Java class - because obviously you will say 'no you can't'. I am asking what is the best known method of protecting Java classes against de-compiling? If you aware of any research or academic paper in this field please do let me know. Also if you have used some methods or software please share you experience? Any kind of information will be very useful. Thank you.

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  • Representing Sparse Data in PostgreSQL

    - by Chris S
    What's the best way to represent a sparse data matrix in PostgreSQL? The two obvious methods I see are: Store data in a single a table with a separate column for every conceivable feature (potentially millions), but with a default value of NULL for unused features. This is conceptually very simple, but I know that with most RDMS implementations, that this is typically very inefficient, since the NULL values ususually takes up some space. However, I read an article (can't find its link unfortunately) that claimed PG doesn't take up data for NULL values, making it better suited for storing sparse data. Create separate "row" and "column" tables, as well as an intermediate table to link them and store the value for the column at that row. I believe this is the more traditional RDMS solution, but there's more complexity and overhead associated with it. I also found PostgreDynamic, which claims to better support sparse data, but I don't want to switch my entire database server to a PG fork just for this feature. Are there any other solutions? Which one should I use?

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  • Overriding equals, hashCode and toString in a Clojure deftype

    - by mikera
    I'm trying to create a new type in Clojure using deftype to implement a two dimensional (x,y) coordinate, which implements a "Location" protocol. I'd also like to have this implement the standard Java equals, hashCode and toString methods. My initial attempt is: (defprotocol Location (get-x [p]) (get-y [p]) (add [p q])) (deftype Point [#^Integer x #^Integer y] Location (get-x [p] x) (get-y [p] y) (add [p q] (let [x2 (get-x q) y2 (get-y q)] (Point. (+ x x2) (+ y y2)))) Object (toString [self] (str "(" x "," y ")")) (hashCode [self] (unchecked-add x (Integer/rotateRight y 16))) (equals [self b] (and (XXXinstanceofXXX Location b) (= x (get-x b)) (= y (get-y b))))) However the equals method still needs some way of working out if the b parameter implements the Location protocol. What is the right approach? Am I on the right track?

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  • How do I catch jQuery $.getJSON (or $.ajax with datatype set to 'jsonp') error when using JSONP?

    - by Andy May
    Is it possible to catch an error when using JSONP with jQuery? I've tried both the $.getJSON and $.ajax methods but neither will catch the 404 error I'm testing. Here is what I've tried (keep in mind that these all work successfully, but I want to handle the case when it fails): jQuery.ajax({ type: "GET", url: handlerURL, dataType: "jsonp", success: function(results){ alert("Success!"); }, error: function(XMLHttpRequest, textStatus, errorThrown){ alert("Error"); } }); And also: jQuery.getJSON(handlerURL + "&callback=?", function(jsonResult){ alert("Success!"); }); I've also tried adding the $.ajaxError but that didn't work either: jQuery(document).ajaxError(function(event, request, settings){ alert("Error"); }); Thanks in advance for any replies!

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  • How would I best address this object type heirachy? Some kind of enum heirarchy?

    - by FerretallicA
    I'm curious as to any solutions out there for addressing object heirarchies in an ORM approach (in this instance, using Entity Framework 4). I'm working through some docs on EF4 and trying to apply it to a simple inventory tracking program. The possible types for inventory to fall into are as follows: INVENTORY ITEM TYPES: Hardware PC Desktop Server Laptop Accessory Input (keyboards, scanners etc) Output (monitors, printers etc) Storage (USB sticks, tape drives etc) Communication (network cards, routers etc) Software What recommendations are there for handling enums in a situation like this? Are enums even the solution? I don't really want to have a ridiculously normalised database for such a relatively simple experiment (eg tables for InventoryType, InventorySubtype, InventoryTypeToSubtype etc). I don't really want to over-complicate my data model with each subtype being inherited even though no additional properties or methods are included (except PC types which would ideally have associated accessories and software but that's probably out of scope here). It feels like there should be a really simple, elegant solution to this but I can't put my finger on it. Any assistance or input appreciated!

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  • Is yield break equivalent to returning Enumerable<T>.Empty from a method returning IEnumerable<T>

    - by Mike Two
    These two methods appear to behave the same to me public IEnumerable<string> GetNothing() { return Enumerable.Empty<string>(); } public IEnumerable<string> GetLessThanNothing() { yield break; } I've profiled each in test scenarios and I don't see a meaningful difference in speed, but the yield break version is slightly faster. Are there any reasons to use one over the other? Is one easier to read than the other? Is there a behavior difference that would matter to a caller?

