Announcement: Andl on SQLite

This is a preliminary announcement that Andl can now use Sqlite as a backend database. In other words, it has a preliminary implementation of The Third Manifesto Prescriptions 13, 14, 16 and 17 with respect to database relvars stored in Sqlite.

The language supported is identical to the in-memory version already released. The type system, expression evaluation and relational algebra are identical. There are no (known or intended) incompatibilities or restrictions, other than as below. The performance is reasonable (considering the stage of development), but a couple of areas need some work.

All relation and attribute types are supported, including DEE and DUM (relations with no attributes), Relation Valued Attributes, Tuple Valued Attributes and User Defined Types. There are however two areas not yet implemented due to challenges in the platform/SQL. They’re just plain hard!

  1. Aggregation (FOLD)
  2. Ordered aggregation (grouping)

For those interested, the strategy is a mix of SQL generation and a runtime Virtual Machine. The implementation strategy contains only a modest amount of Sqlite specific code. The exact same method should work with any of the main RDBMS. I would plan to tackle Postgres next (requires Java Interop), and then perhaps SQL Server.

I shall make a release available soon, hopefully when I have solved the above, it’s a bit more robust, and it performs a bit better.

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