🐛 fix(db): 修复达梦DDL缺失字段注释 Fixes #615

- 补齐达梦列元数据查询中的字段注释读取
- 保留原始 CREATE TABLE 结果并追加 COMMENT ON COLUMN 语句
- 修正达梦列定义映射时 COMMENT 丢失的问题
- 新增达梦 DDL 注释补全回归测试

internal/app/methods_db.go

@@ -1766,6 +1766,9 @@ func resolveCreateStatementWithFallbackWithText(dbInst db.Database, config conne
 	sqlStr, sourceErr := dbInst.GetCreateStatement(metadataSchemaName, metadataTableName)
 	if sourceErr == nil && !shouldFallbackCreateStatement(dbType, sqlStr) {
 		if strings.TrimSpace(sqlStr) != "" {
+			if columns, err := loadCreateStatementCommentColumns(dbInst, dbType, metadataSchemaName, metadataTableName); err == nil {
+				sqlStr = appendCreateStatementColumnComments(dbType, ddlSchemaName, ddlTableName, sqlStr, columns)
+			}
 			return sqlStr, nil
 		}
 		if isOceanBaseOracleProtocol(config) {
@@ -1916,6 +1919,51 @@ func buildFallbackCreateStatement(dbType string, schemaName string, tableName st
 	return buildFallbackCreateStatementWithText(dbType, schemaName, tableName, columns, nil, defaultDBBackendText)
 }
 
+func loadCreateStatementCommentColumns(dbInst db.Database, dbType string, schemaName string, tableName string) ([]connection.ColumnDefinition, error) {
+	if !shouldAppendColumnCommentsToCreateStatement(dbType) {
+		return nil, nil
+	}
+	return dbInst.GetColumns(schemaName, tableName)
+}
+
+func shouldAppendColumnCommentsToCreateStatement(dbType string) bool {
+	switch dbType {
+	case "dameng":
+		return true
+	default:
+		return false
+	}
+}
+
+func appendCreateStatementColumnComments(dbType string, schemaName string, tableName string, ddl string, columns []connection.ColumnDefinition) string {
+	if !shouldAppendColumnCommentsToCreateStatement(dbType) || strings.TrimSpace(ddl) == "" || len(columns) == 0 {
+		return ddl
+	}
+
+	qualifiedTable := quoteTableIdentByType(dbType, schemaName, tableName)
+	existingDDLUpper := strings.ToUpper(ddl)
+	commentStatements := make([]string, 0, len(columns))
+	for _, col := range columns {
+		commentSQL := buildFallbackColumnCommentStatement(dbType, schemaName, tableName, qualifiedTable, col.Name, col.Comment)
+		if commentSQL == "" {
+			continue
+		}
+		if strings.Contains(existingDDLUpper, strings.ToUpper(commentSQL)) {
+			continue
+		}
+		commentStatements = append(commentStatements, commentSQL)
+	}
+	if len(commentStatements) == 0 {
+		return ddl
+	}
+
+	trimmedDDL := strings.TrimRight(ddl, " \t\r\n")
+	if !strings.HasSuffix(trimmedDDL, ";") {
+		trimmedDDL += ";"
+	}
+	return trimmedDDL + "\n" + strings.Join(commentStatements, "\n")
+}
+
 func buildFallbackCreateStatementWithText(dbType string, schemaName string, tableName string, columns []connection.ColumnDefinition, indexes []connection.IndexDefinition, text func(string, map[string]any) string) (string, error) {
 	if text == nil {
 		text = defaultDBBackendText

internal/app/methods_db_create_statement_test.go

@@ -286,6 +286,39 @@ func TestResolveCreateStatementWithFallback_KingbaseIncludesColumnComments(t *te
 	}
 }
 
+func TestResolveCreateStatementWithFallback_DamengAppendsColumnComments(t *testing.T) {
+	t.Parallel()
+
+	dbInst := &fakeCreateStatementDB{
+		createSQL: `CREATE TABLE "APP"."ORDERS" ("ID" NUMBER NOT NULL, "STATUS" VARCHAR2(32));`,
+		columns: []connection.ColumnDefinition{
+			{Name: "ID", Type: "NUMBER", Nullable: "NO", Key: "PRI", Comment: "主键"},
+			{Name: "STATUS", Type: "VARCHAR2(32)", Nullable: "YES", Comment: "状态"},
+		},
+	}
+
+	ddl, err := resolveCreateStatementWithFallback(dbInst, connection.ConnectionConfig{
+		Type: "dameng",
+	}, "APP", "ORDERS")
+	if err != nil {
+		t.Fatalf("resolveCreateStatementWithFallback() unexpected error: %v", err)
+	}
+	if !strings.Contains(ddl, dbInst.createSQL) {
+		t.Fatalf("expected original dameng create SQL to be preserved, got: %s", ddl)
+	}
+	for _, want := range []string{
+		`COMMENT ON COLUMN "APP"."ORDERS"."ID" IS '主键';`,
+		`COMMENT ON COLUMN "APP"."ORDERS"."STATUS" IS '状态';`,
+	} {
+		if !strings.Contains(ddl, want) {
+			t.Fatalf("expected dameng DDL to contain %q, got: %s", want, ddl)
+		}
+	}
+	if dbInst.columnsCalls != 1 {
+		t.Fatalf("expected dameng path to load column metadata once, got %d", dbInst.columnsCalls)
+	}
+}
+
 func TestResolveCreateStatementWithFallback_KingbaseIncludesSecondaryIndexes(t *testing.T) {
 	t.Parallel()
 

