Sahil Takiar created IMPALA-9339:
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Summary: Revise explanation of RowMaterializationTimer
Key: IMPALA-9339
URL: https://issues.apache.org/jira/browse/IMPALA-9339
Project: IMPALA
Issue Type: Bug
Reporter: Sahil Takiar
Assignee: Sahil Takiar
IMPALA-8825 added the following explanation of the counter
{{RowMaterializationTimer}}
{quote}
/// Tracks the time spent materializing rows and converting them into a
QueryResultSet.
/// The QueryResultSet format used depends on the client, for Beeswax clients
an ASCII
/// representation is used, whereas for HS2 clients (using TCLIService.thrift)
rows are
/// converted into a TRowSet. Materializing rows includes evaluating any yet
unevaluated
/// expressions using ScalarExprEvaluators.
{quote}
This isn't accurate because the actual timer measures time taken running
{{Coordinator::GetNext}} which can block if any downstream operators in the
plan take a long time to materialize rows.
We should revise the explanation of {{RowMaterializationTimer}} and consider
adding a separate timer that truly measures the amount of time taken to
materialize rows (e.g. measure time taken in {{QueryResultSet::AddRows}}).
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