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  • http(/* argument here */) How is this Object (Http) being used without an explicit or implicit meth

    - by Randin
    In the example for coding with Json using Databinder Dispatch Nathan uses an Object (Http) without a method, shown here: import dispatch._ import Http._ Http("http://www.fox.com/dollhouse/" >>> System.out ) How is he doing this? Thank you for all of the answers unfortunatly I was not specific enough... It looks like it is simply passing an argument to a constructor of class or companion object Http. In another example, I've seen another form: http = new Http http(/* argument here */) Is this valid Scala? I guess it must be, because the author is a Scala expert. But it makes no sense to me. Actions are usually performed by invoking methods on objects, whether explicitly as object.doSomething() or implicitly as object = something (using the apply() method underneath the syntactic sugar). All I can think of is that a constructor is being used to do something in addition to constructing an object. In other words, it is having side effects, such as in this case going off and doing something on the web.

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  • Weird generics compile error.

    - by Jouke van der Maas
    I have two classes, a base class and a child class. In the base class i define a generic virtual method: protected virtual Bar Foo<T() where T : Bar {} Then in my child class i try to do this: protected override BarChild Foo() // BarChild inherits Bar { return base.Bar<T as BarChild() } Visual studio gives this weird error: The type 'T' cannot be used as type parameter 'T' in the generic type or method 'Foo()'. There is no boxing conversion or type parameter conversion from 'T' to 'Bar'. Repeating the where clause on the child's override also gives an error: Constraints for override and explicit interface implementation methods are inherited from the base method, so they cannot be specified directly So what am i doing wrong here?

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  • Difference between "traditional" COM and COM+ (in Component Services)

    - by kizzx2
    By the "traditional" way I mean registering the DLL in registry. There seems to be another method to set up it by going to mmc-Component Services-COM+ Applications and adding the .tlb file. I have a COM library that supports both methods. When it installs, it registers itself in the registry as a COM component and it works fine. However, when I added the .tlb file using the Component Services method, the behavior seems to be different and it starts giving out errors. I suspect it has something to do with marshaling and inter-process object transfer? (Sorry, I'm really a noob in the COM area) Can anyone point me to a good resource to clear my understanding?

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  • How to prevent "Local transaction already has 1 non-XA Resource" exception?

    - by Zeratul
    Hi, I'm using 2 PU in stateless EJB and each of them is invoked on one method: @PersistenceContext(unitName="PU") private EntityManager em; @PersistenceContext(unitName="PU2") private EntityManager em2; @TransactionAttribute(TransactionAttributeType.REQUIRES_NEW ) public void getCandidates(final Integer eventId) throws ControllerException { ElectionEvent electionEvent = em.find(ElectionEvent.class, eventId); ... Person person = getPerson(candidate.getLogin()); ... } @TransactionAttribute(TransactionAttributeType.REQUIRES_NEW ) private Person getPerson(String login) throws ControllerException { Person person = em2.find(Person.class, login); return person; } Those methods are annotated with REQUIRES_NEW transcaction to avoid this exception. When I was calling these method from javaFX applet, all worked as expected. Now I'm trying to call them from JAX-RS webservice (I don't see any logical difference as in both cases ejb was looked up in initial context) and I keep getting this exception. When I set up XADatasource in glassfish 2.1 connection pools, I got nullpointer exception on em2. Any ideas what to try next? Regards

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  • Xcode, changing applications subfolder?

    - by fuzzygoat
    Hi have noticed today whilst writing a simple iPhone app that Xcode sometimes starts a new folder in applications, whilst your still working on the same app. /Users/Fuzzygoat/Library/Application Support/iPhone Simulator/User/Applications/4E5EF4F0-F410-46A6-888C-0D23BB97D2DC Does anyone know what causes Xcode to swap to a new app folder (i.e. the one named "4E5EF4F0-F410-46A6-888C-0D23BB97D2DC") EDIT_001: One thing I have noticed is that I have been doing a lot of quitting an application and restarting to check a set of archive methods, and that does tend to confuse it sometimes. A couple of times it has not found saved data, I guess this is just a side effect of constantly running the simulator over and over via Xcode. Things seem to go just fine if I test on the Simulator without Xcode, for a start the folder keeps the same name. NB: I am using NSSearchPathForDirectoriesInDomains to get the documents folder each time. gary

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  • What to name a method

    - by coffeeaddict
    I'm debating what to name this method. CloseCashTransaction(Cash.Id, -1, true); or CompleteCyberCashTransaction(Cash.Id, -1, true); or neither are good? In business terms/process by sending in these 3 values I'm essentially "closing the transaction" or "completing the transaction" in our workflow. However on the developer side, I cant' infer wtf "Complete" or "Close" means. It forces me to look into the internals of the method. My struggle is that I try to name methods to infer what they are doing. Complete is just way too general and forces the consumer of the method to dive into the code every time I use words like this. When I see stuff like this all over code, I have to take so much time to figure out what they are actually doing. And if the comments suck, I end up having to look at all logic in that method because the comments nor the method name really infer what's going on.

