refactor create table for postgres

dialects/postgres.go

@@ -966,38 +966,35 @@ func (db *postgres) AutoIncrStr() string {
 }
 
 func (db *postgres) CreateTableSQL(table *schemas.Table, tableName string) ([]string, bool) {
-	var sql string
-	sql = "CREATE TABLE IF NOT EXISTS "
 	if tableName == "" {
 		tableName = table.Name
 	}
 
 	quoter := db.Quoter()
-	sql += quoter.Quote(tableName)
-	sql += " ("
+	var b strings.Builder
+	b.WriteString("CREATE TABLE  IF NOT EXISTS ")
+	quoter.QuoteTo(&b, tableName)
+	b.WriteString(" (")
 
-	if len(table.ColumnsSeq()) > 0 {
-		pkList := table.PrimaryKeys
-
-		for _, colName := range table.ColumnsSeq() {
+	for i, colName := range table.ColumnsSeq() {
 		col := table.GetColumn(colName)
-			s, _ := ColumnString(db, col, col.IsPrimaryKey && len(pkList) == 1)
-			sql += s
-			sql = strings.TrimSpace(sql)
-			sql += ", "
+		s, _ := ColumnString(db, col, col.IsPrimaryKey && len(table.PrimaryKeys) == 1)
+		b.WriteString(s)
+
+		if len(table.PrimaryKeys) > 1 {
+			b.WriteString("PRIMARY KEY ( ")
+			b.WriteString(quoter.Join(table.PrimaryKeys, ","))
+			b.WriteString(" )")
 		}
 
-		if len(pkList) > 1 {
-			sql += "PRIMARY KEY ( "
-			sql += quoter.Join(pkList, ",")
-			sql += " ), "
+		if i != len(table.ColumnsSeq())-1 {
+			b.WriteString(", ")
+		}
 	}
 
-		sql = sql[:len(sql)-2]
-	}
-	sql += ")"
+	b.WriteString(")")
 
-	return []string{sql}, true
+	return []string{b.String()}, false
 }
 
 func (db *postgres) IndexCheckSQL(tableName, idxName string) (string, []interface{}) {