Category Archives: Release

First release of Andl.NET

Andl.NET is a pure implementation of the Relational Algebra for manipulating
relational data in any .NET language. While Andl itself is a full programming
language, Andl.NET relies on another language such as C# and simply provides
the higher order queries.

Andl.NET can perform relational queries at or beyond the capabilities
of any SQL dialect. It can do all the ordinary things like select, where
and join but it can also do generative queries, self-joins, complex
aggregations, subtotals and running totals (a bit like SQL recursive
common table expressions and windowing).

Andl.NET has its own in-memory database so it can provide a complete
application backend for any kind of user interface on any platform. It can
easily be used to program a data model as a set of tables just like SQL, but
including all the access routines, without the need for an Object Relational

Andl.NET can retrieve data from Csv, Txt, Sql, Odbc and Oledb but does not
provide any persistence mechanism. (Left as an exercise for the caller!)

The core feature of Andl.NET is an implementation of the generic interface
IRelatable<T>. This provides a series of extension methods similar in flavour
to Linq’s IEnumerable<T> and IQueryable<T>, but directly implementing the core
features of the Relational Algebra.

The main differences from SQL are:
* all joins are natural (by attribute name)
* relations (tables) have no duplicate tuples (rows)
* data values cannot be null.

The main differences from Linq are:
* provides sources, stores and updates as well as queries
* many additional relational operations

Sample programs are included to demonstrate these capabilities. Familiarity
with Linq will help in reading them.

A future release of Andl.NET will generate SQL so that queries can be
executed on a relational database backend.

The release is here.

The licence is Licence.

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Lambdas and functions as values

Andl now has ‘functions as values’, and lambda literals.

A lambda is the literal form of a value of type ‘function’. It corresponds to a defined function but can be treated as a first class value: it can be

  • stored in a variable, component member of a user-defined type or attribute of a tuple
  • passed as a parameter
  • executed by the postfix operator of parentheses enclosing an argument list.

The syntactic definition is similar to a function definition omitting the name.

// function literal
def funlit(def(a:'') => a & a)
// function variable
var funval := def def(a:'') => a & a
// direct call on function value
(def def(a:'') => a & a)(‘ab’)

In this example, funlit, funval and the literal lambda can be called interchangeably. The value can be stored in a variable, user type component or tuple attribute and can be passed as a parameter. There is no type declaration as such, just literals of the type. Treating the function call on values as a postfix operator produces an odd asymmetry:

funval(‘ab’) // legal
funlit(‘ab’) // legal
(funval)(‘ab’) // legal
(funlit)(‘ab’) // illegal! [Built in and user-defined operators are still second class.]

Please note that these are individual function values, not methods. They have access to local and global scope, but there is no object or instance scope.

The latest release provides the working system and samples. Download from github.

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Support for PostgreSQL released

Andl now supports PostgreSQL as a backend database.

The latest release of Andl now makes it possible to use PostgreSQL as a backend database, with Andl relations stored as native PostgreSQL tables and Andl queries translated into PostgreSQL SQL for execution.

All features of Andl work identically on all supported platforms, where implemented. Open functions and aggregations (evaluated from within a query) are fully supported, as are Andl native types and user-defined types. Currently the only features not implemented are ‘while’ queries (similar to SQL common table expression recursive) and ordered queries (similar to SQL window functions).

Andl scripts can be compiled and Andl functions stored in the Andl catalog for later execution (similar to SQL stored procedures). Andl is implemented as a PostgreSQL installed language, so it is possible to call Andl functions from SQL. The server-based access to those functions using Web API, REST or Thrift interfaces will be part of a later release.

The Github project is here. The release is here.


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Announcing: Andl Syntax 6

Andl syntax has been evolving over time. The original syntax was somewhat cryptic and a bit of a challenge for anyone to understand. Also some parts of the syntax could be ambiguous in some situations, or at least would limit the generality of some constructs. It has also become increasingly clear that much of the syntax has direct parallels in SQL, and that it is people who already know SQL who are most likely to be interested.

Introducing Syntax 6. The key development is that each of the parts of a query takes a form that is closely parallel to a corresponding construct in SQL. So, for example:

  • The function .where(expression) performs the same function as an SQL WHERE clause.
  • The function .order(field, field...) performs the same function as an SQL ORDER BY clause.
  • The function .set{ field, field:=value } performs the same function as an SQL SELECT.

And there are lots more. These are postfix functions (with a dot) that follow a relational expression. On the other hand JOIN and UNION are infix operations, placed between two values. When you put them together you get something like this SQL query and the corresponding Andl code.

// SQL>select distinct sname from s, sp, p where p.color='Red' and s.s#=sp.s# and p.p#=sp.p#
(S .set{ S#, SNAME } join SP .set{ S#, P#} join P .set{ P#,COLOR }) .where(COLOR='Red') .set{ SNAME }

The order is not quite the same but all the same elements are there. If you know SQL, now with Syntax 6 you can learn Andl easily!

Latest releases are on the Downloads page. There are lots more examples of SQL and matching Andl syntax in the sample file SPPSample1.andl.

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Announcing: Andl Workbench

Andl now has an interactive program for writing and experimenting with queries, called Andl Workbench.

Andl Workbench should be familiar to anyone who has used MySql Workbench or Microsoft SQL Server Management Studio. It shows the current contents of a database catalog, and allows queries to be written and tested. Here is what it looks like.


Get the latest release form the Downloads page.

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Announcing: Andl with Thrift is here

Thrift is a platform-independent API technology, see It’s a “software framework for scalable cross-language services development, combining a software stack with a code generation engine to build services that work efficiently and seamlessly between C++, Java, Python, PHP, Ruby, Erlang, Perl, Haskell, C#, Cocoa, JavaScript, Node.js, Smalltalk, OCaml and Delphi and other languages”. And now with Andl.

Andl provides the following Thrift-related capabilities.

  1. The Andl compiler can generate a Thrift Interface Definition Language (IDL) file as an optional output.
  2. The Andl runtime performs data conversion to and from the format required by Thrift classes for wire transmission.

That’s all you really need. To put together a complete application involves the following steps.

  1. Write the database backend in Andl.
  2. Compile with the /t switch to generate the Thrift IDL. Compiled data and code are stored in a database catalog.
  3. Run the Thrift IDL compiler to generate an API of callable functions in the target language.
  4. The release includes a generic server written in C# using Thrift classes, which can be modified to suit specific needs. It simply needs to load the catalog.
  5. The release also includes sample client programs using both Thrift classes and the target language API functions, but containing no Andl  code or functions at all.
  6. The developer should modify the client programs or create new ones that call the target language API according to the needs of the application.

And that’s it. Mostly it is just Thrift and the Thrift documentation applies. The end result is that you can write an Andl program that exposes a set of callable entry points, and then call them from any Thrift-supported language.

Check the Downloads page for the current release.


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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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