89 files and 6,300 lines become one file of 807. Nothing about the
resulting schema changes; what goes away is the requirement that a new
installation replay our development history to arrive at it.
revision = "0089", down_revision = None. That pairing IS the migration
strategy for existing installs, not a detail of it: a deployed database
already has alembic_version = '0089' from running the real 0089, so
alembic reads the version table, sees head reached, and does nothing. No
stamp is required — which matters, because `alembic stamp` writes a
version string without validating anything about the schema it is writing
it against, and a wrong stamp is indistinguishable from a right one until
the next migration fails. An empty database runs the file and records
0089. Both paths converge. The next migration is 0090, as it would have
been; the numbering is continuous across the collapse on purpose.
Autogenerate produced nearly all of this unaided, which was NOT true of
the first attempt — that one was reverted because the generator silently
dropped eleven indexes and three uniqueness guarantees. #3275 put those
on the models first, so the HNSW index with its opclass, the COALESCE
expression index, the partial uniques, 107 server_defaults and the enum
CHECKs are all emitted now. Doing the reconciliation before the squash,
rather than after, is what made this work.
Hand-added, because none of it can live in a model:
* CREATE EXTENSION vector / tsm_system_rows (0001, 0004) — database
objects, not table metadata.
* The pgvector import. Autogenerate writes qualified
pgvector.sqlalchemy.vector.VECTOR references without importing the
package, so its own output cannot run (run 4988).
* THE TWO SEED ROWS. 0002 and 0003 did not only build schema — each
inserted a settings singleton, and nothing in the app ever creates
them: ImportSettings.load() and MLSettings.load() are
select(...).scalar_one(), which RAISES NoResultFound rather than
returning None. A models-only baseline would leave both tables empty
and crash a fresh install on first settings access, while
baseline.yml reported a perfect schema match. Only running the app
against a new database finds that.
Not carried over: 0023's DELETE FROM tag and 0047's series deletes, which
are historical cleanups operating on rows an empty database lacks.
downgrade() raises. A baseline's downgrade is "drop every table", which
is a data-loss event wearing a migration as a disguise; offering it as
one invites someone to run it. Restore from a backup.
Also removed, per the plan: the 10 test_migration_*.py files (they assert
intermediate states and backfills that no longer exist — a test that a
column exists is already the model tests' job) and
backend/app/utils/artist_backfill.py, whose only importer was 0008.
Verified no other consumer anywhere in backend/ or tests/.
baseline.yml changes with it. chain_ref now DEFAULTS to 725bf15, since
the tree no longer carries a chain to compare against — that pinned
commit is the last one that does.
And the CheckConstraint repair is removed, because it never fired. I
added it claiming autogenerate re-doubles a constraint name on the round
trip and asserted in b979062 that it was "still correct and still
needed". It is not: autogenerate wraps names in op.f(), which marks them
already-formatted and blocks the convention from re-applying. Tested
against the real candidate line — the regex matches nothing. What
actually fixed the mismatch was 0088's renames alone. The doubling is a
real hazard, but of hand-writing a pre-prefixed name, not of the
generator; the comment asserting otherwise was worse than the dead code
under it.
The header comment is rewritten for the same reason — it described 87
revisions, and claimed the HNSW index could not be expressed in a model,
which #3275 disproved. It now also states plainly what this check CANNOT
see: it compares schema, so a green run means the schema is right, not
that the baseline is.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_017QHszn9H8VBvx5Ke8x1hvw
bvandeusenandClaude Opus 5
973db73221