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Posted to dev@rocketmq.apache.org by GitBox <gi...@apache.org> on 2021/08/10 04:01:21 UTC

[GitHub] [rocketmq] xiaoyaofawai commented on issue #3240: Why is the reading time from consumerQueue O(1)

xiaoyaofawai commented on issue #3240:
URL: https://github.com/apache/rocketmq/issues/3240#issuecomment-895710016


   ConsumeQueue support read data by message index, as you see:
   ![image](https://user-images.githubusercontent.com/12688996/128805753-a9f1e64d-edc6-4120-96b1-c17984d901fc.png)
   ConsumeQueue read data relay on MappedFileQueue, data offset can be calculated by 'startIndex' . the index of MappedFile in MappedFileQueue and the offset of data in MappedFile can be calculated by data offset.The time complexity of these processes is O(1), so the time complexity of reading data by startIndex from ConsumeQueue is O(1)


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