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ec3
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Posts: 2
Registered: ‎08-17-2017

RowMaterializationTimer and TotalTime in query profile

In the query profile, under the ImpalaServer section, there are ClientFetchWaitTimer, InactiveTotalTIme, RowMaterializationTimer, and TotalTime. Below is an example from the query profile of a query I ran:

 

ImpalaServer
- ClientFetchWaitTimer: 3,884,245,220
- InactiveTotalTime: 0
- RowMaterializationTimer: 59,959,236,928
- TotalTime: 0

 

What exactly does RowMaterializationTimer measure? There are no comments for this counter in the code. I traced the code to client-request-state.cc and saw that in FetchRowsInternal() there's the line: SCOPED_TIMER(row_materialization_timer_);

and then nothing else. It seems like row_materialization_timer_ is updated via PeriodicCounterUpdater. But I don't understand how taking samples periodically would contribute to a single value shown in "RowMaterializationTimer". Any insights would be appreciated.

 

Also, is it possible that TotatlTime is 0 whenClientFetchWaitTimer and RowMaterializationTimer are > 0? Isn't that the total elapsed time from ImpalaServer?

 

Thanks,

 

Eric

 

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