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Real memory usage doesn't match resource groups; how can we improve estimation of query needs?

We frequently encounter situations where our resource groups have been fully allocated during peak periods but our real memory utilization in Linux and the first tab of management console is only about 50%. How can we improve Vertica's estimation of how much memory each query will need?

Question from Optimizing Query Performance and Resource Pool Tuning @rbankula @bat

Answers

  • Keep in mind that Vertica allocates memory to a query based on the query budget you set, not always the actual memory used (though in some cases Vertica will allocate less than the budget). Query Budget is typically MaxMemorySize (or MemorySize if that value is set) divided by PlannedConcurrency. Each session coming into that pool is allocated that amount. If you adjust those values and set a lower query budget per session, you will see the allocation in the pool go down.

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