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  • I want absolute atomicity on a single couchdb instance (insert, fail if already existing)

    - by MatternPatching
    I've come to really love the couchdb style of organizing and updating data, but there are a few situations where I really need to be able to create an entry and determine if an equivalent entry is already in existence before returning to the user. The only situation that this is absolutely necessary for my application is user registration. I'm fine with having all user registration writes go to a particular, designated couchdb instance known as the "registration-instance". I want to hash the user_id into some _id to use. Then execute a put with this _id, but fail if the _id is already inserted. I need to return to the user that the user name is already reserved, and I cannot detect the conflict later and resolve it at that point, because the user would be under the impression that they had reserved the user name. I don't see why couchdb couldn't provide some way to do this, under the assumption that you designate that inserts for a particular "type" of document always are routed to a particular instance.

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  • Prevent Users from Performing an Action Twice

    - by TheOnly92
    We have some problems with users performing a specific action twice, we have a mechanism to ensure that users can't do it but somehow it still happens. Here is how our current mechanism works: Client side: The button will be disabled after 1 click. Server side: We have a key hash in the URL which will be checked against the key stored in SESSIONS, once it matches, the key is deleted. Database side: Once the action is performed, there is a field to be flagged indicating the user has completed the action. However, with all these measures, still there are users able to perform the action twice, are there any more safer methods?

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  • Dynamic Custom Fields for Data Model

    - by Jerry Deng
    I am in the process of creating a dynamic database where user will be able to create resource type where he/she can add custom fields (multiple texts, strings, and files) Each resource type will have the ability to display, import, export its data; I've been thinking about it and here are my approaches. I would love to hear what do you guys think. Ideas: just hashing all the custom data in a data field (pro: writing is easier, con: reading back out may be harder); children fields (the model will have multiple fields of strings, fields of text, and fields for file path); fixed number of custom fields in the same table with a key mapping data hash stored in the same row; Non-SQL approach, but then the problem would be generating/changing models on the fly to work with different custom fields;

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  • Constants in Model and View with select option and show view

    - by caplod
    i have a some values ,that i use in my model as constants. class Animal < ActiveRecord::Base LEGS = {:vierbeiner => 4, :zweibeiner => 2 } end in the form (formtastic) for the collection i use: <%= f.input :legs, :as => :select, :collection => Animal::LEGS => but how do i format the show view so instead showing me the number , the key of the hash? in show view i have: <p> <strong>Legs:</strong> <%=h @animal.legs %> </p>

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  • Where can I find an array of the unassigned Unicode code points for a particular block?

    - by gitparade
    At the moment, I'm writing these arrays by hand. For example, the Miscellaneous Mathematical Symbols-A block has an entry in hash like this: my %symbols = ( ... miscellaneous_mathematical_symbols_a => [(0x27C0..0x27CA), 0x27CC, (0x27D0..0x27EF)], ... ) The simpler, 'continuous' array miscellaneous_mathematical_symbols_a => [0x27C0..0x27EF] doesn't work because Unicode blocks have holes in them. For example, there's nothing at 0x27CB. Take a look at the code chart [PDF]. Writing these arrays by hand is tedious, error-prone and a bit fun. And I get the feeling that someone has already tackled this in Perl!

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  • .NET Publishing files but allowing them to be edited?

    - by acidzombie24
    I had media files require in the project so i did this + set built action to content Now here are my problems I would like my app to check for .NET and to check for other installs which is fine now that i made a prerequisite I would like to copy media files when i publish One of these files is a config file i like the user to edit Problem is after doing 1 which gives me a publish folder with a setup.exe + files i have no idea where my installed files are and if i modify the file.ext.deploy i get an error about the hash of the file modified. Is there a way i can have plain non deploy files or distribute the bin/release folder as i normally do but add something to check my prerequisite?

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  • What is a simple C library for a set of integer sets?

