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• how to have separate keys per record in mongo_mapper + Rails

  - by Vitaly Kushner

  When I'm adding a record in mongodb I can specify whatever keys I want and it will store it in the db. The problem is that it will remember those keys for the next time I insert another record. so for example if I do the following: Product.create :foo => 123 and then Product.create :bar => 456 I get :foo => nil field in the 2nd record. This is definitely not a limitation of mongodb itself, since if I restart the rails console and create yet another record with different set of columns, it will not add the columns from the 1st 2 records. So it seems like mongomapper remembers all the keys used and inserts them all into all records, even if values are not provided. The question is obviously: how do I disable this crazy attributes explosion? Basically I want only the 'permanent' keys that I specify in the model to be in every record, but all the 'extra' attributes to be specified per record and not to mess the consequent records.

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• how to test if a string is a valid UTF16 string?

  - by superb

  I am using mongodb and javascript to do some string processing. Now I got some error like: Sun May 23 07:42:20 Assertion failure JS_EncodeCharacters( _context , s , srclen , dst , &len) scripting/engine_spidermonkey.cpp 152 0x80f4f7e 0x80f8794 0x811525b 0x811a953 0x8119fc4 0x8111bc5 0x81b408e 0x81c4ee7 0x81b4a10 0x817a881 0x817a7d8 0x817a6e2 0x811e1bb 0x80a777b 0x80a8f8a 0xb7cb2455 0x80a37a1 mongodb-linux-i686-1.4.2/bin/mongo(_ZN5mongo12sayDbContextEPKc+0xfe) [0x80f4f7e] After doing some google, I find that JS_EncodeCharacters return false if the input is not a valid UTF16 string. (if spidermonkey is build with UTF-8 enabled) So I was wondering how to test if the input string if a proper UTF16 string? so I can skip such kind of string to avoid problem ... Thanks

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• Scala case class generated field value

  - by Petteri Hietavirta

  I have an existing Scala application and it uses case classes which are then persisted in MongoDB. I need to introduce a new field to a case class but the value of it is derived from existing field. For example, there is phone number and I want to add normalised phone number while keeping the original phone number. I'll update the existing records in MongoDB but I would need to add this normalisation feature to existing save and update code. So, is there any nice shortcut in Scala to add a "hook" to a certain field of a case class? For example, in Java one could modify setter of the phone number.

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• Is shortening properties names worth it?

  - by raam86

  in how to node Blog rolling with node.js and mongoDB the author mentions it's a good idea to shorten proprieties names: ....oft-reported issue with mongoDB is the size of the data on the disk... each and every record stores all the field-names .... This means that it can often be more space-efficient to have properties such as 't', or 'b' rather than 'title' or 'body', however for fear of confusion I would avoid this unless truly required! I am aware of solutions of how to do it I am more intrested in when is it truly required?

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• Understanding NoSQL Data Modeling - blog application

  - by Rushabh RajeshKumar Padalia

  I am creating an blogging application in Node.js + MongoDB Database. I have used relational Database like MySQL before but this is my first experience with NoSQL database. So I would like to conform my MongoDB data models before I move further. I have decided my blogDB to have 3 collections post_collection - stores information about that article comment_collection - store information about comments on articles user_info_collection - contains user inforamtion PostDB { _"id" : ObjectID(...), "author": "author_name", "Date": new Date(....), "tag" : ["politics" , "war"], "post_title": "My first Article", "post_content": "Big big article" "likes": 23 "access": "public" } CommentDB { "_id" : Objectid(...), "POST": "My First Article", "comment_by": "User_name", "comment": "MY comments" } UserInfoDB { "_id": ObjectID(...), "user": "User_name", "password": "My_password" } I would appreciate your comments.

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• Why is Javascript used in MongoDB and CouchDB instead of other languages such as Java, C++?

