-- What the artifact store no longer keeps (novox/hq ADR 0189, issue 108).
--
-- The mesh removes from its store only what it put there and can account for: every digest it
-- could remove is already in a build record, so the sweep reads its own records rather than
-- enumerating the store. What it does not get from those records is whether it has already
-- removed something -- `build.made` says what that build published, for ever, which is history
-- and not an index of what is on disk.
--
-- Without this the sweep would reissue a delete for every artifact it has ever collected, every
-- time it runs, and each one would answer 404 -- a number of requests that grows with the mesh's
-- whole history and never shrinks.
--
-- Keyed by the reference as the mesh records it (`artifact-store://<module>/<artifact>@sha256:…`),
-- because that is the identity the record uses everywhere else. Not a foreign key to build: two
-- builds can publish the same digest (the same source built twice produces the same bytes), and
-- what is collected is the artifact, not the attempt that made it.
create table artifact_collected (
    reference text        primary key,

    -- When the store answered. Kept so a reader of an old build record can tell "this artifact is
    -- gone" from "this artifact was never there", which are different kinds of surprise.
    at        timestamptz not null default now()
);