But let us have a look at the broader context, first.
Ever since the proclamation of UDDI or RUP, we may think that the U for Unified is a clear and unmistakable indicator for what Joel Spolsky would call architecture astronautitis. In case you’ve missed those hilarious posts, here they are:
- April 21, 2001: Don’t Let Architecture Astronauts Scare You
- October 21, 2005: Architecture Astronauts are Back
- May 01, 2008: Architecture Astronauts Take Over
Today, many software vendors are again trying to unify database query languages. Erik Meijer’s LINQ was the most successful attempt at doing so, so far. But even LINQ doesn’t compare to Codd’s visions, which were about replacing the whole data model first by a rock-solid mathematical theory, and only then, thinking about appropriate languages to query such data models.
Flexible vs. rigid abstractions
We believe that unifying query languages to query RDBMS, XML, Objects, and NoSQL is a bad idea because such a unification is subject to either:
- being a flexible abstraction
- being a rigid abstraction
If an abstraction is flexible, then the heterogeneous implementation details of the abstracted data stores will inevitably leak into the query language and into your application. You don’t gain too much, for the price of adding more layers and boiler-plate.
If an abstraction is rigid, then the unified query language (LINQ, JPQL, etc.) may be concise, but it will inevitably abstract away 80% of all useful features of the underlying data store. LINQ cannot meet the expressivity of SQL. Neither can it match the power of XPath/XQuery/XSLT/XProc, which is the most appropriate tool chain for XML. Maybe, it cannot even match what Java 8 calls the Streams API, which is very likely to become the most appropriate tool chain for objects and collections in Java.
Typesafe’s SLICK is Not About SQL
We’ve already compared Slick with jOOQ in our manual’s preface. Now, Christopher Vogt has made a clear statement about what SLICK is supposed to be and what SQL is:
There are understandable mistakes when your mind is (still) set on SQL. […]
Good luck with jooq and check back if you are ever annoyed by SQL semantics and want Scala back :).
That is only an extract of what Christopher said, of course, and there’s certainly quite a bit of goodness in SLICK. SLICK’s mission is to provide Scala collection semantics when querying databases. That might be a desireable thing to have in the Scala platform, specifically when comparing SLICK with LINQ.
But we’ve mentioned it before, on our blog. SQL is not an undesirable language or technology. Like any legacy technology, SQL has its ways. We’ve blogged about that, too, lots of times. SQL is a standard that is constantly evolving and that is here to stay. In our opinion, any technology operating on RDBMS but at the same time aiming for hiding SQL or abstracting it away completely is against the inevitable trend imposed by the big elephants who will not let go of their best-selling technologies.
SQL is about 10 years ahead of alternative RDBMS querying methods – most specifically Java, Scala, C# collection-based ones. T-SQL has now entered the TIOBE Top 10 and is considered by TIOBE to be the language of the year 2013, PL/SQL isn’t too far behind. Don’t fight SQL any longer, embrace it. Or in Christopher Vogt’s words:
Check back with SQL/jOOQ, if you are ever annoyed by the increasing amount of leaky or rigid abstraction created by modern language architects!
Further reading: “Don’t Jump the SQL Ship Just Yet”.