Comments

• Rahul_Choudhary

  January 2014

  Hi Thomas
  
  When you run a query that references more than one table, HP Vertica may need to do one or both of the following operations to join the tables together:
  1) Sort the data
  2) Resegment the data
  
  Local resegment groups are formed by resegmenting the data during the query execution with a node so that more parallelism can be exploited by each core can work on each of the small segment of the data. 
  
  I hope this answers your question.
  
  Regards
  Rahul

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• Vijaya_Bhaskar_

  April 2014

  Rahul, 
  
    Could you please explain for "LOCAL RESEGMENT GROUPS" and reason for joins in Plan with SQL involves one Table .
  
  EXPLAIN SELECT COUNT(distinct customer_key) AS cntd_cust     store_key,

          COUNT(DISTINCT product_key) AS cntd_prod,          COUNT(DISTINCT promotion_key) AS cntd_promo,          SUM(sales_dollar_amount) AS sum_sales_dollar,          SUM(cost_dollar_amount) AS sum_cost_dollar   FROM store.store_sales_fact   GROUP BY store_key   ORDER BY cntd_cust DESC   LIMIT 25;

  https://my.vertica.com/docs/7.0.x/HTML/index.htm#Authoring/AdministratorsGuide/EXPLAIN/PartiallySort...
  
  
  
  
  

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