88 lines
2.8 KiB
Python
88 lines
2.8 KiB
Python
"""Database engine and session plumbing.
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Synchronous SQLAlchemy on purpose: the background scheduler, the Telegram
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polling bot and the request handlers all touch the same tables, and one boring
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threadsafe sessionmaker is far easier to reason about than three event loops.
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FastAPI runs plain `def` endpoints in a threadpool, so nothing blocks.
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"""
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from __future__ import annotations
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from collections.abc import Iterator
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from contextlib import contextmanager
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from sqlalchemy import create_engine, inspect, text
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from sqlalchemy.orm import DeclarativeBase, Session, sessionmaker
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from app.config import env_settings
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class Base(DeclarativeBase):
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pass
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def _engine_kwargs(url: str) -> dict:
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if url.startswith("sqlite"):
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# One file, many threads (scheduler + bot + requests).
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return {"connect_args": {"check_same_thread": False}}
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return {"pool_pre_ping": True, "pool_size": 5, "max_overflow": 10}
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engine = create_engine(env_settings().database_url, **_engine_kwargs(env_settings().database_url))
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SessionLocal = sessionmaker(bind=engine, autoflush=False, expire_on_commit=False)
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# Columns a refactor later dropped from the model but, with no migration tool
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# in this project, left behind on any database that was already running —
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# still `NOT NULL` with no server-side default, so every insert that no
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# longer sets them fails. `create_all` only ever adds; this is the other half.
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_DEAD_COLUMNS: dict[str, tuple[str, ...]] = {
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"tasks": ("completed_here",),
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}
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def _drop_dead_columns() -> None:
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inspector = inspect(engine)
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existing_tables = set(inspector.get_table_names())
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with engine.begin() as conn:
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for table, columns in _DEAD_COLUMNS.items():
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if table not in existing_tables:
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continue
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existing_columns = {c["name"] for c in inspector.get_columns(table)}
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for column in columns:
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if column in existing_columns:
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conn.execute(text(f'ALTER TABLE {table} DROP COLUMN {column}'))
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def init_db() -> None:
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"""Create any missing tables. The schema is additive, so this is enough —
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plus the one-time cleanup above for columns a refactor removed from the
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model."""
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from app import models # noqa: F401 (register the mappers)
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Base.metadata.create_all(bind=engine)
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_drop_dead_columns()
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@contextmanager
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def session_scope() -> Iterator[Session]:
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"""A transactional session for background jobs and scripts."""
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session = SessionLocal()
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try:
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yield session
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session.commit()
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except Exception:
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session.rollback()
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raise
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finally:
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session.close()
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def get_session() -> Iterator[Session]:
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"""FastAPI dependency: one session per request, committed by the endpoint."""
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session = SessionLocal()
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try:
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yield session
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finally:
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session.close()
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