🐛 fix(dameng): 修复表设计字段注释加载失败

增加 SYSCOLUMNCOMMENTS 原生字典降级查询，按字段名合并注释；原生字典无权限时保留基础元数据，并补充回归测试。

internal/db/dameng_columns_runtime_test.go

@@ -28,6 +28,7 @@ var registerDamengColumnsMetadataDriverOnce sync.Once
 var damengColumnsMetadataQueryState struct {
 	sync.Mutex
 	failAutoIncrementQuery bool
+	failColumnCommentQuery bool
 	queries                []string
 }
 
@@ -49,6 +50,7 @@ func (damengColumnsMetadataConn) QueryContext(_ context.Context, query string, _
 	damengColumnsMetadataQueryState.Lock()
 	damengColumnsMetadataQueryState.queries = append(damengColumnsMetadataQueryState.queries, query)
 	failAutoIncrementQuery := damengColumnsMetadataQueryState.failAutoIncrementQuery
+	failColumnCommentQuery := damengColumnsMetadataQueryState.failColumnCommentQuery
 	damengColumnsMetadataQueryState.Unlock()
 
 	if strings.Contains(query, "DBMS_METADATA.GET_DDL") {
@@ -67,6 +69,19 @@ func (damengColumnsMetadataConn) QueryContext(_ context.Context, query string, _
 		}, nil
 	}
 
+	if strings.Contains(query, "SYS.SYSCOLUMNCOMMENTS") {
+		if failColumnCommentQuery {
+			return nil, errors.New("insufficient privilege for SYS.SYSCOLUMNCOMMENTS")
+		}
+		return &damengColumnsMetadataRows{
+			columns: []string{"COLUMN_NAME", "COL_COMMENT"},
+			values: [][]driver.Value{
+				{"ID", "订单主键"},
+				{"NAME", "客户名称"},
+			},
+		}, nil
+	}
+
 	if strings.Contains(query, "SYS.SYSCOLUMNS") {
 		if failAutoIncrementQuery {
 			return nil, errors.New("insufficient privilege for SYS.SYSCOLUMNS")
@@ -132,16 +147,18 @@ func openDamengColumnsMetadataDB(t *testing.T) *sql.DB {
 	return conn
 }
 
-func resetDamengColumnsMetadataQueryState(t *testing.T, failAutoIncrementQuery bool) {
+func resetDamengColumnsMetadataQueryState(t *testing.T, failAutoIncrementQuery, failColumnCommentQuery bool) {
 	t.Helper()
 
 	damengColumnsMetadataQueryState.Lock()
 	damengColumnsMetadataQueryState.failAutoIncrementQuery = failAutoIncrementQuery
+	damengColumnsMetadataQueryState.failColumnCommentQuery = failColumnCommentQuery
 	damengColumnsMetadataQueryState.queries = nil
 	damengColumnsMetadataQueryState.Unlock()
 	t.Cleanup(func() {
 		damengColumnsMetadataQueryState.Lock()
 		damengColumnsMetadataQueryState.failAutoIncrementQuery = false
+		damengColumnsMetadataQueryState.failColumnCommentQuery = false
 		damengColumnsMetadataQueryState.queries = nil
 		damengColumnsMetadataQueryState.Unlock()
 	})
@@ -154,7 +171,7 @@ func damengColumnsMetadataQueries() []string {
 }
 
 func TestDamengGetColumnsMarksAutoIncrementColumns(t *testing.T) {
-	resetDamengColumnsMetadataQueryState(t, false)
+	resetDamengColumnsMetadataQueryState(t, false, false)
 
 	damengDB := &DamengDB{conn: openDamengColumnsMetadataDB(t)}
 	columns, err := damengDB.GetColumns("biz", "orders")
@@ -170,15 +187,18 @@ func TestDamengGetColumnsMarksAutoIncrementColumns(t *testing.T) {
 	if columns[1].Extra != "" {
 		t.Fatalf("non-identity column should not be marked: %+v", columns[1])
 	}
+	if columns[0].Comment != "订单主键" || columns[1].Comment != "客户名称" {
+		t.Fatalf("native column comments should fill empty compatibility-view values: %+v", columns)
+	}
 
