add table & column comment for postgres（add table comment for mysql） (#2067)

让 postgres 支持字段注释，只在 v1.2.5 上测试过（不知道怎么 import master）

发现 master 分支好像大改了？模式表名带 schema 了

使用方式和 mysql 相同
```go
	type User struct {
		Id int64	`xorm:"pk autoincr"`
		Name string `json:"name" xorm:"not null default '' varchar(50) index(name_age) comment('用户 (it''s) 1; 名')"`
		Salt string
		Age int		`json:"age" xorm:"not null default 0 int(10) index(name_age) comment('年龄')"`
		Passwd string `xorm:"varchar(200)"`
		CreatedAt time.Time `xorm:"created"`
		UpdatedAt time.Time `xorm:"updated"`
	}

	_ = engine.Sync(new(User))

    func (model User) TableComment() string {
    	return "表注释"
    }
```

Co-authored-by: fanybook <fanybook@gmail.com>
Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>
Reviewed-on: https://gitea.com/xorm/xorm/pulls/2067
Co-authored-by: fanybook <fanybook@noreply.gitea.io>
Co-committed-by: fanybook <fanybook@noreply.gitea.io>

dialects/dialect.go

@@ -206,7 +206,7 @@ func (db *Base) IsColumnExist(queryer core.Queryer, ctx context.Context, tableNa
 // AddColumnSQL returns a SQL to add a column
 func (db *Base) AddColumnSQL(tableName string, col *schemas.Column) string {
 	s, _ := ColumnString(db.dialect, col, true)
-	return fmt.Sprintf("ALTER TABLE %v ADD %v", db.dialect.Quoter().Quote(tableName), s)
+	return fmt.Sprintf("ALTER TABLE %s ADD %s", db.dialect.Quoter().Quote(tableName), s)
 }
 
 // CreateIndexSQL returns a SQL to create index

dialects/mysql.go

@@ -685,6 +685,12 @@ func (db *mysql) CreateTableSQL(ctx context.Context, queryer core.Queryer, table
 		b.WriteString(db.rowFormat)
 	}
 
+	if table.Comment != "" {
+		b.WriteString(" COMMENT='")
+		b.WriteString(table.Comment)
+		b.WriteString("'")
+	}
+
 	return b.String(), true, nil
 }
 

dialects/postgres.go

@@ -991,13 +991,37 @@ func (db *postgres) IsTableExist(queryer core.Queryer, ctx context.Context, tabl
 		db.getSchema(), tableName)
 }
 
