Memgraph ZeroMemGQLConnectto DuckDB

DuckDB

The DuckDB connector (CONNECTOR_TYPE=duckdb) translates GQL queries into SQL and executes them against an embedded DuckDB instance. It requires a mapping file that maps graph patterns to relational tables.

DuckDB runs in-process (no separate server needed), making it ideal for local development and testing.

1. Create and seed a DuckDB database

docker network create memgql-net
 
# Create a DuckDB file with seed data using the DuckDB CLI
docker run --rm -v ./data:/data \
    datacatering/duckdb:v1.1.1 \
    -c "
CREATE TABLE persons (id INTEGER PRIMARY KEY, name TEXT, age INTEGER);
CREATE TABLE companies (id INTEGER PRIMARY KEY, name TEXT);
CREATE TABLE knows (from_id INTEGER, to_id INTEGER);
CREATE TABLE works_at (person_id INTEGER, company_id INTEGER);
 
INSERT INTO persons VALUES (1, 'Alice', 30), (2, 'Bob', 25);
INSERT INTO companies VALUES (1, 'Acme Corp');
INSERT INTO knows VALUES (1, 2);
INSERT INTO works_at VALUES (1, 1);
" /data/graph.duckdb

2. Start MemGQL

docker run --rm \
    --name memgql \
    --network memgql-net \
    --stop-timeout 2 \
    -p 7688:7688 \
    --env CONNECTOR_TYPE=duckdb \
    --env DUCKDB_PATH=/data/graph.duckdb \
    --env MAPPING_FILE=/data/mapping.json \
    --env BOLT_LISTEN_ADDR=0.0.0.0:7688 \
    -v ./data:/data \
    -v ./mapping.json:/data/mapping.json \
    memgraph/memgql:latest

For an in-memory database (no persistence), omit DUCKDB_PATH.

3. Connect

mgconsole --port 7688

4. Query

MATCH (p:Person) RETURN p.name, p.age;
MATCH (p:Person)-[:WORKS_AT]->(c:Company) RETURN p.name, c.name;
MATCH (a:Person)-[:KNOWS]->(b:Person) RETURN a.name, b.name;

For environment variables, see Reference.

Supported GQL features

FeatureDuckDB
MATCH / WHERE / RETURN✓
Pattern-level WHERE (MATCH (n WHERE …))✓
Multi-MATCH (cross-join)✓
OPTIONAL MATCH✓
WITH pipeline boundary✓
WITH DISTINCT / WITH … ORDER BY … LIMIT N✓
Chained WITH … WITH …✓
Whole-node WITH n carry-through✓
Typed edge (a)-[r:R]->(b)✓
Untyped edge ()-[]->(b)✓
UNION / UNION ALL / UNION DISTINCT✓
Quantified path (){m,n} — bounded✓
Map projections RETURN n {.a, .b}✓
IN list membership WHERE x IN [...]✓
STARTS WITH / ENDS WITH / CONTAINS✓
collect() aggregate✓
count, sum, avg, min, max✓
COUNT(DISTINCT …)✓
Arithmetic + - * / %✓
CASE WHEN … THEN … ELSE … END✓
COALESCE, NULLIF✓
INSERT (a {…}) RETURN a.x✓
DELETE✓
SET / REMOVE (property update / delete)✗
DETACH DELETE✗
INTERSECT / EXCEPT✗
Quantified path (){m,} — unbounded✗
Shortest-path (ALL SHORTEST / SHORTEST k)✗

Known limitations

  • Unbounded variable-length paths (()-[*]->()) are rejected. Bound the depth ({1,5}) or run the query against a Cypher backend.
  • MATCH p = (...) path binding on quantified traversals is not supported. Drop the path binding or run on a Cypher backend.
  • Whole-node RETURN n projects scalar columns rather than a Bolt Node struct. Use a map projection (RETURN n {.id, .name} AS info) for a single structured cell.
to Clickhouseto Iceberg