How do you choose between lazy loading, joined loading, select-in loading, and raise-on-access in SQLAlchemy?

Chooses relationship loading from cardinality, query count, result size, and hidden-I/O boundaries.

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Lazy loading waits until code accesses a relationship, which is convenient but can hide extra queries. Joined loading fetches related rows in the same SQL statement and works well for bounded single-valued relationships, but collections can multiply rows. Select-in loading fetches parents first and related rows in a second query using their keys, which often fits collections. Raise-on-access is useful when unplanned lazy I/O should fail visibly.

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Chooses relationship loading from cardinality, query count, result size, and hidden-I/O boundaries.

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Chooses relationship loading from cardinality, query count, result size, and hidden-I/O boundaries.
Lazy loading waits until code accesses a relationship, which is convenient but can hide extra queries. Joined loading fetches related rows in the same SQL statement and works well for bounded single-valued relationships, but collections can multiply rows. Select-in loading fetches parents first and related rows in a second query using their keys, which often fits collections. Raise-on-access is useful when unplanned lazy I/O should fail visibly.
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I choose from the exact response shape and real cardinality. For twenty orders with one customer each, a join may be simple; for orders with many lines and tags, joining everything can create a large cartesian result, so select-in loading or an explicit projection is safer. Eager is not synonymous with efficient. I inspect statement count, rows transferred, duplicate data, and memory rather than optimizing only for one round trip.

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Enabling eager loading everywhere
Counting only SQL statements
Letting serialization choose what to load

How do you choose between lazy loading, joined loading, select-in loading, and raise-on-access in SQLAlchemy?

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