A Query.Farm VGI worker for DuckDB.

Decode & Generate QR Codes and Barcodes in DuckDB

vgi-barcode · a Query.Farm VGI worker · powered by rxing

A VGI worker (Rust, a compiled binary) that brings barcode and QR-code decoding and generation to DuckDB / SQL over Apache Arrow. DuckDB launches the worker and talks to it over Arrow IPC; the functions appear under the catalog barcode, schema main.

Decoding and encoding are powered by rxing, the maintained Rust port of ZXing.

LOAD vgi;
ATTACH 'barcode' (TYPE vgi, LOCATION './target/release/barcode-worker');
SET search_path = 'barcode.main';

-- Decode the first barcode in an image BLOB.
SELECT decode_barcode(content) AS text,
       barcode_format(content) AS format
FROM read_blob('label.png');
-- → 'vgi-barcode', 'QR_CODE'

-- Generate a QR-code PNG, then round-trip it.
SELECT decode_barcode(generate_qr('hi'));        -- → 'hi'

-- Generate an EAN-13 barcode PNG.
SELECT generate_barcode('5901234123457', 'EAN_13');

-- Every barcode found in one image (table function).
SELECT * FROM decode_barcodes(generate_qr('multi'));
-- seq | format  | text
--   0 | QR_CODE | multi

-- Discover the supported formats.
SELECT * FROM barcode_formats();

Functions

Scalar

Function	Returns	Description
decode_barcode(blob)	VARCHAR	Text of the first barcode found, or NULL.
barcode_format(blob)	VARCHAR	Format name of the first barcode (e.g. QR_CODE, EAN_13), or NULL.
generate_qr(text)	BLOB	QR-code PNG (default 256 px square).
generate_qr(text, size_px)	BLOB	QR-code PNG of the given size.
generate_barcode(text, format)	BLOB	PNG of text in format (default size).
generate_barcode(text, format, size_px)	BLOB	PNG of the given size.
barcode_version()	VARCHAR	Worker version string.

Table

Function	Columns	Description
decode_barcodes(blob)	seq BIGINT, format VARCHAR, text VARCHAR	Every barcode detected in one image (multi-decode).
barcode_formats()	format VARCHAR	The supported barcode format names.

DuckDB table functions take constant arguments (no subqueries), so the image BLOB passed to decode_barcodes must be a constant-foldable expression (a literal, or e.g. generate_qr('…')).

Supported formats

Decode (multi-format): QR codes, EAN-8/13, UPC-A/E, Code 128/39/93, Codabar, ITF, Data Matrix, PDF417, Aztec. Generation accepts the same canonical names (SELECT * FROM barcode_formats()); 1D symbologies impose their own payload constraints (e.g. EAN-13 needs 13 digits), and an unsupported format name is a clear error.

Behavior & robustness

Image bytes are treated as untrusted:

• A malformed, truncated, or hostile image never crashes the worker — it decodes to NULL (scalars) or no rows (decode_barcodes). A bad blob beside a good one still produces results.
• Decoding is bounded: images whose dimensions or pixel count exceed safe limits are rejected at the header stage, before pixels are materialized, so an "image bomb" cannot exhaust memory.
• NULL input → NULL output / no rows.
• On generation, an invalid format name (or a payload that cannot be encoded in the requested symbology) surfaces a clear DuckDB error.

Building & testing

cargo build --release                                   # build the worker
cargo test --workspace --all-features                   # unit + integration tests
cargo clippy --all-targets --all-features -- -D warnings # lint
make test-sql                                           # DuckDB SQL end-to-end

make test-sql builds the release worker, points VGI_BARCODE_WORKER at it, and runs the haybarn-unittest sqllogictest suite under test/sql/. Install the runner once with uv tool install haybarn-unittest. Regenerate the committed fixture images with make fixtures.

License

MIT — see LICENSE.

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Authorship & License

Written by Query.Farm.

Copyright 2026 Query Farm LLC - https://query.farm