internal/db/dameng_metadata.go

@@ -110,9 +110,11 @@ func buildDamengColumnsQuery(dbName, tableName string) string {
 	upperDBName := strings.ToUpper(strings.TrimSpace(dbName))
 
 	if upperDBName == "" {
-		return fmt.Sprintf(`SELECT c.column_name, c.data_type, c.data_length, c.char_length, c.data_precision, c.data_scale, c.nullable, c.data_default,
+		return fmt.Sprintf(`SELECT c.column_name, c.data_type, c.data_length, c.char_length, c.data_precision, c.data_scale, c.nullable, c.data_default, cc.comments AS comment,
 		CASE WHEN pk.column_name IS NOT NULL THEN 'PRI' ELSE '' END AS column_key
 		FROM user_tab_columns c
+		LEFT JOIN user_col_comments cc
+		  ON cc.table_name = c.table_name AND cc.column_name = c.column_name
 		LEFT JOIN (
 			SELECT cols.table_name, cols.column_name
 			FROM user_constraints cons
@@ -125,9 +127,11 @@ func buildDamengColumnsQuery(dbName, tableName string) string {
 		ORDER BY c.column_id`, upperTableName, upperTableName, upperTableName)
 	}
 
-	return fmt.Sprintf(`SELECT c.column_name, c.data_type, c.data_length, c.char_length, c.data_precision, c.data_scale, c.nullable, c.data_default,
+	return fmt.Sprintf(`SELECT c.column_name, c.data_type, c.data_length, c.char_length, c.data_precision, c.data_scale, c.nullable, c.data_default, cc.comments AS comment,
 		CASE WHEN pk.column_name IS NOT NULL THEN 'PRI' ELSE '' END AS column_key
 		FROM all_tab_columns c
+		LEFT JOIN all_col_comments cc
+		  ON cc.owner = c.owner AND cc.table_name = c.table_name AND cc.column_name = c.column_name
 		LEFT JOIN (
 			SELECT cols.owner, cols.table_name, cols.column_name
 			FROM all_constraints cons
@@ -243,6 +247,7 @@ func buildDamengColumnDefinitions(data []map[string]interface{}) []connection.Co
 			Type:     formatDamengColumnType(row),
 			Nullable: normalizeDamengNullable(getDamengRowString(row, "NULLABLE")),
 			Key:      getDamengRowString(row, "COLUMN_KEY"),
+			Comment:  getDamengRowString(row, "COMMENT", "COMMENTS"),
 		}
 
 		defaultValue := getDamengRowString(row, "DATA_DEFAULT")

internal/db/dameng_metadata_test.go

@@ -3,6 +3,7 @@ package db
 import (
 	"errors"
 	"reflect"
+	"strings"
 	"testing"
 )
 
@@ -118,3 +119,44 @@ func TestCollectDamengDatabaseNames_FallbackToCurrentUser(t *testing.T) {
 		t.Fatalf("兜底查询应该返回当前用户, got=%v want=%v", got, want)
 	}
 }
+
+func TestBuildDamengColumnsQuery_IncludesColumnCommentsJoin(t *testing.T) {
+	t.Parallel()
+
+	userQuery := buildDamengColumnsQuery("", "orders")
+	if !strings.Contains(userQuery, "user_col_comments") {
+		t.Fatalf("expected user query to join user_col_comments, got: %s", userQuery)
+	}
+	if !strings.Contains(userQuery, "cc.comments AS comment") {
+		t.Fatalf("expected user query to select column comments, got: %s", userQuery)
+	}
+
+	allQuery := buildDamengColumnsQuery("app", "orders")
+	if !strings.Contains(allQuery, "all_col_comments") {
+		t.Fatalf("expected schema query to join all_col_comments, got: %s", allQuery)
+	}
+	if !strings.Contains(allQuery, "cc.comments AS comment") {
+		t.Fatalf("expected schema query to select column comments, got: %s", allQuery)
+	}
+}
+
+func TestBuildDamengColumnDefinitions_MapsComment(t *testing.T) {
+	t.Parallel()
+
+	columns := buildDamengColumnDefinitions([]map[string]interface{}{
+		{
+			"COLUMN_NAME": "ID",
+			"DATA_TYPE":   "NUMBER",
+			"NULLABLE":    "N",
+			"COLUMN_KEY":  "PRI",
+			"COMMENT":     "主键",
+		},
+	})
+
+	if len(columns) != 1 {
+		t.Fatalf("expected one column, got=%d", len(columns))
+	}
+	if columns[0].Comment != "主键" {
+		t.Fatalf("expected comment to be mapped, got=%q", columns[0].Comment)
+	}
+}