ReadRdf

This repository is based on https://github.com/duckdb/extension-template, check it out if you want to build and ship your own DuckDB extension.

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This extension, ReadRdf, allow you to read RDF files directly into DuckDB. For now we support the NTriples format but technicaly possible to support turtle, XML serializations etc. Just more code.. Parsing of NTriples is via finite state machine (e.g. no dependencies for that).

Five columns are returned for RDF. Subject, predicate, object, language_tag (if present), datatype (if present).

Building

Managing dependencies

DuckDB extensions uses VCPKG for dependency management. Enabling VCPKG is very simple: follow the installation instructions or just run the following:

git clone https://github.com/Microsoft/vcpkg.git
./vcpkg/bootstrap-vcpkg.sh
export VCPKG_TOOLCHAIN_PATH=`pwd`/vcpkg/scripts/buildsystems/vcpkg.cmake

Note: VCPKG is only required for extensions that want to rely on it for dependency management. If you want to develop an extension without dependencies, or want to do your own dependency management, just skip this step. Note that the example extension uses VCPKG to build with a dependency for instructive purposes, so when skipping this step the build may not work without removing the dependency.

(As of now, not using VCPKG but leaving it here incase it's worth integrating something like SERD. )

Build steps

Now to build the extension, run:

make

The main binaries that will be built are:

./build/release/duckdb
./build/release/test/unittest
./build/release/extension/read_rdf/read_rdf.duckdb_extension

• duckdb is the binary for the duckdb shell with the extension code automatically loaded.
• unittest is the test runner of duckdb. Again, the extension is already linked into the binary.
• read_rdf.duckdb_extension is the loadable binary as it would be distributed.

Running the extension

To run the extension code, simply start the shell with ./build/release/duckdb.

Now we can use the features from the extension directly in DuckDB. The template contains a single table function read_rdf() that takes a single string arguments (the name of the NTriples file) and returns a table:

D select * from read_rdf('tests.nt');
┌──────────────────────┬──────────────────────┬──────────────────────┬──────────────┬────────────────────────────┐
│       subject        │      predicate       │        object        │ language_tag │        datatype_iri        │
│       varchar        │       varchar        │       varchar        │   varchar    │          varchar           │
├──────────────────────┼──────────────────────┼──────────────────────┼──────────────┼────────────────────────────┤
│ http://example.org…  │ http://www.w3.org/…  │ http://xmlns.com/f…  │ NULL         │ NULL                       │
│ http://example.org…  │ http://xmlns.com/f…  │ John Doe             │ NULL         │ NULL                       │
│ http://example.org…  │ http://xmlns.com/f…  │ 30                   │ NULL         │ http://www.w3.org/2001/X…  │
│ http://example.org…  │ http://xmlns.com/f…  │ jane                 │ NULL         │ NULL                       │
│ jane                 │ http://www.w3.org/…  │ http://xmlns.com/f…  │ NULL         │ NULL                       │
│ jane                 │ http://xmlns.com/f…  │ Jane Smith           │ en           │ NULL                       │
│ http://example.org…  │ http://purl.org/dc…  │ The Great Book       │ NULL         │ NULL                       │
│ http://example.org…  │ http://purl.org/dc…  │ http://example.org…  │ NULL         │ NULL                       │
│ http://unicode.org…  │ http://example.org…  │ 🦆                   │ NULL         │ NULL                       │
└──────────────────────┴──────────────────────┴──────────────────────┴──────────────┴────────────────────────────┘

Running the tests

Test for this extension are SQL tests in ./test/sql. They rely on a sample triples file tests.nt These SQL tests can be run using:

make test

Installing the deployed binaries

To install from GitHub actions:

• navigate to the actions for this repo
• click on the latest successful build
• select the architecture you want from the left hand navigation
• open the Run actions/upload artifact step
• find the artifact URL for the compiled extension
• download, unzip and then install to DudkDB

To install your extension binaries from S3, you will need to do two things. Firstly, DuckDB should be launched with the allow_unsigned_extensions option set to true. How to set this will depend on the client you're using. Some examples:

CLI:

duckdb -unsigned

Python:

con = duckdb.connect(':memory:', config={'allow_unsigned_extensions' : 'true'})

NodeJS:

db = new duckdb.Database(':memory:', {"allow_unsigned_extensions": "true"});

Secondly, you will need to set the repository endpoint in DuckDB to the HTTP url of your bucket + version of the extension you want to install. To do this run the following SQL query in DuckDB:

SET custom_extension_repository='bucket.s3.eu-west-1.amazonaws.com/<your_extension_name>/latest';

Note that the /latest path will allow you to install the latest extension version available for your current version of DuckDB. To specify a specific version, you can pass the version instead.

After running these steps, you can install and load your extension using the regular INSTALL/LOAD commands in DuckDB:

INSTALL read_rdf
LOAD read_rdf