[jira] [Created] (TEZ-2496) Consider scheduling tasks in ShuffleVertexManager based on the partition sizes from the source

["Rajesh Balamohan (JIRA)" <ji...@apache.org>]

Rajesh Balamohan created TEZ-2496:
-------------------------------------

             Summary: Consider scheduling tasks in ShuffleVertexManager based on the partition sizes from the source
                 Key: TEZ-2496
                 URL: https://issues.apache.org/jira/browse/TEZ-2496
             Project: Apache Tez
          Issue Type: Improvement
            Reporter: Rajesh Balamohan


Consider scheduling tasks in ShuffleVertexManager based on the partition sizes from the source.  This would be helpful in scenarios, where there is limited resources (or concurrent jobs running or multiple waves) with dataskew and the task which gets large amount of data gets sceheduled much later.

e.g Consider the following hive query running in a queue with limited capacity (42 slots in total) @ 200 GB scale

{noformat}
CREATE TEMPORARY TABLE sampleData AS
  SELECT CASE
           WHEN ss_sold_time_sk IS NULL THEN 70429
           ELSE ss_sold_time_sk
       END AS ss_sold_time_sk,
       ss_item_sk,
       ss_customer_sk,
       ss_cdemo_sk,
       ss_hdemo_sk,
       ss_addr_sk,
       ss_store_sk,
       ss_promo_sk,
       ss_ticket_number,
       ss_quantity,
       ss_wholesale_cost,
       ss_list_price,
       ss_sales_price,
       ss_ext_discount_amt,
       ss_ext_sales_price,
       ss_ext_wholesale_cost,
       ss_ext_list_price,
       ss_ext_tax,
       ss_coupon_amt,
       ss_net_paid,
       ss_net_paid_inc_tax,
       ss_net_profit,
       ss_sold_date_sk
  FROM store_sales distribute by ss_sold_time_sk;
{noformat}

This generated 39 maps and 134 reduce slots (3 reduce waves). When lots of nulls are there for ss_sold_time_sk, it would tend to have data skew towards 70429.  If the reducer which gets this data gets scheduled much earlier (i.e in first wave itself), entire job would finish fast.



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