PGresult *res = PQexec(conn, "CREATE EXTENSION IF NOT EXISTS vector");

PGresult *res = PQexec(conn, "CREATE TABLE items (id bigserial PRIMARY KEY, embedding vector(3))");

const char *paramValues[2] = {"[1,2,3]", "[4,5,6]"};
PGresult *res = PQexecParams(conn, "INSERT INTO items (embedding) VALUES ($1), ($2)", 2, NULL, paramValues, NULL, NULL, 0);

const char *paramValues[1] = {"[3,1,2]"};
PGresult *res = PQexecParams(conn, "SELECT * FROM items ORDER BY embedding <-> $1 LIMIT 5", 1, NULL, paramValues, NULL, NULL, 0);

PGresult *res = PQexec(conn, "CREATE INDEX ON items USING hnsw (embedding vector_l2_ops)");
// or
PGresult *res = PQexec(conn, "CREATE INDEX ON items USING ivfflat (embedding vector_l2_ops) WITH (lists = 100)");