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  • Objective-C : Member variable is losing reference between method calls.

    - by Winston
    Hello, I've been having with an objective-c class which appears to be losing its pointer reference between methods of the same class. In the MyTableViewController.h file, I declare: @interface SettingsTableViewController : UITableViewController <UITextFieldDelegate>{ OCRAppDelegate *delegate; } MyTableViewController.m file - (id) init { self = [ super initWithStyle: UITableViewStyleGrouped ]; delegate = [(OCRAppDelegate *)[[UIApplication sharedApplication] delegate] retain]; } The problem is when the "MyTableViewController" view appears again and a different method is executed within that same class, the delegate pointer (which was assigned during the init method) is no longer there. I tried to retain, but to no avail. Would anyone know why this is, it seems like perhaps it is a fundamental Objective-C issue which I am missing. Appreciate your help. Thanks, Winston

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  • Custom array class with assotiated objects

    - by FancyDancy
    I have a simple structure, it's just an array of model's objects. For example, it's a users with books. @books = Book.find(:all, :include = :users) I need to check, does user have a book? I have written a helper method: def has_book?(user_id) @books.select{|b| b.user_id == user_id}.any? end Then, i need to get only books from selected library def in_library(n) @books.select{|b| b.library == n} end I have tried to make custom Array class: class BooksList < Array def initialize(books) self << books end # its my custom methods def has_book?(user_id) self.select{|b| b.user_id == user_id}.any? end def in_library(n) self.select{|b| b.library == n} end end It works, but i have only one problem. I can't access Book's assotiated object (user). So i can't write: @books = BookList.new(Book.find(:all, :include => :users)) @books.first.user.id # it says undefined method `user' for #<Array:0x104b43e08>

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  • How do I Call a method from other Class

    - by balexandre
    Hi guys, I'm having some trouble figuring out to call methods that I have in other classes #import "myNewClass.h" #import "MainViewController.h" @implementation MainViewController @synthesize txtUsername; @synthesize txtPassword; @synthesize lblUserMessage; - (IBAction)calculateSecret { NSString *usec = [self calculateSecretForUser:txtUsername.text withPassword:txtPassword.text]; [lblUserMessage setText:usec]; [usec release]; } ... myNewClass.h #import <Foundation/Foundation.h> @interface myNewClass : NSObject { } - (NSString*)CalculateSecretForUser:(NSString *)user withPassword:(NSString *)pwd; @end myNewClass.m #import "myNewClass.h" @implementation myNewClass - (NSString*)CalculateSecretForUser:(NSString *)user withPassword:(NSString *)pwd { NSString *a = [[NSString alloc] initWithFormat:@"%@ -> %@", user, pwd]; return a; } @end the method CalculateSecretForUser always says 'MainViewController' may not respond to '-calculateSecretForUser:withPassword:' what am I doing wrong here?

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  • How to create Custom action project with WIX 2.0

    - by Venkat
    Hi, I have installed WIX 2.0 (and Votive). I need to create user defined custom actions using the Custom action project. I found the custom action project template in VS2008 when WIX 3.0 is installed. Now, i couldnt find any template in VS2005 with WIX 2.0. Can anyone plz let me know how can i create a custom action project( class with some custom action)..like this [CustomAction] public static ActionResult InstallItem1(Session session) I think Microsoft.WindowsInstaller and Microsoft.Deployment.WindowsInstaller are the references required (not sure) to create such methods but i couldnt find them in my machine.

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  • C# differences between Windows Mobile and regular Windows

    - by Matt
    Are there many differences between Windows and Windows Mobile as far as C# programming is concerned? I can write some moderately complicated programs in C#, but I'm not sure if it would just run perfectly on a Windows smartphone, or if something has to be done to port it. If so, is there a tool that will automatically revise code to make it mobile-compatible? The reason I ask is that the new Windows mobile 7 will only support a few methods of app development, one of which is C#. Also, do smartphones with non-windows operating systems have C# support available? Or can C# code be converted to Symbian or iPhone or whatever? Thanks for any help you can provide.

