59 lines
1.7 KiB
Markdown
59 lines
1.7 KiB
Markdown
---
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title: Use Transactions for Database Operations
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impact: HIGH
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impactDescription: Transactions provide atomic database operations
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tags: transaction, database, postgres, sqlalchemy
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---
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## Use Transactions for Database Operations
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Transactions are a special type of step optimized for database access. They execute as a single database transaction. Only use with Postgres.
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**Incorrect (database access in regular step):**
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```python
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@DBOS.step()
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def save_to_db(data):
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# For Postgres, use transactions instead of steps
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# This doesn't get transaction guarantees
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engine.execute("INSERT INTO table VALUES (?)", data)
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```
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**Correct (using transaction):**
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```python
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from sqlalchemy import text
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@DBOS.transaction()
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def save_to_db(name: str, value: str) -> None:
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sql = text("INSERT INTO my_table (name, value) VALUES (:name, :value)")
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DBOS.sql_session.execute(sql, {"name": name, "value": value})
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@DBOS.transaction()
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def get_from_db(name: str) -> str | None:
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sql = text("SELECT value FROM my_table WHERE name = :name LIMIT 1")
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row = DBOS.sql_session.execute(sql, {"name": name}).first()
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return row[0] if row else None
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```
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With SQLAlchemy ORM:
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```python
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from sqlalchemy import Table, Column, String, MetaData, select
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greetings = Table("greetings", MetaData(),
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Column("name", String),
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Column("note", String))
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@DBOS.transaction()
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def insert_greeting(name: str, note: str) -> None:
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DBOS.sql_session.execute(greetings.insert().values(name=name, note=note))
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```
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Important:
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- Only use transactions with Postgres databases
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- For other databases, use regular steps
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- Never use `async def` with transactions
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Reference: [DBOS Transactions](https://docs.dbos.dev/python/reference/decorators#transactions)
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