DataMapper

DataMapper is an object-relational mapper library written in Ruby that follows the active record pattern even though the name implies it follows the data mapper pattern. While DataMapper 1 may not have achieved total decoupling between object and database suggested by the data mapper pattern, it appears DataMapper 2 intended to change this (a la Virtus, a library adapted from DataMapper).[1] The DataMapper 2 project was renamed before launch and was released as Ruby Object Mapper (ROM) in August 2013.[2]

Some features of DataMapper:[3]

  • 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.[4] As a result, DataMapper adapters have been built for other non-SQL databases, such as CouchDB,[5] Apache Solr,[6] and webservices such as Salesforce.com.[7]

References

  1. ↑ "datamapper wiki: Roadmap". GitHub.
  2. ↑ "Where is DataMapper 2?". Google Groups.
  3. ↑ http://datamapper.org/why
  4. ↑ Fowler, Martin; David Rice; Matthew Foemmel; Edward Hieatt; Robert Mee; Randy Stafford (November 2002). Patterns of Enterprise Application Architecture. Addison-Wesley. ISBN 0-321-12742-0.
  5. ↑ https://github.com/kabari/dm-couchdb-adapter/tree/master
  6. ↑ https://github.com/lritter/dm-solr-adapter/tree/master
  7. ↑ https://github.com/halorgium/dm-salesforce/tree/master
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