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# File 'lib/online_migrations/background_migrations/background_migration_class_validator.rb', line 7
def validate(record)
relation = record.migration_relation
migration_name = record.migration_name
if !relation.is_a?(ActiveRecord::Relation)
record.errors.add(
:migration_name,
"#{migration_name}#relation must return an ActiveRecord::Relation object"
)
return
end
if relation.arel.orders.present? || relation.arel.taken.present?
record.errors.add(
:migration_name,
"#{migration_name}#relation cannot use ORDER BY or LIMIT due to the way how iteration with a cursor is designed. " \
"You can use other ways to limit the number of rows, e.g. a WHERE condition on the primary key column."
)
end
end
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