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  • Inheriting from class that inherits from DynamicObject

    - by SeveQ
    Hello there, I'm experimenting with C# 4.0's dynamic object model. I've created an abstract class named "Block" that inherits from DynamicObject. It overrides TryGetMember and TrySetMember. Furthermore I've created a usable class named "Brush" that inherits from "Block". I want it to be usable dynamically. But when I create a dynamic object from it and try to access a runtime bound member, it pelts me with an exception telling me that the member doesn't exist. The overridden TryGetMember or TrySetMember methods of the abstract parent class aren't getting called. Is this behaviour to be expected? Thank you!

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  • improving conversions to binary and back in C#

    - by Saad Imran.
    I'm trying to write a general purpose socket server for a game I'm working on. I know I could very well use already built servers like SmartFox and Photon, but I wan't to go through the pain of creating one myself for learning purposes. I've come up with a BSON inspired protocol to convert the the basic data types, their arrays, and a special GSObject to binary and arrange them in a way so that it can be put back together into object form on the client end. At the core, the conversion methods utilize the .Net BitConverter class to convert the basic data types to binary. Anyways, the problem is performance, if I loop 50,000 times and convert my GSObject to binary each time it takes about 5500ms (the resulting byte[] is just 192 bytes per conversion). I think think this would be way too slow for an MMO that sends 5-10 position updates per second with a 1000 concurrent users. Yes, I know it's unlikely that a game will have a 1000 users on at the same time, but like I said earlier this is supposed to be a learning process for me, I want to go out of my way and build something that scales well and can handle at least a few thousand users. So yea, if anyone's aware of other conversion techniques or sees where I'm loosing performance I would appreciate the help. GSBitConverter.cs This is the main conversion class, it adds extension methods to main datatypes to convert to the binary format. It uses the BitConverter class to convert the base types. I've shown only the code to convert integer and integer arrays, but the rest of the method are pretty much replicas of those two, they just overload the type. public static class GSBitConverter { public static byte[] ToGSBinary(this short value) { return BitConverter.GetBytes(value); } public static byte[] ToGSBinary(this IEnumerable<short> value) { List<byte> bytes = new List<byte>(); short length = (short)value.Count(); bytes.AddRange(length.ToGSBinary()); for (int i = 0; i < length; i++) bytes.AddRange(value.ElementAt(i).ToGSBinary()); return bytes.ToArray(); } public static byte[] ToGSBinary(this bool value); public static byte[] ToGSBinary(this IEnumerable<bool> value); public static byte[] ToGSBinary(this IEnumerable<byte> value); public static byte[] ToGSBinary(this int value); public static byte[] ToGSBinary(this IEnumerable<int> value); public static byte[] ToGSBinary(this long value); public static byte[] ToGSBinary(this IEnumerable<long> value); public static byte[] ToGSBinary(this float value); public static byte[] ToGSBinary(this IEnumerable<float> value); public static byte[] ToGSBinary(this double value); public static byte[] ToGSBinary(this IEnumerable<double> value); public static byte[] ToGSBinary(this string value); public static byte[] ToGSBinary(this IEnumerable<string> value); public static string GetHexDump(this IEnumerable<byte> value); } Program.cs Here's the the object that I'm converting to binary in a loop. class Program { static void Main(string[] args) { GSObject obj = new GSObject(); obj.AttachShort("smallInt", 15); obj.AttachInt("medInt", 120700); obj.AttachLong("bigInt", 10900800700); obj.AttachDouble("doubleVal", Math.PI); obj.AttachStringArray("muppetNames", new string[] { "Kermit", "Fozzy", "Piggy", "Animal", "Gonzo" }); GSObject apple = new GSObject(); apple.AttachString("name", "Apple"); apple.AttachString("color", "red"); apple.AttachBool("inStock", true); apple.AttachFloat("price", (float)1.5); GSObject lemon = new GSObject(); apple.AttachString("name", "Lemon"); apple.AttachString("color", "yellow"); apple.AttachBool("inStock", false); apple.AttachFloat("price", (float)0.8); GSObject apricoat = new GSObject(); apple.AttachString("name", "Apricoat"); apple.AttachString("color", "orange"); apple.AttachBool("inStock", true); apple.AttachFloat("price", (float)1.9); GSObject kiwi = new GSObject(); apple.AttachString("name", "Kiwi"); apple.AttachString("color", "green"); apple.AttachBool("inStock", true); apple.AttachFloat("price", (float)2.3); GSArray fruits = new GSArray(); fruits.AddGSObject(apple); fruits.AddGSObject(lemon); fruits.AddGSObject(apricoat); fruits.AddGSObject(kiwi); obj.AttachGSArray("fruits", fruits); Stopwatch w1 = Stopwatch.StartNew(); for (int i = 0; i < 50000; i++) { byte[] b = obj.ToGSBinary(); } w1.Stop(); Console.WriteLine(BitConverter.IsLittleEndian ? "Little Endian" : "Big Endian"); Console.WriteLine(w1.ElapsedMilliseconds + "ms"); } Here's the code for some of my other classes that are used in the code above. Most of it is repetitive. GSObject GSArray GSWrappedObject