    - by conradlee
    I've got to modify a C program and I need to include a set of unsigned integer sets. That is, I have millions of sets of integers (each of these integer sets contains between 3 and 100 integers), and I need to store these in some structure, lets call it the directory, that can in logarithmic time tell me whether a given integer set already exists in the directory. The only operations that need to be defined on the directory is lookup and insert. This would be easy in languages with built-in support for useful data structures, but I'm a foreigner to C and looking around on Google did (surprisingly) not answer my question satisfactorily. This project looks about right: http://uthash.sourceforge.net/ but I would need to come up with my own hash key generator. This is a standard, simple problem, so I hope there is a standard and simple solution.

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  • what is the underlying data structure of a set c++?

    - by zebraman
    I would like to know how a set is implemented in C++. If I were to implement my own set container without using the STL provided container, what would be the best way to go about this task? I understand STL sets are based on the abstract data structure of a binary search tree. So what is the underlying data structure? An array? Also, how does insert() work for a set? How does the set check whether an element already exists in it? I read on wikipedia that another way to implement a set is with a hash table. How would this work?

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  • PHP Variable Encryption

    - by NCoder
    I have the following code that creates an encryption in PHP: $password = "helloworld"; $passwordupper = strtoupper($password); $passwordencode = mb_convert_encoding($passwordupper, 'UTF-16LE'); $passwordsha1 = hash("SHA1", $passwordencode); $passwordbase64 = base64_encode($passwordsha1); The instructions I have from the system I'm trying to connect to states: The encoding process for passwords is: first convert to uppercase, then Unicode it in little-endian UTF 16, then SHA1 it then base64 encode it. I think I'm doing something wrong in my code. Any ideas?! Thanks! NCoder

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  • Mongoose Not Creating Indexes

    - by wintzer
    I have been trying all afternoon to get my node.js application to create MongoDB indexes properly. I am using the Mongoose ODM and in my schema definition below I have the username field set to a unique index. The collection and document all get created properly, it's just the indexes that aren't working. All the documentation says that the ensureIndex command should be run at startup to create any indexes, but none are being made. I'm using MongoLab for hosting if that matters. I have also repeatedly dropped the collection. Please tell me what I'm doing wrong. var schemaUser = new mongoose.Schema({ username: {type: String, index: { unique: true }, required: true}, hash: String, created: {type: Date, default: Date.now} }, { collection:'Users' }); var User = mongoose.model('Users', schemaUser); var newUser = new Users({username:'wintzer'}) newUser.save(function(err) { if (err) console.log(err); });

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  • A new Rails idea in views and no more controller. maybe better maybe worse, i need help if this is t

    - by Totty
    Hy, I was thinking that all my website will have use of cells, using the known plugin cell for rails, so this is my idea: A table that contains 3 fields: id, view_name and layout. the layout will be a serialized hash. When a request is made, the layout field is requested and then in the view, default layout, will be unserialized the layout var, that looks like this: @layout[:sidecol][:gallery] = {... some params for it...}; @layout[:maincol][:comments] = {..params...}; In the <% #ruby code to render the cells in the @layout[:sidecol] % will be some ruby code that will loop over the @layout[:sidecol] and render all cells in it. the same occurs in the maincol div. What do you think? Positive in my opinion: More modular controller is used only for post easy change of structure easier to implement some kind of traking to see diferences on what layout is better or not. Negative: not found yet

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  • Not a statement?

    - by abelenky
    I have a simple little code fragment that is frustrating me: HashSet<long> groupUIDs = new HashSet<long>(); groupUIDs.Add(uid)? unique++ : dupes++; At compile time, it generates the error: Only assignment, call, increment, decrement, and new object expressions can be used as a statement HashSet.Add is documented to return a bool, so the ternary (?) operator should work, and this looks like a completely legitimate way to track the number of unique and duplicate items I add to a hash-set. When I reformat it as a if-then-else, it works fine. Can anyone explain the error, and if there is a way to do this as a simple ternary operator?

