When analyzing options for query tuning, the first step is to analyze the query plan, as described in Reading Query Plans. The query plan explains how Vertica plans to process the query. The query plan describes the plan that the Optimizer calculates as the least-cost plan based on what projections the query accesses and on the table statistics. But the query plan does not provide any information about how the query actually executes.
Read more here:
https://my.vertica.com/kb/System-Tables ... rmance.htm