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  • Python mechanize - two buttons of type 'submit'

    - by directedition
    I have a mechanize script written in python that fills out a web form and is supposed to click on the 'create' button. But there's a problem, the form has two buttons. One for 'add attached file' and one for 'create'. Both are of type 'submit', and the attach button is the first one listed. So when I select the forum and do br.submit(), it clicks on the 'attach' button instead of 'create'. Extensive Googling has yielded nothing useful for selecting a specific button in a form. Does anyone know of any methods for skipping over the first 'submit' button and clicking the second?

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  • C++/CLI .ToString() returning error

    - by George Johnston
    I am a beginner to C++/CLI as I come from a C# background. I am currently writing a wrapper for some native C++ code. I have the following methods: void AddToBlockList(System::String^ address) { char* cAddress = (char*)(void*)Marshal::StringToHGlobalAnsi(address); _packetFilter->AddToBlockList(cAddress); } void AddToBlockList(IPAddress^ address) { char* cAddress = (char*)(void*)Marshal::StringToHGlobalAnsi(address.ToString()); _packetFilter->AddToBlockList(cAddress); } ...The first method works fine and converts my string into the character array. However, the second function with the IPAddress object as the signiture gives me the following error: error C2228: left of '.ToString' must have class/struct/union ...When I type ? address.ToString() ...in the command window, the IP Address prints. Not sure where I'm going wrong. Any ideas?

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  • What exactly is a property in Objective C ? What is the difference between a property ans an instance variable?

    - by tek3
    I am very much confused between instance variables and property. I have read number of posts regarding this but still i am not clear about it. I am from JAVA background and what i infer from objective C documentation is that a property is similar to JAVA BEAN CLASS (one having getter and setter of instance varibles). A property can accessed from other classes through its getter and setter methods while an instance variable is private and cannot be accessed from other classes. Am i right in thinking in this direction ?

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  • Flex 4 - Using .pfm/.pfb fonts

    - by Zed-K
    Hi everyone, I just switched to Flash Builder 4 & Flex 4 SDK, and it seems it's no longer possible to use a .pfm/.pfb font, either by embedding it or using it as a system font. I keep getting error messages, and Google can't find anybody having the same issue. I tried several methods: - copy/pasting the [Embed] statement which was working using Flex 3 SDK - installing the font and then try to simply call it by its name in a CSS declaration without embedding it ; seems to work for every .ttf and .otf system fonts, but not for .pfm/.pfm ones - using a Flash-generated swf which embeds the font So far none of these seems to work. Has anybody got an idea on how to achieve this? I actually don't care using a system font without embedding it as long as it works. I'll be really grateful if somebody could help me on this, I'm totally stuck and cannot use another font instead.

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  • unable to inject seam cache provider

    - by Joshua
    Env: Seam 2.2, ehcache-core 2.1.0 I tried injecting the CacheProvider using the following call in my bean scoped for session @In CacheProvider cacheProvider; WEB-INF\components.xml contains the following line to enable the cache provider <cache:eh-cache-provider/> The above configuration seems to return a null value for the cache provider Using the cache provider like this CacheProvider cacheProvider = CacheProvider.instance(); throws the following warning 15:29:27,586 WARN [CacheManager] Creating a new instance of CacheManager using the diskStorePath "C:\DOCUME~1\user5\LOCALS~1\Temp\" which is already used by an existing CacheManager. The source of the configuration was net.sf.ehcache.config.generator.Configuratio nSource$DefaultConfigurationSource@15ed0f9. The diskStore path for this CacheManager will be set to C:\DOCUME~1\user5\LOCALS ~1\Temp\\ehcache_auto_created_1276682367586. To avoid this warning consider using the CacheManager factory methods to create a singleton CacheManager or specifying a separate ehcache configuration (ehcache .xml) for each CacheManager instance. What am I missing here?

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