code: func MockInfoSchema(tbList []*model.TableInfo) InfoSchema {
  	result := &infoSchema{}
  	result.schemaMap = make(map[string]*schemaTables)
  	result.sortedTablesBuckets = make([]sortedTables, bucketCount)
  	dbInfo := &model.DBInfo{ID: 0, Name: model.NewCIStr("test"), Tables: tbList}
  	tableNames := &schemaTables{
  		dbInfo: dbInfo,
  		tables: make(map[string]table.Table),
  	}
  	result.schemaMap["test"] = tableNames
  	for _, tb := range tbList {
  		tbl := table.MockTableFromMeta(tb)
  		tableNames.tables[tb.Name.L] = tbl
  		bucketIdx := tableBucketIdx(tb.ID)
  		result.sortedTablesBuckets[bucketIdx] = append(result.sortedTablesBuckets[bucketIdx], tbl)
  	}
  	for i := range result.sortedTablesBuckets {
  		sort.Sort(result.sortedTablesBuckets[i])
  	}
  	return result
  }
docs: // MockInfoSchema only serves for test.