When to use CouchDB over MongoDB and vice versa

Question

I am stuck between these two NoSQL databases    In my project I will be creating a database within a database  For example  I need a solution to create dynamic tables    So users can create tables with columns and rows  I think either MongoDB or CouchDB will be good for this  but I am not sure which one  I will also need efficient paging as well

User · Answer

Be aware of an issue with sparse unique indexes in MongoDB. I've hit it and it is extremely cumbersome to workaround.

The problem is this - you have a field, which is unique if present and you wish to find all the objects where the field is absent. The way sparse unique indexes are implemented in Mongo is that objects where that field is missing are not in the index at all - they cannot be retrieved by a query on that field - {$exists: false} just does not work.

The only workaround I have come up with is having a special null family of values, where an empty value is translated to a special prefix (like null:) concatenated to a uuid. This is a real headache, because one has to take care of transforming to/from the empty values when writing/quering/reading. A major nuisance.

I have never used server side javascript execution in MongoDB (it is not advised anyway) and their map/reduce has awful performance when there is just one Mongo node. Because of all these reasons I am now considering to check out CouchDB, maybe it fits more to my particular scenario.

BTW, if anyone knows the link to the respective Mongo issue describing the sparse unique index problem - please share.

User · Answer

Very old question but it s on top of Google and I don t quite like the answers I see so here s my own   There s much more to Couchdb than the ability to develop CouchApps  Most people use CouchDb in a classical 3-tiers web architecture    In practice the deciding factor for most people will be the fact that MongoDb allows ad-hoc querying with a SQL like syntax while CouchDb doesn t  you ve got to create map reduce views which turns some people off even though creating these views is Rapid Application Development friendly - they have nothing to do with stored procedures    To address points raised in the accepted answer   CouchDb has a great versionning system  but it doesn t mean that it is only suited  or more suited  for places where versionning is important  Also  couchdb is heavy-write friendly thanks to its append-only nature  writes operations return in no time while guaranteeing that no data will ever be lost    One very important thing that is not mentioned by anyone is the fact that CouchDb relies on b-tree indexes  This means that whether you have 1  row  or 20 billions  the querying time will always remain below 10ms  This is a game changer which makes CouchDb a low-latency and read-friendly database  and this really shouldn t be overlooked   To be fair and exhaustive the advantage MongoDb has over CouchDb is tooling and marketing  They have first-class citizen tools for all major languages and platforms making the on-boarding easy and this added to their adhoc querying makes the transition from SQL even easier   CouchDb doesn t have this level of tooling - even though there are many libraries available today - but CouchDb is exposed as an HTTP API and it is therefore quite easy to create a wrapper in your favorite language to talk with it  I personally like this approach as it avoids bloat and allows you to only take what you want  interface segregation principle    So I d say using one or the other is largely a matter of comfort and preference with their paradigms  CouchDb approach  just fits   for certain people  but if after learning about the database features  in the exhaustive official guide  you don t have your  hell yeah  moment  you should probably move on    I d discourage using CouchDb if you just want to use  the right tool for the right job   because you ll find out that you can t just use it that way and you ll end up being pissed and writing blog posts such as  Where are joins in CouchDb    and  Where is transaction management     Indeed  Couchdb is - paradoxically - very transparent but at the same time requires a paradigm shift and a change in the way you approach problems to really shine  and really work     But once you ve done that it really pays off  I d personally need very strong reasons or a major deal breaker on a project to choose another database  but so far I haven t met any

User · Answer

I m sure you can with Mongo  more familiar with it   and pretty sure you can with couch too   Both are documented oriented  JSON-based  so there would be no  columns  but rather fields in documents -- but they can be fully dynamic   They both do it you may want to look at other factors on which to use  other features you care about  popularity  etc  Google insights  indeed com job posts would be ways to look at popularity   You could just try it i think you should be able to have mongo running in 5 minutes

User · Answer

Ask this questions yourself  And you will decide your DB selection    Do you need master-master  Then CouchDB  Mainly CouchDB supports master-master replication which anticipates nodes being disconnected for long periods of time  MongoDB would not do well in that environment  Do you need MAXIMUM R W throughput  Then MongoDB Do you need ultimate single-server durability because you are only going to have a single DB server  Then CouchDB  Are you storing a MASSIVE data set that needs sharding while maintaining insane throughput  Then MongoDB  Do you need strong consistency of data  Then MongoDB  Do you need high availability of database  Then CouchDB   Are you hoping multi databases and multi tables  collections  Then MongoDB You have a mobile app offline users and want to sync their activity data to a server  Then you need CouchDB  Do you need large variety of querying engine  Then MongoDB Do you need large community to be using DB  Then MongoDB

User · Answer

I summarize the answers found in that article   http   www quora com How-does-MongoDB-compare-to-CouchDB-What-are-the-advantages-and-disadvantages-of-each  MongoDB  Better querying  data storage in BSON  faster access   better data consistency  multiple collections  CouchDB  Better replication  with master to master replication and conflict resolution  data storage in JSON  human-readable  better access through REST services   querying through map-reduce   So in conclusion  MongoDB is faster  CouchDB is safer   Also  http   nosql mypopescu com post 298557551 couchdb-vs-mongodb

User · Answer

Of C  A  amp  P  Consistency  Availability  amp  Partition tolerance  which 2 are more important to you  Quick reference  the Visual Guide To NoSQL Systems   MongodB   Consistency and Partition Tolerance CouchDB   Availability and Partition Tolerance   A blog post  Cassandra vs MongoDB vs CouchDB vs Redis vs Riak vs HBase vs Membase vs Neo4j comparison has  Best used  scenarios for each NoSQL database compared  Quoting the link     MongoDB  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  CouchDB   For accumulating  occasionally changing data  on which pre-defined queries are to be run  Places where versioning is important    A recent  Feb 2012  and more comprehensive comparison by Riyad Kalla     MongoDB   Master-Slave Replication ONLY CouchDB   Master-Master Replication   A blog post  Oct 2011  by someone who tried both  A MongoDB Guy Learns CouchDB commented on the CouchDB s paging being not as useful   A dated  Jun 2009  benchmark by Kristina Chodorow  part of team behind MongoDB    I d go for MongoDB   Hope it helps

User · Answer

The answers above all over complicate the story    If you plan to have a mobile component  or need desktop users to work offline and then sync their work to a server you need CouchDB  If your code will run only on the server then go with MongoDB   That s it  Unless you need CouchDB s  awesome  ability to replicate to mobile and desktop devices  MongoDB has the performance  community and tooling advantage at present

[mongodb] When to use CouchDB over MongoDB and vice versa

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