Todd Lipcon created KUDU-2866:
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Summary: CFileSet::Iterator::FinishBatch takes a lot of CPU for
selective wide table scans
Key: KUDU-2866
URL: https://issues.apache.org/jira/browse/KUDU-2866
Project: Kudu
Issue Type: Improvement
Components: perf, tablet
Reporter: Todd Lipcon
Assignee: Todd Lipcon
Scanning a wide table with a predicate that doesn't ever match showed ~10% CPU
usage in CFileSet::Iterator::FinishBatch. Looking at the assembly it seems that
the cost was in iterating over the vector<bool> indicating which columns had
been prepared. In the case of a selective predicate, only one of the 200+
columns was prepared, and the iteration was quite slow. Instead of using the
bitmap, we can instead just keep a list of the prepared column iterators.
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