-func (db *postgres) ModifyColumnSQL(tableName string, col *schemas.Column) string {
+func (db *postgres) AddColumnSQL(tableName string, col *schemas.Column) string {
+	s, _ := ColumnString(db.dialect, col, true)
+
+	quoter := db.dialect.Quoter()
+	addColumnSQL := ""
+	commentSQL := "; "
 	if len(db.getSchema()) == 0 || strings.Contains(tableName, ".") {
-		return fmt.Sprintf("alter table %s ALTER COLUMN %s TYPE %s",
+		addColumnSQL = fmt.Sprintf("ALTER TABLE %s ADD %s", quoter.Quote(tableName), s)
-			db.quoter.Quote(tableName), db.quoter.Quote(col.Name), db.SQLType(col))
+		commentSQL += fmt.Sprintf("COMMENT ON COLUMN %s.%s IS '%s'", quoter.Quote(tableName), quoter.Quote(col.Name), col.Comment)
+		return addColumnSQL + commentSQL
 	}
-	return fmt.Sprintf("alter table %s.%s ALTER COLUMN %s TYPE %s",
+
-		db.quoter.Quote(db.getSchema()), db.quoter.Quote(tableName), db.quoter.Quote(col.Name), db.SQLType(col))
+	addColumnSQL = fmt.Sprintf("ALTER TABLE %s.%s ADD %s", quoter.Quote(db.getSchema()), quoter.Quote(tableName), s)
+	commentSQL += fmt.Sprintf("COMMENT ON COLUMN %s.%s.%s IS '%s'", quoter.Quote(db.getSchema()), quoter.Quote(tableName), quoter.Quote(col.Name), col.Comment)
+	return addColumnSQL + commentSQL
+}
+
+func (db *postgres) ModifyColumnSQL(tableName string, col *schemas.Column) string {
+	quoter := db.dialect.Quoter()
+	modifyColumnSQL := ""
+	commentSQL := "; "
+
+	if len(db.getSchema()) == 0 || strings.Contains(tableName, ".") {
+		modifyColumnSQL = fmt.Sprintf("ALTER TABLE %s ALTER COLUMN %s TYPE %s", quoter.Quote(tableName), quoter.Quote(col.Name), db.SQLType(col))
+		commentSQL += fmt.Sprintf("COMMENT ON COLUMN %s.%s IS '%s'", quoter.Quote(tableName), quoter.Quote(col.Name), col.Comment)
+		return modifyColumnSQL + commentSQL
+	}
+
+	modifyColumnSQL = fmt.Sprintf("ALTER TABLE %s.%s ALTER COLUMN %s TYPE %s", quoter.Quote(db.getSchema()), quoter.Quote(tableName), quoter.Quote(col.Name), db.SQLType(col))
+	commentSQL += fmt.Sprintf("COMMENT ON COLUMN %s.%s.%s IS '%s'", quoter.Quote(db.getSchema()), quoter.Quote(tableName), quoter.Quote(col.Name), col.Comment)
+	return modifyColumnSQL + commentSQL
 }
 
 func (db *postgres) DropIndexSQL(tableName string, index *schemas.Index) string {
@@ -1302,6 +1326,26 @@ func (db *postgres) GetIndexes(queryer core.Queryer, ctx context.Context, tableN
 	return indexes, nil
 }
 
+func (db *postgres) CreateTableSQL(ctx context.Context, queryer core.Queryer, table *schemas.Table, tableName string) (string, bool, error) {
+	quoter := db.dialect.Quoter()
+	if len(db.getSchema()) != 0 && !strings.Contains(tableName, ".") {
+		tableName = fmt.Sprintf("%s.%s", db.getSchema(), tableName)
+	}
+
+	createTableSQL, ok, err := db.Base.CreateTableSQL(ctx, queryer, table, tableName)
+	if err != nil {
+		return "", ok, err
+	}
+
+	commentSql := "; "
+	if table.Comment != "" {
+		// support schema.table -> "schema"."table"
+		commentSql += fmt.Sprintf("COMMENT ON TABLE %s IS '%s'", quoter.Quote(tableName), table.Comment)
+	}
+
+	return createTableSQL + commentSql, true, nil
+}
+
 func (db *postgres) Filters() []Filter {
 	return []Filter{&SeqFilter{Prefix: "$", Start: 1}}
 }

names/table_name.go

@@ -14,9 +14,15 @@ type TableName interface {
 	TableName() string
 }
 
+type TableComment interface {
+	TableComment() string
+}
+
 var (
 	tpTableName    = reflect.TypeOf((*TableName)(nil)).Elem()
+	tpTableComment = reflect.TypeOf((*TableComment)(nil)).Elem()
 	tvCache        sync.Map
+	tcCache        sync.Map
 )
 