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  • [perl] Efficient processing of large text

    - by jesper
    I have text file that contains over one million urls. I have to process this file in order to assign urls to groups, based on host address: { 'http://www.ex1.com' = ['http://www.ex1.com/...', 'http://www.ex1.com/...', ...], 'http://www.ex2.com' = ['http://www.ex2.com/...', 'http://www.ex2.com/...', ...] } My current basic solution takes about 600mb of RAM to do this (size of file is about 300mb). Could You provide some more efficient ways? My current solution simply reads line by line, extracts host address by regex and put url into hash.

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  • How to fix missing RAID1 drive

    - by Sodved
    I had to do some fiddling about with my cables inside thebox and now I am getting a "Critical Error" about the RAID disks during startup. I have a gigabyte GA-MA770T-UD3 motherboard. Aparently the RAID controller is an AMD SB710 chip. I'm pretty sure I know what happenned. The first time I rebooted I had forgotten the power cable on one of the disks in the RAID1 (mirror) and let it boot up. So I shut down and put the power back in. So now when it boots up I go into the RAID admin interface (between the BIOS screen and the OS loading): it shows the RAID1 as in error the logical device has one disk and says the other is disconnected or missing the other physical disk shows up as a single disk If I boot to the OS (Windows 7 32 bit) the data all seems to be there. If I go into computer management it says my partition is on a disk and working OK. But the other disk is offline because: "The disk is offline because it has a signature collision with another disk that is online" So I am guessing because I STUPIDLY booted up with only one of the disks powered on, the other disk fell out of synch with the mirror and so now cannot rejoin the mirror. How do I fix this? I want to get the RAID1 mirror working again. There does not appear to be any "Repair" option in the basic RAID admin tool which I get into during startup before the OS boots. I have not made any explicit changes to the online one (but I guess the OS has probably written some admin data).

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  • Can you use POST to run a query in Solr (/select)

    - by RyanFetz
    I have queries that I am running against out solr index that sometimes have very long query parameters, I get errors when i run these queries, which i assume are do to the limit of a GET query parameters. Here is the method I use to query (JSON), this is to show I am using the Http Extensions (the client i use is a thin wrapper for HttpClient) not an end to end solution. 90% of the queries run fine, it is just when the params are large i get the 500 error from solr. I have read somewhere you can use POSt's when doing the select command but have not found examples of how to do it. Any help would be fantastic! public string GetJson(HttpQueryString qs) { using (var client = new DAC.US.Web.XmlHttpServiceClient(this.Uri)) { client.Client.DefaultHeaders.Authorization = new Microsoft.Http.Headers.Credential("Basic", DAC.US.Encryption.Hash.WebServiceCredintials); qs.Add("wt", "json"); if (!String.IsNullOrEmpty(this.Version)) qs.Add("version", this.Version); using (var response = client.Get(new Uri(@"select/", UriKind.Relative), qs)) { return response.Content.ReadAsString(); } } }

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  • Where can I find an array of the (un)assigned Unicode code points for a particular block?

    - by gitparade
    At the moment, I'm writing these arrays by hand. For example, the Miscellaneous Mathematical Symbols-A block has an entry in hash like this: my %symbols = ( ... miscellaneous_mathematical_symbols_a => [(0x27C0..0x27CA), 0x27CC, (0x27D0..0x27EF)], ... ) The simpler, 'continuous' array miscellaneous_mathematical_symbols_a => [0x27C0..0x27EF] doesn't work because Unicode blocks have holes in them. For example, there's nothing at 0x27CB. Take a look at the code chart [PDF]. Writing these arrays by hand is tedious, error-prone and a bit fun. And I get the feeling that someone has already tackled this in Perl!

