A Dart client API to DuckDb

Features

Sending and executing statements works. Fetching the data back into Dart works for most important data types.

All database operations are sync 😃.

There are several features that are not yet implemented. For example:

• Inserting data into DuckDb is usually done with an appender. Right now, the recommended way to insert bulk data is to use the native DuckDb functionality read_csv, read_parquet, read_json_auto, see documentation.

• Complex data types (list, struct, array)

Because DuckDb also has a WASM implementation, it should be possible to run/embed it into Flutter and on the Web. I have not explored that direction.

Disclaimer

As I am not an expert in databases, C, or even Dart, there should be significant room for improvement in the performance and ergonomics of this package. PR's are welcome. I may not be able to engage in the long term maintenance of this package, and it's very likely that I won't provide the level of support the community needs. If the development of this package is not happening fast enough for you, consider becoming a contributor so you can take this project further and faster. I created this package because DuckDB was worth exploring and there are not a lot of DB offerings for Dart on the backend.

A huge thanks to the Dart FFI package designers. The FFI gen just works! It's amazing.

Getting started

I only have access to an Ubuntu 22.04 and a Windows 10 machine for testing. The package has been tested with the 1.1.0 DuckDb version.

To use the package, you need to install the Command line and the C/C++ bindings on your machine, see installation.
It is painless process. For Linux systems, just copy the libduckdb.so in the /usr/local/lib folder. For Window, make sure the dll is on your path.

Usage

final con = Connection.inMemory();
con.execute('CREATE TABLE tbl (state VARCHAR, population INTEGER);');
con.execute("INSERT INTO tbl VALUES ('CA', 39539223), ('VA', 8631393);");
var result = con.fetch('SELECT * FROM tbl;');
con.close();  // close the connection to release resources

You can also load an existing database from disk

final con = Connection('data.duckdb');
final res = con.fetch('SHOW TABLES;');
con.close();

Or read in a csv file directly

final con = Connection.inMemory();
con.execute("CREATE TABLE ontime AS SELECT * FROM 'flights.csv'");
con.fetch('SELECT * FROM ontime LIMIT 5;');

See the test/duckdb_test.dart for more examples.

Map query result to a Dart class

For convenience, you can map a row of the resulting query directly to a Dart class using fetchRows. For example, given the table

con.execute('CREATE TABLE people (name VARCHAR, age INTEGER);');
con.execute("INSERT INTO people VALUES ('Tom', 31), ('Jenny', 29), ('Maria', 33);");

and the class

final class Person {
  Person({required this.name, required this.age});
  String name;
  int age;
}

you can map the rows of the table to a Person using fetchRows

final result = con.fetchRows('SELECT name, age FROM people ORDER BY name;',
    (List row) => Person(name: row[0], age: row[1]));
assert(result.length == 3);
assert(result.first.name == 'Jenny');
assert(result.first.age == 29);

Additional information

The documentation on the DuckDb web site is comprehensive. For more info on Db internals, see the presentation.

Info for authors

The Dart client is based on the DuckDb C API. The DuckDb tests for the C API are located at https://github.com/duckdb/duckdb/blob/main/test/api/capi

Download the C/C++ DuckDb bindings and extract the zip file.

• Put the duckdb.h header file in the ./third_party folder
• Copy the libduckdb.so in the /usr/local/lib folder
• Run dart run ffigen --config ffigen.yaml to generate the bindings.
  Bindings get generated in file ./src/ffi/duckdb.g.dart