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Questions tagged [nosql]

NoSQL (sometimes expanded to "not only SQL") is a broad class of database management systems that differ from the classic model of the relational database management system (RDBMS) in some significant ways.

NoSQL (sometimes expanded to "not only ") is a broad class of database management systems that differ from the classic model of the relational database management system () in some significant ways.

NoSQL systems:

  • Specifically designed for high load
  • Natively support horizontal scalability
  • Fault-tolerant
  • Store data in a denormalized manner
  • Do not usually enforce strict database schema
  • Do not usually store data in a table
  • Sometimes provide eventual consistency instead of ACID transactions

In contrast to RDBMS, NoSQL systems:

  • Do not guarantee data consistency
  • Usually support a limited query language (a subset of SQL or another custom query language)
  • May not provide support for transactions/distributed transactions
  • Do not usually use some advanced concepts of RDBMS, such as triggers, views, stored procedures

NoSQL implementations can be categorized by their manner of implementation:

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Amazon SimpleDB vs Amazon DynamoDB

I have some basic understanding what Amazon SimpleDB is, but according to the Amazon DynamoDB description it seems to be almost the same: a NoSQL Key-value store service. Can someone simply explain the main differences between them and tell in which…
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When NOT to use Cassandra?

There has been a lot of talk related to Cassandra lately. Twitter, Digg, Facebook, etc all use it. When does it make sense to: use Cassandra, not use Cassandra, and use a RDMS instead of Cassandra.
JimJim
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Possibility of duplicate Mongo ObjectId's being generated in two different collections?

Is it possible for the same exact Mongo ObjectId to be generated for a document in two different collections? I realize that it's definitely very unlikely, but is it possible? Without getting too specific, the reason I ask is that with an…
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What is BSON and exactly how is it different from JSON?

I am just starting out with MongoDB and one of the things that I have noticed is that it uses BSON to store data internally. However the documentation is not exactly clear on what BSON is and how it is used in MongoDB. Can someone explain it to me,…
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How to empty a redis database?

I've been playing with redis (and add some fun with it) during the last fews days and I'd like to know if there is a way to empty the db (remove the sets, the existing key....) easily. During my tests, I created several sets with a lot of members,…
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Storing time-series data, relational or non?

I am creating a system which polls devices for data on varying metrics such as CPU utilisation, disk utilisation, temperature etc. at (probably) 5 minute intervals using SNMP. The ultimate goal is to provide visualisations to a user of the system in…
Marcus Whybrow
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MongoDB: How to update multiple documents with a single command?

I was surprised to find that the following example code only updates a single document: > db.test.save({"_id":1, "foo":"bar"}); > db.test.save({"_id":2, "foo":"bar"}); > db.test.update({"foo":"bar"}, {"$set":{"test":"success!"}}); >…
Luke Dennis
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DynamoDB vs MongoDB NoSQL

I'm trying to figure out what can I use for a future project, we plan to store about 500k records per month in the first year and maybe more for the next years this is a vertical application so there's no need to use a database for this, that's the…
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What scalability problems have you encountered using a NoSQL data store?

NoSQL refers to non-relational data stores that break with the history of relational databases and ACID guarantees. Popular open source NoSQL data stores include: Cassandra (tabular, written in Java, used by Cisco, WebEx, Digg, Facebook, IBM,…
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Is there any NoSQL data store that is ACID compliant?

Is there any NoSQL data store that is ACID compliant?
JustinT
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MongoDB/NoSQL: Keeping Document Change History

A fairly common requirement in database applications is to track changes to one or more specific entities in a database. I've heard this called row versioning, a log table or a history table (I'm sure there are other names for it). There are a…
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What is NoSQL, how does it work, and what benefits does it provide?

I've been hearing things about NoSQL and that it may eventually become the replacement for SQL DB storage methods due to the fact that DB interaction is often a bottle neck for speed on the web. So I just have a few questions: What exactly is…
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Querying DynamoDB by date

I'm coming from a relational database background and trying to work with amazon's DynamoDB I have a table with a hash key "DataID" and a range "CreatedAt" and a bunch of items in it. I'm trying to get all the items that were created after a specific…
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Eventual consistency in plain English

I often hear about eventual consistency in different speeches about NoSQL, data grids etc. It seems that definition of eventual consistency varies in many sources (and maybe even depends on a concrete data storage). Can anyone give a simple…
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Is mongodb running?

I have installed Mongodb and the PHP drivers on my Unix server. My question is how can I tell if Mongodb is running? Is there a simple command line query to check status? If I start it once from the shell will it keep running if I exit the shell…
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