  - by startup007

  I asked this question on SO but was suggested to try here. So here it goes: My understanding of Javascript so far has been that it is a client-side language that capture events and makes a web-page dynamic. But on reading the comparison between MongoDB and CouchDB I noticed that both are using Javascript. This makes me wonder the reason behind the choice of JavaScript over other conventional languages. I guess I am trying to understand the role of JavaScript and its advantages over other languages. Update: I am not asking about the languages / drivers supported by the two databases. The comparison says: Both CouchDB and MongoDB make use of Javascript. CouchDB uses Javascript extensively including in the building of views. MongoDB also supports running arbitrary javascript functions server-side and uses javascript for map/reduce operations. My lack of understanding pertains to why is Javascript being used at all for the backend work. Why is it preferred for building views in CouchDB, or for using map/reduce operations? Why C/C++ or Java were not used? What are the advantages in using Javascript for such back-end work?

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• Using map/reduce for mapping the properties in a collection

  - by And

  Update: follow-up to MongoDB Get names of all keys in collection. As pointed out by Kristina, one can use Mongodb 's map/reduce to list the keys in a collection: db.things.insert( { type : ['dog', 'cat'] } ); db.things.insert( { egg : ['cat'] } ); db.things.insert( { type : [] }); db.things.insert( { hello : [] } ); mr = db.runCommand({"mapreduce" : "things", "map" : function() { for (var key in this) { emit(key, null); } }, "reduce" : function(key, stuff) { return null; }}) db[mr.result].distinct("_id") //output: [ "_id", "egg", "hello", "type" ] As long as we want to get only the keys located at the first level of depth, this works fine. However, it will fail retrieving those keys that are located at deeper levels. If we add a new record: db.things.insert({foo: {bar: {baaar: true}}}) And we run again the map-reduce +distinct snippet above, we will get: [ "_id", "egg", "foo", "hello", "type" ] But we will not get the bar and the baaar keys, which are nested down in the data structure. The question is: how do I retrieve all keys, no matter their level of depth? Ideally, I would actually like the script to walk down to all level of depth, producing an output such as: ["_id","egg","foo","foo.bar","foo.bar.baaar","hello","type"] Thank you in advance!

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• getting data from dynamic schema

  - by coure2011

  I am using mongoose/nodejs to get data as json from mongodb. For using mongoose I need to define schema first like this var mongoose = require('mongoose'); var Schema = mongoose.Schema; var GPSDataSchema = new Schema({ createdAt: { type: Date, default: Date.now } ,speed: {type: String, trim: true} ,battery: { type: String, trim: true } }); var GPSData = mongoose.model('GPSData', GPSDataSchema); mongoose.connect('mongodb://localhost/gpsdatabase'); var db = mongoose.connection; db.on('open', function() { console.log('DB Started'); }); then in code I can get data from db like GPSData.find({"createdAt" : { $gte : dateStr, $lte: nextDate }}, function(err, data) { res.writeHead(200, { "Content-Type": "application/json", "Access-Control-Allow-Origin": "*" }); var body = JSON.stringify(data); res.end(body); }); How to define scheme for a complex data like this, you can see that subSection can go to any deeper level. [ { 'title': 'Some Title', 'subSection': [{ 'title': 'Inner1', 'subSection': [ {'titile': 'test', 'url': 'ab/cd'} ] }] }, .. ]

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• encapsulation in python list (want to use " instead of ')

