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a2c6c8201b
The legacy pkg/persistence/migrations (DBMigration / dbmXXX) system now coexists with Alembic but accepts no new migrations — all new schema changes go through Alembic. - remove dbm026_llm_model_context_length (superseded by Alembic 0005_add_llm_context_length, which makes the identical change) - cap required_database_version at 25 (legacy chain dbm001-025 kept read-only to upgrade pre-existing 3.x DBs to the Alembic baseline) - add migrations/README.md documenting the freeze - document the Alembic-only policy and revision-id/idempotency rules in AGENTS.md
37 lines
1.6 KiB
Markdown
37 lines
1.6 KiB
Markdown
# Legacy migrations (DEPRECATED — do not add new files here)
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This directory holds the **legacy 3.x database migration system**
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(`DBMigration` subclasses in `dbmXXX_*.py`, registered via
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`@migration.migration_class(N)` and run from `pkg/persistence/mgr.py`).
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**This system is frozen. Do not add new `dbmXXX_*.py` migrations.**
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The chain is capped at version 25 (`required_database_version = 25` in
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`pkg/utils/constants.py`). These files exist only to upgrade pre-existing
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3.x databases up to the Alembic baseline (`0001_baseline`). Removing them
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would break in-place upgrades from old installations, so they are kept
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read-only.
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## All new schema changes use Alembic
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Migrations now live in `pkg/persistence/alembic/versions/`. To create one:
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```bash
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uv run python -m langbot.pkg.persistence.alembic_runner autogenerate "description of your change"
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```
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(requires `data/config.yaml` to exist). Review and edit the generated
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script before committing — Alembic migrations run automatically on startup
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and must be idempotent and guard against missing tables (the test suite
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runs them against empty databases).
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### Rules for Alembic revision ids
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- Keep the revision id **≤ 32 characters** — PostgreSQL stores
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`alembic_version.version_num` as `varchar(32)` and will raise
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`StringDataRightTruncationError` on overflow.
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- Guard every `op` call against a missing table / missing column
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(`inspector.get_table_names()` / `inspector.get_columns()`); fresh
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installs create the schema via `create_all()` and stamp the baseline,
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so migrations may run against tables that already match or do not exist.
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