Pattern 20 — Two-Node Dependency DAG

Class: Create (both nodes) | Test: test_cookbook_20_two_node_dag

When to use

Build a two-level analytics pipeline where a summary stream table depends on a base aggregation stream table.

Migration files

-- migrations/streams/c20_totals.sql
-- @aqueduct:schedule = "30s"
SELECT id, SUM(amount) AS total FROM raw_c20 GROUP BY id;

-- migrations/streams/c20_summary.sql
-- @aqueduct:schedule = "1m"
-- @aqueduct:depends_on = ["public.c20_totals"]
SELECT COUNT(*) AS num_customers FROM public.c20_totals;

Plan output

  + c20_totals     [create]   level 0
  + c20_summary    [create]   level 1 (depends on c20_totals)

Notes

  • aqueduct always applies nodes in topological order. c20_totals is created before c20_summary regardless of file order in migrations/streams/.
  • Use @aqueduct:depends_on to declare explicit dependencies when the planner cannot infer them from schema-qualified names in the SQL.