Comparing Actual to Estimated Cost

Teradata Visual Explain User Guide

brand
Teradata Tools and Utilities
prodname
Visual Explain
vrm_release
16.10
16.20
category
User Guide
featnum
B035-2504-086K
When comparing actual to estimated cost, use Teradata Visual Explain to load the actual cost information from the DBQL for the most recently logged execution of the query.
This feature is available only for plans captured using QCD.

Load an execution plan before viewing cost. For more information, see Loading and Viewing an Execution Plan.

  1. Click .

    The Actual Versus Estimated Cost window opens.

    Actual Versus Estimated Cost for Query ID

    Column Name Description
    Step Step number in the query plan
    CPU Time CPU the step uses
    IO Count I/O the step uses
    StepStart Time Timestamp, to the nearest microsecond, when the step was sent to the AMP
    StepStop Time Timestamp, to the nearest microsecond, when the step returned from the AMP
    Elapsed Time Difference between StepStop Time and StepStart Time
    CPU Cost Estimated CPU time required to execute the step
    IO Cost Estimated I/O time required to execute the step
    Network Cost Estimated network time required to execute the step
    Total Cost Total estimated time required to execute the step
    If the query is not present in the DBQL, only the estimated cost appears. If the query is found, the actual and estimated stepwise costs appear.
  2. [Optional] In the Actual vs. Estimated Cost window, double-click the column headings to change the sort order.

    For example, double-click the CPU Cost column heading to list the steps with the highest cost estimates first.

  3. To view the graphical layout of the stepwise costs, click View Graph.
    Stepwise Cost Distribution Graph for Query ID