What is the async for pattern with asyncpg?

Question

Accepted Answer

**asyncpg** uses **async for** for streaming database results.

```python
import asyncpg
import asyncio

async def stream_users():
    conn = await asyncpg.connect("postgresql://localhost/db")

# Cursor-based streaming
    async with conn.transaction():
        async for record in conn.cursor("SELECT * FROM users"):
            process(record)  # Process one row at a time

await conn.close()

# With SQLAlchemy
from sqlalchemy.ext.asyncio import AsyncSession

async def stream_products(db: AsyncSession):
    result = await db.stream(select(Product))
    async for row in result:
        yield row

# Batch processing
async def process_large_dataset():
    conn = await asyncpg.connect("postgresql://localhost/db")

batch_size = 1000
    offset = 0

while True:
        records = await conn.fetch(
            "SELECT * FROM large_table OFFSET $1 LIMIT $2",
            offset, batch_size
        )
        if not records:
            break

for record in records:
            process(record)

offset += batch_size

await conn.close()

asyncio.run(stream_users())
```

**Benefits:**
- Memory efficient.
- Handles large datasets.
- Automatic connection management.

Python: What is the async for pattern with asyncpg?