searchPattern — Load → Query

The simplest semantic process: get RDF in and ask questions of it. No inference, no validation, no carving — just the head and the read.

When to use it

You have RDF and you want to query it with SPARQL — joined, if you like, with regular SQL. This pattern works at any scale, including the full 8.2-billion-triple graph: Query is not the single-threaded constraint, so there is no carve waist here.

A worked scenario — people and their mailboxes

Three people; two have a mailbox, one does not.

Step 1 — load the data

SELECT pgrdf.add_graph(100);
SELECT pgrdf.parse_turtle('
@prefix ex:   <http://example.com/> .
@prefix foaf: <http://xmlns.com/foaf/0.1/> .

ex:alice foaf:name "Alice" ; foaf:mbox <mailto:alice@example.com> .
ex:bob   foaf:name "Bob" .
ex:carol foaf:name "Carol" ; foaf:mbox <mailto:carol@example.com> .
', 100);

Step 2 — a basic query

SELECT * FROM pgrdf.sparql(
  'PREFIX foaf: <http://xmlns.com/foaf/0.1/>
   SELECT ?n WHERE { ?s foaf:name ?n }');

One JSONB row per solution:

{"n": "Alice"}
{"n": "Bob"}
{"n": "Carol"}

Step 3 — refine with OPTIONAL

Pull in the mailbox where it exists, without dropping the people who have none — that is what OPTIONAL does:

SELECT * FROM pgrdf.sparql(
  'PREFIX foaf: <http://xmlns.com/foaf/0.1/>
   SELECT ?n ?m
   WHERE { ?s foaf:name ?n .
           OPTIONAL { ?s foaf:mbox ?m } }');

{"n": "Alice", "m": "mailto:alice@example.com"}
{"n": "Carol", "m": "mailto:carol@example.com"}
{"n": "Bob",   "m": null}

Bob keeps his row; his missing mailbox comes back as null rather than removing him from the result.

Grounded in the test suite

This is tests/w3c-sparql/04-optional-chain — the same data, query, and expected output, gated in CI against the hand-computed W3C result.

Compose with regular SQL

Because pgrdf.sparql is a set-returning function, the result joins straight into SQL — filter, aggregate, or join it against your own tables:

SELECT count(*) AS people_with_mbox
FROM pgrdf.sparql(
  'PREFIX foaf: <http://xmlns.com/foaf/0.1/>
   SELECT ?m WHERE { ?s foaf:mbox ?m }');
--  → 2

Next step

Add inference with Load → Reason → Query, or a conformance gate with Load → Validate → Query.