  - by Codehai

  I have a list of users users["pirates"] and they're stored in the format ['pirate1','pirate2']. If I hand the list over to a def and query for it in MongoDB, it returns data based on the first index (e.g. pirate1) only. If I hand over a list in the format ["pirate1","pirate"], it returns data based on all the elements in the list. So I think there's something wrong with the encapsulation of the elements in the list. My question: can I change the encapsulation from ' to " without replacing every ' on every element with a loop manually? Short Example: aList = list() # get pirate Stuff # users["pirates"] is a list returned by a former query # so e.g. users["pirates"][0] may be peter without any quotes for pirate in users["pirates"]: aList.append(pirate) aVar = pirateDef(aList) print(aVar) the definition: def pirateDef(inputList = list()): # prepare query col = mongoConnect().MYCOL # query for pirates Arrrr pirates = col.find({ "_id" : {"$in" : inputList}} ).sort("_id",1).limit(50) # loop over users userList = list() for person in pirates: # do stuff that has nothing to do with the problem # append user to userlist userList.append(person) return userList If the given list has ' encapsulation it returns: 'pirates': [{'pirate': 'Arrr', '_id': 'blabla'}] If capsulated with " it returns: 'pirates' : [{'_id': 'blabla', 'pirate' : 'Arrr'}, {'_id': 'blabla2', 'pirate' : 'cheers'}] EDIT: I tried figuring out, that the problem has to be in the MongoDB query. The list is handed over to the Def correctly, but after querying pirates only consists of 1 element... Thanks for helping me Codehai

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• checking mongo database for data

  - by user1647484

  I'm playing around with this tutorial that uses Sinatra, backbone.js, and mongodb for the database. It's my first time using mongo. As far as I understand it the app uses both local storage and a database. it has these routes for the database. For example, it has these routes get '/api/:thing' do DB.collection(params[:thing]).find.to_a.map{|t| from_bson_id(t)}.to_json end get '/api/:thing/:id' do from_bson_id(DB.collection(params[:thing]).find_one(to_bson_id(params[:id]))).to_json end post '/api/:thing' do oid = DB.collection(params[:thing]).insert(JSON.parse(request.body.read.to_s)) "{\"_id\": \"#{oid.to_s}\"}" end After turning the server off and then on, I could see in the server getting data from the database routes 127.0.0.1 - - [17/Sep/2012 08:21:58] "GET /api/todos HTTP/1.1" 200 430 0.0033 My question is, how can I check from within the mongo shell whether the data's in the database? I started the mongo shell ./bin/mongo I selected the database 'use mydb' and then looking at the docs (http://www.mongodb.org/display/DOCS/Tutorial) I tried commands such as > var cursor = db.things.find(); > while (cursor.hasNext()) printjson(cursor.next()); but they didn't return anything.

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• new project app; use entirely node.js

  - by Jared

  I have been looking into Node.js, express and Nowjs and love how easy it is to have real time interactions between clients. My background is mostly from CodeIgniter MVC using PHP and MYSql. I want to re make a current web project of mine from scratch to make everything better and more real time with this newer technology. After researching and doing test examples I want to use node.js , express and Nowjs for the real time interactions once someone connects to the socket.io to pull data back to clients. But use Code Igniter for the control of the site and user management , possible shopping cart/store , pretty much everything else. This is purely due to time constraints and that I am already familiar with doing it that way. I have been looking at MongoDB as an alternative to MySql, Basically the app is going to be multiple chat rooms all on one page. with the ability of notifications and private messaging. Lots of data transfer and images. before I started piecing it together I wanted to get people who have already done something similar. My model would use Code Igniter and MySQL to render the page and then connect them onto a node.js server and broadcast using express and nowjs would using a mongoDB be better than mySQL for tons of messages and data being stored or MYSQL? Also does it make since to not make the whole site on Node.js , kinda piece it together like that?

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• MongoMapper and migrations

