mongodb

问题 I've been able to successfully write binary data (an image) to MongoDB in Node.js. However I can't find clear documentation on how to read it back. Here's how I'm writing the image to MongoDB: var imageFile = req.files.myFile; var imageData = fs.readFileSync(imageFile.path); var imageBson = {}; imageBson.image = new db.bson_serializer.Binary(imageData); imageBson.imageType = imageFile.type; db.collection('images').insert(imageBson, {safe: true},function(err, data) { I'd appreciate any

问题 I use the latest version of MongoDB database and the latest version of the official JAVA MongoDB driver. The dependencies that I use in my pom.xml: <properties> <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding> <maven.compiler.source>1.7</maven.compiler.source> <maven.compiler.target>1.7</maven.compiler.target> ... <jersey.container.version>2.13</jersey.container.version> <jackson.version>2.4.3</jackson.version> <genson.version>1.1</genson.version> <jongo.version>1.1</jongo

问题 I use the latest version of MongoDB database and the latest version of the official JAVA MongoDB driver. The dependencies that I use in my pom.xml: <properties> <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding> <maven.compiler.source>1.7</maven.compiler.source> <maven.compiler.target>1.7</maven.compiler.target> ... <jersey.container.version>2.13</jersey.container.version> <jackson.version>2.4.3</jackson.version> <genson.version>1.1</genson.version> <jongo.version>1.1</jongo

问题 I have a schema: var s = new Schema({ links: { type: [Url] } }); In this case I am using the url schema type from https://github.com/bnoguchi/mongoose-types - but I have tried this with other types. Mongoose doesn't seem to validate/use the schema type when in an array - works fine without the array. How can I define an array of schema types that will validate? 回答1: Answer from Mongoose creator: "Unless the Url is a subdocument, validation will not get triggered currently (there is a ticket

问题 I have a schema: var s = new Schema({ links: { type: [Url] } }); In this case I am using the url schema type from https://github.com/bnoguchi/mongoose-types - but I have tried this with other types. Mongoose doesn't seem to validate/use the schema type when in an array - works fine without the array. How can I define an array of schema types that will validate? 回答1: Answer from Mongoose creator: "Unless the Url is a subdocument, validation will not get triggered currently (there is a ticket

问题 I have an aggregation query as follows : db.TWITTER_DATA_Processed.aggregate( {$match : { SpId : 840, Scheduler_id : "SCH_01" }},{$group : {_id : {SpId : "$SpId", Scheduler_id : "$Scheduler_id",Country : "$Country"}, positive_count : { $sum: { $cond: [ { $gt: [ "$Sentiment", 0 ] } , 1, 0 ] } }, neutral_count : { $sum: { $cond: [ { $eq: [ "$Sentiment", 0 ] } , 1, 0 ] } }, negative_count : { $sum: { $cond: [ { $lt: [ "$Sentiment", 0 ] } , 1, 0 ] } }}}) Sample output : { "_id" : { "SpId" : 840,

问题 I want to export mongodb as json, here is a record: {"_id":{"$oid":"554f042c0e81bf483e4a4e2f"}, "batch":"3","bz":NumberInt(1)} the problems is when I use json to loads it: json.loads('{"_id":{"$oid":"554f042c0e81bf483e4a4e2f"}, "batch":"3","bz":NumberInt(1)}') it returns ValueError: No JSON object could be decoded . This is because json can not deal with NumberInt(1) . So how can I translate NumberInt(1) to 1 when I export? 回答1: [UPDATE] IF your mongo collection does not include NumberInt,

问题 I want to export mongodb as json, here is a record: {"_id":{"$oid":"554f042c0e81bf483e4a4e2f"}, "batch":"3","bz":NumberInt(1)} the problems is when I use json to loads it: json.loads('{"_id":{"$oid":"554f042c0e81bf483e4a4e2f"}, "batch":"3","bz":NumberInt(1)}') it returns ValueError: No JSON object could be decoded . This is because json can not deal with NumberInt(1) . So how can I translate NumberInt(1) to 1 when I export? 回答1: [UPDATE] IF your mongo collection does not include NumberInt,

问题 I'm wondering if it's possible to create a table dynamically in mongodb using a Mongoose schema, Node.js and Angular for example. The basic way to make a schema is to create a model explicitly in Node.js like this: import mongoose from 'mongoose'; const Schema = mongoose.Schema; const postSchema = new Schema({ title: { type: 'String', required: true }, content: { type: 'String', required: true }, slug: { type: 'String', required: true } }); let Post = mongoose.model('Post', postSchema); Is it

问题 Basically I have a quite simple questions, but I was not able to find the answer in the MongoDB documentation or using Google. What I want to know is, whether there is a upper limit of how big a MongoDB based GridFS may become? (I know that the default maximum file size is 16 MByte, and that you can exceed this limit by using GridFS. But what is the upper limit for all files in GridFS?) 回答1: MongoDB uses the operating system's mmapped IO as storage engine. The theoretical maximum, if there