Function compareIndexes

backend/plugin/schema/differ.go:746–784

compareIndexes compares indexes between two tables.

(engine storepb.Engine, oldTable, newTable *model.TableMetadata)

// compareIndexes compares indexes between two tables.
func compareIndexes(engine storepb.Engine, oldTable, newTable *model.TableMetadata) []*IndexDiff {
	var changes []*IndexDiff

	oldIndexes := oldTable.ListIndexes()
	newIndexes := newTable.ListIndexes()

	// Check for dropped indexes
	for _, oldIdx := range oldIndexes {
		if newTable.GetIndex(oldIdx.GetProto().Name) == nil {
			changes = append(changes, &IndexDiff{
				Action:   MetadataDiffActionDrop,
				OldIndex: oldIdx.GetProto(),
			})
		}
	}

	// Check for new and modified indexes
	for _, newIdx := range newIndexes {
		oldIdx := oldTable.GetIndex(newIdx.GetProto().Name)
		if oldIdx == nil {
			changes = append(changes, &IndexDiff{
				Action:   MetadataDiffActionCreate,
				NewIndex: newIdx.GetProto(),
			})
		} else if !indexesEqual(engine, oldIdx.GetProto(), newIdx.GetProto()) {
			// Drop the old index and recreate the new one instead of altering
			changes = append(changes, &IndexDiff{
				Action:   MetadataDiffActionDrop,
				OldIndex: oldIdx.GetProto(),
			})
			changes = append(changes, &IndexDiff{
				Action:   MetadataDiffActionCreate,
				NewIndex: newIdx.GetProto(),
			})
		}
	}

	return changes
}

// indexesEqual checks if two indexes are equal.
func indexesEqual(engine storepb.Engine, idx1, idx2 *storepb.IndexMetadata) bool {