[jira] [Created] (IMPALA-9339) Revise explanation of RowMaterializationTimer

["Sahil Takiar (Jira)" <ji...@apache.org>]

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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