  - by Clint Miller

  I'm building a Rails application using MongoDB as the back-end and MongoMapper as the ORM tool. Suppose in version 1, I define the following model: class SomeModel include MongoMapper::Document key :some_key, String end Later in version 2, I realize that I need a new required key on the model. So, in version 2, SomeModel now looks like this: class SomeModel include MongoMapper::Document key :some_key, String key :some_new_key, String, :required => true end How do I migrate all my existing data to include some_new_key? Assume that I know how to set a reasonable default value for all the existing documents. Taking this a step further, suppose that in version 3, I realize that I really don't need some_key at all. So, now the model looks like this class SomeModel include MongoMapper::Document key :some_new_key, String, :required => true end But all the existing records in my database have values set for some_key, and it's just wasting space at this point. How do I reclaim that space? With ActiveRecord, I would have just created migrations to add the initial values of some_new_key (in the version1 - version2 migration) and to delete the values for some_key (in the version2 - version3 migration). What's the appropriate way to do this with MongoDB/MongoMapper? It seems to me that some method of tracking which migrations have been run is still necessary. Does such a thing exist? EDITED: I think people are missing the point of my question. There are times where you want to be able to run a script on a database to change or restructure the data in it. I gave two examples above, one where a new required key was added and one where a key can be removed and space can be reclaimed. How do you manage running these scripts? ActiveRecord migrations give you an easy way to run these scripts and to determine what scripts have already been run and what scripts have not been run. I can obviously write a Mongo script that does any update on the database, but what I'm looking for is a framework like migrations that lets me track which upgrade scripts have already been run.

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• NoSQL DB for .Net document-based database (ECM)

  - by Dane

  I'm halfway through coding a basic multi-tenant SaaS ECM solution. Each client has it's own instance of the database / datastore, but the .Net app is single instance. The documents are pretty much read only (i.e. an image archive of tiffs or PDFs) I've used MSSQL so far, but then started thinking this might be viable in a NoSQL DB (e.g. MongoDB, CouchDB). The basic premise is that it stores documents, each with their own particular indexes. Each tenant can have multiple document types. e.g. One tenant might have an invoice type, which has Customer ID, Invoice Number and Invoice Date. Another tenant might have an application form, which has Member Number, Application Number, Member Name, and Application Date. So far I've used the old method which Sharepoint (used?) to use, and created a document table which has int_field_1, int_field_2, date_field_1, date_field_2, etc. Then, I've got a "mapping" table which stores the customer specific index name, and the database field that will map to. I've avoided the key-value pair model in the DB due to volume of documents. This way, we can support multiple document types in the one table, and get reasonably high performance out of it, and allow for custom document type searches (i.e. user selects a document type, then they're presented with a list of search fields). However, a NoSQL DB might make this a lot simpler, as I don't need to worry about denormalizing the document. However, I've just got concerns about the rest of the data around a document. We store an "action history" against the document. This tracks views, whether someone emails the document from within the system, and other "future" functionality (e.g. faxing). We have control over the document load process, so we can manipulate the data however it needs to be to get it in the document store (e.g. assign unique IDs). Users will not be adding in their own documents, so we shouldn't need to worry about ACID compliance, as the documents are relatively static. So, my questions I guess : Is a NoSQL DB a good fit Is MongoDB the best for Asp.Net (I saw Raven and Velocity, but they're still kinda beta) Can I store a key for each document, and then store the action history in a MSSQL DB with this key? I don't need to do joins, it would be if a person clicks "View History" against a document. How would performance compare between the two (NoSQL DB vs denormalized "document" table) Volumes would be up to 200,000 new documents per month for a single tenant. My current scaling plan with the SQL DB involves moving the SQL DB into a cluster when certain thresholds are reached, and then reviewing partitioning and indexing structures.

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• Use cases for NoSQL

  - by seengee

  NoSQL has been getting a lot of attention in the industry recently. Really interested in peoples thoughts on the best use-cases for its use over relational database storage. What should trigger a developer into thinking that particular datasets are more suited to a NoSQL solution like Redis/CouchDB/MongoDB/Cassandra etc. Would also be really interested to hear what people have ported from relational db's to NoSQL and what improvements they have seen.

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• Clojure and NoSQL databases

  - by Mad Wombat

  I am currently trying to pick between different NoSQL databases for my project. The project is being written in clojure and javascript. I am currently looking at three candidates for storage. What are the relative strengths and weaknesses of MongoDB, FleetDB and CouchDB? Which one is better supported in Clojure? Which one is better supported under Linux? Did I miss a better product (has to be free and OSS)?

