Function compareForeignKeys

backend/plugin/schema/differ.go:1018–1063

compareForeignKeys compares two lists of foreign keys.

(oldFKs, newFKs []*storepb.ForeignKeyMetadata)

// compareForeignKeys compares two lists of foreign keys.
func compareForeignKeys(oldFKs, newFKs []*storepb.ForeignKeyMetadata) []*ForeignKeyDiff {
	var changes []*ForeignKeyDiff

	oldFKMap := make(map[string]*storepb.ForeignKeyMetadata)
	for _, fk := range oldFKs {
		oldFKMap[fk.Name] = fk
	}

	newFKMap := make(map[string]*storepb.ForeignKeyMetadata)
	for _, fk := range newFKs {
		newFKMap[fk.Name] = fk
	}

	// Check for dropped foreign keys
	for fkName, oldFK := range oldFKMap {
		if _, exists := newFKMap[fkName]; !exists {
			changes = append(changes, &ForeignKeyDiff{
				Action:        MetadataDiffActionDrop,
				OldForeignKey: oldFK,
			})
		}
	}

	// Check for new and modified foreign keys
	for fkName, newFK := range newFKMap {
		oldFK, exists := oldFKMap[fkName]
		if !exists {
			changes = append(changes, &ForeignKeyDiff{
				Action:        MetadataDiffActionCreate,
				NewForeignKey: newFK,
			})
		} else if !foreignKeysEqual(oldFK, newFK) {
			// Drop the old FK and recreate the new one instead of altering
			changes = append(changes, &ForeignKeyDiff{
				Action:        MetadataDiffActionDrop,
				OldForeignKey: oldFK,
			})
			changes = append(changes, &ForeignKeyDiff{
				Action:        MetadataDiffActionCreate,
				NewForeignKey: newFK,
			})
		}
	}

	return changes
}

// foreignKeysEqual checks if two foreign keys are equal.
func foreignKeysEqual(fk1, fk2 *storepb.ForeignKeyMetadata) bool {