 	queries := damengColumnsMetadataQueries()
-	if len(queries) != 2 || !strings.Contains(queries[1], "SYS.SYSCOLUMNS") {
-		t.Fatalf("expected base and system metadata queries, got=%v", queries)
+	if len(queries) != 3 || !strings.Contains(queries[1], "SYS.SYSCOLUMNCOMMENTS") || !strings.Contains(queries[2], "SYS.SYSCOLUMNS") {
+		t.Fatalf("expected base, native comment, and system column metadata queries, got=%v", queries)
 	}
 }
 
 func TestDamengGetColumnsKeepsBaseMetadataWhenAutoIncrementQueryFails(t *testing.T) {
-	resetDamengColumnsMetadataQueryState(t, true)
+	resetDamengColumnsMetadataQueryState(t, true, false)
 
 	damengDB := &DamengDB{conn: openDamengColumnsMetadataDB(t)}
 	columns, err := damengDB.GetColumns("biz", "orders")
@@ -190,8 +210,21 @@ func TestDamengGetColumnsKeepsBaseMetadataWhenAutoIncrementQueryFails(t *testing
 	}
 }
 
+func TestDamengGetColumnsKeepsBaseMetadataWhenNativeCommentQueryFails(t *testing.T) {
+	resetDamengColumnsMetadataQueryState(t, false, true)
+
+	damengDB := &DamengDB{conn: openDamengColumnsMetadataDB(t)}
+	columns, err := damengDB.GetColumns("biz", "orders")
+	if err != nil {
+		t.Fatalf("GetColumns should keep base metadata when native comments are unavailable: %v", err)
+	}
+	if len(columns) != 2 || columns[0].Name != "ID" || columns[0].Extra != "auto_increment" {
+		t.Fatalf("unexpected fallback columns: %+v", columns)
+	}
+}
+
 func TestDamengGetCreateStatementAppendsTableComment(t *testing.T) {
-	resetDamengColumnsMetadataQueryState(t, false)
+	resetDamengColumnsMetadataQueryState(t, false, false)
 
 	damengDB := &DamengDB{conn: openDamengColumnsMetadataDB(t)}
 	ddl, err := damengDB.GetCreateStatement("biz", "orders")
@@ -218,7 +251,7 @@ func TestDamengGetCreateStatementAppendsTableComment(t *testing.T) {
 }
 
 func TestDamengGetIndexesUsesIndexOwnerJoinAndMapsColumnOrder(t *testing.T) {
-	resetDamengColumnsMetadataQueryState(t, false)
+	resetDamengColumnsMetadataQueryState(t, false, false)
 
 	damengDB := &DamengDB{conn: openDamengColumnsMetadataDB(t)}
 	indexes, err := damengDB.GetIndexes("biz", "orders")

internal/db/dameng_impl.go

@@ -331,6 +331,14 @@ func (d *DamengDB) GetColumns(dbName, tableName string) ([]connection.ColumnDefi
 	if len(columns) == 0 {
 		return columns, nil
 	}
+	if !hasDamengColumnComments(columns) {
+		commentData, _, commentErr := d.Query(buildDamengColumnCommentsQuery(dbName, tableName))
+		if commentErr != nil {
+			logger.Warnf("达梦 GetColumns 原生字段注释查询失败，已返回基础字段定义：%v", commentErr)
+		} else {
+			columns = applyDamengColumnComments(columns, commentData)
+		}
+	}
 
 	autoIncrementData, _, autoIncrementErr := d.Query(buildDamengAutoIncrementColumnsQuery(dbName, tableName))
 	if autoIncrementErr != nil {

internal/db/dameng_metadata.go

@@ -148,6 +148,25 @@ func buildDamengColumnsQuery(dbName, tableName string) string {
 		ORDER BY c.column_id`, upperDBName, upperTableName, upperDBName, upperTableName, upperDBName, upperTableName)
 }
 
