[GitHub] [hbase] apurtell commented on pull request #3360: HBASE-25975 Row Commit Sequencer

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apurtell commented on pull request #3360:
URL: https://github.com/apache/hbase/pull/3360#issuecomment-855306586


   The main issue with https://github.com/apache/hbase/pull/3352 is serializing commits with the act of getting the time requires that everything that might mutate the resource you are trying to protect must be within that scope. For a single row update the scope would be a row, and highly granular, so performance will not be affected that much. For batch mutations, which are typical, the scope is the region, and serializing commits to a region is expensive. I struggled for a while with various forms of hierarchical clocks where one might get a clock for the region, then use that clock to get child clocks for a row, but then reconsidered... What is it we are really tracking? Why not track that explicitly? It seemed much simpler in retrospect. Hence this PR, to explore that idea instead. 


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