Frequently Asked Questions

• Connections / Engines
  • How do I pool database connections? Are my connections pooled?
  • “MySQL Server has gone away”
  • How Do I “Retry” a Statement Execution Automatically?
  • I am using multiple connections with a SQLite database (typically to test transaction operation), and my test program is not working!
  • How do I use engines / connections / sessions with Python multiprocessing, or os.fork()?
• • My program is hanging when I say / metadata.drop_all()
  • How can I sort Table objects in order of their dependency?
• SQL Expressions
  • Why are percent signs being doubled up when stringifying SQL statements?
• ORM Configuration
  • How do I configure a Column that is a Python reserved word or similar?
  • I’m getting a warning or error about “Implicitly combining column X under attribute Y”
  • Why is ORDER BY required with (especially with subqueryload())?
• • How can I profile a SQLAlchemy powered application?
• Sessions / Queries
  • How do I make a Query that always adds a certain filter to every query?
  • I’ve created a mapping against an Outer Join, and while the query returns rows, no objects are returned. Why not?
  • Query has no __len__(), why not?
  • I’m calling and it isn’t removed from the parent collection!
  • how do I use ON DELETE CASCADE with SA’s ORM?
  • How do I walk all objects that are related to a given object?
  • Why does post_update emit UPDATE in addition to the first UPDATE?
• • I’m getting errors related to “numpy.int64”, “numpy.bool_”, etc.