+// buildDamengColumnCommentsQuery uses Dameng's native comment dictionary as a
+// fallback. Some DM8 deployments expose column metadata through the Oracle-
+// compatible ALL_COL_COMMENTS/USER_COL_COMMENTS views but return empty comment
+// values when those views are joined with the column dictionary.
+func buildDamengColumnCommentsQuery(dbName, tableName string) string {
+	upperTableName := strings.ReplaceAll(strings.ToUpper(strings.TrimSpace(tableName)), "'", "''")
+	upperDBName := strings.ReplaceAll(strings.ToUpper(strings.TrimSpace(dbName)), "'", "''")
+
+	schemaPredicate := "SCHNAME = USER"
+	if upperDBName != "" {
+		schemaPredicate = fmt.Sprintf("SCHNAME = '%s'", upperDBName)
+	}
+
+	return fmt.Sprintf(`SELECT COLNAME AS column_name, COMMENT$ AS col_comment
+		FROM SYS.SYSCOLUMNCOMMENTS
+		WHERE %s AND TVNAME = '%s' AND COMMENT$ IS NOT NULL
+		ORDER BY COLNAME`, schemaPredicate, upperTableName)
+}
+
 func buildDamengTableCommentQuery(dbName, tableName string) string {
 	upperTableName := strings.ReplaceAll(strings.ToUpper(strings.TrimSpace(tableName)), "'", "''")
 	upperDBName := strings.ReplaceAll(strings.ToUpper(strings.TrimSpace(dbName)), "'", "''")
@@ -393,3 +412,30 @@ func buildDamengColumnDefinitions(data []map[string]interface{}) []connection.Co
 
 	return columns
 }
+
+func hasDamengColumnComments(columns []connection.ColumnDefinition) bool {
+	for _, column := range columns {
+		if strings.TrimSpace(column.Comment) != "" {
+			return true
+		}
+	}
+	return false
+}
+
+func applyDamengColumnComments(columns []connection.ColumnDefinition, data []map[string]interface{}) []connection.ColumnDefinition {
+	commentsByColumn := make(map[string]string, len(data))
+	for _, row := range data {
+		columnName := strings.ToUpper(strings.TrimSpace(getDamengRowString(row, "COLUMN_NAME", "COLNAME")))
+		if columnName == "" {
+			continue
+		}
+		commentsByColumn[columnName] = getDamengRowString(row, "COL_COMMENT", "COMMENT$", "COMMENT", "COMMENTS")
+	}
+
+	for i := range columns {
+		if comment, ok := commentsByColumn[strings.ToUpper(strings.TrimSpace(columns[i].Name))]; ok {
+			columns[i].Comment = comment
+		}
+	}
+	return columns
+}

internal/db/dameng_metadata_test.go

@@ -146,6 +146,28 @@ func TestBuildDamengColumnsQuery_IncludesColumnCommentsJoin(t *testing.T) {
 	}
 }
 
+func TestBuildDamengColumnCommentsQueryUsesNativeDictionary(t *testing.T) {
+	t.Parallel()
+
+	userQuery := buildDamengColumnCommentsQuery("", "orders")
+	for _, want := range []string{
+		"FROM SYS.SYSCOLUMNCOMMENTS",
+		"SCHNAME = USER",
+		"TVNAME = 'ORDERS'",
+		"COLNAME AS column_name",
+		"COMMENT$ AS col_comment",
+	} {
+		if !strings.Contains(userQuery, want) {
+			t.Fatalf("current-schema native comment query should contain %q, got: %s", want, userQuery)
+		}
+	}
+
+	ownerQuery := buildDamengColumnCommentsQuery("biz", "orders")
+	if !strings.Contains(ownerQuery, "SCHNAME = 'BIZ'") || !strings.Contains(ownerQuery, "TVNAME = 'ORDERS'") {
+		t.Fatalf("schema native comment query should target the selected table, got: %s", ownerQuery)
+	}
+}
+
 func TestBuildDamengTableCommentQueryUsesSchemaAppropriateDictionaryView(t *testing.T) {
 	t.Parallel()
 
@@ -182,11 +204,11 @@ func TestBuildDamengColumnDefinitions_MapsComment(t *testing.T) {
 
 	columns := buildDamengColumnDefinitions([]map[string]interface{}{
 		{
-			"COLUMN_NAME":  "ID",
-			"DATA_TYPE":    "NUMBER",
-			"NULLABLE":     "N",
-			"COLUMN_KEY":   "PRI",
-			"COL_COMMENT":  "主键",
+			"COLUMN_NAME": "ID",
+			"DATA_TYPE":   "NUMBER",
+			"NULLABLE":    "N",
+			"COLUMN_KEY":  "PRI",
+			"COL_COMMENT": "主键",
 		},
 	})