DB:: Migration:: Operation:: Optimization:: ResultType
Defines the various types of results that can be returned by a migration operation optimization.marten/db/migration/operation/optimization/result_type.cr
A "completed" result indicates that the considered migration operation was indeed optimized and that a new set of operations should be used in lieu of the operation.
A "failed" result indicates that the considered migration operation cannot be optimized, which generally means that that incoming operation used for optimizing has a dependency to the considered operation (for example, a CreateTable operation that has a reference column to a table created by another CreateTable operation).
An "unchanged" result indicates that no optimization can be done and that operations remain unchanged (for example, two completely unrelated operations that cannot be further optimized).