V03 of the package DDL: the runs table's nullable outcome_blob column, and a GIN index on metadata.

outcome_blob

A run's own answer, kept where a reader that has never seen the run live can find it. A durable subchart child's completion used to exist only on the step that produced it - a stored record carries no donedata - which is fine while a completion is answered immediately and not fine once N of them have to be collected and assembled in index order. The column is written once, at the child's completion, by StatifierPersistence.Storage.update_run_status/4.

Nullable, because almost no run has one: an ordinary run answers nobody, and a run that fails at creation never completes.

It is a blob column, not a jsonb one, and the difference is a disclosure decision rather than a typing convenience. metadata is restricted to host identities (ADR-0006 decision 2) precisely because :blob_type encryption does not reach a queryable column. A donedata payload carries whatever the chart's author put in it, so it belongs on the side of that line the encryption reaches: outcome_blob joins the three existing blob columns and takes the configured :blob_type with them.

The metadata GIN index

V02 shipped no index and said why: which pairs a host queries by is the host's call (ADR-0006 decision 4). Fan-out settlement changes the arithmetic. Every child completion asks "are all N of my siblings terminal?", which is the same jsonb containment query the cascade already issues, so one fan-out of N children issues N of them; without an index each is a sequential scan of the host's whole runs table. That is not a cost a host can be left to discover in production, so this package now ships the index the query it issues needs.

jsonb_path_ops rather than the default jsonb_ops: containment (@>) is the only operator either query uses, and the path-ops opclass serves exactly that, with a smaller index. A host that needs the wider operator set, or an expression index on particular keys, still adds its own - ADR-0006 decision 4's clause is narrowed by this migration, not withdrawn, and the record carries a dated Note saying so.

Adapters other than Postgres

GIN and jsonb_path_ops are Postgres spellings. up/1 therefore creates the index only when the migration's repo runs on Ecto.Adapters.Postgres, and down/1 drops it under the same condition; on any other adapter both steps are skipped and the migration otherwise runs to completion. Before that check existed the whole of V03 rolled back on a SQLite repo - ecto_sqlite3 raises ArgumentError from using: - which took the outcome_blob column with it and left such a host unable to run this package's DDL at all (sp-11w).

The column is created on every adapter, because it is a nullable binary column and every adapter has one. That is what keeps StatifierPersistence.Storage.Ecto.supports_run_outcome?/1 true everywhere.

Skipping the index is not the same as the index not mattering. What the index serves - the jsonb containment queries StatifierPersistence.Storage.Ecto.list_runs_by_metadata/2 and list_run_states_by_metadata/2 issue - is Postgres-only SQL in its own right, so an adapter that cannot take the index cannot run the queries either and says so: that adapter's metadata support is declared false, and a durable subchart or fan-out over such a store is refused at open rather than started and left unsettleable. sp-5lm tracks the Ecto adapter's Postgres-only surface.