code: func (b *batchChecker) fillBackKeys(t table.Table, row toBeCheckedRow, handle int64) {
  	if row.rowValue != nil {
  		b.dupOldRowValues[string(t.RecordKey(handle))] = row.rowValue
  	}
  	if row.handleKey != nil {
  		b.dupKVs[string(row.handleKey.newKV.key)] = row.handleKey.newKV.value
  	}
  	for _, uk := range row.uniqueKeys {
  		b.dupKVs[string(uk.newKV.key)] = tables.EncodeHandle(handle)
  	}
  }
docs: // fillBackKeys fills the updated key-value pair to the dupKeyValues for further check.