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Todd Lipcon commented on KUDU-2381: ----------------------------------- Looking again at a similar workload and still see behavior like this. An easy fix is likely to have a new bool like 'DeltaPreparer::_may_have_deltas' which can be set to true in all of the spots where deleted_, reinserted_, and updates_by_col_ are modified. We can use that to implement MayHaveDeltas easily and to short-circuit the clearing of updates_by_col_ for the common case of no deltas. > Optimize DeltaMemStore for case of no matching deltas > ----------------------------------------------------- > > Key: KUDU-2381 > URL: https://issues.apache.org/jira/browse/KUDU-2381 > Project: Kudu > Issue Type: Improvement > Components: perf, tablet > Reporter: Todd Lipcon > Assignee: Todd Lipcon > Priority: Major > > Currently in a scan workload which scans 280 columns I see DeltaMemStore > iteration taking up a significant amount of CPU in the scan, despite the fact > that the dataset has no updates. Of 1.6sec in > MaterializingIterator::NextBlock, we spent 0.61s in DMSIterator::PrepareBatch > and 0.14s in DMSIterator::MayHaveDeltas. So, about 46% of our time here is on > wasted work. -- This message was sent by Atlassian JIRA (v7.6.3#76005)