FAQ¶

Q: How to check connection pool status?¶

A: Use the engine.status attribute:

status = engine.status
print(status)

Q: What's the difference between streaming query and regular query?¶

A: - Regular Query: Loads all results into memory, suitable for small datasets - Streaming Query: Returns results row by row, does not consume memory, suitable for large datasets

Q: How to customize result type?¶

A: Use the result_class parameter, supports tuple, dict, or custom model classes:

result = await engine.execute(
    "SELECT * FROM users",
    result_class=dict  # or custom model class
)

Q: How to handle transactions?¶

A: Set auto_commit=False and manage manually:

engine = Engine(url="...", auto_commit=False)
await engine.connect()

# Note: Transaction management in v2 requires manual connection control

Q: How to get error information?¶

A: Through result.error, result.error_no, and result.error_msg attributes:

result = await engine.execute("SELECT * FROM invalid_table")
if result.error:
    print(f"Error code: {result.error_no}")
    print(f"Error message: {result.error_msg}")

Q: How to batch insert data?¶

A: Use the execute_many() method:

data = [("张三", "zhangsan@example.com"), ("李四", "lisi@example.com")]
result = await engine.execute_many(
    "INSERT INTO users (name, email) VALUES (%s, %s)",
    data
)

A: You can create an Engine instance at application startup, then share it through dependency injection or global variables:

# app.py
engine = Engine(url="mysql://...")
await engine.connect()

# service.py
from app import engine

class UserService(AsMysql):
    def __init__(self):
        super().__init__(engine)

Q: How to set connection pool size?¶

A: Set based on application concurrency and database server performance:

Low concurrency applications: min_pool_size=2, max_pool_size=10
Medium concurrency: min_pool_size=5, max_pool_size=50
High concurrency applications: min_pool_size=10, max_pool_size=100+

Q: How to handle connection timeout?¶

A: You can set connection timeout through the connect_timeout parameter:

engine = Engine(
    url="mysql://...",
    connect_timeout=10  # 10 seconds timeout
)