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ravendb: All content tagged as ravendb in NoSQL databases and polyglot persistence

Document Databases and RavenDB

Brian Ritchie talked about document database and RavenDB at ☞ Jacksonville Software Architecture Group:

Original title and link: Document Databases and RavenDB (NoSQL databases © myNoSQL)


RavenDB: Index Replication to Relational Databases

Interesting (and I think unique) feature added to RavenDB:

RavenDB is a great database for storing documents, and the ability to create indexes on top of documents make extracting information out of the indexes very easy. There are situations, especially for reports, when you still want to use a relational database. The Index Replication Bundle is meant to handle just those scenarios. It is capable of replicating an index a table in a relational database.

Original title and link: RavenDB: Index Replication to Relational Databases (NoSQL databases © myNoSQL)

via: http://ayende.com/Blog/archive/2010/09/22/ravendb-replicating-to-a-relational-database.aspx


Document Databases Compared: CouchDB, MongoDB, RavenDB

Brian Ritchie has two posts (☞ here and ☞ here) covering three document databases: CouchDB, MongoDB, and RavenDB concluding with the matrix below:

But before using this as a reference material there are a couple of corrections needed:

They have some special characteristics that make them kick some serious SQL.

  • Objects can be stored as documents: The relational database impedance mismatch is gone. Just serialize the object model to a document and go.
  • Documents can be complex: Entire object models can be read & written at once. No need to perform a series of insert statements or create complex stored procs.
  • Documents are independent: Improves performance and decreases concurrency side effects
  • Open Formats: Documents are described using JSON or XML or derivatives. Clean & self-describing.
  • Schema free: Strict schemas are great, until they change. Schema free gives flexibility for evolving system without forcing the existing data to be restructured.
  • Built-in Versioning: Most document databases support versioning of documents with the flip of a switch.
  1. Judging by the growing number of document database mapping tools, I’m not sure impedance mismatch is really gone (related to 1st point above)
  2. Using embedded format is not always the best solution for mapping relationships and other more complex data structures. (related to 2nd and 3rd points above)
  3. Versioning is an extra-feature that is not fundamental to document databases. MongoDB and CouchDB do not support it by default, but there are different solutions available

Related to the matrix comparison:

  1. Versioning is not supported by either MongoDB and CouchDB. MVCC should not be confused for document versioning
  2. Sharding: CouchDB doesn’t support sharding out of teh box. There are different solutions for scaling CouchDB, using Cloudant Dynamo-like scaling solution for CouchDB, or even running CouchDB with a Riak backend
  3. Replication: both MongoDB and CouchDB support master/master and master/slave
  4. Security: check firstly the NoSQL databases and security post and decide for yourself and the “basic” level is enough for your app

Original title and link for this post: Document Databases Compared: CouchDB, MongoDB, RavenDB (published on the NoSQL blog: myNoSQL)


RavenDB in Production

Good question on Stackoverflow (it applies to the other document database, Terrastore too):

I’m having a hard time finding applications and websites that use RavenDB in production. Does anyone have first-hand experience with this, or examples of (well-known) sites that run on RavenDB?

I assume that both are too young to have production installations at this moment.

RavenDB in Production originally posted on the NoSQL blog: myNoSQL

via: http://stackoverflow.com/questions/3494342/anyone-using-ravendb-in-a-production-environment


Microsoft Azure and NoSQL Databases: MongoDB, sones GraphDB, and RavenDB

Looks like today is the day of the NoSQL databases in the Microsoft cloud. After covering how to run MongoDB on Azure and today’s guide to running sones GraphDB on Azure, the third one joining the party is RavenDB:

The short answer was, with the current build, no. RavenDB uses the .NET HttpListener class internally, and apparently that class will not work on worker roles, which are restricted to listening on TCP only.

[…]

I have to sign a contribution agreement, and do some more extensive testing, but I hope that Ayende is going to pull my TCP changes into the RavenDB trunk so that this deployment model is supported by the official releases.

So, two document stores and a graph database are already available for Microsoft Azure. Which one is next?

Microsoft Azure and NoSQL Databases: MongoDB, sones GraphDB, and RavenDB originally posted on the NoSQL blog: myNoSQL

via: http://blog.markrendle.net/2010/08/running-ravendb-on-azure.html


Presentations: Oren Eini on NoSQL and RavenDB

Bookmark this for the time you’ll be looking into RavenDB or when you’ll have around 6 hours to watch Oren Eini (Ayende Rahien) talk on NoSQL and RavenDB.

Embedded below are the slides from Introduction to RavenDB:


VoltDB Don’ts Validating NoSQL Assumptions

Interesting to note that some VoltDB don’ts from the paper ☞ Do’s and Don’ts (pdf) are validating some major assumptions in the NoSQL space:

Don’t create tables with very large rows (that is, lots of columns or large VARCHAR columns). Several smaller tables with a common partitioning key are better.

Basically both wide-column stores (i.e. Cassandra, HBase, Hypertable) with their column-families and document databases (i.e. CouchDB, MongoDB, RavenDB, Terrastore) with their schema-less approach are addressing this issue.

  1. Don’t use ad hoc SQL queries as part of a production application.

Firstly this points to the mindset change required by the NoSQL space when doing data modeling: think about data access patterns.

Secondly, it pretty much validates CouchDB and RavenDB approaches of having queries defined upfront making their reads extremely fast.


Document Database Query Language

Recently I have noticed that Doctrine[1], a PHP library focused on persistence services, has been working on ☞ defining a new query language for document databases.

So, I couldn’t stop asking myself is there a need for a (new) document query language?

To be able to answer this question, I thought I should firstly review what are the existing solutions/approaches.

