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Abstracting Data Query in Ruby with Ambition Ambition

by Sebastien Auvray on Sep 26, 2007 |
One of today's challenges is to reduce the complexity of accessing and integrating information from various sources. While .NET already has such LINQ, Ruby had no such solution. There are existing DSL projects for querying with Ruby but not as Ruby.

Chris Wanstrath brings his own solution: Ambition.  Ambition takes advantage of ParseTree to walk the parse tree and translate plain Ruby queries into SQL (when the target is a Relational Database), so at the end you'll be able to write your queries the Ruby way:

User.first
# which will translate into "SELECT * FROM users LIMIT 1"
User.select { |u| u.karma > 20 }.sort_by(&:karma).first(5)
# which will translate into "SELECT * FROM users WHERE (users.`karma` > 20)
# ORDER BY users.karma LIMIT 5"


While originally Chris was gunning for Rack, he changed his target since he discovered LINQ.
We’ve moved our sights from Rack to LINQ. That is, we don’t want to only support other ORMs—we want Ambition to be a query language for SQL, LDAP, XPath, the works. The 1.0 release will be backend-agnostic. Maybe then we’ll change the name to Hubris? Time will tell.
You can find latest sources at git://errtheblog.com/git/ambition

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Another Groovy plug :) by Thom Nichols

GORM does this very well too, although the approach is a bit different. I think I like this syntax better.

At some point GORM will support JPA, which (if I understand correctly) means it should be able to query XML and such as well.

Re: Another Groovy plug :) by Werner Schuster

There might be overlap in the querying features, but not in the approach. Following your link, GORM seems to use Builders or string queries, or something that seems to use the Groovy version of method_missing.

However, Ambition works by actually looking at the AST of the queries, and as such is similar to Macros in languages like LISP or Scheme. The link to LINQ (pun intended) is that LINQ uses the same approach.

Of course, the results of the various solutions are the same, but the approaches are different. Question is how well Ruby syntax lends itself to Macros: the Ambition queries still need to be legal Ruby code, otherwise it couldn't be parsed. This is different in LISP, since there isn't much syntax to speak of in the first place. Of course, taking a peek at LINQ can help here.

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