Please take this survey to help us learn more about how you use third party tools. Your input is greatly appreciated!

What does LOCAL RESEGMENT GROUPS mean?

When we do EXPLAIN <query>, sometimes it shows LOCAL RESEGMENT GROUPS.  I'm just wondering what it means.  Thanks.

Comments

  • 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
  • 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...




Leave a Comment

BoldItalicStrikethroughOrdered listUnordered list
Emoji
Image
Align leftAlign centerAlign rightToggle HTML viewToggle full pageToggle lights
Drop image/file

Can't find what you're looking for? Search the Vertica Documentation, Knowledge Base, or Blog for more information.