Datamapper

Datamapper is an object-relational mapper library written in Ruby and commonly used with Merb. It was developed to address perceived shortcomings in Ruby on Rails' ActiveRecord library.

Some features of Datamapper:^[1]

• eager loading of child associations to avoid (N+1) queries
• lazy loading of select properties, e.g., larger fields
• query chaining, and not evaluating the query until absolutely necessary (using a lazy array implementation)
• an API not too heavily oriented to SQL databases

Datamapper was designed to be a more abstract ORM, not strictly SQL, based on Martin Fowler's enterprise pattern.^[2] As a result, people have built Datamapper adapters for other non-SQL databases, such as CouchDB^[3], Apache Solr^[4], and webservices such as Salesforce^[5].

References

1. ^ http://datamapper.org/why
2. ^ Fowler, Martin; David Rice, Matthew Foemmel, Edward Hieatt, Robert Mee, and Randy Stafford (November 2002). Patterns of Enterprise Application Architecture. Addison-Wesley. ISBN 0-321-12742-0. 
3. ^ http://github.com/kabari/dm-couchdb-adapter/tree/master
4. ^ http://github.com/lritter/dm-solr-adapter/tree/master
5. ^ http://github.com/halorgium/dm-salesforce/tree/master

External links

• Datamapper homepage