NoSQL - MongoDB vs CouchDB

Question

I am a complete noob when it comes to the NoSQL movement. I have heard lots about MongoDB and CouchDB. I know there are differences between the two. Which do you recommend learning as a first step into the NoSQL world?

Answer 1

See following links

• CouchDB Vs MongoDB
• MongoDB or CouchDB - fit for production?
• DB-Engines - Comparison CouchDB vs. MongoDB

Update: I found great comparison of NoSQL databases.

MongoDB (3.2)

• Written in: C++
• Main point: JSON document store
• License: AGPL (Drivers: Apache)
• Protocol: Custom, binary (BSON)
• Master/slave replication (auto failover with replica sets)
• Sharding built-in
• Queries are javascript expressions
• Run arbitrary javascript functions server-side
• Has geospatial indexing and queries
• Multiple storage engines with different performance characteristics
• Performance over features
• Document validation
• Journaling
• Powerful aggregation framework
• On 32bit systems, limited to ~2.5Gb
• Text search integrated
• GridFS to store big data + metadata (not actually an FS)
• Data center aware

Best used: If you need dynamic queries. If you prefer to define indexes, not map/reduce functions. If you need good performance on a big DB. If you wanted CouchDB, but your data changes too much, filling up disks.

For example: For most things that you would do with MySQL or PostgreSQL, but having predefined columns really holds you back.

CouchDB (1.2)

• Written in: Erlang
• Main point: DB consistency, ease of use
• License: Apache
• Protocol: HTTP/REST
• Bi-directional (!) replication,
• continuous or ad-hoc,
• with conflict detection,
• thus, master-master replication. (!)
• MVCC - write operations do not block reads
• Previous versions of documents are available
• Crash-only (reliable) design
• Needs compacting from time to time
• Views: embedded map/reduce
• Formatting views: lists & shows
• Server-side document validation possible
• Authentication possible
• Real-time updates via '_changes' (!)
• Attachment handling

Best used: For accumulating, occasionally changing data, on which pre-defined queries are to be run. Places where versioning is important.

For example: CRM, CMS systems. Master-master replication is an especially interesting feature, allowing easy multi-site deployments.