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• How to stream image object in Sinatra

  - by Prakash

  I had uploaded images to mongoDB using GridFS. I want to retrieve an image from the db and display it in the browser. How to do this with the help of Sinatra and HAML.

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• TG2.1: Proper location to store a database session instance?

  - by Lee Olayvar

  I am using a custom database (MongoDB) with TG 2.1 and i am wondering where the proper place to store the PyMongo connection/database instances would be? Eg, at the moment they are getting created inside of my inherited instance of AppConfig. Is there a standard location to store this? Would shoving the variables into the project.model.__init__ be the best location, given that under SQLAlchemy, the database seems to commonly be retrieved via: from project.model import DBSession, metadata Anyway, just curious what the best practice is.

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• Exception in morphia-0.93-SNAPSHOT.jar

  - by Rupeshit

  Hi guys, I am trying to mapp pojo class to mongodb using morphia-0.93-SNAPSHOT.jar but it is throwing exception that "java.lang.NoClassDefFoundError: org/bson/types/CodeWScope" which is bson's exception.So I am not able to run those programs.So please can anybody help me to solved this problem

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• Grails Domain.get() returns null for mongo's ObjectId

  - by Shashank Agrawal

  I'm using grails 2.3.5 with mongodb 3.0.1 and no hibernate installed. I've a domain class which uses mongo's ObjectId. import org.bson.types.ObjectId class Category { ObjectId id String name } And has a record in mongo database: { "_id": ObjectId("53f6c34c33a429240e2ab471"), "name": "art", "version": NumberLong("41") } When I do, Category.get(new ObjectId("53f6c34c33a429240e2ab471")) somewhere in grails app, it returns null but when I do Category.get("53f6c34c33a429240e2ab471") it then actually returns the result. Why, get() method does not process ObjectId type?

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• Directory Hierarchy

  - by niveditha

  How to build a folder structure using morphia or the mongodb API? I am looking for something like this. folderA --->folderB --->folderC ------>fileC ------>folderCA ---------->fileCA

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• how get validation messages from mangomapper using rails console ?

  - by Alex

  Hi, I am basically teaching myself how to use RoR and MongoDB at the same time. I am following the very good book / tutorial : http://railstutorial.org/ I decided to replace Sqlite3 by MongoDB using the mongomapper gem. Everything works out about alright, but I am having some non-blocking little issues that I truly wish I could get rid of. In chapter 6, when working with validation I got 2 issues: - I don't know how to get the validations messages back like with Sqlite3. The "standard" code is: $ rails console --sandbox >> user = User.new(:name => "", :email => "[email protected]") >> user.save => false >> user.valid? => false >> user.errors.full_messages => ["Name can't be blank"] but if I try to do the same with MongoMapper, it throws an error saying that errors is undefined function. So does it mean that this is simply not implemented in mongomapper / mongo driver ? Or is there some other clever way to do this that I could not figure ? Additional, 2 things here: - I following the exemple in the book to the line, so I was expecting to be able to use the console in sandbox mode, but apparently that does not work either: (...)ruby-1.9.2-p136@rails3/gems/railties-3.0.3/lib/rails/console/sandbox.rb:1:in `<top (required)>': uninitialized constant ActiveRecord (NameError) from /Users/Alex/.rvm/gems/ruby-1.9.2-p136@rails3/gems/railties-3.0.3/lib/rails/application.rb:226:in `initialize_console' from /Users/Alex/.rvm/gems/ruby-1.9.2-p136@rails3/gems/railties-3.0.3/lib/rails/application.rb:153:in `load_console' from /Users/Alex/.rvm/gems/ruby-1.9.2-p136@rails3/gems/railties-3.0.3/lib/rails/commands/console.rb:26:in `start' from /Users/Alex/.rvm/gems/ruby-1.9.2-p136@rails3/gems/railties-3.0.3/lib/rails/commands/console.rb:8:in `start' from /Users/Alex/.rvm/gems/ruby-1.9.2-p136@rails3/gems/railties-3.0.3/lib/rails/commands.rb:23:in `<top (required)>' from script/rails:6:in `require' from script/rails:6:in `<main>' Also, in the book they call "user" but I need to call "User" (note the capital U) why is that ? Is it like mangomapper does not follow the Ruby naming convention or something ? And finally, I am trying to validate the field email with a regex as shown in the tutorial. It does not throws any errors at the code, but whenever I try to insert it just won't ever accept it unless I comment out the :format option... class User include MongoMapper::Document key :name, String, :required => true, :length => { :maximum => 50 } key :email, String, :required => true, # :format => { :with => email_regex }, :uniqueness => { :case_sentitive => false} timestamps! end Any advices you can provide on those topics would help me a lot ! Thanks, Alex

