Function validate_read_then_write_dependencies 

pub(crate) fn validate_read_then_write_dependencies(
    catalog: &Catalog,
    ids: impl IntoIterator<Item = CatalogItemId>,
    max_rw_dependencies: usize,
    policy: DependencyPolicy,
) -> Result<(), AdapterError>

Validates all transitive dependencies of a read-then-write selection.

User DML requires every relation leaf to be a writable user table. System reads accept supported system objects across time domains. Both reject mz_now().

The first invalid or temporal dependency encountered short-circuits with the corresponding error. Traversal is bounded at max_rw_dependencies distinct objects, returning AdapterError::ReadThenWriteDependencyLimitExceeded if exceeded.