🐛 fix(schema): 修复 PostgreSQL 模式备份恢复与重命名

- 模式备份脚本写入安全转义的 CREATE SCHEMA IF NOT EXISTS
- 支持仅大小写变化的 PostgreSQL 模式重命名
- 补充备份头顺序、非 PostgreSQL 隔离和模式 DDL 回归测试

Fixes #480

internal/app/methods_db.go

@@ -322,7 +322,7 @@ func buildRenameSchemaSQLWithText(dbType string, oldSchemaName string, newSchema
 	if oldSchemaName == "" || newSchemaName == "" {
 		return "", fmt.Errorf("%s", text("db.backend.error.schema_name_required", nil))
 	}
-	if strings.EqualFold(oldSchemaName, newSchemaName) {
+	if oldSchemaName == newSchemaName {
 		return "", fmt.Errorf("%s", text("db.backend.error.schema_same_name", nil))
 	}
 	if !isPostgresSchemaDDLDBType(dbType) {

internal/app/methods_db_i18n_test.go

@@ -406,7 +406,7 @@ func TestMethodsDBSchemaDDLUsesEnglishMessages(t *testing.T) {
 		t.Fatalf("expected localized schema name message, got %q", missingSchemaName.Message)
 	}
 
-	sameSchemaName := app.RenameSchema(connection.ConnectionConfig{Type: "postgres", Database: "tenant"}, "", "sales", "SALES")
+	sameSchemaName := app.RenameSchema(connection.ConnectionConfig{Type: "postgres", Database: "tenant"}, "", "sales", "sales")
 	if sameSchemaName.Success {
 		t.Fatalf("RenameSchema with same names returned success: %+v", sameSchemaName)
 	}

internal/app/methods_db_schema_test.go

@@ -62,6 +62,17 @@ func TestBuildRenameSchemaSQL_PostgresQuotesIdentifiers(t *testing.T) {
 	}
 }
 
+func TestBuildRenameSchemaSQL_PostgresAllowsCaseOnlyRename(t *testing.T) {
+	got, err := buildRenameSchemaSQL("postgresql", "sales", "SALES")
+	if err != nil {
+		t.Fatalf("expected postgres case-only schema rename SQL, got error: %v", err)
+	}
+	const want = `ALTER SCHEMA "sales" RENAME TO "SALES"`
+	if got != want {
+		t.Fatalf("unexpected case-only rename schema SQL, want %q got %q", want, got)
+	}
+}
+
 func TestBuildDropSchemaSQL_PostgresUsesCascade(t *testing.T) {
 	got, err := buildDropSchemaSQL("postgresql", `sales"ops`)
 	if err != nil {

internal/app/methods_file.go

@@ -3065,10 +3065,7 @@ func (a *App) ExportSchemaSQL(config connection.ConnectionConfig, dbName string,
 	w := bufio.NewWriterSize(f, 1024*1024)
 	defer w.Flush()
 
-	if err := writeSQLHeader(w, runConfig, dbName); err != nil {
-		return connection.QueryResult{Success: false, Message: err.Error()}
-	}
-	if _, err := w.WriteString(fmt.Sprintf("-- Schema: %s\n\n", safeSchemaName)); err != nil {
+	if err := writeSQLSchemaExportHeader(w, runConfig, dbName, safeSchemaName); err != nil {
 		return connection.QueryResult{Success: false, Message: err.Error()}
 	}
 	for _, objectName := range objects {
@@ -3322,6 +3319,33 @@ func writeSQLHeader(w *bufio.Writer, config connection.ConnectionConfig, dbName
 	return writeSQLHeaderWithDatabaseBootstrap(w, config, dbName, false)
 }
 
+func writeSQLSchemaExportHeader(
+	w *bufio.Writer,
+	config connection.ConnectionConfig,
+	dbName string,
+	schemaName string,
+) error {
+	safeSchemaName := strings.TrimSpace(schemaName)
+	if safeSchemaName == "" {
+		return errors.New("schema name is required")
+	}
+	if err := writeSQLHeader(w, config, dbName); err != nil {
+		return err
+	}
+	if _, err := w.WriteString(fmt.Sprintf("-- Schema: %s\n\n", safeSchemaName)); err != nil {
+		return err
+	}
+	dbType := resolveDDLDBType(config)
+	if isPostgresSchemaDDLDBType(dbType) {
+		_, err := w.WriteString(fmt.Sprintf(
+			"CREATE SCHEMA IF NOT EXISTS %s;\n\n",
+			quoteIdentByType(dbType, safeSchemaName),
+		))
+		return err
+	}
+	return nil
+}
+
 func writeSQLDatabaseBackupHeader(w *bufio.Writer, config connection.ConnectionConfig, dbName string) error {
 	return writeSQLHeaderWithDatabaseBootstrap(w, config, dbName, true)
 }

internal/app/methods_file_export_test.go

@@ -1717,3 +1717,53 @@ func TestFilterExportViewLookupBySchema_PostgresQualifiedViewsOnly(t *testing.T)
 		t.Fatalf("expected public.v_users to be filtered out, got=%v", got)
 	}
 }
+
+func TestWriteSQLSchemaExportHeaderPostgresCreatesQuotedSchema(t *testing.T) {
+	var output bytes.Buffer
+	writer := bufio.NewWriter(&output)
+	if err := writeSQLSchemaExportHeader(
+		writer,
+		connection.ConnectionConfig{Type: "postgres"},
+		"app_db",
+		`Sales"Ops`,
+	); err != nil {
+		t.Fatalf("write postgres schema export header: %v", err)
+	}
+	if err := writer.Flush(); err != nil {
+		t.Fatalf("flush postgres schema export header: %v", err)
+	}
+
+	content := output.String()
+	if !strings.Contains(content, `-- Schema: Sales"Ops`) {
+		t.Fatalf("schema export header must describe the selected schema, content=%q", content)
+	}
+	if !strings.Contains(content, `CREATE SCHEMA IF NOT EXISTS "Sales""Ops";`) {
+		t.Fatalf("schema export header must bootstrap the quoted schema, content=%q", content)
+	}
+	databaseIndex := strings.Index(content, "-- Database: app_db")
+	schemaIndex := strings.Index(content, `-- Schema: Sales"Ops`)
+	createIndex := strings.Index(content, `CREATE SCHEMA IF NOT EXISTS "Sales""Ops";`)
+	if databaseIndex < 0 || schemaIndex < databaseIndex || createIndex < schemaIndex {
+		t.Fatalf("schema bootstrap must follow the database and schema metadata, content=%q", content)
+	}
+}
+
+func TestWriteSQLSchemaExportHeaderDoesNotBootstrapNonPostgresSchema(t *testing.T) {
+	var output bytes.Buffer
+	writer := bufio.NewWriter(&output)
+	if err := writeSQLSchemaExportHeader(
+		writer,
+		connection.ConnectionConfig{Type: "mysql"},
+		"app_db",
+		"sales",
+	); err != nil {
+		t.Fatalf("write non-postgres schema export header: %v", err)
+	}
+	if err := writer.Flush(); err != nil {
+		t.Fatalf("flush non-postgres schema export header: %v", err)
+	}
+
+	if strings.Contains(output.String(), "CREATE SCHEMA") {
+		t.Fatalf("non-postgres schema export must not inject postgres bootstrap SQL, content=%q", output.String())
+	}
+}