drop anonymous unique index

diff/diff.go

@@ -442,7 +442,7 @@ func (ctx *alterCtx) dropTableIndexes() error {
 	indexes := ctx.fromIndexes.Difference(ctx.toIndexes)
 	// drop index after drop constraint.
 	// because cannot drop index if needed in a foreign key constraint
-	lazy := make([]*model.Index, 0, indexes.Cardinality())
+	lazy := make([]model.Ident, 0, indexes.Cardinality())
 	for _, index := range indexes.ToSlice() {
 		indexStmt, ok := ctx.from.LookupIndex(index)
 		if !ok {
@@ -455,37 +455,30 @@ func (ctx *alterCtx) dropTableIndexes() error {
 			continue
 		}
 
-		var indexName model.Ident
-		if indexStmt.ConstraintName.Valid {
-			indexName = indexStmt.ConstraintName.Ident
-		} else if indexStmt.Name.Valid {
-			indexName = indexStmt.Name.Ident
-		} else {
-			var err error
-			indexName, err = ctx.guessDropTableIndexName(indexStmt)
+		indexName := getIndexName(indexStmt)
+		if !indexName.Valid {
+			name, err := ctx.guessDropTableIndexName(indexStmt)
 			if err != nil {
 				return err
 			}
+			indexName.Valid = true
+			indexName.Ident = name
 		}
 		if indexStmt.Kind != model.IndexKindForeignKey {
-			lazy = append(lazy, indexStmt)
+			lazy = append(lazy, indexName.Ident)
 			continue
 		}
 
 		ctx.begin()
 		ctx.writeString("DROP FOREIGN KEY ")
-		ctx.writeIdent(indexName)
+		ctx.writeIdent(indexName.Ident)
 	}
 
 	// drop index after drop CONSTRAINT
-	for _, indexStmt := range lazy {
+	for _, indexName := range lazy {
 		ctx.begin()
 		ctx.writeString("DROP INDEX ")
-		if !indexStmt.Name.Valid {
-			ctx.writeIdent(indexStmt.ConstraintName.Ident)
-		} else {
-			ctx.writeIdent(indexStmt.Name.Ident)
-		}
+		ctx.writeIdent(indexName)
 	}
 
 	return nil
@@ -538,33 +531,34 @@ LOOP:
 			continue
 		}
 
-		var name model.Ident
-		if idx.ConstraintName.Valid {
-			name = idx.ConstraintName.Ident
-		} else if idx.Name.Valid {
-			name = idx.Name.Ident
-		} else {
+		name := getIndexName(idx)
+		if !name.Valid {
 			continue
 		}
 
 		// this name should not be used in the "from".
 		for _, idx2 := range ctx.from.Indexes {
-			if idx2.ConstraintName.Valid {
-				if idx2.ConstraintName.Ident == name {
-					continue LOOP
-				}
-			} else if idx2.Name.Valid {
-				if idx2.Name.Ident == name {
-					continue LOOP
-				}
+			name2 := getIndexName(idx2)
+			if name2.Valid && name2.Ident == name.Ident {
+				continue LOOP
 			}
 		}
 
-		return name, nil // found
+		return name.Ident, nil // found
 	}
 	return "", fmt.Errorf("can not drop index without name: %q", indexStmt.ID())
 }
 
+func getIndexName(idx *model.Index) model.MaybeIdent {
+	if idx.Name.Valid {
+		return idx.Name
+	}
+	if idx.ConstraintName.Valid {
+		return idx.ConstraintName
+	}
+	return model.MaybeIdent{}
+}
+
 // equalIndex returns whether index a and b have same definition, excluding their names.
 func equalIndex(a, b *model.Index) bool {
 	if a.Table != b.Table {

diff/diff_test.go

@@ -522,14 +522,31 @@ type AutoNamedSpec struct {
 
 var autoSpecs = []AutoNamedSpec{
 	{
-		Name: "remove FOREIGN KEY that MySQL named automatically",
+		Name: "drop anonymous unique key",
+		Before: []string{
+			"CREATE TABLE `fuga` ( `id` INTEGER NOT NULL, UNIQUE KEY (`id`) )",
+		},
+		Current: []string{"CREATE TABLE `fuga` (" +
+			"`id` int NOT NULL," +
+			"UNIQUE KEY `id` (`id`)" +
+			") ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_ai_ci",
+		},
+		After: []string{
+			"CREATE TABLE `fuga` ( `id` INTEGER NOT NULL )",
+		},
+		Expect: []string{
+			"ALTER TABLE `fuga` DROP INDEX `id`",
+		},
+	},
+	{
+		Name: "remove anonymous FOREIGN KEY",
 		Before: []string{
 			"CREATE TABLE `f` ( `id` INTEGER NOT NULL AUTO_INCREMENT, PRIMARY KEY (`id`) )",
 			"CREATE TABLE `fuga` ( `id` INTEGER NOT NULL, `fid` INTEGER NOT NULL, FOREIGN KEY (fid) REFERENCES f (id) )",
 		},
 		Current: []string{
 			"CREATE TABLE `f` ( `id` int NOT NULL AUTO_INCREMENT, PRIMARY KEY (`id`) ) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_ai_ci",
-			"Create Table: CREATE TABLE `fuga` (" +
+			"CREATE TABLE `fuga` (" +
 				"`id` int NOT NULL," +
 				"`fid` int NOT NULL," +
 				"KEY `fid` (`fid`)," +
@@ -542,13 +559,41 @@ var autoSpecs = []AutoNamedSpec{
 		},
 		Expect: []string{
 			"ALTER TABLE `fuga` " +
-				"DROP FOREIGN KEY `fk`, " +
-				"DROP INDEX `fk`, " +
+				"DROP FOREIGN KEY `fuga_ibfk_1`, " +
 				"ADD INDEX `fid` (`fid`)",
 		},
 	},
 }
 
+func TestDiffWithAutoNamedObjects(t *testing.T) {
+	var buf bytes.Buffer
+	for _, spec := range autoSpecs {
+		t.Run(spec.Name, func(t *testing.T) {
+			buf.Reset()
+			before := joinQueries(spec.Before)
+			after := joinQueries(spec.After)
+			current := joinQueries(spec.Current)
+			expect := joinQueries(spec.Expect)
+
+			err := diff.Strings(&buf, before, after, diff.WithCurrentSchema(current))
+			if err != nil {
+				t.Errorf("spec %s failed: %v", spec.Name, err)
+				return
+			}
+
+			actual := buf.String()
+			if diff := cmp.Diff(expect, actual); diff != "" {
+				t.Errorf(
+					"spec %s mismatch (-want/+got)\n%s\n"+
+						"before = %q\n"+
+						"after  = %q",
+					spec.Name, diff, spec.Before, spec.After,
+				)
+			}
+		})
+	}
+}
+
 func TestDiffWithAutoNamedObjects_Integrated(t *testing.T) {
 	database.SkipIfNoTestDatabase(t)