This package is modeled closely after LINQ. If you are not familiar with LINQ, this is a great overview. It is especially recommended if you associate LINQ mainly with a query syntax in a language and don't know about the underlying language features and architecture, for example how anonymous types, lambdas and lots of other language features all play together. The query syntax is really just the tip of the iceberg.

The core idea of this package right now is to iterate over NamedTuples for table like data structures. Starting with a DataFrame, query will create an iterator that produces a NamedTuple that has a field for each column, and the collect method can turn a stream of NamedTuples back into a DataFrame.

If one starts with a queryable data source (like SQLite), the query will automatically be translated into SQL and executed in the database.

The wording of methods and types currently follows LINQ, not julia conventions. This is mainly to prevent clashes while Query.jl is in development.


The original LINQ document is still a good read.

The The Wayward WebLog has some excellent posts about writing query providers:

Joe Duffy wrote an interesting article about iterator protocolls:

On NULL values and 3VL in .Net.