parththakkar106andClaude Opus 5
d3756abdaa
Phase 14 SP1. The tree goes into the schema and nothing reads it yet: a `branches` table, `branch_id`/`depth` on actions and memories, a head pointer on adventures, migrations 46-52, and a server-side backfill that re-reads every existing adventure as a tree with one branch. `depth` holds the number `index` already held, gaps included, so no story changes — a linear story *is* a tree with one branch, which is what makes the SP0 baseline passing unmodified the pass condition rather than a hope. The writer had to come with it. No migration will ever visit a row written after it ran, so columns backfilled today and populated next subphase would leave a hole exactly the width of one deploy, and from SP2 on a row without a branch is a row no read can see. `app/tree.py` owns that: one module, because a node written without a branch fails by disappearing rather than by raising. Three things the schema itself insisted on: - `adventures.head_branch_id` is a plain integer, not a foreign key. Pointing both ways makes the two tables a cycle create_all cannot order, and its escape hatch needs an ALTER SQLite does not have. It is a cache, and a head naming a branch that is gone recovers onto the root. - `lineage` is NOT NULL, so the backfill inserts `'[]'` and fills it in a second pass guarded on `json_array_length(lineage) = 0` — not `= '[]'`, because Postgres `json` has no equality operator. - SQLite will not drop a column a foreign key names, which is how two existing tests broke: they simulated an old database by rewinding the stamp while leaving the new columns in place. Every ADD COLUMN migration is now idempotent, and `tests/test_tree_migration.py` builds a genuine schema 45 by rebuilding three tables from frozen DDL so the real ALTERs run. 297 tests green, 14 of them new. `branches` costs 0.1 kB of a 733.5 kB turn; page load and index are byte-identical to the recorded figures. The deploy that ships this needs one `VACUUM FULL actions;` on the direct endpoint afterwards — it rewrites every row. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_017Dvvqn9ZDR4ixeFPHNbww7
48 lines
2.3 KiB
Python
48 lines
2.3 KiB
Python
"""Make a database look like an older schema version, so a migration can run.
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`create_all` always builds the *current* schema. A test that wants to watch a
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migration happen therefore has to take the newer columns back off before it
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stamps an older version — otherwise the migration meets a table that already
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has its column and dies on a duplicate.
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Rewinding the stamp alone was enough for a while, which is why two test files
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did exactly that. It stopped being enough the moment another `ADD COLUMN`
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landed after theirs: the replay then runs migrations they never meant to
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exercise, against columns `create_all` had already made. This module is that
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rewind done properly, in one place, so appending a migration means adding its
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inverse here rather than discovering three unrelated test failures.
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SQLite only — every test that replays migrations runs on a temp file, and
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`PRAGMA user_version` is where the stamp lives there. Migrations that change a
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column's *type* (43–45, JSON to compressed bytes) have no clean inverse and are
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not listed: they get replayed as-is, which is what the tests using them already
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relied on.
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"""
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from sqlalchemy import text
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from sqlalchemy.engine import Engine
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# (version that added it, statements that take it back off), newest first.
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#
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# Phase 14's `branch_id` columns are deliberately absent: SQLite refuses to drop
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# a column a foreign key names ("unknown column in foreign key definition"), so
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# a current-schema database cannot be rewound past them at all. That is what
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# `migrations._column_already_there` is for — the replay skips DDL that has
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# already happened, so the tree migrations run their backfill against a schema
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# that already has the columns, which is exactly the situation here.
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_UNDO: list[tuple[int, tuple[str, ...]]] = [
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# Packed float32 vectors and the flag beside them.
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(39, ("ALTER TABLE memories DROP COLUMN embedded",)),
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(38, ("ALTER TABLE memories DROP COLUMN embedding_blob",)),
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]
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def rewind_to(engine: Engine, version: int) -> None:
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"""Drop everything added after `version`, then stamp the database at it."""
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with engine.begin() as conn:
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for added_at, statements in _UNDO:
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if added_at > version:
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for sql in statements:
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conn.execute(text(sql))
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conn.execute(text(f"PRAGMA user_version = {version}"))
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