nosql

问题 I have been reading documentation and watching screencasts specific to Mongo DB over the past few days and I am at a loss for when a solution like this would be better than a typical pg or mysql environment. Specifically, my question is under what circumstance (w/ use case would be nice) would you want to go the nosql route? Thanks! 回答1: Many disparate writers. Especially when the writers can get segmented due to disconnections in the network, and will later need to resync data that has been

问题 As it currently stands, this question is not a good fit for our Q&A format. We expect answers to be supported by facts, references, or expertise, but this question will likely solicit debate, arguments, polling, or extended discussion. If you feel that this question can be improved and possibly reopened, visit the help center for guidance. Closed 8 years ago . Recently I watched some old Oredev presentation on NoSql databases. I learned a bit but I still don't know when these databases are

问题 I want to use amazon Dynamo DB with rails.But I have not found a way to implement pagination. I will use AWS::Record::HashModel as ORM. This ORM supports limits like this: People.limit(10).each {|person| ... } But I could not figured out how to implement following MySql query in Dynamo DB. SELECT * FROM `People` LIMIT 1 , 30 回答1: You issue queries using LIMIT. If the subset returned does not contain the full table, a "LastEvaluatedKey" value is returned. You use this value as the

问题 Closed . This question is opinion-based. It is not currently accepting answers. Want to improve this question? Update the question so it can be answered with facts and citations by editing this post. Closed last year . I am considering MongoDB to hold metadata of images, recorded from 100 cameras, and the records will be kept for 30 days for each camera. If one camera gives 100,000 images in a day then i am going to save ( 100 x 30 x 100000 ) images (documents) at max in MongoDB. My web

问题 Closed . This question is opinion-based. It is not currently accepting answers. Want to improve this question? Update the question so it can be answered with facts and citations by editing this post. Closed last year . I am considering MongoDB to hold metadata of images, recorded from 100 cameras, and the records will be kept for 30 days for each camera. If one camera gives 100,000 images in a day then i am going to save ( 100 x 30 x 100000 ) images (documents) at max in MongoDB. My web

问题 I have no experience dealing with nosql databases such as Amazon AWS DynamoDB. I have some data stored in Amazon AWS DynamoDB. Is it possible to export data from DynamoDB to MySQL Server ? If so, how to go about accomplishing that ? Thanks, 回答1: I would extract the data in CSV format. This "DynamoDBtoCSV" tool seems promising. Then you can import this CSV file into your MySQL database with LOAD DATA INFILE. The drawback is that you 1. need to create the receiving structure first and 2. repeat

问题 Is it possible to do SQL inner joins kind of stuff in MongoDB , well i know there is $lookup attribute in aggregation pipeline and it is equivalent to outer joins in SQL but i want to do a similar kind of a task as in inner joins , i have two three collections ,which i need to merge together ----User Collection---- db.User.find({}) { ID : 1, USER_NAME : "John", password : "pass" } { ID : 2, USER_NAME : "Andrew", PASSWORD : "andrew" } ---ROLE COLLECTION--- db.ROLE.find({}) { ID : 1, ROLE_NAME

问题 I'm writing a web application using PHP/Symfony2/Doctrine2 and just finishing up the design of the Database. We have to import these objects (for ex. Projects, Vendors) into our database that come from different customers with variety of fields. Some customers have 2 fields in the project object and some have 20. So I was thinking about implementing them in MongoDB since it seems like a good use for it. Symfony2 supports both ORM and ODM so that shouldn't be a problem, Now my question is how

问题 " Make things as simple as possible, but no simpler. " Can we find the solution/s that fix the Python database world? Update: A 'lustdb' prototype has been written by Alex Martelli - if you know any somewhat lightweight, high-level database libraries with multiple backends we could wrap in syntax sugar honey, please weigh in! from someAmazingDB import * #we imported a smart model class and db object which talk to database adapter/s class Task (model): title = '' done = False #native types not

问题 I'm still learning my lessons about data modeling in bigtable/nosql and would appreciate some feedback. Would it be fair to say that I should avoid parent->child relationships in my data modeling if I frequently need to deal with the children in aggregate across parents? As an example, let's say I'm building a blog that will be contributed to by a number of authors, and each other has posts, and each post has tags. So I could potentially set up something like this: class Author(db.Model):