 // GetTableName returns table name
@@ -55,3 +61,40 @@ func GetTableName(mapper Mapper, v reflect.Value) string {
 
 	return mapper.Obj2Table(v.Type().Name())
 }
+
+// GetTableComment returns table comment
+func GetTableComment(v reflect.Value) string {
+	if v.Type().Implements(tpTableComment) {
+		return v.Interface().(TableComment).TableComment()
+	}
+
+	if v.Kind() == reflect.Ptr {
+		v = v.Elem()
+		if v.Type().Implements(tpTableComment) {
+			return v.Interface().(TableComment).TableComment()
+		}
+	} else if v.CanAddr() {
+		v1 := v.Addr()
+		if v1.Type().Implements(tpTableComment) {
+			return v1.Interface().(TableComment).TableComment()
+		}
+	} else {
+		comment, ok := tcCache.Load(v.Type())
+		if ok {
+			if comment.(string) != "" {
+				return comment.(string)
+			}
+		} else {
+			v2 := reflect.New(v.Type())
+			if v2.Type().Implements(tpTableComment) {
+				tableComment := v2.Interface().(TableComment).TableComment()
+				tcCache.Store(v.Type(), tableComment)
+				return tableComment
+			}
+
+			tcCache.Store(v.Type(), "")
+		}
+	}
+
+	return ""
+}

session_schema.go

@@ -394,6 +394,8 @@ func (session *Session) Sync(beans ...interface{}) error {
 						_, err = session.exec(engine.dialect.ModifyColumnSQL(tbNameWithSchema, col))
 					}
 				}
+			} else if col.Comment != oriCol.Comment {
+				_, err = session.exec(engine.dialect.ModifyColumnSQL(tbNameWithSchema, col))
 			}
 
 			if col.Default != oriCol.Default {

tags/parser.go

@@ -316,6 +316,7 @@ func (parser *Parser) Parse(v reflect.Value) (*schemas.Table, error) {
 	table := schemas.NewEmptyTable()
 	table.Type = t
 	table.Name = names.GetTableName(parser.tableMapper, v)
+	table.Comment = names.GetTableComment(v)
 
 	for i := 0; i < t.NumField(); i++ {
 		col, err := parser.parseField(table, i, t.Field(i), v.Field(i))

tags/parser_test.go

@@ -26,6 +26,20 @@ func (p ParseTableName2) TableName() string {
 	return "p_parseTableName"
 }
 
+type ParseTableComment struct{}
+
+type ParseTableComment1 struct{}
+
+type ParseTableComment2 struct{}
+
+func (p ParseTableComment1) TableComment() string {
+	return "p_parseTableComment1"
+}
+
+func (p *ParseTableComment2) TableComment() string {
+	return "p_parseTableComment2"
+}
+
 func TestParseTableName(t *testing.T) {
 	parser := NewParser(
 		"xorm",
@@ -47,6 +61,36 @@ func TestParseTableName(t *testing.T) {
 	assert.EqualValues(t, "p_parseTableName", table.Name)
 }
 
+func TestParseTableComment(t *testing.T) {
+	parser := NewParser(
+		"xorm",
+		dialects.QueryDialect("mysql"),
+		names.SnakeMapper{},
+		names.SnakeMapper{},
+		caches.NewManager(),
+	)
+
+	table, err := parser.Parse(reflect.ValueOf(new(ParseTableComment)))
+	assert.NoError(t, err)
+	assert.EqualValues(t, "", table.Comment)
+
+	table, err = parser.Parse(reflect.ValueOf(new(ParseTableComment1)))
+	assert.NoError(t, err)
+	assert.EqualValues(t, "p_parseTableComment1", table.Comment)
+
+	table, err = parser.Parse(reflect.ValueOf(ParseTableComment1{}))
+	assert.NoError(t, err)
+	assert.EqualValues(t, "p_parseTableComment1", table.Comment)
+
+	table, err = parser.Parse(reflect.ValueOf(new(ParseTableComment2)))
+	assert.NoError(t, err)
+	assert.EqualValues(t, "p_parseTableComment2", table.Comment)
+
+	table, err = parser.Parse(reflect.ValueOf(ParseTableComment2{}))
+	assert.NoError(t, err)
+	assert.EqualValues(t, "p_parseTableComment2", table.Comment)
+}
+
 func TestUnexportField(t *testing.T) {
 	parser := NewParser(
 		"xorm",