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  • Find a common element within N arrays

    - by kunjaan
    If I have N arrays, what is the best(Time complexity. Space is not important) way to find the common elements. You could just find 1 element and stop. Edit: The elements are all Numbers. Edit: These are unsorted. Please do not sort and scan. This is not a homework problem. Somebody asked me this question a long time ago. He was using a hash to solve the problem. I was thinking if SO has solved similar problems.

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  • NoMethodError using Memcached Sinatra-style

    - by sevennineteen
    I've just installed Memcached on my Mac and updated my Sinatra app configuration as described in Heroku's documentation, but I'm getting a NoMethodError when trying to use the hash-based syntax they specify: >> CACHE['color'] = 'blue' >> CACHE['color'] Using explicit get and set methods as below seems to work fine. >> CACHE.set('color', 'blue') >> CACHE.get('color') If necessary I can use the latter syntax, but the former seems more elegant. I haven't tested this on Heroku's environment since I'd like whatever implementation I use to work on my local environment as well. Thanks!

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  • how to save image and data locally in iphone device

    - by MaheshBabu
    Hi folks, I am getting image and some details from .net web server. I need to store these details in iphone device memory(not in sdcard),Because I need to connect web services only one time,that is at installing my app. From Next time onwards i need to get data from device. I have some knowledge in java,In java i use files to store image and Hash table to store details. How can i done this in iphone. can any one pls help me. Thank u in advance.

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  • Javascript object encapsulation that tracks changes

    - by Raynos
    Is it possible to create an object container where changes can be tracked Said object is a complex nested object of data. (compliant with JSON). The wrapper allows you to get the object, and save changes, without specifically stating what the changes are Does there exist a design pattern for this kind of encapsulation Deep cloning is not an option since I'm trying to write a wrapper like this to avoid doing just that. The solution of serialization should only be considered if there are no other solutions. An example of use would be var foo = state.get(); // change state state.update(); // or state.save(); client.tell(state.recentChange()); A jsfiddle snippet might help : http://jsfiddle.net/Raynos/kzKEp/ It seems like implementing an internal hash to keep track of changes is the best option. [Edit] To clarify this is actaully done on node.js on the server. The only thing that changes is that the solution can be specific to the V8 implementation.

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  • Const-Qualification of Main's Parameters in C++

    - by pt2cv
    The C++ standard mandates that all conforming implementations support the following two signatures for main: int main(); int main(int, char*[]); In case of the latter signature, would the addition of (top-level) const-ness break any language rules? For example: int main(const int argc, char** const argv); From my understanding, top-level const qualification doesn't affect the function's signature hash, so it should be legal as far as the specification is concerned. Also, did anyone ever encounter an implementation which rejected this type of modification?

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  • Create a class that inherets DrawableGameComponent in XNA as a CLASS with custom functions

