mgo | 易学教程

Store Uploaded File in MongoDB GridFS Using mgo without Saving to Memory

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问题 noob Golang and Sinatra person here. I have hacked a Sinatra app to accept an uploaded file posted from an HTML form and save it to a hosted MongoDB database via GridFS. This seems to work fine. I am writing the same app in Golang using the mgo driver. Functionally it works fine. However in my Golang code, I read the file into memory and then write the file from memory to the MongoDB using mgo. This appears much slower than my equivalent Sinatra app. I get the sense that the interaction

Should I copy session for each operation in mgo?

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问题 I want to upsert a list of record, so I have two choice, one just use one session, another copy a session for every record. So, as my opinion, first method may slower than the second, but will the first one cause too many session created? 1.use one session func (this *CvStoreServiceImpl) SetCvJobItemMeasureList(accessToken *base_datatype.ServiceAccessToken, versionPolicy string, jobItemList []*cv_common_type.CvJobItemMeasure) (err error) { session := this.session.Clone() defer session.Close()

How can I use mongodb projections with Go and mgo?

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I am currently trying to extract a single object within a document array inside of mongodb. This is a sample dataset: "_id" : ObjectId("564aae61e0c4e5dddb07343b"), "name" : "The Races", "description" : "Horse races", "capacity" : 0, "open" : true, "type" : 0, "races" : [ { "_id" : ObjectId("564ab9097628ba2c6ec54423"), "race" : { "distance" : 3000, "user" : { "_id" : ObjectId("5648bdbe7628ba189e011b18"), "status" : 1, "lastName" : "Miranda", "firstName" : "Aramys" } } }, { "_id" : ObjectId("564ab9847628ba2c81f2f34a"), "bet" : { "distance" : 3000, "user" : { "_id" : ObjectId(

Parsing error in mongodb db, insert to collection with unique index

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I have a collection in mongodb with documents of the form: { "user": "user1", "email: "user1@example.com", } Where the fields "user" and "email" are unique. I want to insert a new user to the collection, while checking for uniqueness of both values. I can do an insert in golang with mgo like this: session.SetSafe(&mgo.Safe{}) // ensure mgo waits for errors user := struct{ string `bson:"user"` string `bson:"email"` }{ "user1", "user1@different.com" } err := users.Insert(user) // where user is type *mgo.Collection If I print err it outputs insertDocument :: caused by :: 11000 E11000 duplicate

Golang “Best practice” to handle connection to database

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I have a webservice written in Go and currently I have this Global package I import everywhere which contains the connection to MongoDB (via MGO), but I have to say that this feels very icky to me. What is the best practice of maintaining connections to datasources in Go? I come from a PHP world, hence the Global :S There is nothing wrong with importing a package which exports an initialized *mgo.Session object either as a package-level variable or through an accessor/initializer. Maybe the latter appeals better to classical "OOP-ists". 来源： https://stackoverflow.com/questions/23333753/golang

How do you select all records from a mongodb collection in golang using mgo

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问题 In MongoDB doing something like db.mycollection.find() returns all documents in a collection. When working in GoLang using the package labix.org/v2/mgo and I do for example: query := db.C("client").Find(); It complains that it requires input in the form of an interface. All I need to do is retrieve all documents and iterate through them and display each one for now. How do I achieve this effect? All examples I have seen seem to have filters in place. 回答1: Found a solution: var results [

Using golang and mgo, how do I search for a range of values in MongoDB?

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I worked through the example on the mgo homepage , but I'm struggling to find a way to query a range of values. The line: searchResults, searchErr = SearchReading(bson.M{"k": key, "t": { $gte: start, $lte: end } }, limit) fails with: line67: syntax error: unexpected $ line67: missing type in composite literal I left out the non-essential bits of code... type Reading struct { K string "k" T int64 "t" V float64 "v" } func SearchReading(q interface{}, limit int) (searchResults []Reading, searchErr string) { searchErr = "" searchResults = []Reading{} query := func(c *mgo.Collection) error { fn :=

How to represent an array with mixed types

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I am constructing an aggregation pipeline query with the $substr command from MongoDB but I don't know how to represent the array it requires in Go with the mgo driver because it contains different types of values (string, int). Here is the query in javascript: [ {$group: {"_id": {"dt": {"$substr": ["$dt",0,6]}}}} ] What this is trying to do is get the substring of dt (from the previous stage of aggregation) with starting index 0 and ending index 6. In Go i got: []bson.M{"$group": bson.M{"_id": bson.M{"dt": bson.M{"$substr": ["$dt",0,6]}}}}} but ["$dt",0,6] is not a correct representation and

How to use interface type as a model in mgo (Go)?

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问题 Suppose you have a workflow that consists of multiple embedded nodes of different types. Since nodes are of different types, I thought of using Golang interfaces here and came up with following: type Workflow struct { CreatedAt time.Time StartedAt time.Time CreatedBy string Nodes []Node } type Node interface { Exec() (int, error) } type EmailNode struct { From string To string Subject string Body string } type TwitterNode struct { Tweet string Image []byte } func (n *EmailNode) Exec() (int,

【翻译】使用Golang+MongoDB构建微服务

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原创文章，转载请注明：转载自勤奋的小青蛙本文链接地址: 【翻译】使用Golang+MongoDB构建微服务翻译来源： http://goinbigdata.com/how-to-build-microservice-with-mongodb-in-golang/ 参考链接： mgo驱动官网现在golang成为热门的微服务(RESTFul API)开发语言之一。通常，这些微服务系统采用了MongoDB作为数据库。在这篇博客里，我们将构建一个简单的图书管理微服务，采用Golang + MongoDB来完成该微服务。我们将使用 mgo 来完成Golang与MongoDB的交互。 MongoDB MongoDB简单，高可用性，并且是文档类型的数据库，也就是我们常说的 NoSQL 数据库。相比 SQL 型的数据库，它的优势有： mongodb的文档对象结构对应了诸多编程语言的数据结构；组合式的文档结构减少了昂贵的join连接开销；文档动态支持各种各样数据类型的结构，一个集合中可以存在各种各样不同数据类型字段的文档。什么是文档（document）文档只是一个由字段和值对组成的数据结构。字段的值可能包括其他文档，数组和文档数组。MongoDB文档类似于JSON对象，每个文档都作为一个记录存储在MongoDB集合中。例如，一本书可以表示为以下文档（json）： { "isbn":