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• Drop in solution for logging to DB

  - by Jake

  I'm considering setting up our servers to log to a Mongo Database rather than log files. Logs will then be all on one server, queryable, and overall easier to manage. I'd love to find a solution that will allow all the different processes I have running to write to DB rather than files (or perhaps something to read the files, pass the logs on and truncate the files). I don't want to have to find a different solution for every process if I can avoid it. So, does anyone know of an existing solution to this problem?

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• mongoexport csv output array values

  - by 9point6

  I'm using mongoexport to export some collections into CSV files, however when I try to target fields which are members of an array I cannot get it to export correctly. command I'm using: mongoexport -d db -c collection -fieldFile fields.txt --csv > out.csv and the contents of fields.txt is similar to id name address[0].line1 address[0].line2 address[0].city address[0].country address[0].postcode where the BSON data would be: { "id": 1, "name": "example", "address": [ { "line1": "flat 123", "line2": "123 Fake St.", "city": "London", "country": "England", "postcode": "N1 1AA" } ] } what is the correct syntax for exporting the contents of an array?

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• Understanding mongod log entries

  - by Jo Erlang

  Can anyone explain the numbers in the % column, in this mongod log snippet ? It is building a new index but I'm not sure I understand why the numbers look like that Tue Nov 20 11:38:08 [initandlisten] connection accepted from 127.0.0.1:49299 #8 (2 connections now open) Tue Nov 20 11:38:08 [conn8] build index xx.yyyy { source: 1 } Tue Nov 20 11:38:19 [conn8] 2921300/243339 1200% Tue Nov 20 11:38:29 [conn8] 4109600/243339 1688% Tue Nov 20 11:38:39 [conn8] 4400100/243339 1808% Tue Nov 20 11:38:49 [conn8] 4676600/243339 1921% Tue Nov 20 11:38:59 [conn8] 4939700/243339 2029% Tue Nov 20 11:39:09 [conn8] 5217800/243339 2144% Tue Nov 20 11:39:19 [conn8] 5439300/243339 2235% Tue Nov 20 11:39:29 [conn8] 5659700/243339 2325% Thanks

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• Database OR Array

  - by rezoner

  What is the exact point of using external database system if I have simple relations (95% querries are dependant on ID). I am storing users and their stats. Why would I use external database if I can have neat constructions like: db.users[32] = something Array of 500K users is not that big effort for RAM Pros are: no problematic asynchronity (instant results) easy export/import dealing with database like with a native object LITERALLY ps. and considerations: Would it be faster or slower to do collection[3] than db.query("select ... I am going to store it as a file/s There is only ONE application/process accessing this data, and the code is executed line by line - please don't elaborate about locking. Please don't answer with database propositions but why to use external DB over native array/object - I have experience in a few databases - that's not the case. What I am building is a client/gateway/server(s) game. Gateway deals with all users data, processing, authenticating, writing statistics e.t.c No other part of software needs to access directly to this data/database.

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