  1. CouchDB doesn’t allow running dynamic queries against the store, but you can define views with the help of Javascript-based mapreduce functions.
  2. MongoDB allows dynamic and pretty complex queries, but it is using a custom query API.
  3. RavenDB, the latest addition to the document database space, has chosen the route of Linq[2] for defining indexes.
  4. Terrastore supports predicate (XPath currently) and range queries offering a mapreduce-like solution. You can read more about these in the Terrastore 0.5.0 article
  5. Last, but not least, XML databases are using XPath for querying.

Simply put, it looks like each solution comes with its own approach. While it will probably make sense to create a unified query language for document databases, I see only two possible solutions:

  • either make all document databases sign up to use this query language (note: this might be quite difficult)
  • or provide it through a framework that works will all of the existing document stores (note: this might not be possible)

But do not create a new query language in a framework that works only with a single document store.


  1. ☞ Doctrine project website  ()
  2. ☞ LINQ: a set of extensions to the .NET framework that encompass language-integrated query, set, and transform operations.  ()

Comparing Document Databases to Key-Value Stores

Oren Eini has an interesting ☞ post emphasizing the main differences between document databases (f.e. CouchDB, MongoDB, etc.) and key-value stores (f.e. Redis, Project Voldemort, Tokyo Cabinet):

The major benefit of using a document database comes from the fact that while it has all the benefits of a key/value store, you aren’t limited to just querying by key.

One of the main advantages of data transparency (as opposed to opaque data) is that the engine will be able to perform additional work without having to translate the data into an intermediary or a format that it understands. Querying by non primary key is such an example. The various document stores provide different implementation flavors depending on index creation time, index update strategy, etc. Oren goes on and covers the query behavior for CouchDB, Raven and MongoDB:

In the first case (nb indexes prepared ahead of time), you define an indexing function (in Raven’s case, a Linq query, in CouchDB case, a JavaScript function) and the server will run it to prepare the results, once the results are prepared, they can be served to the client with minimal computation. CouchDB and Raven differs in the method they use to update those indexes, Raven will update the index immediately on document change, and queries to indexes will never wait. […] With CouchDB, a view is updated at view query time, which may lead to a long wait time on the first time a view is accessed if there were a lot of changes in the meanwhile. […]

Note that in both CouchDB and Raven’s cases, indexes do not affect write speed, since in both cases this is done at a background task.

MongoDB, on the other hand, allows ad-hoc querying, and relies on indexes defined on the document values to help it achieve reasonable performance when the data size grows large enough. MongoDB’s indexes behave in much the same way RDBMS indexes behave, that is, they are updated as part or the insert process, so large number of indexes is going to affect write performance.

Another good resource explaining the differences between MongoDB and CouchDB queries is Rick Osbourne’s ☞ article.

After RavenDB made his appearance in the NoSQL space we’ll probably have to compare it to the existing CouchDB and MongoDB features.

This is not to say that some of this functionality cannot be achieved with pure key-value stores, but these seem to be focused mainly on single/multi key lookups and most probably you’ll have to build this additional layer by yourself.


New Projects in NoSQL Space

Lately I’ve been hearing about a couple of newcomers in the NoSQL space so here is your chance to find out about them and why not provide other readers with some additional feedback about each of them:

kumofs

Kumofs is a distributed key-value store built on top of Tokyo Cabinet and using the memcached protocol.

According to the ☞ project homepage:

  • Data is partitioned and replicated over multiple servers.
  • Extreme single node performance; comparable with memcached.
  • Both read and write performance got improved as servers added.
  • Servers can be added without stopping the system.
  • Servers can be added without modifying any configuration files.
  • The system does not stop even if one or two servers crashed.
  • The system does not stop to recover crashed servers.
  • Automatic rebalancing support with a consistency control algorithm.
  • Safe CAS operation support.
  • memcached protocol support.

There already seems to be ☞ success story of kumofs, but you’ll have to take that with a grain of salt as the same company was announcing a success story with Redis for the same problem.

Raven DB

Raven DB is a dual licensed document database for the .NET platform with a RESTful API.

According to the ☞ project homepage:

  • Scalable infrastructure: Raven builds on top of existing, proven and scalable infrastructure
  • Simple Windows configuration: Raven is simple to setup and run on windows as either a service or IIS7 website
  • Transactional: Raven support System.Transaction with ACID transactions. If you put data in it, that data is going to stay there
  • Map/Reduce: Easily define map/reduce indexes with Linq queries
  • .NET Client API: Raven comes with a fully functional .NET client API which implements Unit of Work and much more
  • RESTful: Raven is built around a RESTful API

Orient

Orient comes in two flavors: OrientDB: a document database and OrientKV a key-value store, both running on the Java platform.

According to the ☞ project homepage, OrientDB is a

scalable Document based DBMS that uses the features of the Graph Databases to handle links. It’s the basic engine of all the Orient products. It can work in schema-less mode, schema-full or a mix of both. Supports advanced features, such as indexing, fluent and SQL-like queries. It handles natively JSON and XML documents.

The OrientKV is a:

Key/Value Server based on the Document Database technology and accessible as embedded repository via Java APIs or via HTTP using a RESTful API. Orient K/V uses a new algorithm called RB+Tree, derived from the Red-Black Tree and from the B+Tree. Orient Key/Value server can run in high availability mode using a cluster of multiple nodes partitioned.

Have you tried any of these?

Pincaster

According to the GitHub page, Pincaster is a persistent NoSQL database to store geographic data and key/value pairs, with a HTTP/JSON interface. Unfortunately there’s almost no documentation about the project so I don’t think there’s anything else I could add for now.

Update: hint received from @fs111