    - by user3675013
    using Microsoft.Xna.Framework.Graphics; using Microsoft.Xna.Framework.Media; using Microsoft.Xna.Framework; using Microsoft.Xna.Framework.Content; namespace TileEngine { class Renderer : DrawableGameComponent { public Renderer(Game game) : base(game) { } SpriteBatch spriteBatch ; protected override void LoadContent() { base.LoadContent(); } public override void Draw(GameTime gameTime) { base.Draw(gameTime); } public override void Update(GameTime gameTime) { base.Update(gameTime); } public override void Initialize() { base.Initialize(); } public RenderTarget2D new_texture(int width, int height) { Texture2D TEX = new Texture2D(GraphicsDevice, width, height); //create the texture to render to RenderTarget2D Mine = new RenderTarget2D(GraphicsDevice, width, height); GraphicsDevice.SetRenderTarget(Mine); //set the render device to the reference provided //maybe base.draw can be used with spritebatch. Idk. We'll see if the order of operation //works out. Wish I could call base.draw here. return Mine; //I'm hoping that this returns the same instance and not a copy. } public void draw_texture(int width, int height, RenderTarget2D Mine) { GraphicsDevice.SetRenderTarget(null); //Set the renderer to render to the backbuffer again Rectangle drawrect = new Rectangle(0, 0, width, height); //Set the rendering size to what we want spriteBatch.Begin(); //This uses spritebatch to draw the texture directly to the screen spriteBatch.Draw(Mine, drawrect, Color.White); //This uses the color white spriteBatch.End(); //ends the spritebatch //Call base.draw after this since it doesn't seem to recognize inside the function //maybe base.draw can be used with spritebatch. Idk. We'll see if the order of operation //works out. Wish I could call base.draw here. } } } I solved a previous issue where I wasn't allowed to access GraphicsDevice outside the main Default 'main' class Ie "Game" or "Game1" etc. Now I have a new issue. FYi no one told me that it would be possible to use GraphicsDevice References to cause it to not be null by using the drawable class. (hopefully after this last bug is solved it doesn't still return null) Anyways at present the problem is that I can't seem to get it to initialize as an instance in my main program. Ie Renderer tileClipping; and I'm unable to use it such as it is to be noted i haven't even gotten to testing these two steps below but before it compiled but when those functions of this class were called it complained that it can't render to a null device. Which meant that the device wasn't being initialized. I had no idea why. It took me hours to google this. I finally figured out the words I needed.. which were "do my rendering in XNA in a seperate class" now I haven't used the addcomponent function because I don't want it to only run these functions automatically and I want to be able to call the custom ones. In a nutshell what I want is: *access to rendering targets and graphics device OUTSIDE default class *passing of Rendertarget2D (which contain textures and textures should automatically be passed with a rendering target? ) *the device should be passed to this function as well OR the device should be passed to this function as a byproduct of passing the rendertarget (which is automatically associated with the render device it was given originally) *I'm assuming I'm dealing with abstracted pointers here so when I pass a class object or instance, I should be recieving the SAME object , I referenced, and not a copy that has only the lifespan of the function running. *the purpose for all these options: I want to initialize new 2d textures on the fly to customize tileclipping and even the X , y Offsets of where a WHOLE texture will be rendered, and the X and Y offsets of where tiles will be rendered ON that surface. This is why. And I'll be doing region based lighting effects per tile or even per 8X8 pixel spaces.. we'll see I'll also be doing sprite rotations on the whole texture then copying it again to a circular masked texture, and then doing a second copy for only solid tiles for masked rotated collisions on sprites. I'll be checking the masked pixels for my collision, and using raycasting possibly to check for collisions on those areas. The sprite will stay in the center, when this rotation happens. Here is a detailed diagram: http://i.stack.imgur.com/INf9K.gif I'll be using texture2D for steps 4-6 I suppose for steps 1 as well. Now ontop of that, the clipping size (IE the sqaure rendered) will be able to be shrunk or increased, on a per frame basis Therefore I can't use the same static size for my main texture2d and I can't use just the backbuffer Or we get the annoying flicker. Also I will have multiple instances of the renderer class so that I can freely pass textures around as if they are playing cards (in a sense) layering them ontop of eachother, cropping them how i want and such. and then using spritebatch to simply draw them at the locations I want. Hopefully this makes sense, and yes I will be planning on using alpha blending but only after all tiles have been drawn.. The masked collision is important and Yes I am avoiding using math on the tile rendering and instead resorting to image manipulation in video memory which is WHY I need this to work the way I'm intending it to work and not in the default way that XNA seems to handle graphics. Thanks to anyone willing to help. I hate the code form offered, because then I have to rely on static presence of an update function. What if I want to kill that update function or that object, but have it in memory, but just have it temporarily inactive? I'm making the assumption here the update function of one of these gamecomponents is automatic ? Anyways this is as detailed as I can make this post hopefully someone can help me solve the issue. Instead of tell me "derrr don't do it this wayyy" which is what a few people told me (but they don't understand the actual goal I have in mind) I'm trying to create basically a library where I can copy images freely no matter the size, i just have to specify the size in the function then as long as a reference to that object exists it should be kept alive? right? :/ anyways.. Anything else? I Don't know. I understand object oriented coding but I don't understand this XNA It's beggining to feel impossible to do anything custom in it without putting ALL my rendering code into the draw function of the main class tileClipping.new_texture(GraphicsDevice, width, height) tileClipping.Draw_texture(...)

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  • [PersistenceException: org.hibernate.exception.SQLGrammarException: could not execute query]

    - by doniyor
    i need help. i am trying to select from database thru sql statement in play framework, but it gives me error, i cannot figure out where the clue is. here is the code: @Transactional public static Users findByUsernameAndPassword(String username, String password){ String hash = DigestUtils.md5Hex(password); Query q = JPA.em().createNativeQuery("select * from USERS where" + "USERNAME=? and PASSWORD=?").setParameter(1, username).setParameter(2, password); List<Users> users = q.getResultList(); if(users.isEmpty()){ return null; } else{ return users.get(0); here is the eror message: [PersistenceException: org.hibernate.exception.SQLGrammarException: could not execute query] can someone help me please! any help i would appreciate! thanks

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  • optimizing oracle query

    - by deming
    I'm having a hard time wrapping my head around this query. it is taking almost 200+ seconds to execute. I've pasted the execution plan as well. SELECT user_id , ROLE_ID , effective_from_date , effective_to_date , participant_code , ACTIVE FROM CMP_USER_ROLE E WHERE ACTIVE = 0 AND (SYSDATE BETWEEN effective_from_date AND effective_to_date OR TO_CHAR(effective_to_date,'YYYY-Q') = '2010-2') AND participant_code = 'NY005' AND NOT EXISTS ( SELECT 1 FROM CMP_USER_ROLE r WHERE r.USER_ID= E.USER_ID AND r.role_id = E.role_id AND r.ACTIVE = 4 AND E.effective_to_date <= (SELECT MAX(last_update_date) FROM CMP_USER_ROLE S WHERE S.role_id = r.role_id AND S.role_id = r.role_id AND S.ACTIVE = 4 )) Explain plan ----------------------------------------------------------------------------------------------------- | Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time | ----------------------------------------------------------------------------------------------------- | 0 | SELECT STATEMENT | | 1 | 37 | 154 (2)| 00:00:02 | |* 1 | FILTER | | | | | | |* 2 | TABLE ACCESS BY INDEX ROWID | USER_ROLE | 1 | 37 | 30 (0)| 00:00:01 | |* 3 | INDEX RANGE SCAN | N_USER_ROLE_IDX6 | 27 | | 3 (0)| 00:00:01 | |* 4 | FILTER | | | | | | | 5 | HASH GROUP BY | | 1 | 47 | 124 (2)| 00:00:02 | |* 6 | TABLE ACCESS BY INDEX ROWID | USER_ROLE | 159 | 3339 | 119 (1)| 00:00:02 | | 7 | NESTED LOOPS | | 11 | 517 | 123 (1)| 00:00:02 | |* 8 | TABLE ACCESS BY INDEX ROWID| USER_ROLE | 1 | 26 | 4 (0)| 00:00:01 | |* 9 | INDEX RANGE SCAN | N_USER_ROLE_IDX5 | 1 | | 3 (0)| 00:00:01 | |* 10 | INDEX RANGE SCAN | N_USER_ROLE_IDX2 | 957 | | 74 (2)| 00:00:01 | -----------------------------------------------------------------------------------------------------

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  • Securing database keys for client-side processing

    - by danp
    I have a tree of information which is sent to the client in a JSON object. In that object, I don't want to have raw IDs which are coming from the database. I thought of making a hash of the id and a field in the object (title, for example) or a salt, but I'm worried that this might have a serious effect on processing overhead. SELECT * FROM `things` where md5(concat(id,'some salt')) = md5('1some salt'); Is there a standard practice for obscuring IDs in this kind of situation?

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